In nature, monellin is found in the berries of the West African plant
Dioscoreophyllum cumminisii, which have been used as a sweetener by local
people for hundreds of years. Because it is so profoundly sweet, monellin can be
added to food in such tiny quantities that its calorie contribution is virtually
nil.

“Monellin is a protein, so it contributes the same number of calories as
other proteins—4 kilocalories per gram,” says Kirin researcher Keiji
Kondo, who describes the production technique in the current Nature
Biotechnology (vol 14, p 453).

To produce monellin on a large scale, Kondo and his team inserted several
copies of a modified form of the gene which codes for the protein into yeast
cells. Instead of replicating natural monellin, which comprises two separate but
intertwined protein chains, the modified genes link together the two chains. The
resulting single chain protein is more stable at the high temperatures and
different pH values encountered during food preparation. Fortunately,
it is just as sweet as natural monellin, and is easier to extract from the yeast
cells.

Another natural protein of similar sweetness, thaumatin, is already used
by the food industry to mask bitterness in foods and enhance aroma and flavour.
However, the protein is expensive because it is extracted from seasonal fruit.
Monellin is the first natural protein to be successfully produced in quantities
useful to industry, irrespective of the growing season.

Richard Nelson of NutraSweet Kelco Corporation in San Diego, California,
welcomed the possible competition, but said the company was already developing a
product 7500 times sweeter than sugar called Sweetner 2000. Nelson would not
reveal whether it was synthetic or a natural product.

CHEAPER, faster computing is in prospect as researchers close in on a
“universal substrate” on which to build semiconductor chips. They hope this will
open the way to chips with circuits based on high-performance materials such as
gallium, indium and thallium, in place of silicon.

Normally, silicon is used for both the substrate—the foundations for
the chip—and the layer on its surface into which the semiconductor
circuits are etched. Because the same material is used in both layers, the
crystals in each layer align to form a strong bond between the base and the
circuit.

But silicon is not the best material for semiconductor circuits. Electrons
travel faster in compounds of gallium, indium and thallium, so transistors made
from these materials would operate faster.

The problem is that when conventional techniques are used to grow layers of
these compounds onto silicon, the patterns dictated by the spaces between their
atoms do not mesh. “The atoms don’t match up,” says Felix Ejeckam of New York’s
Cornell University, one of the team producing the universal substrates. The
resulting layers contain many imperfections, rendering them useless as
circuits.

The researchers have overcome this by literally adding a twist to the way
chip substrates are made. An extra thin layer of the base material is laid on
top of the main block, but at an angle of up to 32 degrees. These two layers are
then heated to 550 °C to fuse them together.

Because the crystal structures are at an angle, the bonds between the layers
are twisted and deformed. This makes the resulting material more flexible and
able to accommodate the crystal structures of a wide range of materials. The
researchers have tested their process using a gallium arsenide substrate. They
say it could be applied to silicon too, and that it would allow chip
manufacturers to build circuits from gallium, indium and thallium as well as
silicon on the same substrate.

This process could open up routes to a whole host of improved electronic
devices. As well as being the basis for faster electronics, compounds of gallium
and indium also give off light. This could be of use in electro-optical devices,
in which beams of laser light replace some of the wires.

NASA has pulled out of a controversial collaboration with the Russian and
French space agencies designed to study the effects of weightlessness on
monkeys. The decision follows the death of one of two monkeys sent into orbit by
the Russians four months ago.

Last December, the Russian Bion 11 capsule was launched into space and
orbited Earth for two weeks. It contained two rhesus monkeys, strapped into
their seats and with electrodes implanted into their muscles and brains. After
landing, the monkeys were anaesthetised by Russian scientists so that bone
samples could be collected. Unexpectedly, one monkey died and the other became
ill for several days (In Brief, 18 January, p 11).

An independent panel has now reviewed the project for NASA, and says that US
scientists should not take part in similar monkey experiments planned for a
follow-up mission, Bion 12, due for launch next year. The experiment has
“declared itself as risky to primates”, says Ronald Merrell, chairman of surgery
at Yale University, who led the panel. “To ignore it would be
ľ±°ů°ů±đ˛ő±č´Ç˛Ô˛őľ±˛ú±ô±đ.”

NASA says it will follow the panel’s recommendation. It is not yet clear
whether the Russians will abandon the monkey experiments, allowing NASA to
remain involved in other life science experiments planned for Bion 12.

Rhesus monkeys normally recover well from anaesthesia. The panel believes
that some undefined stress associated with space travel affected the autonomic
nervous system, which controls breathing and heart rate, making anaesthesia
unusually dangerous. This could mean that an astronaut returning to Earth in
desperate need of an operation would be in serious trouble, says Merrell.

