New lead compounds for brassinosteroid biosynthesis inhibitors

The first brassinosteroid biosynthesis inhibitor is reported. Among newly synthesized triazole derivatives, 4-(4-chlorophenyl)-2-phenyl-3-(1,2,4-triazoyl)butan-2-ol (6) was found to inhibit the growth of cress seedlings, and this inhibition was recovered by the treatment of brassinolide, suggesting that compound 6 primarily inhibits brassinosteroid biosynthesis.     

New steroids with antiprogestational and antiglucocorticoid activities

A number of 11-substituted 19-norsteroids with inverse configuration at C-13 were synthesized. 11 beta-Aryl compounds in this series were found to possess antiprogestational and antiglucocorticoid activities.     

Molecular targets in the search for endothelium-protecting compounds

Impairment of endothelial function forms basis for many cardiovascular diseases, therefore today it becomes an independent target for therapeutic action, and the search for new compounds possessing endothelium-protective properties is one of the prospective goals of the pharmacotherapy and medicinal chemistry. An efficient instrument to solve the problem is the use of methods of molecular modeling. Application of the methods is possible only if detailed information on three-dimensional structure and function of molecular targets—receptors and enzymes responsible for signal transduction both inside and outside endothelial cells—is available. In the review we collected the data on the structure and functions of various macromolecules involved in the process of regulation of vascular tone. The structure of endothelial NO-synthase (EC 1.14.13.39) (eNOS) responsible for synthesis of nitrogen oxide and involved in the process of vascular tone regulation is described. The importance of its substrate, L-arginine, from the point of view of eNOS activity regulation is emphasized; the data on structure and functions of L-arginine transport system are presented. Also, various pathways of eNOS activity regulation are described, including activation and competitive inhibition through binding of exogenous substances in its active center and inhibition through caveolin binding at eNOS oxygenase domain among them, as well as regulation by means of phosphorylation of individual eNOS amino acid residues by protein kinases and their dephosphorylation by phosphatases. The importance of membrane receptors of endotheliocytes as targets for substances possessing endothelium-protective activity is emphasized. Receptors of endothelin, thrombocyte activation factor, prostaglandins, bradykinin, histamine, serotonin, and protein kinase-activated receptors are among them. The importance of calcium and potassium ion channels in vessel cells for endothelium protection is emphasized. Finally, the macromolecules discussed in the review are considered as targets in the search for endothelium-protective therapeutic agents by the proposed approaches and methods of molecular modeling.     

A new approach to the search for antineoplastic compounds

The necessity of using microbial test systems with regular reproduction of associated impairments in cell differentiation and division in screening of antitumor compounds is substantiated. Conditions for induction of such impairments during secondary growth in prokaryotic and eukaryotic mycelial microorganisms were developed. The fungal culture, Fusarium bulbigenum var. blasticola, the growth of whose secondary colonies was selectively inhibited by representatives of various classes of antitumor agents such as alkylating agents, antimetabolites, antibiotics, plant preparations, etc. was isolated.     

Experimental models in the search for antigestagenic compounds with menses-inducing activity

A need for menses-inducing drugs as an additional method for the regulation of human fertility still exists. Based on the present knowledge of the regulation of early human pregnancy, potential progesteroneantagonists should induce menstruation at the time of missed menses in a fertile cycle. The experimental models in rats, rabbits and rhesus monkeys, which would allow detection of progesterone antagonists, are described. A potential progesterone antagonist is first assessed for antigestagenic activity in the rabbit. In this test, oestrogens or compounds with oestrogenic properties have antigestagenic effects. Since it is known that oestrogens even in very high doses have no menses-inducing effect in early human pregnancy, such compounds have to be recognized and excluded from further development. In rhesus monkeys, the HCG-prolonged luteal phase was selected as model situation for early pregnancy. It was shown that oestradiol, norethisterone and lynestrenol, compounds which have antigestagenic activity in the rabbit due to their oestrogenic properties, do not induce drug-related menstruation. 11-Deoxycorticosterone and bromacetoxyprogesterone have antigestagenic activity in the rabbit which may be due to competitive progesterone antagonism; these compounds would, however, have too many side effects and are not pursued. No compound with menses-inducing activity has so far been identified; however, the experimental procedure for the study of future active compounds has been well defined.     

Signature movements lead to efficient search for threatening actions

The ability to find and evade fighting persons in a crowd is potentially life-saving. To investigate how the visual system processes threatening actions, we employed a visual search paradigm with threatening boxer targets among emotionally-neutral walker distractors, and vice versa. We found that a boxer popped out for both intact and scrambled actions, whereas walkers did not. A reverse correlation analysis revealed that observers' responses clustered around the time of the "punch", a signature movement of boxing actions, but not around specific movements of the walker. These findings support the existence of a detector for signature movements in action perception. This detector helps in rapidly detecting aggressive behavior in a crowd, potentially through an expedited (sub)cortical threat-detection mechanism.     

New search for pectolytic yeasts

A new screening method for pectin-depolymerizing microorganisms is described. The method is based on precipitation of non-hydrolyzed citrus pectin with hexadecyltrimethylammonium bromide in a medium solidified with a bacterial gelling gum. A substrate depolymerized by the secreted enzymes does not precipitate, and the positive strains thus show transparent areas around the colonies. The method was used to screen 300 yeast and yeast-like microorganisms belonging to 52 different genera. The secretion of pectin-depolymerizing enzymes occured with different frequencies in 13 genera (69 positive strains of 207 tested), the lowest frequency being found in the genusCandida (13 positive out of 125 strains tested) and the highest frequency in the generaAureobasidium (4 of 6)Cryptococcus (29 of 38),Geotrichum (4 of 9),Kluyveromyces (5 of 5),Rhodosporidium (2 of 2),Leucosporidium (2 of 2),Trichosporon (3 of 6) andUstilago (2 of 2). Strains giving the highest number of harvested cells after growth on pectin in a liquid medium have been identified. Supported by theGrant Agency for Science of the Slovak Republic.     

