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Results for “Cycloheximide”

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PubMed1979

[Reduced catalytic effectiveness of RNA polymerase I in hepatocytes of rats treated with cycloheximide].

Rat liver RNA polymerase I solubilized from isolated nuclei and present in a soluble form in the cytoplasmic fraction has been analyzed by phosphocellulose chromatography 3 hours after the administration of cycloheximide. The antibiotic did not induce any change in the chromatographic properties of both nuclear and cytoplasmic RNA polymerase I. They appeared to remain in the IB and IA forms, characteristic of the transcribing (IB) and non-transscribing (IA) enzyme. While the level of the nuclear enzyme was not modified, the level of the cytoplasmic one appeared significantly increased. These results support previous ones indicating that the cycloheximide-induced inhibition of ribosomal RNA synthesis cannot be merely explained by a decrease in the nuclear or cellular level of RNA polymerase I. The cellular level of RNA polymerase I, taking into account the relative proportion of the enzyme found in nuclei and cytoplasm, appeared to be slightly increased. Cycloheximide administration did not seem to result in the appearance, in intact nuclei, of enzyme molecules in a free form or as blocked transcription complexes. It is concluded that the antibiotic affects the catalytic efficiency rather than the number of RNA polymerase I molecules actually engaged in the transcription of ribosomal cistrone.

Animals↗
PubMed1983

[Effect of cycloheximide on lysosomal proteinase activity in rat organs].

Administration of cycloheximide (0.1-0.4 mg/kg bw) to rats caused a progressive drop of cathepsin A, B, C and D activity in the liver and kidneys. In the spleen, the activity of all lysosomal proteinases declined 50-70% even with the minimal dose of cycloheximide. On the contrary, the activity of other lysosomal hydroxylases (beta-galactosidase and arylsulfatases A and B) dropped by not more than 10-25% in all the organs under study, regardless of the fact that the dose of cycloheximide was maximal. It is suggested that the reduction of cathepsin activities during protein biosynthesis inhibition is a regulatory mechanism by which the protein resources in the cell are preserved.

Animals↗
PubMed1984

[Structural changes in chromatin during activation of transcription coupled with translation inhibition by cycloheximide].

A chromatin preparation isolated one hour after cycloheximide injection possesses a higher RNA-synthesizing activity and is split by DNAase I to a greater extent as compared to chromatin of control hepatocytes. Thermal denaturation of this preparation causes a considerable increase (about 2-fold) in the content of the thermolabile fraction melting in the free DNA denaturation zone. The relative content of fast repetitions in the thermolabile fraction (1 hour after the beginning of experiment) is lower than that in control. The type of changes in the viscosity of chromatin in the predenaturation zone isolated one hour later suggests a more labile binding of DNA to the protein. Chromatin preparation isolated 3 hours after cycloheximide injection is characterized by intermediate values of all parameters under study, as compared to the two other preparations used in this experiment. It is assumed that the activation of transcription coupled with the inhibition of translation by cycloheximide is determined by the appearance of elongated segments of free or weakly bound DNA in the chromatin preparation.

Animals↗
PubMed1983

[Cycloheximide-dependent mutants of the yeast Saccharomyces cerevisiae].

Selection of sup1 and sup2 mutants in the yeast Saccharomyces cerevisiae on cycloheximide containing media revealed classes of mutants that either are completely unable to grow on YAPD without cycloheximide or need this drug under high temperature incubation (30 or 36 degrees C). Some of these mutants also exhibit the growth dependence on another antibiotic--trichodermin, and, at the same time, the osmotic dependence. A hypothesis claiming that sup1 and sup2 mutations cause conformational lability fo yeast cytoplasmic ribosomes has been put forward. It is also proposed that binding of cycloheximide and trichodermin to the mutant ribosomes cause their conformational shift, which compensates the functional defects.

Culture Media↗
PubMed1984

The effect of cycloheximide on repair in a temperature conditional radiation-sensitive mutant of Saccharomyces cerevisiae.

Previous results [M. Budd and R. K. Mortimer, Mutat. Res. 103, 19-24 (1982)] have shown that rad54-3 strains are temperature conditional for double-strand break repair. At the temperature where survival is high, 23 degrees C, rad54-3 strains are able to repair X-ray-induced double-strand breaks, while at the temperature where survival is low, 36 degrees C, these strains are unable to repair rad54-3 strains provide a system to study the effects of drugs that block protein synthesis such as cycloheximide on repair of X-ray damage. Repair of X-ray damage is studied by irradiating rad54-3 cells, incubating them at the permissive temperature, 23 degrees C, for 5 hr, shifting the cells to the restrictive temperature, 36 degrees C, and assaying for colony-forming ability. Comparing the survival of these cells with those which had been continuously incubated at the restrictive temperature after irradiation shows the extent of repair. Addition of cycloheximide at the time of irradiation causes an inhibition of repair. If cycloheximide is added a short time after irradiation, an enhanced recovery is observed compared with the addition of the drug at the time of irradiation. One explanation for the enhanced recovery is an increased synthesis of repair enzymes after irradiation.

