Suspension culture promotes serosal mesothelial development in human intestinal organoids

Pluripotent-stem-cell-derived human intestinal organoids (HIOs) model some aspects of intestinal development and disease, but current culture methods do not fully recapitulate the diverse cell types and complex organization of the human intestine and are reliant on 3D extracellular matrix or hydrogel systems, which limit experimental control and translational potential for regenerative medicine. We describe suspension culture as a simple, low-maintenance method for culturing HIOs and for promoting in vitro differentiation of an organized serosal mesothelial layer that is similar to primary human intestinal serosal mesothelium based on single-cell RNA sequencing and histological analysis. Functionally, HIO serosal mesothelium has the capacity to differentiate into smooth-muscle-like cells and exhibits fibrinolytic activity. An inhibitor screen identifies Hedgehog and WNT signaling as regulators of human serosal mesothelial differentiation. Collectively, suspension HIOs represent a three-dimensional model to study the human serosal mesothelium.

Development and ultrastructure of the thickened serosa and serosal cuticle formed beneath the embryo in the stonefly Scopura montana Maruyama, 1987 (Insecta, Plecoptera, Scopuridae)

We aimed to describe the development and ultrastructure of the thickened serosa and serosal cuticle formed beneath the embryo of Plecoptera, using Scopura montana of Scopuridae as a euholognathan representative. Using transmission electron microscopy, we found that the egg membranes were composed of a thick exochorion, a thicker endochorion consisting of two sublayers, and an extremely thin vitelline membrane. The egg membrane construction represents a groundplan feature of the euholognathan egg membranes. The serosa converges beneath the embryo to form a thickened serosa, comprising cells in a radial arrangement, in association with the formation of the amnioserosal fold. The thickened serosa then deposits the thickened serosal cuticle, consisting of four layers differing in fine structure and electron density. After achieving its secretory function, the thickened serosa then disintegrates, and the liberated serosal cells float for a short period in the peripheral region of the egg inside. Collectively, our findings should provide the basis for further characterization of the serosal structures concerned, but we were unable to corroborate previous studies assigning the thickened serosa and serosal cuticle in Plecoptera to the water absorption function.

Embryonic development of a collembolan, Tomocerus cuspidatus Börner, 1909: with special reference to the development and developmental potential of serosa (Hexapoda: Collembola, Tomoceridae)

The embryogenesis of a collembolan, Tomocerus cuspidatus, was examined and described, with special reference to the development of serosa and its developmental potential. As a result of cleavage, which starts with holoblastic cleavage and changes to the superficial type, the blastoderm forms. At the center of the dorsal side of the egg, the primary dorsal organ develops. The mesoderm is segregated beneath the entire blastoderm, excluding the primary dorsal organ. The mesoderm then migrates to the presumptive embryonic area, and the embryonic and extra-embryonic areas differentiate. The area lined with mesoderm is the embryo, and that devoid of it is the serosa. Owing to blastokinesis completion, the extra-embryonic area or the serosa is highly stretched, and the serosal cells are often found to undergo mitosis. The serosa possesses the ability to differentiate into the body wall. It was confirmed, in contrast to the previous understanding, that the serosal cells do not degenerate, but participate in the formation of the body wall or definitive dorsal closure. Integrating this newly obtained information and other embryological evidence, the basal splitting of Hexapoda was phylogenetically discussed and reconstructed, and a phylogeny formulated as "Ellipura (=Protura+Collembola)+Cercophora (=Diplura and Ectognatha)" was proposed.

Placenta-like structure of the aphid endoparasitic wasp Aphidius ervi: a strategy of optimal resources acquisition

Aphidius ervi (Hymenoptera: Braconidae) is an entomophagous parasitoid known to be an effective parasitoid of several aphid species of economic importance. A reduction of its production cost during mass rearing for inundative release is needed to improve its use in biological control of pests. In these contexts, a careful analysis of its entire development phases within its host is needed. This paper shows that this parasitoid has some characteristics in its embryological development rather complex and different from most other reported insects, which can be phylogenetically very close. First, its yolkless egg allows a high fecundity of the female but force them to hatch from the egg shell rapidly to the host hemocoel. An early cellularisation allowing a rapid differentiation of a serosa membrane seems to confirm this hypothesis. The serosa wraps the developing embryo until the first instar larva stage and invades the host tissues by microvilli projections and form a placenta like structure able to divert host resources and allowing nutrition and respiration of embryo. Such interspecific invasion, at the cellular level, recalls mammal's trophoblasts that anchors maternal uterine wall and underlines the high adaptation of A. ervi to develop in the host body.

Structure and function of the extraembryonic membrane persisting around the larvae of the parasitoid Toxoneuron nigriceps

The embryo of Toxoneuron nigriceps (Hymenoptera, Braconidae) is surrounded by an extraembryonic membrane, which, at hatching, releases teratocytes and gives rise to a cell layer embedding the body of the 1st instar larva. This cell layer was studied at different developmental times, from soon after hatching up to the first larval moult, in order to elucidate its ultrastructural, immunocytochemical and physiological function. The persisting "larval serosa" shows a striking structural and functional complexity: it is a multifunctional barrier with protective properties, limits the passage of macromolecules and it is actively involved in the enzymatic processing and uptake of nutrients. The reported results emphasizes the important role that the embryo-derived host regulation factors may have in parasitism success in Hymenoptera koinobionts.

