Biomedical subjects

L Carrasco

Publications and source records attributed to L Carrasco.

At least 235 records · Page 13Linked to original sources

PubMed1986

External ATP permeabilizes transformed cells to macromolecules.

External ATP under certain ionic conditions render transformed cells permeable to the translation inhibitor hygromycin B. With this method the protein toxin alpha-sarcin selectively penetrates into 3T6 cells, as compared to 3T3 cells. This entry is enhanced by ATP synthesis blockers such as CCCP. Other proteins, such as horseradish peroxidase and luciferase, also pass selectively in 3T6 cells under permeabilization conditions.

Adenosine Triphosphate↗

PubMed1986

The inhibition of nucleic acid synthesis in encephalomyocarditis virus-infected L929 cells: effects on nucleoside transport.

Picornavirus infection induces a profound inhibition of labelling of newly synthesized RNA in some cell lines. EMC virus blocks transcription in L929 cells, particularly at early times during infection. This inhibition is not dependent on virus gene expression, since it occurs with UV-inactivated virus and also in the presence of translation inhibitors. The inhibition can be largely accounted for by the blockade of [3H]nucleoside transport, as suggested by the transport kinetics and incorporation of labelled nucleoside from preloaded cells. The inhibition of transport and incorporation into TCA-precipitable material was observed with pyrimidine (uridine, thymidine and cytosine) and purine nucleosides (adenosine and guanosine), but the blockade by EMC virus was higher with the latter nucleosides. Preloading of cells with any of these nucleosides resulted in a decreased effect on nucleoside incorporation into nucleic acid after virus infection. These results suggest that the inhibition of incorporation of labelled nucleosides into nucleic acid in EMC virus-infected cells can be explained, at least in part, by the decreased pool size of the phosphorylated nucleosides. These effects are not specific for L cells, because they are also observed in other cell lines.

Animals↗

PubMed1986

New agents active against African swine fever virus.

Actinobolin, atropine, carrageenan, megalomycin C, suramin, and tetracenomycin C were tested for their activity against African swine fever virus replication. Both viral inhibitory potency and cytotoxicity were investigated. Megalomycin C, suramin, atropine, and carrageenan exhibited significant activity. Megalomycin C was the most active of the four agents with respect to the concentration of compound that blocked the formation of infectious virus by 50%. Suramin was the next most active agent in this respect, but because of its lower cytotoxicity, it had the most favorable therapeutic index.

African Swine Fever Virus↗

PubMed1986

Antirhinovirus compound 44,081 R.P. inhibits virus uncoating.

44,081 R.P., or 2-[(1,5,10,10a-tetrahydro-3H-thiazolo[3,4-b]isoquinolin- 3-ylidine)amino]-4-thiazole acetic acid, is a compound which selectively inhibits rhinovirus in cell cultures. The compound, which was unable to inactivate infectivity of virions, appeared to act prior to RNA and protein synthesis without affecting adsorption or penetration of virus in MRC5 cells. In contrast, it protected intracellular [5-3H]uridine-labeled virions against the effects of RNase treatment, indicating that inhibition of virus uncoating is the mode of action of 44 081 R.P.

Adsorption↗

PubMed1986

Specific proteins synthesized during the viral lytic cycle in vaccinia virus-infected HeLa cells: analysis by high-resolution, two-dimensional gel electrophoresis.

The proteins synthesized in vaccinia-infected HeLa cells have been analyzed at different times after infection by using two-dimensional gel electrophoresis. Vaccinia-infected cells present up to 198 polypeptides (138 acidic, isoelectric focusing; 60 basic, nonequilibrium pH gradient electrophoresis) not detected in control cells. Cells infected in the presence of cycloheximide show 81 additional polypeptides after cycloheximide removal, resulting in a total estimate of 279 proteins induced after vaccinia infection. The glycoproteins made at various times postinfection were also analyzed. At least 13 proteins labeled with [3H]glucosamine were detected in vaccinia-infected HeLa cells.

Cycloheximide↗

PubMed1986

Ultrastructural modifications of the cavities formed by folliculo-stellate cells in chicken adenohypophysis under septic shock conditions.

Effects of septic shock by repeated inoculations with Escherichia coli on the ultrastructure of the folliculo-stellate cells and cavities of the adenohypophysis of the chicken were investigated in order to determine the function of these cavities. The principal morphological modifications were dilation of the Golgi apparatus, endoplasmic reticulum and autophagic vacuoles, and necrosis phenomena in the stellate cells. The follicular cavities showed dilation, and there was heterogeneous dense material and granular elements in the follicular lumen. Based on results reported in the literature, the observations reported here are evidence of a "cleaning-role", for the removal of cell debris, when there is endocrine disfunction.