Cell Survival↗
PubMed1978

[Stabilization of polyribosomal mRNA in rat liver cells under protein synthesis inhibition by cycloheximide].

It was found that in the course of centrifugation of the postmitochondrial fraction from rat liver in the sucrose concentration gradient, mRNA located in the EDTA-resistant structures sedimented together with polyribosomes. The same structures were detected in the polyribosomal fraction of liver cells after injection of ethionine to the animals. Centrifugation of polyribosomes through a layer of 2.0 M sucrose at 105 000 g for 4 hrs and subsequent centrifugation through a layer of 1.0 M sucrose resulted in the disappearance of the complexes from the polyribosomal fraction. Evidence for the absence of destruction of labelled polyribosomal mRNA in liver cells following the injection of cycloheximide were obtained. Actinomycin D also stabilized polyribosomal mRNA in liver cells, however, in a much lesser degree as compared to cycloheximide. Possible mechanisms of the stabilizing effects of cycloheximide and actinomycin D on polyribosomal mRNA in liver cells are discussed.

Animals↗
PubMed1983

Effects of puromycin and cycloheximide on properties of cells from Xenopus laevis early embryos.

The effects have been studied of puromycin and cycloheximide on the reaggregation of ectoderm cells dissociated from Xenopus laevis blastulae. Puromycin or cycloheximide can inhibit reaggregation, suggesting that cell reassociation is dependent upon protein synthesis. If the cells are allowed a 3 h 'recovery' period in culture medium following dissociation, before being exposed to either puromycin or cycloheximide, higher concentrations of the inhibitors are required to prevent cell aggregation, suggesting that significant synthesis of the proteins required for reaggregation occurs in the 3 h immediately following dissociation. Lower concentrations of puromycin permit cell reaggregation but reduce the normal formation of cilia. The effects have also been observed of puromycin on the scanning electron microscopical appearance of Xenopus blastula ectoderm cells cultured singly in vitro. Puromycin reduces the normal formation of pseudopodia, suggesting that puromycin might inhibit reaggregation partly by inhibiting cell movement. Puromycin also produces some elongated cells, possibly by inhibition of cytokinesis.

Animals↗
PubMedDate not supplied

[Effect of actinomycin D, cycloheximide and hypertonic concentrations of NaCl on the reproduction of the tick-borne encephalitis virus].

Synthesis of virus-specific polypeptides occurs in pig embryo kidney cells infected with tick-borne encephalitis virus and treated with actinomycin D, cycloheximide, and hypertonic concentrations of NaCl in various combinations. Despite the fact that virus-specific matrix RNAs function under such conditions, production of infectious virus particles is inhibited considerably. Virus yield is greatly decreased by treatment with actinomycin D alone and by combined effect of actinomycin D and cycloheximide. Sodium chloride and combined treatment of the infected cells with cycloheximide and NaCl do not affect the intact virus production. The mechanism of the inhibiting effect of actinomycin D on production of infectious tick-borne encephalitis virus is assumed to consist in the impairment of the synthesis of virus-specific ribonucleic acid and/or in marked reduction of its infectivity. Actinomycin D may possibly inhibit somehow the morphogenesis of intact virions of tick-borne encephalitis virus.

Animals↗
PubMedDate not supplied

[Effect of cycloheximide on synthesis of skeletal muscle proteins and nuclear DNA-dependent RNA-polymerase activity].

A high sensitivity towards cycloheximide is shown for three main protein fractions of albino rat skeletal muscle, i. e. a 50% inhibition of myofibrillar protein synthesis is caused by a dose of 0.1 mg/100 g of body weight after 3.5 h, the rate of inhibition of two other fractions is even higher. A dose of 3.0 mg/100 g of body weight inhibits the synthesis of the sarcoplasmic and myofibrillar proteins by 96% by the end of the 15th minute. Administration of cycloheximide in vivo (0.3 mg/100 g of body weight) inhibits the alpha-amanitin-resistant DNA-dependent RNA-polymerase activity of the nuclei. The relation between the inhibition rate and time of the cycloheximide action is ruled by the first order kinetic. This allows postulating the existence of a fast renewal with a period of half-life of about 110 min (determined graphically) among nuclear proteins involved in the transcription of rRNA. The idea of this protein participation in adaptive shifts of rRNA synthesis in the systematic skeletal muscle function is suggested.

