ScienceWeek

SCIENCE-WEEK

A Weekly Email Digest of the News of Science

A journal devoted to the improvement of communication
between the scientific disciplines, and between scientists,
science educators, and science policy-makers.

October 27, 2000 -- Vol. 4 Number 43

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For the real amazement, if you wish to be amazed, is this
process: You start out as a single cell derived from the coupling
of a sperm and an egg; this divides in two, then four, then
eight, and so on, and at a certain stage there emerges a single
cell which has as all its progeny the human brain. The mere
existence of such a cell should be one of the great astonishments
of the Earth. People ought to be walking around all day, all
through their waking hours calling to each other in endless
wonderment, talking of nothing except that cell.
-- Lewis Thomas (1913-1993)

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=-=-=-=-=-=-=-=-=
Section 1
=-=-=-=-=-=-=-=-=

Contents of this Issue (Full reports in Section 2):

1. ASTROPHYSICS:
DISCOVERY OF ISOLATED GIANT PLANETS
Astronomers report the discovery by optical and near-infrared
imaging of an extremely red, low-luminosity population of
isolated objects in the young nearby stellar cluster around the
multiple massive star sigma-Orionis. Like the planets of our
Solar System, these objects are unable to sustain stable nuclear
burning in their interiors, but in contrast, they are apparently
not bound to stars. This new type of isolated giant planet, which
apparently forms on time scales of less than a few million years,
offers a challenge to our understanding of the formation
processes of planetary mass objects. (Science 6 Oct 00 290:103)

2. PLANETARY SCIENCE:
RECOVERY AND ANALYSIS OF A RARE TYPE OF METEORITE
On 18 January 2000, an exceptionally bright fireball was
witnessed in dawn twilight throughout the Yukon and Northwest
Territories, northern British Columbia, and parts of Alaska.
Hundreds of fragments of the object, now known as the "Tagish
Lake meteorite", have been recovered, and the meteorite is
evidently a new type of carbonaceous chondrite, and of apparent
great importance. Fragments recovered range in mass from
fractions of a kilogram to several kilograms, and it is estimated
that the original pre-atmospheric mass of the meteoroid was
approximately 200,000 kilograms, corresponding to an object 4 to
6 meters in diameter. (Science 13 Oct 00 290:283)

3. EARTH SCIENCES: ON CLIMATE EXTREMES
Most considerations of near-future climate changes have focused
on average values of various climate parameters. But expected
extreme values of these parameters are of considerable
importance, since climate extremes (heavy rainfall, drought,
highest and lowest temperatures, etc.) have enormous sudden
impacts on society and ecology. Analysis of climate models
indicates changes in extreme events for future climates, such as
increases in extreme high temperatures, decreases in extreme low
temperatures, and increases in intense precipitation events. In
addition, the societal infrastructure is becoming more sensitive
to weather and climate extremes, which would be exacerbated by
climate change. (Science 22 Sep 00 289:2068)

4. MOLECULAR BIOLOGY: ON RIBOSOMES
The dogma that nucleic acids are the repository of information
and that proteins catalyze chemical reactions was overturned only
15 years ago by the demonstration of catalytic RNAs (ribozymes).
Despite increasing support for the "RNA world hypothesis", which
sees RNA-based life forms as the progenitors of modern biological
cells, most biologists did not seriously consider the possibility
that RNA could be playing more than a minor part in reactions
such as protein synthesis. But it has turned out that in the
ribosome most of the important functional work is done by RNA,
and that the ribosome is "one colossal RNA enzyme".
(Nature 21 Sep 00 407:306)

5. DEMOGRAPHY:
INCREASE OF MAXIMUM LIFE-SPAN IN SWEDEN 1861-1999
An demographic analysis reveals that the maximum age at death in
Sweden has risen from approximately 101 years during the 1860s to
approximately 108 years during the 1990s, with the rate of
increase 0.44 years per decade before 1969 and 1.11 years per
decade after that date. The researchers suggest their analysis
refutes the common assertion that the human life-span is fixed
and unchanging over time. Although the maximum life-span has
increased much more slowly than the average life-span, the entire
distribution of ages at death has been shifting upward for more
than a century in Sweden and, presumably, in other countries as
well. (Science 29 Sep 00 289:2366)

6. MEDICAL BIOLOGY:
ON PROSTATE CANCER
In the US, adenocarcinoma of the prostate is the most common
malignancy in men older than 50 years, the incidence increasing
with each decade of life, with approximately 210,000 new cases
occur in the US each year. The incidence of prostate cancer in
the US is significantly higher than in most other countries,
particularly Asian countries, even though the incidence of
histological pre-neoplastic lesions has been reported to be
similar worldwide. Dietary and environmental factors have
therefore been presumed to play a key role in prostate
carcinogenesis, similar to their role in other common epithelial
cancers. (Genes & Development 1 Oct 00 14:2410)

