Biomedical subjects

N Orsi

Publications and source records attributed to N Orsi.

At least 37 records · Page 2Linked to original sources

PubMed1994

Effect of various detergents on the interaction between BK virus and susceptible cells.

The activity of various types of detergents towards the infectivity and the hemagglutinating activity of BK virus was studied. Similarly to other non enveloped small viruses, BK virus showed a significant resistance to non cytotoxic concentrations of the compounds tested, with the exception of N-Dodecyl-N,N-dimethyl-3-ammonio-1-propane-sulfonate. In some cases, mainly with N-Octylglucoside, both the infectivity and the hemagglutinating activity of BK virus was enhanced.

Animals↗

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

Invasiveness of Shigella flexneri in poliovirus infected HT-29 cells.

In this paper we report the effect in HT-29 cells of mixed infections with poliovirus type 1 and Shigella flexneri serotype 5 strain M90T and derivative strains differing in adhesive as well as invasive properties. HT-29 epithelial intestinal cells derived from a human colon adenocarcinoma are a good model for coinfection studies because they are susceptible both to poliovirus replication and to S. flexneri invasion. The results show that 48 h after infection by poliovirus the invasiveness of wild-type S. flexneri M90T and of its adherent and invasive derivative M90T (pIL22) is increased. However, the alterations produced in HT-29 cells at the later stage of poliovirus infection are not sufficient to promote the internalization of simply non invasive, or non invasive but adherent, isogenic derivative bacterial strains.

Bacterial Adhesion↗

PubMed1993

Chiral discrimination and antipicornavirus activity of 6-oxazolinylisoflavan.

Racemic 6-oxazolinylisoflavan, a highly effective inhibitor of rhinovirus serotype 1B in vitro, was resolved by high-performance liquid chromatography on a chiral stationary phase in order to study the activity of the enantiomers against picornaviruses. The absolute configuration of the two isomers was determined by circular dichroism curves. The antipicornavirus activity of each isomer, separately collected, was evaluated in vitro against human rhinovirus serotype 1B, enterovirus 71, echovirus 6, coxsackievirus B4, and poliovirus type 2 by means of the plaque reduction assay. Both enantiomers were inhibitors of picornavirus replication with the degree of their activity depending on virus and isomer tested.

Antiviral Agents↗

PubMed1993

Effect of sub-inhibitory concentrations of antibiotics on the hemolytic activity of Legionella.

The effect of sub-inhibitory concentrations of various antibiotics on the hemolytic activity of different strains of Legionella has been tested. By means of a gradient plate technique it was possible to demonstrate that in a limited range of sub-inhibitory concentrations, antibiotics did not affect bacterial growth but inhibited the hemolytic activity of the strains examined.

Anti-Bacterial Agents↗

PubMed1993

Iron-regulated salicylate synthesis by Pseudomonas spp.

Two iron-regulated compounds have been found in acidified ethyl acetate extracts from culture supernatants of Pseudomonas aeruginosa and Pseudomonas cepacia type-strains. Synthesis of both compounds paralleled iron-deficient growth, and was repressed in the presence of 100 microM-FeCl3. Yields of these substances varied among different strains and attained maximum levels during stationary phase. Thin layer chromatographic analysis in five different solvent systems revealed that the slower-moving compound chromatographed as two distinct bands, and showed RF values and spectral properties similar to pyochelin. The faster-moving compound co-migrated as a single band with a standard of commercial salicylic acid in each of the chromatographic systems tested. Moreover, a molecule with an identical RF was also produced by Pseudomonas fluorescens CHA401, which is known to synthesize salicylic acid as the only siderophore during iron-limited growth. Spectrophotometric and spectrofluorometric titrations led to the identification of this iron-regulated compound as salicylic acid, in agreement with the structure deduced from 1H-NMR and mass spectroscopy. The identity of the P. cepacia siderophore azurechelin as salicylic acid was also conclusively demonstrated. Salicylic acid, like pyochelin and pyoverdin, promoted P. aeruginosa growth in an iron-depleted medium. These results are consistent with a putative siderophore activity for salicylic acid, i.e. azurechelin, as has been demonstrated for P. aeruginosa, P. fluorescens and P. cepacia. Thus, salicylic acid is likely to act as a siderophore in more than one species belonging to the genus Pseudomonas.

