Influence of plant extracts on the metabolic activity of the yeast Saccharomyces cerevisiae 39]

Addition to the nutrient medium of the extracts of camomile, nettle, mint, or Saint-John's-wort to a concentration of 0.5-4% was established to activate the yeast growth. The maximum effect was recorded on the addition of the extracts to the poor "water" medium. The extracts of camomile and Saint-John's-wort were shown to inhibit the alcohol dehydrogenase activity of the yeast cells, whereas the extracts of nettle and mint increased the activity of this enzyme by 62-70%.     

Interaction of a cysteine-containing peptide with DNA

Cystine peptide dimer (Lys-Gly-Val-Cys-Val-N2H2Dns)2 with S-S bridge was synthesized and its interactions with DNA and synthetic polynucleotides have been studied by optical spectroscopy methods. By recording fluorescent titration curves we have shown that the affinity of the peptide to different synthetic polynucleotides decreases in the order: poly(dG).poly(dC) greater than poly(dA).poly(dT) greater than poly(dGC).poly(dGC). The stability of complexes to increasing concentrations of NaCl diminishes in the same order. The association constant is about 20-fold greater for peptide binding to poly(dG).poly(dC) than to poly(dA).poly(dT). By using circular dichroism and fluorescence measurements we have shown that the peptide competes for the binding sites on DNA with two minor-groove binding antibiotics--distamycin A and sybiromycin. These results have suggested that the peptide also binds in the DNA minor groove. Investigation of the interactions between such peptides and DNA may be useful for constructing ligands with combined specificity to DNA.     

A universal instinct for designing thermoregulated promotors in gram-positive bacteria]

The construction of plasmid pVKH300, which is useful for modifying any promoter into the thermoregulated form in B. subtilis cells, is presented. The main features of the plasmid are the presence of effectively expressed in B. subtilis lambda C1857 gene and recognition site of BglII restriction enzyme between OR2 and OR3 lambda phage operator sites. Promoterless alpha-amylase gene of B. amyloliquefaciens is used as a reporter gene for promoter cloning into BglII site of pVKH300. Examples of promoter-containing DNA fragments cloning with pVKH300 as vector are presented. It was found that the best regulated promoter, in a plasmid named pVKH332, was cloned in such a way that the distance between central nucleotides of OR2 and OR3 is equal to integer number of DNA helix turns (84 b.p. in the case).     

Pea (Pisum sativum) genes participating in symbiosis with nitrogen-fixing bacteria. II. Nucleotide sequence of cDNA and parts of the late nodulin-6 (PsNod6) gene]

Certain characteristics of late noduline gene from pea-Nod6 were investigated as part of works of characterization of higher plant genes taking part in symbiotic nitrogen fixation. The complete 450 b.p. long cDNA was sequenced, it's coding sequence includes the open reading frame. The part of DNA containing the corresponding gene from the genomic clone was also sequenced. The predicted Nod6 amino acid sequence has been analyzed and do not reveal the significant homology with any known protein.     

Interaction of trivaline with single-stranded polyribonucleotides]

Binding of tripeptide H-Val3-(NH)2-Dns (TVP) to polyribonucleotides was studied by fluorescence methods, circular and flow linear dichroism, equilibrium dialysis and electron microscopy. It was found that TVP binds to poly(U) in monomer, dimer and tetramer forms with binding constants of about 10(3), 40, 18.10(4) M, respectively. The cooperativity parameter for peptide dimer binding is 2000. The peptide forms tetramer complexes with poly(A), poly(C), poly(G) also. The formation of a complex between the peptide tetramer and nucleic acid is accompanied by a significant increase in the fluorescence intensity. The cooperative binding of TVP dimers to poly(U), poly(A), poly(C) is accompanied by a dramatic decrease in the flexibility of polynucleotide chains. However, it has a small effect (if any) on the flexibility of the poly(G) chain. The observed similarity of thermodynamic, optical and hydrodynamic++ properties of TVP complexes with single-stranded and double-stranded nucleic acids may reflect a similarity in the geometries of peptide complexes with nucleic acids. Electron microscopy studies show that peptide binding to poly(U) and dsDNA leads to compactization of the nucleic acids caused by interaction between the peptide tetramers bound to a nucleic acid. At the first stage of the compactization process the well-organized rod-like particles are formed, each consisting of one or more single-stranded polynucleotide fibers. Increasing the peptide concentration stimulates a side-by-side association and folding of the rods with the formation of macromolecular "leech-like" structures with the thickness of 20-50 nm.     

Testicular toxicity and mutagenicity of steroidal and non-steroidal estrogens in the male mouse.

