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Biomedical subjects

N Orsi

Publications and source records attributed to N Orsi.

At least 55 records · Page 3Linked to original sources
PubMed1991

Role of membrane phospholipids and glycolipids in cell-to-cell fusion by VSV.

To identify membrane components of CER cells interacting with vesicular stomatitis virus (VSV) during fusion at acidic pH (fusion from without, FFWO) two different approaches have been used, i.e. (i) treating the whole cells with enzymes and (ii) testing the ability of isolated membrane molecules to interfere with FFWO. Phospholipase A2 and C digestion of cells greatly reduced syncytia formation, pointing towards the involvement of lipid structures as target sites for VSV. Cell susceptibility to FFWO was also reduced after neuraminidase, beta-galactosidase or periodate treatment, suggesting that carbohydrate residues may participate in a complex receptor structure required for virus fusion. When membrane molecules were examined separately for their ability to inhibit viral FFWO, phosphatidylserine, phosphatidylinositol, sphingomyelin, cholesterol and GM3 ganglioside were found to be active, confirming the role of membrane lipid moiety in the cell surface structures involved in the early phases of VSV infection.

Cell Fusion↗
PubMed1991

Epidemiological typing of uropathogenic Pseudomonas aeruginosa strains from hospitalized patients.

One hundred and twenty-one clinical isolates of Pseudomonas aeruginosa from patients with hospital-acquired urinary tract infections (UTIs) were studied to determine their major epidemiological markers, including API 20NE profile, O-serotype, pyocin type, phage type, lysogenic state and antibiotic susceptibility. Serotypes O4, O12, O11, O6 and O5 were found with a high frequency, accounting respectively for 23.9%, 23.1%, 12.3%, 8.2% and 5.7% of isolates. Pyocin type 10 was most common (32.2%) followed by types 1 (10.7%), 33 (7.5%) and 105 (4.1%); subtype h was predominant being characteristic of 34.7% of isolates. Most of the strains (69.4%) were either not phage typable or sensitive to phages 68 and 119x. Resistance to gentamicin, tobramycin, amikacin, imipenem and ciprofloxacin was more frequent among strains belonging to serotype O12. The O-serotypes were combined with API 20NE profiles, pyocin and phage types, lysogenic states and antibiotic resistance in order to identify epidemiologically related clones. Within predominant serotypes--O4 and O12--most strains displayed similar but not identical type characteristics, whereas other serotypes were less homogeneous. Our results support the concept that a combination of current typing techniques allows the identification of epidemiologically related P. aeruginosa isolates.

Bacterial Typing Techniques↗
PubMed1991

Influence of polyions on the early steps of enterovirus infection.

The influence of electric charged molecules on the early phases of enterovirus infection was studied in order to select antiviral compounds able to prevent viral attachment. The effect of different polyelectrolytes on the multiplication of coxsackie virus B3, echovirus 6 and hepatitis A virus was investigated in susceptible cells by adding the drug before, during or after the viral adsorption period. Among polyanions, the polysaccharides heparin and dextran sulfate inhibited viral infectivity, dextran sulfate being the most effective mainly towards hepatitis A virus infection. DEAE-dextran and protamine sulfate, generally recognized as enhancers of infectivity of naked and enveloped viruses, exhibited an inhibitory effect towards the three picornaviruses tested. Only in the case of hepatitis A did DEAE-dextran slightly improve viral antigen synthesis. The inhibitory effect shown by compounds belonging to positive and negative polyions suggests that the electric charge is not sufficient by itself to explain the antiviral activity of these drugs.

Animals↗
PubMed1991

Antiviral activity of constituents of Tamus communis.

The antiviral activity of the phenanthrene derivatives 1-6, of the spyrostane triglycosides dioscin (7) and gracillin (8), of the furostanol tetraglycosides methylprotodioscin (9), its (25S) epimer methylprotoneodioscin (10), and methylprotogracillin 11, have been tested towards two RNA viruses: vesicular stomatitis virus and human rhinovirus type 1B. All these products were extracted from the rizomes of Tamus communis L; compound 11 was isolated also from Asparagus cochinchinesis, together with pseudoprotodioscin (12), a 20 (22)-unsaturated furostanoside, which was also investigated for antiviral activity. The results were of some interest mainly for the phenanthrene derivatives.

Animals↗
PubMed1991

Growth of Legionella spp. under conditions of iron restriction.

The growth inhibiting activity of transferrins, citrate, 2-2' dipyridyl and desferrioxamine methanesulphonate towards Legionella spp. and their serogroups was investigated. The inhibitory activity of all these compounds depended upon the iron-free state of the molecules and was abolished by saturation with iron. No bactericidal effect by transferrins was observed at concentrations up to four times the minimal bacteriostatic concentration. No interaction of transferrins with the legionella cell surface was detected by direct or indirect fluorescence assay, or by dialysis culture experiments in which transferrin was separated from the bacterial cells. The demonstration of a siderophore-like activity in supernates of iron-deficient legionella cultures may account for the ability of Legionella spp. to multiply in conditions of iron restriction.

