British scientist Arpad Pusztai,who was fired last year from theRowett Research Institute in

Aberdeen, Scotland, and banned fromspeaking to the press for a while, told a parliamentary select committee onMarch 8 in London he had no regretsabout his comments that led to his dis-missal. Humans, he had said, were beingused as guinea pigs in a vast experimentwith genetically modified (GM) foods.

Pusztai’s testimony to the committeefollowed headlines in British newspapersscreaming that a scientist had beengagged and his findings suppressed tokeep secret that genetically modifiedfoods threaten health. Conspiracy theo-ries abounded—namely, that PresidentBill Clinton had personally pressured

Prime Minister Tony Blair to give bio-technology companies, including Mon-santo, a freer rein in planting GM crops.An admission on March 1 from JohnPrescott, secretary of state for Environ-ment, Transport and the Regions—thatthe British government has indeed re-ceived representations from its U.S. coun-terpart about GM crops—did not help.

The furor started last August, whenPusztai released to the media resultsthat he said indicated that rats fed pota-toes genetically engineered to contain alectin from the snowdrop plant—a nat-urally occurring insecticide—had suf-fered damaged immune systems andstunted growth of vital organs. The re-sults stood in stark contrast to safetyclaims made by biotech companies andto the received wisdom of the harmless-ness of transgenic crops.

Four days after his announcementPusztai, a renowned scientist who pio-neered studies on the effects of lectin,was suspended. The Rowett institutestated he had muddled his findings. Qui-etly, over the ensuing months, Rowettinvited a group of independent scien-tists to audit Pusztai’s work—and the

audit found that his conclu-sions were indeed erroneous,although it absolved him ofthe more serious charge ofscientific fraud.

Other scientists, though,came to Pusztai’s defense.Two researchers forwardedhis data to 21 scientists, wholater issued a memorandumin February that said, “Weare of the opinion ... that theconsumption of the GMpotatoes by rats led to sig-nificant differences in organweights and depression oflymphocyte responsivenesscompared to controls.”

A study that criticized theRowett audit and confirmedPusztai’s results also got somebacking. Done by pathologistStanley Ewen of AberdeenUniversity, a friend of Pusz-tai’s, the work was examinedby Thorkild Bøg-Hansen, alectin expert from the Univer-sity of Copenhagen (and oneof the researchers who for-warded Pusztai’s results toothers). He concluded that

“Dr. Ewen’s results clearly showed theerrors in the audit report that followedDr. Pusztai’s suspension from the Row-ett Research Institute. The experimentsclearly showed that . . . the GM pota-toes caused a major intraepithelial lym-phocyte infiltration similar to inflam-matory responses.’’

Vyvyan Howard, a toxicopathologistat the University of Liverpool and Pusztaisupporter, says that the results showedthe main risk of GM food to be “long-term, low-dose toxicity from subtlechanges to the nature of the food chain.”He describes Pusztai’s findings as unex-pected and not totally attributable to thelectin. In other words, the genetic modifi-cation process itself was causing unpre-dictable outcomes. Speculations includevirus promoters (mechanisms used toswitch on the inserted genes) and possi-ble unintended switching off of beneficialgenes. “It is precisely this type of findingwhich means that animal testing for de-velopmental toxicological effects is essen-tial,” says Howard, who also argues thatthe “mixture problem” must be ad-dressed as well. “None of us eat only asingle food. The effects of mixtures to myknowledge have not been addressed,” henotes, concluding that “human volunteertesting would probably be advisable.”

Tom Sanders of King’s College Lon-don, a nutrition expert and a member ofthe government’s Advisory Committeeon Novel Foods and Processes, is notconvinced by Pusztai or his supporters.After reviewing Pusztai’s experiments, hemaintains that all they definitivelyproved was that eating raw potatoes,which are indigestible, is harmful tomammals—“something that has beenknown for many years,” he asserts.

Sanders also says that carrying out fullpharmaceutical-style testing on GMfoods would be impossible, because low-level poisons ostensibly from GM prod-ucts would not appear in ordinary toxi-cological testing. He also points out thattesting for human allergenicity with ani-mals is not possible. He suggests insteadthat known allergens be banned for usein GM food, along with markers used totell which foods have been modified.

Jim Dunwell of the plant sciences de-partment at the University of Readinghas another point against Pusztai: allpotatoes are not alike, and toxin levelscan vary widely between different tu-bers before any modification is carried

News and Analysis34 Scientific American May 1999

TECHNOLOGY AND BUSINESS

LEAVING A BAD TASTE

The furor in Britain raises health safety concerns about genetically

modified foods

BIOENGINEERING

A LOAD OF CROP?Greenpeace protests against genetically modifiedfoods in front of 10 Downing Street in London.

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Copyright 1999 Scientific American, Inc.

