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The effects of cycloheximide on the biosynthesis and secretion of proteoglycans by chondrocytes in culture.

Proteoglycans synthesized by rat chondrosarcoma cells in culture are secreted into the culture medium through a pericellular matrix. The appearance of [35S]sulphate in secreted proteoglycan after a 5 min pulse was rapid (half-time, t 1/2 less than 10 min), but that of [3H]serine into proteoglycan measured after a 15 min pulse was much slower (t 1/2 120 min). The incorporation of [3H]serine into secreted protein was immediately inhibited by 1 mM-cycloheximide, but the incorporation of [35S]sulphate into proteoglycans was only inhibited gradually(t 1/2 79 min), suggesting the presence of a large intracellular pool of proteoglycan that did not carry sulphated glycosaminoglycans. Cultures were pulsed with [3H]serine and [35S]sulphate and chased for up to 6 h in the presence of 1 mM-cycloheximide. Analysis showed that cycloheximide-chased cells secreted less than 50% of the [3H]serine in proteoglycan of control cultures and the rate of incorporation into secreted proteoglycan was decreased (from t 1/2 120 min to t 1/2 80 min). Under these conditions cycloheximide interfered with the flow of proteoglycan protein core along the route of intracellular synthesis leading to secretion, as well as inhibiting further protein core synthesis. The results suggested that the newly synthesized protein core of proteoglycan passes through an intracellular pool for about 70-90 min before the chondroitin sulphate chains are synthesized on it, and it is then rapidly secreted from the cell. Proteoglycan produced by cultures incubated in the presence of cycloheximide and labelled with [35S]sulphate showed an increase with time of both the average proteoglycan size and the length of the constituent chondroitin sulphate chain. However, the proportion of synthesized proteoglycans able to form stable aggregates did not alter.

Animals↗

Evaluation of selective media for Campylobacter isolation when cycloheximide is replaced with amphotericin B.

AIMS: Laboratory media for the isolation of Campylobacter usually contain various selective agents, designed to allow these bacteria to grow whilst suppressing that of other organisms. For example, cycloheximide has often been incorporated into Campylobacter media to inhibit the growth of fungi. The production and availability of cycloheximide, however, has recently decreased due to concerns relating to its potential toxicity for mammalian cells and the compound has also become more expensive as a result. An alternative antifungal agent is necessary, and to address this, the effect of using amphotericin B in place of cycloheximide in Campylobacter selective broths and agars was examined. METHODS AND RESULTS: The growth of Campylobacter strains and the suppression of potential competitor organisms in selective broths or on selective agars containing either amphotericin B or cycloheximide was quantified, using pure microbial cultures. The results were then confirmed by testing food and water samples that contained high levels of micro-organisms, including Campylobacter. CONCLUSIONS: The results of this study indicate that amphotericin B is a suitable replacement for cycloheximide in Campylobacter selective media.

Amphotericin B↗

Cycloheximide resistance can be mediated through either ribosomal subunit.

Two cycloheximide-resistant mutants of Tetrahymena thermophila were analyzed to determine the site of their cycloheximide resistance. The mutations in both strains had been previously shown to be genetically dominant and located at separate loci (denoted Chx-A and Chx-B). Strains carrying these mutations were readily distinguished by the extent to which they were resistant to the drug. The homozygous double mutant was more resistant than either single mutant. Cell-free extracts of wild type and of the three mutant strains, assayed for protein synthetic activity by both runoff of natural mRNA and poly(U)-dependent phenylalanine polymerization, demonstrated that in vitro the mutants were all more resistant than the wild type. Further fractionation of the cell-free systems into ribosomes and supernates localized cycloheximide resistance to the ribosome for both Chx-A and Chx-B homozygotes. Ribosome dissociation and pairwise subunit mixing in the in vitro system indicated that ribosome resistance was conferred by the 60S subunit from one strain whereas resistance in the other strain was mediated through the 40S subunit. This was further confirmed by reconstruction of all four cycloheximide-resistance "phenotypes" by mixing ribosomal subunits from appropriate strains. This finding suggests that the mechanisms by which these mutations confer resistance to cycloheximide are different.

Animals↗

Transcription of thrombomodulin mRNA in mouse hemangioma cells is increased by cycloheximide and thrombin.

