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.     

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.     

RNA and DNA synthesis catalyzed by a DNA-polymerase alpha complex with primase from silkworm cells on single-stranded DNA]

Depending on the ionic environment the replicative complex of silkworm Bombyx mori, containing DNA polymerase alpha and primase, catalyzes on single-stranded DNA of phage M13 a NTP-dependent synthesis or elongation of preformed primers. In the presence of NTPs and dNTPs at conditions optimal for the NTP-dependent synthesis the replicative complex synthesizes on M13 DNA oligoribonucleotides of 9-11 residues, which serve as primers for polymerization of DNA. The length of RNA-primers synthesized by primase of the complex depends on concentration of dNTP but does not depend on activity of DNA polymerase alpha. During elongation of exogenic primers annealed to M13 DNA the complex is processive synthesizing DNA fragments of dozens residues without dissociation from the template. Double-stranded structures in DNA such as "hairpins" appear to be barriers for driving of the complex along the template and cause pauses in elongation. DNA-binding proteins the SSB of Escherichia coli or the p32 of phage T4 destabilize double-stranded regions in DNA and eliminate elongation pauses corresponding to these regions. The replicative complex is able to fill in single-stranded gaps in DNA completely and to perform slowly the synthesis with displacement of one of parent strands in duplexes via repeated cycles of binding to the primer-template, limited elongation and dissociation.     

Binding of SSB-protein from Ehrlich ascites carcinoma cells with DNA and polyribonucleotides]

Binding of SSB-protein from Ehrlich ascites tumor to ssDNA from M13 phage leads to its compactization. The structure of the complex at the protein/DNA ratios far from the saturation level looks like "beads-on the string". DNA that was fully saturated with protein forms collapsed globular structure. Binding of the protein to the dsDNA from phage lambda increases its flexibility and decreases the coil dimensions; no "beads-on the string" structure are seen. The protein possess slight destabilizing effect on hairpin helices of M13DNA. Competition studies demonstrate that the binding properties of protein with polyribonucleotide lattices and DNA's decrease in ranking as follows: poly(rG) greater than or equal to poly(rI) greater than or equal to ssDNA greater than dsDNA greater than poly(rA) congruent to approximately poly(rU). Thus SSB-protein from Ehrlich ascites tumor differs significantly from its presumed prokaryotic analogs.     

Induction of transverse polarity by blue light: An all-or-none response

Phototropic stimulation induces a spatial memory. This was inferred from experiments with maize (Zea mays L.) coleoptiles involving opposing blue-light pulses, separated by variable time intervals, and rotation on a horizontal clinostat (Nick and Schafer, 1988b, Planta 175, 380-388). In those experiments, individual seedlings either curved towards the first or towards the second pulse, or they remained straight. Bending, if it occurred, seemed to be an all-or-none response. Intermediates, i.e. plants, bending only weakly, were not observed. In the first part of the present study it was attempted to create such intermediates. For this purpose the strength of the first, inducing, and the second, opposing, pulse was varied. The result was complex: (i) Individual seedlings maintained the all-or-none expression of spatial memory. (ii) However, on the level of the whole population, the time intervals at which a given response type dominated depended on the fluence ratio. (iii) Furthermore, the final curvature was determined by the fluence ratio. These results are discussed in terms of a blue-light-induced transverse polarity. This polarity initiates from a labile precursor, which can be reoriented by an opposing stimulation (indicated by the strong bending towards the second pulse). The strong curvatures towards the first pulse over long time intervals reveal that, eventually, the blue-light-induced transverse polarity becomes stabilised and thus immune to the counterpulse. In the second part of the study, the relation between phototropic transduction and transverse polarity was characterised by a phenomenological approach involving the following points: (i) Sensory adaptation for induction of transverse polarity disappears with a time course similar to that for phototropic sensory adaptatation. (ii) The fluence response for induction of transverse polarity is a saturation curve and not bell-shaped like the curve for phototropism (iii) For strong counterpulses and long time intervals the clinostat-elicited nastic response (Nick and Schafer 1989, Planta 179, 123-131) becomes manifest and causes an "aiming error" towards the caryopsis. (iv) Temperature-sensitivity of polarity induction was high in the first 20 min after induction, then dropped sharply and rose again with the approach of polarity fixation. (v) Stimulus-summation experiments indicated that, for different inducing fluences, the actual fixation of polarity happened at about 2 h after induction. These experiments point towards an early separation of the transduction chains mediating phototropism and transverse polarity, possibly before phototrophic asymmetry is formed.     

Methyljasmonate and α-linolenic acid are potent inducers of tendril coiling

A coiling-inducing factor was isolated from tendrils of Bryonia dioica Jacq. and identified by infrared, ¹H-, ¹³C-nuclear magnetic resonance and mass spectrometry as -linolenic acid. When applied to detached tendrils, exogenous -linolenic acid, but not linoleic acid or oleic acid, induced tendril coiling. Further investigations showed that metabolites of -linolenic acid, jasmonic acid and, even more so, methyljasmonate, are highly effective inducers of tendril coiling in B. dioica. Methyljasmonate was most active when administered by air and, in atmospheric concentrations as low as 40–80 nM, induced a full free-coiling response with kinetics similar to mechanical stimulation. Even atmospheric levels as low as 4–5 nM methyljasmonate were still found to be significantly active. Methyljasmonate could be one of the endogenous chemical signals produced in mechanically stimulated parts of a tendril and, being highly volatile, act as a diffusible gaseous mediator spreading through the intracellular spaces to trigger free coiling of tendrils.Abbreviations EI-MS electron impact-mass spectrometry - HPLC high-performance liquid chromatography - IAA indole-3-acetic acid - NMR nuclear magnetic resonance - TFA trifluoroacetic acid We are indebted to the Deutsche Forschungsgemeinschaft, Bonn and the Fonds der Chemischen Industrie, Frankfurt (literature provision) for their support and to Dr. C. Brückner, Halle, for jasmonic-acid determinations.