Serosal membranes (pleura, pericardium, peritoneum). Normal structure, development and experimental pathology

This monograph offers a comprehensive review of the present knowledge of the structure of the serosal coverings of the pleural, pericardial, and peritoneal cavities in humans and laboratory animals. The authors provide data from their own research--with transmission and scanning electron microscopy--on the structure of the main components of the serosal membranes: mesothelial cells, underlying basal lamina, and submesothelial connective tissue layer. Two main types of mesothelial cells (flat and cubic) are distinguished and their distribution on the parietal serosal sheets and on the visceral coverings of various organs is described. The openings between mesothelial cells (stomata) and their relations with lymphatic lacunae are described thoroughly. Special reference is made to the serosal accumulations of lymphoid tissue (milky spots). The transcellular and intercellular transport to and from serosal cavities is studied by means of horseradish peroxidase tracing experiments. The prenatal and postnatal developmental studies are focused on human and rat pleura. The alterations of serosal membranes after experimental hemothorax, pneumonectomy, and peritonitis caused by Pseudomonas aeruginosa application suggest the existence of early, reversible, and late, definite periods.

Development of serous cutaneous glands in Scinax nasica (Anura, Hylidae): patterns of poison biosynthesis and maturation in comparison with larval glands in specimens of other families

We examined the development of serous (poison) cutaneous glands in larval and juvenile Scinax nasica (Hylidae) at the ultrastructural level. We describe the biosynthesis and maturation of the cutaneous poison in comparison with the corresponding processes in representatives of Discoglossidae, Leptodactylidae, Pelobatidae and Pipidae. Serous biosynthesis in S. nasica starts in discrete adenoblasts and continues in the syncytial secretory unit. Biosynthetic processes involve rough endoplasmic reticulum and the Golgi apparatus, that releases membrane-bounded material, varying from fine grained to flocculent. During the post-Golgian secretory phase, this material undergoes initial maturation, and two products are formed: dense granules and larger vesicles holding a thin substance that will later be structured into a three-dimensional, honeycomb-like net. Both the secretory granules and vesicles change into glomerular-like aggregates of bowed, rod-shaped subunits (modules). In adult frogs, formation of dense granules is bypassed. The modular granule substructure seems to be related to the merocrine release of small amounts of poison, involved in regulating skin homeostasis. Comparison with maturational changes in larval glands of species representing four anuran families discloses similar patterns in the Leptodactylidae, but production of opaque homogeneous granules occurs in the Discoglossidae, clear vesicles in the Pelobatidae and aggregates of dense bars in the Pipidae.

Serous and Mucous Cells of Human Submandibular Salivary Gland Stimulated In Vitro by Isoproterenol, Carbachol and Clozapine: An LM, TEM, and HRSEM Study

We have investigated by LM, TEM, and HRSEM the effects of D,L-isoproterenol (beta-adrenergic agent), carbachol (muscarinic agent) and clozapine on biopsy specimens of human submandibular gland stimulated in vitro in an inorganic oxygenated medium. Clozapine is a dibenzodiazepine derivative used in psychotic patients that provokes hypersalivation, a displeasing side effect that often causes discontinuance of therapy. Our findings demonstrate that clozapine acts on salivary mucous and seromucous (serous) cells of the gland as a muscarinic agonist. However, the induced secretory response seems to differ qualitatively and quantitatively from that resulting from carbachol. Thus, in agreement with published data resulting from therapeutic treatments and from experimental studies on rats, the mechanism of clozapine induced hypersialorrhea remains open to further investigation.

Yolk utilization in stick insects entails the release of vitellin polypeptides into the perivitelline fluid

This study investigates the developmental fate of vitellin (Vt) polypeptides generated by limited proteolysis in an insect embryo. To this end, a number of polyclonal (pAb) and monoclonal antibodies (mAb) were raised against the yolk sac and the perivitelline fluid of late embryos of the stick insect Carausius morosus. Two dimensional immuno gel electrophoresis and Western blotting demonstrate that polypeptides resulting from Vt processing are present both in the yolk sac and the perivitelline fluid. At the confocal microscope, different labelling patterns were detected in the ooplasm depending on the stage of development attained by the embryo. At early developmental stages, label is associated with large unsegmented portions of the fluid ooplasm. During embryonic development, the fluid ooplasm is gradually transformed into yolk granules by intervention of vitellophages. Prior to dorsal closure, the yolk sac is separated from the perivitelline fluid by interposition of serosa cells (the so called serosa membrane). Several mAbs raised against the perivitelline fluid react specifically with this membrane suggesting that the release of Vt polypeptides from the yolk sac occurs by intracellular transit through the serosa cells. By immunocytochemistry, gold label appears associated with the cell surface and a number of vacuoles of the serosa membrane. These data are interpreted as suggesting that Vt polypeptides resulting from limited proteolysis in stick insect embryos are not exhaustively degraded within the yolk sac, but are instead transferred transcytotically to the perivitelline fluid through the serosa membrane.

