Editors' Choice

Science  25 Jan 2008:
Vol. 319, Issue 5862, pp. 387
  1. PHYSIOLOGY

    Dying For Iron

    1. Lisa D. Chong

    Food supplements, such as the blue-green alga popularly referred to as spirulina, are used worldwide and can serve as valuable sources of vitamins and minerals. Iron is one of the many elements that are needed for life yet are toxic in excess. In the small intestine—particularly in the first 12-finger-width segment known as the duodenum—epithelial cells express the iron-regulatory proteins (IRP1 and IRP2) that maintain iron homeostasis by adjusting the expression of proteins that absorb, metabolize, and export this essential dietary component. By selectively eliminating the expression of IRPs in these cells in mice, Galy et al. demonstrate that they are also required for intestinal development. They observed that mice deficient in IRPs suffered from weight loss and dehydration and died a few weeks after birth. Surprisingly, the mice manifested close to normal blood and liver iron content; on the other hand, intestinal villi were malformed, and duodenal epithelia displayed degenerated mitochondria (perhaps a sign of diminished iron-sulfur cluster synthesis) and increased cell death, which probably contributed to impaired water and nutrient absorption. Thus, although the absence of IRPs in the intestinal epithelium does not acutely alter systemic iron levels, it does affect intracellular processes that control intestinal morphogenesis and survival. — LDC

    Cell Metab. 7, 79 (2008).

  2. APPLIED PHYSICS

    CARS to See Spores

    1. Jake S. Yeston

    Selective detection of airborne biohazards in a background environment filled with all manner of pollen, dust, and debris remains a serious challenge. Pestov et al. have pursued a promising approach based on coherent anti-Stokes Raman scattering (CARS) spectroscopy. In general, Raman-based techniques should offer high specificity based on molecular vibrational signatures, but they have been plagued by high background noise due to nonresonant scattering of the light by the molecules in the beam path. The authors' group previously addressed this shortcoming using a precisely timed series of broadband pump and Stokes excitation pulses followed by a delayed narrowband probe, a modification of the more conventional CARS protocol in which pump and probe pulses are closer in time and duration (see Pestov et al., Reports, 13 April 2007, p. 265). They now show that by shifting wavelengths from the visible to the lower-energy near-infrared regime, they can increase the signal strength by raising photon intensity while avoiding damage to the sample that would preclude identification. Further optimization of the pulse bandwidths and relative timings allowed detection of as few as 10,000 bacterial spores with a single laser shot. — JSY

    Proc. Natl. Acad. Sci. U.S.A. 105, 422 (2008).

  3. CHEMISTRY

    Bright Yellow Glow

    1. Phil D. Szuromi

    One approach for creating white-light sources is to integrate a yellow phosphor with a blue light-emitting source. Yellow phosphors usually comprise rare earth (Ce or Eu) ions in an inorganic host matrix. Recently, it was shown that large-channel Zn-Ga phosphates could exhibit yellow-to-white luminescence. Yang and Wang now report that an organic-inorganic microporous analog is a highly efficient yellow phosphor with photoluminescent quantum efficiencies that can exceed 40%. These materials contain hexameric Ga clusters, Ga6(OH)4O26, that are connected in a two-dimensional network through bridging phosphate and oxalic acid groups. This anionic framework is charge-balanced by organic dications. The authors suggest that the intrinsic disordered nature of the lattice creates defect sites at pairs of Ga atoms in the largest pore that act as activator sites for emission. — PDS

    J. Am. Chem. Soc. 130, 10.1021/ja7101423 (2008).

  4. PHYSIOLOGY

    Give Me Oxygen (or Not)

    1. Paula A. Kiberstis

    Recent memorial tributes celebrating the accomplishments of Sir Edmund Hillary, one of the first two men to scale Mount Everest, are a fascinating reminder of the ability of mammals to tolerate low oxygen levels (hypoxia). The physiological response to hypoxia involves the transmission of signals from cellular oxygen-sensing pathways to metabolic enzymes that consume oxygen, but how this occurs is poorly understood. Aragonés et al. have studied mice that are deficient in an oxygen-sensitive enzyme that regulates the stability of a transcription factor (hypoxia-inducible factor-1), which is known to activate genes involved in cellular adaptations to hypoxia. Analysis of skeletal muscle in the mutant mice revealed that the loss of this enzyme, called prolyl hydroxylase-1 (Phd1), lowered oxygen consumption by reprogramming basal metabolism; that is, by inducing a selective decrease in glucose oxidation and a switch to more anaerobic glycolysis. Muscle tissue in the Phd1-deficient mice was protected from the necrosis typically seen under acute oxygen deprivation, an outcome apparently due to reduced formation of harmful reactive oxygen species. These findings not only identify Phd1 as a key molecular player regulating hypoxia tolerance but raise the possibility that pharmacological inhibition of the enzyme could have beneficial effects in diseases characterized by oxidative stress and ischemic damage. — PAK

    Nat. Genet. 40, 10.1038/ng.2007.62 (2008).