Biomedical subjects

M A Rebello

Publications and source records attributed to M A Rebello.

At least 19 recordsLinked to original sources

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↗

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↗

PubMed1987

The surface charge of L-A9 cells and Aedes albopictus cells infected with Marituba (Bunyaviridae) virus.

The surface charge of Marituba virus infected L-A9 cells and Aedes albopictus cells was estimated by direct measurement of their electrophoretic mobilities. Uninfected L-A9 cells and A. albopictus cells have mean electrophoretic mobilities of -1.083 microns/s X cm/V and -1.019 microns/s X cm/V, respectively. In Marituba virus infected L-A9 cells a progressive decline in the electrophoretic mobility was observed. In contrast, in Marituba virus infected A. albopictus cells the electrophoretic mobility of the cell surface was unaltered.

Aedes↗

PubMed1987

Effect of high temperature on Aedes albopictus cells infected with Mayaro virus.

The multiplication of Mayaro virus in Aedes albopictus cells was drastically inhibited after incubation at 37 degrees C. The effect of short-term exposure of infected cells to high temperatures (heat shock) produced a preferential translation of the heat shock messengers when compared to the viral mRNAs. When cells were shifted back to 28 degrees C (the optimum growth temperature for Aedes albopictus cells), preferential translation of viral mRNA occurred. Although the infected cells were programmed for preferential translation of viral messengers, the thermal treatment was able to shift the translational machinery towards synthesis of heat shock proteins.

Aedes↗

PubMed1987

Lactate dehydrogenase from cultured Aedes albopictus cells: kinetic and isozyme analysis.

L(+) lactate dehydrogenase (LDH) activity from cultured cells of Aedes albopictus was studied as a kinetic model of carbohydrate metabolism. Enzyme kinetics were studied in the forward (lactate as substrate) and reverse (pyruvate as substrate) reactions and the apparent Km values were obtained showing LDH higher affinity for pyruvate. The Hill coefficient values for each substrate were similar and indicate the existence of only one binding site on the enzyme. Isozyme analysis on cellulose-acetate electrophoresis presented a single band of LDH which presumably is of the LDH-5 type. The results obtained contribute to the assumption that Aedes albopictus cells have a predominance of anaerobic metabolism.

Aedes↗

PubMed1986

Core transcription restores in vitro inhibition of protein synthesis induced by vaccinia virus.

When Ehrlich acistes tumor cell lysate is incubated in the presence of vaccinia core, protein synthesis is impaired. However, when the same system is coupled with viral transcription, protein synthesis is restored. The reversal of endogenous protein synthesis is inhibited by actinomycin D, suggesting that de novo RNA synthesis is required for the reversal of total protein synthesis. When the in vitro products of synthesis are analysed by polyacrylamide gel electrophoresis, two newly synthesized peptides which are not present in the noncoupled transcription-translation system are observed. These two peptides have molecular weights of 31 000 and 25 000, similar to viral early proteins.

Animals↗

PubMed1986

Marituba (Bunyaviridae) virus replication in cultured Aedes albopictus cells and in L-A9 cells.

The replication of Marituba virus (Bunyavirus genus, family Bunyaviridae), was studied in Aedes albopictus (mosquito) cells. Infection of Aedes albopictus cells with Marituba virus was characterized by an initial acute phase of infection in which large amounts of virus were produced and further by a persistent phase of infection in which virus yield was much lower. No changes in host cell DNA, RNA and protein synthesis were observed in Aedes albopictus cells infected with Marituba virus. In contrast in L-A9 (mouse fibroblasts) cells this virus shut-off the host macromolecular synthesis. During the replication of MTB virus in L-A9 cells three virus-specific proteins (G1, G2 and N) were detected. In Aedes albopictus cells, Marituba virus replicates slowly and two virus-specific proteins (G1 and N) accumulate in these cells.

Aedes↗

PubMed1985

Interferon induction in mouse fibroblast L-A9 cells.

Mouse L-A9 cell interferon was induced by infection with Newcastle disease virus. Interferon production was 1.5 X 10(5) IU/10(7) cells. Interferon was partially purified by precipitation with ammonium sulphate, chromatography on CM-Sephadex and hydrophobic chromatography on octyl-agarose. The specific activity of the final preparation was 1.7 X 10(7) IU/mg protein. Treatment of L-A9 cells with 20 IU/ml interferon prior to viral infection inhibited the intracellular accumulation of reovirus-specific double-stranded RNA. Dose-response studies of the cells to interferon indicated that L-A9 cells require 10, 13 and 15 IU/ml to obtain 50% viral plaque reduction for Marituba virus, vesicular stomatitis virus and reovirus, respectively. The present results demonstrate the potential of mouse L-A9 cells as an interferon-producing system and also as a model for the study of the effect of cellular response to exogenous interferon treatment on the replication of RNA viruses.

Animals↗

PubMed1983

Autointerference of Marituba Virus (Bunyaviridae) in mouse L cells by defective interfering particles.

The growth characteristics of Marituba virus, a member of the Bunyaviridae family, were studied in L-A9 cells. Virus yield was strictly dependent on the MOI. Quantitation of infectious virus released from the cells revealed a decrease in magnitude with continued serial passage. Specificity of the Marituba virus inhibitory response was investigated in relation to interference within homologous and heterologous viral classes. Virus particles were studied by isopycnic centrifugation in sucrose gradients. Under conditions of multiple viral passages at high multiplicity, two major classes of virus particles were produced, one band at 1.19 g/ml and another at 1.16 g/ml. Particles at 1.16 g/ml were noninfectious. Our results suggest that during the replication of Marituba virus at high MOI a population of defective interfering particles is generated.

Animals↗