ScienceWeek

SCIENCE-WEEK

A Weekly Digest of the News of Science

July 17, 1998

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Our biology has made us into creatures who are constantly
recreating our psychic and material environments, and whose
individual lives are the outcomes of an extraordinary
multiplicity of intersecting causal pathways. Thus, it is
our biology that makes us free.
-- Richard Lewontin

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Contents of This Issue:

1. Human Cloning: Two Views Opposed
2. Cosmology: The End of the Old Model Universe
3. On the Future of Earth and the Universe
4. Entanglement, Decoherence, and the Quantum-Classical Boundary
5. Geology: A Sharp Controversy Concerning a Rock-Dating Method
6. Lipid Bilayers: A New Molecular Probe
7. Prebiotic Organic Compounds: Oceanic Protection from Solar UV
8. Fossils of Two New Feathered Dinosaurs
9. Mechanisms of Tumor Suppressor Genes
10. Drug Addiction and the Glutamate Neurotransmitter

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1. HUMAN CLONING: TWO VIEWS OPPOSED
The issue of acceptance vs. prohibition of human cloning will
erupt again (and again) as soon as new information piques the
interest of commercial media. Meanwhile, a quiet debate continues
among professionals, and the *New England Journal of Medicine*
has now published a precis of the controversy, with John A.
Roberston (University of Texas Austin, US) formulating an
acceptance view, and George J. Annas (Boston University, US)
formulating an opposing position. Robertson's position has
several aspects: 1) There is no reason to think that the ability
to clone humans will cause many people to turn to cloning when
other methods of reproduction would enable them to have healthy
children. Cloning a human being by *somatic cell nuclear
transfer, for example, would require a consenting person as a
source of the DNA, eggs to be enucleated and then fused with the
DNA, a woman who would carry and deliver the child, and a person
or couple to raise the child. Given this reality, cloning is most
likely to be sought by couples who, because of infertility, a
high risk of severe genetic disease, or other factors, cannot or
do not wish to conceive a child. 2) Having the same genome as
another person is not in itself harmful, as widespread experience
with *monozygotic twins shows. Being a twin does not deny either
twin his or her individuality or freedom, and twins often have a
special intimacy or closeness that few non-twin siblings can
experience. There is no reason to think that being a later-born
identical twin resulting from cloning would change the overall
assessment of being a twin. 3) There is no rational basis for the
idea that parents who choose their child's genome through
somatic-cell cloning will view the child as a commodity or an
object to serve their own ends. We do not view children born
through coital or assisted reproduction as "mere means" just
because people reproduce in order to have company in old age, to
fulfill what they see as God's will, to prove their virility, to
have heirs, to save a relationship, or to serve other selfish
purposes. What counts is how a child is treated after birth.
Self-interested motives for having children do not prevent
parents from loving children for themselves once they are born.
Robertson concludes: "Cloning illustrates the principle that when
legitimate uses of a technique are likely, regulatory policy
should avoid prohibition and focus on ensuring that the technique
is used responsibly for the good of those directly involved." The
contrary views of G.J. Annas are essentially as follows: 1)
Cloning would devalue children and treat them as interchangeable
commodities. 2) Cloning would radically alter what it means to be
human by replicating a living or dead human being asexually to
produce a person with a single genetic parent. 3) The danger is
that through human cloning we will lose something vital to our
humanity, the uniqueness (and therefore the value and dignity) of
every human. 4) Cloning represents the height of genetic
reductionism and genetic determinism. Annas concludes that human
cloning should be prohibited, and that "we should also take the
opportunity to fill in the regulatory lacuna that permits any
individual scientist to act first and consider human consequences
later..."
QY: John A. Robertson, University of Texas Austin 512-471-3434.
QY: George J. Annas, Boston University 617-353-3700.
(New England J. Med. 9 July 98 339:119,122)
(Science-Week 17 Jul 98)

-------------------

Related Background:

... ... *somatic cell nuclear transfer: Somatic cells are cells
other than germline cells (egg cells and sperm cells). The
transfer technique indicated involves the transfer of the nucleus
of a somatic cell (which contains the genome for the individual)
to an enucleated egg cell. The egg cell now has a new nucleus,
and it is the genome in the new nucleus that determines the
development of the egg cell.
... ... *monozygotic twins: Monozygotic twins are genetically
identical, derived from the division and autonomous development
of a single zygote (fertilized egg).


