Science (Vol. 307, No. 5711, February 2005)

157 Pages·2005·19.772 MB·English

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edited by Stella Hurtley and Phil Szuromi
Stuffed with Pulsars
tals.Rich et al.(p.910;see the Perspective by Martin and Luo) now
Globular clusters contain thousands to millions of stars and are among show that the ear of the earliest known monotreme,from the Early
the oldest objects in the universe.Ransomet al.(p.892;see the Cretaceous,has only one bone.Thus,the complex ears of mammals
Perspective by Lorimer) studied the globular cluster,Terzan 5,with the arose separately and converged in different mammalian lineages.
Green Bank radio telescope and discovered 21
new millisecond pulsars,about half in binary
Decisions,Decisions…
systems (two with close enough orbits to Cuprates in Real-
allow repeated eclipses and others with What makes an individual
and Momentum-Space
unusually wide orbits or odd companions), decide to choose one set of
several with some of the highest rates of rota- Recent real-space imaging experiments on the high- activities over another? Brigg-
tion,and two with masses that exceed the temperature cuprate superconductors have revealed the man et al.(p.896) tried to
theoretical limits for neutron stars.This existence of a “checkerboard”charge-ordering pattern unravel the mechanisms
menagerie of extraordinary pulsars has much on the surface.This structure has received much atten- underlying behavioral choice in
to tell us about pulsar physics,general relativ- tion in terms of its relation to understand- the relatively simple nervous
ity,and globular cluster evolution. ing the mechanism underlying super- system of the medicinal
conductivity in these materials.To leech.They presented an
strengthen the case,what is now animal with a constant
Through a Glass,Darkly
needed are samples that allow stimulus that repeat-
Most carbon nanotubes are grown with the direct comparison between edly produced two
aid of catalyst particles that reside at the tips real-space and momentum- different,mutually
of the growing tubes.However,how do nano- space data.Working with the exclusive behaviors
tubes grow during the catalyst-free process sodium-doped oxychloride with roughly equal
in which an arc is struck between two superconductor,Shen et al. probabilities.This
graphite rods? De Heer et al.(p.907) studied (p.901) present angle-resolved approach allowed the
this process in detail and found the formation photoemission data that provides authors to focus on
of amorphous carbon beads on a small num- complementary data in momentum neurons involved in deci-
ber of the multiwalled tubes,which suggests space.Interpreting the similarities and sion-making rather than the
that the tubes grow in a manner similar to differences found in the real-space and neural effects of sensory input,
other crystal-growth processes. momentum-space experiments may provide some guid- which was invariant.Neurons
ance in revealing the underlying mechanism. exhibiting decisive roles in the
choice between swimming and
Shifting Reference Frames
crawling were identified by
There are several chains of volcanoes and seamounts within the combining high-resolution voltage-sensitive dye imaging with the
Pacific plate that have been used to track its motion,given the sophisticated mathematical methods of principal component analysis
assumption that there is a fixed hot spot that can serve as a reference and linear discriminant analysis.A candidate key neuron highlighted
frame.The Hawaiian-Emperor chain shows a sharp bend which indi- by these analyses (neuron 208) could selectively bias the decision to
cates that a change in growth swim or crawl.
direction occurred at about 47 mil-
lion years ago. Koppers and
Bt Receptor Defines Specificity
Staudigel(p.904) dated a similar
bend in two volcanic chains in the The Bt toxin,a crystalline protein produced by the soil-borne bac-
southern Pacific plate and found terium Bacillus thuringiensis,is used to control insect pests in agricul-
that the chains changed directions ture.After the toxin is ingested by insect larvae,the toxin damages
at different times.The lack of syn- the gut of susceptible insects.Griffitts et al.(p.922) examined the
chronicity among the three bends mode of action of Bt.Several genes known to control resistance to the
in the three volcanic chains means Bt toxin encode enzymes that synthesize a set of glycolipids found in
that the hot spot must have been nematodes and insects.These glycolipids function as the receptor for
GEL moving or the plate properties were different in different regions. the Bt toxin explaining why the toxic effects of Bt are limited to
DI
ND STAU Tuhseedse t ore tsrualctks ipnldaticea mteo tthioatn as afinxde dt hhaott -ssopmoet rreefveirseionncse ofrfa pmlaet eca tnenctootn biec nematodes and insects.
