Effects of ethidium bromide in diploid and duplication strains of Aspergillus nidulans.

Unstable duplication and diploid strains of Aspergillus nidulans were treated with ethidium bromide, and it was shown that this drug reduces the number of sectors produced by such strains. The mechanisms which could be responsible for the partial stabilization of the strains are discussed and it is suggested that a similar mechanism is responsible for the production of sectors in both strains. It is also suggested that ethidium bromide could be useful for the reduction of instability of industrial strains.     

Resistance to ethidium bromide inAspergillus nidulans

Summary A mutant ofAspergillus nidulans resistant to ethidium bromide was isolated and the semi-dominant gene responsible for this resistance was allocated on linkage group II at 17.42±3.05 units of recombination from thewA₃ gene. The gene also confers cross-resistance to acriflavin, malachite green and crystal violet. It was also shown that riboflavin is antagonistic to the toxic effect of ethidium bromide, at certain concentrations. The mechanisms which could be responsible for the toxic effect of this drug are discussed and compared with those of acriflavin. The use of theEtb ₁ gene in genetical analysis through the parasexual cycle is suggested.Acknowledgements. The authors are thankful to the National Council for the Development of Science and Technology (CNPq) for financial support through PIG-SIP 04/053 FAPESP.     

Comparison of the effects of ethidium bromide and of the ethidium bromide-deoxyribonucleic acid complex in Ehrlich tumor cells]

When injected into the peritoneal cavity, ethidium bromide can strongly inhibit the multiplication of mouse Ehrlich ascites tumour cells. This antitumour effect is increased when ethidium bromide is linked to DNA and also injected into the peritoneal cavity. The cellular alterations are identical after a treatment with E.B. either free or bound to DNA. However, when the cells are treated with E.B.-DNA they contain E.B. for a longer period than after a treatment with E.B.     

Effect of intercalating mutagens on crossing-over inDrosophila melanogaster females

Summary In order to evaluate the effect of several intercalating compounds on crossing-over inDrosophila melanogaster females, acridine orange, acriflavine, chloroquine, ethidium bromide and quinacrine were fed separately to larvae ofy ct f/+++ genotype. Our results show that acridine orange, acriflavine and ethidium bromide increase significantly the recombination frequency at thect-f region and support the view that, for intercalating agents, there is a relationship between clastogenic activity and female recombination induction.     

Inhibition of fading in fluorescence microscopy of fixed cells.

Following Hirschfeld et al., dithionite was added to mounting media to inhibit fluorescence fading. Excellent response is reported for fluorescein, acridine orange, 33258 Hoechst, acriflavine, berberine (and ethidium bromide), but not for quinacrine.     

Effect of ethidium bromide onDrosophila melanogaster andDrosophila simulans

Summary Ethidium bromide was fed toD. melanogaster andD. simulans males in order to test its toxic capacity and potency for the induction of dominant lethals. Our results show that ethidium bromide has a high toxicity and likewise produces dominant lethals to a significant extent in both species, but more effectively inD. melanogaster.     

Inhibition of fading in fluorescence microscopy of fixed cells

Summary Following Hirschfeld et al., dithionite was added to mounting media to inhibit fluorescence fading. Excellent response is reported for fluorescein, acridine orange, 33258 Hoechst, acriflavine, berberine (and ethidium bromide), but not for quinacrine.Acknowledgment. The author is grateful to Dr T. Hirschfeld of Block Engineering, Cambridge, Mass., USA, for an illuminating introduction to his work.     

Observations of a certain arrangement in the nucleolar chromatin after continuous ethidium bromide treatment

Summary This work is an ultrastructural and cytochemical study of a structure observed in the nucleolus of Allium cepa meristematic cells after nucleolar disgregation, by a continuous treatment of 12 h with ethidium bromide. The ultrastructural and cytochemical data allow us to consider this structure as the intranucleolar chromatin collapsed by the effect of the drug.     

