Characterisation of verocytotoxin-producing Escherichia coli isolated from pigs and cattle in northern Italy.
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Animals↗
Biomedical subjects
G Donelli
Publications and source records attributed to G Donelli.
N-acetylcysteine inhibits apoptosis and decreases viral particles in HIV-chronically infected U937 cells.
Apoptosis or programmed cell death (PCD) is a type of death occurring in various physiological processes. Several data suggest that: (1) apoptosis may play a critical role in AIDS pathogenesis; (2) an increase of endocellular free radical levels can be associated with activation of previously latent HIV virus. Tumor necrosis factor (TNF), a cytokine capable of inducing oxygen free radicals and apoptosis, appears also to be involved in HIV activation. The present findings, which elucidate a relationship between the percentage of apoptotic cells, reduced glutathione (GSH) depletion and an increase of p24 antigenemia, suggest that pretreatment with N-acetylcysteine (NAC) is capable of decreasing the above-mentioned phenomena in HIV-infected U937 cells.
Acetylcysteine↗
A new, striking morphologic feature for the human erythrocyte in hereditary spherocytosis: the blebbing pattern.
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Erythrocyte Membrane↗
A 50-Hz magnetic field induces structural and biophysical changes in membranes.
The effects of a 50-Hz extremely low frequency magnetic field on cultured K562 cells growing in suspension were studied by means of scanning electron microscopy and electron paramagnetic resonance spectroscopy. Exposure of K562 cells at 2.5 mT for periods to 96 hours induced significant changes in cell-surface structure and physiology without modification of proliferative capability as indicated by quantitative analysis. Thus extremely low frequency fields seem able to induce injurious, sublethal cell alterations, and the plasma membrane seems to play an important role in this effect.
Cell Division↗
Variable fixation of staphylococcal slime by different histochemical fixatives.
A variety of histochemical fixatives were used to compare the fixation of bacterial films produced by a standard slime-producing strain of Staphylococcus epidermidis on plastic tissue culture plates. Some reagents were completely ineffective in fixing the slime layer, whereas others gave variable results. The best alternative to the fixative of the reference method, the potentially explosive Bouin's reagent, was air drying.
Bacteriological Techniques↗
Effect of polyions on the infectivity of SA-11 rotavirus in LCC-MK2 cells.
We investigated the effect of different polyions on the early phases of SA-11 rotavirus infection in susceptible LLC-MK2 cells in order to clarify the influence of electrostatic interactions in rotavirus binding to cell membranes and to select antiviral compounds able to prevent viral attachment. When added during the viral attachment step, polymers having positive charge (protamine, protamine sulphate, DEAE-dextran, histone and poly-L-lysine hydrobromide) enhanced virus infection whereas those having negative charge (mucin, heparin, heparan sulphate, alpha-1-acid glycoprotein and dextran sulphate) inhibited the viral replication. The effect of polyanions on SA-11 rotavirus and on cell membrane receptors has also been examined. Results obtained indicated that while mucin and alpha-1-acid glycoprotein act directly on virus particles, the target of heparin, heparan sulphate and dextran sulphate is the host cell membrane.
Adsorption↗
Induction of phagocytic behaviour in human epithelial cells by Escherichia coli cytotoxic necrotizing factor type 1.
Cytotoxic necrotizing factor type 1 (CNF1) from strains of pathogenic Escherichia coli induces in human epithelial HEp-2 cells, a profound reorganization of the actin cytoskeleton into prominent stress fibres and membrane ruffles. We report here that this process is associated with induction of phagocytic-like activity. CNF1-treated cells acquired the ability to ingest latex beads as well as non-invasive bacteria such as Listeria innocua, which were taken as a model system. Uptake of bacteria was similar to pathogen-induced phagocytosis, since L. innocua transformed with DNA coding for the pore-forming toxin listeriolysin O behaved, with respect to intracellular growth, like the invasive, pathogenic species L. monocytogenes. Our results raise the possibility that, in vivo, pathogenic CNF1-producing E. coli may invade epithelia by this novel induced phagocytic-like mechanism.
Actin Cytoskeleton↗
Clostridium difficile toxin A elicits Ca(2+)-independent cytotoxic effects in cultured normal rat intestinal crypt cells.
In rat intestinal crypt cells, Clostridium difficile toxin A induces (i) early cytoskeletal alterations involving the whole population and (ii) late effects in 30 to 40% of the cells, consisting mainly of surface blebbing and nuclear fragmentation. All these effects were Ca2+ independent and were not abolished by protein synthesis inhibitors.
Animals↗
Interaction of Escherichia coli cytotoxic necrotizing factor type 1 (CNF1) with cultured cells.
The cytotoxic necrotizing factor type 1 (CNF1) from E. coli causes necrosis in rabbit skin and multinucleation in cultured cells. Cells exposed to CNF1 were characterized by changes in actin organization, mainly consisting in the presence of well-developed stress fibers and membrane ruffles. The interaction of CNF1 with the cell cytoskeleton probably promotes the cell spreading and interferes with the cytokinesis, leading to the formation of giant multinucleated cells.
Actins↗
Viral childhood diarrhoea in Rome: a diagnostic and epidemiological study.
During the period May 1987-January 1989, faecal samples from 417 paediatric inpatients admitted to the main paediatric hospital in Rome were screened by direct electron microscopy and rotavirus enzyme-linked immunosorbent assay. Rotaviruses were detected in 18.2% of cases and adenoviruses in 7%, whereas astroviruses were found in 1% of cases. Different percentages of rotavirus excretors were revealed by enzyme-linked immunosorbent assay and electron microscopy. This discrepancy seems to be due to false positive results introduced by enzyme-linked immunosorbent assay. Analysis of electron microscopy-positive samples by rotaviral RNA polyacrylamide gel electrophoresis showed different electropherotypes of rotavirus among which a single, largely predominant long electropherotype (55.4%) was revealed. Short electropherotype subgroup I rotaviruses were demonstrated in about 10.7% of samples.