Tribolium embryogenesis: a SEM study of cell shapes and movements from blastoderm to serosal closure

Embryogenesis in the beetle Tribolium is of increasing interest to both molecular and evolutionary biology because it differs from the Drosophila paradigm by its type of segment specification (short- vs. long-germ) and by the extensive epithelial envelopes - amnion and serosa - that are typical of most insects but not of higher dipterans. Using scanning electron microscopy of DAPI staged embryos we document development in Tribolium castaneum from blastoderm to completion of the envelopes, recording many details not otherwise accessible; we also provide a time table of the respective stages at 30 degrees C. The nascent blastoderm cells remain basally confluent with the yolksac until after the 13th (=last synchronous) mitotic cycle. The cells in the prospective serosa - the first domain to segregate visibly from the uniform blastoderm - carry surface protrusions likely to contact the overlying vitelline envelope. The embryonic rudiment, the other (and larger) blastodermal domain, gives rise to amnion and germ anlage. In the latter, visible differentiation begins with a "primitive pit" reminiscent of the posterior midgut rudiment of Drosophila. The subsequent invagination of the mesoderm resembles Drosophila gastrulation, except in the head region where the median groove extends through the entire preoral region. The prospective amnion starts differing visibly from the germ anlage during early gastrulation. It then folds underneath the spreading serosa and, advancing with the latter, closes the amniotic cavity at the ventral face of the germband. The largest (=posterior) amniotic fold covers a crestlike protrusion of the yolksac. Together with marked changes in the shape and arrangement of the amnion cells, this protrusion may contribute to the fold's elevation and early progress.

The serous demilune of rat sublingual gland is an artificial structure produced by conventional fixation

The ultrastructure of the secretory end-piece of the rat sublingual gland was examined in samples prepared by rapid freezing and freeze-substitution method, and results were analyzed in combination with 3-D images reconstructed by computer graphics from light micrographs of serial sections. Fixation by rapid freezing followed by freeze-substitution preserved cellular ultrastructures, especially the membrane structure, in perfect condition, and demonstrated the terminal portion of the sublingual gland to be a compound branched tubulo-alveolar gland with serous cells distributed throughout the end-pieces. All the serous cells aligned with mucous cells to surround a common lumen, leaving no demilune structure. In contrast, samples fixed by the conventional immersion method showed distended mucous cells displacing the serous cells toward the basal portion of the acinus to form the demilune structure. The luminal space was also compressed and appeared disconnected from the serous cells. From these observations, the serous demilune that for more than 130 years has been believed to be an actual histological entity was proved to be an artificial structure produced through compression by the hydrated and expanded mucous cells during immersion fixation.

A scanning and transmission electron microscope study of the human minor salivary glands

All human minor salivary glands, apart from the posterior deep lingual (von Ebner's) glands which were serous, contained a minor population of seromucous cells that increased from palatine and posterior superficial lingual (Weber's) to labial, anterior lingual (Blandin and Nuhn's) and buccal glands, in that order. Unlike the predominant mucous cells, whose structure was uniform, serous and seromucous cells exhibited, in each gland, peculiar cytological and cytoarchitectural characters.

[Anatomy and histotopography of human pericardial lymphoid tissue]

Data concerning microscopic structure of the layers of human serous pericardium, localization of lymphoid structures as related to them and their interrelations with connective tissue elements and vessels are represented. Findings on the thickness of serous pericardium in different layers are also given.

Intercellular material in the basal and lateral folds of parotid serous cells in four species of bats

BACKGROUND

Basal folds are slender plications at the basal surface of acinar cells in the salivary glands of many mammalian species. These largely organelle-free folds increase the surface area of the basal plasmalemma manyfold and are unquestionably involved in the translocation of organic and inorganic molecules and water into the acinar cells.

METHODS

Specimens of salivary glands were obtained from over 230 species of live-trapped bats from major areas of the globe. Tissues for electron microscopy were fixed and processed by conventional means.

RESULTS

A number of the bat species examined had dense material in the intercellular spaces between basal and lateral folds of serous cells in the parotid gland. This intercellular material was particularly prominent in three species of New World bats, viz., Pteronotus parnellii, P quadridens, and Phyllostomus latifolius, and in one species of Old World bats, Chalinolobus argentatus. This dense material, which has a farinaceous texture, appears not to pass through tight junctions, so it is excluded from the lumina of intercellular canaliculi and acini. The dense material originates in the acinar cells--it is carried to the membranes of the folds via coated vesicles, which empty their dense content by exocytosis into the intercellular space. Similar dense material is present in the intercellular spaces of the basal labyrinth of striated ducts in the two species of Pteronotus. The manner in which this material accumulates in the striated duct is unclear.

CONCLUSIONS

Although the function of the intracellular dense material is undetermined, it appears to be placed strategically to influence molecular traffic into acinar cells or to modulate the paracellular pathway. From a comparative evolutionary perspective, we hypothesize that, in bats, the combination of basal folds and extracellular densities is associated with insectivory. Similar morphologies appear to be lacking in frugivorous or nectarivorous species.

