Base Of Epithelial Cells Research Articles

Spread of Trichomonas gallinae in species of birds in balad district with the effect of infection on histological picture

Trichomoniasis in birds is one of the most common types of infection that affects birds worldwide, and it is caused by Trichomonas gallinae. This study was carried out to examine and determine the presence of T. gallinae in Columba livia, Streptopelia turtur, and Gallus gallus domesticus microscopic examination (direct smear and Giemsa stained). The study was conducted in Balad district in Salah al-Din Governorate, north of Baghdad, Iraq, from October 2021 to March 2022. The results showed the microscopic examination that the incidence of T. gallinae average was 19.17%, distributed between 14.16% for C. livia, while S. turtur constituted 14.0%, and the rate of G. gallus domesticus was 27.92%, but there were no significant differences at P> 0.05 among these bird species. The gender of birds showed that there were no differences between a male and a female of each type. In males of the two types of pigeons (C. livia, and S. turtur) and Gallus gallus domesticus, the rates of infection were (16.10, 15.05, and 5.75 %), while in female types of C. livia, S. turtur, and Gallus gallus domesticus, the rates of infection were (12.17, 12.28, and 31.11%), respectively. The incidence of T.gallinae is distributed for the most studied months, as it showed the highest infection rate for pigeons in January at 20% for C. livia, and 32% for S. turtur, and while January to February had 33% as the highest rate of infection in G.gallus domesticus, although there were no significant differences (P>0.05) among studied birds. The histological changes of infected organs for all species as well as for healthy birds, as the parasite was located in the upper part of the gastrointestinal tract, which was tongue, pharynx, vesicle, and gizzard. Granular lesions and infiltration of lymphoid and inflammatory cells were found, as well as degeneration in a number of gland-forming cells. The mucous in the affected areas as a result of parasite penetration into the tissue, congestion of blood vessels and appearance of granulation tissue in the upper part of healthy alimentary canal was compared with that of C. livia, S. turtur and Gallus gallus domesticus of Balad distract. In pharynx, the infiltration of large numbers of white blood cells, scattered and nodular form, and the sloughing of surface cells, and presence of strands of sloughed keratin appeared in pharynx cavity, and in vesicle tissue, and in gizzard, the histological sections showed the presence of parasite in muscle layer surrounded by a white transparent band, the infiltration of a large number of white blood cells appeared, and degeneration of epithelial cells at the bases of epithelial cells appeared in mucous folds.

Macrophages Maintain Epithelial Barrier Integrity in the Distal Colon by Limiting the Absorption of Fluids Containing Fungal Products

The colon is responsible for absorbing fluids. It contains many microorganisms including fungi, which are enriched in its distal segment. The colonic mucosa must thus tightly regulate fluid influx to avoid absorption of fungal metabolites, which can be toxic to epithelial cells and reach the blood circulation, leading to barrier dysfunction and sepsis. How this is achieved remains unknown. Here, we describe a mechanism by which macrophages rapidly check the fluids absorbed through epithelial cells to avoid intoxication of colonocytes. This mechanism relies on a population of distal colon macrophages equipped with balloon-like protrusions (BLPs) inserted at the base of epithelial cells. BLPs sample absorbed fluids and stop absorption when fluids contain fungal toxins. Without macrophages or BLPs, epithelial cells keep absorbing fluids containing fungal products, leading to apoptosis and loss of epithelium integrity. These results reveal an unexpected role of macrophages in the maintenance of colon-microbiota interactions in homeostasis.

Scanning and transmission electron-microscopic study of the development of the podocyte in the human fetus.