The mutagenicity and toxicity of diethylstilbestrol (DES), 17 beta-estradiol and zeranol on the male mouse germ cells were investigated with meiotic micronucleus assays in vivo and in vitro, sperm-head abnormality test and morphometry. Further, the developmental effects of DES on testicular morphology were explored. Micronucleus induction was observed at 10(-7) M concentration of DES and 17 beta-estradiol in vitro, but other treatments yielded negative results. The micronucleus assay in vivo revealed a small number of micronuclei in early haploid spermatids 17 days after a single subcutaneous injection of DES 50 mg/kg, whereas estradiol and zeranol gave negative results. The sperm-head abnormality rates were significantly elevated 5 weeks after treatments with high doses of DES, 17 beta-estradiol and zeranol, and testicular morphometry revealed transient changes in the volume densities of testicular tissue components. Prenatal and neonatal estrogen administration resulted in permanent alterations in seminiferous epithelium and dilatation of the rete testis, but did not affect micronucleus or sperm-head abnormality rates. The mutagenicity and toxicity of hormones in the mouse testis paralleled the hormonal activity of these compounds. Early estrogenization was the most sensitive toxicity test, followed by in vitro meiotic micronucleus induction, whereas the sperm-head abnormality assay and morphological analysis did not reveal subtle changes.     

Organotin compounds induce aneuploidy in human peripheral lymphocytes in vitro

In vitro exposure of PHA-stimulated human lymphocytes to organotin compounds resulted in statistically significant increases in the frequencies of hyperdiploid cells. When taken together with our previous study demonstrating spindle inhibiting effects of the same organotin compounds by an indirect method (Jensen et al., 1989), the present study strongly indicates that organotin compounds are able to induce aneuploidy, probably by affecting spindle function.     

Antimutagenic and antitumorigenic activities of nordihydroguaiaretic acid.

Nordihydroguaiaretic acid (NDGA), which occurs in the resinous exudates of many plants is used as an antioxidant in fats and oils. In this study we show that NDGA inhibited the mutagenicity of methyl methanesulfonate, benzo[a]pyrene (BP), 2-aminofluorene, and aflatoxin B1 in Salmonella typhimurium strain TA100 or TA98 in the absence and presence of rat hepatic microsomal activation system. The addition of NDGA during and after nitrosation of methylurea (MU) resulted in a dose-dependent inhibition of mutagenicity induced by nitrosation products of MU. In a two-stage skin tumorigenesis protocol using 7,12-dimethylbenz[a]anthracene (DMBA) as the initiating agent followed by twice weekly applications of 12-O-tetradecanoylphorbol-13-acetate (TPA) as tumor promoter, pretreatment of animals with NDGA prior to DMBA application, afforded significant protection against skin tumorigenicity in female SENCAR mice. In additional studies, skin application of NDGA also inhibited the binding of topically applied [3H]BP and [3H]DMBA to epidermal DNA. When assessed in the anti-tumor promotion protocol, pretreatment of animals with NDGA before each application of TPA in DMBA-initiated mouse skin, resulted in 72% decrease in the total number of tumors when compared to non-NDGA pretreated animals. The possible mechanism(s) of the antimutagenic and anti-tumorigenic activities may be due to the multiple effects of NDGA as inhibitor of the carcinogen metabolism and DNA-adduct formation, scavenger of carcinogen free radicals, and as inhibitor of TPA-induced ornithine decarboxylase activity.     

Fractionation of eukaryotic DNA in a pulsating electrical field. I. Detection and properties of discrete DNA fragments]

The fractionation of eukaryotic DNA by field inversion gel electrophoresis results in the appearance of discrete DNA-fragments. The set of these fragments is similar to that of different eukaryotic representatives and consists of various chromosomal DNAs, unified by size. The physical properties of DNA-fragments suggest that they can form multimeric structures due to the presence of sticky ends flanking discrete fragments. We suppose that the set of discrete DNA-fragments results in a specific cleavage of intact nuclear DNA and can reflect different levels of chromatin structural organization.     

Immunological identification of yeast SCO1 protein as a component of the inner mitochondrial membrane

Summary The SCO1 gene of Saccharomyces cerevisiae encodes a 30 kDa protein which is specifically required for a post-translational step in the accumulation of subunits 1 and 2 of cytochrome c oxidase (COXI and COXII). Antibodies directed against a -Gal::SCO1 fusion protein detect SCO1 in the mitochondrial fraction of yeast cells. The SCO1 protein is an integral membrane protein as shown by its resistance to alkaline extraction and by its solubilization properties upon treatment with detergents. Based on the results obtained by isopycnic sucrose gradient centrifugation and by digitonin treatment of mitochondria, SCO1 is a component of the inner mitochondrial membrane. Membrane localization is mediated by a stretch of 17 hydrophobic amino acids in the amino-terminal region of the protein. A truncated SCO1 derivative lacking this segment, is no longer bound to the membrane and simultaneously loses its biological function. The observation that membrane localization of SCO1 is affected in mitochondria of a rho ⁰ strain, hints at the possible involvement of mitochondrially coded components in ensuring proper membrane insertion.