Specific modification of Q and R bands by 5-bromodeoxyuridine and actinomycin D]

When introduced into human lymphocyte culture, 5-bromodeoxyuridine (BUdR) and actinomycin D (AMD) induce chromosome differentiation by lack of condensation of segments corresponding to Q-bands (BUdR) and R-bands (BUdR and AMD). The total amount of DNA per cell is not modified by these treatments. The non-condensed segments partly keep their properties of R- or Q-banding after heat treatment or staining with quinacrine mustard. On the other hand, they lose their properties after ASG treatment (G-bands), and emit modified fluorescence after staining with acridine orange. With heat treatment or QM staining, it seems that BUdR or AMD elongate the R or Q segments in several ways—homogeneous repartition or fragmentation of various types. On the other hand, this elongation seems homogeneous after Feulgen staining. This suggests that the relation between Feulgen-revealed DNA and substratum of the R- and Q-bands might not be direct.     

The effect of space flight on the production of actinomycin D by Streptomyces plicatus

The effect of space flight on production of the antibiotic actinomycin D by Streptomyces plicatus WC56452 was examined onboard the US Space Shuttle mission STS-80. Paired space flight and ground control samples were similarly prepared using identical hardware, media, and inoculum. The cultures were grown in defined and complex media under dark, anaerobic, thermally controlled (20°C) conditions with samples fixed after 7 and 12 days in orbit, and viable residuals maintained through landing at 17 days, 15 h. Postflight analyses indicated that space flight had reduced the colony-forming unit (CFU) per milliliter count of S. plicatus and increased the specific productivity (pg CFU⁻¹) of actinomycin D. The antibiotic compound itself was not affected, but its production time course was altered in space. Viable flight samples also maintained their sporulation ability when plated on agar medium postflight, while the residual ground controls did not sporulate. Received 21 August 2001/ Accepted in revised form 30 July 2002     

The methylation of tRNA in KB cells after treatment with actinomycin D

Extensive shifts in the distribution of labeled methylated constituents of tRNA were observed in KB cells treated with actinomycin D for 30 min prior to a 90-min pulse with ³H-CH₃-methionine. Although this treatment completely blocked the synthesis of tRNA, methylation continued to the extent of 12–15% of controls (pulsed without antibiotic). Under this condition the relative proportion of radioactivity incorporated into 3-methylcytosine, N²-methylguanine and 2′-O-methylribose was markedly increased (170–235% of control values), it was moderately reduced in 1-methyladenine, 5-methyl-cytosine and 5-methyluracil (35–70% of controls) and markedly reduced in 1-, 7- and N²N²-methylguanines (15–30% of controls). These data suggest that specific types of methylations occur at particular times during the processing of pre-tRNAs.     

The effect of actinomycin D on the formation of gametangia and mitosporangia in Allomyces

The effect of actinomycin on gametangium and mitosporangium production in Allomyces arbuscula and A. macrogynus has been investigated. Male gametangium production was not more sensitive to actinomycin than female development. Actinomycin at 20 g/ml added at the commencement of induction was completely inhibitory. The process became insensitive to actinomycin just before the first septum was laid down.     

The effect of actinomycin D and flavomycin onEscherichia coli R+ strains

When tested by¹⁴C-uracil incorporation, a higher permeation of actinomycin D into R⁺ Escherichia coli cells was observed. From actinomycin D and flavomycin only flavomycin was found to be effective in R⁺ cells selective growth inhibition. The results indicate that the effect of flavomycin is related to the fertility functions of the strain. The possible practical importance of flavomycin application for R⁺ cells elimination in the bacterial population is discussed.     

Study of the chondriome in SPEV cell culture after treatment with actinomycin D

It is shown that the 12-hour treatment of cell with actinomycin D (AMD) in the concentration of 0.05 microgram/ml disturbs a correlation between the morphological cycle of mitochondria and phases of the mitotic cell cycle which is characteristic of intact cells. An increase in the total number of mitochondria independent of phase is observed in all the cells in comparison with intact cells. At the same time a decrease in the amount of branched organellae and appearance of giant mitochondria are discovered. All mitochondria are in the condense form. These changes, perhaps, are a result of the inhibition of the rRNA synthesis in the nucleus and of the protein synthesis in the cell found with it by AMD. The possibility of the immediate interaction of AMD with membrane components of the cell, which induces changes in the ion concentrations and peroxidation of the membrane lipids is not excluded.