Fluorometric estimation of dead cells in cell suspensions

Summary An objective vitality test is proposed. It is based on the fluorescence increment of ethidium bromide in the presence of dead cells, which is proportional to cellular DNA under conditions previously defined.Acknowledgments. The skilful technical assistance of Ms G. Roloff is gratefully acknowledged. Fluorometric measurements have been performed at the Division of Cellular and Molecular Cardiology, Central Institute of Heart and Circulatory Regulation Research Berlin-Buch.     

Visualization of DNA in various phages (T4, χ, T7, ϕ 29) by ethidium bromide epi-fluorescent microscopy

Summary DNA-containing areas in various phages (T4, , T7 and 29) could be observed at the light microscopic level using ethidium bromide epi-fluorescent microscopy. The fluorescent intensity per phage was in linear proportion to the DNA content in each phage.Acknowledgements. This work was supported in part by the grant No. 521708 and No. 511212 from the Japan Ministry of Education, Science and Culture.     

Differential sensitivity to ethidium bromide of replicative DNA synthesis and bleomycin-induced unscheduled DNA synthesis in permeable mouse sarcoma cells

Replicative DNA synthesis in permeable mouse sarcoma cells was more sensitive to ethidium bromide (EtBr) than bleomycin-induced unscheduled DNA synthesis (UDS). A similar difference in sensitivity to EtBr was observed between DNA polymerases alpha and beta. The difference in sensitivity to EtBr of replicative DNA synthesis and UDS in the present system seems to reflect mainly the sensitivity difference between DNA polymerases alpha and beta.     

Plasmids controlling the resistance to several antibiotics in C. perfringens type A, strain 659]

A strain of C. perfringens type A, isolated from a patient, was found to be resistant to four antibiotics: tetracycline (Tet), chloramphénicol (Chl), erythromycin (Ero) and clindamycin (Cli). Clones resistant to only two drugs (Tet-Chl or Ero-Cli), or sensitive to all drugs were found in cultures of the wild-type strain treated by acridine dyes or ethidium bromide. DNA analysis by equilibrium centrifugation confirmed that the original strain contains two resistance plasmids, one called Rip 401 (Tet-Chl) and the other Rip 402 (Ero-Cli), which represent respectively 1.8 +/- 0.2% and 2.3 +/- 0.2% of the total amount of DNA in this strain of Cl. perfrigens.     

Implication of GABA in the spatial organization of the receptive fields of retinal ganglia cells of frogs]

An histoautoradiographic study of the Chicken and Frog retinae was made following an intravitreal injection if tritiated GABA. This amino acid was especially fixed at the amacrine and horizontal cell level. It has been suggested (Werblin, 1974) that horizontal cells might be responsible for the spatial organization of the receptive fields of retinal ganglion cells. GABA could thus be involved in bringing about of the centre-surround arrangement of the latter receptive fields. We have shown that picrotoxin, a specific GABA-antagonist, does indeed provoke marked changes in the activity of retinal ganglion cells. It provokes a decrease in the response threshold, a facilitation of spontaneous activities, and a marked increase in the receptive field area of the ON-OFF ganglion cells: from 12 at the start, it reaches 24 under the effect of picrotoxin.     

Interaction of smooth muscle relaxant drugs with calmodulin and cyclic nucleotide phosphodiesterase

Some smooth muscle relaxant drugs with an unknown mechanism of action have been tested for their interaction with calmodulin and with calmodulin-induced cyclic nucleotide phosphodiesterase (PDE) activity. The affinity of these drugs for calmodulin does not parallel their inhibitory effect on the calmodulin activation of PDE. The lack of parallelism could be due to a binding of the drugs to different sites on calmodulin; furthermore a binding of papaverine, octylonium bromide and felodipine to PDE molecule might also be considered to explain their inhibitory effect on PDE basal activity. The myolytic effect of octylonium bromide and pinaverium bromide may be due to their interaction with calmodulin-dependent systems.     