7. IN FOCUS: ON THE EVOLUTION OF THE NERVOUS SYSTEM

8. FROM THE SCIENCEWEEK ARCHIVE:
A CRITICISM OF US ACADEMIC RESEARCH IN BIOLOGY


=-=-=-=-=-=-=-=-=
Section 2
=-=-=-=-=-=-=-=-=

1. ASTROPHYSICS:
DISCOVERY OF ISOLATED GIANT PLANETS
In general, brown dwarf stars are believed to be formed by the
contraction of a lump of gas with a mass too small for nuclear
reactions to begin in the core. Such a star has a relatively
short-lived luminosity (approximately 100 million years) as the
result of conversion of gravitational energy to radiation. The
surface temperature of a brown dwarf is below 2500 degrees
kelvin. As recently as 1994, brown dwarfs were "theoretical"
stars, with no brown dwarfs considered to be unambiguously
identified. A number of such stars have now been located. In
contrast, the term "giant planet" refers to astronomical objects
of Jupiter-size or greater, but still with a mass to small for
core nuclear reactions to be generated. There is presently some
disagreement in the astronomical community concerning the
categorization of brown dwarfs vs. giant planets, whether to base
the distinction on details of formation or on the mass limit for
nuclear burning (see below). Dozens of apparent extra-solar giant
planets have been discovered, and until now all of them have been
found to be orbiting specific stars.
... ... M.R. Zapatero Osorio et al (7 authors at 6 installations,
ES, US, DE) now report the discovery of isolated apparent giant
planets, the authors making the following points:
     1) Recent deep photometric and spectroscopic searches have
revealed that brown dwarfs, objects unable to begin a stable
fusion of hydrogen (but which do burn deuterium), are very common
in star-forming regions, galactic clusters, and the neighborhood
of our Solar System. Young brown dwarfs in stellar clusters have
been unambiguously identified, with masses ranging from the
hydrogen-burning limit (75 Jupiter masses) (1 Solar mass = 1047
Jupiter masses) down to the deuterium-burning threshold
(approximately 13 Jupiter masses). This minimum mass limit has
been recently proposed to set the boundary between brown dwarfs
and giant planets: while brown dwarfs are capable of fusing
deuterium into Helium-3, one of the lowest threshold energy
nuclear reactions, so-called "planets" never sustain any nuclear
burning in their interiors. This nuclear criterion applied to
define the term "planet" is independent of any criteria based on
any poorly known (at present) formation processes of substellar
objects.
     2) The authors report the discovery by optical and near-
infrared imaging of an extremely red, low-luminosity population
of isolated objects in the young nearby stellar cluster around
the multiple massive star sigma-Orionis. The authors suggest the
proximity (352 parsecs), youth (1 million to 5 million years),
and low spectral corruption (low "internal extinction") make this
cluster an ideal site to explore the substellar domain from the
hydrogen mass limit down to a few Jupiter masses. The authors
report that optical and near-infrared low-resolution spectroscopy
of 3 of these objects confirms the very cool spectral energy
distribution (atmospheric effective temperatures of 1700 to 2200
degrees kelvin) expected for cluster members with masses in the
range 5 to 15 times that of Jupiter. Like the planets of our
Solar System, these objects are unable to sustain stable nuclear
burning in their interiors, but in contrast, they are apparently
not bound to stars. The authors state: "This new kind of isolated
giant planet, which apparently forms on time scales of less than
a few million years, offers a challenge to our understanding of
the formation processes of planetary mass objects."
-----------
M.R. Zapatero Osorio et al: Discovery of young, isolated
planetary mass objects in the sigma-Orionis star cluster.
(Science 6 Oct 00 290:103)
QY: M.R. Zapatero Osorio: mosorio@ll.iac.es
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 27Oct00
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
GIANT PLANETS VS. BROWN DWARFS
Filipe D. Santos (Centro de Fisica da Universidade de Lisboa, PT)
presents a short review of current ideas concerning giant
extrasolar planets and *brown dwarf stars. The author makes the
following points: 1) The recent discoveries of planets orbiting
nearby Sun-like stars have revealed that planetary systems can be
surprisingly diverse. The initial discovery in 1995 of the planet
around the star 51 Pegasi was a surprise because it is apparently
a planet with mass about that of Jupiter (at least 0.44 Jupiter-
mass) and an orbital period of only 4.2 days, which implies that
the planet is 20 times closer to its star than Earth is to the
sun. 2) Seven additional planets around solar-type stars have
since been discovered, with Jupiter-mass values ranging from 0.44
to 6.84. 3) Two critical questions are, a) Where should we set
the dividing line that distinguishes massive planets from brown
dwarfs? and, b) What are the mechanisms leading to the formation
of massive planets and brown dwarfs? 4) Brown dwarfs are expected
to have masses smaller than the hydrogen-burning limit of
approximately 0.075 solar-mass (approximately 75 Jupiter-mass),
but probably larger than the deuterium-burning limit of 0.013
solar-mass (approximately 13 Jupiter-mass). 5) Like the companion
massive planets mentioned, several companion brown dwarfs to
solar-type stars have also been identified. One method of
investigating brown dwarfs involves *astrometric measurements,
and in all cases of brown dwarfs investigated by the astrometric
method, the masses are above or very close to the hydrogen-
burning limit. The extant data thus suggest that the distribution
of mass of brown dwarfs does not extend to masses as small as
giant planets. Also, the new measurements indicate that brown
dwarfs orbiting solar-type stars are very rare. 6) The discovery
of Jupiter-mass planets with orbits very close to their stars
poses a considerable problem, because it is difficult to
understand how such planets could form in place. (Five known
Jupiter-mass planets have orbital radii smaller than the distance
from Mercury to the Sun.) The suggestion has been made that these
planets formed at larger distances and migrated inward, but the
proposed migration mechanisms are not yet empirically
distinguishable. The author concludes: "Clearly the discovery of
planetary systems outside our solar system has opened a Pandora's
box of startling phenomena and new questions."
QY: Filipe D. Santos 
(Science 17 Jul 98 281:359) (Science-Week 31 Jul 98)
-------------------
Related Background:
... ... *brown dwarf stars: See main report.
... ... *astrometric measurements: This method of detection
infers the presence of a companion to a star by measuring the
position of the star as it orbits the center of mass of the
entire system. From the orbital inclination, the real mass of the
companion can be derived.
-------------------
Related Background:
ASTROMETRIC SIGNATURES OF GIANT PLANET FORMATION
The discoveries during the past two years of giant planets
orbiting nearby solar-type stars has raised again the question of
how these planets are formed. Two different models have been
proposed. The gravitational instability model involves formation
of planets directly from the gas in the accretion disk around the
young star. The alternative model is the core-accretion model, in
which rocky cores of about 10 Earth masses form first, with that
followed by hydrodynamical accretion of gas to form the massive
envelopes of the giant planets. ... ... Alan P. Boss (Carnegie
Institution of Washington, US) now proposes, on the basis of
calculations, that these two processes have very different
astrometric signatures, and that it should be observationally
possible to distinguish between them. Planets that form through
gravitational instabilities do so rapidly, so that within just a
few hundred years of the onset of the instability the nascent
planet is making the young stellar object wobble in its orbit.
This can be seen in the youngest stellar objects, with ages as
little as 0.1 million years. If planets form by core accretion,
an observable wobble will not be visible for 10-20 million years.
The author suggests that observations of a suitable ensemble of
optically visible young stellar objects (such as those in the
Taurus molecular cloud) over a period of several decades should
be able to determine which of the two processes is responsible
for the formation of giant planets.
-----------
QY: Alan P. Boss: boss@dtm.ciw.edu
(Nature 14 May 98 393:141) (ScienceWeek 5 Jun 98)
For more information: http://scienceweek.com/swfr.htm