2. COSMOLOGY: THE END OF THE OLD MODEL UNIVERSE
Cosmologists are apparently expecting the near-future necessity
for profound conceptual alterations in their field. Peter Coles
(University of London, UK) presents a short review of the current
situation and makes the following points: 1) Observations only
recently made possible by improvements in astronomical
instrumentation have put theoretical models of the Universe under
intense pressure. The standard ideas of the 1980s about the shape
and history of the Universe have now been abandoned -- and
cosmologists are now taking seriously the possibility that the
Universe is pervaded by some sort of "vacuum energy" whose origin
is not at all understood. 2) The weakness of the Big Bang model
is that the numerical values of certain essential parameters in
the model (the Hubble constant, the density parameter, and, in
some versions, the cosmological constant) are not predicted by
theory, and thus the parameters must be inferred from
observations. 3) The Big Bang model does not deserve to be called
a "theory" unless and until it can explain how nonuniformities of
galaxies and clusters of galaxies came into being and evolved. 4)
The Cold Dark Matter model of structure formation, first proposed
in the 1980s, is in serious difficulty because the consequent
significant gravitational brake on expansion is not evident, and
in fact expansion may be accelerating. Current observations
coupled with current dynamical arguments all suggest a global
density of matter in the Universe less than the value required to
make the Universe recollapse. 5) The existence of a cosmological
constant (or vacuum energy) of the required size necessary to
make the basic cosmological models work is not at all explained
by current theories of the fundamental interactions of matter. 6)
There is every reason to be confident that the important issues
will soon be resolved, because a data explosion is about to
engulf cosmology, a new generation of galaxy surveys. The Sloan
Digital Sky Survey, for example, will encompass more than a
million galaxies. The cosmological community is bracing itself
for the arrival of these enormous new data sets and the new
insights they will surely bring. 7) It is possible that none of
the available models will fit all the new data. Coles concludes:
"For many of us, that is the most exciting possibility of all, as
we would have to move to stranger theories, perhaps not even
based on General Relativity."
QY: Peter Coles 
(Nature 25 Jun 98 393:741) (Science-Week 17 Jul 98)


3. ON THE FUTURE OF EARTH AND THE UNIVERSE
Adams and Laughlin (2 installations, US) present a rather
remarkable essay on the future of the universe, the extrapolation
based on the "open" or continuing expansion universe model, with
the authors demarcating various epochs in a time-span that ranges
from the Big Bang to 10^(100) years into the future. They make
the following points: 1) Eventually the stars and galaxies that
define our era will give way to a cosmos of bizarre frozen stars,
evaporating black holes, and lonely atoms the size of galaxies.
2) In roughly 1.1 billion years, according to the current theory
of stellar evolution, our own Sun will heat up enough to make the
Earth inhospitable to life. In 7 billion years, the Sun will
become a full-fledged *red giant star, expanding in size to
nearly engulf the Earth, and certainly melting the Earth's crust
completely and "obliterating every trace of the geology, biology,
and civilizations that once graced the planetary surface." A few
hundred million years after that, the Sun will exhaust its
nuclear fuel, shed its outer layers to become a *white dwarf
star, and begin a slow fade to black. 3) In the time frame of
10^(100) years, the 10 or 15 billion years already gone by
represent an utterly insignificant fragment of time. The
significant entries on the cosmic calendar outlined by the
authors are as follows:
 -- 10^(-44) seconds: *Big Bang. The indicated time is the Planck
time, the quantum unit of time itself, and indivisible.
 -- 10^(-37) seconds: *Inflation begins.
 -- 10^(-34) seconds: Microscopic fluctuations that will become
the seeds of galaxies and clusters of galaxies.
 -- 10^(-32) seconds: Inflation ends. An interval of continual
expansion and cooling begins, the Universe dominated by smooth,
uniform, and dense radiation, with stars and galaxies not yet
formed.
 -- 10^(-10) seconds: Electroweak phase transition; the
electromagnetic and *weak forces become separate for the first
time.
 -- 10^(-5) seconds: *Quarks become confined to form protons and
neutrons.
 -- 10^(2) seconds: Synthesis of light elements.
 -- 10^(5.5) years: Electrons and protons combine to form
hydrogen atoms. Universe becomes transparent; *cosmic background
radiation breaks free.
 -- 10^(6) years: First possible stars.
 -- 10^(8.8) years: Formation of galaxies.
 -- 10^(10) to 10^(10.1) years: Lifespan of Sun and warm Earth.
 -- 10^(17) years: Most planets are detached from stars.
 -- 10^(20) years: Most stars and planets have left galaxies.
 -- 10^(25) years: Remaining dark white dwarfs absorb and deplete
*weakly interacting massive particles (WIMPS) from galactic
halos.
 -- 10^(30) years: *Black holes accrete remaining dark white
dwarfs and *neutron stars on galaxy-size scales.
 -- 10^(33) years: Black holes accrete remaining stars on
cluster-size scales.
 -- 10^(37) years: Possible decay of protons. Nothing made of
atoms remains.
 -- 10^(44) years: Possible decay of *axions into photons.
 -- 10^(46) to 10^(64) years: Black holes the only remaining
concentration of mass.
 -- 10^(65) years: Stellar mass black holes evaporate.
 -- 10^(83) years: Million-solar-mass black holes evaporate.
 -- 10^(99) years: Largest galaxy-mass black holes evaporate;
empty era begins.
 -- 10^(108) years: *Positronium formation and decay in a flat
universe.
The authors introduce what they call the "Copernican time
principle". Just as our planet, and hence humankind, has no
special location, the current cosmological epoch has no special
place in the vast expanse of cosmic time. The authors state:
"This principle thus exorcises the last vestiges of
anthropocentric thought."
QY: Fred C. Adams, University of Michigan 313-764-7433.
(Sky & Telescope August 1998) (Science-Week 17 Jul 98)

