Morphofunctional characteristics of the duodenum in the early stages of experimental escherichiosis

Using the model of experimental colibacillosis in mice morphological, immunomorphological and morphometrical studies of duodenum 1 to 24 hours after inoculation were performed. Typical dynamics of cellular composition in the intestinal wall, accompanied with increased lymphoplasmacellular infiltration, and dystrophic changes in cells of submucosal and intermuscular neuroplexuses were found. The data obtained testify, that the infectious process at the acute state of experimental colibacillosis has an immune character (immediate hypersensitivity of local type), characterised by increasing in immunoglobulin-containing cells and including in this process of mast and endocrine cells.     

An analysis of the ultrastructure of epithelial cells of the rat proximal tubule at early stages of penicillin elimination

A study was made of the ultrastructure of epithelial cells of the rat proximal tubules nephrons 25-30 seconds, and 15 and 30 minutes following penicillin injection. The morphological changes in the transporting cells that were observed involved the dilation of the inner cavities of canals and cisterns of the endoplasmic reticulum. The number of elements of the smooth endoplasmic reticulum concentrated on the periphery of the cell, near the basolateral border, was seen to increase. Microbodies appeared enlarged with the appearance of the nucleolus; the electron density of the cytoplasmic ground substance fell down. The space between cells augmented, and the interstitial space between infoldings of the basal plasmalemma was much broadened. Similar morphological changes but different in the intensity were found at either stage examined. The maximum changes were established 25-30 seconds following penicillin injection.     

Ultrastructure of pericytes in early stages of histamine-induced inflammation

Physiological and ultrastructural assessment of changes in the walls of venules in the rat cremaster muscle after administration of histamine indicates that pericytes have essential roles in the normal functioning of venules during inflammation. Fluorescein-labelled albumin was used to quantitate macromolecular leakage and to select suitable venules for ultrastructural analysis 4 and 7 minutes after addition of histamine. Pericytes were concentrated over endothelial cell junctions and gaps. At 4 minutes, when albumin leakage was becoming detectable, gaps between endothelial cells were observed in the venule wall. In 24 serially sectioned gaps, pericytes formed covers, with contact points to the endothelial cells along the sides of the gaps. At 7 minutes, when albumin leakage was maximal, gaps with pericyte covers were still evident, but more commonly observed were pericyte covers over closed endothelial cell junctions. Spaces between the innermost pericytes and endothelial cells were enlarged by an order of magnitude, from 95 nm in controls to 872 nm at 4 minutes and 958 nm at 7 minutes. Pericytes formed coverings or bridges over inclusions of extravasated cells, fluid, proteins, and the vascular label monastral blue. The data indicate that pericytes protect the endothelial lining of venules during histamine-induced inflammation by forming a cohesive covering across gaps.     

Role of sipA in the early stages of Salmonella typhimurium entry into epithelial cells

Salmonella virulence depends on an ability to invade host cells, which is in turn dependent on a type III protein secretion system encoded in Salmonella pathogenicity island 1 (SPI1). Several protein targets of the SPI1‐encoded secretion system are translocated into host cells, where they subvert cellular processes that contribute to bacterial invasion, actin rearrangement, membrane ruffling and other aspects of virulence. We examined the role of sipA (encoding the translocated protein SipA) and found that a sipA mutant was significantly less invasive in Madin–Darby canine kidney (MDCK) cells than in its parental strain at the earliest stages of infection (5 min). The invasion defect associated with sipA was no longer apparent after 15 min of infection. Confocal microscopy of F‐actin in tetramethyl rhodamine isothiocyanate (TRITC)–phalloidin‐stained MDCK cells revealed no difference in either the frequency or the morphology of membrane ruffles induced by wild‐type and sipA mutant strains of S. typhimurium. Time‐lapse phase‐contrast microscopy of membrane ruffle propagation in live cells confirmed that the sipA mutant induced membrane ruffles as efficiently as the wild‐type bacteria. These studies also revealed that, after ruffle propagation, individual sipA mutant S. typhimurium either invaded more slowly than wild‐type bacteria or failed to invade at all. Furthermore, although wild‐type S. typhimurium typically maintained a position central to the developing membrane ruffle, sipA mutant bacteria frequently moved initially to the periphery of the spreading ruffle and were sometimes observed to detach from it. A wild‐type pattern of invasion was restored to the sipA mutant after the introduction of sipA on a plasmid. Together, these data indicate that loss of sipA significantly decreases the efficiency of S. typhimurium invasion at the early stages of infection without affecting its ability to induce membrane ruffles. It thus appears that the secreted effector protein SipA promotes invasion by a previously unrecognized mechanism separate from the induction of membrane ruffling per se.     

