This Week in Science

Science  25 Jun 2004:
Vol. 304, Issue 5679, pp. 1871
  1. Faster When Wet


    There are several landslides along the East Bay Hills, which are bounded by the Hayward Fault in Berkeley, California. In the absence of seismic events that can trigger rapid mass movements, these landslides move at rates of about 27 millimeters per year. It is difficult to track these slow and small changes over long time periods. Hilley et al. (p. 1952) measured small changes in many interferometric synthetic aperture radar (InSAR) scenes retrieved by satellites during a 9-year period and then followed the movement of permanent scatterers, such as rock outcrops. An increase in mass movement occurred during periods of higher precipitation caused by the 1997-to-1998 El Niño event.

  2. From Core Collapse to Compact Object

    When a Type II supernova explodes, theory suggests that the remnants of the explosion can collapse into a compact object, such as a neutron star or a black hole. Bietenholtz et al. (p. 1947, published online 10 June 2004) may have observed this process directly in radio observations of supernova 1986J. Although they have been observing SN 1986J since 1986 (its explosive birth was estimated to be in 1983), it was not until 1998 and then again in 2002 and 2003 that they started to see different patterns in the radio emissions suggestive of a black hole or neutron star. These observations provide information about the transition from explosion to core collapse and the youngest stage of growth of a compact object. Because the emissions will continue to increase in intensity, further study should help pin down the identity of this compact object.

  3. Arrestin's Nemesis

    The G protein-coupled receptors (GPCRs) transduce signals elicited by many different factors, including hormones, neurotransmitters, and cytokines. Negative and positive regulation of signaling for a majority of GPCRs is controlled by receptor association with the cytoplasmic protein arrestin. Arrestin regulates almost all G protein-coupled receptor (GPCR)-mediated signaling and trafficking. Wang et al. (p. 1940) now find that spinophilin, a multidomain protein that interacts with GPCRs, regulates both the signaling and trafficking of these receptors in vitro and in vivo by functionally antagonizing the multiple roles of arrestin in these processes.

  4. Where's My Mummy?

    The opioid system in the brain is involved in mediating pain, reward, and also plays an important role in drug addiction. What is its connection with the physiological and genetic basis of infant-maternal social attachment? Moles et al. (p. 1983; see the news story by Beckman) show that transgenic animals lacking μ-opioid receptors did not react to maternal deprivation with distress calls usually produced by normal pups, indicating deficits in attachment behaviors. Maternal cues were apparently less well recognized, possibly because a link between maternal stimuli and pleasurable states had not been formed.

  5. Climate Signals from the South

    Ice cores have provided records of differential responses of the Northern and Southern Hemispheres to recent glaciation and deglaciation events. Two reports focus on proxies from South America for following the related changes that occurred at lower latitudes. Environmental signals produced by vegetation can be used as proxies for climate change if the temporal relation between cause and effect are known. Hughen et al. (p. 1955, published online 20 May 2004) present records of tropical vegetation change from sediments off the coast of Venezuela which show that vegetation in tropical South America changed rapidly during the latter half of the last deglaciation, between 15,000 and 10,000 years ago. They used a record derived from terrestrial leaf waxes to show that ecosystem changes occurred decades after climate changes began, and that the lag of the vegetation response depended on the rapidity and magnitude of the climate change. The climate shifts in the high- and low-latitude North Atlantic were synchronous at the onset of the Younger Dryas. Lamy et al. (p. 1959; see the Perspective by Lynch-Stieglitz) present a record of sedimentary iron content—a proxy for terrigenous input—and sea surface temperature (SST) from the southern Chilean continental margin, which chronicles oceanographic and Patagonian ice sheet variability during the past 50,000 years. The timing of SST changes in the southeast Pacific corresponded to temperature changes in Antarctica, not Greenland, and the Patagonian ice sheet responded to those temperature variations with variable time lags. This nonuniform delay might help explain some apparent contradictions between certain South American terrestrial records.

  6. A Molecular Light Switch


    A photodiode carries current in only one direction in the dark, but when exposed to light, it allows some backward current to flow in proportion to the light intensity. Using two different types of helical peptides, Yasutomi et al. (p. 1944) constructed a molecular photodiode whose response depends of the wavelength of the light. The two types of oligopeptides used to form a monolayer are anchored differently to the substrate. These oligopeptides form different helices and can be switched independently when exposed to different wavelengths of light.

