Although lifestyle and genetics obviously play an important role in whether
you pile on the pounds, the influence of the environment on the fetus may also
be have an impact, according to David Phillips of the Medical Research Council
Environmental Epidemiology Unit at the University of Southampton and James Young
of the Northwestern University Medical School in Chicago. “We’ve forgotten that
environment in early life is important,” says Phillips.

Phillips and his colleagues examined body mass index (BMI) data from 1750 men
and women who had been born in Hertfordshire between 1920 and 1930 and had lived
there all their lives. The BMI provides a measure of obesity. It is calculated
by taking a person’s weight in kilograms and dividing by the square of their
height in metres. Obese people have a larger BMI.

The researchers then classified the winters between 1920 and 1930 as either
“mild” or “cold”, and found that there was a marked increase in BMI among men
born in cold winters. As the researchers will report in the International
Journal of Obesity, the effect was also apparent for the women, though less
pronounced.

“We don’t properly understand why it occurs,” Phillips admits. He suggests
the effect could arise from the cold setting limits on how hormones behave,
possibly by influencing the thyroid gland. “Animal experiments suggest it’s
relative, not absolute temperature that causes the effect,” he adds. “So this
might explain why children of people who emigrate from hot to colder countries
are prone to get fat.”

P-glycoprotein (P-gp) stops toxic chemicals—including drugs—from
passing through the placenta, and also helps to maintain the blood-brain
barrier. In cancer, P-gp can make tumour cells resistant to drugs by pumping
them out of the cells. Alfred Schinkel and his colleagues at the Netherlands
Cancer Institute in Amsterdam bred mice lacking the gene that codes for P-gp.
When the researchers administered the anti-HIV drug saquinavir to these mice
when they were pregnant, the fetuses got five to seven times as much of the drug
as normal.

Buoyed by this success, the team administered saquinavir to normal mice,
along with cancer drugs that are known to block the action of P-gp. The foetuses
of these mice showed the same increase in saquinavir uptake as those lacking the
P-gp genes.

Schinkel hopes that giving HIV-positive pregnant women saquinavir in
combination with drugs that block P-gp could substantially reduce the risk of
passing the virus to their children. “We’ve demonstrated that we can increase
the drug loading of the mouse embryos,” he says. “Now it’s up to the clinicians
to look at patients.”

Increasing the amount of anti-HIV drugs that can be administered to a fetus
in utero would be an important advantage, according to David Back, a
pharmacologist at Liverpool University. But he advises caution in case there are
side effects. “There’s a lot we need to know about what happens when we shut
this protein down.”

żěè¶ĚĘÓƵs now know that the heartbeat is far more complex and irregular than once supposed
(żěè¶ĚĘÓƵ, 3 January 1998, p 20). The signals that
control a healthy heartbeat contain many different frequency components, and
this leads to a highly complex pattern of intervals between beats.

The gaps between heartbeats are “anti-correlated”: if the heart speeds up
over a short sequence of beats, it will slow down again over the next few beats.
More importantly, the pattern of these speed-up/slow-down events can be seen on
both short and long timescales: it looks the same over a few beats as it does
for a thousand beats. In other words, the heartbeat has a fractal pattern.

An international team led by Plamen Ivanov of the physics department at
Boston University decided to compare how the fluctuations in the interval
between beats varied between day and night. The results surprised them: during
the supposedly relaxed state of sleep, the intervals between heartbeats
fluctuated much more strongly, but were brought under control more quickly,
showing that the heart is under much closer control during sleep. “It was
totally counterintuitive,” says Ivanov.

The team initially thought the difference might come about because the body
is resting during sleep. Physical activity tends to cause changes in the
heartbeat, which would lead to more fluctuations and give the appearance that
the heart had less control. But a marked difference remained even when these
external influences were taken into account.

The researchers then compared their results with heart data from the
cosmonauts on Mir. “It was interesting to compare them with the cosmonauts who were
doing something different under different conditions,” says Luis Amaral of the
Boston team. “But we still got the same results, so this is definitely picking
up something intrinsic.”

In people with heart disease, the heart is under weaker control than in
healthy people. But the researchers found that even heart patients showed an
increased level of control when they were asleep.

The results suggest that there might be different mechanisms controlling the
heart during waking and sleep, hinting at a hitherto unsuspected role for sleep.
“I can’t tell you what sleep means,” says Harvard cardiologist Aryl Goldberger,
“but maybe a function of sleep is to readjust the heart by exercising the
˛ő˛â˛őłŮ±đłľ.”

Halitosis can be caused by various factors, from sinus trouble to poor diet,
but in 90 per cent of cases the smell is caused by volatile sulphur compounds
(VSCs). These are released when proteins are broken down by bacteria in the
mouth.

Monitoring these compounds can reveal if you have a problem, but the
detectors tend to be inaccurate and bulky—and without them it’s generally
impossible to tell whether your own breath smells. But now Alfredo Sanz-Medel, a
chemist at the University of Oviedo, Spain, says he has worked out how to make a
pocket-sized breath analyser, he reveals in the chemistry journal Analytica
Chimica Acta (vol 398, p 23).