OPPERS A histories may be needed. Natural Brominated Bioaccumulators
K
ET AL.N ; Ear Origins Hsoamloeg ceansaetse dw iotrhg paontice nctoimallpyo tuonxdics c coanns eaqcucuemncuelsa.tSeo imn ea noifm thael steis,ssuuechs, ains
HE
S All living mammals have a distinctive ear containing three bones the polybrominated diphenyl ethers (PBDEs) used as flame retardants,
M):
O BOTTO (ehvaomlvemde frr,oamnv filo,uarn odr s mtirorruep b) oanneds a t hsiantg mlea jdaew u bpo tnhee. Tjahwes oef s tthruecirt urerpes- hcoavmep ionduunsdtsr,iaslu ocrhig ains sm.Tehteh ooxriygliantse odf psoomlyber colmasisneast oefd b dioipahcecunmyl ueltahtienrgs
OP T tilian ancestor in the Mesozoic.It has been thought that this evolu- (MeO-BDEs),have been uncertain.Teuten et al.(p.917) extracted
CREDITS (T t(tiohne foecwc uerxrteadn tin m aa bmamsaal lms tahmatm laayl ,epgrgios)r ftroo mth me saprsliutp oiaf lms aonndo ptrlaecmenes- more than 10 kilograms of blubber from a fataCllOyN TsItNrUaEnDdOeNdP ATGrEu8e1’3s
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beaked whale,and isolated MeO-BDEs at 99% purity for radiocarbon analysis,which reliably
distinguishes carbon of ancient and recent origin.The carbon content of MeO-BDEs was over-
whelmingly recent,indicative of a natural rather than industrial origin for these compounds.
Endangered Ginseng?
Ginseng is a highly valued understory forest plant that is widespread in eastern North Amer-
ica,although at low population density.It has many uses in traditional Asian medicine and
strong cultural ties to Appalachian communities.Population viability analyses carried out by
McGraw and Furedi(p.920;see the news story by Stokstad) suggest that high rates of
browsing by burgeoning populations of white-tailed deer threaten to cause extinction of
most,if not all,wild American ginseng populations within a century.The white-tailed deer
represents a keystone species,with large and cascading effects on the natural community.
Loss of the wild populations of ginseng and other potentially valuable understory herbs
would have significant economic and cultural consequences.
Earliest Influences
The two main lineages of T cells to emerge from the thymus are distinguished by the T cell
receptors that they carry,either αβor γδ,which confer distinctive functional properties on each
cell type.Within the thymus,the development of the two lineages has been thought to occur
independently.Silva-Santos et al.(p.925,published online 9 December 2004;see the Perspec-
tive by Rothenberg) now show that the features peculiar to γδ T cells are not generated
autonomously but are conferred directly on the cells by their immature αβthymic counter- Thefollowingorganizations
parts.This process required signaling via a pathway already known to be essential for lymphoid haveplacedanadin the
organogenesis and generating effective immune responses.Thus,the developmental interac- SpecialAdvertisingSection
tion between two lineages of T cell imparts fundamental features on one of the cell types.
Advances in:
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As neurons wire together networks of communication,they need to
know not only which other neurons to connect to,but in which direc- AmplifyingNucleicAcids
tion they should send signals.Such polarity within a single neuron is
reflected by its morphology:multiple short dendrites receive signals,
and the single longer axon sends signals.Kishi et al.(p.929) examined
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therapeutic benefit.In a chemical screen,Boyce et al.(p.935) identified a small molecule (salu-
brinal) that protects cells from ER stress–induced apoptosis.Salubrinal selectively inhibited the
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Putting the Methyl in Plant MicroRNAs
MicroRNAs (miRNAs),~22 nucleotide RNAs encoded in the genomes of both plants and ani-
mals,have the potential to regulate the expression of a diverse array of genes.Numerous fac-
tors modulate miRNA function,for example,Arabidopsismutants of HEN1 show reduced
miRNA abundance,as well as miRNA size heterogeneity.Yuet al.(p.932) now show that
HEN1 methylates miRNAs on the ribose of their last nucleotide.Methylation plays an
ET AL.HI ifmerpinogr tRaNntA rso.lIet iins rliikbeolsyo tmhaatl RmNaAn yfu,anncdti opno sasnidb lsyt aablli,lpizleasn et xmogiReNnoAuss alyr ein stirmodiluarcleyd m smetahlyl ilnatteedr-,
KIS whereas present evidence suggests that animal miRNAs are not methylated.
DIT:
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DITORIAL
Where Science Meets Society
T
he theme for next week’s American Association for the Advancement of Science (AAAS) annual
meeting, “The Nexus: Where Science Meets Society,” reminds us of many events of the past few
years that suggest that the relationship between science and society is undergoing significant stress.
Some members of the public are finding certain lines of scientific research and their outcomes
disquieting, while others challenge the kind of science taught in schools. This disaffection and shift
in attitudes predict a more difficult and intrusive relationship between science and society than
we’ve enjoyed in the recent past.