Burkholderia cepacia↗

PubMed1992

SA-11 rotavirus binding to human serum lipoproteins.

An investigation of SA-11 rotavirus binding to human serum lipoproteins was carried out. Various subclasses of lipoproteins, purified by ultracentrifugal flotation, and apoproteins were tested for their activity in inhibiting viral infectivity and hemagglutination. All tested lipoprotein subclasses (very low, low and high density, lipoproteins; VLDL, LDL, HDL, HDL1) were shown to interact with SA-11 rotavirus: VLDL and LDL were the most active in preventing rotavirus replication, whereas HDL and HDL1 inhibited viral hemagglutination to a greater extent. Moreover, A1 and A2 apoproteins were effective towards both viral infectivity and hemagglutination. Results obtained are in agreement with a preferential interaction of VP7 or VP4 proteolytic products with low density lipoproteins and of VP8* with high density lipoproteins. Binding of SA-11 to lipoproteins or apoproteins was also quantified by an enzyme-linked immunosorbent assay procedure and lipoproteins-virus interaction was visualized by electron microscopy.

Animals↗

PubMed1992

Virulence determinants in Pseudomonas aeruginosa strains from urinary tract infections.

A total of 121 uropathogenic Pseudomonas aeruginosa strains were examined for production of several virulence-related factors. These strains were distributed in five predominant O-serotypes, i.e. O 4, O 12, O 11, O 6 and O 5, which accounted respectively for 23.9, 23.1, 12.3, 8.2 and 5.7% of isolates. Pyochelin and pyoverdin siderophores were produced by most of the isolates, defective variants occurring at very low frequency (2.4% for pyochelin and 7.4% for pyoverdin). Adherence to uroepithelial cells and production of cytotoxins was demonstrated in 52.8 and 67.7% of the strains, respectively, with higher frequencies for epidemiologically related strains belonging to serotypes O 4 and O 12. Titration of total proteases, elastase and phospholipase C revealed a high degree of heterogeneity among isolates. However, examination of individual O-serotypes by exoenzyme production showed that elevated levels of total proteases and elastase were characteristics of serotypes of minor numerical importance, i.e. O 1, O 10, O 11 and O 17, whilst low levels of elastase were produced by strains belonging to the predominant serotypes, namely O 4 and O 12. Moreover, epidemiologically related strains belonging to serotypes O 4 and O 12 appeared more homogeneous than the whole serogroup, when compared with other groups on the basis of exoenzyme levels.

Bacterial Adhesion↗

PubMed1992

Constituents of Eriobotrya japonica. A study of their antiviral properties.

The CHCl3 extract of Eriobotrya japonica from an Italian source was shown to contain four new triterpene esters, namely, 23-trans-p-coumaroyltormentic acid [1], 23-cis-p-coumaroyltormentic acid [2], 3-O-trans-caffeoyltormentic acid [3], and 3-O-trans-p-coumaroylrotundic acid [4], in addition to three common ursolic acid derivatives 5, 6, and 7. An investigation of the antiviral properties of compounds 1-7 revealed that only 3 significantly reduced rhinovirus infection. The compounds were ineffective towards human immunodeficiency virus type 1 (HIV-1) and Sindbis virus replication.

Antiviral Agents↗

PubMed1992

Effect of biological and synthetic polymers on BK virus infectivity and hemagglutination.

The effect of several biological and synthetic polymers, chosen on the basis of different physical and chemical properties, was investigated on BK virus infectivity and hemagglutination. It was observed that polyanions like mucin, dextran sulfate and heparin depressed the viral binding, whereas polycations had no significant activity, with the exception of poly-L-lysine, which enhanced it. The effect of the active polymers was studied in different experimental conditions and the results obtained suggested that polyanions may act directly on the virus particle, whereas the target of polycations could be at the level of cell membranes. However, the effect shown by the active compounds did not appear to be simply related to the electric charge since neutral compounds, such as tamarind gum and locust bean gum, showed a marked inhibitory effect on BK virus binding to the cells.

