[Inhibition of oleandomycin synthesis by glucoses added during fermentation]. / Podavlenie biosinteza oleandomitsina gliukozoi pri ee dobavlenii v protsesse fermentatsii.

Oleandomycin biosynthesis by Streptomyces antibioticus is repressed by glucose added to the growth medium in the process of fermentation. Phosphotransferase involved in the synthesis of acetyl CoA and propionyl CoA (the precursors of the antibiotic macrolactone ring) is neither inhibited nor repressed, and the substrate specificity of the enzyme does not change. The content of cAMP in the mycelium of S. antibioticus does not change significantly when either glucose or sucrose is added to the medium 24 h after the inoculation whereas the content of exogenous cAMP rises abruptly 24 h after glucose addition. At the same time, the medium becomes much more acidic and the content of protein in the mycelium rises noticeably. Consequently, cAMP may be involved in the regulation of the culture growth.

[Cyclic adenosine-3',5-monophosphate in Streptomyces antibioticus and its possible role in regulating oleandomycin biosynthesis and the growth of the culture]. / Tsiklicheskaia adenozin-3',5-monofosfornaia kislota u Strptomyces antibioticus i ee vozmozhnaia rol' v reguliatsii biosinteza oleandomitsina i rosta kul'tury.

When glucose is substituted for sucrose in the fermentation medium for Streptomyces antibioticus, the pH of the cultural broth becomes more acidic, the rate of protein synthesis in the mycelium rises, and the rate of oleandomycin synthesis decreases abruptly. The dynamics of cAMP (cyclic monophosphate) accumulation was studied in the process of biosynthesis by the culture in different media. Most of the synthesized cAMP (80-90%) was shown to be excreted into the medium. Glucose stimulates cAMP synthesis and excretion from the mycelium by a factor of 1.5-3. No distinct correlation was found between cAMP content in S. antibioticus cells and the level of oleandomycin biosynthesis. A correlation between changes in the concentration of exocellular cAMP and protein synthesis in the mycelium suggests that the excreted cAMP may be involved in regulating the growth of the culture producing the antibiotic.

[Inhibition of oleandomycin biosynthesis by glucose]. / Podavlenie biosinteza oleandomitsina gliukozoi.

The results of the study on the effect of glucose and various carbohydrates on biosynthesis of oleandomycin by Streptomyces antibioticus are presented. It was found that glucose added at the beginning or by the 48th hour of the fermentation process on the complex medium inhibited oleandomycin biosynthesis. To investigate the mechanism of the glucose effect, a fermentation medium was developed. It provided variation of the carbohydrate composition, determination of the protein content in the culture and evaluation of the mycelium productivity. With the use of this medium it was shown that monosaccharides such as galactose, fructose and glucose significantly activated the mycelium growth as compared to lactose and sucrose. At the same time glucose completely inhibited oleandomycin biosynthesis when added either as an only carbohydrate component or in combination with galactose or fructose, while the presence of the other two monosaccharides did not prevent antibiotic production, though the mycelium productivity was lowered as compared to that with the use of the disaccharide. Therefore, the inhibitory effect of glucose on biosynthesis of oleandomycin was not connected with activation of the culture growth by it. Acidification of the medium on cultivation of the streptomycete in the presence of glucose only partially explained its inhibitory effect, since inhibition was maintained on the medium with addition of CaCO3 which stabilizes pH. Addition of 2-deoxy-D-glucose, a nonmetabolized glucose analog, to the fermentation medium retarded antibiotic production. It is possible that the inhibitory effect of glucose on biosynthesis of oleandomycin is not associated with its metabolism.

[Effect of levorin on the intracellular pool of free amino acids in Ehrlich ascites carcinoma cells]. / Vliianie levorina na vnutrikletochnyi fond svobodnykh aminokislot v kletkakh astsitnoi kartsinomy Erlikha.

Levorene, a polyenic antibiotic, lowered the concentration of amino acids in the cells of Ehrlich carcinoma. The decrease in the intracellular level of the amino acids was due not only to inhibition of their entrance to the cells but also to their increased leaching from the cells. The effect of levorene on the intracellular level of the neutral amino acids was higher than that on the main amino acids which was associated with different sensitivity of the amino acid transport systems to the antibiotic.

[Heterogeniety of the amino acid pool for protein synthesis in Ehrlich ascites carcinoma cells]. / Geterogennost' fonda aminokislot dlia sinteza belka v kletkakh astsitnoi kartsinomy Erlikha.

Using a new methodological approach based on a step-wise labelling with [14C] and [3H] amino acids, it was demonstrated that the Ehrlich ascite carcinoma cells are capable of utilizing both intracellular and extracellular amino acid pools for protein synthesis. The inhibition of amino acid transport into the cells is accompanied by a more intensive utilization of the exogenous pool. The described procedure permits to calculate the specific radioactivity of the tRNA-bound amino acid and the absolute rate of protein synthesis.

