4i0 e 230 N. 4726

This Week in Scence , * .....

LETTERS m o ' ' '-''andFaa E i: A. J. Fidhind, A. N. C E.- q ;A N. Burdett; R. B. Z 4 jo n c.......... T. 0

EDiCTORAP Air_Poflution and Acid Ra in.. 617X~~~~~~~~~~~nfCU-O .8 q, . . . . . . . .. . .. .. . .

;X- .ffwAC Ene-tic Extrcwtion and Use i a'Nonadic Pastoral Ecosystem:.B.Coughenouretl ....................610

onservatiou--filila: M. R. Gebhardt, T. C. Daniel, E. E. Schweizer,R.R.Allaa

q4, ; ijPerapeive: Tmo Necrsis Ftor (TNF): 4 J Old.Structure of the Huma Intdreubi-2 Receptor Gene: W. J. Leonard et al.....-.

_~~~~~~J AM f_jt]Wt,]Xfi$JM e=br.%..- . . . . . . _,

HL-II and LAV: Similar or-enialA

11!; ' r - , O . . . . 8 .~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~rI enia?. . . .......6

ExPertu Cast Doiuts on X-ry Laser ..............4...........

RESEARCN A-to-riof MemuraneaeN ..................................Receptos..49-'New M at ft C r ................................... e h G c C2

Predictable Quake Damage .................................................. 65

BOOK REVIEWS Non-Proliferation and Safeguarding the Atom, reviewed by W. H. Donnelly; TheIntellectual and Social Organization of the Sciences, R. L. Simpson; TheBiology of Terrestrial Isopods, R. C. Brusca; Solar Maximum Analysis andSolar-Space Observations and Stellar Prospects, J. B. Zirker; BooksReceived ............................................................. 65

REPORTS The Structure of the Core of the Spiral Wave in the Belousov-ZhabotinskiiReaction: S. C. Maller, T. Plesser, B. Hess ............................... 66

Intracellular Free Calcium Localization in Neutrophils During Phagocytosis:D. W. Sawyer, J. A. Sullivan, G. L. Mandell ....... ...................... 66

High-Frequency Switching of Colony Morphology in Candida aibicans: B. Slutsky,J. Buffo, D. R. Soil ................... ................................. 66

Psoriatic Fibroblasts Induce Hyperproliferation of Normal Keratinocytes in aSkin Equivalent Model in Vitro: P. Saiag, B. Coulomb, C. Lebreton, E. Bell,L. Dubertret ........................................................... C6

Chromosomal Locations of Human Tissue Plasminogen Activator and UrokinaseGenes: B. Rajput et al .................................................. 67

Phytochelatins: The Principal Heavy-Metal Complexing Peptides of Higher Plants:E. Grill, E.-L. Winnacker, M. H. Zenk ........ ........................... 67

Wounding and Its Role in RSV-Mediated Tumor Formation: D. S. Dolberg,R. Hollingsworth, M. Hertle, M. J. Bissel .67

Iron(II) EDTA Used to Measure the Helical Twist Along Any DNA Molecule:T. D. Tullius and B. A. Dombroski .67

Hypoglycemia-Induced Neuronal Damage Prevented by an N-Methyl-D-AspartateAntagonist: T. Wieloch. 68

PRODUCTS AND Cell Culture Labware; Immunoassay; Syringe Filters; Data Recorder; ResearchMATERIALS Immunoassays; Spectrometer; Literature .6

COVER

Section (4.5 by 4.5 millimeters) of aspiral wave of chemical activity traveling through a 1-millimeter layer of -quiescent, excitable Belousov-Zhabotinskii reagent catalyzed by ferroinThe concentration distribution of ferroin was measured by means of a twodimensional spectrophotometer base(on a video camera, a video frame buffer, and a computer. The core of thtspiral-a singular site at which the ferroin concentration remains almost constant-is contained within the greeicircle. The colored curves are Archimedian spirals fitted to isointensity levels that correspond to the lowest (blueand the highest (red) measured intensities and to the intensity at the cop(yellow). See page 661. [S. C. MullerMax-Planck-Institut fir Ernmhrungsphysiologie, D-4600 Dortmund, Federal ReDublic of Germanvl

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SCIENCE:

ollution and Acid Rainrch being conducted on air pollution and acid rain is leading to apicture of the relative importance of SO2 and NOR. Political and

ry efforts have been focused on sulfur oxides because they pro-)out twice as much acid as NO,. However, that emphasis disregardsof NO. in the formation of toxic photochemical oxidants. Con-tudies at experimental facilities and observations in the field haveI effects of ozone and NO. as more damaging to vegetation thanle.ilight a complex series of reactions occurs in the troposphere,g photolysis of NO2 to produce excited atomic oxygen and thenceAdditional reactive species formed include hydrogen peroxide,iydroperoxide, peroxyacetic acid, and reactive free radicals, includ-NO3, and HO2. Maxima in the amounts of these species usually:tween 9:00 a.m. and 4:00 p.m. in midsummer. Monitoring hasconsiderable variability in concentrations of the oxidizing pollut-ited to abundance of the input substances. Some ozone may bethat originates in the stratosphere.been known that SO2, NO5, and 03 can have toxic effects on plants.Lrly days, experiments tended to be performed "scientifically"; thats were exposed in chambers in which the chemicals were tested oneUnder those circumstances, it was noted that concentrations of

I NO2 greater than ambient were required to produce notablery. Indeed, low concentrations of NO2 were sometimes beneficiala fertilizer effect). However, in the real world, pollutants are

together. When experiments were conducted with ambient middayr ozone present (for example, 50 to 100 parts per billion), toxicity:d. When the ozone was supplemented with NO2, there was usuallyLntial additional toxicity attributable to NO2. Similar results werehen ozone was supplemented with SO2.eleterious effects of ozone on agricultural crops have been docu-and analyzed in a report* issued by the Environmental ProtectionIt is estimated that a reduction in ambient ozone levels of 25would produce nearly $2 billion in benefits, while a 25 percentin ozone would lead to an additional $2.3 billion in crop losses.hotochemical oxidants, particularly OH, have an important role ination of SO2 leading to H2SO4. In the summer, with abundant OHthe oxidation proceeds much more rapidly than in winter. Sulfuremissions in winter and summer are about the same, but the totalDn of sulfate in January and February at stations in northeasternras found to be a third or less than what it was in midsummer.ion of nitrate showed little seasonal effect. Thus, at the crucial time?ring runoff, the contribution of nitric acid was about equivalent to;ulfuric acid.ives to reduce acid rain tend to be centered on the electrical utilitiestheir emissions of SO2. When new coal-fired plants are built, theyiired to include facilities for flue gas desulfurization. This addstially to the cost of the plant, decreases the efficiency of energyion to electricity, and diminishes overall reliability. While theis effective in capturing SO2, it is ineffective in removing NO. Anyaimed at reducing acid rain should take into consideration the totalation problem, including NO,. Efforts to reduce SO2 emissionsbe accompanied by a corresponding emphasis on reducing NO5,-r the source. For the electrical utilities, this would mean providing:xibility to use technologies that reduce both SO2 and NO,. But in1, the other large contributors to NO5, such as motor vehicles,-ome under scrutiny.-PHILIP H. ABELSON

Jams, S. A. Hamilton, B. A. McCarl, The Economic Effects of Ozone on Agricultureental Research Laboratory, Environmental Protection Agency, Corvallis, Ore. 1984).