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Biomedical subjects

G Donelli

Publications and source records attributed to G Donelli.

At least 19 recordsLinked to original sources
PubMed1995

Enhancement of rotavirus infectivity by saturated fatty acids.

The effect of different saturated fatty acids from 10 to 16 carbon atom chains and some derivatives on the infectivity of SA-11 rotavirus was examined. Both fatty acids and derivatives induced an increase of rotavirus infected LLC-MK2 cells when present during viral absorption to host cells. Capric acid and palmitic acid were the most effective with a dose-dependent relationship. These last lipids, in the same experimental conditions, failed to restore the susceptibility to infection of LLC-MK2 cells made resistant by neuraminidase treatment or to allow cell infection by non-infectious single-shelled viral particles. Results obtained suggest that the enhancing effect on viral infectivity by saturated fatty acids requires previous binding of rotaviral outer capsid proteins to sialic acid containing cell receptors.

Animals↗
PubMed1995

Vitamin E prevents UVB-induced cell blebbing and cell death in A431 epidermoid cells.

Cultured A431 epidermoid cells exposed to UVB (120-2400 J/m2) develop numerous blebs on their surface, detach from the plastic dish, and undergo injury and death. Numerous detached cells display fragmented nuclei, typical of apoptotic cells. Since bleb formation also occurs after oxidative stress it was assumed that the morphological variations observed are the consequence of free radical-mediated insult. In order to test this hypothesis, the antioxidant alpha-tocopherol (vitamin E) was added to cell cultures at different times, before or after irradiation. The results indicate that vitamin E inhibits UVB-induced surface blebbing as well as cell detachment from the substrate. Moreover, vitamin E is most effective in stimulating cell recovery when it is added after the end of UVB irradiation. Finally, vitamin E treatment also seems to reduce the fraction of cells undergoing death (probably those which will undergo apoptosis) after exposure to UVB radiation.

Antioxidants↗
PubMed1995

Transmembrane P-glycoprotein (P-gp/P-170) in HIV infection: analysis of lymphocyte surface expression and drug-unrelated function.

P-glycoprotein (P-gp/P-170), a transmembrane efflux pump known to be one of the mechanisms responsible for multidrug resistance in cancer therapy, is constitutively expressed in several solid human tissues as well as in normal peripheral blood lymphocytes and bone marrow cells. In particular, this molecule has been associated with the transport of perforin and other cytolysins in natural killer (NK) and T cytotoxic lymphocytes. In the present study, we analyzed peripheral blood lymphocytes (PBLs) from controls and HIV+ patients for phenotypic expression and function of the P-gp/P-170 molecule. We found that 90% of all PBL subsets (i.e., CD4+, CD8+, CD56+, and CD19+ cells) expressed surface P-gp/P-170 both in controls and HIV+ patients. However, a significant decrease in CD4+/P-170+ and CD19+/P-170+ cells was observed in HIV+ individuals with respect to controls. PHA and IL-2 stimulation of PBLs was unable to increase the expression of P-gp/P-170 both in controls and HIV+ patients, despite the increased detection of the CD25 molecule. On the other hand, stimulation with anti-CD3 determined a significant increase in lymphocyte P-gp/P-170. The function of P-gp/P-170, assessed by a flow cytometric assay for rhodamine-123 (Rh123) efflux, was significantly reduced in CD16+ NK cells and CD19+ B cells from HIV+ patients. The Rh123 efflux by NK cells correlated (p < 0.01) with the NK cytotoxicity against the 51Cr-labeled K562 cell line. Last, the effect of the antiretroviral drugs AZT, ddI, and ddC on P-gp expression and function was evaluated. The dideoxynucleoside compounds did not inhibit P-gp/P-170 function of normal mononuclear cells in vitro, and did not increase P-gp/P-170 expression in vivo, in patients undergoing antiretroviral therapy with AZT. These findings provide further evidence of a possible involvement of the P-gp/P-170 system in specific immunological lymphocyte functions, and especially in cytotoxic-type functions. In addition, it is possible to suggest, on the basis of our experimental data, that the dideoxynucleoside class of antiretroviral agents does not contribute to the phenotypic and functional alterations related to P-glycoprotein during HIV infection.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Escherichia coli cytotoxic necrotizing factor 1: evidence for induction of actin assembly by constitutive activation of the p21 Rho GTPase.

