The incorporation of deoxyuridine monophosphate into DNA increases the sister-chromatid exchange yield

The effect of a treatment with 5-fluoro-2'-deoxyuridine (FdUrd) in combination with 2'-deoxyuridine (dUrd) on cell proliferation, incorporation of DNA precursors into DNA and sister-chromatid exchanges (SCEs) has been analyzed in Allium cepa meristem cells. FdUrd in the range 10(-9)-5 X 10(-7) M produced a dose- and time-dependent decrease in the amount of cells in mitosis. This inhibitory effect could be reversed by 70-80% in short-term (6 h) experiments, by exogenously supplied dUrd at a concentration of 10(-4) M. However, at the highest FdUrd dose tested (10(-7) M), 10(-4) M dUrd could not reverse the FdUrd effect in long-term experiments (20 h, about one cell cycle interval), as shown by analyzing the kinetics of synchronous cell populations. DNA extracted from cells pulsed with [6-3H]dUrd in the presence of FdUrd and 6-amino-uracil (6-AU), an inhibitor of uracil-DNA glycosylase, contained a small amount of label (at least 3% of the total radioactivity incorporated into DNA) in the form of [6-3H]dUMP. Thus, we conclude that, under our experimental conditions, exogenously supplied dUrd may be metabolized intracellularly to 2'-deoxyuridine triphosphate (dUTP) and that this deoxynucleotide may eventually be mis-incorporated into DNA. As far as the formation of SCEs is concerned, analysis of second division chromosomes showed that 2'-deoxyuridine monophosphate (dUMP) residues present in newly-synthesized DNA strands are probably not relevant to SCE formation. However, by analyzing SCE levels in third division chromosomes of cells treated with FdUrd and dUrd during their second cycle, we have scored a 6-fold increase in the reciprocal SCE level which demonstrates that the replication of a dUMP-containing DNA template leads to a higher SCE yield.     

Immediate induction of a 45 K secreted glycoprotein by serum and growth factors in quiescent mouse 3T3 cells : Two-dimensional gel analysis

Stimulation of quiescent 3T3 cells by serum dramatically induces the synthesis of a group of secreted polypeptides with a molecular weight (MW) of 45 K (p45 A, B, C, D). The synthesis of these polypeptides increases 10-fold during the first 2 h. Cycloheximide superinduces the 45 K polypeptides and actinomycin D (actD) blocks completely their induction by serum. Peptide mapping analysis and pulse-chase experiments revealed that p45 A is a precursor of polypeptides p45 B, C, D. Tunicamycin treatment inhibits the synthesis of all four polypeptides but a new related protein appears, p-p45, the unglycosylated precursor. In the presence of tunicamycin, p-p45 is also found in the medium, demonstrating that glycosylation is not essential for the secretion. In vitro translation experiments show that the levels of p45 mRNA present in stimulated cells are severalfold higher than that of non-stimulated cells. Purified growth factors, such as platelet-derived growth factor (PDGF), fibroblast growth factor (FGF) and epidermal growth factor (EGF) induce the synthesis of p45 in quiescent cells.     

Insulin and IGF receptors are developmentally regulated in the chick embryo eye lens

We have previously reported that insulin-like growth factor (IGF) receptors appear to predominate over insulin receptors in early stages of embryogenesis in the chick (days 2-3 whole embryo membranes). Overall, [125I]IGF I and II binding to specific receptors was maximal when the rate of brain growth is highest. In the present study we used the embryonic chick lens, a well-defined tissue composed of a single type of cell, to analyse whether changes of insulin and IGF I binding are correlated with changes in growth rate and differentiation state of the cells. We show that both insulin receptors and IGF receptors are present in the lens epithelial cells, and that each type is distinctly regulated throughout development. While there is a direct correlation between IGF-binding capability and growth rate of the cells, there is less relation to differentiation status and embryo age. Insulin receptors, by contrast, appear to be mostly related to the differentiated state of cells, decreasing sharply in fibers, irrespective of their developmental age.     

Zinc accumulation in the telencephalon of lizards

Summary The zinc concentration in the brains of two species of lizard was determined by atomic-absorption spectrophotometry. The zinc concentration was found to be highest in the telencephalon of Lacerta galloti (21.1 g/g fresh weight) and Podarcis hispanica (16.77±0.8 g/g) while the mesencephalon and brain stem exhibited lower zinc concentrations, i.e., 7.0 g/g in Lacerta galloti and 6.08±0.4 g/g in Podarcis hispanica. This high telencephalic concentration of zinc is paralleled by intense and well-defined Timm reactivity used for demonstrating the presence of zinc-containing boutons at the light-microscope level. Volumetricdensitometric studies of these Timm-reactive zones were performed using serial transverse sections of the same lizard brains.     

