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PubMed1975

Regulation of ornithine decarboxylase in 3T3 cells by putrescine and spermidine: indirect evidence for translational control.

Addition of putrescine of spermidine prevents the increase in ornithine decarboxylase activity in cultures of 3T3 cells brought about by pituitary growth factors and results in a rapid, specific, and reversible reduction of enzyme activity in cultures previously stimulated by the growth factors. These effects are not due to polyamine toxicity and do not require other organic medium components. The amines apparently share a single carrier-mediated transport system in 3T3 cells. Methylglyoxal bis(guanylhydrazone), an inhibitor of spermidine synthesis from putrescine was found to also inhibit uptake of each amine. Studies with this drug indicate that each amine is effective without further metabolism. Since ornithine decarboxylase activity decays more rapidly in the presence of each polyamine after addition of camptothecin, the major locus of amine action appears to be in the cytoplasm. However, direct inhibition of the enzyme in vivo by assimilated amines appears to account for at most a small part of the reduction in activity, a conclusion supported by the inability to recover activity in vitro. Also, neither amine seems to act by accelerating enzyme inactivation. When amines are removed from the medium, the subsequent recovery of enzyme activity is totally prevented by trichodermin, an inhibitor of protein synthesis, but is only slightly reduced by camptothecin. It is suggested that both putrescine and spermidine reduce ornithine decarboxylase activity by selectively inhibiting translation.

Camptothecin↗

PubMed1976

Genetic studies on cycloheximide-resistant strains of Schizosaccharomyces pombe.

Cycloheximide-resistant mutants of Schizosaccharomyces pombe were isolated either as spontaneous mutants or after mutagenic treatment with nitrous acid, UV and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Twenty-three spontaneous mutants and 64 induced mutants were analysed genetically. Crosses revealed that at least four loci, designated cyh1, cyh2, cyh3 and cyh4 are responsible for resistance. Alleles of cyh1 show good growth on either high (100 mug/ml) or low (40 mug/ml) concentrations of cycloheximide whereas alleles at the cyh2, cyh3 and cyh4 loci gorw well on 40 mug/ml but poorly on 100 mug/ml. Some alleles at the cyh2 and cyh3 loci are also temperature sensitive (ts), the ts phenotype being conferred by the same gene as the resistance. In diploids, cyh1 and cyh4 are re-essive to wild type whereas cyh2 and cyh3 are semi-dominant. There was no intragenic complementation between three cyh1 alleles. Cross-resistance to trichodermin and anisomycin was shown by cyh2, cyh3 and cyh4 but not cyh1. Most cyh1 alleles, of spontaneous and UV origin only, were cold sensitive (cs) at 14 degrees and some of these were also cycloheximide dependent at the same temperature. It is suggested that the cyh1 and cyh4 genes are involved in ribosome formation or function and the other loci probably affect the uptake of cycloheximide by the cells.

Anisomycin↗

PubMed1990

Translation of the Saccharomyces cerevisiae tcm1 gene in the absence of a 5'-untranslated leader.

The role of eukaryotic 5'-untranslated messenger RNA leaders is not entirely clear, since they share little sequence similarity among each other. The importance of the leader in determining the efficiency of translation initiation was addressed here by examining the polyribosome distribution of several leader-deletion alleles of the yeast tcm1 gene (coding for ribosomal protein L3). Shortening of this 22-nucleotide leader, or complete removal of it (the first nucleotide of the mRNA becoming the A of the translation initiation codon AUG) permitted translation, albeit reduced. Further deletion of as few as the first two nucleotides of the initiation codon leads to a substantial reduction in ribosome loading, which is compatible with inefficient initiation at the next downstream, out-of-frame, AUG triplet. A second measure of translation initiation was obtained by assaying qualitatively for the production of biologically active L3 protein using growth-resistance to trichodermin. This experiment indicates that ribosomes can recognize the correct initiation codon even in the complete absence of a leader. We conclude that the 5'-untranslated leader of the yeast tcm1 gene is not essential for accurate translation initiation, but enhances its efficiency.

