External zinc stimulates proliferation of tumor Hep-2 cells by active modulation of key signaling pathways.

The effect of external zinc supplementation (10 and 35 micromol) on cell proliferation and mitogenic signaling of Hep-2 tumor cells was examined during 72 h of treatment. Zinc levels were manipulated by using zinc-free cultivation medium with or without addition of zinc ions. Proliferation of Hep-2 cells exposed to zinc-free medium decreased in a time-dependent manner and corresponded to decreasing intracellular zinc content. Hep-2 cells accumulated in G(0)/G(1) phase, showed reduced abundance of AKT and NF-kappaB as well as of anti-apoptotic Bcl-2 and Bcl-XL proteins. Zinc supplied to Hep-2 cells maintained in the presence of zinc-free medium stimulated their proliferation as well as mitogenic signaling which paralleled increasing intracellular zinc content. In zinc-exposed Hep-2 cells, several changes in various mitogenic signaling pathways were noted such as enhanced expression of p53, AKT and MAP kinases, NF-kappaB and increased DNA binding of AP-1 family. Also, supplementation with zinc of Hep-2 cells resulted in the suppression of key apoptotic molecules such as Bax protein and increased expression of anti-apoptotic Bcl-2 and Bcl-XL proteins. Since only the highest supplied zinc concentration (35 micromol) induced oxidative stress, it is reasoned that the observed activation of pro-survival signaling occurs both directly and indirectly. These data show that zinc may stimulate growth and proliferation of some tumor cells by a combination of internal mechanisms with a varying contribution of external signaling pathways too.     

Über die gestaltende Wirkung verschiedener Ernährung auf die Organe der Gans,insbesondere über die funktionelle Anpassung an die Nahrung

Ohne Zusammenfassung     

Seasonality of harpacticoids (Crustacea, Copepoda) in a tidal pool in subarctic south-western Iceland

Seasonality of phytal harpacticoids was studied in a tidal pool in the lower rocky intertidal in south-western Iceland. Samples of the red alga Chondrus crispus were taken monthly from January 1999 to January 2000. Multidimensional scaling ordination showed a clear seasonal pattern in phytal species composition and abundance of individual species. Of more than 70 species recorded, Zaus spinatus accounted for one third of the total abundance. Many species were found only sporadically and analysis of the data was confined primarily to the eleven most common species (Zaus spinatus, Ectinosomaspp., Tisbespp., Ameira longipes, Mesochra sp. 2 and Mesochrasp. 1, Dactylopusia vulgaris, Amphiascoides debilis, Amphiascussp. 1, Parastenhelia spinosa and Amphiascus minutus). Four showed no significant variation in total abundance through the year, while the remainder had more or less pronounced peaks in summer. Most species (on which data was sufficient) had a prolonged (≥ 6 months) to a continuous breeding season, as indicated by the presence of ovigerous females. This contrasts with most shallow-water temperate and subarctic invertebrates which appear to have more restricted breeding seasons. Our results extend to higher latitudes the general conclusion that many temperate phytal harpacticoids have a long, often continuous, breeding season. The reasons for this are unclear but, presumably, involve access to continuous food supply. There is strong evidence that variations in abundance of several species in the tidal pool were not due only to recruitment, but also to migration to the pool in summer and emigration in autumn.     

Untersuchungen über die Bastardierung der Echiniden- und Crinoidenfamilie

Ohne ZusammenfassungVorgetragen in der Sitzung der Akad. d. Wissenschaften in Krakau am 10. Juli 1905. Vorl. Mitteil. in Bull. de l'Acad. des Sc. de Cracovie. Juillet 1905.     

Die Einwirkung des Sauerstoffes auf die Entwickelung von Rana temporaria und Versuch der quantitativen Bestimmung des Gaswechsels in den ersten Entwickelungsstadien

Ohne Zusammenfassung     

Interaction of nucleic acids with electrically charged surfaces: II. Conformational changes in double-helical polynucleotides

The influence of adsorption of double-stranded (ds) DNA, ds RNA and homopolymeric pairs at a mercury electrode on conformation of these polynucleotides was studied. Changes in the polarographic reducibility of polynucleotides, which were followed by means of normal pulse polarography and linear sweep peak voltammetry at the dropping mercury electrode were exploited to indicate conformational changes. It was found that, as a consequence of adsorption of ds polynucleotides on the negatively charged electrode conformational changes similar to denaturation take place in a narrow potential region around ?1.2 V (the region U). After sufficiently long time of the contact with the electrode (under our conditions about 10 s) these changes reach limiting values, which can approach total denaturation. Upon adsorption of ds polynucleotides on the electrode charged to more positive potentials than the region U either (1) no conformational changes occur or (2) only a small part of the polynucleotide (probably labile regions of the ds molecule) is very quickly denatured - the remainder of the molecule preserves its ds structure. Conformational changes of adsorbed ds polynucleotides are influenced by factors which change the stability of ds polynucleotides in solution. It is supposed that denaturation of ds polynucleotides in the region U might result from the strains connected with the repulsion of certain segments of the molecule anchored on the electrode from the negatively charged surface.     

ON THE NATURE AND ORIGIN OF THE FEATHER COLOURATION IN THE GREAT WHITE PELICAN PELECANUS ONOCROTALUS ROSEUS IN ETHIOPIA

The yellow or orange-brown colour on the breast feathers and to a lesser extent on other feathers of the Great White Pelican in a breeding colony on an island in Lake Shala, Ethiopia, is due to the presence of ferric oxide.
The feathers most probably become stained when the birds are in the water, and the source of the ferric oxide may be iron–rich silt carried into the lake by the Gidu River.