Animals↗

PubMed1985

Modification of membrane permeability during Semliki Forest virus infection.

Modification of membrane permeability has been analyzed in Semliki Forest virus (SFV)-infected cells by means of translation inhibitors not permeable to normal cells. A higher inhibition of protein synthesis in the infected cells is only observed with those antibiotics that do not easily pass the cell membrane, but not with others, permeable to cells, such as anisomycin, cycloheximide, trichodermin, etc. It does not, therefore, seem that the suggestion of M. A. Gray, K. J. Micklem, and C. A. Pasternak [Eur. J. Biochem. 135, 299-302, (1983)] that protein synthesis in virus-infected cells is more susceptible to translation inhibitors in general is correct. Both low- and high-molecular weight compounds enter the cell very early during SFV infection. This permeabilization is blocked by compounds known to increase the pH of coated vesicles, such as NH4Cl and chloroquine. Inhibition of energy production by means of N3Na and 2'-deoxyglucose also blocks this process. The optimal external pH for this early permeabilization is around 7-8. Acidic pH inhibits the entry of these impermeant antibiotics promoted by SFV. Analysis of 86Rb+ content in SFV-infected HeLa cells also indicates that a drastic decline in this cation takes place, in agreement with previous findings, but disagreeing with the previous results. A parallel between the decrease in this cation and the blockade of protein synthesis is apparent, throughout the course of infection. In addition to the early permeabilization that takes place during virus entry, increased entry of hygromycin B and alpha-sarcin also occurs in SFV-infected cells from 2 to 3 hr postinfection, but not when late viral replication is blocked by means of interferon treatment.

Ammonium Chloride↗

PubMed1985

Uridine 5'-diphosphate glucose analogues. Inhibitors of protein glycosylation that show antiviral activity.

A series of analogues of uridine 5'-diphosphate glucose and uridine 5'-diphosphate glucosamine have been synthesized by reaction of 2,3,4,6-tetra-O-benzyl-, 2,3,4,6-tetra-O-benzoyl-, 2,3,4,6-tetra-O-acetyl-, and 2,3,4,6-tetra-O-palmitoyl-alpha-D-glucopyranose and 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-alpha-D-glucopyranose with chlorosulfonyl isocyanate and 2',3'-O-isopropylideneuridine. Isopropylidene and acetyl groups of the resulting 5'-O-[[[[(alpha-D-glucopyranosyl)oxy]carbonyl]amino]sulfonyl] -2',3'-O-isopropylideneuridine derivatives were removed by reaction with a TFA/water (5:1) mixture and methanolic ammonia, respectively. The 5'-O-[[[[(2",3",4",6"-tetra-O-benzyl-and 2",3",4",6"-tetra-O-benzoyl-alpha-D-glucopyranosyl)oxy]carbonyl] amino]sulfonyl]-2',3'-O-isopropylideneuridine (13 and 19) and the corresponding deisopropylidenated derivatives showed antiviral activity as determined by the inhibition of the cytopathic effect induced by HSV-1 replication and by the plaque assay method. Compound 13 inhibited glycosylation of proteins in HSV-1 infected HeLa cells.

Antiviral Agents↗

PubMed1985

Synthesis and antiviral evaluation of nucleosides of 5-methylimidazole-4-carboxamide.

Due to the antiviral activity of certain 5-substituted imidazole nucleosides related to ribavirin, 5-methylimidazole-4-carboxamide nucleosides having beta-D-ribofuranosyl, 2-deoxy-beta- and -alpha-D-ribofuranosyl, and (2-hydroxyethoxy)methyl moieties have been prepared and tested as antiviral agents. 1-beta-D-Ribofuranosyl-5-methylimidazole-4-carboxamide was obtained by deacetylation of the corresponding tri-O-acetyl nucleoside 11 or by deacetylation and ammonolysis of the blocked ethyl 5-methylimidazole-4-carboxylate nucleoside 10, which was prepared from the stannic chloride catalyzed condensation of the trimethylsilyl derivative of ethyl 4(5)-methylimidazole-5(4)-carboxylate. Glycosylation of 4(5)-methylimidazole-5(4)-carboxamide with 3,5-di-O-p-toluoyl-2-deoxy-D-erythro-pentofuranosyl chloride via mercuric cyanide method provided an anomeric mixture of the blocked 5-methylimidazole-4-carboxamide deoxynucleoside 14 along with an anomeric mixture of the 4-methyl 5-carboxamide isomer 15. Separation of compound 14 into the corresponding beta and alpha anomers was achieved by conversion to the 3',5'-di-O-acetyl derivatives 17 and 18, which after chromatographic separation were deacetylated to give 1-(2-deoxy-beta-D-erythro-pentofuranosyl)-5-methylimidazole-4-carboxa mid e and its alpha anomer 20. 1-[(2-Hydroxyethoxy)methyl]-5-methylimidazole-4-carboxamide was prepared by alkylation of the imidazole 13 with (2-acetoxyethoxy)methyl bromide followed by treatment with methanolic ammonia. All these imidazole nucleosides were tested in HeLa cell cultures against type 1 herpes simplex and vesicular stomatitis viruses. The ribofuranosyl derivative 12 showed a significant activity against type 1 herpes simplex virus.

