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Biomedical subjects

K Koschel

Publications and source records attributed to K Koschel.

52 records · Page 3Linked to original sources
PubMed1975

Virus-specific proteins associated with the replication complex of poliovirus RNA.

The poliovirus replication complex was isolated and purified from infected HeLa S3 cells. Preparations with RNA-dependent RNA polymerase activity were concentrated 200- and 1000-fold with respect to the original virus and total protein content. The enzyme activity was found to be associated with the proteins NCVPI, 2, 3, 4, (5), 6 and VPl/NCVPx. The structural proteins VP2, 3 and 4 were not present. Addition of cycloheximide to infected cells resulted in a decrease in the in vitro polymerase activity and a loss in NCVPI content. Treatment of the infected cells with toloylsulphonyl-phenylalanine chloromethyl ketone (TPCK) and iodoacetamide (IAA) led to an inhibition of in vivo RNA synthesis. The 750 g supernatant fluids obtained from extracts of these cells were able to block RNA synthesis in vitro. Electrophoretic profiles of the respective protein compositions indicate that large virus precursor proteins are responsible for the inhibition of poliovirus RNA synthesis in vivo and in vitro.

Cycloheximide↗
PubMed1974

Poliovirus infection and poly(A) sequences of cytoplasmic cellular RNA.

The influence of polio infection on Poly(A) sequences of cellular cytoplasmic RNA was investigated. In the presence of guanidine, cellular protein synthesis was still shut off after poliovirus infection, although there was no viral RNA synthesis. The Poly(A) of these cells was unchanged with respect to quantity, size, and linkage to cellular cytoplasmic RNA. This finding strongly suggests that the shut off of cellular protein synthesis is not caused by a change of the Poly(A) sequences of cellular mRNA.

Adenosine↗
PubMed1974

Reversible inhibition of poliovirus RNA synthesis in vivo and in vitro by viral products.

In poliovirus-infected HeLa-S3 cells, the protease inhibitors tolylsulfonyl-phenylalanyl chloromethyl ketone and iodoacetamide cause an accumulation of large precursor proteins, and they block viral RNA synthesis most probably via these products. Viral RNA polymerase activity can, however, be extracted by detergent containing buffer (Tris/Nonidet P-40, deoxycholate) from the inhibited cells. Only cytoplasmic extracts from infected cells treated with tolylsulfonyl-phenylalanyl chloromethyl ketone or iodoacetamide contain a protein which inhibits the in vitro polymerase reaction.

Acetamides↗
PubMed1971

Effect of inactivation by hydroxylamine on early functions of poliovirus.

Evidence is presented that poliovirus particles with a single lethal hit by hydroxylamine do not induce in host cells either inhibition of cellular protein synthesis or viral ribonucleic acid (RNA) replication. The RNA of these viruses is not replicated even if the cells are simultaneously infected with both active and inactivated viruses. The damaged viral RNA seems to have lost both its template function and its function in the translation of normal viral proteins.

Amino Acids↗
PubMedDate not supplied

Does diethylstilbestrol (DES) change the stress fiber organization in C6 rat glioma cells?

C6 Rat glioma cells acquire an astrocyte-like morphology (cytoplasmic shrinking) after exposure to beta-adrenergic compounds (e.g., isoproterenol) in serum-free medium. This morphological response is mediated by elevation of the intracellular cAMP level and possibly by activation of a kinase phosphorylating and inactivating the myosin-L-kinase in analogy to observations with smooth muscle cells. The result is a disturbance of the stress fiber function, which depends on a cooperation between actin and myosin. Diethylstilbestrol (DES) induces an identical morphological response in these cells under serum-free conditions. However, under the influence of DES no increase of the cAMP level was observed. In addition, at concentrations not inducing these morphological responses, DES inhibits the isoproterenol-induced effect when administered simultaneously or prior to the beta-receptor agonist. DES does not inhibit the isoproterenol-mediated morphological response when added after isoproterenol treatment. Furthermore, if serum is added to cells showing the isoproterenol- or DES-mediated astrocyte-like morphology (DES or isoproterenol present all the time) the cells regain their normal fibroblast-like morphology within 30 min. In view of these results the question arises whether DES interferes with myosin-L-chain phosphorylation or whether it directly interacts with the cytoskeleton stress fiber components, as cytochalasin B1 does. Thus it remains to be established whether the observed effects are related to the estrogenic activity of DES. Similar effects were observed with Syrian hamster embryo fibroblasts under the influence of DES and the naturally occurring steroid estrogen 17-beta-estradiol.

Animals↗