Mapping the Hawaiian plume conduit with converted seismic waves

The volcanic edifice of the Hawaiian islands and seamounts, as well as the surrounding area of shallow sea floor known as the Hawaiian swell, are believed to result from the passage of the oceanic lithosphere over a mantle hotspot. Although geochemical and gravity observations indicate the existence of a mantle thermal plume beneath Hawaii, no direct seismic evidence for such a plume in the upper mantle has yet been found. Here we present an analysis of compressional-to-shear (P-to-S) converted seismic phases, recorded on seismograph stations on the Hawaiian islands, that indicate a zone of very low shear-wave velocity (< 4 km s(-1)) starting at 130-140 km depth beneath the central part of the island of Hawaii and extending deeper into the upper mantle. We also find that the upper-mantle transition zone (410-660 km depth) appears to be thinned by up to 40-50 km to the south-southwest of the island of Hawaii. We interpret these observations as localized effects of the Hawaiian plume conduit in the asthenosphere and mantle transition zone with excess temperature of approximately 300 degrees C. Large variations in the transition-zone thickness suggest a lower-mantle origin of the Hawaiian plume similar to the Iceland plume, but our results indicate a 100 degrees C higher temperature for the Hawaiian plume.     

Kinetics of BRCA1 regulation in response to UVC radiation

To investigate changes in BRCA1 following DNA damage, we exposed MCF-7 cells to increasing doses of ultraviolet C. We observed an increase in BRCA1 protein levels above 78 J/m². This increase was observed as early as 5 min after irradiation. BRCA1 levels were then observed to decrease after 2 h, consistent with the previously published data. By pretreating with cycloheximide prior to irradiation, we observed a decrease in the protein half-life, from 3.5 h to 53 min, suggesting that a decrease in protein half-life may cause the lower levels of BRCA1 after irradiation. We also observed an increase in BRCA1 mRNA within 15 min of irradiation, followed by a decrease after 4 h. These data suggest that newly translated protein may contribute to increases in BRCA1 protein levels. The very rapid changes in BRCA1 support its role as a sensor of DNA damage, as opposed to being a repair gene. Received 6 April 2000; received after revision 23 May 2000; accepted 23 May 2000     

X-irradiation of mice in early fetal period influences dose-dependently sex ratio of offspring until weaning

Summary Fractionated X-irradiation of mouse fetuses on gestation days 11–13 resulted in a significantly increased postnatal mortality of female litters. This occurred only at 3×110 rad, which was the threshold for the formation of typical neuroepithelial, rosette-like malformations.We are greatly indebted for the technical assistance of Miss C. Gutmann, Mrs I. Hempfling and Mrs K. Pfaff.     

Acetylcholine as an activator of oxidation reactions

Zusammenfassung Acetylcholin wirkt als Aktivator auf Oxydationsreaktionen mit Wasserstoffperoxyd in alkalischer Lösung. Solche Wirkungen auf die Chemilumineszenz des Luminols (3-Aminophthalhydrazid), auf die Oxydation des Indols, Benzidins und o-Dianizidins wurden durch Messungen der Lumineszenzintensität (), bzw, der Extinktion (E) näher untersucht.     

Über die Ausschleusung nukleolärer Substanz im Milchdrüsenepithel der weissen Maus

Summary Mammary glands of the white mouse in different stages of lactation were fixed in Carnoy's fluid and the sections stained with Gallocyanin-chromalum für microscopic observation. After dislocation of the nucleolus to the nuclear membrane or the formation of a heterochromatic pathway between nucleolus and nuclear membrane the extrusion of nucleolar substance into the cytoplasm was observed.     

Histochemical localization of acid phosphatase and cathepsin-like activities in regressing tails of xenopus larvae at metamorphosis

Zusammenfassung Histochemische Reaktionen an regredierenden Schwänzen von Krallenfroschlarven haben ergeben, dass die saure Phosphatase und die kathepsinartigen Esterasen vorwiegend in Makrophagen des subepidermalen Bindegewebes angereichert sind. Somit dürfte die erhöhte Aktivität dieser Fermente im regredierenden Schwanzgewebe auf der lokalen Aktivierung von Makrophagen beruhen.

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This work was supported by the Swiss National Foundation for Promotion of Scientific Research (Project 1613).