Cytotoxic necrotizing factor type 1 (CNF1) induces in HEp-2 cells an increase in F-actin structures, which was detectable by fluorescence-activated cell sorter analysis 24 h after addition of this factor to the culture medium. Increase in F-actin was correlated with the augmentation of both the cell volume and the total cell actin content. Actin assembly-disassembly is controlled by small GTP-binding proteins of the Rho family, which have been reported recently to be modified by CNF1 treatment. Clostridium difficile toxin B and Clostridium botulinum exoenzyme C3, both known to act on the Rho GTPase, were used as biological tools to study the effect of CNF1 on this protein. CNF1 incubated before, during, or after exposure to the chimeric toxin C3B (which is the product of a genetic fusion between the DNA coding for C3 and the one coding for the B fragment of diphtheria toxin) protected HEp-2 cells from the disruption of F-actin structures caused by inactivation of the Rho GTPase through its ADP-ribosylation. On the other hand, C. difficile toxin B cytopathic effect was not observed upon preincubation of cells with CNF1. Toxins acting through a Rho-independent mechanism, such as cytochalasin D and Clostridium spiroforme iota-like toxin, could not be modified in their cellular activities by CNF1 treatment. All of our results suggest that CNF1 modifies the Rho molecule, thus probably protecting this GTPase from further bacterial toxin modification.

ADP Ribose Transferases↗
PubMed1995

Zonula occludens toxin modulates tight junctions through protein kinase C-dependent actin reorganization, in vitro.

The intracellular signaling involved in the mechanism of action of zonula occludens toxin (ZOT) was studied using several in vitro and ex vivo models. ZOT showed a selective effect among various cell lines tested, suggesting that it may interact with a specific receptor, whose surface expression on various cells differs. When tested in IEC6 cell monolayers, ZOT-containing supernatants induced a redistribution of the F-actin cytoskeleton. Similar results were obtained with rabbit ileal mucosa, where the reorganization of F-actin paralleled the increase in tissue permeability. In endothelial cells, the cytoskeletal rearrangement involved a decrease of the soluble G-actin pool (-27%) and a reciprocal increase in the filamentous F-actin pool (+22%). This actin polymerization was time- and dose-dependent, and was reversible. Pretreatment with a specific protein kinase C inhibitor, CGP41251, completely abolished the ZOT effects on both tissue permeability and actin polymerization. In IEC6 cells ZOT induced a peak increment of the PKC-alpha isoform after 3 min incubation. Taken together, these results suggest that ZOT activates a complex intracellular cascade of events that regulate tight junction permeability, probably mimicking the effect of physiologic modulator(s) of epithelial barrier function.

Actins↗
PubMed1994

Both UVA and UVB induce cytoskeleton-dependent surface blebbing in epidermoid cells.

Data on the morphological changes induced by UVA or UVB irradiation of A431 epidermoid cells in culture are presented. After irradiation with different doses of UVB (120-2400 J m-2) or UVA (10(4)-10(5) J m-2), the membrane and cytoskeleton of these cells were analysed by immunofluorescence and scanning electron microscopy at different times after exposure (0-48 h). Both UVA and UVB alter microtubules and microfilaments and surface blebs are formed after UV irradiation. In particular, UVB induces multiple small blebs on the cells, while UVA induces one single large bleb on each cell. Since cytoskeletal damage and surface blebbing of this type are also induced by oxidative stress, these results add to the body of evidence indicating that UV radiation is capable of pro-oxidant behaviour. Specifically, the morphological changes described in this paper are reminiscent of the modifications which accompany epidermal keratinocytes during their transformation to sunburn cells after UV irradiation. The physiological implications of these findings are discussed.

Actins↗
PubMed1994

Detection of enteroadherent Escherichia coli associated with diarrhoea in Italy.

One hundred and sixty-eight isolates of Escherichia coli obtained in Italy from 112 children with diarrhoea and 56 age-matched controls were examined by the HEp-2 cell adhesion assay. Sixteen strains showed localised adherence (LA), 29 showed diffuse adherence (DA) and eight strains showed aggregative adherence (AA). No adhesion pattern was significantly associated with disease. Strains that showed LA or AA were further characterised by serotyping, fluorescent actin staining (FAS) test and hybridisation with the EPEC adherence factor (EAF), E. coli attaching and effacing (eae) and enteroaggregative (EAgg) DNA probes. Strains that showed poor LA were FAS-negative, did not belong to EPEC serotypes and did not hybridise with EPEC probes. Conversely, the two strains that showed a good LA pattern belonged to serotype O128:H2, were FAS positive and hybridised with the eae probe. No isolate hybridised with the EAF probe. Only three of the eight strains with the AA pattern hybridised with the EAgg probe. Probe positivity correlated with the ability to produce clumps at the surface of the liquid culture and to agglutinate rat erythrocytes. In two of these EAgg probe-positive strains, electronmicroscopy revealed the presence of fibrillar bundles which seem to mediate bacterial aggregation.