Ultrastructure of the binary parotid glands in the free-tailed bat, Tadarida thersites. I. Principal parotid gland

BACKGROUND

Many species of bats have two sets of submandibular glands, principal and accessory. The accessory gland may resemble the principal one but more often shows wide morphological divergence. The free-tailed bat, Tadarida thersites, is very unusual in that it has two sets of parotid glands rather than binary submandibular glands. We studied the ultrastructure of the principal parotid gland to establish a baseline for comparison with the accessory parotid.

METHODS

Two specimens of adult free-tailed bats, one male and one female, were live-trapped in western Kenya. Parotid glands were fixed for electron microscopy using a protocol expressly designed for field fixation and then embedded by conventional means.

RESULTS

Histologically, the principal parotid is a typical serous gland. The secretory granules of the endpiece cells have an unusual substructure in that they contain variable numbers of lucent halos and one or several spherules. Intercalated duct cells contain a significant number of dense, serous-like granules. Striated ducts have the usual basal configuration of mitochondria and folded plasma membranes, but the supranuclear cytoplasm contains many small, dense granules, so that these ducts resemble the granular convoluted tubules found in the submandibular glands of many families of rodents. The apices of the duct cells have a peculiar contour--the luminal surfaces obliquely invaginate into the apical cytoplasm, so that in thin section the luminal membranes appear to be underlaid by a layer of vacuoles.

CONCLUSION

Although the principal parotid gland of the free-tailed bat shows some distinctive, species-specific ultrastructural features, it basically is similar to the parotid gland in two other molossid bats, Tadarida brasiliensis and Molossus molossus. The distinctive features in the principal parotid gland of T. thersites might relate to its feeding on hard-bodied insects and perhaps to the production of lysozyme.

Serous cutaneous glands in Phyllomedusa hypochondrialis (Anura, Hylidae): secretory patterns during ontogenesis

Three syncytial gland types (Ia, Ib, and II ) have been described in the skin of larval, juvenile and adult Phyllomedusa hypochondrialis, which share the ultrastructural traits common to the serous secretory units of anuran skin, although each manufactures a peculiar product. Type la secretion consists of dense granules provided with a peculiar substructure, type Ib of vesicles holding a lucent material, type II of lipid deposits. None of the developmental stages investigated showed intermediate features between any of the three cutaneous products, which accumulate in the syncytial cytoplasms of the secretory units following different biosynthetic pathways, consistent with each gland type. These findings confirm previous results on adult specimens of P. hypochondrialis and P. sauvagei and stress the polymorphism of the serous glands in the genus Phyllomedusa. This morphological variability reflects the wide adaptive flexibility of serous glands in anurans.

Ultrastructure, distribution, and density of lamellar bodies in human peritoneum

OBJECTIVE

To determine the ultrastructure, relative density, and location of lamellar bodies in the various regions, structures, cells, and intercellular matrix in normal human peritoneum; to carry out engineering analysis of the role of lamellar structures in serosal lubricancy and deduce what effect this system may have on the process of peritoneal dialysis.

DESIGN

Five samples of normal human parietal peritoneum obtained at elective operation were fixed in a tannic acid-glutaraldehyde mixture and submitted to examination by transmission electron microscopy. Detailed analysis using reconstruction of serial electron micrographs and tracings of montages were employed in determining location, disposition, density, and geometric patterns of lamellar bodies in all levels of the peritoneal membrane.

RESULTS

Lamellar profiles were found in greatest density enmeshed in surface microvilli and in mesothelial cytoplasm. Lamellar bodies were frequently observed capping the external portion of mesothelial junctional complexes, and within intercellular junctions. Lamellar bodies were also encountered in macrophages, both in the peritoneal cavity and submesothelial tissue, and also in fibroblasts. Lamellar bodies were present in low density in the matrix ground substance of submesothelial connective tissue, in blood vessel walls between smooth muscle, in endothelial cell cytoplasm, and in vascular lumina.

CONCLUSION

Three-dimensional analysis of lamellae on mesothelial surfaces indicates that an arrangement of constantly changing microscopic spheres and cylinders would act as "ball and roller bearings" among the microvilli for the lubrication of opposing surfaces. The entrapment of fluid in lamellar bubbles, which in normal peritoneum fill the microvillous layer, would, if maintained in peritoneal dialysis, constitute a stagnant layer of considerable stability and inertia.

Carbachol, but not forskolin, increases mucosal-to-serosal transport of intact protein in rat ileum in vitro

The effects of the secretagogues forskolin and carbachol on protein uptake in isolated ileum of rats were studied. The mucosal-to-serosal transport of horseradish peroxidase (HRP, mol mass 40 kDa) was measured in Ussing chambers, and afterwards tissues were processed for electron microscopy. In the absence of secretagogues, the flux of enzymatically active HRP was 5 pmol.cm-2.h-1 at a mucosal concentration of 10 microM. Electron micrographs showed vesicles filled with active HRP in enterocytes but no HRP activity in intercellular spaces. Forskolin decreased HRP activity in the cells. Carbachol increased the amount of HRP-filled vesicles in enterocytes and induced HRP filling in some intercellular spaces and tight junctions in the upper parts of the villi. The transepithelial flux of intact HRP increased more than 2.5-fold. This effect was suppressed by atropine. We conclude that cholinergic activation can increase the uptake of intact protein via endocytosis and the transepithelial passage by the induction of a diffusional paracellular pathway. We speculate that the increased transport of intact protein through the intestinal barrier may influence immunologic sensitization to food allergens.

