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Biomedical subjects

K Bienz

Publications and source records attributed to K Bienz.

At least 55 records · Page 3Linked to original sources
PubMed1983

Intracellular distribution of poliovirus proteins and the induction of virus-specific cytoplasmic structures.

In a susceptible cell, enteroviruses induce a vesiculated region (the "virus-induced vesicles") which is both the site of viral RNA synthesis as well as the site referred to morphologically, as the "cytopathic effect." Proteins of poliovirus (type I, Mahoney) were shown to migrate into the region of the virus-induced vesicles of infected HEp-2 cells. Five proteins (P2-5b, P3-4b, P3-6a, P3-7c, P3-9) were found to be associated with the vesicles themselves, either as intrinsic membrane protein (P3-9) or in a soluble form within the vesicles (P3-4b, P3-7c, and, partially, P3-6a) or bound to a DOC-resistant structure (P2-5b and a small amount of P3-6a). Partial inhibition of the cleavage of the viral polyprotein with ZnCl2 was used to alter the viral protein pattern within the cells. The data obtained indicate that P2-5b is the protein responsible for the formation of the virus-induced vesicles.

Carcinoma, Hepatocellular↗
PubMed1982

Poliovirus-induced inhibition of host RNA synthesis studied in isolated HEp-2 cell nuclei.

Nuclei isolated from uninfected HEp-2 cells synthesized RNA for 60 to 90 min. The individual RNA polymerase activities were determined by alpha-amanitin differential inhibition and the RNA products characterized by electron microscope (EM) autoradiography and sucrose gradient centrifugation. In nuclei prepared from poliovirus-infected cells, the capacity to synthesize RNA in vitro decreased with time after infection. RNA polymerase II activity (hnRNA synthesis) was preferentially inhibited more than was the polymerase I activity (rRNA synthesis). Poliovirus-infected cytoplasm (S-30) inhibited in vitro RNA synthesis in uninfected nuclei by selectively affecting the polymerase II activity. Selective inhibition of hnRNA synthesis by the crude extracts could be monitored by EM autoradiography directly. Determinations of individual RNA polymerase activities by differential alpha-amanitin inhibition were done only after treatment of the infected cytoplasm with micrococcal nuclease to abolish virus RNA replication. Selective inhibition of hnRNA synthesis depended on preincubation of the nuclei together with the infected cytoplasm, indicating that inhibitory substances from the infected cytoplasm entered the nuclei. Isolated nuclei therefore provide a useful system for studying the nature of the inhibitor(s) and of host RNA synthesis inhibition by picornaviruses.

Cell Line↗
PubMed1982

Accumulation of poliovirus proteins in the host cell nucleus.

Poliovirus (type 1, Mahoney) proteins were transported into the nuclei of HEp-2 cells, as demonstrated by means of electron microscopic autoradiography. Quantitative determinations of the proteins by electrophoresis showed that the relative amounts of precursor proteins (1a, 3b, 1b), of some of the intermediate polypeptides (3a, 3c, 5b, 2), and of one end product (VP1) were higher in the nucleus than in the cytoplasm. Other proteins (VPO, VP2, X, 4, 6a) were found in the same relative amounts in the nucleus as in the cytoplasm, whereas two proteins (VP3 and 6b) were excluded from the nucleus. The findings are discussed in view of the recently demonstrated inhibitory activity exerted by cytoplasmic extracts of poliovirus-infected cells on transcription in isolated nuclei of uninfected cells.

Cell Compartmentation↗
PubMed1980

Influence of poliovirus infection on S-phase and mitosis of the host cell.

Hep-2 cells were synchronized by a double thymidine block and infected with poliovirus type I (Mahoney) in hourly intervals after release from the second thymidine block. The S-phase is not prevented by a poliovirus infection but, with cells infected 0-4 hours after release, an increase of its duration is found. With an infection 5 hours and later after release, the duration of the S-phase is not different from that of an uninfected, synchronized control culture. DNA synthesis itself is slower early in S-phase and gets inhibited up to 75 per cent late in S-phase. All cultures show the first signs of a CPE 3.5 hours p.i. and, in spite of CPE, the cells continue to synthesize DNA. In infected cells a slightly higher peak of mitotic cells compared to control cultures is found. The time point of the mitotic peak is dependant of the time of infection and seems no longer controlled by the cell cycle. The mitotic indices are similar for all cultures infected at different times after release. When the cells are infected early after release CPE appears before mitosis and prevents the cells from entering mitosis. Cells which are infected towards the end of the S-phase finish mitosis normally before they exhibit characteristics of CPE. Extent and kinetics of poliovirus RNA synthesis and yield of virus progeny are not altered by the cell cycle.

Cell Cycle↗
PubMed1978

Differential inhibition of host cell RNA synthesis in several picornavirus-infected cell lines.

Patterns of cellular RNA synthesis during poliovirus (types 1,2 and 3) and mengovirus infections in HeLa, HEp-2, Vero and L-cells were investigated by means of high-resolution autoradiography, kinetics of 3H-uridine incorporation, and sucrose gradient centrifugation. Only mengovirus-infected L-cells showed an early and exponential inhibition of hnRNA and rRNA synthesis. The other cell lines tested, whether infected with polio- or mengovirus, exhibited a slowly and linearly decreasing cellular RNA synthesis, with hnRNA production suppressed completely, although somewhat later than in L-cells, and rRNA synthesis continuing at a gradually reduced rate during the entire viral growth cycle. Locations of cleavage steps of rRNA precursor molecules are discussed.

Autoradiography↗
PubMed1975

A method for distinction between RNA and DNA in aldehyde and osmiumtetroxide-fixed electron microscopic autoradiographs.

A simple method for distinction between RNA- and DNA-containing structures in aldehyde- and osmiumtextroxide-fixed electron microscopic autoradiographs (or ordinary thin sections) is described: the developer and the acetic acid used for processing autoradiographs extract selectively uranium acetate from DNA containing-structures which, after staining with lead citrate, leads to a characteristically 'bleached' appearance of the DNA.

Aldehydes↗
PubMed1973

Virus replication, cytopathology, and lysosomal enzyme response of mitotic and interphase Hep-2 cells infected with poliovirus.

Mitotic Hep-2 cells, selected by the PEL (colloidal silica) density gradient method and held in mitosis with Colcemid, are readily infected by poliovirus type I (Mahoney). They produce and release the same amount of virus as interphase, random-growing cells. In contrast to interphase cells, mitotic cells show no detectable virus-induced cytopathic effect at the light microscopy level and only slight alterations, consisting of small clusters of vacuoles, at the electron microscopy level. Mitotic cells contain the same total amount of lysosomal enzymes per cell as interphase cells, but they display no redistribution of lysosomal enzymes during the virus infection as interphase cells do. This supports the view that lysosomal enzyme redistribution is associated with the cytopathic effect in poliovirus infection but shows that virus synthesis and release is not dependent on either the cytopathic effect or lysosomal enzyme release. The possible reasons for the lack of cytopathic effect in mitotic cells are discussed.

Carcinoma↗