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2. PLANETARY SCIENCE:
RECOVERY AND ANALYSIS OF A RARE TYPE OF METEORITE
     The term "meteor" has a loose usage, but generally refers
only to the streak of light in the sky produced by a small object
entering Earth's atmosphere. When in space, outside the
atmosphere, the object is called a "meteoroid", and if parts of
the object survive the plunge through the atmosphere and reach
the surface of the Earth, those parts are called "meteorites".
Only a few thousand meteorites have been retrieved immediately
after a fall.
     "Stony" meteorites (aerolites) are meteorites formed solely
of rock-forming silicates, and chondrites are a type of stony
meteorite consisting of an agglomeration of millimeter-sized
globules (chondrules) that are thought to be unchanged since the
original condensation out of the nebula from which the Sun and
Solar System formed. A carbonaceous chondrite is a chondritic
meteorite that contains a relatively large amount of carbon, with
a resultant dark appearance. Most meteorites are believed to
derive from asteroids, but important questions concerning their
origin are still unresolved.
     There are various types of carbonaceous chondrites, and CI
carbonaceous chondrites are of special significance because they
have nearly the same composition, ignoring hydrogen and helium,
as the *photosphere of the Sun, and because they have evidently
experienced only little thermal processing since the earliest
history of the solar system. It is believed that CI carbonaceous
chondrites probably derive from so-called "C asteroids", which
are relatively common in the outer parts of the asteroid belt.
     In contrast to other stony meteorites, C asteroid materials
are structurally weak and CI carbonaceous chondrite meteorites
are rare. Such meteorites, in fact, are physically akin to dried
mud, and they either disintegrate or dissolve easily once they
reach the surface of the Earth.
     On 18 January 2000, an exceptionally bright fireball was
witnessed in dawn twilight throughout the Yukon and Northwest
Territories, northern British Columbia, and parts of Alaska.
Hundreds of fragments of the object, now known as the "Tagish
Lake meteorite", have been recovered, and the meteorite is
evidently a new type of carbonaceous chondrite, and of apparent
great importance. Fragments recovered range in mass from
fractions of a kilogram to several kilograms, and it is estimated
that the original pre-atmospheric mass of the meteoroid was
approximately 200,000 kilograms, corresponding to an object 4 to
6 meters in diameter.
... ... Jeffrey N. Grossman (Geological Survey, US) presents a
commentary on the first report of analysis of the Tagish Lake
meteorite (P.G. Brown et al: Science 13 Oct 00 290:320), the
author making the following points:
     1) The author points out that most meteorites that reach the
Earth's surface are pieces of asteroids and are older than any
native rock on our planet. Meteorites thus provide a glimpse into
the first few tens of millions of years of the history of the
Solar System. The most primitive meteorites are made of materials
that contain the clearest accounts of the most ancient events in
the Solar System, mixed with exotic "presolar" grains that formed
in other stars before the beginning of our 4.56-billion-year
local history. Among these primitive meteorites are the CI
carbonaceous chondrites.
     2) A series of lucky events are necessary to get a
reasonable amount of CI carbonaceous chondrite material to the
laboratory in pristine condition. Over the last two centuries,
only 5 of the nearly 1000 meteorites recovered from witnessed
falls have been CI chondrites. Two 20th century falls in France,
a 1911 fall in India, and a 1938 fall in Tanzania yielded a total
of approximately 20 kilograms of material, but time and
antiquated curation techniques have severely degraded these
samples, especially for the analysis of low-temperature and
organic components. In 1965, a CI chondrite fall was accompanied
by a spectacular fireball over British Columbia, but only
approximately 1 gram of material was recovered. The search for
already fallen meteorites is even less promising. Of the
approximately 20,000 meteorites found on Earth whose fall was not
witnessed, only two fragments of CI chondrites, totaling no more
than approximately 15 grams, have been identified, both in the
Antarctic.
     2) The recovery of the Tagish Lake meteorite is therefore of
particular importance. The meteorite fell on 18 January 2000 and
was recovered 7 to 8 days later. P.G. Brown et al demonstrate
that the meteorite is closely related to the CI chondrites and
they speculate that it may in some respects be even more
primitive. Most of the Tagish Lake specimens have not been warmed
above 0 degrees centigrade since they hit the frozen lake, and
this is almost certainly the first time any fresh meteorite has
received such treatment. The low temperatures have apparently
hindered the loss of volatiles: the stones give off a strong
sulfur odor when warmed to room temperature, as some of the
volatile components evaporate. In addition to the good luck of
recovering such a large pristine mass of a primitive meteorite,
the fall of the Tagish Lake meteorite was widely enough witnessed
to allow the calculation of an orbit for the original meteoroid,
which has never before been done for a carbonaceous chondrite.
     3) The author concludes: "It seems likely that the Tagish
Lake meteorite will be the most important recovered fall since
the Allende (Mexico) and Murchison (Australia) events, both in
1969, touched off a revolution in our understanding of meteorites
and what they tell us about the early Solar System."
-----------
Jeffrey N. Grossman: A meteorite falls on ice.
(Science 13 Oct 00 290:283)
QY: Jeffrey N. Grossman: jgrossman@usgs.gov
-----------
Text Notes:
... ... *photosphere: In general, the visible surface of a star
(in this case the Sun), from which most of its energy is emitted
in the form of visible and infrared radiation.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 27Oct00
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
A WORKSHOP ON CHONDRITE METEORITES
Chondrite meteorites are characterized by the presence of
chondrules, small spherical inclusions of glassy rock that can be
seen easily with the naked eye if the meteorite is cut and one of
the cut faces polished. Carbonaceous chondrites contain both
chondrules and volatiles, and since the presence of the volatiles
is believed to indicate an origin which did not involve heat, the
carbonaceous chondrites are considered the least altered remains
of the solar nebula from which the planets are believed to have
formed. In general, the study of chondrites is one of the
important keys to the history of our solar system. One of the
more interesting carbonaceous chondrites is the meteorite called
Allende, which fell on 8 February 1969 at Pueblito de Allende in
norther Mexico, and which scattered 5 metric tons of material
over an area 48 kilometers long by 7 kilometers wide. Some 100
meteorite specialists met recently at a workshop in Hawaii (the
Workshop of the Nebular and Parent Body Alteration of Chondritic
Materials, 17-19 July, Maui, HI US), with a major discussion of
the present divergent views concerning the origin and formation
of chondrites and how these views are related to current models
of the early history of the solar system. The challenge for these
meteorite specialists is to attempt to understand the complex
record produced 4.56 billion years ago (a consensus date derived
from isotope data), as evidenced in the microstructure of
chondrites, when the meteorite formation events have no apparent
terrestrial analog. The Allende meteorite was an important focus
at this meeting, a meteorite that has "already stimulated and
intrigued many planetary scientists for the last 25 years".
QY: Adrian Brearley  (Science 3 Oct 1997)
-------------------
Related Background:
A NEW THEORY FOR THE FORMATION OF CHONDRITE METEORITES
Chondrites are a type of stony meteorite consisting of an
agglomeration of millimeter-sized globules (chondrules) that are
thought to be unchanged since the original condensation out of
the nebula from which the sun and solar system formed. During the
past century, specialists in meteorites have puzzled over the
unusual composition of these meteorites: dust, round rocks that
were apparently flash-melted and resolidified, and the remains of
short-lived radioactive isotopes. At a recent meeting of the
American Astronomical Society in Winston-Salem (NC US), Frank Shu
et al (University of California Berkeley, US; Academia Sinica,
TW; New York University, US) presented a well-received theory
that chondrites were produced by the solar flares and jets that
the Hubble Space Telescope has apparently indicated exist at the
outer edges of young stars. Not everyone agrees with this idea,
but astronomers seem to think it is the best hypothesis to date.
(Science 20 June) (ScienceWeek 26 Jun 97)
For more information: http://scienceweek.com/swfr.htm