Animal rights activists argue that NASA should never have got involved with
the project in the first place. “Blasting monkeys into space has really become
passé,” says Mary Beth Sweetland, director of research for People for the
Ethical Treatment of Animals.

But NASA officials disagree. The Bion missions were expected to yield useful
information, says Joe Bielitzki, a veterinary scientist based at NASA’s Ames
Research Center in Mountain View, California. He adds that project scientists
had no idea that the experiment would prove dangerous, as primates had never
before been anaesthetised immediately after returning from space. “This was one
that snuck up on us,” he says.

The idea of animals being manipulated to produce substances useful to humans
conjures up images of hi-tech efficiency. Yet in reality it is a pretty
hit-and-miss affair. PPL’s flock of sheep contains both high and low yielders of
the precious product, and for each transgenic sheep created there are numerous
expensive failures. Unfortunately for PPL’s shareholders, these limitations mean
that the flock can only ever supply a fraction of the ÂŁ250-million world
market for alpha-1-antitrypsin.

High hopes for cloning

But if future generations of these walking pharmaceuticals factories were
cloned from the current herd’s top producer using the technique that recently
created Dolly the sheep, the company’s share of the market would skyrocket.

In the furore which followed the announcement that Ian Wilmut, Keith Campbell
and others at the Roslin Institute and PPL Therapeutics had cloned a sheep
from an adult cell, the scientists tried to defuse public concerns that their
technique could be used to clone humans by listing the benefits that cloned
livestock could offer to medicine. They talked of a future in which herds
of identical cows supplied lavish amounts of medically important proteins, of
sheep with cystic fibrosis and other diseases which would help doctors find new
cures, and of cloned transgenic pigs that could help to meet the desperate
shortfall in human organs for transplant.

However, now that the dust has settled, many are beginning to ask whether
such a future would be as rosy as Wilmut and his colleagues would have us
believe. Now that cloning has the potential to turn a rare experimental
procedure—the creation of transgenic animals—into a profitable,
industrial process, ethicists, geneticists, agriculturists and animal welfare
activists are warning that the new technology could encourage serious abuses of
animal welfare. They point out that although the first transgenic farm animal
was created in 1985, issues such as how to minimise suffering and how to police
the production of engineered animals remain unresolved. It would be dangerous,
they say, to allow the cloning of transgenic animals without first tightening up
animal welfare regulations.

“Where transgenics and clones are concerned, it is legal and ethical free
fall,” says Andrew Kimbrell, a lawyer with the International Center for
Technical Assessment in Washington DC, which monitors the use of new
technologies. Bob Combes, a geneticist and toxicologist at the University of
Nottingham Medical School in Britain, who also works with the Fund for the
Replacement of Animals in Medical Experiments (FRAME), is calling for an
international committee to be set up to look at the welfare issues surrounding
transgenic animals. He would like to see regulations which prevent companies
from developing herds of transgenic animals until the long-term effects of each
foreign gene on the animals’ health have been fully assessed.

“There are insufficient controls,” says Combes. “People argue that these
animals are so fantastically important and the benefits so profound that they
should not have to go through the cost-benefit analysis and weigh animal
suffering and other ethical concerns in the equation. It’s the technology taking
over, and this is wrong.” Caren Broadhead, scientific officer for FRAME, says
that genetic engineers “have no idea how [transgenic] sheep could suffer”.

Current laws on transgenic animals are remarkably nonspecific. In the US,
once an animal has been engineered to produce a protein that is to be tested as
a medicine, its welfare is largely regulated by the Food and Drug Administration
(FDA) under the same laws that would govern a vat of cells. “If an animal is
used as a `bioreactor’, the animal is the source of manufacture, and the FDA
would regulate,” says biotechnologist Frank Tang of the Department of
Agriculture Animal and Plant Health Inspection Service in Riverdale,
Maryland.

In addition, there are no safeguards in the US to prevent a company from
creating large numbers of transgenic animals before it is certain that the
foreign gene will not harm the animal or its offspring. The regulations in the
European Union are just as vague.

Using transgenic animals to manufacture useful proteins still remains
inefficient. Out of 10 000 eggs injected with foreign DNA, only about three make
it to adulthood and produce the desired protein in sufficiently high quantities.
The techniques used to create Dolly offer two potential shortcuts. The
pharmaceuticals companies could create just one good transgenic animal by
conventional techniques and then clone it ad infinitum to create flocks with a
human disease such as cystic fibrosis for drug testing. Or, because Dolly’s
genetic material came from cultured cells from adult sheep, the genetic
manipulation could be done in these cells. This could allow geneticists to be
more precise about the changes they are making, enabling them to introduce and
remove genes at will.