-------------------

Related Background:

... ... *red giant star: A red giant star is a star in a late
stage of evolution, having exhausted the hydrogen fuel in its
core. It has a surface temperature of less than 4700 degrees
Kelvin and a diameter 10 to 100 times that of the Sun.
... ... *white dwarf star: White dwarf stars are extremely dense
and compact stars that have undergone gravitational collapse.
They are the final stage in the evolution of low-mass stars after
they have lost their outer layers. White dwarf stars are about
the size of Earth, but with a mass about that of the Sun.
... ... *Big Bang: From the *Big Bang theory, the general
cosmological model that proposes that all matter and radiation in
the universe originated in an explosion at a finite time in the
past.
... ... *Inflation: From the inflationary model of the initial
universe. The inflationary model, first proposed by Alan Guth in
1980, proposes that quantum fluctuations in the time period
10^(-35) to 10^(-32) seconds after time zero were quickly
amplified into large density variations during the
"inflationary" 10^(50) expansion of the universe in that time
frame.
... ... *weak forces: The weak force, one of the four fundamental
forces, occurs between leptons (particles without internal
structure, e.g., electrons, neutrinos) and hadrons (particles
with internal structure, e.g., neutrons and protons); the weak
force is responsible for radioactivity.
... ... *Quarks: A quark is a hypothetical fundamental particle,
having charges whose magnitudes are one-third or two-thirds of
the electron charge, and from which the elementary particles may
in theory be constructed.
... ... *cosmic background radiation: Unresolved radiation from
space, the cumulative effect of many unresolved and individually
weak discrete sources. One important form is the microwave
background radiation which is considered to be due to the "hot"
Big Bang. The "hot-Big-Bang" theory is the specific version
proposed by George Gamow in the 1940s in which the temperature of
matter and radiation decreases with time.
... ... *weakly interacting massive particles (WIMPS): This
refers to a hypothetical elementary particle that is a candidate
for cosmic dark matter, a stable neutral particle, somewhat
heavier than the neutron, that interacts only weakly with
ordinary matter.
... ... *Black holes: If the terminal stages of star death leave
a remnant star mass greater than 3 solar masses, the ultimate
gravitational collapse will produce a black hole, a relativistic
singularity. A black hole is a localized region of space from
which neither matter nor radiation can escape. The "trapping"
occurs because the requisite escape velocity, which can be
calculated from the relevant equations, exceeds the velocity of
light and is therefore unattainable. Another view of a black hole
is that it is a mass that has collapsed to such a small volume
that its gravity prevents the escape of all radiation. Space and
time essentially have no meaning in a black hole. The boundary of
the black hole is called the "event horizon", because any event
within the boundary is invisible outside, the invisibility
resulting from the fact that no radiation can escape to be
detected. The radius of the black hole depends upon how much
matter has fallen into the region; it is called the "Schwarzchild
radius", and it is usually a few kilometers. However, massive
black holes are possible and are thought to be the source of
quasars (quasi-stellar objects), which are extremely luminous
sources radiating energy over the entire spectrum from x-rays to
radio waves, and which are apparently the oldest and most distant
objects in the universe. If quasars indeed involve black holes,
the radiation is from material just outside the black hole, and
not from anything within it. Nothing inside a black hole can get
out of it.
... ... *neutron stars: If, following its terminal stages, the
remnant mass of a star is between 1.4 and 2 to 3 solar masses,
the star will collapse into a neutron star, a body with a radius
of 10 to 15 kilometers, with a core so dense that its component
protons and electrons have merged into neutrons. The average
density of a neutron star is 10^(15) grams per cubic centimeter,
and the weight of an object on the surface of a neutron star
would be 10^(11) its weight on the surface of the Earth. Neutron
stars apparently have an outer shell of iron, but it is iron like
no Earth iron, an iron of 4 orders of magnitude greater density.
Theory predicts that a neutron star should rotate very rapidly,
be extremely hot, and have an intense magnetic field. Pulsars,
sources of pulsed radio energy, are evidently spinning neutron
stars which emit beams of radiation from their magnetic poles. A
few pulsars have been found in binary systems, and the empirical
estimated masses of the pulsars are consistent with the masses
predicted by neutron star models. 
... ... *axions: A hypothetical elementary particle of very low
mass and zero charge, and one of the candidates for dark matter
in the Universe.
... ... *Positronium: A positron-electron system that lasts for a
measurable time before combining to produce annihilation
radiation. Positronium can be thought of as an atom analogous to
that of hydrogen in which the electron and positron move in
orbits about the center of mass halfway between them. A positron
is the antiparticle of the electron, with a rest mass equal to
that of the electron, but with opposite charge.