2,2'-Dipyridyl↗
PubMed1991

Human serum non-antibody inhibitors towards SA-11 rotavirus hemagglutination.

In the present work the non-antibody inhibitory activity of human serum towards SA-11 rotavirus hemagglutination (HA) has been studied. Among human serum protein components, inhibitory activity was recovered in fractions III (beta-globulin), IV (alpha-globulin) and IV (glycoprotein). Additional experiments performed with purified lipoprotein sub-classes and their lipid and apolipoprotein moieties demonstrated the ability of HDL and, HDL1 to prevent SA-11 HA.

Animals↗
PubMed1990

Role of membrane phospholipids and glycolipids in the Vero cell surface receptor for rubella virus.

Membrane receptors for rubella virus (RV) in Vero cells were studied by means of two different approaches: (i) by enzyme treatment of the whole cell membrane and (ii) by testing the ability of isolated plasma membrane molecules to compete with cells for virus binding. The replication of RV was studied with both indirect immunofluorescence assay and molecular hybridization techniques. Phospholipases A2 and C digestion of cells greatly reduced the infectivity by the virus, pointing towards the involvement of lipid structures as receptor sites for RV. Furthermore, susceptibility of Vero cells to virus infection was also reduced after beta-N-acetyl-D-glucosaminidase, alpha-glucosidase and beta-galactosidase treatment, suggesting that carbohydrate residues may participate in a complex cellular receptor structure for RV. When the major membrane lipids were examined separately for their ability to inhibit viral infectivity, several phospholipids (phosphatidylserine, phosphatidylinositol, phosphatidylethanolamine, phosphatidylcholine, sphingomyelin) and glycolipids (gangliosides, lactosylceramide, cerebroside sulphate) showed a strong neutralizing activity, confirming the role of membrane lipid moiety in the cell surface receptor for RV.

Animals↗
PubMed1990

Effect of inhibitors of cytoplasmic structures and functions on rabies virus infection in vitro.

The effect in vitro of some cytoplasmic structure and function inhibitors on the different stages of rabies virus infection was investigated. Treatment of fibroblasts (CER) and human neuroblastoma cells (IMR-32) with substances acting on low pH intracellular compartments (methylamine and monensin) prevented rabies virus genome delivery in the cytosol. An early inhibition of viral infection was also obtained in the presence of B and D cytochalasins and trifluoperazine which interact with microfilament structures. Treatment with colchicine and vinblastine did not affect rabies multiplication, suggesting that microtubules are not involved in this process. However, the multiplication of prebound virions did not take place in the presence of inhibitors of oxidative phosphorylation (sodium azide and CCCP) and of glycolysis (2-deoxy-D-glucose) indicating that rabies virus replication is largely energy-dependent in both host cells examined.

Animals↗
PubMed1990

In vitro effect of synthetic flavanoids on astrovirus infection.

In this study we investigated the activity of halogeno-, cyano- and amidino-isoflavenes, isoflavans and flavans on the multiplication of human astroviruses. These are naked small round viruses which have been recognized as causative agents of human gastroenteritis, and whose capsid proteins are similar to those of picornaviruses. Although all drugs tested caused a dose-dependent reduction of viral antigen synthesis as monitored by immunofluorescence, the chloro derivatives were the most effective.

Animals↗
PubMed1990

Activities and mechanisms of action of halogen-substituted flavanoids against poliovirus type 2 infection in vitro.

The effects of some halogen-substituted flavanoids (dichloroflavan, halogenated isoflavans, and isoflavenes) on poliovirus type 2 infection was examined. Only two isoflavenes exhibited a significant inhibitory activity on the virus-induced cytopathic effect and plaque formation. In a single cycle of viral replication, both compounds reduced the viral yield by approximately 90%. The presence of the isoflavenes from the beginning of infection or during the adsorption period only prevented the shutoff of host translation and viral RNA and protein synthesis, suggesting that the drugs blocked an early step of viral replication. Indeed, both isoflavenes were not virucidal, did not protect virus infectivity from heat inactivation, and had no measurable effect on the binding of virus to cells, viral penetration, and uncoating of the viral RNA. In contrast, both compounds significantly reduced the infectivity of free viral RNA. The possibility that compounds interfere with poliovirus replication at a very early stage of translation of the input RNA is discussed.

Flavonoids↗
PubMed1990

Effect of desferrioxamine B, a metal chelating agent, on rhabdovirus multiplication.

