ÐÓ°ÉÔ­´´

Letter

I was interested in the article about skin allergies caused by henna tattoos
that contain para-phenylene diamine. Since this chemical is present in
most hair dyes, would it also cause contact dermatitis of the scalp and adverse
reactions in people who dye their hair?

It would indeed. In fact, hair-dye allergy is relatively common. The face,
ears and neck are usually affected. Ironically, one of the natural substitutes
sometimes used by people with such allergies is henna—Ed

Bugs on Venus

If Chandra Wickramasinghe is right about extraterrestrial bacteria falling on
the Earth every day
(4 August, p 11),
then the same amount of bacteria should be
falling on Venus too. There they would encounter an upper atmosphere with
conditions very similar to the upper atmosphere on Earth, so if they can survive
here, they might also survive on Venus.

A space probe designed to fly or float around in Venus’s upper atmosphere
collecting samples could provide strong evidence for or against Wickramasinghe’s
theory, and might also make the first discovery of life on another planet.

Three in one

Feedback’s concern over which of three postboxes to use
(18 August) may be
unnecessary if the collection arrangements are like those at a similar
installation near where I used to live. Here, the collector invariably turned up
with a single bag, into which the contents of all three boxes were emptied.

Ignore PCB scares, breast is always best

Congratulations on yet another thoughtfully written editorial comment
(30 June, p 3).
However, there is one issue that never seems to be aired in anything
I read about PCB contamination of human milk. In any balanced article on this
subject, some comment deserves to be made about comparable PCB contamination of
infant formulas.

Whenever the media expose the PCB contamination of human milk but not the
contamination of artificial baby milks, more mothers are influenced to take what
they see as the safer action—feed their babies with formula. Your
editorial was responsible enough to add that the babies fed breast milk in the
study you cited “still did better in neurological tests than their bottle-fed
peers”—but did not implicate formula as another source of PCB
contamination.

A group of lactation consultants in Brisbane has declined to support local
research into PCB levels in breast milk because the research will not also
examine the same issue in formula. We have seen on countless previous occasions
how the media sensationalise this type of research and also how baby-food
industries use it to further undermine breastfeeding rates.

Cloned chickens

Great. Identical chickens
(18 August, p 3 and
p 4).
That should make deadly
flu epidemics much easier to spread. Without a healthy dose of genetic diversity
all the chickens will be susceptible to the same diseases at the same time.

Letter

To answer the question in your editorial, no, the public would not be keen to
eat “battery” chickens—they are not for eating.

The majority of laying hens are kept in cages and are called battery hens.
These are not for eating, but lay eggs for the table. Chickens that are for
eating are rarely kept in cages.

Slow down the waltz

Trisha Gura says that it might be hard to test whether time passes faster for
ageing musicians
(4 August, p 32).
I suggest the test has been done, and the
results can be seen in the British names for note lengths.

When the semibreve was invented about a millennium ago, it meant what it
said—”a half of a short”. And the minim, similarly, meant “minimum
length”. With very rare exceptions, the semibreve is now the longest note and
the minim is thirty-two times the length of the shortest.

Of course, there could be more than one factor involved. Old dancers with
stiff joints prefer their favourite waltz to be less upbeat. Singing teachers
take a song through slowly to make sure it’s accurate. But I’m prepared to bet
that part of the overall slowdown comes from a genuinely subconscious dilation
of individual internal clocks.

Which conductors take the classics through at the faster rate—older or
younger?

Cattle pros and cons

I have just been looking at the ecological footprint calculator you
recommended
(11 August, p 53)
and I’m interested in the meat/vegetarian
question. If, like me you are a meat eater, you add 85 to your score, while a
vegetarian adds only 25.

I assume that this is calculated on European farming practices, as sheep and
cattle farming in New Zealand are far less damaging to the environment than
market gardens and grain growing. As far as non-organic agriculture goes, our
large grain fields and market gardens are deserts devoted to one species,
heavily sprayed and fertilised, while most sheep and cattle stations here have a
mix of native and introduced plant species, provide habitat for native fauna,
and are far less dependent on chemicals. Our stocking rates are low and animals
are fed grass rather than grain.

Is the ecological footprint different for those who eat non-intensive,
grass-fed meat?

Letter

While it may be correct to suggest that fuel crops could be energy wasters,
I’m amazed that agricultural scientist David Pimentel says the land would be
better used to supply cattle feed
(18 August, p 17).

