This Week in Science

Science  24 Oct 1997:
Vol. 278, Issue 5338, pp. 549
  1. A molecular basis for ethanol sensitivity

    People and animals differ in their sensitivity to the intoxicating and addictive properties of ethanol, but the molecular basis for this variation has not been known. Miyakawa et al. (p. 698; see the news story by Pennisi, p. 573) show that mice missing one of the nonreceptor tyrosine kinases, Fyn, are hypersensitive to ethanol. They also lack the usual ethanol-induced phosphorylation of the N-methyl-D-aspartate (NMDA) subtype of the glutamate receptor (a likely mediator of ethanol's intoxicating effects) and show no ethanol tolerance, as monitored by measuring ethanol's ability to inhibit NMDA current. The ability of Fyn to phosphorylate the NMDA receptor is likely a determinant of an individual's response to ethanol.

  2. Not so slippery drops

    Superfluid helium-4 is hard to contain since it wets nearly all surfaces and flows freely without dissipation. Ross et al. (p. 664) show that on uniform cesium surfaces, however, superfluid helium-4 will form isolated droplets. The contact angle with the surface shows hysteresis depending on flow direction, and the droplets pin to the surface, refusing to flow down an incline.

  3. A coupled plate

    Although it is known that oceanic crust is spreading and subducted crust is being pulled down due to mantle convection, the coupling between crust and mantle is poorly understood. Along strike-slip faults such as the San Andreas, where plates slide past each other, the connection between the crust and mantle is not even well defined. Henstock et al. (p. 650) provide a velocity model based on a seismic experiment near the Mendocino Triple Junction in northern California that shows a narrow, vertical zone of deformation throughout the crust along the San Andreas fault. Strike-slip faulting appears to extend through the crust into the upper mantle, coupling deformation to mantle dynamics.

  4. Tube in a tube

    Carbon nanotubes are finding numerous applications and, together with their boron nitride counterparts, show great potential in nanoscale electronic applications. Heterojunctions of carbon and boron nitride nanotubes can be envisioned because of their different electronic properties. Suenaga et al. (p. 653) have now succeeded in realizing such a combined structure in nanotubes forming structures of carbon, boron nitride, and in some cases further carbon layers. A strong phase separation between the carbon and the boron nitride layers is observed.

  5. Birds in hand?

    One characteristic used to suggest that birds arose from theropod dinosaurs is hand morphology. The theropod hand is generally thought to preserve digits I, II, and III. Burke and Feduccia (p. 666; see the Perspective by Hinchliffe, p. 596) examined the hands and feet of developing embryos of birds, alligators, and turtles and show that their hands develop to preserve digits II, III, and IV. This pattern is in apparent conflict with the identification of the first digit in Archaeopteryx.

  6. Relaxation in water

    Mid-infrared spectra of water can reveal the orientational dynamics of the OH groups of water, and by using fast laser pulses, the dynamics of the vibrational and orientational relaxation can be resolved for specific subensembles of water molecules. Woutersen et al. (p. 658) found that there are two distinct time scales for orientational relaxation in the liquid. While weakly hydrogen-bonded water molecules may relax through both the fast and the slow relaxation process, strongly hydrogen-bonded molecules can only relax via the slow process.

  7. Getting to the infected site

    After an infection, T cells that are specific for the infectious agent enter the inflamed site. Part of this extravasation process involves cell surface adhesion molecules in the integrin and selectin families. In an in vivo study, DeGrendele et al. (p. 672) now show that when T cells were activated through their T cell receptors in the regional lymph nodes, CD44 on their surface was activated to bind to its ligand hyaluronate (HA) and acquired the capacity to roll. These activated cells next moved into the blood stream, and their entry into inflamed tissue required both CD44 and HA. Thus CD44 is a key player in the movement of cells into an inflammatory site.

  8. Why a Y?

    Although most chromosomes appear to contain a diverse set of genes, Lahn and Page (p. 675) have tested the theory that the Y chromosome may contain a functional organization. A systematic search of the Y chromosome (specifically the nonrecombining part, which includes 95% of the chromosome) revealed 12 novel genes or families of genes. These genes fell into only two classes: Housekeeping genes that are also expressed on the X chromosome and genes expressed specifically in the testis. In this way, comparable expression of housekeeping genes in males and females and the pressure to enhance male reproductive fitness are maintained.