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

3. EARTH SCIENCES: ON CLIMATE EXTREMES
Most considerations of near-future climate changes have focused
on average values of various climate parameters. But expected
extreme values of these parameters are of considerable
importance, since climate extremes (heavy rainfall, drought,
highest and lowest temperatures, etc.) have enormous sudden
impacts on society and ecology.
... ... D.R. Easterling et al (6 authors at 4 installations, US)
present a review of prospects for near-future climate extremes,
the authors making the following points:
     1) There is general agreement that changes in the frequency
or intensity of extreme weather and climate events would have
profound impacts on both human society and the natural
environment. Recent years have seen a number of weather events
cause large losses of life as well as a tremendous increase in
economic losses from weather hazards. In 1998, Hurricane Mitch
caused over 10,000 deaths in Central America, and more recently,
major flooding events with large loss of life have occurred in
both Venezuela and Mozambique. In the US since 1987, more than
360 weather events each produced losses in excess of $5 million,
with several record-setting catastrophes. These include the
midwest drought of 1988-1989 ($39 billion), Hurricane Andrew in
South Florida in 1992 ($30 billion), and the midwest flood of
1993 ($19 billion). These life and property losses helped raise
alarm over the possibility that the recent increases were due to
a shifting climate. The important question is clear: Are these
increases merely a function of decadal fluctuations, or are they
indicative of longer term trends related to anthropogenic-induced
climate change?
     2) It is apparent from the observed record that there has
been an increase in the global mean temperature of approximately
0.6 degrees centigrade since the start of the 20th century, and
that this increase is associated with a stronger warming in daily
minimum temperatures than in maximums, leading to a reduction in
the diurnal temperature range. Land surface precipitation has
also increased over the same period in the mid- to high
latitudes, but shows a decrease in the tropics and subtropics.
Given these changes, it is expected that there would also be
changes in what are now considered extreme events. Therefore, if
there are indeed identifiable trends in certain extreme climate
events, such as extremes in temperature or precipitation, it
would add to the body of evidence that there is a discernible
human effect on the climate, and potentially have important
consequences for society and natural systems.
     3) The authors suggest that analysis of climate models
indicates changes in extreme events for future climates, such as
increases in extreme high temperatures, decreases in extreme low
temperatures, and increases in intense precipitation events. In
addition, the societal infrastructure is becoming more sensitive
to weather and climate extremes, which would be exacerbated by
climate change. For wild plants and animals, climate-induced
extinctions, distributional and *phenological changes, and range
shifts of species are being documented at an increasing rate.
Several apparently gradual biological changes are linked to
responses to extreme weather and climate events.
-----------
D.R. Easterling et al: Climate extremes: Observations, modeling,
and impacts.
(Science 22 Sep 00 289:2068)
QY: David R. Easterling: david.r.easterling@noaa.gov
-----------
Text Notes:
... ... *phenological changes: The term "phenology" refers to the
study of periodicity phenomena in plants, e.g., timing of
flowering in relation to climate.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 27Oct00
For more information: http://scienceweek.com/swfr.htm

