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R Vrijsen

Publications and source records attributed to R Vrijsen.

At least 37 records · Page 2Linked to original sources
PubMed1989

Eclipse products of poliovirus after cold-synchronized infection of HeLa cells.

The particles derived from radioactively labeled poliovirus, in cold-synchronized infection of HeLa cells, were studied. After temperatures shift-up, radioactivity was transferred rapidly from the infecting virions (160 S) to 135 S, and from there more slowly to 110 S, a previously unreported eclipse product. Both the 135 and 110 S particles contained RNA, lacked VP4, and were H-antigenic. In the 135 S particles, part of the VP1 complement was lost; in addition to this, the VP2 polypeptide of the 110 S particles was cleaved in situ. The formation of eclipse products was insensitive to cycloheximide. Arildone totally blocked the formation of 135 S particles, but not their further processing.

Antigens, Viral↗
PubMed1989

In vitro differentiation of fat-storing cells parallels marked increase of collagen synthesis and secretion.

Fat-storing cells were isolated and purified from livers of normal adult rats and maintained in primary culture. By light and electron microscopy it was established that they underwent phenotypic changes into cells with the ultrastructural characteristics of myofibroblasts, between the third and sixth day in culture. These morphological changes were accompanied by a 2-fold increase of L-[3H]proline incorporation into secretory proteins and an 11-fold increase into secreted collagenase-sensitive proteins. In contrast, incorporation into cell layer-associated proteins and into cell layer-associated collagenase-sensitive proteins was not significantly elevated. Sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in combination with fluorography, demonstrated that the main collagen type secreted by the myofibroblast-like cells was collagen type I. Collagen types III and IV, and fibronectin were present in lesser amounts. The similarity between the well known in vivo alterations of fat-storing cells under pathological conditions and the spontaneous in vitro differentiation described in this study, makes primary cultures of fat-storing cells a valuable tool for studying their role in chronic liver disease.

Adipose Tissue↗
PubMed1988

Antiviral activity of flavones and potentiation by ascorbate.

We compared the anti-poliovirus activities of three flavones, quercetin, luteolin and 3-methylquercetin, which differ only at ring position 3. 3-Methylquercetin was the most potent compound. Quercetin exhibited antiviral activity only when protected against oxidative degradation by ascorbate. The antiviral activity of luteolin was comparable to that of ascorbate-stabilized quercetin.

Antiviral Agents↗
PubMed1987

A pH-dependent dissociation of poliovirus procapsids.

At pH 7.6-8.2, poliovirus procapsids are dissociated in the cold to 14 S subunits which exhibit the same antigenicity and ability to be reassembled to empty capsids as naturally occurring 14 S subunits. The dissociation of the procapsids at pH 8.2 follows exponential kinetics. At pH 8.4 or 8.5, the procapsids are converted to 80 S H-antigenic, empty capsids.

Capsid↗
PubMed1987

The poliovirus-induced shut-off of cellular protein synthesis persists in the presence of 3-methylquercetin, a flavonoid which blocks viral protein and RNA synthesis.

In poliovirus-infected cells, the viral protein and RNA synthesis were severely reduced, provided 3-methylquercetin was present between 1 and 2 h post-infection. Under these conditions, the virally induced host shut-off remained in effect. On the other hand, in uninfected HeLa cells, protein and RNA synthesis was inhibited only slightly by 3-methylquercetin. The inhibition of poliovirus cytopathogenicity in Vero cells by 3-methylquercetin exhibited a similar time dependence.

Animals↗
PubMed1986

Lycorine: a eukaryotic termination inhibitor?

The effect of the alkaloid lycorine on viral protein synthesis was studied in poliovirus-infected HeLa cells. The incorporation of [3H]leucine was inhibited by lycorine in a dose-dependent way, although lycorine never completely abolished translation. Using polyacrylamide gel electrophoresis, the viral proteins were identified as derived from the P1 (5' terminal), P2 (middle), or P3 (3' terminal) region of the poliovirus translation unit. The residual labeling of viral proteins in the presence of lycorine was mainly due to synthesis of P1 proteins and slightly less to P2 proteins, while virtually no P3-derived proteins were made. It is suggested that lycorine may act at the level of termination.

Amaryllidaceae Alkaloids↗
PubMed1986

Assembly factors in poliovirus morphogenesis.

Extracts of poliovirus-infected HeLa cells promoted the in vitro assembly of 14 S subunits into empty capsids antigenically indistinguishable from procapsids. When infected cells were treated with iodoacetamide, the extract lacked the assembly promoting activity. This activity was restored by the addition of heat-disrupted virions, but the empty capsids formed in this system were antigenically different from procapsids. This and other observations introduce a distinction between the "assembly promoting" and "antigenicity conferring" activities of infected-cell extracts.

Animals↗
PubMed1986

Relationship between poliovirus neutralization and aggregation.

The interaction of mono- and polyclonal neutralizing antibodies with poliovirus was studied. In all cases, neutralization was due to antibody-mediated virus aggregation, and the unpolymerized virions accounted for the residual infectivity. The effect of papain on previously neutralized virus was to deaggregate the virus to fully infective single virions. With some antibodies, the amount of aggregated virus regressed in the region of greatest antibody excess, even though the virus remained fully neutralized. Under these conditions, noninfective, unaggregated immune complexes were formed. A mutant resistant to one of the monoclonal antibodies was selected. The mutant virions were still bound but no longer aggregated or neutralized by the selecting antibodies.