Examples of these strains in the relationship include sharp public divisions about therapeutic or research
cloning and stem cell research. Although many understand the potential benefits of such research, they also are
troubled about scientists working so close to what they see as the essence and origins of human life. Last year,
ideology came dangerously close to publicly trumping science when the U.S. Congress failed by
only two votes to defund a set of grants from the National Institutes of Health on sexual behavior,
HIV/AIDS, and drug abuse that made religious conservatives uncomfortable, even though the
research was critical to solving major public health problems. And, of course, the scientific
community is enmeshed in a continuing battle to keep the nature of science clear in debates about
whether schools should be allowed to teach non–science-based “intelligent design theory” alongside
evolution in science classrooms.
The common thread linking these examples is that science and its products are intersecting
more frequently with certain human beliefs and values. As science encroaches more
closely on heavily value-laden issues, members of the public are claiming a stronger
role in both the regulation of science and the shaping of the research agenda.
To many, this appears to be a new dimension of the science/society relationship
(in truth, it may be a recurrent dimension, because the same issues have been prominent
at other historical moments). We’ve been used to having science and technology evaluated
primarily on the basis of potential risks and benefits. However, our recent experience
suggests that a third, values-related dimension will influence the conduct and support of science
in the future. Taizo Nishimuro, chairman of the board at Toshiba Corporation, suggested at the Science
and Technology in Society Forum in Kyoto, Japan, in November 2004 that whereas historically science
and technology have changed society, society now is likely to want to change science and technology, or at least
to help shape their course.
For many scientists, any such overlay of values on the conduct of science is anathema to our core principles
and our historic success. Within the limits of the ethical conduct of science with human or animal subjects, many
believe that no scientifically answerable question should be out of bounds. Bringing the power of scientific
inquiry to bear on society’s most difficult questions is what we have done best, and that often means telling the
world things that it might not initially like.
Independence and objectivity in the shaping and conduct of science have been central to our successes and our
ability to serve society. Still, our recent experiences suggest that the values dimension is here to stay, certainly for
a while, and that we need to learn to work within this new context. Protesting the imposition of value-related
O
ON BY JEFFREY PEL cddoiissnccAsoutnrusa sraiisnnlettg.es Wr tonhneae t smhicvaieevea enin schi enta oghd a aassndo bdome pueets neas uft hmucelcnu euecssshsus awmolf ior toehresu pp ri ronwoncgoslrreuak,s m.bi vWuse te s ia utsp chdphoor ueoaslsadn ct ’thhtr e ywt hNtooara tkf t ieibnonedngc acaalogu Hmesesum imoto tdahnnoe g erGr sconeou’ntmn ordmem stehou rnnRoaiutetiesge ehswa oaritcsphhse e tnIhrn,et irs vaptietutiluobytln eiiac’nsl.
N SERVICES,ILLUSTRATI EaathnntahddtSi ihcRinmaoeslwalp,i nl gLytihite opyegnr yaio,s l tr wedeaslohnatiiidtnnce ghgS t oottbhhc roeeii a ntishlnga ecIsmrmu sebrcps etiilhleoiicinnenatf goit sai foot nvsvnd aets lovr up gaaereln ocutdhgoe enr osarsvy miewdsrt.ei e atrAmhan tndrsioo e.etnlxhisgpe iierno cteutoxis nt ahlgmee aa pcd dloeeinrf sfdies ua rctnehtnd eat neAotduhA tuiccAsoiesSm ot’ssef .tsD ocL iiedeatinl’ssocc getur ucyseos s nosofcnmiir eSemn cdstiii etfphnilceoc meoa,ld adEvc aatyhdn aiaccngesdes,
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UBLICATI discussion and see how that goes for a change. Alan I.Leshner
D BY AAAS P Chief Executive Officer,American Association for tEhxee cAudtviaven cPeumbleisnhte orf, SScciieennccee
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DESIG 10.1126/science.1110260
©2004
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DITORS’ HOICE
HIGHLIGHTS OF THE RECENT LITERATURE
edited by Gilbert Chin
violet irradiation through an
ECOLOGY/EVOLUTION optical fiber inserted into the
A Forest Sere sample probe.The appearance
of a 129Xe NMR signal,shifted
Tropical rainforests,despite their locations,can suffer from more than 700 parts per
drought,and during severe droughts,a rainforest can even million upfield from the free
become susceptible to fire.Evidence of past forest fires,in solvent,confirmed that a Xe
the form of charcoal deposits,can be found in many atom was coordinated to the
parts of the humid tropics,but there has been little unsaturated Re center,and
documentation of the effects of such catastrophic further evidence came from
disturbances on the ecology of tree species. nuclear spin coupling of the
Van Nieuwstadt and Sheil have examined the bound Xe to the PF ligand,
3
effects of drought and fire in a lowland rainforest in observed via 31P and 19F
East Kalimantan,Indonesia,by censusing live and NMR spectra.The compound
dead trees in adjacent burned and unburned areas.The persists for hours in liquid Xe
drought of 1997–1998,one of the most severe ever in a at –110ºC.— JSY
tropical rainforest,was followed by fire.The consequences Proc.Natl.Acad.Sci.U.S.A.102,1853
of the drought were more pronounced in the larger, (2005).