BK Virus↗

PubMed1992

Mechanism of action of the antirhinovirus flavanoid 4',6-dicyanoflavan.

4',6-Dicyanoflavan (DCF), a new antirhinovirus compound, was shown to inhibit an early event of rhinovirus type 1B replication in HeLa cells. When DCF was present from the beginning of infection or was added no later than the first hour of infection, the compound completely prevented viral RNA and protein synthesis and the virus-induced shutoff of host translation. DCF had no adverse effect either on virus binding to the cell membrane or on virus penetration into cells, whereas it delayed the uncoating kinetics of neutral redencapsidated rhinovirus. DCF also prevented mild acid or thermal inactivation of virus infectivity, although it reversibly interacted with virions. These results suggest that the stabilizing effect of DCF on virion capsid conformation is responsible for uncoating inhibition.

Antiviral Agents↗

PubMed1992

Metal regulation of siderophore synthesis in Pseudomonas aeruginosa and functional effects of siderophore-metal complexes.

Pseudomonas aeruginosa synthesizes two siderophores, pyochelin and pyoverdin, characterized by widely different structures, physicochemical properties, and affinities for Fe(III). Titration experiments showed that pyochelin, which is endowed with a relatively low affinity for Fe(III), binds other transition metals, such as Cu(II), Co(II), Mo(VI), and Ni(II), with appreciable affinity. In line with these observations, Fe(III) and Co(II) at 10 microM or Mo(VI), Ni(II), and Cu(II) at 100 microM repressed pyochelin synthesis and reduced expression of iron-regulated outer membrane proteins of 75, 68, and 14 kDa. In contrast, pyoverdin synthesis and expression of the 80-kDa receptor protein were affected only by Fe(III). All of the metals tested, except Mo(VI), significantly promoted P. aeruginosa growth in metal-poor medium; Mo(VI), Ni(II), and Co(II) were more efficient as pyochelin complexes than the free metal ions and the siderophore. The observed correlation between the affinity of pyochelin for Fe(III), Co(II), and Mo(VI) and the functional effects of these metals indicates that pyochelin may play a role in their delivery to P. aeruginosa.

Bacterial Outer Membrane Proteins↗

PubMed1992

Isolation and characterization of Pseudomonas aeruginosa mutants blocked in the synthesis of pyoverdin.

We have isolated and characterized by chemical and enzymatic analyses three distinct types of pyoverdin-defective (pvd) mutants of Pseudomonas aeruginosa PAO1. The pvd-1 mutant is an L-N5-hydroxyornithine (L-N5-OH-Orn) auxotroph unable to hydroxylate L-ornithine (L-Orn) in a cell-free system and requiring L-N5-OH-Orn for pyoverdin production. The other two types of mutants appear to be blocked in further steps of the biosynthetic pathway leading to pyoverdin, namely, the acylation of L-N5-OH-Orn (pvd-2) and chromophore synthesis (pvd-3). The different pvd mutations were all found to be located in the catA1 region at 47 min of the genetic map of P. aeruginosa PAO1.

Chromosome Mapping↗

PubMed1992

Effect of enterovirus infection on susceptibility of HeLa cells to Shigella flexneri invasivity.

Invasiveness of Shigella flexneri M90T in HeLa cells was significantly increased when cells were preinfected with poliovirus 1, coxsackievirus B3 and echovirus 6. This effect was dependent on the dose of virus used, evident at early stages of viral infection and lasted hours before the appearance of a cytopathic effect. An increase of bacterial invasion ability was also noticed when HeLa cells were incubated with UV-inactivated enteroviruses. This enhancing effect obtained with both viable and UV-inactivated enteroviruses was not observed when in coinfection experiments HN555, a mutant of S. flexneri M90T which lacked invasive properties, was used. The data presented here suggest that the early steps of enterovirus infection induce some alterations of HeLa cells which are responsible for the enhancing of the invasiveness of S. flexneri M90T, but not sufficient to promote internalization of a non-invasive strain.