Antiviral Agents↗

PubMed1985

The regulation of translation in reovirus-infected cells.

The regulation of translation in reovirus-infected cells has been investigated by double-infection experiments. Different cell lines were able to translate uncapped encephalomyocarditis (EMC) virus mRNA and capped vesicular stomatitis virus (VSV) mRNAs both early and late during reovirus infection. These results are not fully in agreement with a previously suggested model in which, in the early phase of reovirus infection, only capped mRNAs are translated, whereas in the late phase the cells are modified to translate exclusively uncapped mRNAs. The observations that EMC virus and VSV shut down host protein synthesis more efficiently than reovirus translation in the late phase in double-infections indicate that competition for a message-discriminatory factor may not be involved in the shut-off of host protein synthesis in these animal virus-infected cells.

Animals↗

PubMed1985

Mildiomycin: a nucleoside antibiotic that inhibits protein synthesis.

Mildiomycin, a new nucleoside antibiotic, selectively inhibits protein synthesis in HeLa cells, and is less active in the inhibition of RNA or DNA synthesis. An increased inhibition of translation by mildiomycin is observed in cultured HeLa cells when they are permeabilized by encephalomyocarditis virus. This observation suggests that this antibiotic does not easily pass through the cell membrane, as occurs with other nucleoside and aminoglycoside antibiotics. The inhibition of translation is also observed in cell-free systems, such as endogenous protein synthesis in a rabbit reticulocyte lysate or the synthesis of polyphenylalanine directed by poly (U). Finally the mode of action of mildiomycin was investigated and the results suggest that the compound blocks the peptidyl-transferase center.

Animals↗

PubMed1984

Action of oligomycin on cultured mammalian cells. Permeabilization to translation inhibitors.

Oligomycin, an inhibitor of ATP synthesis, has been used as a model to study the effects of ATP depletion on macromolecular synthesis and modification of membrane permeability. Protein synthesis is totally blocked by the antibiotic, whereas RNA and DNA synthesis are less inhibited. Different concentrations of monovalent and divalent cations do not revert the inhibition of protein synthesis. Measurement of cellular ATP and 86Rb+ content indicate that the blockade of translation depends on the ATP content. A significant decrease in cellular ATP does not lead to the reduction of monovalent ions in the cell, although hyperpolarization of the cell membrane does take place. An increased membrane permeability to some inhibitors develops when the cells are hyperpolarized by oligomycin.

Adenosine Triphosphate↗

PubMed1984

Synthesis of heat-shock proteins in HeLa cells: inhibition by virus infection.

Incubation of HeLa cells at supraoptimal temperatures induces the synthesis of a class of proteins known as heat-shock or stress-response proteins. After restoration of cells to physiological temperatures heat-shock protein synthesis continues for several hours. Normal cellular translation eventually recovers even if cells are treated with actinomycin D, indicating that neither normal cellular mRNAs nor components of the translation machinery are irreversibly modified by heat treatment. The synthesis of heat-shock proteins after poliovirus infection is more resistant to inhibition than normal host proteins. Nevertheless, their synthesis is also inhibited in infected cells, even in cells treated with human interferon under which conditions viral RNA replication and viral translation are blocked. Translation of heat-shock proteins is also resistant to hypertonic shock indicating that their mRNAs bind ribosomes with high affinity.

Electrophoresis, Polyacrylamide Gel↗

PubMed1984

Screening for new compounds with antiherpes activity.

