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Biomedical subjects

J Vilcek

Publications and source records attributed to J Vilcek.

At least 199 records · Page 11Linked to original sources
PubMed1976

Superinduction of interferon with metabolic inhibitors: possible mechanisms and practical applications.

Ten years have passed since cycloheximide was first shown to enhance endotoxin-induced production of interferon in mice, in the first demonstration of what was later called the superinduction of interferon. Various inhibitors of protein and RNA symthesis, as well as combinations of these inhibitors, have been shown to act as superinducing agents of interferon production stimulated by polyriboinosinic-polyribocytidylic acid. The evidence that superinduction is due to the suppression of a mechanism of post-transcriptional regulation of interferon synthesis is rather convincing. The notion (first proposed about six years ago) that this modification is caused by a protein "repressor" remains the most plausible, albeit still unproved, hypothesis. The availability of systems that translate with fidelity interferon messenger RNA isolated from induced cells should prove most useful in the elucidation of post-transcriptional control mechanisms of interferon synthesis and of interferon superinduction. Meanwhile, superinduction has become a useful tool for the production of large quantities of interferon. In particular, this technique has been successfully applied to the production of interferon from human diploid fibroblasts. The clinical potential of this material remains to be critically examined.

Animals↗
PubMed1975

Enhancement of human interferon production by neutral red and chloroquine: analysis of inhibition of protein degradation and macromolecular synthesis.

Two lysosomotrophic drugs, neutral red and chloroquine, enhance polyinosinic:polycytidylic acid-induced interferon production by a strain of diploid human fibroblasts (FS-4). Treatment of cells with neutral red or chloroquine between 2.5 and 3.5 h after induction increases interferon yields 16- to 64- and 4- to 16-fold, respectively, in the subsequent 20.5 h. The two drugs inhibit the rates of protein degradation and of RNA and protein synthesis. In addition, neutral red is a very potent inhibitor of uridine transport into cells. Normalized dose-effect curves show that interferon superinduction is correlated with the inhibition of macromolecular synthesis, but not with that of protein degradation. Treatment of cells with chloroquine at low concentration (25 mug/ml) for a prolonged period of time (24 h) caused approximately 40% reduction in the rate of protein degradation. The usual rapid shutoff of interferon production and the effectiveness of effectiveness of actinomycin D superinduction are not altered by this treatment. This strongly suggests that inhibition of intralysosomal protein degradation does not significantly contribute to interferon superinduction. Degradation of the rapidly and the slowly turning over proteins was unaffected by actinomycin D under conditions of treatment known to enhance interferon production. Treatment with cycloheximide (5 or 50 mug/ml for 5 h) inhibited the rate of degradation of the rapidly turning over component by 10% and the slow component by 30-40%, which suggests that the two components turn over by distinct cellular mechanisms.

Cells, Cultured↗
PubMed1975

Human interferon production: superinduction by 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole.

Polyinosinic.polycytidylic acid [poly(I.C)] induced production of interferon by a strain of diploid human fibroblasts (FS-4), measured between 5 and 24 hours from induction, is enhanced up to 128-fold by 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB), a reversible inhibitor of nuclear heterogeneous RNA synthesis. A normalized dose-effect plot shows a close correlation between the superinducing effect of DRB and inhibition of RNA synthesis. Cultures that contained DRB continue to produce interferon for up to 4 days. Removal of the drug at any time during this period leads to a prompt shutoff of interferon production.

Benzimidazoles↗
PubMed1975

Cell-free synthesis of human interferon.

With mRNA prepared from induced human fibroblasts biologically active human interferon was synthesized de novo in a cell-free extract from mouse cells. The identity of the antiviral activity as human interferon was demonstrated by its species and antigenic specificity.

Animals↗
PubMed1975

Two antigenically distinct species of human interferon.

Rabbit antisera prepared against interferon produced in human fibroblast cell cultures stimulated with poly(1).poly(C) neutralized the activity of interferon preparations produced in various human fibroblast cultures timulated either with poly(1)poly)C) or with viruses. However, these antisera showed no detectable neutralizing activity against interferon produced in cultures of human leukocytes. On the other hand, most rabbit antisera against the human leukocyte interferon were active in neutralizing both homologous interferon and fibroblast interferons. A preparation of antiserum against leukocyte interferon, active against both leukocyte and fibroblast interferons, was shown by affinity chromatography to have two distinct antibody populations, one of which was specific for the fibroblast interferon. We conclude that the heterologous neutralizing activity of sera from rabbits immunized with leukocyte interferon is liekly to be due to the presence of two antigenic species of interferon. The major antigenic species of leukocyte interferon preparations (designated "Le") is distinct from huamn fibroblast interferon. The minor species of leukocyte interferon ("F") is either identical with, or closely related to, interferon produced in human fibroblast cultures.

Animals↗
PubMed1975

Inhibition of interferon secretion by vinblastine.

