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J Vilcek

Publications and source records attributed to J Vilcek.

At least 217 records · Page 12Linked to original sources
PubMed1972

Production of high-titered interferon in cultures of human diploid cells.

The effect of incubation with interferon prior to the stimulation of interferon production (priming) and of sequential treatment with cycloheximide and actinomycin D (superinduction) on the interferon yield from polyinosinic-polycytidylic acid (poly I.poly C)-induced diploid human foreskin cell cultures (FS-3 strain) was studied. Suitable priming with interferon produced, on the average, about an eightfold increase over the control yield, with a greater increase noted on some occasions when the control interferon yield was very low. Under the optimal conditions carefully defined in our experiments, superinduction produced about a 100-fold increase over the average control yield, resulting in interferon yields of about 10,000 reference units from cultures containing about 10(6) cells. Combined superinduction and priming did not produce yields markedly higher than obtainable by superinduction alone. Essentially similar results were obtained in cultures of human embryonic kidney cells and in FS-3 cells stimulated with other double-stranded polynucleotide inducers. However, stimulation of cells with certain concentrations of a mixture of diethylaminoethyl-dextran and poly I.poly C altered the interferon response; the yield was considerably higher than in cells stimulated with poly I.poly C alone, but it could not be markedly increased further by superinduction.

Cell Line↗
PubMed1972

Suppression of the intracellular growth of Shigella flexneri in cell cultures by interferon preparations and polyinosinic-polycytidylic acid.

A strain of Shigella flexneri type 2a was found to multiply intracellularly in cultures of the diploid human cell strain FS-1 and in secondary rabbit kidney cells. When inoculated cultures were stained and observed under the light microscope, it appeared that the cytoplasm of infected cells became gradually filled with bacteria. Various preparations of human and rabbit interferon were found to suppress the intracellular bacterial growth in homologous cells. Polyinosinic-polycytidylic acid (poly I.poly C) had a similar inhibitory effect. Rabbit interferon preparations did not cause a significant suppression in human cells. Suppression of the bacterial growth could be demonstrated in two ways: (i) by showing that treatment with either homologous interferon or poly I.poly C reduced the proportion of infected cells determined by counting the total number of cells and the number of cells with 10 or more bacteria in several microscopic fields selected at random, or (ii) by showing that a suppression in (3)H-uridine incorporation by bacteria occurs in infected cultures treated with actinomycin D after incubation with interferon or poly I.poly C. (Uridine incorporation by the bacterium is insensitive to actinomycin D.) Treatment of cells with actinomycin D before incubation with interferon prevented the development of cellular resistance to bacterial infection. Interferon preparations did not have an inhibitory effect on the extracellular growth of S. flexneri in a broth culture. These findings show that the range of activity of the interferon system apparently extends to intracellularly growing bacteria.

Animals↗
PubMed1972

Control of interferon synthesis: effect of diethylaminoethyl-dextran on induction by polyinosinic-polycytidylic acid.

Interferon production in cultures of rabbit kidney cells (RKC) stimulated with 10 to 250 mug of polyinosinic-polycytidylic acid (poly I.poly C) per ml peaked at 3 to 4 hr after the exposure of cells to inducer and rapidly declined thereafter. On the other hand, RKC stimulated with poly I.poly C (10 or 2 mug/ml) in the presence of diethylaminoethyl (DEAE)-dextran (100 or 20 mug/ml, respectively) produced a protracted interferon response, with the release of interferon continuing for over 24 hr. The kinetics of interferon production in RKC stimulated with lower concentrations of the mixture of poly I.poly C and DEAE-dextran were similar to the response produced by poly I.poly C alone (10 to 250 mug/ml). Only the responses that terminated early were paradoxically enhanced by treatment with low doses of actinomycin D or with cycloheximide. Cells stimulated with 50 mug of poly I.poly C/ml showed hyporesponsiveness to a second interferon induction with poly I.poly C when restimulated 7 hr after primary induction. This hyporesponsiveness could be overcome by restimulating with higher concentrations of the poly I.poly C-DEAE-dextran complex. The results are compatible with the hypothesis that the early termination of interferon production and hyporesponsiveness to repeated induction with poly I.poly C are due to a cellular repressor exerting negative control on interferon synthesis, and that the increased cellular uptake of poly I.poly C in the presence of DEAE-dextran may effectively neutralize the repressor. These results also suggested that the often observed different kinetics and the varied effects of inhibitors of ribonucleic acid or protein synthesis on interferon responses in various cells and in cells stimulated with different inducers (such as with viruses as compared with polynucleotides) need not imply the existence of fundamentally different mechanisms of interferon production.