Animals↗
PubMedDate not supplied

Effect of cycloheximide on increased aspartate aminotransferase in carbon tetrachloride hepatotoxicity.

The previously reported increases in liver and serum aspartate aminotransferase (ASAT) activities and liver protein content 24 hours after the administration of carbon tetrachloride (CCl4) were reduced by administering multiple doses of the protein synthesis inhibitor cycloheximide (CH). Liver ASAT and protein content were reduced to saline-injected control levels, and the serum ASAT increase was reduced by 45.0 percent in rats given CH. Although there are morphological features of severe hepatotoxicity in the cycloheximide-carbon tetrachloride-injected rats, cycloheximide does reduce the severity of these lesions and the regenerative response. These findings lend some support to the hypotheses that (1) the increase in liver ASAT activity and protein content after CCl4 is due to increased synthesis and (2) the increase in serum ASAT after CCl4 is most likely due to a combination of increased synthesis and leakage from necrotic and damaged cells.

Animals↗
PubMed1983

The effect of cycloheximide on dictyosome activity in Tradescantia pollen tubes determined using cytochalasin D.

Dictyosome activity in Tradescantia pollen tubes has been determined using a recently developed method based on the assumption that the rate of vesicle accumulation around the dictyosomes, after treatment with cytochalasin D, is equivalent to the actual rate of vesicle production. In tubes germinated in the presence of 1.0 micrograms/ml cycloheximide, reduced dictyosome activity could be detected as early as 10 min after sowing, although tube extension was not halted until later. After 30 min vesicle production had completely ceased. These observations are discussed in relation to previous reports on the effect of cycloheximide on pollen tube growth, and in relation to the synthesis and transfer of membrane proteins to secretory vesicles and the plasma membrane. It is concluded that the ability of pollen to germinate and produce short tubes in the presence of cycloheximide, does not necessarily indicate that protein synthesis is not a requirement for early pollen tube growth, as protein shortages would not be expected to become apparent over time periods less than the dictyosome turnover time and the secretory vesicle residence time.

Cycloheximide↗
PubMed1978

Partial inhibition of castration induced ventral prostate regression with actinomycin D and cycloheximide.

Sprague Dawley male rats were injected subcutaneously with either actinomycin D or cycloheximide in saline immediately after castration. Control animals received saline only. Treatment was repeated daily for 4 subsequent days, and 24 hr after the last injection rats were sacrificed by decapitation. Ventral prostates were dissected and weighed. Actinomycin D and cycloheximide administration significantly reduced the rate of prostatic weight loss in castrated rats; serum testosterone levels in the control and drug treated animals were comparable. Histologic studies of the prostates indicated that drug treated animals had more active epithelial cells than saline injected controls. These results indicate that the rate of prostatic regression induced by castration can be modified by drugs such as actinomycin D and cycloheximide.

Adrenal Cortex Hormones↗
PubMed1982

[Effect of cycloheximide on the alkaline and acid DNAse activity in rat cells].

Using spectrophotometric and viscosimetric techniques, the effects of cycloheximide on the activity of alkaline and acid DNAses in the homogenate cells of thymus, mesenterial lymphatic node, spleen, liver and in blood serum of the rat were studied. Using these two methods, it was demonstrated that cycloheximide inhibits the activity of alkaline DNAase in the spleen, lymphatic node and liver cells by 70% without changing that of acid DNAase in all the organs tested but has no inhibiting effect on the activity of alkaline endonuclease in the thymocytes. Cycloheximide inhibits the activity of alkaline DNAase in rat blood serum by 85%. It can thus be concluded that in the spleen, lymphatic node and liver cells there occurs a practically constant synthesis of alkaline DNAase, the bulk of which is released into the blood stream.

Animals↗
PubMed1980

The structure of chromatin synthesized in the presence of cycloheximide in Physarum polycephalum.

The effect of cycloheximide on protein and DNA synthesis and on the structure of chromatin was studied. Changes in the rate and extent of DNA synthesis in response to cycloheximide were highly variable in contrast to the extremely rapid and reproducible inhibition of protein synthesis. No differences in the rate of the release of acid-soluble products by nucleases and in the nature of the nucleoprotein particles were found in chromatin from plasmodia treated and non-treated with cycloheximide. It is concluded that, in Physarum polycephalum, unlike in higher animals, chromatin from the antibiotic-treated plasmodia is structurally indiscernible by the methods applied from normal chromatin.