  9. Population losses

    How many populations, demographically or genetically distinguishable groups, are there on Earth, and how rapidly are they being lost? Hughes et al. (p. 689; see the Perspective by Myers, p. 597) estimate, on the basis of published studies of population differentiation for a variety of taxa and distribution maps for different species, that there are several billion populations globally. Using the rate of tropical deforestation as a surrogate for habitat loss, and assuming that population loss parallels habitat destruction, they calculate that around 16 million individual populations are disappearing each year.

  10. Surprising survival

    The effect of mass extinction can be enormous in terms of species loss, but what is the effect on the preservation of the history of life? In a mathematical analysis, Nee and May (p. 692; see the Perspective by Myers, p. 597) show that even with an extinction event that removes at random 95% of all species, the bulk (80%) of evolutionary history will be maintained in the surviving 5%. The study may help focus conservation policy for dealing with the current anthropogenic biotic crisis, even though the importance assigned to species is usually not related to their evolutionary history.

  11. A fluid plate

    Plate tectonics, the idea that Earth's crust consists of rigid plates that separate and collide creating narrow zones of volcanism, deformation, and seismicity, is the standard model for crustal dynamics. England and Molnar have evaluated whether the rigid-plate approximation is appropriate for continental crust where deformation along the plate boundaries is typically diffuse. They modeled the stress and strain rates along the Tibetan plateau and found that the crust is more fluid-like, requiring the rigid-plate model to allow for some creeping flow in continental crustal plates.

  12. Useful bottlenecks

    Filters are often used to remove particles or molecules completely from solution, but usually they are not used to separate different small molecules in solution, as is done in chromatography. Jirage et al. have chemically plated polymeric membranes with gold to form nanopores with ends capped by even narrower orifices, or “bottlenecks.” They show that such membranes can be constructed to filter small molecules on the basis of size. Pyridine (with a molecular weight of 79) passed through such a membrane, but quinine (with a molecular weight of 324) could not be detected in the filtrate.

  13. X-rays in the water window

    Biological applications of x-ray methods are favored for wavelengths below 4.37 nanometers (where carbon in biomolecules absorbs strongly) but above 2.33 nanometers (avoiding the oxygen absorption of water). Spielmann et al. show that they can produce x-rays in the wavelength range with small laboratory source. They focused a very short (5 femtoseconds) near-infrared laser pulse into a narrow helium gas jet. In this way, neutral atoms are exposed to very high fields before they ionize, and the x-rays produced extend well into this “water window.”

  14. Fos and Jun in Drosophila development

    Biochemical experiments have shown that the proteins Fos and Jun function together as transcription factors. However, in vivo analyses in vertebrates have been complicated by the presence of multiple Jun and Fos family members. Riesgo-Escovar and Hafen have identified a genetic locus, kayak, that encodes the only known Fos-related protein in Drosophila, DFos. In an in vivo analysis, DFos and DJun are shown to cooperate in mid-embryogenesis for the process of dorsal closure by regulating the expression of decapentaplegic (dpp). During early embryogenesis, a second function for Fos is reported where the factor functions downstream of dpp, independently of DJun.

  15. Very expressive

    Now that the entire DNA sequence of the yeast Saccharomyces cerevisiae is available, it has become possible to look at genome expression at the level of the entire genome. DeRisi et al. have taken a set of DNA fragments representing nearly every gene in yeast and arrayed them on glass slides as probes for fluorescently labeled complementary DNAs (cDNAs). The cDNAs were made from RNAs expressed when the yeast was exposed to different metabolic conditions. Changes in gene expression were observed after glucose exhaustion and after gain or loss of a transcription factor in order to explore the potential of this developing technology.

  16. Overcoming the BAD

    The regulation of pro-death and anti-death pathways in a cell is incompletely understood. The protein kinase Akt phosphorylates on serine or threonine, is known to promote survival, and is activated when a cell binds a growth factor such as interleukin-3. A pro-death protein called BAD interferes with survival by binding to and inhibiting survival factors such as Bcl-xL, as long as BAD is not phosphorylated. Now del Peso et al. have connected the independent Akt and BAD observations with data that implicate Akt as the kinase that inactivates BAD, thus preventing cell death.

  17. MDC and HIV infectivity

    Initial findings that the chemokines RANTES, MIP-1α, and MIP-1β act as natural suppressors of human immunodeficiency virus-type 1 (HIV-1) infection have opened up new avenues for understanding HIV pathogenicity and therapeutics. However, it became clear that these chemokines could not explain all of the suppressive effect. Pal et al. have determined that the recently identified macrophage-derived chemokine MDC strongly suppressed infection of peripheral blood mononuclear cells under conditions in which the other chemokines were not effective.

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