The Effect of a DNA Damaging Agent on Embryonic Cell Cycles of the Cnidarian Hydractinia echinata

The onset of gastrulation at the Mid-Blastula Transition can accompany profound changes in embryonic cell cycles including the introduction of gap phases and the transition from maternal to zygotic control. Studies in Xenopus and Drosophila embryos have also found that cell cycles respond to DNA damage differently before and after MBT (or its equivalent, MZT, in Drosophila). DNA checkpoints are absent in Xenopus cleavage cycles but are acquired during MBT. Drosophila cleavage nuclei enter an abortive mitosis in the presence of DNA damage whereas post-MZT cells delay the entry into mitosis. Despite attributes that render them workhorses of embryonic cell cycle studies, Xenopus and Drosophila are hardly representative of diverse animal forms that exist. To investigate developmental changes in DNA damage responses in a distant phylum, I studied the effect of an alkylating agent, Methyl Methanesulfonate (MMS), on embryos of Hydractinia echinata. Hydractinia embryos are found to differ from Xenopus embryos in the ability to respond to a DNA damaging agent in early cleavage but are similar to Xenopus and Drosophila embryos in acquiring stronger DNA damage responses and greater resistance to killing by MMS after the onset of gastrulation. This represents the first study of DNA damage responses in the phylum Cnidaria

Cortical thickness in youth with major depressive disorder

Article deposited according to publisher policies: http://www.biomedcentral.com/about/copyright June 20, 2014YesFunding provided by the Open Access Authors Fund

Search for the supersymmetric partner of the top quark in p(p)over-bar collisions at root s=1.8 TeV

We report on a search for the supersymmetric partner of the top quark (top squark) produced in t (t) over bar events using 110 ph(-1) of p (p) over bar collisions at roots = 1.8 TeV recorded with the Collider Detector at Fermilab. In the case of a light top squark, the decay of-the top quark into a top squark plus the lightest supersymmetric particle (LSP) could have a significant branching ratio. The observed events are consistent with standard model t (t) over bar production and decay. Hence, we set limits on the branching ratio of the top quark decaying into a top squark plus LSP, excluding branching ratios above 45% for a LSP mass up to 30 GeV/c(2)