[Effect of levorin on RNA synthesis in Ehrlich ascites carcinoma cells]. / Vliianie levorina na sintez RNK v kletkakh astsitnogo raka Erlikha.

The polyene antibiotic levorin had no effect on the incorporation of 14C-uracil into the pool of intracellular free nucleotides in Ehrlich ascites tumour cells. RNA synthesis was inhibited by the antibiotic only at the late stages of incubation, evidently, due to earlier disturbances of the protein synthesis and in cell energetics.

[Action of levorin on the incorporation of labelled amino acids into the proteins of Ehrlich ascitic cancer cells]. / Deistvie levorina na vkliuchenie mechenykh aminokislot v belki kletok astsitnogo raka Erlikha.

A polyenic antibiotic levorin had a significant damaging effect on the amino acid transport in the cells of Ehrlich's ascites carcinoma by inhibiting the incorporation and increasing the release of 14C-glycine and 14C-arginine. Inhibiton of incorporation of the radioactive amino acids into protein was observed on both simultaneous addition of the antibiotic and the label into the medium and addition of previously labeled cells into radioinactive medium with the antibiotic. Since in the latter case levorin had probably no effect on the specific radioactivity of the precursor, it was suggested that the decrease in the label incorporation into protein was an evidence of the real antibiotic inhibition of the rate of the synthesis of the polypeptide chain.

[Effect of levorin on the activity of facilitated diffusion systems in murine Ehrlich cancer cells]. / Deistvie levorina na aktivnost' nekotorykh sistem oblegchennoi diffuzii v kletkakh myshinogo raka Erlikha.

Five-minute incubation of the cells of Ehrlich's mouse carcinoma with levorin in a concentration of 0.25 microgram/ml resulted in a release of 30% of K+ and 40-50% suppression of active transport of neutral amino acids. No changes in incorporation of nitrous compounds, nucleosides and cyclophosphamide, an antitumor drug transported by the systems of facilitated diffusion were observed under the same conditions.

[Action of levorin on amino acid transport in the rat small intestine]. / Deistvie levorina na transport aminokislot v tonkoi kishke krysy.

Levorin, a polyenic antibiotic, in concentration of 2.10(-6) M markedly inhibited the active transport of amino acids in the cells of rat thin intestine, thus decreasing the oxygen dependent transfer of 14C-glycine and 14C-leucine and antigradient accumulation of glycine in the enterocytes. The effect increases with an increase in the period of the intestine mucosa contact with the antibiotic. Introduction of levorin from th serous side had no effect on the glycine transport. Inhibition of the transmembrane transport of glycine by levorin is due to its effect on transfer and accumulation of amino acids in the cells.

[Action of levorin on glucose transport in the rat small intestine]. / Deistvie levorina na transport gliukozy v tonkoi kishke krysy.

The technique of accumulating preparation of the mucosa and "turned out sac" was used to show that levorin, a polyenic antibiotic in a concentration of 10(-6) M, lowered the transport rate and accumulation of glucose by the epithelial cells of the rat thin intestine under conditions of oxygenation. Suppression of the glucose transport in the first stages resulted in partial inhibition of the transmembrane transfer. It is suggested that levorin suppression of the glucose transport through the erythrocyte apical membrane in the thin intestine is associated with a decrease in the electrochemical gradient of Na+.

[Effect of ionic composition of incubation medium on inhibition by levorin of amino acid transfer in Candida albicans]. / Vliianie ionnogo sostava sredy na tormozhenie levorinom transports aminokislot u Candida albicans.

It was demonstrated that K+ and Na+ concentrations in C. albicans cells cultivated on an aerated enriched complex medium do not practically depend on their concentration ratios in the medium. The effect of levorin on the ionic composition of the cells, on the contrary, strongly depends on the composition of the medium. In a Na-containing medium with levorin the bulk of intracellular potassium is substituted by sodium, while in a "potassium" medium no redistribution of the monovalent cations in the cells occurs. The transport of neutral amino acids with a short carbohydrate radical (e. g. glycine, alanine) is largely inhibited by levorin irrespective of the intra- and extracellular concentrations of the movement cations. The inhibition of transport of amino acids with a long carbohydrate radical (e. g. leucine, phenylalanine) by levorin is possibly mediated by its effect on the intracellular concentration of monovalent cations, since in "potassium" medium it is either insignificant or altogether absent. The transfer of neutral amino acids differing in the length of the carbohydrate radical of C. albicans by various systems is discussed.

[Effect of levorin on incorporation of individual amino acids into proteins of membranes, ribosomes and cell sap of Candida albicans]. / Deistvie levorina na vkliuchenie individual'nykh aminokislot v belki membran, ribosom i kletochnogo soka Candida albicans.