Adenovirus Infections, Human↗
Ultrastructure analysis of Tenckhoff chronic peritoneal catheters used in continuous ambulatory peritoneal dialysis patients.
The luminal and external surfaces of 18 curled silicone double-cuff catheters removed from patients who had been on continuous ambulatory peritoneal dialysis (CAPD) for 2-77 months (average 37 +/- 21 months) were analyzed by scanning electron microscopy (SEM) and microbiological cultures. Eight catheters (G1) were removed due to recurrent peritonitis or peritonitis refractory to antibiotic management, and the others (G2) due to local or clinical problems. The peritonitis rate was one episode every 24 patient-months in G1, and 80 patient-months in G2. All catheter surfaces were covered with proteinlike granular deposits (0.15 +/- 0.11/cm); 6 catheters were covered by microbial biofilm (0.24 +/- 0.16/cm). Positive cultures of catheter segments were obtained in 6 cases (4 for G1 and 2 for G2) with a preponderance (33%) of Staphylococcus aureus among the cultivated bacteria. Structural defects and small linear tears were present on both luminal and external surfaces in 8 catheters. Structural defects were frequent in the catheters removed for recurrent peritonitis. Linear tears appeared more frequently in the catheters used for a longer time. Structural defects of catheter surfaces were also discovered in the newer devices. The structural defects of the catheter appear to facilitate microbial adhesion and colonization and to predispose the patient to recurrence of peritonitis. A better catheter design and an improvement in the production process should therefore be recommended.
Bacteria↗
Cell death. General features and morphological aspects.
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Antigens, Surface↗
Mechanism of astrovirus entry into Graham 293 cells.
Astroviruses are intestinal pathogens associated with gastroenteritis in man and animals. The mechanism of internalization into host cells has not been reported previously. The cell entry pathway of serotype 1 human astrovirus into 293 cell line was studied biochemically and morphologically. Viral infection was monitored by indirect immunofluorescence. Infected cells were treated with the lysosomotropic agents ammonium chloride, methylamine, and dansylcadaverine or the ionophore monensin to raise the intraendosomal and intralysosomal pH. All drugs tested inhibited the early stages of infection whereas they did not interfere with the viral binding to the plasma membrane. The presence of astrovirus particles was detected by electron microscopy in coated pits and later in coated vesicles. The data indicate adsorptive endocytosis as the most probable mechanism by which astroviruses enter susceptible cells.
Ammonium Chloride↗
Cell injury and death caused by bacterial protein toxins.
Bacterial protein toxins, such as Clostridium difficile toxin A and the Escherichia coli cytotoxic necrotizing factor 1 are known to exert their cytotoxic action via a modification of some cytoskeletal components. The changes in actin organization caused by these toxins appear to be the primary events in the mechanism leading to cell death.
Actins↗
Laboratory diagnosis of rotavirus infection in diarrhoeal patients by immunoenzymatic and latex-agglutination assays.
One hundred stool samples from children with acute diarrhoea were examined by six commercial latex and immunoenzymatic assays for the diagnosis of rotavirus infection in four different laboratories. Samples were also analyzed by solid-phase immune electron microscopy using a rabbit anti-group A rotavirus antiserum. With electron microscopy as a basis for comparison, sensitivity and specificity for the latex and ELISA assays varied from 91.1 to 92.9% and from 94.2 to 99.4%, respectively. Statistically significant differences were revealed in the confirmation rate of electron microscopy-negative samples between different commercial assays. Significant variability was also found between results obtained by the laboratories taking part in the study.
Antigens, Viral↗
Increased reactivity of laminin in the basement membranes of capillary walls in AIDS brain cortex.
To verify how the components of the capillary wall are modified in the course of AIDS we studied the brain cortex from nine cases with AIDS. Cellular and extracellular components were delineated using antibodies for laminin and collagen IV for basement membranes and glial fibrillary acidic protein for astrocyte foot processes. We found a marked increase in reactivity for laminin in the basement membranes of capillary walls and hypertrophy and hyperplasia of astrocyte foot processes around vessels, when compared to control cortical tissue. We suggest that modifications of brain capillary wall may have a role in the pathogenesis of neurological disfunction in AIDS.
Acquired Immunodeficiency Syndrome↗
HT-29 cells: a new substrate for rotavirus growth.
Susceptibilities of a continuous rhesus monkey kidney cell line (MA-104) and that of a human colon carcinoma cell line (HT-29) to infection by different human and animal rotavirus strains were compared. HT-29 cells appeared to be more sensitive to human rotavirus infection than MA-104 cells, whereas the latter cell line was more susceptible to animal rotavirus replication. The greater sensitivity to human rotavirus infection of HT-29 cells was confirmed by the successful, direct isolation of these viruses from faecal specimens. Human rotavirus infection of HT-29 cells was also followed by transmission electron microscopy. In ultra-thin sections, unenveloped particles of rotaviruses, representing infectious mature virions, were observed in large number. Moreover, many "double-shelled" particles were detected in negative-stained supernatants from infected cultures. Scanning electron microscopy of uninfected HT-29 cells showed that in the presence of Ca++, required for rotavirus growth, they are able to express some of the features of mature intestinal cells. In view of these results, HT-29 cells appear to be a useful in vitro model for the study of rotavirus infection.
Animals↗
Cell membranes as target for anticancer agents.
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Antineoplastic Agents↗