Base Sequence↗

PubMed1985

Inducible phenotypic multidrug resistance in the fungus Mucor racemosus.

The dimorphic fungus Mucor racemosus exhibited a single-step, inducible resistance to cycloheximide, trichodermin, and amphotericin B. Cells adapted to inhibitory levels of the antibiotics after 12 to 40 h. The adaptation involved all the cells in the population and was not the result of the selection of resistant mutants. Adaptation to one drug provided cross resistance to other, dissimilar drugs. Resistance was lost within several generations of growth in the absence of the inhibitors.

Amphotericin B↗

PubMed1990

Coaggregation of Streptococcus sanguis and other streptococci with Candida albicans.

Thirteen strains of viridans group streptococci and two strains of other streptococci were tested for coaggregation with Candida albicans. Streptococcus sanguis strains generally exhibited low levels of adherence to 28 degrees C-grown exponential-phase yeast cells, but starvation of yeast cells for glucose at 37 degrees C (or at 28 degrees C) increased their coaggregating activity with these streptococci by at least tenfold. This was a property common to four C. albicans strains tested, two of which were able to form mycelia (6406 and MEN) and two of which were not (MM2002 and CA2). The expression of the coaggregation adhesin during yeast cell starvation was inhibited by addition of trichodermin or amphotericin B. The strains of S. sanguis, Streptococcus gordonii, and Streptococcus oralis tested for coaggregating activity encompassed a diverse range of physiological and morphological types, yet all exhibited saturable coaggregation with starved C. albicans cells. There was no correlation of cell surface hydrophobicity, of either yeast or streptococcal cells, with their abilities to coaggregate. Strains of Streptococcus anginosus also coaggregated with starved yeast cells; Streptococcus salivarius and Streptococcus pyogenes coaggregated to a lesser degree with C. albicans, and the coaggregation with S. pyogenes was not promoted by yeast cell starvation; Streptococcus mutans and Enterococcus faecalis did not coaggregate with yeast. The coaggregation reactions of S. sanguis and S. gordonii with C. albicans were inhibited by EDTA and by heat or protease treatment of the yeast cells and were not reversible by the addition of lactose or other simple sugars. These observations extend the range of intergeneric coaggregations that are known to occur between oral microbes and suggest that coaggregations of C. albicans with viridans group streptococci may be important for colonization of oral surfaces by the yeast.

Amphotericin B↗

PubMed1980

Regulation of ornithine decarboxylase during morphogenesis of Mucor racemosus.

During the yeast-to-hyphae transition of the dimorphic phycomycete Mucor racemosus, there was a 30- to 50-fold increase in the activity of ornithine decarboxylase. Increased enzyme activity preceded the emergence of germ tubes and reached a maximum before conversion was completed. Subsequently, enzyme levels rapidly declined, despite the continuation of mycelial growth. Both putrescine and spermidine blocked the enzyme activity response. Protein synthesis was required for the increase in enzyme activity during morphogenesis. A combination of actinomycin D and netropsin inhibited ribonucleic acid synthesis but failed to inhibit the increase in ornithine decarboxylase activity. There was a twofold increase in the enzyme half-life during morphogenesis with either trichodermin or verrucarin to inhibit protein synthesis.

Carboxy-Lyases↗

PubMed1975

Inhibitors of polypeptide elongation on yeast polysomes.

Yeast polysomes are very active for amino acid incorporation when supplemented with elongation factors and the different components required for elongation of the polypeptide chain. This polysomal system is suitable for the study of the individual streps of the elongation cycle and to test the effect of different inhibitors. Anisomycin, trichodermin, trichodermol, trichothecin, fusarenon X, sparsomycin and blasticidin S inhibit peptide bond formation on these polysomes, whereas diphtheria toxin, pederine, cycloheximide and cryptopleurine block translocation.

Amino Acids↗

PubMedDate not supplied

[Biological preparations with different mechanism of action for protecting potato against fungal diseases].