The plant alkaloids vinblastine and colchicine are known to arrest cells in mitosis by virtue of their binding to spindle protein. These drugs are also capable of binding to microtubule protein and causing these structures to disaggregate into nonfunctional subunits (1, 2). Microtubular structures are thought to be involved in the secretory process of a number of proteins including insulin (7), collagen (4), and thyroid hormone (12). In this report we present our findings on the effects of these two drugs on the synthesis and secretion of interferon in a high producing human foreskin fibroblast strain (FS-4) (11).

Cell Line↗
PubMed1975

Immunologically specific production of interferon in cultures of rabbit blood lymphocytes: association with in vitro tests for cell-mediated immunity.

Lymphocytes of animals with delayed hypersensitivity produce mediators of cellular immunity when challenged in vitro with specific antigen. Among these are macrophage migration inhibitory factor (MIF) and interferon (IF). Nonspecific mitogens also induce the production of these lymphokines. In the following study leukocytes and column-purified lymphocytes of the same peripheral blood sample from tuberculin (purified protein derivatives [PPD])-sensitive rabbits were concurrently cultured in medium alone or with PPD. Supernatants of 1- and 4-day lymphocyte cultures were assayed for MIF. Supernatants of 1-, 2- to 4- and 5- to 7-day leukocyte cultures were assayed for IF by inhibition of cytopathic effect of vesicular stomatitis virus on rabbit kidney cultures. In the presence of PPD, normal lymphocytes did not produce MIF, but lymphocytes from sensitized animals did (8/8 animals), after 1 and 4 days of culture. Leukocytes from normal animals produced little or no IF when cultured with or without PPD. Leukocytes from sensitized animals cultured in medium alone produced little IF. However, when cultured with PPD they produced significant amounts of IF on day-1 (6/8 animals) and day-2 to day-4 (4/8) animals. There was no correlation between relative amounts of MIF and IF produced by cultures of respective cells from individual animals. Rabbit IF produced or released in vitro appeared in significant and maximum amounts by 24 h coincident with the time release of significant amounts of another mediator of cellular immunity, MIF.

Animals↗
PubMed1974

Increased interferon production in human cells irradiated with ultraviolet light.

Polyinosinate-polycytidylate [poly(I).poly(C)]-induced interferon production in cultures of human foreskin fibroblast strains was increased by ultraviolet irradiation of cells at the time of exposure to inducer or at 2 h after induction. Incubation of cells with interferon prior to induction (priming) and ultraviolet irradiation exerted a cooperative enhancing effect on interferon production. The resulting interferon yields were generally somewhat higher than the yields from cultures subjected to sequential treatment with cycloheximide and actinomycin D.

Journal Article↗
PubMed1974

Interferon induction in rabbit cells irradiated with UV light.

UV irradiation of a continuous line of rabbit kidney cells (RK13) was used as a tool for the study of the mechanism of interferon induction. Irradiation of cells prior to their exposure to Newcastle disease virus (NDV) resulted in a dose-dependent decrease in interferon production. The inhibition of total cellular RNA synthesis by UV irradiation in uninduced cultures was similar to the inactivation curve of interferon production in NDV-induced cultures. In contrast, the production of interferon with polyinosinate-polycytidylate (poly[I].poly [C]) paradoxically was enhanced in cells irradiated with a wide range of doses of UV. However, in cells stimulated with poly(I).poly(C) and "superinduced" by the sequential addition of cycloheximide and actinomycin D, the rate of inactivation of interferon production by UV light was similar to that observed with NDV. These results are not inconsistent with the idea that both poly(I).poly(C) and NDV stimulate the same interferon gene(s), but indicate that the mechanism controlling its expression may be different for each inducer.

Cell Line↗
PubMed1973

Stabilization of interferon messenger RNA activity by treatment of cells with metabolic inhibitors and lowering of the incubation temperature.

Interferon production was induced in a strain of human diploid foreskin cells with poly(I).poly(C). Cycloheximide was included in the culture medium at the time of addition of the inducer. Actinomycin D was added to the cultures 4 or 5 hr later, before the inhibition of protein synthesis was reversed at 6 hr. Thus, subsequent interferon synthesis had to be directed by messenger RNA synthesized before addition of actinomycin D. The amount of interferon produced after such treatment was about 50-fold greater than in cells induced with poly(I).poly(C) but not treated with inhibitors. Experiments using cordycepin suggested that in spite of the continued presence of the inducer the synthesis of the bulk of interferon messenger RNA was completed within the first 2 hr of exposure of cells to poly(I).poly(C) and cycloheximide. Transcription of interferon messenger RNA was apparently not affected when interferon synthesis was suppressed to various degrees by different inhibitors of protein synthesis, indicating the independence of transcription and translation. The high rate of interferon synthesis after the reversal of cycloheximide action was more sustained at 32 degrees than at 37 degrees . The rate of decrease of overall protein synthesis in cells treated with actinomycin D and then incubated either at 32 degrees or 37 degrees showed a similar dependence on incubation temperature, suggesting that the stability of messenger RNA (or of another actinomycin D-sensitive component required for protein synthesis) was greater at the lower temperature.

Carbon Radioisotopes↗