Wilmut and his colleagues readily acknowledge that they have a few more
hurdles to clear before the two technologies—cloning and
transgenics—can be combined. The technique that created Dolly must be
repeated and made more efficient, they say. Campbell points out that just one
out of 277 egg cells successfully took up the adult DNA. And no one has yet used
the adult cloning technique in a species other than sheep.

But most agree that the financial rewards will be sufficient incentive to
overcome these barriers. “The whole reason [for] cloning is to make it a whole
lot easier to create transgenic [animals] that produce valuable
pharmaceuticals,” says physiologist and cattle rancher George Seidel of Colorado
State University in Fort Collins, who studies the possibilities for cloning
livestock. And there are plenty of successful transgenic animals that would make
suitable candidates for cloning, say scientists. According to Carl Gordon, a
biotechnology analyst for financial consultants Mehta and Isaly in New York,
genetic engineers have created no fewer than 45 transgenic goats, cows, pigs and
other livestock that secrete everything from human antithrombin III, a protein
that helps to stop blood from clotting, to human prolactin, which boosts the
immune system.

Although most welfare concerns are over the creation of transgenic animals
rather than the cloning of those animals, the new technology has itself thrown
up important issues. For instance, cloning by embryo division has a tendency to
create sheep and cows that are born up to twice the normal size. This strange
phenomenon has already led to the downfall of one cow cloning company, Granada
Genetics of Houston, Texas, because the mother cows could not deliver their
calves.

Transgenic mistakes can be unpleasant for the animal. One example is the
infamous “Beltsville pig”, which was engineered by researchers at the US
Department of Agriculture in Beltsville, Maryland, to produce human growth
hormone in an effort to stimulate growth and reduce fat on the animal. The
hormone succeeded in making the pig grow faster without extra food, but it
suffered terribly from side effects including severe bone and joint
problems.

Protected by investment

Some scientists dismiss concerns over the threat to animal welfare posed by
cloning. Robert Foote, professor emeritus of animal science at Cornell
University in Ithaca, New York, insists that cloning transgenic farm animals
would be a good thing. Producing medicinal products in milk is “an excellent
use” of animals, he says. He argues that the large amounts of money invested in
the development of transgenic animals gives them a measure of protection, as do
laws designed to ensure the humane treatment of farm animals and animals used in
experiments, such as the US Animal Welfare Act and the British Animal Scientific
Procedures Act.

But others insist that these laws are not comprehensive enough to prevent the
welfare of animals produced by genetic engineering and cloning from being
abused. Charles McCarthy, senior research fellow at the Kennedy Institute,
Georgetown University, suggests that the only way to ensure abuses are avoided
may be to have transgenic animals monitored constantly “by someone knowledgeable
about the species who will recognise signs of neurological disorders and
behavioural changes that may indicate suffering”.

FRUIT flies show a surprising similarity to humans when served a few stiff
drinks too many. They stumble around, fall over and eventually pass out. Now
researchers at the Gallo Center of the University of California, San Francisco,
are looking for genes that make fruit flies susceptible to the effects of drink.
They hope that this might highlight the genes that lead to alcoholism in
humans.

Previous studies have suggested that both genetic make-up and environmental
factors are responsible for people becoming alcoholic. “It would be safe to say
that the contribution is roughly half and half,” says Irving Gottesman of the
University of Virginia in Charlottesville, who has studied the incidence of
alcoholism in identical twins and in unrelated families.

There is also evidence that people who need to drink a relatively large
amount before becoming drunk— a characteristic that is determined
genetically to some extent—have a higher than normal chance of becoming
alcoholic. “If we can get a handle on the genes, we might be able to intervene,”
says Ulrike Heberlein, the biologist who led the research. For instance, it
might be possible to chemically switch off genes that control alcohol
tolerance.

Heberlein’s team studied the effects of alcohol on the fruit fly
Drosophila melanogaster. The genes responsible for metabolising alcohol in
the fly may be the same as in people. Heberlein genetically engineered hundreds
of flies to have short sections of DNA randomly inserted into different genes,
to disrupt their function.

Heberlein placed the mutant flies inside her “inebriometer”, a tall glass
cylinder with a miniature staircase mounted at 45 degrees. She then piped in
ethanol vapour. As the flies became steadily more sozzled, they lost their
balance, then stumbled from step to step. Finally they fell into a collection
vessel at the bottom of the inebriometer—typically after about 20
minutes.