The metanephric kidneys of seven human fetuses at 11-17 weeks' gestation were examined by scanning and transmission electron microscopy in order to evaluate differentiation of glomerular podocytes. When glomeruli were in the stage of S-shaped bodies, the surface of the visceral epithelium of renal corpuscles was smooth, with indistinct cell borders. As the glomeruli developed, visceral epithelial cells of renal corpuscles became spherical and resembled clusters of grapes in dense aggregation. In this stage, processes and foot processes were simultaneously formed at the base of epithelial cells. As glomeruli further differentiated, visceral epithelial cells of renal corpuscles began to separate from one another and became flat with the development of vascular loops. Processes and foot processes were exposed for the first time in Bowman's space. In this stage, the degree of differentiation of epithelial cells varied widely among various sites of the glomerulus. As glomeruli developed further, projections became more complex and epithelial cells began to show structures similar to those of adult epithelial cells. The adjacent foot processes arose from different cells throughout the period of morphological differentiation.

In vivo and in vitro experimental intestinal amebiasis in Mongolian gerbils (Meriones unguiculatus).

One of the main drawbacks of experimental amebiasis is the lack of an adequate animal model for invasive intestinal lesions. Mongolian gerbils are useful because both intestinal and hepatic amebiasis can be produced experimentally with Entamoeba histolytica trophozoites. In this paper we show results obtained with in vivo and in vitro models of intestinal amebiasis in gerbils. We inoculated gerbils intracecally with monoxenic cultures of a highly virulent E. histolytica HM1:IMSS substrain. In the in vivo model an increase in mucus production was observed during the first 6 h of interaction. Microulcerative mucosal lesions appeared at 24-72 h postinoculation. Inflammatory infiltrate and edema of the lamina propria were associated with superficial foci of necrosis. At 96 h the cecal mucosa had an almost normal appearance and live amebas were no longer detected. In the in vitro model, early damage was detected in cecal strips mounted in Ussing chambers as a rapid fall in potential difference, short-circuit current, and transepithelial resistance that correlated with the extent of the microscopic lesions produced. The latter consisted of cellular edema and the appearance of small, translucent vacuoles at the base of epithelial cells. Further damage led to loss of intercellular junctions, destruction of interglandular epithelial cells, and edema of the lamina propria. The present results demonstrate that the gerbil is useful as an experimental model for the analysis of early stages of invasive intestinal amebiasis both in vivo and in vitro.

Appearance and distribution of laminin a chain isoforms and integrin α2, α3, α6, β1, and β4 subunits in the developing human small intestinal mucosa

Laminin, a major component of basement membranes, is well known in its classical heterotrimeric form (B1-A-B2) to regulate diverse biological functions, including cell polarization and differentiation. However, the role of merosin, a laminin-like molecule in which an M chain is substituted for its homologous A chain, remains largely unknown. In the present study, we analyzed by indirect immunofluorescence the expression and distribution of these four laminin chains as well as the integrins alpha 2 beta 1, alpha 3 beta 1, alpha 6 beta 1, and alpha 6 beta 4, four potential receptors, at the epithelial-mesenchymal interface of the developing human small intestine, with a panel of specific monoclonal antibodies. Beginning at 7 weeks of gestation and throughout mucosal organogenesis, the B1 and B2 chains were uniformly detected at the epithelial basement membrane. The A chain also was detected beginning at 7 weeks, and its distribution at the basement membrane remained uniform throughout villus (9+ weeks) and crypt (16+ weeks) formation. In contrast, M chain expression was not observed until 16 weeks; between 16 and 20 weeks, it was exclusively associated with the base of epithelial cells that comprised the forming crypts. Integrins alpha 6 beta 1 and alpha 6 beta 4, as determined by their subunit immunolocalization, appeared to be expressed by all enterocytes from 7 to 20 weeks. In contrast, the expression of the alpha 2 beta 1 and alpha 3 beta 1 integrins was found time- and site-restricted. The alpha 2 subunit was predominantly detected in the epithelial cells of the intervillous area and its derivative, the crypt, whereas the alpha 3 subunit was strongly expressed by all epithelial cells except those located at the bottom of 19-20-week-old crypts. Taken together, these observations demonstrate that both compositional changes in the basement membrane and differential expression of receptors occur during human intestinal organogenesis, suggesting that epithelial cell-matrix interactions play a role during development.

