[Large-scale fragmentation of dna and the death of tumor cells by the action of the binary system ascorbic acid-metallocomplexes of cobalt in vitro].

High-molecular-weight DNA fragments are the markers of the early stage of apoptosis induced in eukaryotic cells by cytotoxins of different nature. The dynamics of the development of large-scale DNA fragmentation in K-562 leukemia cells by the action of the antitumor drug, the binary system ascorbic acid--cobalt phthalocyanine within 48 h of incubation, which correspond to two periods of the doubling of cell number in growing control cultures, have been studied. It was shown that, within the first hours of incubation, hydrogen peroxide generated by the system induces the formation of DNA fragments from 2200 to 50 kbp long. Later on the cell death accompanied by a decrease in the content of fragmented DNA is observed. Within 24 h of incubation, part of fragmented DNA remains unrepaired; after 48 h of incubation, a delay or a slowed down proliferation of K-562 cells, which differ from control cells also by a high level of death and a higher content of high-molecular-weight DNA fragments, is observed.

Generators of reactive oxygen forms gamma-irradiation and ascorbic acid--cobalt metallocomplexes induced large-scale fragmentation and reparation of DNA in tumor cells.

It was demonstrated that ascorbate-cobalt phthalocyanine complex produces a time-dependent nuclease effect on leukemia K-562 cells is. Catalase added to the incubation medium prevented or blocked fragmentation of cell DNA. The size of large-scale fragments formed during irradiation and exposure to the above system varied from 2200 to 30 kbp. The fragments induced by the system recombined slower than the fragments induced by g-irradiation in a dose adequate by the level of DNA damage. This effect observed previously in HEp-2 carcinoma cells exposed to the action of the B12b+C vitamin system can be explained by generation of H(2)O(2) inducing more severe damage to DNA structure than gamma-radiation due to site-specific Fenton reaction.

Apoptotic death of human lympholeukemia HL-60 cells resultant from combined effect of cobalt octa-4,5-carboxyphthalocyanine propylenglycol ether and ascorbate.

Cobalt octa-4,5-carboxyphthalocyanine propylenglycol ether proposed for antitumor therapy potentiates the cytotoxic effect of ascorbate on HL-60 human leukemia cells. Combination of these substances caused the formation of H2O2 in the medium and initiated apoptotic death of cells. Catalase abolished the cytotoxic effect of this combination. The results indicate that binary catalytic system of this combination can be regarded as a potential antitumor agent.

Combined treatment with vitamin B12b and ascorbic acid causes in vitro DNA degradation in tumor cells.

Incubation of Ehrlich ascites carcinoma and HEp-2 human epidermoid laryngeal carcinoma cells with hydroxycobalamin (vitamin B12b) and ascorbic acid induced generation and accumulation of double-stranded DNA fragments (23,000 b.p. and longer) in cells. The same vitamins alone in the same concentrations produced no such effects. DNA degradation in HEp-2 cells caused by long-term (4 h) incubation with 5-25 microM hydroxycobalamin and ascorbic acid (1:10-1:40 molar ratio) at 37 degrees C was comparable with that induced by gamma-irradiation in a dose of 150 Gy at 4 degrees C.

[DNA degradation and repair in human laryngeal carcinoma HEp-2 cells after combined exposure to vitamin B12b and ascorbic acid]. / Degradatsiia i reparatsiia DNK v kletkakh épidermoidnoi kartsinomy gortani cheloveka HEp-2 pri sovmestnom deistvii vitamina B12b i askorbinovoi kisloty.

The formation and accumulation of DNA fragments containing no more than 23,000 pairs of bases were observed under exposure of human larynx epidermoid carcinoma cells (Hep-2) to "chemical nuclease", oxycobalamin (vitamin B12b) and ascorbic acid (vitamin C). The obtained DNA damages were repaired more slowly than those induced by gamma-irradiation in the dose adequate to the level of DNA damages. DNA reparation was not revealed after washing the cells from vitamin B12b and ascorbic acid, and in the course of cell incubation with ascorbic acid. Vitamin B12b and ascorbic acid separately did not induce degradation of DNA. DNA damages induced by "chemical nuclease" action precede the cell death observed later.

[The effect of lead on DNA repair in thymocytes of gamma-irradiated mice]. / Deistvie svintsa na reparatsiiu DNK v timotsitakh gamma-obluchennykh myshei.

The effects of Pb on the repair of DNA have been studied in the thymocytes of gamma-irradiated mice exposed to diacetate lead in the drinking water (up to 20 mg/l) for 14-50 days. It is found that lead causes no DNA degradation by itself and renders its genotoxic action indirectly, via inhibiting the repair of single-strand DNA breaks induced by acute gamma-irradiation of mice. Genotoxic effect of lead is reversible that becomes evident when exposed animals are maintained on Pb-free drinking water for 1-2 weeks.

[Study of combined chronic effects of gamma radiation and lead on the occurrence and repair of DNA injury in mice]. / Issledovanie sochetannogo khronicheskogo vozdeistviia gamma-radiatsii i svintsa na obrazovanie i reparatsiiu povrezhdenii DNK u myshei.

It has been shown that neither exposure of mice to lead in the drinking water (20 mg/l) for 50 days nor chronic gamma-irradiation of animals (1.5 Gy, 1.3 mGy/h, 50 days) induces single-stranded DNA breaks in thymocytes. Acute gamma-irradiation (1 and 4 Gy) of lead-pretreated mice resulted in an inhibiting of repair of radiation-degraded DNA in thymocytes and in an increasing of the level of DNA lesions detected in erythroblasts of bone marrow by the micronuclear test method. Inhibition of ssDNA break repair in thymocytes caused by lead was not seen upon exposure of mice to combined chronic action of gamma-irradiation and lead. Chronic irradiation did not affect the micronuclei rate increase revealing after acute irradiation of lead-treated mice.

