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Apoptosis-inducing factor (AIF) and AIF-homologous mitochondrion-associated inducer of death (AMID) are both mitochondrial flavoproteins that trigger caspase-independent apoptosis. Phylogenetic analysis suggests that these two proteins evolutionarily diverge back from their common prokaryote ancestor. Compared with AIF, the proapoptotic nature of AMID and its mode of action are much less clarified. Here, we show that overexpression of yeast AMID homologue internal NADH dehydrogenase (NDI1), but not external NADH dehydrogenase (NDE1), can cause apoptosislike cell death, and this effect can be repressed by increased respiration on glucose-limited media. This result indicates that the regulatory network of energy metabolism, in particular the cross-talk between mitochondria and the rest of the cell, is involved in Ndi1p-induced yeast cell apoptosis. The apoptotic effect of NDI1 overexpression is associated with increased production of reactive oxygen species (ROS) in mitochondria. In addition, NDI1 overexpression in sod2 background causes cell lethality in both fermentable and semifermentable media. Interruption of certain components in the electron transport chain can suppress the growth inhibition from Ndi1p overexpression. We finally show that disruption of NDI1 or NDE1 decreases ROS production and elongates the chronological life span of yeast, accompanied by the loss of survival fitness. Implication of these findings for Ndi1p-induced apoptosis is discussed. INTRODUCTIONApoptosis is a form of programmed cell death essential to the development and tissue homeostasis of multicellular organisms. Although programmed cell death or apoptosis is widely accepted as an essential process in multicellular organisms, until a few years ago it was generally considered to be unnecessary for single cell organisms that do not form multicellular structures. Recent studies demonstrated that apoptosis also occurs in bacteria and yeast (Madeo et al., 1997;Engelberg-Kulka and Glaser, 1999;Wadskog et al., 2004). Like mammalian cells, yeast cells (Saccharomyces cerevisiae) undergoing apoptosis show characteristic markers such as DNA cleavage, apoptosis-typical chromatin condensation, externalization of phosphatidylserine, and cytochrome c release from mitochondria (Madeo et al., 1997;Manon et al., 1997;Ludovico et al., 2002). Reactive oxygen species (ROS), the central regulator in the metazoan apoptosis, has also been identified as essential in at least some yeast apoptosis, indicating that the similarity between the two processes is not restricted to the appearance (Madeo et al., 1999). The past several years have seen the discovery of several yeast orthologues of crucial apoptotic regulators (Laun et al., 2001;Ligr et al., 2001;Blanchard et al., 2002;Madeo et al., 2002;Chae et al., 2003;Fahrenkrog et al., 2004;Fannjiang et al., 2004;Herker et al., 2004;Sauder and Aebi, 2004;Ahn et al., 2005). These findings firmly established that yeast and metazoan apoptosis are in essence the same cellular program and lay the foundation of using ...

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Nonflammable materials based on renewable ammonium alginate and nano fillers (nanoscale magnesium hydroxide, nanoscale aluminum hydroxide, layered double hydroxide, sodium montmorillonite, and Kaolin) were fabricated through a simple, environmentally friendly freeze-drying process, in which water was used as a solvent. A simple and economic post-cross-linking method was used to obtain homogeneous samples. The microstructure of the cross-linked alginate aerogels show three-dimensional networks. These materials exhibit low densities (0.064-0.116 g cm(-3)), low thermal conductivities (0.024-0.046 W/m K), and useful mechanical strengths (0.7-3.5 MPa). The aerogels also exhibit high thermal stabilities and achieve inherent nonflammability with limiting oxygen indexes (LOI) higher than 60. Related properties were conducted and analyzed by cone calorimeter (CC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). These results combine to suggest promising prospects for use of these aerogel nanocomposites in a range of applications.