Entamoeba histolytica: Electrophysiologic and Morphologic Effects of Trophozoite Lysates on Rabbit Colon

Although in acute intestinal amoebiasis the events occurring during the initial interaction of Entamoeba histolytica trophozoites with the mucosa of the large intestine probably determine the invasion by the parasites, an appropriate experimental model to study them does not exist. To develop such a model we used rabbit colonic segments (0.28 cm2) mounted in Ussing-type chambers. These preparations had electrophysiological properties (potential difference, short-circuit current, and electrical resistance) similar in magnitude and duration to those reported for stripped colonic mucosa. Lysates from 50,000 Entamoeba invadens PZ strain trophozoites (virulent to reptiles) added to the mucosal side of preparations had no effect, whereas lysates from the same number of E. histolytica HM1 strain trophozoites (virulent to humans) caused an immediate decay of electrophysiological properties. E. histolytica lysates induced the formation of translucent vacuoles at the bases of epithelial cells and separation between the epithelium and the lamina propria. The specificity and speed of the electrophysiologic effects of E. histolytica lysates and their correlation with the microscopic lesions suggest that this model may be useful to analyze the initial pathogenic events of intestinal amoebiasis.

Lipid in the human gallbladder mucosa. A histochemical study by light and electron microscopy.

The distribution of lipids in the epithelium of 70 gallbladders removed for cholecystitis was investigated histochemically. Lipid was demonstrated in 68 gallbladders--cholesterol and its esters, triglycerides, free fatty acids and phospholipids. Neutral lipid was found at the bases of epithelial cells in 90 per cent and at the apex in 10 per cent of the gallbladders. Phospholipid was shown at the apex of epithelial cells in 64 per cent of the gallbladders. Electron microscopy in 12 specimens revealed cholesterol in and between the epithelial cells and in the underlying connective tissue.

Basal processes on duodenal epithelial cells of man, mouse and rat

Localized ischaemia of duodenal mucosa induced either by ligation or cautery of a small branch of the coeliac artery resulted in the loss of epithelial cells of duodenal villi in young mature inbred mice. Biopsies from normal human duodenum and mouse duodenum placed in non-oxygenated physiological saline for 20 min showed a similar loss of epithelial cells. In all cases, scanning electron microscope (SEM) examination revealed that processes extended from the base of epithelial cells through the underlying basement membrane. When duodenal tissues were bathed in solutions of EDTA or sodium azide, basal processes were not seen by SEM. Transmission electron microscopy (TEM) of duodenal tissues from man, rat, and mouse revealed basal processes. Because all duodenal epithelial cells appear to have basal processes, it is proposed that they may play an important role in moving absorbed substances across the villous basement membrane barrier along an intracellular concentration gradient, and in thus facilitating absorption. There are no indications which would suggest that basal processes are the result of a pathological process, and the presence of similar basal processes in other tissues is noted.

Duodenal epithelial cell migration and loss in NZB mice

Abstract The duodenal mucosa of NZB mice is characterized by the presence of a high crypt/villus (? vestibule/villus) ratio. Scanning electron microscopy of villi and the intervillus floor of NZB mouse duodenum has revealed that death of epithelial cells may occur at any part of the mucosa and the position at which death occurs is related to the extent to which migration is impeded. For this reason a variable and possibly only a small proportion of all villus cells are shed from apical extrusion zones. In NZB mice because of the large numbers of crypts (? vestibules) producing cells for each villus even normal crypt cell proliferation would result in considerable competition for migration pathways to villous surfaces. Our interpretation of SEM micrographs suggest that ‘traffic jams’ of migrating epithelial cells occur, and the outlines of epithelial cells in such situations are deformed in accordance with the pressures to which they are exposed. Because of their limited lifespan, cells trapped in such ‘traffic jams’ die and are shed from such positions. The rootlike processes which occur on the bases of epithelial cells could be expected to impede cell migration. It is proposed that epithelial cell migration occurs because of pressures which result from the growth to mature size of recently divided cells and the fact that the villous basement membrane is a thixotropic gel. When ‘maturation pressure’ reaches a critical level, localized deformation and flow is initiated in the basement membrane, permitting the cell column under pressure to move until the pressure is exhausted. As the cell moves, the deformed basement membrane is displaced and flows behind the basal process of the moving cell. When movement stops the basement membrane gel reforms. Thus the ability of cell columns to move independently does not breach the integrity of the epithelial cell layer, although it implies that tight junctions between columns must be able to be disrupted and reformed.