[The effect of gamma irradiation on the content in the thymus and liver chromatin of rats of DNA-bound proteins resistant to dissociation by phenol and sodium dodecylsulfate]. / Vliianie gamma-oblucheniia na soderzhanie v khromatine timusa i pecheni krys DNK-sviazannykh belkov, ustoichivykh k dissotsiatsii fenolom i dodetsilsul'fatom natriia.

Two groups of proteins of 50-68 kD (A) and 12-14 kD (B) are the components of DNP preparations from rat thymus and liver obtained by washing with 0.075 M NaCl-0.024 M EDTA solution and deproteinization with phenol and dodecylsulfate (SDS). Immediately after irradiation with a dose of 10 Gy, there observed an approximately 1.5-fold increase in the content of only B proteins in the rat thymus fraction precipitated upon treatment with SDS-NaCl. The acidic amino acid content of this fraction and DNP preparation obtained without treatment with SDS amounts to 25 mol%; the ratio to basic amino acids was 1.3-1.4. The comparison of the amino acid content in the above DNP preparation and the "supramolecular DNA" preparation, described in the literature, that was obtained by the same phenol deproteinization and contained about 50 mol% of acidic amino acids, indicates the presence in the "supramolecular DNA" preparation of a component that increases upon irradiation: the component consists almost completely of acidic amino acids and is eliminated completely from the DNP preparation by washing with 0.075 M NaCl-0.024 M EDTA prior to deproteinization. The amino acid composition of the protein fraction A is presented.

[Acid polypeptides as intensifiers of the formation of irreparable double-stranded DNA breaks induced by the gamma irradiation of mammalian cells]. / Kislye polipeptidtidy kak usiliteli obrazovaniia nereparirovannykh dvunitevykh razryvov DNK, indutsirovannykh gamma-oblucheniem kletok mlekopitaiushchikh.

Acid polypeptides, synthetic analogues of a natural modifier of lethal effect of radiation, were shown to inhibit double-strand DNA breaks (DSB) repair, to increase irreparable DSB accumulation and to enhance the formation of structural chromosome rearrangements in gamma-irradiated mammalian cells. The authors discuss the possibility of involvement of proteins, that contain amino acid sequences comparable, in length, with a modifier, into radiation formation of irreparable DSB.

[The inhibition by strongly acidic polypeptides of the repair of double-stranded DNA breaks induced by the gamma irradiation of Chinese hamster fibroblast cells]. / Ingibirovanie sil'nokislymi polipeptidami reparatsii dvunitevykh razryvov DNK, indutsirovannykh gamma-oblucheniem kletok fibroblastov kitaiskogo khomiachka.

The ability of polypeptides consisted of aspartic and glutamic acids to inhibit the repair and to promote the formation of unrepaired double-strand DNA breaks and chromosomal aberrations in gamma-ray induced Chinese hamster cells was shown. A complete inhibition of the double-strand DNA breaks repair was observed at the concentrations of 20 mu M/l (polyglutamic acid with molecular weight 2000-15,000 daltons) and 100 mu M/l (aspartylglutamic acid with molecular weight 1500-4500 daltons). Both polypeptides were low toxic at the given concentrations.

[Stimulation of mitochondrial oxidative enzymes in acute cooling and its catecholamine mechanisms]. / Stimuliatsiia okislitel'nykh fermentov mitokhondrii pri ostrom okhlazhdenii i ee katekholaminovye mekhanizmy.

Acute cooling of rats led to stimulation of NAD+-dependent isocitrate dehydrogenase (ICDH), succinate dehydrogenase (SDH) and NAD(P)+-transhydrogenase (TH) but did not affect the NADP+-ICDH activity in liver, heart and skeletal muscle mitochondria. After pretreatment of the animals with propranolol the stimulating effect was decreased, thus suggesting that endogenous catecholamines and beta-adrenoreceptors are of importance in activation of NAD+-ICDH, SDH and TH. The effects of cooling, noradrenaline and cAMP did not summarize. Role of catecholamines in stimulation of mitochondrial oxidative enzymes under conditions of cooling is discussed.

[Densitometric determination of nucleic acids in gels after electrophoresis]. / Densitometricheskoe opredelenie nukleinovykh kislot v geliakh posle élektroforeza.

A technique for the quantitative determining of nucleic acids after electrophoresis by double-wave densitometry in UV spectrum by scanning agar gel along both axes was developed. Optical characteristics of agar and acrylamide-agar gels are given. The range of quantities measured is 6 divided by 30 micrograms of DNA per gel; the standard deviation adjusted to 1 microgram is less than +/- 3%.

[Interaction of a natural modifier of lethal effect of radiation with HeLa cells]. / O vzaimodeistvii prirodnogo modifikatora letal'nogo deistviia radiatsii s kletkami HeLa.

Polypeptide 14C-aspartyl glutamate, a chemical analogue of a natural modified of a lethal effect of radiation, has been synthesized. The modifier was shown to react readily with nucleic acids and proteins of non-irradiated cells: the reaction was considerably enhanced when the modifier was administered simultaneously with radiation of cells. As is known from the literature, a molar concentration of the incorporated polypeptide is considerably lower than the intracellular molar concentration of an active radiosensitizer, BUdr, which produces an effect on mammalian cells comparable with that of polypeptide.