  7. Engineering Enzyme Activity into Proteins

    Designer enzymes would have tremendous practical applications, but rational design of new enzymes remains a challenge. Dwyer et al. (p. 1967; see the Perspective by Sterner and Schmid) have used structure-based computational design to introduce enzyme activity into a catalytically inert and structurally unrelated protein scaffold. By making about 20 mutations, they could introduce triose phosphate isomerase (TIM) activity into ribose binding protein. The designed “enzymes” support growth of Escherichia coli under gluconeogenic conditions.

  8. Puzzling Out Smells


    The mammalian sense of smell discriminates an incredible diversity of odors. In the olfactory bulb, each type of odor receptor links up to unique glomeruli that relay the signals up for higher processing in the brain. Immediately after birth, however, the connections from nasal epithelium to the olfactory bulb run helter-skelter. Zou et al. (p. 1976, published online 3 June 2004) have now analyzed the process of refinement using mice in which expression of two specific odorant receptors has been marked. Elimination of odoriferous input during specific times of development stalled an intrinsic process by which the inputs from multiple odorant receptors to a given glomerulus are sorted out to produce a mature glomerulus that responds to only one type of odorant signal. Thus, the experience of smell during a critical period is required for maturation of the odorant interpretation system.

  9. Timed to Within a Whisker

    Rats use their whiskers for fine tactile sensing just as we use our fingertips. However, complex stimuli elicit only sparse spike trains in individual neurons. How does the nervous system manage to extract sufficient information from sparse spike trains to accurately encode complex stimuli? Jones et al. (p. 1986) analyzed the encoding of tactile stimuli by trigeminal ganglion (whisker) neurons in the rat. The timing of spikes in the sensory afferents from the whiskers carry detailed information. Single whiskers encoded deflections with millisecond precision. Krupa et al. (p. 1989) examined the activity of neuronal ensembles through the different layers of primary somatosensory cortex while rats performed a whisker-dependent, active tactile discrimination task. Tactile stimuli were encoded by distributed populations of both excitatory and inhibitory neurons, but differences in encoding mechanisms were found in different cortical layers.

  10. Minis Modulate Dendritic Protein Synthesis

    Since their initial observation by Fatt and Katz in the 1950s, the functional significance of spontaneous miniature synaptic events (minis) has continued to intrigue neurobiologists. Sutton et al. (p. 1979) observed that blockade of synaptic activity leads to a reduction in protein synthesis. However, blocking miniature synaptic activity had the opposite effect and enhanced dendritic protein synthesis. These unexpected results suggest that local dendritic protein synthesis is regulated in a complex manner by different forms of synchronous and miniature synaptic events.

  11. Oscillating Assemblies of Neurons

    Oscillations in neuronal networks are more than an epiphenomenon in the brain. Buzsaki and Draguhn (p. 1926) review the neuronal origins and functional roles of different types of neuronal oscillations. These oscillations are used by the nervous system for a wide variety of tasks, including coding of information and memory consolidation.

  12. Mantle Earthquakes

    The mechanical strength of the upper crust, lower crust, and upper mantle determines how plates deform and how rapidly mountains can be uplifted. The relative strength of the different layers of the lithosphere can be estimated from the regions where earthquakes occur because these regions must be strong enough to accumulate the elastic strain needed to create a rupture. Chen and Yang (p. 1949) located 11 intraplate earthquakes in the mantle beneath the western Himalayas. The apparent strength of upper mantle can account for the rapid uplift of the mountains.

  13. A New Player Enters the Field

    The transcription factor nuclear factor-kappa B (NF-κB) controls the expression of genes whose products regulate the immune response, inflammation, cell proliferation, and apoptosis. Its activity is tightly controlled by the IκB kinase (IKK) complex that sequester NF-κB in the cytoplasm but releases the transcription factor to the nucleus in response to proinflammatory stimuli. Ducut Sigala et al. (p. 1963) have identified a regulatory subunit of the IKK complex that is required for IKK activation and is indispensable for NF-κB function.

  14. Second Path to Silence

    Certain parts of the genome of eukaryotes are packaged into “silent”' heterochromatin. The formation of specific regions of heterochromatin in fission yeast, Arabidopsis, and Drosophila involve the RNA interference machinery. Jia et al. (p. 1971) now show that in fission yeast, the binding of either of a pair of transcription factors, Atf1 and Pcr1, in the mating-type region acts in a parallel pathway of heterochromatin nucleation. The analysis links Atf1 and Pcr1, which are members of the ATF/CREB family of proteins involved in cellular response to environmental stresses, to nucleation of constitutive heterochromatin.