Animals↗

PubMed1992

Effect of electric charged molecules on Sindbis virus hemagglutination and hemolysis.

The role of electrostatic interactions in the attachment and fusion at acidic pH of Sindbis virus (SNV) with goose erythrocytes was studied, investigating the effect of several anionic and cationic polyelectrolytes on SNV hemagglutination and hemolysis. In order to establish the target of active drugs, the compounds were incubated either with the virus particles or with the erythrocytes. Dextran sulfate was the only compound able to inhibit the attachment of SNV to the erythrocytes. Fusion of virus with red cells was reduced dose-dependently by the polyanions dextran sulfate, mucin and polygalacturonic acid. On the contrary two polycations, polylysine and polybrene, enhanced viral hemolytic activity. However the effect of polyions is not exclusively related to the electric charge since ineffective molecules were found in both classes of compounds.

Animals↗

PubMed1991

Siderophore production by Salmonella species isolated from different sources.

A total of 230 Salmonella strains were screened for enterobactin and aerobactin production, sensitivity to bacteriocins and resistance to antibiotics. All the isolates produced the phenolate siderophore enterobactin. Amongst these, 74 strains, most belonging to S. enteritidis, were sensitive to colicin B. Only 26 isolates, all belonging to S. wien, produced an additional iron chelator, i.e. the siderophore aerobactin, and 22 out of these were sensitive to cloacin DF13. Analysis of iron repressible outer membrane proteins and plasmid profiles in S. wien strains showed that the expression of a 74-kDa iron-repressible outer membrane protein and the presence of large plasmids were associated with multiple antibiotic resistance, aerobactin production and sensitivity to cloacin DF13. The incidence of aerobactin-producing strains among S. wien isolates was higher during years 1974-1985; the epidemiological implications of these results are discussed.

Bacterial Outer Membrane Proteins↗

PubMed1991

Effect of polyions on the early events of Sindbis virus infection of Vero cells.

To clarify the role of electrostatic interactions in the binding of Sindbis virus (SNV) to cell membrane receptors, we investigated the effect of different polyions on the initial steps of infection of Vero cells by the virus. Several polyanions (mucin, heparin, polygalacturonic acid) and polycations (polylysine, protamine, polybrene) were able to reduce the replication of SNV when present in the viral adsorption period, whereas others (chondroitin sulfate, polymyxin B sulfate, histone) were devoid of any activity. Therefore the electric charge alone is not sufficient to explain the action of compounds. The effects of polyions on receptor binding, on bound virus, and on internalized virus have been examined. All the drugs inhibited SNV infection by affecting its binding to the cellular receptor. The results indicated that heparin and mucin act directly on the virus particle while polycations bind to the cell membrane receptor for the virus, protamine being effective on both targets. Since among polyanions glycosaminoglycans showed a strong inhibiting activity, the involvement of these molecules in the virus surface receptor was assessed by enzyme digestion of cell membrane with heparinase and chondroitin ABC lyase.

Animals↗

PubMed1991

Rabies virus infection in Aedes pseudoscutellaris cells: a study on receptorial structures.

Rabies virus is able to infect in vitro a wide range of homeothermic and poikilothermic cells but little is known about its multiplication in arthropod cells. In this research the infection of rabies virus in Aedes pseudoscutellaris cells, a mosquito cell line susceptible to mosquito-borne viruses, was studied. After 60 days of incubation at 26 degrees C up to 70% of infected cells showed the synthesis of both viral nucleocapsid and envelope antigens, although viral yield and cell damage could not be detected. Research performed in order to investigate the role of membrane carbohydrate moieties in rabies virus-mosquito cell interaction suggested the participation of galactose and N-acetylglucosamine whereas sialic acid, known to be a rabies binding site in many homeothermic cell lines, was not involved.

Aedes↗