Expression and activity of 2-5A synthetase in the course of differentiation and apoptosis of PC12 cells.

The role of IFN-induced 2-5A system in cell differentiation has not been elucidated. While studying differentiation of PC12 cells we found that the simultaneous treatment of cells with NGF and IFN-gamma in serum-containing medium resulted first in the extension of neurites and then apoptosis. On the contrary, in serum-free medium the cells underwent a more rapid neuronal differentiation. Only the doses of NGF which induced the outgrowth of neurites from the cells were able to induce rapid cell death in combined treatment. When the cells were treated subsequently with NGF and IFN-gamma, the induction of death was observed with NGF post-treatment, but not with NGF pretreatment. Relying on these alternative biological responses, we studied the changes in 2-5A synthetase activity and its 43 kDa isoform expression in the course of differentiation and death of PC12 cells. The results of the present work showed that NGF-induced differentiation of the cells did not evoke any increase in 2-5A synthetase activity or any increase in the expression of its 43 kDa isoform. Moreover, the obtained results demonstrated that NGF could not significantly affect the IFN-induced signalling pathway leading to the activation of 2-5A synthetase gene, at least regarding the studied enzyme activity.

The effect of 9,11-secosterol, a newly discovered compound from the soft coral Gersemia fruticosa, on the growth and cell cycle progression of various tumor cells in culture.

A new 9,11-secosterol, 24-nor-9,11-seco-11-acetoxy-3 beta,6 alpha-dihydroxycholest-7,22(E)-dien-9-one, was found to exhibit growth inhibitory (IC50 below 10 microM) and cytotoxic activities against human leukemia K562, human cervical cancer HeLa, and Ehrlich ascites tumor cells in vitro. The cytostatic concentrations of the compound generally caused the G2/M block in the cell cycle progression, but differences between the three tumor cell lines in the events leading to cell death were remarkable. While inhibiting cell proliferation, 9,11-secosterol caused accumulation of HeLa and K562 cells in the metaphase of mitosis. So, abnormal mitosis can play an important role in the cytotoxicity of 9,11-secosterol in these cell lines. In the Ehrlich ascites tumor cell line the increasing concentrations of the drug (up to 40 microM) did not cause an immediate cell killing. Instead, due to continued DNA synthesis without entry into mitosis, cells with high DNA ploidy were produced. It was shown that the cytoskeletal systems such as microtubules and microfilaments were not damaged by the action of 9,11-secosterol. Further studies are necessary to elucidate the mechanism of the cytotoxic effect of 9,11-secosterol.

Comparative fluorometric study of benzo(a)pyrene and aza-aromatic hydrocarbon penetration and metabolism kinetics in the skin of hairless mice.

The kinetics of penetration and metabolism of BaP, BACs, DB(a,h)ACs and DB(c,g)Cs in the skin of hairless mice was studied. The relative fluorescence intensities were measured during three hours after applying 10 nmoles of the compound to the interscapular region of the mice. By using a kinetical model which combines a non-steady diffusion of a hydrocarbon through the stratum corneum and the metabolic oxidation by epidermal cells, the rate constants for the two processes were calculated. It has been shown that B(a)AC, B(c)AC and 12-MB(a)AC penetrate into the skin and are oxidized by epidermal cells more efficiently than BaP. In contrast, alkyl-DB(a,h)ACs (except 14-MDB(a,h)AC) show a great stability in the mouse skin. The carcinogenic BaP, 7-MB(c)AC and DB(a,h)AC have average rates of elimination from the skin.

[Synthesis and antiaggregation activity of prostacyclin analogs. II. Direct synthesis of 15-fluoro-13,14-didehydrocarbacyclin]. / Sintez i antiagregatsionnaia aktivnost' analogov prostatsiklina. II. Priamoi sintez 15-ftor-13,14-didegidrokarbatsiklina.

E- and Z-isomers of 15-fluoro-13,14-dehydrocarbacyclin were synthesized starting from 2,3-epoxy-bicyclo[3.3.0]octan-6-one ethylene ketal with the use of 3-fluoro-1-octynydlithium.BF3 reagent and Wittig condensation. The ratio of isomeric the oxirane opening reaction and Wittig olefinization products was in each case 1:1. The synthesized compounds were identified by 13C NMR spectra. The antiaggregating activity of 5E-isomer was 2 x 10(-4) of the activity of corresponding 15-hydroxy compound, 5Z-isomer being even less active.

[Synthesis and antiaggregation activity of prostacyclin analogs. 1. Bicyclo [3.2.0] heptane analogs]. / Sintez i antiaggregatsionnaia aktivnost' analogov prostatsiklina. 1. Bitsiklo [3.2.0] geptanovye analogi.