Antibodies, Monoclonal↗
PubMed1985

Demonstration of human alpha-L-fucosidase polymorphism by means of monoclonal antibodies.

Conventional rabbit antibodies and mouse monoclonal antibodies were raised to alpha-L-fucosidase purified from human placenta. Four monoclonal antibodies were studied, of which only one (A) was able to immunoprecipitate the fucosidase activity completely. Two antibodies (B and C) precipitated 65% and one (D) 35% of the activity. The enzyme precipitated by the monoclonal antibodies remained fully active, whereas the enzyme precipitated by conventional antibodies was partly inactivated. As shown by the method of successive immunoprecipitations, the monoclonal antibodies B and C recognized the same set of placental fucosidase molecules, and D a subset thereof. The purified fucosidase also yielded two components after gel electrophoresis in nondenaturing conditions, and the slower component corresponded to the set recognized by antibodies B and C. The fucosidase extracted from different tissues and serum was studied by immunoprecipitation. In all cases, the enzyme was completely precipitated by monoclonal antibody A. Two patterns were found with B, C and D: either part of the activity was precipitated by these antibodies (leucocytes, placenta, brain, liver, spleen, thymus) or B, C and D failed to precipitate any of the enzyme (serum, heart, kidney, testes).

Animals↗
PubMed1985

Characterization and assembly of poliovirus-related 45 S particles.

Using detergents, 45 S particles could be extracted from poliovirus-infected Vero and human embryonic kidney monolayer cells, but not from HeLa suspension cells. They were composed of the capsid proteins VP0, VP1, and VP3, devoid of RNA, and extremely sensitive to heat or to a slightly alkaline pH. The 45 S particles possessed neutralization epitopes of the N1 and N2 classes, as well as a VP3-linked epitope. The N2 epitopes were lost upon denaturation. In the presence of cell extracts 45 S particles were, like 14 S subunits, assembled to 71 S empty capsids expressing the N1 and N2 epitopes.

Animals↗
PubMed1985

Stabilization by host cell components and Mg2+ of the neutralization epitopes of poliovirus.

When type 1 poliovirions were extracted from infected HeLa cells and heated at 56 degrees C in the presence of 1 mM-Mg2+, RNA-free, pluri-antigenic particles were formed. These particles possessed neutralization epitopes as well as epitopes associated with H antigen and with the isolated capsid protein VP3. The heating caused the formation of exclusively H antigenic particles when the Mg2+ concentration was 10(-4) M or lower, or when the virus was further purified in order to remove remaining cellular components. The ability of purified virus to form pluri-antigenic particles upon heating could be restored by incubation at 37 degrees C with infected cell extract.

Antibodies, Monoclonal↗
PubMed1984

In vitro assembly of poliovirus empty capsids: antigenic consequences and immunological assay of the morphopoietic factor.

The assembly of poliovirus 14 S particles into empty capsids was studied without cell extract (self-assembly) and in extracts of infected or uninfected HeLa cells. The products were analyzed using monoclonal antibodies specific for N1, N2, or H epitopes. The empty capsids formed in infected cell extract, and only those, possessed N2 epitopes like the procapsids formed in vivo, thus showing that a virally encoded or induced factor determines the antigenicity of the assembly product. Based on this observation, a simple immunological assay for the activity of the morphopoietic factor is presented. This factor is shown to lack serotype specificity.

Antibodies, Monoclonal↗
PubMed1984

Intertypic cross-reactions of nonneutralizing, monoclonal poliovirus antibodies.

Quantitative data are presented on (i) the intertypic cross-reactions of polyclonal, guinea pig antibodies directed against the N or H antigen of type 1 poliovirus and (ii) a set of five nonneutralizing, mouse hybridoma antibodies raised against N antigen or a mixture of capsid polypeptides VP1, VP2, and VP3. Three of these antibodies recognize H antigen and VP1, the fourth H antigen only, and the fifth VP3 only. The antibodies recognize either only homotypic antigens or the antigens of the three serotypes.

Animals↗
PubMed1983

A simple quantitative protein A micro-immunoprecipitation method; assay of antibodies to the N and H antigens of poliovirus.

Staphylococcus aureus (Cowan strain I) was used to absorb immune complexes from antiserum to poliovirus to which labeled N or H poliovirus antigens had been added, and the radioactivity in the pelleted organisms and in the supernatant was measured. Excellent agreement was obtained between values calculated separately from the pellet and supernatant readings, validating the use of supernatant measurements from a microtitration plate method.

Animals↗
PubMed1983

Epitope evolution in poliovirus maturation.

Eight monoclonal antibodies specific for native (N) poliovirus antigen all recognized empty capsids extracted from infected HeLa cells; only three of them recognized 14S particles. The facts point to the existence of two different epitopes N1 and N2, only one of which (N1) is present on 14S particles (these observations confirm and extend findings by EMINI et al). Another epitope of 14S particles is recognized by antibodies to heated (H) poliovirus antigen. Infected cell extract-catalyzed polymerization of 14S particles yielded mainly empty capsids carrying the N1 and N2, but no H epitopes.

Animals↗