Advances and challenges in the search for D2 and D3 dopamine receptor-selective compounds

Compounds that target D2-like dopamine receptors (DRs) are currently used as therapeutics for several neuropsychiatric disorders including schizophrenia (antagonists) and Parkinson's disease (agonists). However, as the D₂R and D₃R subtypes are highly homologous, creating compounds with sufficient subtype-selectivity as well as drug-like properties for therapeutic use has proved challenging. This review summarizes the progress that has been made in developing D₂R- or D₃R-selective antagonists and agonists, and also describes the experimental conditions that need to be considered when determining the selectivity of a given compound, as apparent selectivity can vary widely depending on assay conditions. Future advances in this field may take advantage of currently available structural data to target alternative secondary binding sites through creating bivalent or bitopic chemical structures. Alternatively, the use of high-throughput screening techniques to identify novel scaffolds that might bind to the D₂R or D₃R in areas other than the highly conserved orthosteric site, such as allosteric sites, followed by iterative medicinal chemistry will likely lead to exceptionally selective compounds in the future. More selective compounds will provide a better understanding of the normal and pathological functioning of each receptor subtype, as well as offer the potential for improved therapeutics.     

Luteolytic effect of the antiprogestin and antiglucocorticoid agent RU486 in rats

Ovarian cells of pregnant rats were cultured with synthetic progestins (R5020, R2323), dexamethasone and RU486. Progesterone and 20 alpha-hydroxy-pregn-4-en-3-one (20 alpha-dihydroprogesterone) in the medium were measured by specific radioimmunoassay. Both R5020 and R2323 increased concentrations of these intrinsic progestins. RU486 decreased concentrations of progesterone, however, the addition of R5020 or R2323 counteracted this action. Immature hypophysectomized rats treated with pregnant mare serum gonadotropin (PMS) and human chorionic gonadotropin (hCG) were administered with RU486; the serum levels of progesterone and 20 alpha-dihydroprogesterone tended to decrease. R5020 and R2323 inhibited the effect of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), whereas RU486 did not. Inhibition of the cholesterol side chain cleavage enzyme (CSCC) by RU486 was more marked than that by R5020 or R2323. These results show that RU486 decreases progesterone synthesis in cultured ovarian cells. A part of the mechanism may involve an inhibition of CSCC.     

Mathematical model for microbial oxidation of pure lead sulfide by Thiobacillus ferrooxidans

A shrinking-core mathematical model describing bioleaching of lead sulfide is developed considering the deposition of insoluble bio-oxidation products on metal sulfide particle surfaces. Variations in particle size are considered as it affects diffusion limitations.     

Teratogenic effects of lead in the mouse

Female mice of the C57B1 strain were mated and given from the first day of the pregnancy a normal diet, containing 1.1% of calcium, or a calcium-deficient one, containing 0.2% of calcium. Animals of the 2 groups were injected intra-peritoneally with 15 or 35 mg of lead acetate/kg at different times of the fetal organogenesis (8th, 9th, 10th or 12th day of the pregnancy). In the normal diet group, injection of lead increases the postimplantation mortality and the rate of skeletal anomalies among the fetuses. The anomalies are restricted to the anterior part of the axial skeleton and consist essentially in the fusion of 2 or more cervical vertebrae. In addition, lead diminishes the blood calcium levels in the pregnant females. In the calcium deficient group, all these effects of lead are considerably increased and fetuses suffer a loss of weight and delayed ossification. In the animals given such a diet but non lead-injected, the fetal weight is already diminished. However, the ossification and the rate of skeletal anomalies are not affected, and the blood calcium levels of the mothers are similar to those of the control females given a normal diet.     

Mutagenesis and comutagenesis by lead compounds.

We have previously reported that lead(II) is weakly mutagenic to Chinese hamster V79 cells. A transgenic cell line G12 containing a single copy of the E. coli gpt gene was developed in this laboratory from Chinese hamster V79 cells. The gpt locus in the G12 cells is more mutable by radiation and oxidative agents compared with the endogenous hprt locus of wild-type V79 cells. We have investigated the mutagenicity of two lead compounds at the gpt locus in G12 cells. Only at a toxic dose is lead acetate significantly mutagenic to G12 cells. Lead nitrate is not significantly mutagenic at any dose. Although both compounds are water-soluble, lead acetate, but not lead nitrate, forms a fine white insoluble precipitate upon addition to growth medium. A nick translation assay on cells treated with lead compounds and then permeabilized indicated that lead nitrate and, to a greater extent, lead acetate causes the appearance of nicks in chromosomal DNA. Lead ions in the presence of hydrogen peroxide, but not alone, introduced nicks into supercoiled plasmid DNA in vitro, suggesting that lead ions can partake in a Fenton reaction and thereby damage DNA. At lower nonmutagenic concentrations, lead acetate enhances the mutagenicity of MNNG and ultraviolet light. DNA damage by ultraviolet light is not enhanced by lead ions in vitro. Our data support the concept that non-toxic concentrations of lead(II) can inhibit DNA repair. Thus, at biologically relevant doses, lead(II) could act as a comutagen and possibly a cocarcinogen, but is not likely to act as an initiating genotoxic carcinogen.