PubMed Health⌕ Search

Biomedical subjects

N G Stepanova

Publications and source records attributed to N G Stepanova.

At least 19 recordsLinked to original sources
PubMed1987

[Fluorescence cytochemistry of nucleic acids. The current status and outlook: on the 35th anniversary of the method].

Most important fields of the fluorescence cytochemistry of nucleic acids are reviewed, special attention being paid to the following aspects of the problem: physicochemical basis of different methods of staining; new methods of cell analysis, including flow cytometry; functional studies, i.e. the use of fluorescence approaches to obtain information about the functional state of individual cells and cell aggregates.

Animals↗
PubMed1987

[Formation of a pentose phosphate cycle metabolite, erythrose-4-phosphate, from initial compounds of glycolysis by transketolase from the rat liver].

Using ion-exchange chromatography of sucrose phosphates on Dowex-1, it was demonstrated that the highly purified rat liver transketolase (specific activity 1.7 mumol/min.mg protein) is capable of catalyzing the synthesis of erythrose-4-phosphate, a metabolite of the pentose phosphate pathway non-oxidizing step, from the initial participants of glycolysis, i. e., glucose-6-phosphate and fructose-6-phosphate. As can be evidenced from the reaction course, the second product of this synthesis is octulose-8-phosphate. The reaction was assayed by accumulation of erythrose-4-phosphate. The soluble fraction from rat liver catalyzes under identical conditions the synthesis of heptulose-7-phosphate (but not erythrose-4-phosphate), which points to the utilization of the erythrose-4-phosphate formed in the course of the transketolase reaction by transaldolase which is also present in the soluble fraction. The role of the transketolase reaction reversal from the synthesis of pentose phosphate derivatives to glycolytic products is discussed. The transketolase reaction provides for the relationship between glycolysis and the anaerobic step of the pentose phosphate pathway which share common metabolites, i. e. glucose-6-phosphate and fructose-6-phosphate.

Animals↗
PubMed1985

Application of 7-amino-actinomycin D for the fluorescence microscopical analysis of DNA in cells and polytene chromosomes.

The cytochemical properties of a guanine-specific synthetic fluorescent analogue of actinomycin D, 7-amino-actinomycin D, have been studied in fixed and living preparations of L cells and polytene chromosomes of salivary glands of Chironomus thummi thummi and Drosophila lummei (Hackman). 7-Amino-actinomycin D has been shown to bind to DNA-containing structures, thereby inducing in them a bright red fluorescence. No specific fluorescence has been found in RNA-containing structures treated with this fluorescent probe. The fluorescence pattern of some regions of polytene chromosomes with a known nucleotide composition was analysed. It has been established that 7-amino-actinomycin D induces a very weak fluorescence in GC-poor chromosome regions of the Drosophila lummei toromere structure. Data indicating a nonlinear dependence between the fluorescence intensity of a stained chromosome region and the GC content in its DNA have been obtained. The influence of DNA nucleotide composition in a chromosome region on the fluorescence of 7-amino-actinomycin D is discussed. In combination with quinacrine staining and the Feulgen fluorescence reaction, treatment with 7-amino-actinomycin D provides useful information about the distribution of GC base pairs in the chromosome region under study.

Animals↗
PubMed1984

7-Amino-actinomycin D as a specific fluorophore for DNA content analysis by laser flow cytometry.

A technique for DNA amount determination by flow cytometry based on the use of 7-amino-actinomycin D (7-amino-AMD), a fluorescent analogue of antibiotic actinomycin has been investigated, and a particular staining procedure has been developed. The procedure includes short fixation in 70% ethanol and staining for 20 min in 10(-5)M solution of 7-amino-AMD at pH7. The results of DNA content measurements are very reproducible. The histograms obtained have a coefficient of variation less than 3%. The absorption maximum of the complex of 7-amino-AMD with DNA is situated in the green spectrum region, making this stain particularly suitable for argon laser flow cytometry.

Animals↗
PubMed1984

[Fluorescence microscopic and autoradiographic analyses of the differential reaction of various regions of polytene chromosomes in Chironomus to prolonged exposure to 7-amino-actinomycin D and 3H-actinomycin D].

Dynamics of binding of a fluorescent analogue of actinomycin D -- 7-amino-actinomycin D -- and 3H-actinomycin D with polytene chromosomes of Ch. thummi was studied. Biological effects of AMD, 7-amino-AMD, and 3H-AMD on polytene chromosomes were found to be similar. These ligands provoke the reduction of the nucleolus and Balbiani rings and the appearance of giant pseudo-puffs in heterochromatic centromere regions of polytene chromosomes. There was no intermediate binding of 7-amino-AMD to DNA in vivo both after a longterm treatment of larvae with fluorochrome and in chase experiments. It was found that a loosening of chromatin in centromere regions accompanied by a weakening of its fluorescence took place in the formation of pseudo-puffs. Possible mechanisms of pseudo-puff formation under the influence of AMD and 7-amino-AMD are discussed. Essential factors may be peculiarities of DNA nucleotide composition in centromere regions, DNA packing, alteration of physico-chemical properties of DNA in the complex with AMD (despiralizations and elongation), and an inhibition of RNA synthesis necessary for the maintenance of normal structure of polytene chromosomes.

Animals↗
PubMed1977

Differential staining of Chironomus thummi giant chromosomes by treatment with acridine orange after mild acid hydrolysis.

The fluorescence of Chironomus thummi giant chromosomes stained by acridine orange after mild acid hydrolysis (1N HCl at 37 degrees) has been studied. After very short hydrolysis as well as in control preparations (untreated by HCl) all chromosome regions show green fluorescence. After long hydrolysis (10 min) all chromosome bands fluoresce red. Intermediate time of hydrolysis (2 min) give in all transcriptionally inactive bands including centromeric ones red fluorescence whereas transcriptionally active puffing regions are green. The possible mechanisms of differential staining of individual chromosome regions are discussed. It is suggested that transcriptionally active chromosome regions are less susceptible to the action of acid or that the difference in chromatin stainability after acid-AO treatment is due to the difference in chromatin packing. The applicability of this method to the study of functional states of chromatin, at least in giant chromosomes, is discussed.

Acridines↗
PubMed1976

Use of actinomycin D for the specific quenching of fluorescence of deoxyribonucleic acid in cells stained with acridine aminoderivatives.

Actinomycin D specifically quenches the fluorescence of acridine orange and quinacrine bound to deoxyribonucleic acid in cytologic preparations, but does not change the fluorescence of these fluorochromes bound to RNA. The following fluorescence-cytochemical applications of techniques based on these findings can be suggested: (a) distinction between deoxyribonucleic acid and ribonucleic acid; (b) detection of double-stranded virus ribonucleic acid; (c) approximate estimation of the lengths of A-T sequences in deoxyribonucleic acid molecules.

Acridines↗
PubMed1976

[Sedoheptulose-1,7-diphosphate as a source of pentose phosphates in heart muscle].

A possibility and some peculiarities of phosphatase degradation of sedoheptulose-1,7-diphosphate in the myocardium has been demonstrated. The reaction products are inorganic phosphate and sedoheptulose-7-phosphate; the latter product is the substrate of the transketolase reaction during pentose phosphates production. The process is largely localized in the soluble fraction of heart cells; in cellular organelles it is represented in a lesser degree. Possible regulatory mechanisms of pentose phosphate biosynthesis in animal tissues are discussed.

Animals↗