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

4. MOLECULAR BIOLOGY:
ON RIBOSOMES
A ribosome is a large ribonucleoprotein particle which is present
in many copies in all biological cells and which is the site of
protein synthesis. All ribosomes consist of 2 subunits of unequal
size, called the "large" and "small" subunits, and the size and
composition of these two subunits differs between *prokaryotic
and *eukaryotic cells (although the overall structure is
similar). Ribosomes from the common bacterium Escherichia coli
have a *sedimentation coefficient of 70s, a total *relative
molecular mass of 2.7 x 10^(6), and a diameter of approximately
200 angstroms. E. coli ribosomes are composed of a large subunit
of 50s and a small subunit of 30s. The 50s subunit consists of 34
different proteins ("ribosomal proteins") and 2 types of
ribosomal RNA. The 30s subunit contains 21 ribosomal proteins and
a 16s RNA. Each ribosomal subunit has been shown to self-assemble
in vitro from its constituent proteins and RNA.
... ... James R. Williamson (Scripps Research Institute, US)
presents a commentary on recent ribosome research, the author
making the following points:
     1) The structure of the small subunit of a bacterial
ribosome has now been solved at atomic resolution (B.T. Wimberly
et al: Nature 21 Sep 00 407:327; A.P. Carter et al: Nature 21 Sep
00 407:340). The ribosome is a fundamental cellular component
which synthesizes all of the proteins in the cell, using
*messenger RNA (mRNA) as the template. The ribosome acts in
concert with a variety of smaller entities that help to
orchestrate the process, but the two main functions involve the
ribosome itself: decoding the genetic code in the messenger RNA,
and catalyzing the formation of chemical bonds between amino
acids to result in polypeptide chains of proteins.
     2) The 30s subunit has a very different architecture than of
its 50s partner. In the 30s subunit, clear domain boundaries are
evident in crystallographic data, and potentially flexible
regions can be seen in cryo-electron microscope reconstruction.
Large movements, on the scale of tens of angstroms, must occur on
the 30s subunit during translocation of the messenger RNA from
one *codon to the next. In contrast, the 50s subunit is
monolithic, its components being intricately folded and packed
into a rigid structure. These two structurally unlike subunits
work together to carry out, in all biological cells, one of the
most intricate of functions.
     3) The author points out that it is perhaps not widely
appreciated that approximately two-thirds of the mass of the
ribosome is composed of RNA. With atomic knowledge of the 30s and
50s structures and how they assemble into the overall 70s
ribosome, one point stands out: the most essential functions of
the ribosome are carried out by RNA.
     4) The dogma that nucleic acids are the repository of
information and that proteins catalyze chemical reactions was
overturned only 15 years ago by the demonstration of catalytic
RNAs (ribozymes). Despite increasing support for the "RNA world
hypothesis", which sees RNA-based life forms as the progenitors
of modern biological cells, most biologists did not seriously
consider the possibility that RNA could be playing more than a
minor part in reactions such as protein synthesis. But it has
turned out that in the ribosome most of the important functional
work is done by RNA. The author concludes: "The ribosome is one
colossal RNA enzyme."
-----------
James R. Williamson: Small subunit, big science.
(Nature 21 Sep 00 407:306)
QY: James R. Williamson: jrwill@scripps.edu
-----------
Text Notes:
... ... *prokaryotic: The term "prokaryotes" refers to biological
cells without internal membrane-bound organelles such as a
nucleus.
... ... *eukaryotic: The term "eukaryotes" refers to biological
cells (or organisms consisting of such cells) with internal
membrane-bound organelles such as a nucleus.
... ... *sedimentation coefficient: The sedimentation coefficient
is essentially the rate of sedimentation of a particle in an
ultracentrifuge or other system. The sedimentation coefficients
of macromolecular and cellular particles are often expressed as
Svedberg units, after Theodor Svedberg (1884-1971), the inventor
of the ultracentrifuge, who received the Nobel Prize in Chemistry
in 1926 for his work on disperse systems.
... ... *relative molecular mass: The unit "relative molecular
mass", often used in biochemistry and denoted by M(subr), is
essentially synonymous with molecular weight, and is the ratio of
the mass of a molecule to the atomic mass constant, which is
taken as one-twelfth of the mass of the nuclide (sup12)C. The
relative molecular mass is a dimensionless number, the magnitude
of which is equivalent to the molecular mass in daltons: A
relative molecular mass of 10,000 is equivalent to 10
kilodaltons.
... ... *messenger RNA (mRNA): The ribonucleic acid molecule
transcribed from DNA that carries the coded information
specifying the sequence of amino acids in a protein.
... ... *codon: A "codon" is the elemental genetic coding unit,
a triplet of 3 consecutive nucleotides that define a specific
amino acid.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 27Oct00
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
MOLECULAR BIOLOGY: ON THE WORKINGS OF THE RIBOSOME
A ribosome (not to be confused with riboZYME) is a small particle
found in all living cells, a complex of various ribonucleic acid
component subunits and proteins that functions as the site of
protein synthesis. Each ribosome particle is approximately 30
nanometers in diameter, and each particle essentially functions
as a translating unit, translating RNA sequence code into a
protein polymer sequence. ... ... Joachim Frank (State University
of New York Albany, US) presents a review of current
understanding of ribosome function and structure, the author
making the following points: 1) Although it is important to know
the structure of the ribosome at atomic resolutions, this goal is
still quite remote, since even one of the simplest ribosomes,
that of the bacterium Escherichia coli, is made up of more than
50 components, mostly proteins plus 3 large RNA molecules.
Ribosomes of higher organisms are even more complex and have more
components. 2) It is now believed that all important functions of
the ribosome actively involve the ribosomal RNAs as major
players, whereas the ribosomal proteins act either as structural
"glue" or as "helpers" that promote specific binding reactions.
This represents a complete reversal of the long-held view that
the proteins of the ribosome perform all the important tasks. 3)
The translation from the nucleotides of messenger RNA (mRNA) to
the amino acids in the protein polypeptide chain is accomplished
at the ribosome with the help of an adaptor molecule called
"transfer RNA" (tRNA). The molecule tRNA exists in 20 varieties,
each variety specifically designed to accommodate only one of the
20 amino acids at one end of the tRNA molecule, and each tRNA
molecule also carries a specific *anticodon at the other end of
the molecule that recognizes only the *codon on mRNA specifying
that particular amino acid. Each tRNA molecule thus acts as a
physical code-link between an mRNA codon for an amino acid and
that specific amino acid, the assembly of the protein polymer
involving the sequential selection of amino acids from the
ambient amino acid pool. 4) The author reviews an application of
the technique of cryo-electron microscopy to the determination of
ribosome structure, the application involving methods of "single-
particle reconstruction" developed by the author. Cryo-electron
microscopy provides a means to image macromolecules in a "close-
to-native" conformation by freezing the molecules rapidly in
liquid ethane at -196 degrees Celsius. The technique was first
developed in the 1970s by Glaeser et al, and then perfected early
in the 1980s by Dubochet et al. The method of single-particle
reconstruction essentially involves the idea that in principle
the 3-dimensional geometry of a macromolecule can be
reconstructed from its projections on a 2-dimensional surface,
provided the molecule occurs in a range of orientations and
provided these orientations are known. The author reviews in
detail what is known concerning the workings of the ribosome
during protein synthesis as amplified by recent data involving
the application of cryo-electron microscopy coupled with
techniques of single-particle geometric reconstruction.
-----------
QY: Joachim Frank, Wadsworth Center, Howard Hughes Medical
Institute, PO Box 509, Albany, NY 12201-0509 US.
(American Scientist Sep/Oct 1998 86:428) (Science-Week 11 Sep 98)
-------------------
Related Background:
... ... *codon and anticodon: A codon is the coding unit of
messenger RNA, comprising a triplet of nucleotides that pairs
with a corresponding triplet (anticodon) of transfer RNA. The
term "codon" is also in more general use as the basic genetic
coding unit, a triplet of nucleotides in DNA.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 11Sep98
For more information: http://scienceweek.com/swfr.htm

