Biomedical subjects

M A Rebello

Publications and source records attributed to M A Rebello.

At least 19 recordsLinked to original sources

PubMed2003

Inactivation of classical swine fever virus: association of hydrostatic pressure and ultraviolet irradiation.

Reversible pressure-induced disassembly of several viruses has suggested the idea of using hydrostatic pressure to suppress virus infectivity. In this study, the effects of high hydrostatic pressure and ultraviolet (UV) irradiation were investigated on classical swine fever virus (CSFV) in an attempt to eliminate residual infectivity. The structural modifications were followed by intrinsic fluorescence and biological activity assays. The kinetics of CSFV inactivation showed that pressure-induced inactivation was not enough to eliminate viral infectivity. However, when pressure was applied in association with UV irradiation no infectious focus was observed. The application of these two methods against CSFV can be an attractive inactivation strategy for the development of a vaccine.

Animals↗

PubMed2003

Effect of monensin on Mayaro virus replication in monkey kidney and Aedes albopictus cells.

The effect of a cationic ionophore, monensin, on the replication of Mayaro virus in monkey kidney TC7 and Aedes albopictus cells has been studied. Treatment of these cells with 1 micromol/l monensin during infection did not affect the virus protein synthesis but inhibited severely the virus replication. Electron microscopy of the cells infected with Mayaro virus and treated with monensin revealed that the morphogenesis of Mayaro virus was impaired in TC7 but not in A. albopictus cells.

Aedes↗

PubMed2001

Inhibition of Mayaro virus replication by prostaglandin A(1) in Vero cells.

Prostaglandins exhibit antiviral activity against a wide variety of RNA and DNA viruses. In the present report, we describe the effect of cyclopentenone prostaglandin A(1) (PGA(1)) on Mayaro virus replication in Vero cells. Virus yield was significantly reduced at nontoxic concentrations which did not suppress DNA, RNA or protein synthesis in uninfected or infected cells. Antiviral action decreased if PGA(1) was added at later times after infection. In Mayaro virus-infected cells, PGA(1) inhibited the synthesis of virus proteins. This effect is accompanied by the induction of heat shock proteins (HSPs). Actinomycin D treatment not only inhibited the induction of HSPs but also partially prevented PGA(1) antiviral activity.

Alphavirus↗

PubMed2000

The metastable state of nucleocapsids of enveloped viruses as probed by high hydrostatic pressure.

Enveloped viruses fuse their membranes with cellular membranes to transfer their genomes into cells at the beginning of infection. What is not clear, however, is the role of the envelope (lipid bilayer and glycoproteins) in the stability of the viral particle. To address this question, we compared the stability between enveloped and nucleocapsid particles of the alphavirus Mayaro using hydrostatic pressure and urea. The effects were monitored by intrinsic fluorescence, light scattering, and binding of fluorescent dyes, including bis(8-anilinonaphthalene-1-sulfonate) and ethidium bromide. Pressure caused a drastic dissociation of the nucleocapsids as determined by tryptophan fluorescence, light scattering, and gel filtration chromatography. Pressure-induced dissociation of the nucleocapsids was poorly reversible. In contrast, when the envelope was present, pressure effects were much less marked and were highly reversible. Binding of ethidium bromide occurred when nucleocapsids were dissociated under pressure, indicating exposure of the nucleic acid, whereas enveloped particles underwent no changes. Overall, our results demonstrate that removal of the envelope with the glycoproteins leads the particle to a metastable state and, during infection, may serve as the trigger for disassembly and delivery of the genome. The envelope acts as a "Trojan horse," gaining entry into the host cell to allow release of a metastable nucleocapsid prone to disassembly.

Alphavirus↗

PubMed2000

Weak bases affect late stages of Mayaro virus replication cycle in vertebrate cells.

This paper describes the effect of two weak bases (ammonium chloride and chloroquine) on the morphogenesis of Mayaro virus. When Mayaro virus-infected TC7 (monkey kidney) cells were treated with these agents it was observed that weak bases caused a significant reduction in virus yield. Also, cellular protein synthesis, which is inhibited by Mayaro virus infection, recovered to nearly normal levels. However, the synthesis of Mayaro virus proteins was affected. These phenomena were dose-dependent. The process of Mayaro virus infection in vertebrate cells is very rapid. Virus precursors are not observed in cell cytoplasm and budding through the plasma membrane seems to be the only way of virus release. Electron microscopy of cells infected with Mayaro virus and treated with weak bases revealed an accumulation of virus structures in cell cytoplasm. The study also noted an inhibition of budding through the plasma membrane and the appearance of virus particles inside intracytoplasmic vacuoles. These observations indicate an impairment at the final stages of the virus replication cycle.

Alphavirus↗

PubMed1999

Effect of brefeldin A on Mayaro virus replication in Aedes albopictus and Vero cells.