A number of compounds have been tested for antiherpes activity. Actinobolin, amicetin, carrageenan, laspartomycin, megalomycin C, pleuromutilin, suramin and tetracenomycin C showed significant protection of HeLa cell monolayers infected with herpes simplex virus type 1. The action of these new antiherpes compounds was compared with those antiherpes agents that have been described previously. Actinobolin, amicetin and tetracenomycin C were also active against viruses other than herpes simplex.

Antiviral Agents↗

PubMed1984

Action of human lymphoblastoid interferon on HeLa cells infected with RNA-containing animal viruses.

Protein synthesis in interferon-treated HeLa cells infected by different animal RNA viruses has been studied. Synthesis of vesicular stomatitis virus (VSV) proteins was not detected in cells treated with concentrations of HuIFN-alpha (Ly) above 10 IU/ml. No specific inhibition of glycosylation of the G protein was observed. In addition, inhibition of host protein synthesis in IFN-treated cells occurred when high multiplicities of VSV were used, even though no viral protein synthesis was detected. For other viruses, such as Newcastle disease virus, Semliki Forest virus, encephalomyocarditis virus and poliovirus, treatment of cells with interferon also led to inhibition of viral protein synthesis. However, influenza virus and reovirus protein synthesis in interferon-treated cells stayed at control levels. The finding of viral translation in influenza virus and reovirus-infected cells treated with interferon suggests that, at least for these two systems, the antiviral state is not mediated by the bulk inhibition of viral protein synthesis through the dsRNA-activated protein kinase, or the 2'-5' oligo(A) system.

Encephalomyocarditis virus↗

PubMed1984

Formation of non-infective herpesvirus particles in cultured cells treated with human interferon.

Treatment of HeLa cells with human lymphoblastoid interferon [HuIFN-alpha(Ly)] induced an antiviral state that rendered the cells refractory to infection by herpes simplex virus type 1 (HSV-1), and the yield of infectious HSV-1 was reduced by 98%. Analysis of the mechanism of the anti-herpes action of IFN indicated that no gross inhibition of viral protein synthesis took place and late proteins appeared, although the synthesis of some of them was partially inhibited. No differences were apparent between the glycoproteins or phosphoproteins synthesized in control and IFN-treated HSV-1-infected HeLa cells. No inhibition of the formation of new virus particles from IFN-treated cells was evident as assessed by electron microscopy and biochemical analyses, although their infectivity was drastically reduced. These virions exhibited some differences in their content of a few proteins as determined by PAGE. Studies on the second infection cycle with virions obtained from IFN-treated cells suggested that they attached and penetrated HeLa cells but that their development was impaired, since no viral protein synthesis was observed during the second infection. Altogether these results do not support the idea that the molecular mechanism of action of human IFN against HSV-1 is mediated via the 2'-5' A system, or by the inactivation of initiation factors. Rather, they focus the problem of the anti-herpes action of IFN at the level of formation of defective virions.

Glycoproteins↗

PubMed1984

Antiherpesvirus action of atropine.

The antimuscarinic compound atropine shows an antiherpesvirus effect as measured by the protection of the cell monolayer and the reduction of the formation of new infectious virus. Atropine at a concentration of 200 micrograms/ml blocks the production of new infectious herpes simplex virus-type 1 virions. At that concentration, it has almost no effect on cellular or viral protein synthesis even when atropine is present from the beginning of the infection. The glycosylation of viral proteins is almost totally blocked when atropine is added. Although the viral proteins are underglycosylated, the formation of new herpes simplex virus type 1 virions takes place. The virions formed in the presence of atropine are noninfectious, and their protein composition, as assessed by labeling with [35S]methionine, is similar to that of the control, except that they are not glycosylated.

Antiviral Agents↗

PubMed1984

pppA2'p5A' blocks vesicular stomatitis virus replication in intact cells.

pppA2'p5'A blocked the production of infectious vesicular stomatitis virus in HeLa cells. When this compound was present from the beginning of infection, a selective inhibitory effect was observed in viral protein synthesis. Thus, cellular translation was not affected even after 10 h of incubation with this compound, and the bulk of viral proteins was not synthesized. However, this effect was not observed with ATP, GTP, or the core A2'p5'A. The step blocked by pppA2'p5'A is located early during virus infection, but adsorption, entry, and virus uncoating seemed to be unaffected by this compound. Analysis of the antiviral spectrum of pppA2'p5'A indicated that it is active against poliovirus, encephalomyocarditis virus, and Semliki Forest virus and shows no effect against herpes simplex virus type 1 and adenovirus type 5.

Adenine Nucleotides↗