Proliferation of submesothelial mesenchymal cells during early phase of serosal thickening in the rabbit bladder is accompanied by transient keratin 18 expression

Partial outlet obstruction of the rabbit bladder induces serosal thickening and smooth muscle (SM) hypertrophy. Within thickened serosa, submesothelial (mesenchymal) cells differentiate into SM cells after 30 days of obstruction[S. Buoro et al. Lab. Invest. 69, 589-602, 1993]. Here, we show that submesothelial cells transiently express keratin (K) 18 but not K8 soon after obstruction. We investigated a possible relationship between keratin expression and cell proliferation/differentiation in vivo and in vitro. The results of this study indicate that expression of K18 is spatiotemporally related to the pattern of cell proliferation with respect to the localization of an elastic membrane which divides the thickened serosa into an "extrinsic" and an "intrinsic" region. Moreover, K18 is not present in bladder mesenchyma during early development, indicating that its expression in the adult is not attributable to a dedifferentiation process. However, simultaneous K18, K8, and desmoplakin (DP) expression can be induced in normal and thickened serosa upon treatment with bromo-deoxyuridine. Our results indicate that K18 is a marker of proliferating mesenchymal cells in rabbit serosa, whereas the combined expression of K18, K8, and DP might be related to the hypothesized alterations in the stability of gene expression. A model is proposed in which keratin-containing submesothelial cells can act as a "transit" cell phenotype involved in both regenerating mesothelial cells and formation of SM cells.

Ultrastructural observations on the peritoneum in the mouse

The serous mesothelium of the serosa and mesentery of the small intestine in the mouse were examined by scanning and transmission electron microscopy. The serosa consisted of a single layer of flattened microvilli-bearing cells containing nuclei, caveolae and micropinocytotic vesicles. The observations in this study differed from previous reports on mesothelial surfaces in two respects. A surface layer of amorphous material was present over parts of the serosa. This layer probably represents serous fluid trapped by the mesothelial microvilli but is unaffected by prefixation rinsing in saline or ultrasonic cleaning. The layer is lost following osmication and routine processing for transmission electron microscopy. The possibility that a serous fluid layer may be preserved in this way may be useful in assessing changes in the peritoneum. Stomata were observed in the mesentery but there was no evidence of a connection with the lymphatic system. The presence of mesenteric stomata may explain the difference in permeability reported between parietal peritoneum and mesentery.

Three-dimensional arrangement of collagen and elastin fibers in the human urinary bladder: a scanning electron microscopic study

To clarify the arrangements of collagen and elastin fibers of the urinary bladder, we examined 9 human (male, aged 42 to 72) urinary bladders by scanning electron microscopy with chemical digestion methods. The mucosal layer was divided into 3 portions according to the collagen arrangement: the superficial portion interwoven densely by collagen fibrils, the middle portion layered by flat bundles of collagen fibrils and the deep portion made of a loose network of twisted collagen bundles. In the muscular layer, the smooth muscle fascicles were firmly covered with collagen sheets, while each muscle cell in a fascicle was accommodated by a thin sheath of collagen fibrils. The serosal layer consists of wavy collagen bundles piled up in a sheet, which was intercalated by clusters of adipose cells. Elastic fibers were, on the other hand, sparse throughout the bladder wall, except for denser networks around the blood vessels and muscle fascicles and beneath the peritoneal mesothelium. The arrangements of these components were discussed in relation to the mechanical function and compliance of the urinary bladder.

Chloride secretion and function of serous and mucous cells of human airway glands

Cells from the acini of human tracheal glands were grown in culture to produce confluent cell sheets of mucous or mixed seromucous phenotype. Levels of mediator-induced Cl secretion in mucous cells were 2-18% those of seromucous cells. Levels of the cystic fibrosis transmembrane conductance regulator (an apical membrane Cl channel) were also much less in mucous than in seromucous cells. These results suggest that serous cells are more important than mucous cells in providing the fluid component of gland secretions.

Morphological and histochemical study of human submucosal laryngeal glands

BACKGROUND

The respiratory submucosal glands are a major source of secretions in the airway. Human submucosal laryngeal glands have been scarcely studied, with no works existing about their ultrastructure and histochemistry.

METHODS

Samples of epiglottis, ventricle, false vocal folds and true vocal folds were fixed in 10% buffered formalin for histochemical study with conventional and carbohydrate lectin histochemistry. Other samples were fixed in 2.5% glutaraldehyde and conventionally processed for transmission electron microscopy.

RESULTS

The human submucosal laryngeal glands are composed of serious tubules; mucous tubules; collector duct; and final portion of this duct. The serous cells showed sialosulphomucins and affinity for WGA and Con-A lectins. With a previous treatment with neuraminidase, they also labelled with PNA. The mucous cells contained sialosulphomucins and showed affinity for WGA and DBA lectins in the samples proceeding from blood group A, and for WGA, UEA-I and LTA with those from blood group O. Ultrastructurally, the serous cells presented a wide variety of granules, cells in which seromucous granules predominated. The mucous cells presented larger-sized granules which were very electron-lucent. The collector duct was composed of mitochondria-rich cells and basal cells. A cell which we have termed "intermediate" was identified in the transition zone between the mucous tubules and the collector duct, and in the final portion of the collector duct. It had morphological characteristics as if it were a transition between a goblet cell and collector duct cell. Some nerve endings with cholinergic and peptidergic vesicles were found among the myoepithelial cells.