The development of quantummechanics, the underlying lawsthat govern matter and energy

on the scale of atoms and electrons, hasnot only revolutionized our understand-ing of the universe but also has given ussuch technologies as the transistor, thelaser and magnetic resonance imaging.Now Philip H. Bucksbaum and his co-workers at the University of Michiganhave combined several recently devel-oped techniques with a feedback systemto control the very essence of quantumparticles: their wave functions. TheBucksbaum experiment “is true quan-tum engineering,” says physicist MichaelG. Raymer of the University of Oregon.“It should open up many new possibili-ties, most of which we cannot evenimagine now.”

A wave function defines the physicalstate of a quantum object. Wave func-tions are slippery characters, tied toprobabilities, not certainties. They obeythe famous Heisenberg uncertaintyprinciple: if one characteristic is welldefined, a related feature must be highlyuncertain. For instance, an electron witha very precise position must have a widerange of possible velocities. Neverthe-less, during the past decade a number ofresearch groups have assembled tech-niques for manipulating and analyzingcomplete wave functions in detail.

Bucksbaum and his graduate students

Thomas C. Weinacht and Jaewook Ahnapply their technique to a type of quan-tum state known as a Rydberg state,which occurs when an electron in anatom is excited to such a high energylevel that it barely remains bound to theatom. “Rydberg states are a great labo-ratory to test new ideas,” Bucksbaumexplains. An electron with such high en-ergy can occupy a very large number ofquantum states. Combining those statesin different proportions (that is, placingthem in superposition) sculpts the shapeof the electron’s wave function. In onecombination, for example, the electron issmeared out in a ring around the atom;in another, it is localized and orbits theatom much like a planet orbiting the sun.

The basic tool for such wave functionsculpting is a strong, ultrashort laserpulse, which excites the electron from alower energy level. Through a design de-

veloped by Warren S. Warren of Prince-ton University, the researchers controlthe shape of the laser pulse using a so-called acousto-optic modulator—a crys-tal whose optical properties are gov-erned by precisely shaped sound waves.How the laser’s intensity and phase varyover the 150-femtosecond pulse deter-mines how the available excited statescombine to produce the electron’s sculpt-ed wave function.

But what shape of laser pulse is need-ed to generate a specific sculpted elec-tron wave function? In principle, thisshape can be predicted by computa-tions, but in practice one must contendwith nonideal equipment and incom-plete understanding of the physical sys-tem being controlled.

Bucksbaum’s new trick, described inthe January 21 issue of Nature, is to usefeedback to modify the shaping pulse.His group works with a gas of cesiumatoms in batches of about a millionatoms. An approximate pulse excitesthe atoms, and the researchers map theshape of the resulting wave functionwith quantum holography, a techniquethey demonstrated a year ago. In opticalholography, the three-dimensional shapeof an object is reconstructed from itshologram, a special two-dimensional in-terference pattern. In quantum hologra-phy, measurements produce data loose-ly analogous to a hologram from whichthe complete wave function of the ob-ject can be reconstructed. In accordancewith the uncertainty principle, however,each measurement disturbs the quan-tum “object,” so the “hologram” mustbe built up one pixel at a time over

many experimental runs,with thousands of identi-cally prepared atoms mea-sured on each run.

Once the physicists havemapped the resulting wavefunction, they look at thedifference between thatone and the desired one.This information is thenused to adjust the detailedshape of the laser pulseused on subsequent batch-es of atoms. Bucksbaumfound that after only twoor three iterations thisfeedback zeroed in on thedesired wave function.

Quantum control hasapplications in the bur-geoning field of quantumcomputing, in which the

News and Analysis Scientific American May 1999 35

out. “Many assertions that are madeagainst GM crops are not backed up bysound science,’’ he contends.

Both Sanders and Dunwell note thepotential benefits from genetic modifica-tion—food engineered to prevent toothdecay or to deliver vaccines. Genetic engi-neering could cut the need for pesticides.But both also admit its risks. Sanders saysthat “each crop needs examination on acase-by-case basis. It is dangerous to ex-trapolate from one to another.” Theyalso admit that genetic engineering couldbe a threat to the environment, especiallyif tests are not conducted locally. “TheEnglish countryside is not the Americanprairie,” Sanders comments.

In the next few months, the Royal So-ciety—an independent science academyestablished in 1660—will complete itsown review of Pusztai’s findings and ofits own stance on the toxicity and aller-genicity of GM foods. Only then mightresidents of Britain—and the rest of theworld—move a step closer toward un-derstanding the health threats, if any.But anyone after a definitive answerwill be disappointed—science doesn’tdeal in absolutes, and the debate willsurely rage on. —Peta Firth

PETA FIRTH, based in London, de-scribed food scares in Britain in the Jan-uary issue.

QUANTUM SCULPTING

Feedback enables researchers tocontrol an atom’s wave function

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Copyright 1999 Scientific American, Inc.