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5. DEMOGRAPHY:
INCREASE OF MAXIMUM LIFE-SPAN IN SWEDEN 1861-1999
The term "demography" refers to the numerical and quantitative
analysis of populations and their distributions. In 1997, a woman
named Jeanne Calment died in France at a documented age of 122.45
years, and the event and its publicity underscored the prime
question in human demographics: Is the maximum human life-span
fixed or can it be substantially increased? Although this
question and a number of subsidiary questions continue to be at
the forefront of research in human demography, few studies have
been carried out on well-defined human populations over extensive
periods.
... ... J.R. Wilmoth et al (4 authors at 3 installations, US SE)
present a study of several human demographic questions related to
life-span, the authors using Swedish national demographic data
from 1861 to 1999, which are the longest available series of
reliable information on the upper limits of achieved human life
span. The authors make the following points:
     1) The authors point out that national demographic
statistics suggest that the maximum age at death has been rising
steadily in industrialized countries for more than 100 years, and
that two important questions arise from this observation: 1) Has
this upward trend been steady over time, or has it changed pace
in recent years? Perhaps the increase has accelerated due to an
intensification of efforts to promote the health of the elderly
and to prevent or even cure ailments such as coronary heart
disease, stroke, and cancer. Or perhaps the trend has decelerated
because maximum ages now observed for humans are approaching a
hypothetical biological limit. 2) What accounts for the apparent
increase in the maximum age at death? There are two competing
explanations: a) the increase is due merely to the larger size of
contemporary populations, which increases the probability that at
least one individual will survive to an extreme old age; or b)
the increase reflects improvements in an individual's probability
of survival, especially at older ages.
     2) The authors report they examined maximum age at death in
Sweden, where the maximum age has risen from approximately 101
years during the 1860s to approximately 108 years during the
1990s. The authors report the pace of increase was 0.44 years per
decade before 1969, but accelerated to 1.11 years per decade
after that date. More than 70 percent of the rise in the maximum
age at death from 1861 to 1999 is apparently attributable to
reductions in death rates above age 70. The rest are due to
increased numbers of survivors to old age (both large birth
cohorts and increased survivorship from infancy to age 70). The
more rapid rise in the maximum age since 1969 is apparently due
to the faster pace of old-age mortality decline during recent
decades.
     3) The authors conclude: "Our analysis refutes the common
assertion that the human life-span is fixed and unchanging over
time. Although the maximum has increased much more slowly than
the average, the entire distribution of ages at death has been
shifting upward for more than a century in Sweden and,
presumably, in other countries as well. Reductions in death rates
at older ages, which have accelerated in recent decades, seem
likely to continue and may gradually extend the limits of
achieved human longevity even further."
-----------
J.R. Wilmoth: Increase of maximum life-span in Sweden, 1861-1999.
(Science 29 Sep 00 289:2366)
QY: J.R. Wilmoth: jrw@demog.berkeley.edu
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 27Oct00
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
AGING, LIFESPAN, AND SENESCENCE
Our knowledge of the basis of senescence of cells, tissues, and
organisms (including humans) has entered a new phase in recent
decades because of the new vistas opened by molecular biology.
Model systems have started to provide insights, and one important
approach has been the identification of genes that determine the
lifespan of an organism. The very existence of genes that when
mutated can extend lifespan suggests to many researchers that one
or a few processes may be critical in aging, and that a slowing
of these processes may slow aging itself. ... ... In a short
review of current research in the molecular biology of aging and
lifespan, L. Guarente et al make the following points: 1) In the
budding yeast Saccharomyces cerevisiae, aging results from the
asymmetry of cell division, which produces a large mother cell
and a small daughter cell arising from the bud. Much of the
macromolecular composition of the daughter cell is newly
synthesized, whereas the composition of the mother cell grows
older with each cell division. It has been shown that mother
cells of this yeast species divide a relatively fixed number of
times, and exhibit a slowing of the cell cycle, cell enlargement,
and sterility. Analysis of *ribosomal DNA in old cells reveals an
accumulation of *extrachromosomal ribosomal DNA of discrete
sizes, apparently representing a cumulative fragmentation of
chromosomal ribosomal DNA. The authors suggest it will be of
great interest to assess the generality of this process as an
aging mechanism. 2) In *Caenorhabditis elegans (a *nematode worm;
see notes), the *neurosecretory system regulates whether animals
enter the reproductive life cycle or arrest development at a
primitive *diapause stage. Developmental arrest is apparently
induced by a *pheromone and involves behavioral and morphological
changes in many tissues of the animal, with the lifespan becoming
4 to 8 times longer than that of the normal 3-week lifespan of
fully developed animals. Declines in pheromone concentration
induce recovery to reproductive adults with normal metabolism and
lifespan. Genes that regulate the function of the C. elegans
diapause and the neuroendocrine aging pathway have been
identified, and at least one of these genes codes for an
*insulin-like receptor apparently involved in metabolism. The
authors suggest that if the association of longevity and diapause
is general, it is possible that *polymorphisms in the human
insulin receptor-signaling pathway genes and related gene
*homologues may underlie genetic variation in human longevity. 3)
In plants, there is a large range of lifespans in the various
plant kingdoms. Certain tree species live for well over a
century, whereas other plants complete their life cycle in a few
weeks. The "yellowing" of leaves is often referred to in the
plant literature as leaf senescence or the "senescence syndrome"
-- referring to the process by which nutrients are mobilized from
the dying leaf to other parts of the plant to support their
growth. The senescence syndrome is characterized by distinct
cellular and molecular changes, with the chloroplast the first
part of the cell to undergo disassembly (producing the
"yellowing"). In many plant species, certain hormones can either
enhance or delay senescence. Although the genes that are
expressed during the plant senescence syndrome (as well as ways
to manipulate such senescence) have been identified, much remains
to be done to understand the molecular basis of aging in plants.
For example, nothing is known about the signal transduction
pathways that lead to altered gene expression during senescence,
or how plant hormones such as *cytokinin influence senescence.
But there are now many tools to explore this process. The authors
conclude: "It remains to be seen whether common mechanisms link
the aging process in diverse organisms."
-----------
L. Guarente et al (3 authors at 3 installations, US)
Aging, lifespan, and senescence.
(Proc. Natl. Acad. Sci. US 15 Sep 98 95:11034)
QY: Leonard Guarente, Mass. Inst. of Technology 617-253-1000.
-----------
Text Notes:
... ... *ribosomal DNA: A ribosome (not to be confused with
riboZYME) is a small particle, a complex of various ribonucleic
acid component subunits and proteins that functions as the site
of protein synthesis. The term "ribosomal DNA" refers to the gene
or genes that code for the RNA in ribosomes. In other words, the
term "ribosomal DNA" does not refer to any DNA in ribosomes
(there is no DNA in ribosomes).
... ... *extrachromosomal: In general, this refers to anything
outside of chromosomes, and in this case to DNA fragments
unincorporated into chromosomal DNA.
... ... *Caenorhabditis elegans: This is a small (1 mm) nematode
worm. It is transparent, hermaphroditic, free-living, and found
in soil. It has a relatively small genome (approximately 19,000
genes), and only a few types of cells in its body. It has a 16-hr
embryogenesis that can be achieved in a petri dish, and is thus
highly suitable for the study of developmental and behavioral
genetics.
... ... *nematode: An abundant and ubiquitous phylum of
unsegmented roundworms.
... ... *neurosecretory system: In general, all neural systems
contain both neurons that themselves secrete chemical messengers
and neurons that signal special secretory cells to secrete
chemical messengers. A neurosecretory pathway is a delineated
signaling system that involves such a resultant secretion.
... ... *diapause: In general, this refers to any programmed
period of suspended development in invertebrates. 
... ... *pheromone: In general, a chemical substance which, when
released into an animal's surroundings, influences the
development or behavior of other individuals of the same species.
... ... *insulin: A protein hormone that promotes uptake by body
cells of free glucose and/or amino acids, depending on target
cell type.
... ... *polymorphisms: A genetic polymorphism is a naturally
occurring variation in the normal nucleotide sequence of the
genome within individuals in a population. Variations are denoted
as polymorphisms only if they cannot be accounted for by
recurrent mutation and occur with a frequency of at least about 1
percent.
... ... *homologues: In general, the term "homologous" means
having the same structure. But the term has special uses in
genetics and evolution biology.
... ... *cytokinin: A group of plant growth substances. They are
chemically identified as derivatives of the purine base adenine.
They stimulate cell division and determine the course of
differentiation. They work synergistically with other plant
hormones called "auxins".
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 6Nov98
For more information: http://scienceweek.com/swfr.htm