CONCLUSIONS

These glands presented some histological differences from the bronchial glands, the mucous secretion was related to the blood group antigens, and the serous cells showed a wide variability in their secretory granules, many of them being of a seromucous type.

Lamellar bodies in synoviocytes, mesothelium and specific epithelia as possible site of auto-antigen in rheumatoid disease

Intracytoplasmic lamellar organelles identical in ultrastructure to surfactant-containing lamellar bodies found in type II pneumocytes, have been demonstrated in other tissues, in synoviocytes and mesothelial cells, in a distribution pattern which reflects the systemic expression of rheumatoid disease. Antibodies raised against surfactant protein A (SP-A), exhibit a ranking of tissue reactivity in area, intensity and density of cells which also parallels the frequency and degree of pathological involvement characteristic of rheumatoid disease, showing in ascending order of immunopositivity, lacrymal and salivary epithelia, pulmonary parenchyma, mesothelium and synoviocytes. Maximal tissue reactivity to anti-SP-A antibodies was found in the synovium of 55 rheumatoid patients exhibiting classical histopathological appearances of RA, in a pattern of immunostaining identical to that obtained with ML30, an antibody to mycobacterial heat shock protein 65kDa which, in turn, cross-reacted with SP-A in dot blot testing.

Giant mitochondria in the seromucous secretory cells of the accessory submandibular gland of the long-haired fruit bat, Stenonycteris lanosus

Giant mitochondria, measuring up to 6.4 microns in diameter, are present in the seromucous secretory cells of the accessory submandibular gland of the long-haired fruit bat, Stenonycteris lanosus. These mitochondria, as well as all of the smaller ones in the same cells, contain in their matrix compartment an abundance of 33 nm threads that probably consist of protein. Some mitochondria, regardless of size, contain 5 nm helical filaments within an expanded crista. Despite their altered morphology, the enlarged mitochondria in the accessory submandibular gland of S. lanosus must be able to function normally in energy metabolism, since the secretory cells in which they are found elaborate numerous secretory granules.

[The enzymatic barrier of the small intestine]

The small intestine's barrier functions are reviewed. The data on mechanical (passive) and active protective systems of the organism against various antigens, toxic substances and proteins, is presented. An important role of these protective systems as an enzyme apparatus of epithelial and postepithelial layers of the small intestine's mucose, is shown.

Multiple myeloma of the serosa coat

We report on a 47-year-old male patient with IgA-kappa plasmacytoma, who 12 months subsequent to diagnosis developed marked ascites. On light and electron microscopy morphologically identical plasma cells with bizarre intracytoplasmatic material were found in the bone marrow, pleural exudate, and ascites fluid. This kind of extramedullary spread is extremely rare and usually resists therapy. The mean survival rate for the 9 patients with malignant plasmacellular ascites whose cases have been documented so far was 2 months. After progression under VCMP regimens our patient has been successfully treated over a period of more than 4 years with i.v. VP16 monotherapy with additional intermittent local administration of methotrexate and systemic poly-chemotherapy according to the VAD scheme.

[The circulatory bed of the human uterine tube]

By means of combined morphological methods blood vessels have been studied in 54 uterine tubes of child-birth women. The main pathways for carrying and distribution of blood to corresponding parts of the tube are sector arteries. They are situated in the subserous tela along the anterior and posterior semicircles of the organ. The microcirculatory bed (MCB) of the uterine tube is presented by serous, subserous, muscular and mucosal plexuses. The MCB of the serous tunic is characterized by vascular compositions--modules. Angioarchitectonics of the mucosal tunic is determined with differences in vascularization of complex and simple folds. Organospecific for small arteries and veins of the tubes is presence of vascular mechanisms, regulating the blood stream (intimal cushions, muscular-elastic constrictors, valves and others). Blood capillaries of the mucosal tunic possess a number of ultrastructural peculiarities: thickened peripheral part of endotheliocyte cytoplasm, that contains fenestrae; wide continuous basal membrane with pericytes in its duplication; three types of pericytic-endothelial contacts etc.