The more susceptible flies fell out in around 13 minutes, while the most
tolerant individuals hung on for up to 32 minutes. “It’s really like
chromatography, only instead of separating things by size or electrical charge,
we’re separating by sensitivity to alcohol intoxication,” says Heberlein.

On checking the gene sequences of the different groups of flies, Heberlein
found that five previously identified genes appear to be linked to alcohol
susceptibility and tolerance. Mutations in genes called amnesiac and
rutabaga, for instance, made the flies more susceptible. Previous research
had shown that malfunction of these genes makes fruit flies lose their sense of
where they are. Heberlein presented the work this month at a conference at the
National Institutes of Health near Washington DC.

“The genes we carry have many counterparts in fruit flies,” says geneticist
Ed Lewis of the California Institute of Technology in Pasedena. “There is a high
likelihood that these genetic pathways which affect behaviour will carry over to
humans.” Gottesman says that the research is “an important piece of the puzzle”
of how alcoholism arises. But he warns that a treatment is still far away: “The
gap between what Heberlein is doing and human alcoholism is enormous.”

AN ancient Andean method of roasting coffee beans, blended with the modern
technology of magnetic resonance, is the secret of a perfect cup of coffee.

Well, that is the sales talk of two Californian companies, Puroast Coffee,
based in Woodland, and Magnetic Resonance Diagnostics of Thousand Oaks. The
“resonance roast” should start appearing on supermarket shelves around the US in
the next couple of months.

The story began high in the Venezuelan Andes, when agricultural engineer
Kerry Sachs was “blown away by the taste” of the coffee he drank there. In the
US, coffee is traditionally flash roasted at about 200 °C. But in the Andes,
beans are slow roasted. Sachs discovered that slow roasting at about 150 °C
eliminates 40 per cent of compounds known as chlorogenic acids, which are
responsible for the bitter taste of coffee. He set up Puroast to exploit the
slow roasting technique three years ago.

Then Sachs met Ronald Weinstock, the head of Magnetic Resonance Diagnostics,
which specialises in magnetic resonance instruments for medical use. Weinstock
found he could use magnetic resonance to improve the flavour of the beans.

Weinstock first analyses the magnetic resonance signature for each batch of
beans. The details of the process are still confidential but Weinstock says: “It
looks sort of like an electrocardiogram, where specific peaks represent positive
attributes we want to bring out.”

The beans are then roasted in a magnetic field which helps to realign charged
particles in the coffee. The individual signature for each batch of beans helps
Weinstock determine the best magnetic field to use. The result is a tastier
brew. The resonant roasting does not create any side effects or residues, says
Weinstock. “Outside our lab, you can’t get a smoother cup of coffee,” says Sachs
of the new product.

Ingo Schubert of the Institute of Plant Genetics and Crop Plant Research in
Gatersleben, Germany, and Oof Oud of the University of Amsterdam were trying to
find out whether a cell can keep its genetic information in a few giant
chromosomes rather than several smaller ones. They crossbred field bean plants,
selecting those that they found had more genetic material attached to one
chromosome arm than usual. After repeated rounds of selection, they ended up
with plants with unusually large chromosomes.

However, it turned out that the plants with larger chromosomes grew less well
than normal field beans. To discover why, the researchers examined cells in the
root tips under the microscope during different phases of cell division.

Normal cell division includes a phase where each chromosome in the mother
cell is copied. The pairs of chromosomes align along the cell’s centre, and then
the two members of each pair are drawn in opposite directions to either end of
the cell along “spindles”. Finally, the cell divides at the centre to form two
daughter cells.

The researchers found that if the chromosome is more than half as long as the
spindle, the trailing ends of the chromosomes will be pinched off by the new
cell walls that form as the cells divide. In that case, the genetic material
never makes it into either daughter cell and is lost, with potentially lethal
effects on the cells (Cell, vol 88, p 515). “Nowadays, when most of the
exciting news in biology comes from the molecular side, it is almost astonishing
that it is still possible to find new, basic rules by classic cytogenetic
research,” says Oud.

The researchers suggest that these limits on chromosome length apply to all
species of plants and animals. But Bill Sullivan of the University of California
in Santa Cruz says his team has seen spindles in fruit fly embryos accommodate
chromosome arms that are longer than Schubert and Oud’s rule allows. The rule
may only be true for plants, which have a cell wall that cannot easily stretch,
he suggests.

However, in 5 per cent of the cell divisions in the long-chromosome fruit
flies there are mistakes, says Sullivan. Though the individual cells may
survive, the organism as a whole may suffer. “So maybe Schubert and Oud’s rule
really applies if one is considering an evolutionary perspective,” Sullivan
says.