Mycological analysis throughout the vegetation period of potato (Solanum tuberosum) made it possible to study in detail the structure of micromycete community, to determine typical dominant (frequency, more than 60%), typical common (frequency, 30 to 60%), typical rare (frequency, 10 to 30%), and casual (frequency, less than 10%) species and to estimate changes in the microorganism community caused by plant protection preparations with different mechanisms of action. It was shown that, as a result of occurrence of resistant forms, synthetic preparations against fungal pathogens of potato (such as TMTD, Ridomil gold MC, and Cupricol) were only slightly more effective than biological preparations (Trichodermin and AgroChit), with the former considerably changing the natural saprophytic mycological community. An increase in the soil pool of Trichoderma harzianum as a result of application of a biological preparation based on this antagonistic fungus correlated with its effectiveness against the soil pathogen Fusarium sp., which causes root rots. A chitosan-based elicitor preparation more effectively suppressed the development of early (Alternaria sp. and Macrosporium sp.) and late (Phytophthora sp.) blights of leaves and had a weaker effect on the soil microflora.

Alanine↗

PubMed1993

[Hygienic standardization of some biological pollutants in the water].

Paper is devoted to problem of sanitary protection of water reservoirs from pollution by bioinsecticides and biosynthesis biologic waste. Experimental data on influence of biological pollutants on organoleptic water properties, water sanitary and toxicologic status are presented. Standards for open water bodies are recommended: dendrobacillin--6 x 10(4) org/l, trichodermin--2 x 10(4) org/l, grain moth pollen--0.05 mg/l, fodder yeast--0.08 mg/l, turingin--0.048 mg/l.

Agrochemicals↗

PubMedDate not supplied

[Influence of Bacillus intermedius RNAse on growth-stimulating and antagonistic characteristics of Trichoderma harzianum].

Bacillus intermedius RNAase (with specific activity of 1,000,000 units per one mg of protein) at concentration of 1 x 10(-3) mg/ml was shown to increase antagonistic and growth-stimulating properties of Trichoderma harzianum. An application of trichodermin which was treated with an enzyme enhanced cucumber crop capacity by 15-18% in industrial conditions.

Bacillus↗

PubMed1985

Mycotoxins producing fungi and mycoflora of air-dust from Taif, Saudi Arabia.

Using the dilution plate method, 70 species and 31 genera were collected from 20 dust samples on glucose (28 genera and 64 species) and cellulose Czapek's agar (22 genera and 46 species) at 28 degrees C. The most common fungi were Aspergillus niger, A. flavus, A. flavus var. columnaris, Phoma glomerata, Fusarium oxysporum, Penicillium chrysogenum and Mucor racemosus; and A. nidulans, Phoma humicola, Drechslera spicifera and Stachybotrys chartarum on the two media, respectively. Toxicity test showed that about 85% of the isolates tested were toxic to brine shrimp (Artemia salina). Thin layer chromatographic analysis revealed that 13 out of 23 toxic isolates produced known mycotoxins. Toxins identified were: aflatoxins B1 and B2, Kojic acid and trichodermine.

Aflatoxin B1↗

PubMed1975

The mode of action of griseoviridin at the ribosome level.

The antibiotic griseoviridin binds to the larger subunit of Escherichia coli ribosomes blocking the interaction between the 3' terminal end of peptidyl-tRNA and the donor site of the peptidyl transferase centre. Griseoviridin inhibits binding of chloramphenicol, thiamphenicol, lincomycin, erythromycin and streptogramin A to bacterial ribosomes. Moreover griseoviridin protects the ribosomal binding site of gougerotin from the drastic conformational changes taking place in the presence of ethanol. Griseoviridin is also able to interact with eukaryotic ribosomes as shown by its effects on model systems and on anisomycin, trichodermin and gougerotin binding studies. Nevertheless, griseoviridin affinity for the 80-S type ribosomes (yeast or human) is two orders of magnitude smaller than with E. coli ribosomes. The inhibitory spectrum and mode of action of griseoviridin on ribosomes is compared to that of antibiotics of the streptogramin A group and found to be essentially the same.

Anti-Bacterial Agents↗

PubMed1976

Activities of nucleoprotein particles derived from rat liver ribosome.