Glutathione status and sensitivity to GSH-reacting compounds of Escherichia coli strains deficient in glutathione metabolism and/or catalase activity

The intracellular concentrations of total glutathione, GSSG and protein · S-SG, the total excreted glutathione concentration, and the susceptibility towards GSH-reacting compounds were assayed in strains of Escherichia coli deficient in biosynthesis and/or reduction of glutathione. A deficiency in glutathione reductase displaced the glutathione status towards the oxidized forms. This displacement was more clearly appreciated in strains additionally deficient in glutathione biosynthesis. A deficiency in catalase activity also produced an increase in the oxidation of glutathione. The most severe changes were observed in the concentrations of protein-glutathione mixed disulfides and in the amount of glutathione excreted to the medium. Increased sensitivities towards compounds known to interact with cellular GSH were observed in glutathione reductase deficient strains, although these effects were enhanced in strains additionally deficient in GSH biosynthesis     

Search for Drosophila genes encoding a conserved domain present in the achaete-scute complex and myc proteins

Summary Several genes of the achaete-scute complex (ASC) of Drosophila melanogaster encode a 60 amino acids long conserved domain which shares a significant homology with a region of the vertebrate myc proteins. Based on these results, the existence of a family of Drosophila genes that would share both this conserved domain and the neurogenic function of the AS-C has been postulated. To test this proposal, we have searched a D. melanogaster genomic library with a probe that encodes the conserved domain. Only under very low stringency hybridization conditions, clones not belonging to the AS-C cross-hybridized with the probe. Those that gave the strongest signals were characterized. Sequencing of the cross-hybridizing regions showed that they had no significant homology with the conserved domain, the sequence similarity extending at the most for 37 nucleotides. Although our results do not conclusively disprove the existence of a family of AS-C-like genes, they indicate that the conservation of the domain would be lower than that found for shared motifs in other families of Drosophila developmental genes.     

The gene for trypsin inhibitor CMe is regulated in trans by the lys 3a locus in the endosperm of barley (Hordeum vulgare L.)

Summary A cDNA encoding trypsin inhibitor CMe from barley endosperm has been cloned and characterized. The longest open reading frame of the cloned cDNA codes for a typical signal peptide of 24 residues followed by a sequence which is identical to the known amino acid sequence of the inhibitor, except for an Ile/Leu substitution at position 59. Southern blot analysis of wheat-barley addition lines has shown that chromosome 3H of barley carries the gene for CMe. This protein is present at less than 2%–3% of the wild-type amount in the mature endosperm of the mutant Risø 1508 with respect to Bomi barley, from which it has been derived, and the corresponding steady state levels of the CMe mRNA are about I%. One or two copies of the CMe gene (synonym Itc1) per haploid genome have been estimated both in the wild type and in the mutant, and DNA restriction patterns are identical in both stocks, so neither a change in copy number nor a major rearrangement of the structural gene account for the markedly decreased expression. The mutation at the lys 3a locus in Risø 1508 has been previously mapped in chromosome 7 (synonym 5H). A single dose of the wild-type allele at this locus (Lys 3a) restores the expression of gene CMe (allele CMe-1) in chromosome 3H to normal levels.     

The breeding biology of the WheatearOenanthe oenanthe in South Sweden during three contrasting years

Summary The breeding phenology, territory size, egg dimensions, clutch size, nestling growth and reproductive success of a dense population of WheatearsOenanthe oenanthe was studied on the island of Öland, S. Sweden during the years 1985–1987. The 1987 season was exceptionally cold and rainy, 1986 had the warmest and driest conditions, while 1985 was intermediate with respect to weather. Cold, windy and rainy weather was associated to prolonged incubation, greater intervals between first and replacement clutches, prolonged nestling growth, lower fledging condition, increased starvation and increased predation. Large clutches were laid earlier in the season and contained relatively larger eggs than small clutches. Incubation periods decreased with clutch size. Female size was positively correlated with egg size and with clutch size. The last egg laid in a clutch had a tendency to be heavier than eggs laid previously, especially in large clutches. Nestling starvation increased with brood size in 2 years.

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Zusammenfassung 1985–1987 wurden Phänologie, Siedlungsdichte, Eimaße, Gelegegröße, Jungenwachstum und Bruterfolg einer Population des Steinschmätzers auf der südschwedischen Insel Öland untersucht. 1987 waren die Lufttemperaturen besonders niedrig und die Niederschläge sehr hoch. Der Sommer 1986 wies dagegen die höchsten Temperaturen und niedrigsten Niederschläge der 3 Jahre auf. Kaltes, windiges und regnerisches Wetter war mit längerer Brütezeit, längeren Intervallen zwischen Erst- und Ersatzbruten, langsamerem Jungenwachstum, schlechterer Kondition der ausfliegenden Jungen und höheren Verlusten durch Verhungern und Beutefeinde korreliert. Die Gelegegröße nahm mit dem Legedatum ab; die größten Gelege hatten im Mittel größere Eier. Die Bebrütungszeit nahm mit der Gelegegröße ab. Größere Weibchen legten größere Eier und zeigten Tendenz, größere Gelege zu produzieren. Die zuletzt gelegten Eier waren meist die schwersten, besonders in großen Gelegen. Ausfälle durch Verhungern stiegen in 2 Jahren mit der Brutgröße.