The effect of levorin on incorporation of labelled amino acids into the protoplasts and proteins of C. albicans depended on the ionic composition of the medium and on the amino acid tested. In a potassium-enriched medium the predominant effect of levorin on [14C] alanine transport into the protoplasts was decreased, while in case of [14C] leucine transport it was completely eliminated. The incorporation of [14C] alanine into the proteins of ribosomes and cell juice was inhibited by the antibiotic in a greater degree as compared to the membrane proteins, the difference in the rate being more pronounced in a sodium-enriched medium. The incorporation of [14C] leucine was inhibited in all protein fractions in the same degree, which was observed only in a sodium-enriched medium.

[Doses levorin display an antiandrogenic action?]. / Okazyvaet li levorin antiandrogennoe deistvie?

The antiandrogenic effect of levorin on immature castrated rats treated with exogenic testosterone was studied. In a dose of 200 mg/kg levorin lowered the cholesterin blood levels in the rats, inhibited the testosterone-induced increase in RNA concentration in the ventral and dorsal prostate and the seminal vesicles and to a less extent suppressed the growth of the accessory sexual glands. However, the antiandrogenic effect was observed with the use of levorin in the dose producing a pronounced toxic action evident from death of a part of the animals and a marked decrease in the animal body weight. This fact casts doubt on specificity of the levorin effect. Apparently, in high doses levorin impairs metabolism as a whole which cannot but affect the response of the sexual glands to administration of testosterone.

[Action of levorin on amino acid transport in Candida albicans]. / Deistvie levorina na transport aminokislot u Candida albicans.

It was shown that suppression by levorin of the leucine transport into the cells of C. albicans was due to replacement of intracellular K+ by Na+ induced by the antibiotic. The alanine transport was suppressed by levorin irrespective of the ratio of the monovalent cations concentration in the medium and inside the cell. The levorin effect on the protone escape from the cells was negligible and probably played no significant role in the mechanism of the amino acid transport suppression by the antibiotic.

[Effect of amigluracil and levorin on membrane permeability and protein synthesis in Candida albicans protoplasts]. / Vliianie amigluratsila i levorina na membrannuiu pronitsaemost' i sintez belka v protoplastakh Candida albicans.

It was shown that amigluracyl, a water soluble derivative of methacyl which decreased the nephrotoxic effect of polyens activated the membrane permeability in Candida albicans for a mixture of 14C-amino acids but had no significant effect on protein synthesis in this microorganism. The level of inhibition of the membrane permeability in C. albicans for the amino acids and protein synthesis in the fungus by levorin did not practically depend on the presence of amigluracyl in the incubation medium. The minimum levorin concentration inhibiting the growth of Candida albicans in the presence or absence of levorin was 0.039 gamma/ml. Therefore, amigluracyl may be used in combination with polyenic antibiotics for the treatment of mycoses.

[Dependence of inhibition by levorin of amino acid incorporation into protoplasts and subcellular proteins of Candida albicans on the change of endocellular potassium concentration]. / Zavisimost' tormozheniia levorinom vkliucheniia aminokislot protoplasty i belki subkletochnykh fraktsii Candida albicans ot izmeneniia vnutrikletochnoi kontsentratsii kaliia.

Levorin is found to decrease more efficiently potassium concentration in C. albicans protoplasts under their incubation in the presence of sodium than in the medium containing the equivalent amount of potassium. Minimal inhibitory concentration of levorin for resistant C. albicans cells incubated on potassium-depeleted medium was in 4 times lower than for cells incubated in potassium-enriched medium. The decrease of membrane permeability for 14C-amino acids and their incorporation into membrane, ribosomal and soluble proteins under the effect of levorin was more pronounced when protoplasts were cultivated in sodium-containing medium than in potassium-containing one. In both media the inhibition of 14C-amino acid incorporation by levorin into ribosomal and cytosol proteins was more efficient than into membrane proteins, but these differences were less pronounced in case of potassium-containing medium.

[Effect of polyene antibiotics on protein synthesis by free and membrane-bound ribosomes of Candida albicans]. / Deistvie polienovykh antibiotikov na sintez belka svobodnymi i membranosviazannymi ribosomami Candida albicans

Polyene antibiotics (levorin, nistatin, amphotericin B) inhibit protein synthesis at concentrations decreasing 14C-amino acid incorporation into Candida albicans protoplasts by 30--60%, the depression of membrane permeability beginning earlier than protein synthesis inhibition. Fractionation of protoplast lysates revealed that protein synthesis by free ribosomes was inhibited by antibiotics stronger than in case of membrane-bound ribosomes. It is supposed that different response of two ribosome classes for polyenes-induced damages is due to different sensitivity of free and membrane-bound ribosomes to the decrease of intracellular K+ concentration.