4. ENTANGLEMENT, DECOHERENCE, AND THE QUANTUM-CLASSICAL BOUNDARY
Quantum mechanical entanglement is a phenomenon that has caught
the imagination of the public as one of the more bizarre
consequences of fundamental physical theory. Entanglement is
unique to quantum mechanics, and involves a relationship (a
"superposition of states") between the possible quantum states of
two entities such that when the possible states of one entity
collapse to a single state as a result of suddenly imposed
boundary conditions, a similar and related collapse occurs in the
possible states of the entangled entity no matter where or how
far away the entangled entity is located. Entanglement arises
from the wave function equation of quantum mechanics, which has
an array of possible function solutions rather than a single
function solution, with each possible solution describing a set
of possible probabilistic quantum states of the physical system
under consideration. Upon fixation of the appropriate boundary
conditions, the array of possible solutions collapses into a
single solution. For many quantum mechanical physical systems,
the fixation of boundary conditions is a theoretical and
fundamental consequence of some interaction of the physical
system with something outside that system, e.g., an interaction
with the measuring device of an observer. In this context, two
entities that are described by the same array of possible
solutions to the wave function equation are said to be
"coherent", and when events decouple these entities, the
consequence is said to be "decoherence". As a physical
phenomenon, entanglement was discussed many years ago, most
particularly following the publication in 1935 of the often
quoted Einstein-Podolsky-Rosen paper (*Physical Review* 1935
47:777). These discussions have been in the form of "gedanken"
(thought) experiments involving two quantum-mechanical entangled
entities. More recently, however, there have been laboratory
constructions of actual quantum mechanical systems exhibiting
such entanglement phenomena, and the reportage of these
laboratory arrangements by the media have engaged the public
fancy. Essential here is that any purely verbal account of
quantum mechanical phenomena is severely limited by the
constraint that the properties of quantum mechanical systems can
be precisely described only by the equations relevant for those
systems, and all other descriptions usually introduce serious
ambiguities. ... ... Serge Haroche (Ecole Normale Superieure
Paris, FR) reviews quantum mechanical entanglement, decoherence,
and the question of the boundary between the physics of quantum
phenomena and the physics of classical phenomena. Haroche makes
the following points: 1) In quantum mechanics, a particle can be
delocalized (simultaneously occupy various probable positions in
space), can be simultaneously in several energy states, and can
even have several different identities at once. This apparent
"weirdness" behavior is encoded in the wave function of the
particle. 2) Recent decades have witnessed a rash of experiments
designed to test whether nature exhibits implausible nonlocality.
In such experiments, the wave function of a pair of particles
flying apart from each other is entangled into a non-separable
superposition of states. The quantum formalism asserts that
detecting one of the particles has an immediate effect on the
other, even if they are very far apart, even far enough apart to
be out of interaction range. The experiments clearly demonstrate
that the state of one particle is always correlated to the result
of the measurement performed on the other particle, and in just
the strange way predicted by quantum mechanics. 3) An important
question is: Why and how does quantum weirdness disappear
(decoherence) in large systems? In the last 15 years, entirely
solvable models of decoherence have been presented by various
authors (e.g., Leggett, Joos, Omnes, Zeh, Zurek), these models
based on the distinction in large objects between a few relevant
macroscopic observables (e.g., position or momentum) and an
"environment" described by a huge number of variables, such as
positions and velocities of air molecules, number of black-body
radiation photons, etc. The idea of these models, essentially, is
that the environment is "watching" the path followed by the
system (i.e., interacting with the system), and thus effectively
suppressing interference effects and quantum weirdness, and the
result of this process is that for macroscopic systems only
classical physics obtains. 4) In mesoscopic systems, which are
systems between macroscopic and microscopic dimensions,
decoherence may occur slowly enough to be observed. Until
recently, this could only be imagined in a gedanken experiment,
but technological advances have now made such experiments real,
and these experiments have opened this field to practical
investigation.
QY: Serge Haroche, Ecole Normale Superieure Paris, FR.
(Physics Today July 1998) (Science-Week 17 Jul 98)