Bacterial Adhesion↗
PubMed1994

Influence of particle size and chemical composition on efficiency of clearance mechanisms: electron microscopy studies on humans.

This article compares the presence of solid particles in lung parenchyma samples collected from accident victims and in bronchoalveolar lavage fluid taken from patients diagnosed with pulmonary carcinoma. Analysis by electron microscopy showed differences in particle size between the two groups, which could be attributable both to differences in original particle size and to their solubility in the biological environment.

Bronchoalveolar Lavage Fluid↗
PubMed1994

[Infections associated with intra- and extravascular catheters: factors involved in microorganism-biomaterial interactions].

Infections is one of the most common cause of catheter failure as well as the most difficult to manage, most often requiring catheter removal. Staphylococcus is the etiologic agent of such infections more frequently isolated, particularly Staphylococcus epidermidis. Several factors have been suggested to be involved in bacteria-biomaterial interactions such as catheter surface morphology, molecular biofilm and bacterial virulence features. Different strategies have been tried to avoid the development to catheter-associated infections: among them adsorption of antibiotic molecules to the catheter surface might represent a successful tool to improve catheter implant life.

Bacterial Adhesion↗
PubMed1994

Bacterial protein toxins acting on the cell cytoskeleton.

A number of bacterial protein toxins are known to exert their cytotoxic activity via a modification of cytoskeletal components. Some toxins induce the ADP-ribosylation of actin whereas others interact with the cytoskeleton by an unknown mechanism. Understanding the mode of action of such toxins at cellular level could provide useful information on their role in vivo as virulence factors.

Actin Cytoskeleton↗
PubMed1994

Rotavirus and poliovirus co-infection in HT-29 cells.

The effect of a mixed poliovirus-rotavirus infection in HT-29 cells, a gut tumour derived cell line highly susceptible to both viruses, has been analyzed. The obtained results showed an increase of poliovirus multiplication in cells super-infected or co-infected with rotavirus, whereas the pre-infection with poliovirus had an interfering effect on rotavirus replication.

Antigens, Viral↗
PubMed1994

Oral immunoglobulins for treatment of acute rotaviral gastroenteritis.

OBJECTIVE: Preliminary evidence has been reported on the antirotavirus effect of human serum immunoglobulin administered orally. The aim was to see whether such treatment might be effective in rotavirus acute gastroenteritis. METHODS: A prospective, double-blind, placebo-controlled study was performed. Ninety-eight children admitted with acute gastroenteritis were enrolled and randomly assigned to groups A (treated) and B (control). Children in group A received a single oral dose of 300 mg/kg body weight of human serum immunoglobulin. Parameters of efficacy were clinical condition, frequency and consistency of stools, duration of diarrhea, duration of viral excretion, and length of hospital stay. Antirotaviral activity was determined in the immunoglobulin preparation by a specific neutralization assay. RESULTS: Seventy-one of the 98 children enrolled had rotaviral gastroenteritis; 36 belonged to group A. Children who received immunoglobulin had significantly faster clinical improvement of clinical condition and stool pattern than control children. Mean total duration of rotaviral diarrhea was 76 hours in group A and 131 in group B (P < .01). Viral excretion lasted 114 and 180 hours, respectively (P < .01). Hospital stay was significantly reduced in children in group A. Neutralizing antibodies against rotavirus were detected in the immunoglobulin preparation. CONCLUSION: Oral administration of immunoglobulin is associated with a faster recovery from acute gastroenteritis and should be given to children hospitalized with this illness.

Acute Disease↗
PubMed1993

Down-modulation of CD4 antigen during programmed cell death in U937 cells.

It has been hypothesized that programmed cell death (PCD), an active cell suicide process occurring in place of necrosis, can be associated with the pathogenesis of acquired immunodeficiency syndrome (AIDS). The entry of human immunodeficiency virus (HIV) into competent cells is mediated by the CD4 molecule present on the surface of certain lymphocyte subpopulations as well as on some cultured cell lines, e.g. U937 myelomonocytic cells. The present paper focuses on some specific aspects of PCD induced by the cytokine tumor necrosis factor (TNF). The results obtained indicate that the exposure of U937 cells to cycloheximide facilitates TNF-mediated PCD via a short term cell death program and modifies the expression of CD4 surface molecules. This change in surface antigen expression, manifested by internalization of the CD4 molecule, occurs in cells in which apoptosis has been triggered, but not in cells undergoing necrosis. These results indicate that the progression of cell death could be associated with specific alterations of certain surface molecules and could have a role in the entry of HIV into cells.

Apoptosis↗
PubMed1993

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↗
PubMed1993

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↗
PubMed1993

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↗
PubMed1993

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↗