A quantitative study of epithelial alterations during the early stages of experimental colonic tumorigenesis in mice

The weekly administration of 1,2-dimethyl-hydrazine (DMH) by subcutaneous injection for a period of 16-20 weeks is a well known procedure for producing colonic tumors in mice and rats. Quantitative histomorphological, histochemical and kinetic studies, as well as investigation of the significance of epithelial cell density were carried out in mice between the 7th and the 91st day after the first DMH injection. These studies showed that between the 28th and the 35th day, several simultaneous alterations in the colonic epithelium involving modification of glandular form, decreased mucus secretion, an increase in epithelial cell density and an increase in the number of S phase cells (BrdU labeling index: LI). Around the 35th day, the glands tended to expand and from the 35th to the 63rd day, they were stretched and displayed compartments of dedifferentiated and non-mucinous crypts (DNMC). In these crypts the cell density became very high, reaching twice the control value on the 91st day. This feature was accompanied by alteration in cell morphology and by an increase in the available basement membrane area. A decrease in mucus secretion was apparent from the 14th day and by the 63rd day, mucus secretion was only about 60% of the control value in all crypts. The LI was increased until the 35th day following which a paradoxical and progressive decrease occurred in all glandular compartments.     

Ultrastructure of epithelial cells in rat's epididymal caput in experimental hyperprolactinemia induced by metoclopramide

The aim of the performed studies has been to find out wether or not the ultrastructural alterations of the epithelial cells in the rat's epididymal caput occur in hyperprolactinemia induced by metoclopramide and to see if the observed changes are of reversible character. It has been revealed that prolactin concentration was twice as high as in control animals due to peritoneal administration of metoclopramide in a dose of 2.2 mg/kg body mass, given for 14 days. The ultrastructural alterations in the principal cells of epididymal caput affected cellular organelles being involved in proteins synthesis, glycosylation, secretion as well as energetic processes. They were manifested by decreased amount of rough endoplasmic reticulum, widening of its cisternae combined with degranulation, distension of Golgi apparatus cisternae, elevated number of vesicles in apical part of the cells, and changes in mitochondria. The termination of metoclopramide administration made prolactin concentration exhibit values being almost similar to those determined in control rats, whereas the ultrastructural changes in the principal cells were found to be reversible.     

Antimicrobial peptides in the duodenum at the acute and convalescent stages in patients with diarrhea due to Vibrio cholerae O1 or enterotoxigenic Escherichia coli infection

Patients with acute watery diarrhea caused by Vibrio cholerae O1 or enterotoxigenic Escherichia coli (ETEC) were analyzed for innate immune factors produced by the epithelium during the disease process. Duodenal biopsies were obtained from study participants at the acute (day 2) and convalescent (day 21) stages of disease. Levels of α-defensin (HD-5 and -6), β-defensin (hBD-1-4), and cathelicidin (LL-37) mRNAs were determined by real-time qRT-PCR. hBD-2, HD-5, LL-37 peptides were analyzed in duodenal epithelium by immunomorphometry. Concentration of hBD-2 in stool was determined by ELISA. Specimens from healthy controls were also analyzed. hBD-2 mRNA levels were significantly increased at acute stage of diarrhea; hBD-2 peptide was detected in fecal specimens but barely in duodenal epithelium at acute stage. Immunomorphometry analysis showed that Paneth cells contain significantly higher amounts of HD-5 pre/propeptide at convalescence (P<0.01) and in healthy controls (P<0.001) compared to acute stage, LL-37 peptide levels also decreased at acute stage while mRNA levels remained unchanged. mRNA expression levels of the other antimicrobial peptides remained unchanged with higher levels of α-defensins than β-defensins. V. cholerae induced an innate immune response at the acute stage of disease characterized by increased expression of hBD-2, and continued expression of hBD-1, HD-5-6, and LL-37.     

