Indian Hedgehog is an antagonist of Wnt signaling in colonic epithelial cell differentiation

Wnt signaling defines the colonic epithelial progenitor cell phenotype, and mutations in the gene adenomatous polyposis coli (APC) that activate the Wnt pathway cause the familial adenomatous polyposis coli (FAP) syndrome and most sporadic colon cancers. The mechanisms that regulate the transition of epithelial precursor cells into their differentiated derivatives are poorly characterized. We report that Indian hedgehog (Ihh) is expressed by mature colonocytes and regulates their differentiation in vitro and in vivo. Hedgehog (Hh) signaling restricts the expression of Wnt targets to the base of the colonic crypt in vivo, and transfection of Ihh into colon cancer cells leads to a downregulation of both components of the nuclear TCF4-beta-catenin complex and abrogates endogenous Wnt signaling in vitro. In turn, expression of Ihh is downregulated in polyps of individuals with FAP and expression of doxycycline-inducible dominant negative TCF4 (dnTCF4) restores Ihh expression in APC mutant DLD-1 colon cancer cells. These data identify a new Wnt-Hh axis in colonic epithelial renewal.     

Hexalure,an insect sex attractant discovered by empirical screening

Zusammenfassung Empirisch wurde ein Sexuallockstoff — cis-7-Hexadecen-1-ol-acetat-gefunden, der auf Männchen der roten Baumwollkapselmotte,Pectinophora, gossypiella (Saunders), auffallend stark wirkt.     

Studies on chemotaxis. VII. Cytotaxins in rabbit serum

Zusammenfassung Die Untersuchungen zeigen, dass mehrere Zytotaxine im Kaninchenserum vorhanden sein können. Zwei davon wirken spezifisch auf Granulozyten und ein anderes spezifisch auf mononukleare Zellen.     

Depletion of cerebral monoamines byp-chlorophenylalanine in the cat

Zusammenfassung p-Chlorphenylalanin, ein Inhibitor der Serotoninbiosynthese, senkte bei Katzen den Serotoningehalt des Gehirns nicht selektiv. Es wurde gleichzeitig eine signifikante und langanhaltende Erniedrigung des Noradrenalin- und Dopamingehalts gefunden.     

Selective incorporation of zinc into rat mast cells

Zusammenfassung Bei der Albinoratte findet sich 48 h nach parenteraler Verabreichung von radioaktivem Zink (Zn⁶⁵) ein hoher Anteil der Aktivität in den Gewebemastzellen. Nach Verabreichung des chemischen Histaminliberators, Compound 48/80, wird ein erheblicher Teil von Zn⁶⁵ aus den Zellen frei.

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This work was supported by the Schweizerische Nationalfonds zur Förderung der wissenschaftlichen Forschung (Grant No. 5200.3).     

Clonal reproduction by males and females in the little fire ant

Sexual reproduction can lead to major conflicts between sexes and within genomes. Here we report an extreme case of such conflicts in the little fire ant Wasmannia auropunctata. We found that sterile workers are produced by normal sexual reproduction, whereas daughter queens are invariably clonally produced. Because males usually develop from unfertilized maternal eggs in ants and other haplodiploid species, they normally achieve direct fitness only through diploid female offspring. Hence, although the clonal production of queens increases the queen's relatedness to reproductive daughters, it potentially reduces male reproductive success to zero. In an apparent response to this conflict between sexes, genetic analyses reveal that males reproduce clonally, most likely by eliminating the maternal half of the genome in diploid eggs. As a result, all sons have nuclear genomes identical to those of their father. The obligate clonal production of males and queens from individuals of the same sex effectively results in a complete separation of the male and female gene pools. These findings show that the haplodiploid sex-determination system provides grounds for the evolution of extraordinary genetic systems and new types of sexual conflict.     

Rain, winds and haze during the Huygens probe's descent to Titan's surface

The irreversible conversion of methane into higher hydrocarbons in Titan's stratosphere implies a surface or subsurface methane reservoir. Recent measurements from the cameras aboard the Cassini orbiter fail to see a global reservoir, but the methane and smog in Titan's atmosphere impedes the search for hydrocarbons on the surface. Here we report spectra and high-resolution images obtained by the Huygens Probe Descent Imager/Spectral Radiometer instrument in Titan's atmosphere. Although these images do not show liquid hydrocarbon pools on the surface, they do reveal the traces of once flowing liquid. Surprisingly like Earth, the brighter highland regions show complex systems draining into flat, dark lowlands. Images taken after landing are of a dry riverbed. The infrared reflectance spectrum measured for the surface is unlike any other in the Solar System; there is a red slope in the optical range that is consistent with an organic material such as tholins, and absorption from water ice is seen. However, a blue slope in the near-infrared suggests another, unknown constituent. The number density of haze particles increases by a factor of just a few from an altitude of 150 km to the surface, with no clear space below the tropopause. The methane relative humidity near the surface is 50 per cent.