Animals↗
PubMed1971

Post-transcriptional control of interferon synthesis.

Low to moderate doses of cycloheximide had a stimulatory effect on interferon production in rabbit kidney cell cultures treated with double-stranded polyinosinate-polycytidylate (poly I:poly C). A very marked stimulation occurred in the presence of a dose of cycloheximide inhibiting amino acid incorporation into total cellular protein by about 75%. Higher doses of cycloheximide caused a shift in interferon release towards later intervals and a gradual decrease in the overall degree of stimulation. An even greater increase in the amount of interferon produced was observed if cells were treated with cycloheximide for only 3 to 4 hr immediately after their exposure to poly I:poly C. Under the latter conditions, a rapid burst of interferon production occurred after the reversal of cycloheximide action. Treatment with a high dose of actinomycin D before the reversal of cycloheximide action caused a further increase and a marked prolongation of interferon production. It is postulated that inhibitors of protein synthesis suppress the accumulation of a cellular regulatory protein (repressor) which interacts with the interferon messenger ribonucleic acid mRNA and thereby prevents its translation. Therefore, active interferon mRNA can apparently accumulate in rabbit kidney cells which, after exposure to poly I:poly C, are kept in the presence of an inhibitor of protein synthesis. Some of this accumulated interferon mRNA can be translated during a partial block of cellular protein synthesis, but its most efficient translation occurs after the reversal of the action of the protein synthesis inhibitor.

Animals↗
PubMed1971

Morphogenesis of rabbit fibroma virus. Correlation with pathogenesis of the skin lesion.

Rabbit fibroma virus injected into the dermis of adult rabbit skin evokes an inflammatory, then granulomatous and finally proliferative or tumoral response. About 1 week after injection, the grossly visible nodular lesion reaches its maximum size and regresses, becoming hemorrhagic and necrotic. Unlike vacciiia, the morphogenesis of the RFV has not been validated satisfactorily. The present study shows that RFV-infected cells contain all the evolutive forms that have been identified during the course of vaccinia virus replication. In addition, long, twisting, intracytoplasmic lamellated inclusions were found in infected cells. These lamellae were composed of linear arrays of elongated, electron-dense fibers. When the inclusion was sectioned in a plane perpendicular to the fiber, the latter was found to be covered by projections approximately 160 A long, spaced at intervals of approximately 80-90 A; when sectioned tangentially, the lamellae appeared to be composed of tubules. Evidence is presented showing the similarities between the subunit of the lamellated inclusion and the virus membrane. It seems likely, therefore, that the viral membrane is covered by closely packed tubules approximately 160 A long. The lambellar inclusion is thought to represent abnormal synthesis or excessive formation of viral membranes. In addition to lamellae, which probably indicate some defect in virogenesis, some infected cells contained viral membranes partially or completely encircling the host's cell constituents, or fragments of viral membrane instead of viral matrix. Furthermore, structures resembling virus nucleoid were lying free in the viral or cytoplasmic matrix. The course of viral morphogenesis was correlated with viral multiplication and the kinetics of interferon production at the site of viral inoculation in the rabbit skin.

Animals↗
PubMed1970

Interferon.

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Animals↗
PubMed1969

Influence of the rate of cell growth and cell density on interferon action in chick embryo cells.

Chick embryo cells became more sensitive to the action of interferon the longer they remained in culture. This phenomenon was found even before confluency had been reached. The relative insensitivity of newly seeded cells was not due to a loss of receptors. Cells synthesizing deoxyribonucleic acid (DNA) at a high rate were less sensitive to interferon action than cells synthesizing DNA at a low rate, but the inhibition of DNA synthesis had no effect on interferon action. An increase in the number of cells used for seeding resulted in an earlier appearance of increased sensitivity to interferon action. These results are discussed in relation to the induction process in animal cells.

Animals↗