[Prooxidant and cytotoxic action of N-acetylcysteine and glutathione combined with vitamin Bl2b].

We studied the prooxidant and cytotoxic action of thiols N-acetylcystein (NAC) and glutathione (GSH) combined with vitamin Bl2b. The synergism of action of the thiols and Bl2b resulted in human carcinoma cell damage was found. It was shown that GSH and NAC in physiological doses combined with Bl2b caused the initiation of apoptosis. It was established that prooxidant action of the thiols combined with vitamin Bl2b, i. e. generation and accumulation of hydrogen peroxide in culture medium, led to intracellular oxidative stress and injury of cell redox system. These effects were completely abolished by nonthiol antioxidants catalase and pyruvate. The chelators of iron phenanthroline and deferoxamine did not suppress the H2O2 accumulation in culture medium but significantly inhibited the cell death induced by the thiols combined with Bl2b. Therefore, the thiols GSH and NAC widely used as antioxidants, in combination with vitamin Bl2b show prooxidant characteristics and induce, with the participation of intracellular iron, apoptotic HEp-2 cell death.

[The role of intracellular pH in regulation of NS/O myeloma cell growth and death]. / Rol' vnutrikletochnogo pH v reguliatsii rosta i gibeli kletok mielomy NS/O.

Measurements of intracellular pH (pHi) were taken in the course of NS/O myeloma cell proliferation, growth arrest and death. Cell proliferation was shown to take place within a wide range of various pHi values (6.8-7.2), in which cell death could also occur. In dense cultures, after ceasing proliferation the apoptosis pathway of cell death was activated practically without pHi changes. Both proliferation and cell death stimulation were noticed in serum-free medium with apoptosis prevalence up to 72 h. Apoptotic death occurred at various intracellular pH values within the range from 6.5 to 7.2. The data obtained provide the ground to suppose that in contrast to normal cells, the pHi value in NS/O myeloma tumor cells was not a regulator of their proliferation and death. The decrease of cell growth and increase of cell death can take place with put pHi alteration.

[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.

[Structure-activity determination of physiological reactions of vasopressin and its analogs on the hemostasis system]. / Strukturno-funktsional'naia obuslovlennost' fiziologicheskikh reaktsiivasopressina i ego analogov na sistemu gemostaza.

Effects of vasopressin, its C-terminal fragments and derivatives on the system of hemostasis were studied in rats. Modification of amino acid sequence in vasopressin molecule led to distinct alterations in main peptide properties. Presence of ring structure in the peptide molecule appears to be obligatory to increase the content of factor VIII in blood, while absence of glycine in side chain caused a decrease in the rate of fibrinolysis and in activity of plasminogen activators.

[Mechanism of cell death in myeloma NS(O) in culture]. / Mekhanizm gibeli kletok mielomy NS(O) v kul'ture.

We studied in vitro myeloma cell death in a serum-free medium. Spectrophotometric assessment of DNA fragmentation, flow cytometry, and staining by Hoechst dye and ethidium bromide indicate that by the beginning of the third day cell death largely followed the apoptotic pathway. We studied dynamics of intracellular pH (pHi) during the cell death and the relationship between the pHi and apoptosis induction during cultivation in media with different pH. We have shown that decreasing pHi in the course of cell death is a consequence rather than the cause of myeloma cell death. Apoptosis took place at cultivation in the media with pH 6.3 and 8.1; the corresponding pHi values were 6.5 and 7.2, respectively. In the presence of Ca-ionophore A23187 we observed appearance of the cells with aberrant distribution of chromatin and fragmented nucleus; however calcium binding in the media with 5-10 mM EDTA induced even more pronounced nuclei fragmentation. This may indicate that both increased and decreased concentration of intracellular calcium induce NS(O) myeloma cell apoptosis.

[Effect of vasopressin and its analogs on blood coagulation in rats]. / Vliianie vazopressina i ego analogov na svertyvanie krovi u krys.

A change in the response of the blood coagulation system to the intravenous injection of vasopressin (AVP), DDAVP and DGAVP has been studied in the experiments on white rats. Intensification of the procoagulant activity on AVP is of the dose-dependent character. Maximal effect is observed 5-15 min after i.v. injection of AVP in a dose of 4 mg/kg. The administration of this peptide increases the fibrinolytic activity, that is connected with an increase in the level of plasminogen activator. DDAVP and DGAVP have a weaker effect on fibrinolysis. AVP and DDAVP increase the level of FVIII by 5-6% during the first minutes, but DGAVP increases the level of FVIII only after 15-30 minutes. While using AVP, DDAVP and DGAVP in clinical practice it is necessary to allow for their hormonal action, the initial state of haemostasis and the age of patients.

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.

Oxidative stress in HEp-2 human laryngeal carcinoma cells induced by combination of vitamins B12b and C.

Incubation of human laryngeal epidermoid carcinoma HEp-2 cells with hydroxocobalamin (vitamin B12b) and ascorbic acid (vitamin C) for 1 h initiated oxidative stress accompanied by damage to mitochondria and increase in intracellular oxidative activity. Studies of the kinetics of these processes showed that the increase in intracellular H2O2 activity and mitochondrial damage are more likely a result, but not the cause of cell apoptosis during the first hour of their incubation with vitamins B12b and C.

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.