Brefeldin A (BFA), a fungal metabolite that blocks transport of newly synthesized proteins from the endoplasmic reticulum, was found to inhibit Mayaro virus replication. At the concentration of 0.05 microgram/ml, the yield of the virus was inhibited by 94% in Aedes albopictus cells and by 99.5% in Vero cells. Treatment of A. albopictus cells with BFA did not inhibit the virus protein synthesis. However, this compound drastically reduced viral protein synthesis in Vero cells. The inhibitory effect progressively declined when BFA was added at late times post infection (p.i.). The effect of BFA on protein glycosylation is discussed.

Aedes↗

PubMed1998

Effect of prostaglandin A1 in the induction of stress proteins in Aedes albopictus cells.

Prostaglandins are natural fatty acid derivatives with diverse physiological effects, including immune function and the control of cell growth. While the action of prostaglandins in the induction of stress proteins in vertebrate cells is well documented, their functions in invertebrate cells have been poorly investigated. The purpose of the present study was to investigate the effect of prostaglandin A1 (PGA1; 0.25, 1.25 and 12.5 micrograms/ml) on protein synthesis during the growth of Aedes albopictus cells. We found that PGA1 stimulates the synthesis of several polypeptides with molecular masses of 87, 80, 70, 57, 29, 27 and 23 kDa in Aedes albopictus cells. When the proteins induced by PGA1 and those induced by heat treatment were compared by polyacrylamide gel electrophoresis, PGA1 was found to induce the stress proteins. The HSP70 family and the low-molecular weight polypeptides (29 and 27 kDa, respectively) were induced by PGA1 in the lag phase. We also observed that PGA1 is able to induce a 23-kDa polypeptide independently of the growth phase of the cell.

Aedes↗

PubMed1998

Inhibition of Mayaro virus replication by prostaglandin A1 and B2 in Vero cells.

The effect of prostaglandins (PGA1 and PGB2) on the replication of Mayaro virus was studied in Vero cells. PGA1 and PGB2 antiviral activity was found to be dose-dependent. However, while 10 micrograms/ml PGB2 inhibited virus yield by 60%, at the same dose PGA1 suppressed virus replication by more than 90%. SDS-PAGE analysis of [35S]-methionine-labelled proteins showed that PGA1 did not alter cellular protein synthesis. In infected cells, PGA1 slightly inhibited the synthesis of protein C, while drastically inhibiting the synthesis of glycoproteins E1 and E2.

Alphavirus↗

PubMed1998

Inhibition of Mayaro virus replication by cerulenin in Aedes albopictus cells.

The antibiotic cerulenin, an inhibitor of lipid synthesis, was shown to suppress Mayaro virus replication in Aedes albopictus cells at non-cytotoxic doses. Cerulenin blocked the incorporation of [3H]glycerol into lipids when present at any time post infection (p.i.). Cerulenin added at the beginning of infection inhibited the synthesis of virus proteins. However, when this antibiotic was added at later stages of infection, it had only a mild effect on the virus protein synthesis. The possibility that cerulenin acts by blocking an initial step in the Mayaro virus replication after virus entry and before late viral translation is discussed.

Animals↗

PubMed1997

In situ relationship between sucrose exposure and the composition of dental plaque.

The aim of this study was to analyze the composition of dental plaque according to sucrose exposure. Twelve adult volunteers took part in this crossover study done in four phases of 28 days each. For each phase of the study, an acrylic resin appliance containing four human dental enamel blocks was constructed for each volunteer. A 20% sucrose solution was dripped onto the enamel blocks from 0 to 8 times/day. The volunteers were randomly assigned to the treatments. During the experimental period all the subjects used fluoride-free dentifrice, refrained from brushing the enamel blocks and drank water fluoridated at 0.70 ppm F. After each phase the concentrations of fluoride (F), calcium (Ca), phosphorus (P) and total carbohydrate were determined in dental plaque. Statistical analyses showed that frequent sucrose exposure significantly (p < 0.05) reduced the F, Ca and P concentrations in dental plaque, but increased the alkali-soluble carbohydrate concentration. The results suggest that the cariogenicity of dental plaque formed in the presence of sucrose cannot be attributed only to its higher porosity, but the lower inorganic concentration may also be important.

Adult↗

PubMed1997

Basic surface properties of Aedes albopictus cells: effect of Mayaro virus infection on electrostatic charge and surface tension.

Aedes albopictus cells possess a negative cell surface charge of -12.7 mV with an isoelectrophoretic point (IEP) located between pH 3.0 and 4.0. Infection with Mayaro virus rendered the surface of A. albopictus cells less negative reaching a zeta-potential value of -9.7 mV after 100 h of infection. Concomitantly, the IEP of the infected cells were also altered from 3.0-4.0 to 4.0-5.0. Furthermore, the contact angle measurements clearly showed qualitative alterations in the cell surface of infected cells.

Aedes↗

PubMed1996

Effect of isoprinosine on rotavirus replication in vitro.