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6. MEDICAL BIOLOGY:
ON PROSTATE CANCER
In the US, *adenocarcinoma of the prostate is the most common
malignancy in men older than 50 years, the incidence increasing
with each decade of life. Approximately 210,000 new cases occur
in the US each year. *Sarcoma of the prostate is rare, occurring
primarily in children. Other forms of prostate cancer also occur,
and these respond poorly to the usual control measures.
... ... C. Abate-Shen and M.M. Shen (University of Medicine and
Dentistry New Jersey, US) present an extensive review of the
molecular genetics of prostate cancer, the authors making the
following points:
     1) In the US, prostate cancer afflicts 1 man in 9 over the
age of 65 and represents the most frequently diagnosed cancer in
American men. Early detection via serum testing for *prostate
specific antigen (PSA) and improved procedures for surgical
intervention and radiation therapy have significantly reduced the
number of fatalities; but there is still no effective cure for
men with advanced disease. Much research, therefore, has been
dedicated to identifying prognostic markers that distinguish
indolent versus aggressive forms of prostate cancer. In contrast,
significantly less research has been devoted to understanding the
molecular mechanisms that underlie normal prostate growth and
development or cancer initiation and progression.
     2) Most prostate tumors are adenocarcinomas, sharing
numerous common features with other prevalent *epithelial
cancers, such as breast and colon cancer. A distinguishing
feature of prostate cancer is its intimate association with
aging; indeed, aging is the single most significant risk factor
for prostate cancer. Although pre-neoplastic lesions (known as
prostatic intra-epithelial neoplasia [PIN]) can be found in men
in their twenties and are fairly common in men by their fifties,
clinically detectable prostate cancer is not generally manifest
until the age of 60 or 70. Furthermore, the occurrence of
precancerous lesions is significantly more prevalent
(approximately 1 in 3 men) than the incidence of carcinoma
(approximately 1 in 9 men). Therefore, whereas the morphological
changes associated with initiation are relatively common and
occur early in life, progression to *invasive carcinoma is a
significantly less common event that occurs in a more limited
population as a consequence of aging.
     3) The incidence of prostate cancer in the US is
significantly higher than in most other countries, particularly
Asian countries, even though the incidence of histological pre-
neoplastic lesions has been reported to be similar worldwide.
Dietary and environmental factors have therefore been presumed to
play a key role in prostate carcinogenesis, similar to their role
in other common epithelial cancers.
     4) Hereditary factors account for a relatively small
percentage (approximately 10 percent) of prostate cancers and are
generally associated with early onset disease. To date, two
familial susceptibility loci have been mapped to the X chromosome
and to a region of chromosome 1q, although the respective
candidate genes have not yet been identified. In addition,
several studies have identified a statistical association between
breast and prostate cancer, but the molecular basis for such a
link is unresolved.
     5) *Steroid hormone receptor signaling plays an apparently
pivotal role in all stages of prostate carcinogenesis. In
particular, there is a characteristic age-related decrease in the
ratio of *androgens to *estrogens in men, which may represent a
contributing factor in prostate cancer initiation.
     6) A primary goal for future research will be to establish a
definitive molecular pathway of prostate cancer initiation and
progression, accompanied by a precise understanding of the
functional roles of candidate genes and cell regulatory pathways.
Achieving this objective will require overcoming the significant
obstacles imposed by the limited availability of homogeneous
genetic material from human prostate cancer specimens. The
continued development of sensitive techniques for isolation and
analysis of limited quantities of genomic DNA and *messenger RNA
(mRNA) should help overcome these limitations. In addition, the
molecular identification and analysis of familial susceptibility
genes for prostate cancer may provide critical breakthroughs in
this endeavor.
     7) The authors conclude: "Although the molecular biology of
prostate cancer has only just emerged from its infancy, the
adolescent maturation of this field appears likely in the not-
too-distant future. In particular, the advent of sophisticated
mouse models will undoubtedly lead to crucial developments in our
understanding of this much-feared disease."
-----------
[Editor's note: This extensive review contains over 300
references with full titles of research papers.]
-----------
C. Abate-Shen and M.M. Shen: Molecular genetics of prostate
cancer.
(Genes & Development 1 Oct 00 14:2410)
QY: Cory Abate-Shen: abate@cabm.rutgers.edu
-----------
Text Notes:
... ... *adenocarcinoma: In general, a tumor of epithelial cells
(see below) in which the cells are in a glandular or gland-like
pattern.
... ... *Sarcoma: In general, a connective tissue neoplasm,
usually highly malignant.
... ... **prostate specific antigen: In general, an antigen is
any entity that provokes an immune response, and this includes,
in certain disease states, entities that are not "foreign" to the
body. Prostate specific antigen is a single-chain 31 kilodalton
glycoprotein with 240 amino acid residues and 4 carbohydrate side
chains. It is produced by prostatic *epithelial cells and is
normally found in seminal fluid and circulating blood. Elevations
of serum prostate specific antigen are highly organ-specific, but
such elevations occur in both prostate cancer (adenocarcinoma)
and benign prostate disease (e.g., benign prostatic hyperplasia).
... ... *epithelial: In animals, "epithelial cells" compose
the cell layers that form the interface between a tissue and the
external environment, for example, the cells of the skin, the
lining of the intestinal tract, and the lung airway passages.
... ... *invasive carcinoma: In this context, the term "invasive"
refers to infiltration of cancer cells beneath the epithelial
*basement membrane.
... ... *basement membrane: Found in various animal tissues, this
is a layer of dense fibrous material interposed between cells and
adjacent connective tissue.
... ... *Steroid hormone receptor signaling: In this context, the
term "receptor" refers to a molecular constituent of a cell
membrane, the constituent interacting specifically with chemical
messengers (e.g., hormones) secreted by other cells, the
interaction producing a specific cellular response in the cell
receiving the signal. In general, a steroid hormone is any
member of a group of biological lipids having a particular
structure of 4 fused carbon rings. The sex hormones, adrenal
cortical hormones, vitamin D, and bile acids are steroids.
Certain carcinogens are also steroids.
... ... *androgens: A generic term for the male sex hormones.
... ... *estrogens: Estrogen is a collective term for the female
hormones, the most powerful of which is estradiol. They control
female secondary sexual characteristics, and prepare and maintain
the uterine lining.
... ... *messenger RNA (mRNA): The ribonucleic acid molecule
transcribed from DNA that carries the coded information
specifying the sequence of amino acids in a protein.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 27Oct00
For more information: http://scienceweek.com/swfr.htm