The instruments Sanz-Medel is developing are based on a
simple reaction that can be measured optically
(see Diagram). It works by measuring the fluorescence
produced when VSCs react with a mercury compound. As the VSC concentration
increases, so does the fluorescence. By picking out telltale wavelengths in the
fluorescence, you get a measure of the “badness” of the breath.

“Other devices are not very accurate,” says Mervyn Druian of the London
Breath Centre, which specialises in treating bad breath. “You still need to be
subjective and use your own nose. It would be wonderful to have an objective
opinion,” he says.

As the technique measures a change in light intensity, fibre-optic technology
could be used to miniaturise the device for personal use. “We are in the
preliminary steps,” says Sanz-Medel, “but I am completely sure that we could
shrink the device to hand-held size.”

James Joseph of Tufts University in Boston was studying antioxidant-rich
foods like strawberries, spinach and blueberries. Antioxidants reverse some
memory loss linked to old age, probably by mopping up free radicals in the
brain.

For eight weeks, Joseph fed supplements of strawberries, spinach or
blueberries to three groups of 19-month-old rats—the equivalent of 60 to
65 years old for humans. He then assessed their memories and mobility in
standard tests.

All the rats showed improvements in memory compared with rats that were not
given antioxidant-rich food to eat. Surprisingly, the rats fed with blueberries
also had better balance and coordination in tasks such as running along a rod
(The Journal of Neuroscience, vol 19, p 8114).

Joseph suspects that the extra coordination may be due to substances in
blueberries called polyphenolics. There is evidence that some of these improve
the way neurons signal to each other and also reduce inflammation in the brain
linked to age.

Molly Wagster, from the National Institute on Aging near Washington DC, says:
“It may have implications not only for normal cognitive motor function, but also
for diseases like Alzheimer’s.”

Chemists would love to eschew the laborious approach of making and testing
one molecule at a time, in favour of reacting thousands of chemicals to make
large libraries of new compounds
(żěè¶ĚĘÓƵ, 13 July 1996, p 22).
Until now, though, this has been limited by difficulties in tracking and testing
solutions of the chemicals under scrutiny. So Alan Schwabacher, a chemist from
the University of Wisconsin in Milwaukee, has developed a novel approach that
overcomes the tracking problem.

Schwabacher’s answer is to use a long thread that has a number of different
compounds attached to it at regular intervals. The string is wrapped around a
cylinder
(see Diagram)
of known diameter. The cylinder is then marked out
lengthways into sections, and each section is reacted with a different chemical
building block. This can be done in a number of ways, but for his prototype
Schwabacher draws a pair of lines with wax—which acts as a barrier to
aqueous solutions—along the cylinder and runs a chemical between the two
lines.FIG-22042201.jpg

The thread is then wrapped around another cylinder of a different diameter
and split into sections again, but as the new cylinder is a different size, the
previous sections are mixed into the new sections. Each of these is then reacted
with a different chemical, ensuring that many permutations of reaction occur.
This process can be repeated as many times as is necessary to generate the
required structural diversity. At the end of the process the thread can be
unwrapped and analysed—the position of a molecule along the thread
determining which particular chemical building blocks have been used to make
that compound.

“It’s a totally novel technique and really quite clever,” said Nick Terrett,
editor of the online journal Combinatorial Chemistry. The Wisconsin
work will be reported in a forthcoming issue of the Journal of the American
Chemical Society.

Albert-László Barabási and his colleagues at the University of Notre Dame created a robot program to discover how documents on the Web are linked to each other. The robot looks at how many outgoing links each document has, and follows them to see where they go. From this information, the researchers created a computer model describing the Web’s connectivity.

In this week’s Nature(vol 401, p 131), Barabási and his colleagues report that their robot has found the Web to be a “small-world network”. While each point tends to connect to near neighbours, there are a few connections between distant points (żěè¶ĚĘÓƵ, 6 June 1998, p 7).

The classic example of a small-world network comes from studies of the links between co-stars in Hollywood movies, as demonstrated by the game that links any film star to the actor Kevin Bacon in less than four moves. And while the Web isn’t quite as tightly connected as Hollywood, Barabási says that in its version of the Kevin Bacon game—navigating between any two randomly chosen documents—you can always reach your target in 19 moves or less. This explains how surfing the Web can sometimes rapidly lead you to what you are looking for. Even if the Web grows tenfold, just 21 hyperlinks will take you to your goal.

Automated search engines, which rely on indexing Web pages, and matching a query to words or phrases in their text, are becoming increasingly unreliable as the Web expands (żěè¶ĚĘÓƵ, 10 July, p 11). “The problem is the amount of information available if you don’t have the human ability to understand it all,” says Oren Etzioni, chief technology officer at Go2Net in Seattle, a company developing tools to help navigate the Web.

What’s really needed is a search engine that can surf the Web in an intelligent way to exploit the links between documents and the small-world effect. That’s probably beyond the scope of current expertise in artificial intelligence, says Etzioni. So his team is working on strategies such as designing adaptive websites which automatically rearrange themselves to make popular documents more accessible, helping both surfers and search engines.