Dual role of cAMP duringDictyostelium development

cAMP plays an essential role duringDictyostelium development both outside and inside the cell. Membrane-bound receptors and adenylyl cyclase are responsible for sensing and producing extracellular cAMP, whereas a phosphodiesterase is responsible for maintaining a low basal level. The molecular events underlying this type of hormone like signalling, which are now beginning to be deciphered, will be presented, in the light of cAMP analogue studies. The importance of intracellular cAMP for cell differentiation has been demonstrated by the central role of the cAMP dependent protein kinase. Mutants as well as strains obtained by reverse genetics will be reviewed which lead to our current understanding of the role of intracellular cAMP in the differentiation of both stalk and spore cells.     

Interaction of smooth muscle relaxant drugs with calmodulin and cyclic nucleotide phosphodiesterase

Summary Some smooth muscle relaxant drugs with an unknown mechanism of action have been tested for their interaction with calmodulin and with calmodulin-induced cyclic nucleotide phosphodiesterase (PDE) activity. The affinity of these drugs for calmodulin does not parallel their inhibitory effect on the calmodulin activation of PDE. The lack of parallelism could be due to a binding of the drugs to different sites on calmodulin; furthermore a binding of papaverine, octylonium bromide and felodipine to PDE molecule, might also be considered to explain their inhibitory effect on PDE basal activity. The myolytic effect of octylonium bromide and pinaverium bromide may be due to their interaction with calmodulin-dependent systems.     

Serum-induced stimulation of snRNA synthesis in mouse 3T3 fibroblasts

Small nuclear RNAs (snRNAs) from quiescent and serum-stimulated 3T3 cultures, labeled with [3H]uridine [( 3H]U), were electrophoresed in polyacrylamide-urea slab gels and revealed by staining with ethidium bromide and by fluorography. Judged by labeling with [3H]U, synthesis of 7S and U1-U6 RNAs was very low or absent in quiescent cultures. The serum-induced transition of 3T3 cells from a resting to a growing state was accompanied by an early, apparently sequential stimulation of snRNA synthesis; stimulated synthesis of 7S, U1, U2, U3, U4 and U6 RNAs coincided in time with serum-induced stimulation of 45S pre-ribosomal RNA (pre-rRNA) and heterogeneous nuclear RNA (hnRNA) synthesis.     

The biochemistry of ancient DNA in bone

The amount of DNA in ancient bone was determined by ethidium bromide staining after the removal of the potent Taq inhibitor, fulvic acid. A complete decalcification and a perfusion protocol were used to recover DNA from bone. A variety of purification techniques including molecular sieve, hydroxyapatite binding and Magic preparations yielded DNA that spanned from 3.4g/g of bone to below detectable limits. Fulvic acid was shown to interfere with the quantification of DNA derived from ancient human skeletal material one hundred to over seven thousand years old. Scanning UV in the 300 to 230 nm range is a simple and sensitive technique for documenting fulvic acid contamination in ancient bone extracts.     

Serum-induced stimulation of snRNA synthesis in mouse 3T3 fibroblasts

Summary Small nuclear RNAs (snRNAs) from quiescent and serum-stimulated 3T3 cultures, labeled with [³H]uridine ([³H]U), were electrophoresed in polyacrylamide-urea slab gels and revealed by staining with ethidium bromide and by fluorography, Judged by labeling with [³H]U, synthesis of 7S and U1-U6 RNAs was very low or absent in quiescent cultures. The serum-induced transition of 3T3 cells from a resting to a growing state was accompanied by an early, apparently sequential stimulation of snRNA synthesis; stimulated synthesis of 7S, U1, U2, U3, U4 and U6 RNAs coincided in time with serum-induced stimulation of 45S pre-ribosomal RNA (pre-rRNA) and heterogeneous nuclear RNA (hnRNA) synthesis.