-------------------

Related Background:

EXPERIMENTAL QUANTUM TELEPORTATION
Quantum teleportation is the transmission and reconstruction over
arbitrary distances of the state of a quantum system, an effect
first suggested by Bennett et al in 1993 (Phys. Rev. Lett.
70:1895). The achievement of the effect depends on the phenomenon
of entanglement, an essential feature of quantum mechanics.
Entanglement is unique to quantum mechanics, and involves a
relationship (a "superposition of states") between the possible
quantum states of two entities such that when the possible states
of one entity collapse to a single state as a result of suddenly
imposed boundary conditions, a similar and related collapse
occurs in the possible states of the entangled entity no matter
where or how far away the entangled entity is located. Polarizat-
ion is essentially a condition in which the properties of photons
are direction dependent, a condition that can be achieved by
passing light through appropriate media. Bouwmeester et al (6
authors, Univ. of Innsbruck, AT) now report an experimental
demonstration of quantum teleportation involving an initial
photon carrying a polarization that is transferred to one of a
pair of entangled photons, with the polarization-acquiring photon
an arbitrary distance from the initial one. The authors suggest
quantum teleportation will be a critical ingredient for quantum
computation networks.
QY: Dik Bouwmeester 
(Nature 11 Dec 97) (Science-Week 2 Jan 98)

-------------------

Related Background:

REPORT OF FIRST QUANTUM MECHANICAL ENTANGLEMENT OF ATOMS
... In the past, evidence of quantum mechanical entanglement has
been restricted to elementary particles such as protons,
electrons, and photons. Now E. Hagley et al, using rubidium
atoms prepared in circular Rydberg states (which means the outer
electrons of the atom have been excited to very high energy
states and are far from the nucleus in circular orbits), have
shown quantum mechanical entanglement at the level of atoms.
What is involved is that the experimental apparatus produces two
entangled atoms, one atom in a ground state and the other atom
in an excited state, physically separated so that the
entanglement is non-local, and when a measurement is made on one
atom, let us say the atom in a ground state, the other atom
instantaneously presents itself in the excited state -- the
result of the second atom wave function collapse thus determined
by the result of the first atom wave function collapse. There is
talk that before long quantum mechanical entanglement may be
demonstrated for molecules and perhaps even larger entities.
[Phys. Rev. Lett. 79:1 (1997)]