Submicroscopic features of cecal cells in experimental Escherichia infection]

Ultrastructural changes of the caecum cells were studied for the period from 15 minutes to 2 weeks after inoculation using the model of experimental escherichiosis. Evolution processes in relation to different caecum cell populations were followed up submicroscopically. Ultrastructural changes observed evidence derangement of protein and water-salt cell metabolism, immune trends of experimental escherichiosis.     

Lipid droplet dynamics at early stages of Mycobacterium marinum infection in Dictyostelium

Lipid droplets exist in virtually every cell type, ranging not only from mammals to plants, but also to eukaryotic and prokaryotic unicellular organisms such as Dictyostelium and bacteria. They serve among other roles as energy reservoir that cells consume in times of starvation. Mycobacteria and some other intracellular pathogens hijack these organelles as a nutrient source and to build up their own lipid inclusions. The mechanisms by which host lipid droplets are captured by the pathogenic bacteria are extremely poorly understood. Using the powerful Dictyostelium discoideum/Mycobacterium marinum infection model, we observed that, immediately after their uptake, lipid droplets translocate to the vicinity of the vacuole containing live but not dead mycobacteria. Induction of lipid droplets in Dictyostelium prior to infection resulted in a vast accumulation of neutral lipids and sterols inside the bacterium‐containing compartment. Subsequently, under these conditions, mycobacteria accumulated much larger lipid inclusions. Strikingly, the Dictyostelium homologue of perilipin and the murine perilipin 2 surrounded bacteria that had escaped to the cytosol of Dictyostelium or microglial BV‐2 cells respectively. Moreover, bacterial growth was inhibited in Dictyostelium plnA knockout cells. In summary, our results provide evidence that mycobacteria actively manipulate the lipid metabolism of the host from very early infection stages.     

Ultrastructural changes in rectal mucosa cells in experimental Escherichia infection

Ultrastructural changes of rectum epitheliocytes and cells of lamina propria were studied at the period from 15 minutes to 2 days after inoculation using the model of experimental escherichiosis. The results obtained allow to determine the correlation of ultrastructural changes and the data of morphometric analysis. Ultrastructural peculiarities were determined of the rectum cells and the different cell populations were studied during infection's process.     

Ultrastructure of surface epithelial cells of the normal human rectum

Luminal surface epithelial cells, excluding a few endocrine cells of the normal human rectum, were studied electron microscopically and 5 types of cells were recognized with special reference to some structure containing mucous substances. Principal-1 cells showing few tiny vesicles and Principal-2 cells containing some tiny vesicles seemed to belong to the absorptive cell group. Vesicle cells having numerous tiny vesicles, and Columnar mucous cells accompanied by numerous tiny vesicles and some round or oval mucous vacuoles, seemed to be labelled as of the secretory cell group. The common features of the epithelial columnar cells, except for the Goblet cell, were columnar shape, microvilli whose length and density had considerable variation, glycocalyceal bodies around the microvilli, and thick surface coat. Goblet cells were characterized by a goblet shape which was expanded by numerous mucous droplets. It is of special interest that 4 different types of columnar epithelial cells are recognized on the luminal surface of the normal human rectum, and that Vesicle cells and Columnar mucous cells are first observed on the luminal surface of the large intestine. Similar epithelial cells have only been reported in the crypt of the large intestine and not on the luminal surface.     

Morphological characteristics of endocrine cells of the intestine in experimental Escherichia infection]

Ultrastructural investigation and quantitative analysis of endocrine cells of intestine were studied at the period from 15 minutes to 24 hours after inoculation using the model of experimental esherichiosis. The results obtained allow to determine the succession of changes of different types of endocrine cells in dependence on localization and duration of influence.