We have measured mRNA levels for thrombomodulin, an endothelial membrane cofactor for the activation of protein C by thrombin, in a mouse hemangioma cell line. Cycloheximide, an inhibitor of protein synthesis, increased levels of thrombomodulin mRNA, as measured in an S1 nuclease protection assay, to 2.5-4.0 times control levels. Thrombomodulin transcription in response to cycloheximide treatment, as determined by nuclear run-on analysis, was 3.9 +/- 1.3 (mean +/- SD) times that found in untreated cells. Thrombin also increased thrombomodulin mRNA levels to 151 +/- 21% (mean +/- SD) of control levels after 2 hr. Transcription increased in response to thrombin by 2.1- to 7.3-fold. The combination of thrombin and cycloheximide had no additive effect on thrombomodulin mRNA levels. Thrombin treatment of hemangioma cells also caused an increase in thrombomodulin protein synthesis to 142 +/- 17% (mean +/- SD) of control levels as determined by immunoprecipitation of [32S]methionine-labeled thrombomodulin. We conclude that thrombomodulin expression is determined in part by the rate of transcription and that thrombomodulin mRNA levels in hemangioma cells are increased by treatment with cycloheximide or thrombin. The increased transcription in response to cycloheximide suggests the existence of a labile protein repressor of thrombomodulin transcription.

Animals↗

Centrosome duplication continues in cycloheximide-treated Xenopus blastulae in the absence of a detectable cell cycle.

Cycloheximide (500 micrograms/ml) rapidly arrests cleavage, spindle assembly, and cycles of an M-phase-specific histone kinase in early Xenopus blastulae. 2 h after cycloheximide addition, most cells contained two microtubule asters radiating from perinuclear microtubule organizing centers (MTOCs). In contrast, blastomeres treated with cycloheximide for longer periods (3-6 h) contained numerous microtubule asters and MTOCs. Immunofluorescence with an anticentrosome serum and EM demonstrated that the MTOCs in cycloheximide-treated cells were typical centrosomes, containing centrioles and pericentriolar material. We conclude that centrosome duplication continues in cycloheximide-treated Xenopus blastulae in the absence of a detectable cell cycle. In addition, these observations suggest that Xenopus embryos contain sufficient material to assemble 1,000-2,000 centrosomes in the absence of normal protein synthesis.

Animals↗

Vitamin B12 and the macromolecular composition of Euglena. 3. Effect of cycloheximide on the recovery from B12-induced unbalanced growth.

When cycloheximide is added to (B12)-deficient cultures before or after replenishment of the cells with B(12), reversion of these cells is inhibited. This inhibition is not caused by interference of the inhibitor in the uptake of B(12) as measured by division kinetics. Cycloheximide does not inhibit the initial increase in the rate of DNA synthesis caused by B(12) replenishment, but within 30-45 min the rate decreases and DNA synthesis ceases. Cycloheximide added to replenished deficient cells after completion of DNA duplication inhibits cell division. The total cellular protein and RNA in replenished cells treated with cycloheximide does not change. B(12) added to deficient cells does not stimulate the incorporation of [(14)C]leucine into protein during resumption and completion of DNA duplication. However, there is a large increase in [(14)C]leucine incorporation into the protein of these cells soon after completion of DNA duplication and before resumption of cell division. The addition of cycloheximide to B(12)-replenished or to nonreplenished deficient cells rapidly inhibits the incorporation. We suggest that the addition of B(12) accelerates the rate of DNA synthesis in the deficient cells and that possibly no new protein synthesis is required except for mitosis. However, protein synthesis is needed for continuous DNA synthesis.

Carbon Radioisotopes↗

Character of the stimulatory response of uridine kinase in rat livers to cycloheximide treatment.

Administration of cycloheximde to adult rats resulted in the enhancement of uridine kinase activity in the liver. The increase of enzyme activity was not affected by adrenal secretion or uptake of food. Actinomycin D, hydroxyurea and puromycin injected simultaneously with cycloheximide depressed the increase of enzyme activity. On the contrary, administration of 5-azacytidine following cycloheximide resulted in further enhancement of uridine kinase. While the half-time of template RNA for uridine kinase in control rat livers was 24 h, for cycloheximide-stimulated enzyme it was about 11 h. At higher dose levels cycloheximide leads to an increased incorporation of both uridine and orotic acid into liver RNA; however, this effect was not observed in the starved animals. The mechanism of action of cycloheximide is briefly mentioned.

Animals↗

Cycloheximide causes increased accumulation of translatable mRNA for tyrosine aminotransferase and tryptophan oxygenase in livers of cortisol-treated rats.