Chromatin↗
PubMed1980

[Change in RNase activity in rat liver cells in cycloheximide protein synthesis inhibition].

Administration of cycloheximide to rats does not change the activity of acid and alkaline RNAases in the cytoplasm of hepatocytes. At the same time cycloheximide-induced inhibition of protein synthesis leads to a fall in the activity of RNAase of microsomes and membrane-bound polyribosomes. The activity of RNAase of free polyribosomes of hepatocytes rises considerably under the action of cycloheximide.

Animals↗
PubMed1980

The effect of cycloheximide and carbon tetrachloride in Ehrlich ascites tumour-bearing mice.

Treatment with cycloheximide and a hepatotoxic dose of CCl4 (well tolerated in normal animals) is acutely toxic in animals bearing the Ehrlich ascites tumour. Reduction in tumour load 4 hr after the administration of cycloheximide and CCl4 is life-saving: treatment with a hepatotoxic dose of CCl4 30 hr before challenge with cycloheximide and CCl4 also nullifies that otherwise life-threatening treatment.

Animals↗
PubMed1995

In vivo regulation of rat neutrophil apoptosis occurring spontaneously or induced with TNF-alpha or cycloheximide.

We previously demonstrated that human TNF-alpha induces rapid apoptosis of human neutrophils. To understand better the in vivo significance of neutrophil apoptosis, we examined spontaneous, recombinant human and mouse TNF-alpha- or cycloheximide-induced apoptosis of normal peripheral blood neutrophils (PBN), PBN from rats injected i.p. with proteose peptone or a streptococcus preparation, OK-432 (inflammatory PBN), peritoneally exudated neutrophils (PEN) obtained after a proteose peptone injection, and normal bone marrow neutrophils. The following observations were made. 1) Normal PBN responded to TNF-alpha, but PEN, normal bone marrow neutrophils, and inflammatory PBN at 12 h after stimulation did not. 2) The sensitivity to TNF-alpha of the inflammatory PBN started to decrease at 3 h, was lowest at 12 h, and was almost restored at 52 h after stimulation. 3) Spontaneous apoptosis of normal and inflammatory PBN reached 25% at 12 h after in vitro incubation, but that of PEN and normal bone marrow neutrophils was very low over this period. 4) The sensitivity to cycloheximide (6 h incubation) was high for normal PBN and bone marrow neutrophils, but low for PEN and inflammatory PBN after 12 h. 5) 125I-rhTNF-alpha binding of bone marrow neutrophils was significantly lower than that of normal and inflammatory PBN and PEN. 6) TNF-alpha-induced apoptosis of normal or inflammatory PBN and bone marrow neutrophils was enhanced by treatment with low doses of cycloheximide that alone were barely able to induce neutrophil apoptosis; however, apoptosis of PEN was not. The mechanisms and in vivo significance of these phenomena are discussed.

Animals↗
PubMed1994

[Change in the level of sphingosine in rat liver nuclei and cells during oncogene superexpression induced by cycloheximide].

Changes in the sphingosine content in rat liver cells and nuclei have been studied with reference to the level of nuclear oncogene expression, induced by cycloheximide (0.1, 0.5 and 3.0 mg/kg). It has been found that only the sublethal (3 mg/kg) dose of cycloheximide which induces the superexpression of c-fos and c-myc oncogenes can promote sphingosine accumulation in the cell. At the moment of enhanced expression of nuclear oncogenes, the maximum content of free sphingosine exceeds the control level 1.5- and 3-fold in the cell and in the nuclei, respectively. The difference in the sphingosine accumulation patterns in the cell and in the nuclei testifies to the fact that sphingomyelin metabolism is more active in the nuclei than in the cell. Sphingosine accumulation in the nuclei is characterized by coordination of sphingomyelinase activity and changes in the sphingomyelin content. A comparative analysis of activities of enzymes of sphingomyelin (sphingomyelinase) and phosphatidyl inositol (phosphatidyl inositol kinase) cycles indicates that in the nuclei the activation of the sphingomyelin cycle forestalls the cycloheximide-induced activation of the phosphatidyl inositol cycle and the maximal accumulation of nuclear oncogene mRNAs. A model of activation of oncogene expression with participation of sphingosine inhibiting protein kinase C and activating casein kinase II, the key enzymes of the signal transduction system of cell proliferation and differentiation, is proposed.

Animals↗