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7. IN FOCUS: ON THE EVOLUTION OF THE NERVOUS SYSTEM
"Animals such as the sea anemone and jellyfish developed the
first nervous systems, which were simple nerve nets. The sponges,
still more primitive animals, have no nervous system at all. A
sponge does not behave, it just rests on the bottom of the sea.
If nutrients are in the water, it lives; if not, it dies. The
jellyfish and the sea anemone represent a great advance over the
sponge because they behave; for example, a jellyfish can swim to
where nutrients are and capture them. In order for a
multicellular animal to move, its cells must somehow be made to
move, and some [cells] accordingly have become specialized as
muscle tissue that can contract. In order for these movements to
accomplish anything they must somehow be controlled so that they
occur together. Even in the sponge there is a small degree of
coordination. If a sponge is prodded in one place, a limited
movement of surrounding cells will occur. Hence the cells somehow
communicate with one another. This communication is thought to be
an electrochemical process that occurs at the cell membranes.
Basically the same mechanism became elaborated into a specialized
cell, the neuron, or nerve cell, that can communicate over longer
distances. Groups of neurons could form larger systems such as
the nerve net of the jellyfish. So far as is known, neurons in
animals from jellyfish to humans utilize the same basic
electrochemical mechanisms for conduction information. The
primitive mechanisms of the jellyfish worked so well that it
became fixed in evolution. In order to progress beyond the
jellyfish's repertoire of behavior and generate more
sophisticated and adaptive behaviors, what was primarily needed
was more neurons put together in more complicated ways. If one
looks at the general structure of the nervous system in such
diverse animals as earthworms, ants, octopuses, and humans, one
might feel that nature has experimented endlessly with different
kinds of nervous systems. But... the basic mechanisms of action
of the neurons in all of these creatures are the same. What is
enormously different is the organization of the neurons, their
patterns of interconnection."
-----------
Richard F. Thompson: _The Brain: An Introduction to Neuroscience_
W.H. Freeman, New York 1985, pp.7-8.
-------------------
SCIENCE-WEEK http://scienceweek.com 27Oct00
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
IN FOCUS: ON THE BRAINS OF MICE AND HUMANS
"No category of cell, no particular type of circuit is specific
to the human cerebral cortex. The components of our cerebral
machinery derive from a stock very similar, if not identical, to
that of the mouse. The major event in the evolution of the
mammalian brain is the expansion of the neocortex. This growth is
accompanied by an increase in the total number of neurons, and
thus in the number and complexity of the operations which the
cortex can perform. The number of cellular elements per unit of
surface area has not changed. The cortical thickness varies, but
much less than its surface area. On average, the cortex of man is
only three times thicker than that of the mouse, although the
increase is not uniform in all layers... The more the surface
area of the cortex expands, the more the number of neurons
capable of establishing association connections increases... This
translates, finally, into an increase in the mean number of
connections per neuron, with a consequent burgeoning of the
dendritic and axonal trees, reaching a maximum in man.
Nevertheless, the increase in the mean number of synapses per
neuron is not directly proportional to the increase in cortical
area. Far from it. The density of synapses per cubic millimeter
of cortex is of the same order in the rat as in man... At the
levels of both the macroscopic anatomy of the cortex and its
microscopic architecture, no sudden qualitative reorganization
marks the passage from the "animal" brain to the human brain.
There is, on the contrary, a continuous _quantitative_ evolution
in the total number of neurons, the diversity of areas, the
number of possible connections between neurons, and, therefore,
the complexity of the neuronal networks that make up the cerebral
machine."
-----------
Jean-Pierre Changeux: _Neuronal Man: The Biology of Mind_
(Oxford University Press, Oxford 1985, p.66)
(Science-Week 19 Mar 99)

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8. FROM THE SCIENCEWEEK ARCHIVE:
A CRITICISM OF US ACADEMIC RESEARCH IN BIOLOGY
Most academic biologists over 50 remember a time when the center
of biology on the campus was the decaying zoology building, or
the connected decrepit zoology-botany buildings, display cases
crowding halls lit with yellow tungsten bulbs, tiny laboratories
cluttered with old microscopes and split wooden stools, and
everywhere the faint smell of formaldehyde wafting in from the
anatomy labs despite open windows to let in fresh air and the
smell of outside greenery. Those were the days before molecular
biology and millions of dollars for research abruptly loomed and
made the earth tremble. These days the center of biology on
campus is more likely to be a cluster of new multi-million-dollar
buildings housing the laboratories of molecular biology, the
windows in these corporate-appearing buildings sealed, the
circulating air carefully filtered, and on each floor a multitude
of laboratory technicians busy with the bench work formerly the
daily grind of professors. With apologies to Pinter, the past is
definitely another world. The emergence of heavily funded
molecular biology has been called a profound scientific
revolution in biology, a blessing of the biological sciences and
the research universities that foster them, but not everyone
agrees, and indeed some people think of the change in academic
biology as the ascendance of a research Godzilla.
... ... Steven Vogel reviews the current situation in US
university biology research, and the author makes the following
points: 1) Current American biology is experiencing the impact of
a growing institutional preference for expensive science -- a
preference with pernicious implications for universities and for
science. 2) At present, the majority of biologists focus on
molecules and subcellular phenomena, and most of the money spent
on biological research supports this work. The combination of
overall expense and high cost per investigator has turned
molecular biology into "academically correct" biology. 3)
Academically correct biology has 4 important features: a) it
seeks molecular explanations; b) it views scientific progress as
a matter of incremental accretion of detail; c) its fairly
immediate goal is human therapy; and, d) its operation is
unabashedly entrepreneurial. All four characteristics prove
conveniently consistent with an overall goal of institutional
growth, and used together as a basis for academic decision-
making, they produce a displacement of other kinds of scientific
investigation. 4) The dominance of academically correct biology
is produced by the availability of support for it, particularly
support from the US National Institutes of Health (NIH), which
has become the largest source of funding for scientific
activities at many universities -- and NIH seems especially fond
of the chemo-reductionist paradigm. 5) The unprecedented
concentration of personal and material resources in molecular
biology may have produced a peculiar paradox. The field may now
be progressing at a rate as slow as that of any area of science
ever actively pursued -- if we consider conceptual progress
relative to the number of active investigators. 6) Science
without data is unimaginable, but data are not science. Equating
the acquisition of data with the progress of science implies that
great generalizations will necessarily follow when sufficient
data are gathered -- an uncertain proposition. 7) The history of
science indicates that few major conceptual advances were driven
by anticipation of immediate utility... An excessive focus by a
university on medical therapy as a short-term research goal is
unhealthy. Too often resources will be concentrated on projects
of lower fundamental importance and intellectual interest. 8)
Especially pernicious are the self-serving attitudes that good
science costs large amounts of money and that the quality of
scientists -- and of science departments -- can be judged by the
funds they raise. 9) Academically correct biology damages mostly
by displacement. The multidimensionality of biological science,
the diversity of elements that should matter for academic
success, the idea of science as more than a compendium of facts
-- all are severely compromised.
-----------
S. Vogel (Duke University, US)
Academically correct biological science.
(American Scientist Nov/Dec 1998 86:504)
QY: Steven Vogel: svogel@acpub.duke.edu
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 6Nov98
For more information: http://scienceweek.com/swfr.htm

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