-------------------

Related Background:

QUANTUM PHOTON ENTANGLEMENT AT A DISTANCE OF SEVEN MILES
Whether or not the quantum mechanical behavior of elementary
particles is called mysterious depends, more or less, on the
attitude one has. If there is a demand that the behavior of these
particles be explainable with the logistic structure of human
language, then some aspects of their behavior seem mysterious
indeed. On the other hand, if there is a willingness to admit
that the logical structure of human language may not at present
be isomorphic with the logical structure of the laws that govern
the behavior of these particles, then it is probably best to put
off notions of mysteries and take the behavior for what it is.
This week there was announced to the popular press, before
publication, the results of a twin-photon experiment in
Switzerland. Nicolas Gisin et al (University of Geneva, CH)
reported that a pair of twin photons split and sent along two
diverging paths, when arriving at terminals seven miles apart,
exhibit the phenomenon of quantum "entanglement". The gist of it
is that the detection of one of the photons effectively causes
the collapse of the spectrum of its wave-function solutions to a
single solution, and this collapse instantaneously causes the
collapse of the possible quantum states of the other photon, in
this case seven miles away. The melodramatic notion (purveyed by
the press) is that information has somehow travelled from one
photon to the other at a speed greater than the speed of light,
with the result that great canons of thought are thereby
destroyed. But perhaps the more prosaic reality is that any
attempt to describe non-classical events with language based on
classical laws and perceptions cannot succeed.
(New York Times 22 Jul 97)


5. GEOLOGY: A SHARP CONTROVERSY CONCERNING A ROCK-DATING METHOD
The geology community is evidently in the midst of an apparent
scandal concerning the rock-dating data produced by a prominent
researcher. The elements of the story are as follows: 1) Data
from Ronald Dorn (Arizona State University Tempe, US) concerning
hundreds of petroglyphs, stone tools, and rock surfaces around
the world are in question. 2) These data were produced by a
method of dating the organic material in rock varnish samples
(see below). It is being reported that rock varnish samples
processed by Dorn contain microscopic granules of coal and
charcoal, which it is said render the dating results meaningless,
with implications for such debates as the peopling of the
Americas. 3) The carbon granules evidently do not appear in
samples processed by other researchers, and it said the US
National Science Foundation and Arizona State University are
reviewing the possibility of misconduct. 4) Dorn is reported to
acknowledge that his technique is flawed and produces "ambiguous"
results. But he says the suggestion of tampering is "utterly
false" and that the carbon granules are naturally occurring. 5)
The technique in question involves accelerator mass spectrometry
radiocarbon analysis, one of several rock-surface dating methods
pioneered since the 1980s by Dorn. The method assumes that
microscopic quantities of carbon-rich organic material become
trapped in and beneath a thin layer of natural varnish on the
rock surface. Although some specialists have doubted the trapped
material can be accurately dated, Dorn has argued since 1986 that
the material holds measurable quantities of radioactive carbon-
14, which decays at a known rate. To date a rock, Dorn scrapes
the varnish and material beneath the varnish, extracts the
organic material with acid, then sends samples to various
accelerator mass spectrometry facilities. This controversy is
apparently serious enough so that most geologists are now
considering all of Dorn's data suspect, and rock-varnish dating
in general of significantly reduced utility. A technical
commentary by Beck et al (7 authors at 4 installations, US CH)
has been published to alert the geology community to the problem.
QY: David Malakoff 
QY: W. Beck, University of Arizona 520-621-2211.
(Science 26 Jun 98 280:2132) (Science-Week 17 Jul 98)