Ultrastructure of nerve plexus in flatworms. III. The infra-epithelial nervous system.

In addition to a submuscular and subepithelial nerve plexus an infra-epithelial nerve-net also occurs in Notoplana acticola. It contains naked nerve cells which lie between the bases of epithelial cells. Individual neurites occur separately or in small tracts. Synapses contain clear spherical vesicles and are polarized. Post-synaptic neurites tend to be flat and ribbon-like. Rhabdite and mucus secreting cells in the epithelium have synapses associated with them. Neurites ending on the rhabdites appear to originate in the subepithelial plexus. The "sensory-free nerve endings" of earlier workers are reinterpreted as being motor terminals on epithelial secretory cells.

Fine structure of nerve terminals in the human gut

AbstractAn electron microscopical investigation was made of neuronal terminals in operatively removed human duodenum and jejunum. No intraepithelial neuronal elements were found. The lamina propria mucosae, submucosa and muscular layer possessed, in addition to large bundles of unmyelinated nerve fibers, small ones consisting of three or four axons wrapped by infoldings of one Schwann cell. Some of these axons were light; others contained mitochondria and clear vesicles measuring 200–500 Å across. Still other axons had dense‐cored vesicles with a diameter ∼ 700 Å. The plasma membranes of vesiculated axons were not thickened and only in part invested by the Schwann cell, but were covered by a basement membrane. Such profiles were interpreted as nerve terminals, and were separated from fibers of the muscularis mucosae, bases of epithelial cells and submucous capillaries by interspaces measuring 5,000–6,800 Å. The gap between neuronal terminals and smooth muscle in the muscular wall was smaller (900 Å, more often 1,500–3,000 Å). The myenteric plexus contained nerve bundles consisting of the usual axons and of preterminals; some of the latter contained small clear vesicles, others predominantly larger granulated vesicles, and still others a mixture of both types of vesicles. The similarities and differences of neuronal terminals occurring in animals and in man were pointed out. The significance of the findings of this study was discussed in the light of current concepts of the physiology of autonomic nerve transmission.

The histogenesis of basement membranes.

A parietal yolk sac carcinoma of the mouse that secretes large quantities of basement membrane-like material has been used to study the formation of basement membranes. Suitably characterized fluorescein-labeled antibodies against this material stained basement membranes of epithelial structures and vessels, as well as reticulin. When absorbed with reticulin and vascular basement membranes of the spleen until these structures no longer fluoresced, the antibody still stained the basement membrane-like material of the tumor, its normal embryonic counterpart (Reichert's membrane), and the basement membranes at the bases of epithelial cells. The observation made previously that parietal yolk sac cells secreted, in the absence of connective tissue and reticulin, the basement membrane (Reichert's membrane) upon which they rested has been confirmed through the localization of ferritin-labeled antibody to the endoplasmic reticulin of the secreting cells. Since a basement membrane proven to be an epithelial secretion is antigenically similar to basement membranes at the bases of all epithelial cells studied but antigenically different from connective tissue elements, it is postulated that the basement membranes at the bases of epithelial cells in general are an epithelial secretion, and are not a condensation of ground substance as is commonly believed.