It has been suggested that the antiviral activity shown by chelating agents towards different viruses is probably related to the action on viral nucleic acid polymerases which require metal ions as essential cofactors. Desferrioxamine B, a metabolite from Streptomyces pilosus which chelates ions (Fe3+, Al3+, Cu2+, Zn2+, Co2+) from intracellular and external compartments, has been tested for its activity on the multiplication of VSV and rabies virus in CER cells. While desferrioxamine B was ineffective on rabies virus multiplication, it was shown to reduce plaque formation, cytopathic effect and viral yield by VSV at both low and high multiplicity of infection. The activity of the drug was not due to a direct action on virions outside the cells, but was probably related to an alteration in the delicate balance of intracellular ions which could in turn be critical for VSV multiplication.

Animals↗
PubMed1990

Susceptibility of mammalian, avian, fish, and mosquito cell lines to rabies virus infection.

The relationship between plasma membrane receptor organization and cell susceptibility in vitro was investigated in mammalian, avian, fish, and arthropod cell lines infected with fixed rabies virus. IMR32, HeLa, CER, and EPC cells were widely susceptible to infection with CVS virus, whereas a lower level of specific viral antigens was detectable in A. albopictus cells. In spite of these differences, the amount of infectious virus particles bound to the various cell surfaces was similar. Competition experiments carried out with plasma membranes extracted from ability of these components to bind the virus and to prevent infection. The different cellular permissiveness to rabies infection described here did not correlate with significant differences in number or in chemical structure of the receptor binding sites, but more likely with events following virus adsorption.

Adsorption↗
PubMed1990

Role of membrane glycosphingolipids as Pseudomonas aeruginosa adhesin receptor in rabbit bladder mucosa.

The adhesiveness of a mucous strain of Pseudomonas aeruginosa to rabbit bladder mucosa was studied after preincubation of the microorganism with several glycolipids with different carbohydrate moieties to investigate their importance in the interaction with bacterial adhesins. Vesical cells were also treated with lectins (limulin and soybean) to confirm the role of saccharides as membrane receptor. The results obtained showed that galactose-containing glycolipids were able, in varying degrees, to reduce bacterial binding. The most active compounds were glycosphingolipids with negatively charged terminal groups. Lectin treatment of bladder mucosal cells confirmed the importance of galactose and sialic acid as mucosal cell membrane receptors for P. aeruginosa.

Adhesins, Bacterial↗
PubMed1989

Effect of cellular function inhibitors on the infection of Frp/3 cells by hepatitis A virus.

The effect of some cellular function inhibitors on hepatitis A virus (HAV) adsorption and on the successive events of infection in a monkey cell line (Frp/3 cells) was investigated. Treatments of Frp/3 cells with colcemide, vinblastine and cytochalasin D, which affect cytoskeleton organization, indicated that neither microtubules nor microfilaments play an important role in the early events of HAV infection. Monensin, which acts as an ionophore on intracellular vesicle compartments inhibited HAV infection probably at the uncoating step. Inhibition of viral replication to a different degree was observed with both inhibitors of oxidative phosphorylation, such as dinitrophenol and sodium azide, and with an inhibitor of glycolysis, 2-deoxy-D-glucose. However, none of these compounds significantly affected the early steps of infection, thus demonstrating that HAV replication is largely dependent upon cell energy.

Azides↗
PubMed1989

Binding sites for rubella virus on erythrocyte membrane.

To identify molecule(s) with the properties of rubella virus (RV) receptor, goose erythrocyte membranes were isolated and tested for their ability to complete with whole cells for viral binding and fusion. Solubilized membranes showed a dose-dependent inhibiting activity on either rubella virus attachment or its fusion with erythrocytes at acidic pH. The inhibitory activity was enhanced by trypsin and neuraminidase, and inactivated by phospholipase A2 digestion, pointing towards the involvement of lipid structures as receptor sites for RV. After isolation of the different membrane components, only the lipid moiety, specifically phospholipids and glycolipids, was found to inhibit viral biological activities. When the major membrane lipids were examined separately, phosphatidylserine and cerebroside sulfate showed a strong inhibiting activity on viral hemagglutination and subsequent hemolysis. The capacity of several pure phospholipids (phosphatidylinositol, phosphatidylcholine and sphingomyelin) to inhibit the hemolysis but not the binding of the virus to the erythrocytes indicated that different membrane lipid components are involved in the attachment and the fusion step. Enzymatic and chemical modifications of whole erythrocytes confirmed the role of membrane lipid molecules in the cell surface receptor for RV.

Animals↗
PubMed1989

Membrane lipid components interacting with hepatitis A virus.

The involvement of lipid components in hepatitis A virus (HAV) attachment to host cells has been investigated. Isolated Frp/3 cell membranes and whole lipids, phospholipid and glycolipid fractions extracted from them were able to bind the virus and to prevent infection. Treatment of virus with various phospholipids or glycolipids demonstrated the participation of phosphatidylserine, phosphatidylethanolamine and galactose in HAV binding. Results obtained added further information on the receptor specificity of host cells for HAV.

Animals↗