Bicyclo[3.2.0]heptane analogues of prostacyclin were synthesized starting from 2,3-epoxy-bicyclo[3.2.0]heptane-6-one ethylene ketale by means of alkynydlithium-BF3-reagents and Wittig reaction. The regioselectivity of the oxirane ring opening reaction is 3:2 and stereoselectivity of Wittig olefinization is 1:1. The synthesised compounds were identified by 13C NMR spectra. The antiaggregative activity of the prostacyclin analogues on rabbit blood platelets was 10(-3)-10(-4) of the activity of PGE1, the isomers with (E)-double bond in alpha-chain being by an order more active that the (Z)-isomers. Elongation of the alpha- and omega-side chain by one carbon atom gives 2-4 fold increase of the activity. Bicyclo[3.2.0]heptane analogues of prostacyclin represent-simple and readily obtainable models for elucidation of structure-activity relationship among prostacyclin analogues.

Identification and biological activity of a novel natural prostaglandin, 5,6-dihydro-prostaglandin E3.

A novel natural E-prostaglandin was detected by HPLC among the endogenous prostaglandins extracted from ram seminal vesicles. The corresponding precursor - all-cis-eicosa-8, 11, 14, 17-tetraenoic acid was isolated from bovine liver lipids and the preparative biosynthesis with the microsomal fraction of ram seminal vesicles was performed. The isolated product was purified by HPLC and identified by GC-MS as 5,6-dihydro-PGE3. The results of in vitro tests demonstrate that 5,6-dihydro-PGE3 is 14 times less active uterine stimulant than PGE1, at the same time retaining 75% of the anti-aggregatory potency of PGE1. Thus, 5,6-dihydro-PGE3 meets the requirements of a selective antithrombotic agent more than PGE1.

Fluorescence method for the measurement of penetration and metabolism of carcinogens in mouse skin.

The present study aims at elucidating by fluorescence measurements the possibilities of the mathematical description of the processes of penetration and metabolism of carcinogenic polynuclear arenes in mouse skin. The fluorescence intensities of the topically applied benzo(a)pyrene (BaP), 10-60 nmoles of BaP in 100 microliters of acetone, were measured in the interscapular region of hairless mice during three hours. A kinetic model combining a non-steady diffusion of BaP through the stratum corneum and BaP metabolic oxidation by epidermal cells was elaborated. Both the processes were described by first-order kinetic equations. Four parameters, viz. BaP flux rate constant into the stratum corneum, BaP metabolism rate constant, BaP flux at zero time and relative fluorescence intensity at zero time, can be calculated from experimental data (fluorescence intensity-time) using the kinetic model. The above method makes it possible to study the effect of other compounds, e.g., phenolic antioxidants, on BaP metabolism rates in the in vivo system.

[Kinetics of benzo[a]pyrene penetration into the mouse skin after treatment with various phenols]. / [Kinetika proniknoveniia benz[a]pirena v kozhu myshei pod vliianiem razlichnykh fenolov.

A mathematical method for the study of benzo(a)pyrene (BP) penetration into the skin of nude mice was elaborated and supported by the experimental data. BP, whose concentration was measured by its fluorescence intensity, was applied to the skin using a "dry" technique. The effect of certain phenols and products of oxybenzene oxidation was studied. It was found that only butylated hydroxytoluene inhibits essentially the rate of BP metabolism.

[Effect of metabolites of 7,12-dimethylbenz(a)anthracene on the dynamics of its fluorescence in the skin of hairless mice]. / Vliianie metabolitov 7,12-dimetilbenz(a)antratsena na dinamiku ego fliuorestsentsii v kozhe bezvolosykh myshei

The influence of two metabolites of 7,12-dimethylbenz(a)anthracene (DMBA)--7-hydromethyl-12-methylbenz(a)anthracene and 7,12-dihydroxymethylbenz(a)anthracene--on the dynamics of DMBA fluorescence was studied in the skin of mice. The first of the metabolites did not affect the dynamics of DMBA fluorescence, whereas the second one, when used in equimolar concentrations with DMBA, prolonged the duration of DMBA fluorescence in the skin. The same effect was observed in case of 7,8-benzoflavone, and inhibitor of DMBA metabolism.

[The effect of hydroxymethyl derivatives of 7,12-dimethylbenz(a)anthracene on its metabolism and toxic action in tissue culture]. / Vliianie oksimetil'nykh proizvodnykh 7,12-dimetilbenz(a)antratsena i ego metabolizm i toksicheskoe deistvie v kul'ture tkani

The naturally occurring hydroxymethyl derivatives of the carcinogen 7,12-dimethylbenz(a)anthracene was found to inhibit the metabolic hydroxylation and toxic effect of this carcinogen in mouse embryo fibroblast-like cell culture. The greatest reduction of both effects was obtained when 12-hydroxymethyl-7-methylbenz(a)anthracene was added to the growth medium, less effective were, resp., 7,12-dihydroxymethylbenz(a)-anthracene and 7-hydroxymethyl-12-methylbenz(a)anthracene. The data obtained are discussed in terms of the intracellular regulation of carcinogenic hydrocarbon metabolism.