Messenger RNA activities for two cortisol-inducible enzymes, tyrosine aminotransferase and tryptophan oxygenase, have been determined by translation in a wheat germ system. The effects of cycloheximide on the two mRNA activities have been evaluated. Cortisol leads to an increase of the translatable mRNAs for tyrosine aminotransferase and tryptophan oxygenase with a maximum at approximately 6 h. Cycloheximide was administered 4 h after treatment with cortisol; 2 h later, the activities of tyrosine aminotransferase and tryptophan oxygenase mRNA had increased five-fold and two-fold, respectively, compared to the activities reached with cortisol alone. Thereafter the amount of the two translatable mRNAs declined, though 14 h after cortisol administration the mRNA activities were still several fold higher than in control animals. Application of alpha-amanitin together with cycloheximide did not prevent an increased accumulation of specific translatable mRNAs. The increase in tyrosine aminotransferase and tryptophan oxygenase activity by cortisol was immediately blocked by cycloheximide. Whereas tryptophan oxygenase activity rapidly declined after cycloheximide application, tyrosine aminotransferase activity remained at the same level. Approximately 4 h thereafter, both enzyme activities increased again.

Amanitins↗

Cycloheximide induces accumulation of vasoactive intestinal peptide (VIP) binding sites at the cell surface of a human colonic adenocarcinoma cell line (HT29-D4). Evidence for the presence of an intracellular pool of VIP receptors.

Incubation of monolayers of HT29-D4 cells (a clone of the human colonic adenocarcinoma cell line HT29) in the presence of 17.5 microM cycloheximide resulted in an increase in the number of vasoactive intestinal peptide (VIP) binding sites at the cell surface without any change in the affinity of receptor for its ligand. The increase in 125I-VIP-binding capacity was dose-dependent between 0.35 microM and 17.5 microM cycloheximide and was correlated with the inhibition of protein biosynthesis. At higher concentrations of drug (17.5-100 microM) a plateau corresponding to a twofold increase in VIP-binding capacity was reached independently of the extent of protein synthesis inhibition. We found that VIP receptors of HT29-D4 cells with such an enhanced binding capacity behaved like those of control cells with respect to receptor internalization and recycling (i.e. the cycle of occupied receptors was insensitive to cycloheximide). After inactivation of 90% of cell-surface VIP receptors by alpha-chymotrypsin, we observed a biphasic kinetic of reappearance of VIP-binding sites. 40% of VIP-binding sites reappeared very quickly (less than 5 min) and 100% within 17 h. The fast recovery of VIP receptors was probably due to the deployment of new binding sites from an intracellular pool. The rate and extent of recovery of these receptors were similar in control cells and in cycloheximide-treated cells. However, the slow recovery was inhibited in cycloheximide-treated cells probably because a pool of immature receptors was depleted by the drug before the alpha-chymotrypsin treatment. Our data are consistent with the existence of two different intracellular pathways of occupied and unoccupied VIP receptors.

Adenocarcinoma↗

Prolonged infusion of cycloheximide does not block mossy fiber sprouting in a model of temporal lobe epilepsy.

PURPOSE: The role of protein synthesis in mossy fiber sprouting is unclear. Conflicting reports exist on whether a single dose of the protein synthesis-blocker cycloheximide administered around the time of an epileptogenic injury can block the eventual development of mossy fiber sprouting. METHODS: In rats, osmotic minipumps and cannulae were implanted to deliver 8 mg/ml cycloheximide to one dentate gyrus and vehicle to the other. This method has been used to block protein synthesis in the infused region for up to 5 days with minimal neurotoxic effects (Taha and Stryker, Neuron 2002;34:425-36). After 2 days of infusion, rats were treated with pilocarpine to induce status epilepticus. Pumps were removed 3 days later. Thirty days after pilocarpine treatment, rats were perfused, and hippocampal sections were processed for Timm staining. RESULTS: Timm staining revealed aberrant mossy fiber sprouting in the inner molecular layer regardless of whether hippocampi were treated with cycloheximide or vehicle. Cycloheximide-treated hippocampi displayed more aberrant Timm staining and more tissue damage around the infusion site than did vehicle-treated hippocampi. CONCLUSIONS: Prolonged infusion of cycloheximide, spanning the period of pilocarpine treatment, did not block mossy fiber sprouting. This finding suggests that protein-dependent mechanisms around the time of an epileptogenic injury are not necessary for the eventual development of synaptic reorganization.

Animals↗

Drastic alteration of cycloheximide sensitivity by substitution of one amino acid in the L41 ribosomal protein of yeasts.