mature trees:Nearly half of the trees with trunk diameter
>80 cm were lost,whereas less than one-quarter of trees Views from within (inset) and above IMMUNOLOGY
<20 cm in diameter died.In contrast,fire killed smaller the forest,showing the effect of Arresting Connections
saplings disproportionately:Almost no individuals <10 cm drought on larger trees.
in diameter survived.Some species (particularly dipterocarp Our T cell repertoire is individ-
and palm) withstood fire better than others.In sum,drought and fire both reduce biomass,alter ually tailored by positive
patterns of forest dynamics by removing reproductive individuals and regenerating saplings,and selection,during which devel-
change the relative abundances of species,but do so in different ways.— AMS oping thymocytes are vetted
J.Ecol.93,191 (2005). for their ability to interact
appropriately with self
peptides bound to major
CELL BIOLOGY stimulated transcription by survive stress induced histocompatibility complex
Astrocytes and Stress activating a promoter with by ischemic or hypoxic proteins.Using two-photon
known ER stress-responsive conditions.— LDC microscopy,Bhakta et al.
Eukaryotic cells sense stressful elements (ERSEs).ER stress Nature Cell Biol.10.1038/ncb1213 scrutinized the calcium
conditions,such as the induced OASIS expression in (2005). concentration and motility
accumulation of abnormal astrocytes but not in neurons of thymocytes undergoing
proteins,in their endoplasmic or fibroblasts.Knockdown of CHEMISTRY positive selection.To maintain
reticulum (ER) by means of OASIS expression reduced Xe as a Ligand the intricate thymic stromal
the aptly named unfolded the expression of BiP,whereas environment,thymocytes
protein response (UPR). OASIS overexpression conferred For more than 20 years,liquid were labeled with a dye and
10.1038/NCB1213 (2005) Atepfohxrsolep dat reUi enpinsPgrssRo i,cot ssheunyacc spothtief eva redmso atmn mhaineeca tc EBgihvReiaaP -pn.tcreioosstnm ettih,rnoe-l rrateeysssptpiresoot–cansynpstecee ects io tfmoi Ec a Rcmye s leutl crtdeihlesiaazsne.tiTh sah mi cun estl,ol xsrcueooesaulnmvcaoetplninlovy t(eu Xtf nhtoedror)as usnh ttgsahuhistad tibtyo oeainnfet tgmana s hcue ikitsng aesehldo rly tlav,se nats itinwnnhoat ywtrnm otdhdaieicckur ehctei edsppds loaua isbcenioet.tiUu,ovtt nehs i dlysniecem merl esocuc ocotcynfiho tdi ennittsh tidaoeicndts
OL. Kondo et al.have determined such as alkanes and fluoro- same way as naïve lymphocytes
URE CELL BI tnhearvt oaustsr soycsytteems oefm thpelo cye annt rEaRl OprAoSteISin ER stress ER cspaerbcotrnoss.cNoepvye srhthoewleesds ,tihnaftr ainred hlyamvep hb eneond oesb.sHerovwedev teor ,dtoh iisn
NAT stress transducer called old some cases,the Xe reacted behavior altered in positive
ET ALDO ., asustbrsotcayntcee s(pOeAciSfIiSca).llOy AinSdISu cised Astrocytes S1P,S2P tcreanntseiresn,tbliyn wdiintgh wthieth m aental stheylemctoiocynt eens vsilroownminge ndtosw,wnith
N
OM) KO ainn t EhRe staramnes mtraenmscbrriapntieo np rfoatcetoinr nucleus eonf tah haylpdyr ocgoemn pbaornadbl.eB atoll teht aatl . cthoenisri dinetrearbalcyt iaonnds pwroitlho ncgeilnlsg
OTT family as CREB/ATF.When have characterized a rhenium of the thymic stroma.
DT;(B astrocytes were treated with (Re)–Xe linkage directly by low- Furthermore,these thymocytes
WSTA agents that disrupt protein temperature nuclear magnetic displayed increased oscillations
NIEU glycosylation or calcium OASIS-N NF-Y ATF6OASIS-N? resonance (NMR) spectroscopy. of intracellular calcium,
OP) VAN hwoams celeoasvteadsi,sa nind tithse N E-Rt,eOrmAiSnIaSl CRE ERSE BiP T(iPhreCyp p)Rreep(CarOe)d PaF Xe(w sohleurtei oiPnr Copf iInndteicrrautpivteio onf ocef lClual2a+r saicgtnivaalitnigon.
DITS:(T domain moved into the Pathway for OASIS activation of is isopropylcyc2lop3entadienyl)
CRE nucleus.This fragment the UPR. and induced CO loss by ultra- CONTINUEDONPAGE819
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