Approximately 90 per cent of the energy mammals get from food is used to
maintain body temperature, so conversion of fodder to muscle is far from
efficient. Also, consider the amount of the carcass that is inedible and the
energy costs of transporting and preparing the meat, not to mention the
potential problems with methane production in the cows’ intestines. I would be
astounded if meat production was “greener” than ethanol production.

Glucose booster

Your editorial and article about drugs in sport
(11 August, p 3 and
p 4)
raised the possibility of the glucose insulin clamp technique being used to
increase muscle glycogen content and improve athletic performance, but presented
no data. Indeed the original article by Peter Sonksen referred only to “informed
street talk”.

We found the use of a two-hour hyperglycaemic, hyperinsulinaemic clamp
resulted in a significant net storage of glucose (assumed to go into muscle
glycogen) in cyclists who continued to consume their normal diet. This improved
athletic performance (a 10-mile time trial following 90 minutes of moderately
severe exercise) by 3 per cent. This figure is almost identical to the
improvement seen in endurance exercise using the well-known technique of
“carbohydrate loading”, when large quantities of carbohydrate are eaten
following exercise to exhaustion.

The clamp technique however is not without its hazards. Glucose and insulin
lead to profound falls in plasma potassium, which produces heart irregularities
and may result in a cardiac arrest. It does need very close monitoring.

We were interested in the technique’s use as a possible means of improving
recovery from surgery or intensive care where “insulin resistance” is observed
and is very similar to that seen during exercise. It is now well established
that preoperative carbohydrate “priming”, as well as insulin clamping
perioperatively, can improve the body’s ability to use glucose, improving muscle
strength and the patient’s ability to get better after an operation. Athletes
are not the only ones who need a helping hand.

Always right or wrong

With reference to David Deutsch’s ideas, Rex Newsome writes “. . . if the
many-worlds theory is right, there must be physically possible worlds in which
he is wrong”
(11 August, p 53).
Not so. There are only two possibilities: either
the many-worlds theory is false or it is true. If it is false then it is false
in all worlds. If it is true then it is true in all worlds. The error arises
from confusion between possible and actual worlds. The worlds in the many-worlds
theory are actual, not (merely) possible, and cannot include any in which the
theory is false.

On a separate matter, it is misleading to use the title “Look who’s talking”
on an article about artificial intelligence
(11 August, p 34).
To refer to a computer program as if it were a sentient being is anthropomorphism.
Hal promises to enhance human-machine communication. However, it no more
“experiences” or “understands” than your humble pocket calculator knows what
it’s doing.

Yorick Wilks, who believes that such talking machines raise an ethical
problem, shares this anthropomorphism. “They won’t want to be switched off,” he
says. What a superstitious attitude towards something that is “little more than
a collection of general learning algorithms on a laptop computer”.

Chemical memory

In a recent issue you report the discovery of long-range signalling between
biological molecules in solution
(14 July, p 16).

Marvin Minsky describes consciousness as “short-term memory”. Could such
signals enhance memory, and so consciousness, by recording the passage of
neurotransmitters between neurons—which would then influence subsequent
discharge of neurotransmitters?

Tuneful proteins

I am writing to correct New ÐÓ°ÉÔ­´´’s inaccurate description of
“molecular music” in two recent pieces
(10 February, p 21, and
28 July, p 30).
Molecular music is music derived from protein structural data. Both articles
state that for each amino acid “each atom type and position gets a
characteristic sound, which varies in pitch, volume and rhythm”.

This is wrong. First, molecular music translates data relating to amino acids
only (not atom types) and, secondly, the statement implies a subjective “musical
labelling” of amino acids. Molecular music may be more accurately described as
the musical mapping of amino acids in a protein structure. It translates the
three-dimensional positions of amino acids into note sequences by a process of
mathematical filtering and musical mapping.

In this way, patterns in protein structure (such as helices and parallel
chains) emerge as recognisable musical note patterns from the 3D structural
data. The musicality of such sequences is incidental, although not surprising,
given that it is the repetitive patterns in music that we often find most
pleasing and memorable.

Hear it for henna

I am very concerned about the representation of henna in your recent article
(18 August, p 16).
While for the most part the article is very factual, the
first part is devoted to scaring people away from a beautiful, traditional art
form because in some cases it has been perverted.

Pure henna has a negligible allergic rate, and many reputable artists are now
banding together to stomp out the addition of chemicals used to darken the henna
tattoo. As an artistic community, we appreciate every published mention of
exactly how horrible these chemicals are. We just want to make clear where the
danger lies.