Cycloheximide is one of the antibiotics that inhibit protein synthesis in most eukaryotic cells. We have found that a yeast, Candida maltosa, is resistant to the drug because it possesses a cycloheximide-resistant ribosome, and we have isolated the gene responsible for this. In this study, we sequenced this gene and found that the gene encodes a protein homologous to the L41 ribosomal protein of Saccharomyces cerevisiae, whose amino acid sequence has already been reported. Two genes for L41 protein, named L41a and L41b, independently present in the genome of S. cerevisiae, were isolated. L41-related genes were also isolated from a few other yeast species. Each of these genes has an intron at the same site of the open reading frame. Comparison of their deduced amino acid sequences and their ability to confer cycloheximide resistance to S. cerevisiae, when introduced in a high-copy-number plasmid, suggested that the 56th amino acid residue of the L41 protein determines the sensitivity of the ribosome to cycloheximide; the amino acid is glutamine in the resistant ribosome, whereas that in the sensitive ribosome is proline. This was confirmed by constructing a cycloheximide-resistant strain of S. cerevisiae having a disrupted L41a gene and an L41b gene with a substitution of the glutamine codon for the proline codon.

Amino Acid Sequence↗

A ction of cycloheximide on Zygosaccharomyces soja.

Tsukada, Yoji (Kyoto University, Kyoto, Japan), Tsunetake Sugimori, Kazutami Imai, and Hideo Katagiri. Action of cycloheximide on Zygosaccharomyces soja. J. Bacteriol. 83:70-75. 1962.-Cycloheximide is known to inhibit the growth of some species of Saccharomyces and other fungi. A new type of action of this antibiotic, with Zygosaccharomyces soja as the test organism, is described in this paper. Growth of Z. soja was completely inhibited under aerobic conditions by cycloheximide in concentrations of more than 5 mug per ml of culture solution. Continued shaking of the culture for more than 96 hr in the presence of an inhibitory amount of cycloheximide restored growth, accompanied by the excretion of riboflavin to the extent of 30 mug per ml of culture solution. In the cells recovering from cycloheximide inhibition, the type of glucose metabolism differed from that in the mother strain; a respiratory quotient of 4 with the mother strain fell to 1 in the progeny. Glucose metabolism (O(2) uptake and CO(2) evolution) by resting cells was investigated, and it was concluded that inhibition of glycolysis was not significant. This was verified by comparing various dehydrogenase activities in the cell-free extract. There were essentially no differences between riboflavin-forming and nonriboflavin-forming cells. The presence of the hexose monophosphate shunt was deduced from the fact that glucose-6-phosphate dehydrogenase activity was the strongest of the various dehydrogenase activities.

Anti-Bacterial Agents↗

Cultivation of Chlamydia trachomatis in cycloheximide-treated mccoy cells.

An isolation technique for Chlamydia trachomatis using McCoy cells is described. In contrast to earlier techniques employing such cells, no pretreatment of the cells was used. The glutarimide antibiotic cycloheximide was added to the culture medium used for incubating the cells after infection. Cycloheximide was used at concentrations that depressed, but did not completely inhibit, the metabolism of the eucaryotic host cells. In studies on different immunotypes of C. trachomatis cultured in the yolk sac of embryonated hen eggs, the cycloheximide technique was compared with a method using pretreatment of cells with 5-iodo-2-deoxyuridine. The cycloheximide method gave greater numbers of inclusion-forming units per cover slip for all the immunotypes of trachoma-inclusion conjunctivitis agents tested, i.e., A through I. In a study of 194 cervical and urethral specimens from women, cycloheximide treatment of McCoy cells was found to be more efficient than 5-iodo-2-deoxyuridine treatment for the isolation of C. trachomatis.

Cell Line↗

Selective inhibition of reovirus ribonucleic acid synthesis by cycloheximide.

Cycloheximide, at a concentration of 10 mug/ml, rapidly blocked protein synthesis in L cells infected with reovirus. When the drug was added before 5 hr postinfection, synthesis of both single- and double-stranded varieties of virus-specific ribonucleic acid (RNA), which normally commences between 6 and 7 hr after infection, was blocked. When the cycloheximide was added at 9 hr after infection, uptake of uridine-H(3) into RNA, for the succeeding 6 hr at least, was similar to that of an infected culture without the drug. This latter uptake of uridine-H(3) in the presence of cycloheximide was largely into single-stranded RNA, since double-stranded RNA synthesis was rapidly and markedly inhibited by the cycloheximide. Single-stranded RNA formed in the presence of cycloheximide was found not to be a precursor of viral progeny, double-stranded RNA. Synthesis of double-stranded RNA in the infected cell probably requires prior synthesis of a new protein, which has a rapid rate of turnover. The possibility that formation of single-stranded RNA is preceded by synthesis of a second new protein is discussed.