80-S ribosomes and 60-S subunits from rat liver were treated at increasing KC1 concentrations giving protein-deficient ribosomal particles whose components were analyzed and their activity tested. Most of the activities assayed stand treatment up to KC1 concentrations of around 0.6 M; peptidyl transferase, measured by the fragment reaction, however was 50% inhibited by 0.5 M KC1 in 60-S subunits but not in 80-S ribosomes. Three proteins, L21, L26 and L31, might be implicated in this loss of activity. 60-S subunits forming part of the 80 S ribosome are more resistant to the salt treatment and the pattern of proteins released by the treatment differs from the one obtained from free 60-S subunits, implying perhaps a change of conformation of this subunit upon association to form 80-S couples. According to their resistance to release by KC1 the proteins of the large sub-unit can be divided into three groups: (1) easily removed, including proteins: L1, L11, L17 and L25 in 80-s subunits and in addition, L5, L8, L9, L13, L20, L22, L26, L29, L31 and L32/33 in 60-S subunits; (2) proteins resistant to release by high salt concentrations in 80-S ribosomes as well as in 60-S subunits, namely proteins L3, L14, L27, L36, L40, L41, X1 and X2; (3) the rest of the proteins which are released in a more or less continuous way throughout the treatment. 5 S RNA is not released by KC1 treatment at the concentrations used. The binding sites for the antibiotics trichodermin and anisomycin are affected in a different way by the salt treatment, indicating that they are structurally different.

Animals↗

PubMed1978

Binding of [3H]narciclasine to eukaryotic ribosomes. A study on a structure-activity relationship.

[3H]Narciclasine is a specific inhibitor of peptide bond formation on eukaryotic ribosomes and binds to 60-S ribosomal subunits. Binding of [3H]-narciclasine to yeast ribosomes is inhibited by many other inhibitors of peptide bond formation including anisomycin, several sequiterpene antibiotics (trichodermin, trichothecin, fusarenon X and verrucarin A) several Cephalotaxus alkaloids (harringtonine, homoharringtonine and isoharringtonine), several Amaryllidaceae alkaloids (pretazettine, haemanthamine, lycorine, pseudolycorine and dihydrolycorine) and the narciclasine derivatives trans-dihydronarciclasine, trans-dihydronarciclasine acetonide and isonarciclasine. Binding is also inhibited, although to a very small extent, by methylnarciclasine and cisdihydronarciclasine. In contrast, no inhibition of [3H]narciclasine binding was observed in the presence of certain other inhibitors of peptide bond formation including blasticidin S, gougerotin, sparsomycin and puromycin.

Alkaloids↗

PubMed1977

Mutation in continuous cultures of Schizosaccharomyces pombe. I. Dependence of the kinetics of mutation accumulation upon the growth-limiting nutrilite.

The rate of spontaneous mutation to resistance to the 12,13-epoxytrichothecene trichodermin has been determined under different growth limiting conditions in continuous cultures of the microbial eukaryote Schizosaccharomyces pombe. In agreement with data obtained in bacterial systems by previous workers the kinetics observed for the accumulation of mutations is found to be dependent upon the nutrient used to limit the growth of the population. Under conditions of glucose-limitation mutation accumulation is directly proportional to the rate of cell division, while under histidine-limitation it is proportional to chronological time. Various possible explanations for these observations are discussed.

Ascomycota↗

PubMed1978

Mutation in continuous cultures of Schizosaccharomyces pombe II. Effect of amino acid starvation on mutational response and DNA concentration.

In agreement with the results obtained in Escherichia coli by other workers and our own previous data, the kinetics with which spontaneous mutations to resistance to the 12,13-epoxytrichothecene trichodermin accumulate in a lysine auxotroph of Schizosaccharomyces pombe are dependent upon the nutrilite used to limit the growth of the population. Under conditions of glucose-limitation mutation accumulation is proportional to generation time, while under lysine-limitation it becomes proportional to chronological time. In contrast to observations made in bacterial system, however, no significant change in the DNA content per cell is noted in slow growing cultures grown under amino acid starvation. These findings help to eliminate some of the theories put forward to explain the differential mutational responses observed under different growth limiting regimes.