Secretion of lingual lipase and amylase from rat lingual serous glands

The effects of various secretagogues on the release of lingual lipase and amylase from rat lingual serous glands was examined in vitro and in vivo. After incubation, the media and tissues were assayed for lingual lipase and amylase activity to determine percent of secretion. In vitro secretion of lingual lipase and amylase stimulated by the cholinergic agonist, carbamylcholine chloride (carbachol), was 28.3 +/- 1.7, 48.0 +/- 3.2, and 55.9 +/- 2.4% and 18.1 +/- 1.7, 26.4 +/- 3.0, and 28.0 +/- 2.5%, respectively, for 30-, 60-, and 90-min incubations. The beta-adrenergic agonist, isoproterenol, and the adenylate cyclase activator, forskolin, elicited very little secretion in vitro; the 90-min values with isoproterenol were 16.8 +/- 7.1% lingual lipase and 6.0 +/- 2.6% amylase. The alpha-adrenergic agonist, phenylephrine, did not stimulate enzyme secretion. Morphological assessment of incubated tissues revealed that carbachol induced a rapid and extensive degranulation of the acinar cells, while isoproterenol caused only minimal exocytosis. In vivo stimulation by the cholinergic agonist, pilocarpine, caused rapid secretion, with maximal secretion occurring by 1 h. In vivo secretion stimulated by isoproterenol was slow, but by 4 h secretion was comparable to that induced by pilocarpine. In vitro, there was a significant difference between the percentages of lingual lipase and amylase secreted, which could not be accounted for by the presence of proteases or microbial products or the lack of stability of the enzymes during the incubation period. Neurotransmitter regulation of protein secretion by the lingual serous (minor salivary) glands appears to be principally cholinergic in contrast to the beta-adrenergic stimulation of protein secretion by the parotid (major salivary) gland.

Serosal tissue: reactive tissue as a model for understanding mesotheliomas

Serosal tissues consist of a surface mesothelial layer and subsurface spindled connective tissue cells. Surface cells are decorated with antibodies to both low and high molecular weight cytokeratin whereas subserosal cells only express the intermediate filament vimentin. Serosal injury results in the proliferation of multipotential subserosal cells (MSC) which have the ultrastructural morphology of myofibroblasts and yet co-express low molecular weight cytokeratin and vimentin. These cells appear responsible for the re-establishment of surface mesothelium during which they acquire high molecular weight cytokeratin and loose vimentin. There are many parallels between reactive and neoplastic serosal tissues. Desmoplastic/sarcomatoid mesotheliomas resemble the MSC and co-express low molecular weight cytokeratin and vimentin and epithelial mesotheliomas resemble surface mesothelium and express both low and high molecular weight cytokeratin. The ability of normal serosal tissue to modulate its cell shape and intermediate filament expression helps understand the diversity of serosal tumors.

[Structural and functional characteristics of the cellular reaction of the bladder epithelium in the frog to calcium extraction from the apical and basolateral membranes]

Extraction of Ca++ ions from cells of the frog urinary bladder serosa side is followed by an increase in the bladder wall permeability for water and inulin. Ultrastructural changes were observed, such as destruction of cell junctions, swelling of the cell and their organelles, reconstruction of the cytoskeleton elements. The free calcium Ringer solution injected in the bladder lumen does not change the permeability of the wall for water and sodium ions. In this case the cell response to the antidiuretic hormone decreases; the ultrastructure of cells and intercellular junctions is not disturbed; the distribution of intramembrane particles on the P- and E-faces of the apical membrane is normal. The above results indicate that there are qualitative differences in the cell response towards the extraction of Ca++-ions between the serosal and mucosal membranes. This also suggests that on the external surface of the apical membrane Ca++ ions may play a very important role in redistribution of intramembrane particles under the action of the antidiuretic hormone.

Quantitation of the secretory cells of the ferret tracheobronchial tree

The tracheal epithelium of the ferret has few goblet cells while sero-mucous submucosal glands are present in large numbers throughout the length of the trachea and bronchi. The epithelium consists mainly of ciliated cells and of dark cytoplasmic non-ciliated cells that sometimes contain secretory granules. Any 'respiratory tract fluid' secreted into the ferret trachea is probably mainly glandular in origin. The epithelium contains neutrophils and a few mast cells and eosinophils. Nerve fibres are virtually absent from the epithelium, and this may be associated with a lack of the cough reflex from the ferret trachea. From a morphological point of view, the ferret trachea may well make a good model for the study of submucosal gland secretions.

Localized fibrous tumour of serosal surfaces. Immunohistochemical and ultrastructural evidence for a type of mesothelioma

It is uncertain whether localized lesions of serosal membranes have a kinship to mesotheliomas or are truly fibromatous in nature. Ultrastructural and immunohistochemical investigations were carried out on 12 localized benign and malignant pleural and peritoneal tumours from 10 patients. Electron microscopic findings, including the consistent and non-fibroblastic cellular organization of localized neoplasms, the presence of some form of intercellular junctions in 7 of 10 cases, basal lamina deposition in 3 cases, and polarized microvilli in one case indicated a form of mesothelial differentiation. Using monoclonal and polyclonal antibodies, positive immunostaining of tumour cells for cytokeratin peptides was detected in one case, while antibody to vimentin stained four cases. Light microscopic, ultrastructural and immunohistochemical features of one benign localized serosal tumour, with a unique blend of epithelial and spindle cells, provided further evidence for a histogenic link between localized serosal tumours and diffuse epithelial mesotheliomas. On the basis of the current findings and reports in the literature, it would appear that the majority of localized tumours of serosal membranes are a subset of mesothelioma, while a minority are fibromas.