Isoprinosine (IPS) is a synthetic drug whose antiviral effect on rotavirus replication in vitro has been characterized in terms of the decrease in metachromasia after acridine orange staining. The present study describes the effect of IPS on the synthesis of viral RNA in vitro. MA-104 cell cultures infected with simian rotavirus strain SA-11 were incubated with zero, 250, 500 and 1,000 micrograms/ml IPS and 22, 24, 48, 52, 72 and 76 h after infection the cultures were submitted to a 1-h starvation period, followed by a 2-h pulse with 10 microCi/ml of [3H]-uridine. The homogenates of virus-infected cultures treated or not with IPS were submitted to phenol/chloroform extraction followed by polyacrylamide gel electrophoresis. The amount of radioactivity in viral RNA eluted from the gel strips was determined. Inhibition of viral RNA synthesis was highest at the IPS concentration of 1,000 micrograms/ml at 72 h after infection, corresponding to 78% inhibition. Although the results obtained in vitro suggest that IPS may be useful for the treatment of rotavirus infection, an in vivo demonstration of its efficacy is needed.

In Vitro Techniques↗

PubMed1995

Prostaglandin A1 inhibits replication of Mayaro virus in Aedes albopictus cells.

Prostaglandin A1 (PGA1) reduced Mayaro virus replication in Aedes albopictus (mosquito) cells in culture. The highest nontoxic dose of PGA1, 7.5 microM, decreased virus production by 90%. In Mayaro virus-infected cells, PGA1 inhibited virus-specific protein synthesis. However, in mock-infected cells the presence of PGA1 stimulated the synthesis of several proteins with molecular masses of 70, 57 and 23 kDa, respectively. The data obtained from this study show that PGA1 plays a role in the metabolic regulation of Aedes albopictus cells, blocking the synthesis of Mayaro virus and inducing the synthesis of cellular polypeptides.

Aedes↗

PubMed1993

Interferon action on Mayaro virus replication.

Treatment of TC7 cells with interferon (IFN) drastically reduced the yield of infectious Mayaro virus under experimental conditions that virus attachment and penetration into the cells were not affected. In IFN-treated cells, synthesis of Mayaro virus proteins was inhibited and cellular protein synthesis was restored. This phenomenon is dependent on IFN concentration and multiplicity of infection. Electron microscopy of these cells revealed normal and anomalous viral particles inside cytoplasmic vacuoles. This suggests that IFN also interferes with Mayaro virus morphogenesis and inhibits the release of virions from cells.

Alphavirus↗

PubMed1990

Ultrastructural study of Mayaro virus replication in BHK-21 cells.

The replication of Mayaro virus in BHK-21 cells was studied by electron microscopy. The infected cells show an intense vacuolization and proliferation of membranous structures. At 5 h post-infection, precursor virus particles were seen in the cytoplasm of infected cells. Later, mature virus particles were found outside the cells and budding from the plasma membrane. Enveloped virus particles were also observed inside the vesicles and budding across their membrane. The release of virus particles into the extracellular space by exocytosis was also observed. In a later stage of the infection, inclusion bodies were sometimes present in the cytoplasm of infected cells. We conclude that in BHK-21 cells, budding from the plasma membrane is the main process of Mayaro virus maturation, and in this kind of cell replication differs significantly from that observed in Aedes albopictus cells.

Alphavirus↗

PubMed1989

Replication of Mayaro virus in Aedes albopictus cells: an electron microscopic study.

The replication of Mayaro virus in Aedes albopictus cells, was studied by electron microscopy at various times post-infection. In infected cells we observed the presence of cytoplasmic vesicles containing viral nucleocapsids and mature virus particles but at no time did we detect virus budding into such vacuoles. Budding of virus through plasma membrane was rarely observed. Our results are discussed considering the possibility of the release of virus particles to the extracellular space by exocytosis.

Aedes↗

PubMed1989

Na+ and K+ concentration and regulation of protein synthesis in L-A9 and Aedes albopictus cells infected with Marituba virus (Bunyaviridae).

Infection of L-A9 cells with Marituba virus produces a severe inhibition of protein synthesis. This inhibition is temporally correlated with an increase in the intracellular Na+ concentration and a decrease in the intracellular K+ concentration. However, in Marituba virus-infected Aedes albopictus cells the intracellular level of Na+ and K+ ions and protein synthesis remained unaltered. Incubation of both cell types at high NaCl concentration facilitated the translation of viral RNA whereas the cellular protein synthesis was inhibited. Using a hypotonic medium, the opposite was found. Results are discussed in terms of a possible involvement of these ions in the viral translational process.

Aedes↗

PubMed1987

Selective inhibition of protein synthesis by hypertonic medium in Marituba (Bunyaviridae) virus-infected L-A9 cells.

Elevation of the NaCl concentration in the growth medium of L-A9 cells caused an inhibition of the protein synthesis accompanied by a complete breakdown of polyribosomes. However, a complete recovery of the rate of protein synthesis was observed when isotonicity was restored. In Marituba virus infected cells, protein synthesis became resistant to hypertonic treatment. Under hypertonic conditions cellular protein synthesis was selectively suppressed and an enhancement of virus proteins was observed. Analysis of the virus specific proteins by polyacrylamide gel electrophoresis revealed that the synthesis of G1 was unalterable, and N was stimulated.

Animals↗