Animals↗

Replication of measles virus: continued synthesis of nucleocapsid RNA and increased synthesis of mRNA in the presence of cycloheximide.

The effect of cycloheximide on virus specific RNA synthesis in Vero cells infected with either wild-strain (Edmonston) or subacute sclerosing panencephalitis strain measles virus was investigated. At 3 days postinfection, cells treated with cycloheximide (2.6 x 10(-4) M) and then exposed to [(3)H]uridine showed a marked increase in labeled virus-specific RNA. A major portion of this incremental labeled RNA was putative viral mRNA which sedimented at 16, 22, and 30S. Five distinct classes of polyribosomes, which were not evident in untreated cells, were found in cycloheximide-treated cells and each contained similar species of virus-specific RNA. Viral nucleocapsid RNA, 50 and 18S, was synthesized and encapsidated in the presence of cycloheximide. The latter observation is in apparent contrast to reports that cycloheximide inhibits replication of RNA of classical paramyxoviruses, and may indicate that mechanisms for replicating RNA of measles virus are different from those for replicating RNA of paramyxoviruses.

Animals↗

DNA synthesis in polyoma virus infection. III. Mechanism of inhibition of viral DNA replication by cycloheximide.

The formation of viral DNA was inhibited in polyoma virus-infected cells in which protein synthesis had been blocked by cycloheximide. The present studies show the following. (i) The pool of replicating viral DNA molecules was reduced in cycloheximide-treated cells by an amount consistent with inhibition of [3-H]thymidine incorporation into viral DNA, whereas the rate of turnover of the replicating population was not affected. (ii) The rate of conversion of replicating molecules into closed-circular DNA was not affected by cycloheximide. (iii) The rate of elongation of nascent viral DNA fragments into strands of unit genome length was unaffected by cycloheximide. It is concluded that viral DNA synthesis is inhibited in the absence of protein synthesis exclusively at the level of initiation of new rounds of genome replication. Replicating molecules already initiated at the time of addition of cycloheximide matured into progeny closed-circular DNA at a normal rate.

Animals↗

Irreversible effects of cycloheximide during the early period of vaccinia virus replicaon.

The presence of cycloheximide, an inhibitor of protein synthesis, during the period 30 to 60 min after vaccinia infection produced an irreversible block in virus replication. In contrast (i) cycloheximide given at earlier or later times, even for prolonged periods, did not prevent continuation of the infectious cycle after removal of the drug, and (ii) treatment with cycloheximide during the first 2 hr did not prevent virus growth when the early stages of replication proceeded more slowly due to infection with a low multiplicity of virus. These findings were interpreted as an indication that protein synthesis is required at a critical time in the virus growth cycle. Under the conditions in which brief cycloheximide treatment prevented virus growth, ribonucleic acid (RNA) synthesis continued at an undiminished rate for at least 2 hr after removal of the drug. Although this RNA appeared identical by polyacrylamide gel electrophoresis to "early" viral messenger RNA, it was not found associated with ribosomes or polyribosomes. Failure to observe viral protein synthesis was consistent with the latter finding. It appeared unlikely that the translational block resulted from inadequate removal of cycloheximide, since the effects of the drug were shown to be reversible at earlier or later times in infection or even at the same time when a lower multiplicity of virus was used. Interference with the normal synthesis of specific viral protein factors required for translation was postulated to explain the results.

Acrylates↗

Cycloheximide and heat shock induce new polypeptide synthesis in Neurospora crassa.

Treatment of Neurospora crassa with 0.1 microgram of cycloheximide per ml, a concentration which inhibited protein synthesis by about 70%, resulted in the greatly enhanced synthesis of at least three polypeptide bands with estimated molecular weights of 88,000, 30,000, and 28,000. A temperature shift from 25 to 37 degrees C resulted in the appearance of a single new polypeptide band of 70,000 daltons, the same size as the major heat shock-induced proteins observed in species of Drosophila and Dictyostelium. Synthesis of the cycloheximide-stimulated polypeptide bands was on cytoplasmic ribosomes rather than on mitochondrial ribosomes, as incorporation of isotope into the polypeptide bands was inhibited by 1.0 microgram of cycloheximide per ml but not by 1 mg of chloramphenicol per ml. In a mutant with cycloheximide-resistant ribosomes, 0.1 microgram of cycloheximide per ml failed to alter the pattern of protein synthesis from that of the controls. It is suggested that the new synthesis of the polypeptide bands reflects specific mechanisms of adaptation to different kinds of environmental stress, including inhibition of protein synthesis and temperature increases.

Chloramphenicol↗