Reactive and neoplastic serosal tissue. A light-microscopic, ultrastructural, and immunocytochemical study

Normal and reactive non-neoplastic serosal tissues and a spectrum of serosal neoplasms were studied using light-microscopic, ultrastructural, immunocytochemical, gel electrophoretic, and immunoblot techniques. Normal surface mesothelium expressed both low- and high-molecular-weight cytokeratins, whereas the scattered submesothelial cells were decorated only with antibodies to vimentin. Reactive non-neoplastic subserosal cells, however, coexpressed both low-molecular-weight cytokeratin and vimentin and demonstrated the ability for surface differentiation during which higher-molecular-weight cytokeratins were acquired and vimentin was lost. The authors suggest the term "multipotential subserosal cells," recognizing the unique intermediate filament expression of reactive subserosal cells and the ability for surface differentiation. The intermediate filament expression of the sarcomatoid/desmoplastic mesotheliomas resembled the MSC, whereas epithelial mesotheliomas resembled surface mesothelium. These findings have potential usefulness for diagnostic pathology.

Intercellular junctions in upper airway submucosal glands of the rat: a tracer and freeze fracture study

The structure of intercellular tight junctions of rat airway submucosal glands was examined by freeze fracture techniques and their permeability assessed by the use of colloidal lanthanum. The submucosal glands were organized into three distinct regions: a) serous tubules and b) mucous tubules lined, respectively, by serous and mucous cells, and c) ducts lined by cuboidal epithelial cells, containing few secretory granules, and some ciliated cells. The mean number of parallel fibrils constituting the tight junctions between serous cells was 3.6 +/- 0.4, which was significantly smaller than those between any of the other cell types. Colloidal lanthanum permeated the tight junctions between serous cells up to the level of the acinar lumen. There was a progressive increase in the mean number of parallel fibrils of tight junctions between mucous (5.1 +/- 0.6), ductal (5.4 +/- 0.5), and ciliated cells (8.5 +/- 0.7); none of these junctions was permeated by colloidal lanthanum. These results imply that tight junctions between serous cells are more permeable to small water-soluble solutes than those present in the more proximal portions of the gland. Gap junctions were observed between serous cells and between mucous cells, suggesting that these secretory cells may be electotronically and metabolically coupled.

Ultrastructure of the parotid gland in the little brown bat

The ultrastructure of the parotid gland was examined in the little brown bat. The seromucous acinar cells contained abundant granules of variable morphology. These granules were characterized by a submembranous dense layer consisting of fine parallel slats. In some bats, the matrix of the granules was structureless, whereas in others it consisted of closely packed but randomly arranged bundles of tubules. The intercalated ducts had a highly developed rough endoplasmic reticulum, often containing large numbers of intracisternal granules. In contrast, only a few secretory granules were present in the supranuclear cytoplasm. The striated ducts, which exhibited the characteristic basal striations consisting of vertically oriented mitochondria and highly folded plasmalemmas, contained numerous small dense granules in a subluminal band. These granules had a paracrystalline substructure with a periodicity of 8 nm. Excretory ducts strongly resembled striated ducts. They showed the same kind of basal striations and about half their constituent cells contained small paracrystalline granules.

Histochemical properties of the respiratory tract epithelium in different species

The comparative composition of secretory components and cell surface moieties is described in this review on epithelial cells of the respiratory tract in mouse, rat, and humans. The discussion concerns mainly the nature of the carbohydrate-rich secretory substances and glycocalyx components present in the various types of epithelial cells in the 3 species. Older methods for characterizing acid groups and vicinal glycols of the complex carbohydrates and more recent methods for identifying specific terminal and internal sugars with labeled lectins are outlined, including techniques for both light and electron microscopic examination. Knowledge derived from the application of these methods is detailed for the surface glycocalyx of secretory cells lining the proximal and distal airways and alveoli, as well as for the glycocalyx of ciliated cells and membranous pneumocytes in each species. Histochemically derived knowledge of the composition of substances in secretory granules of surface epithelial cells is also summarized. The review concerns as well the nature of secretory products in serous and mucous cells of the glands in the lamina propria of trachea and bronchi. The available data delineate major differences between serous cell secretions compared with mucous cell secretions as well as differences between species for each cell type. In addition, ABO blood group dependent differences have been demonstrated in the human glands.

The pleura: a combined light microscopic, scanning, and transmission electron microscopic study in the sheep. I. Normal pleura

The structural features of the ovine pleura are described using light, scanning, and transmission electron microscopy. Extensive sampling of the visceral and parietal pleura revealed considerable variation in both surface morphology and pleural interstitial anatomy. Variations of mesothelial surface were encountered and these were due to microvillar density and length. The pleural interstitium varied considerably in thickness, being relatively sparse in the anterior lung lobes, where respiratory excursion is least, and much more robust in the caudal lung lobes, where respiratory excursion is greatest. A similar correlation was observed with regard to the abundance and extent of the elastic meshwork embedded in the interstitium. The parietal pleura had openings which connected directly with the lymphatics in the underlying interstitium, thus forming a direct channel between the pleural cavity and the lymphatic system.

Morphological and cytochemical investigation of human mesothelial cells from pleural and peritoneal effusions: a light and electron microscopy study

We investigated the morphological and cytochemical properties of mesothelial cells obtained from pleural and peritoneal effusions of patients with various diseases. The morphological features were studied by light and electron microscopy and by cytochemical methods. The different kinds of contact between mesothelial cells and their interaction with lymphocytes were observed and the transition of mesothelial cells to macrophages and/or fibroblasts was demonstrated.