Ascomycota↗

PubMed1985

Modification of membrane permeability during Semliki Forest virus infection.

Modification of membrane permeability has been analyzed in Semliki Forest virus (SFV)-infected cells by means of translation inhibitors not permeable to normal cells. A higher inhibition of protein synthesis in the infected cells is only observed with those antibiotics that do not easily pass the cell membrane, but not with others, permeable to cells, such as anisomycin, cycloheximide, trichodermin, etc. It does not, therefore, seem that the suggestion of M. A. Gray, K. J. Micklem, and C. A. Pasternak [Eur. J. Biochem. 135, 299-302, (1983)] that protein synthesis in virus-infected cells is more susceptible to translation inhibitors in general is correct. Both low- and high-molecular weight compounds enter the cell very early during SFV infection. This permeabilization is blocked by compounds known to increase the pH of coated vesicles, such as NH4Cl and chloroquine. Inhibition of energy production by means of N3Na and 2'-deoxyglucose also blocks this process. The optimal external pH for this early permeabilization is around 7-8. Acidic pH inhibits the entry of these impermeant antibiotics promoted by SFV. Analysis of 86Rb+ content in SFV-infected HeLa cells also indicates that a drastic decline in this cation takes place, in agreement with previous findings, but disagreeing with the previous results. A parallel between the decrease in this cation and the blockade of protein synthesis is apparent, throughout the course of infection. In addition to the early permeabilization that takes place during virus entry, increased entry of hygromycin B and alpha-sarcin also occurs in SFV-infected cells from 2 to 3 hr postinfection, but not when late viral replication is blocked by means of interferon treatment.

Ammonium Chloride↗

PubMed1978

Mechanisms of corticotropin action in rat adrenal cells. I. The effects of inhibitors of protein synthesis and of microfilament formation on corticosterone synthesis.

The contributions of protein synthesis and formation of microtubules and microfilaments to corticotropin-stimulated steroidogenesis in rat adrenal cell suspensions has been assessed by use of a series of inhibitors to each function. Five inhibitors of protein synthesis (cycloheximide, puromycin, blastocidin S, anisomycin, and trichodermin) each exhibited time-dependent inhibition of corticotropin-stimulated steroidogenesis. For the first 30 min, steroidogenesis was more extensively inhibited than protein synthesis, after which the effectiveness of the inhibitors diminished on steroidogenesis but not on protein synthesis. The reversal effect was not observed at high levels of inhibitors. One inhibitor of microfilament formation (cytochalasin B) and four inhibitors of microtubule formation (colchicine, podophyllotoxin, vinblastine sulfate and griseofulvin) inhibited steroidogenesis without inhibiting protein synthesis and without any reversal effect with prolonged incubation. The actions of all ten inhibitors were shown to be fully reversible. Cell superfusion of adrenal cells showed that the decay of steroidogenesis upon addition of all the protein synthesis inhibitors was similar to decay upon removal of corticotropin from the medium (t1/2 = 4--6 min). Recoveries from inhibition upon removal of the inhibitors were similar to each other and comparable to initial corticotropin stimulation of the cells (lag of 3--5 min, t1/2=7--9 min). Similar kinetics of inhibition and recovery were observed for vinblastine sulfate while a direct inhibition of cytochrome P-450scc by aminoglutethimide was complete within 1 min and was rapidly reversed. Injection of each inhibitor (all classes) into hypophysectomized rats inhibited the elevation of plasma corticosterone by corticotropin. The extent of cholesterol combination with cytochrome P-450scc in adrenal mitochondria isolated from these rats was also decreased by all of the inhibitors. Decreases in plasma corticosterone correlated directly with decreases in cholesterol combination with cytochrome P-450scc (r=0.94). It is concluded that protein synthesis and steroidogenesis must be intimately coupled probably due to the requirement of a labile protein for cholesterol transport to cytochrome P-450scc. An involvement of microtubules and microfilaments in this process is clearly indicated.

Adrenal Cortex↗