6. LIPID BILAYERS: A NEW MOLECULAR PROBE
Substances that exhibit both hydrophilic and hydrophobic
properties in the same molecule are called amphipathic, and
examples of these are the lipid surfactants important in soaps
and biological membranes. In aqueous solution, these lipid
molecules form spherical vesicles (liposomes) in which the lipid
molecules are spontaneously arranged into bilayers (layers two
molecules thick) with hydrophilic groups exposed to water
molecules both outside the vesicle and in the core. There is much
interest in these self-organizing systems, and various methods
have been developed to examine the structure and interactions of
such bilayers. Several fluorescent organic molecules have been
described as molecular probes of structural and dynamical changes
in lipid bilayers, the changes usually observed by monitoring the
variation of photophysical properties such as fluorescence
anisotropy, fluorescence lifetime, spectral position, and
fluorescence quantum yield of the dye within the bilayers.
Recently, molecules showing excited-state proton transfer
reactions have been suggested as probes for the study of protein
conformation and binding-sites. ... ... Mateo and Duhal (2
installations, ES) report a new molecular probe, 2-(2'-
hydroxyphenyl)imidazo[1,2-a]pyridine, denoted as HPIP, for
monitoring structural changes in lipid bilayers. Migration of
HPIP from water into vesicles involves rupture of hydrogen bonds
with water and formation of an internal hydrogen bond once the
probe is inside the vesicle. These structural changes of the dye
allow a photo-induced intramolecular proton-transfer reaction and
a subsequent twisting/rotational process upon electronic
excitation of the probe. Because the fluorescence of aqueous HPIP
external to the vesicle apparently does not interfere with the
emission of the probe within the vesicles, the technique allows
the monitoring and quantification of structural changes within
bilayers. The authors suggest the static and dynamic fluorescence
parameters in this technique are sensitive enough to such changes
to make this photostable dye a potential molecular probe of the
physical properties of lipid bilayers of significance in various
fields of research.
QY: Abderrazzak Douhal 
(Proc. Natl. Acad. Sci. US 23 Jun 98 95:7245)
(Science-Week 17 Jul 98)


7. PREBIOTIC ORGANIC COMPOUNDS: OCEANIC PROTECTION FROM SOLAR UV
It is generally believed that the Earth's primitive atmosphere
lacked oxygen, and therefore that an ozone layer protective
against ultraviolet radiation did not exist. This is considered
to be a serious problem for the accumulation of prebiotic organic
compounds on Earth and on Mars, and this problem would have been
worsened by the theoretically expected elevated ultraviolet
radiation production of the early Sun. Protection from
ultraviolet radiation is one of the motivations for proposing an
origin of life in submarine vents, benthic regions, and in deep
subsurface environments. Most attempts to deal with this problem
have involved atmospheric absorbers such as H(sub2)S, SO(sub2),
S(sub8), and organic hazes. ... ... Cleaves and Miller
(University of California San Diego, US) present an analysis of
the problem and report that even in the absence of atmospheric
shielding there would have been sufficient ultraviolet absorbers
in the ocean to allow for the accumulation of organic material.
These absorbers include organic polymers from electric discharges
and hydrogen cyanide polymerizations, solubilized elemental
sulfur, and inorganics such as Cl(-), Br(-), Mg(2+), SH(-),
Fe(2+). Complete ultraviolet protection could also be provided by
a frozen ocean, an oil slick, or large amounts of organic foams.
The authors suggest that oceanic ultraviolet protectors increase
the size of planetary habitable zones and thereby increase the
number of planets on which life may have arisen.
QY: Stanley L. Miller 
(Proc. Natl. Acad. Sci. US 23 Jun 98 95:7260)
(Science-Week 17 Jul 98)


8. FOSSILS OF TWO NEW FEATHERED DINOSAURS
The origin of birds has been much in the news these past 2 years
because of new fossil discoveries in China. Kevin Padian
(University of California Berkeley, US) presents a short review
of the most recent findings of Ji et al (4 authors at 3 install-
ations, CN CA US). Padian makes the following points: 1) Among
all living creatures, only birds have feathers. The discovery of
a single isolated feather in the mid 19th century in Late
Jurassic rocks of Bavaria was enough to demonstrate the remote
ancestry of birds (approximately 150 million years ago). The
discovery of the skeleton of Archaeopteryx in the same area in
1861 confirmed the idea of a feathered ancestor of birds, but
little else in the skeleton appeared related to living birds. 2)
Ji et al now describe two small theropod dinosaurs from
geological beds in the Liaoning province of China, the age of the
beds disputed but apparently Late Jurassic/Early Cretaceous
(about 145 million years ago). These theropods have down-like and
vaned barbed feathers on the body, arms, legs, and tail. But
these animals were clearly not birds, and they were clearly not
capable of flight. 3) If these are true feathers -- and the
evidence indicates they are indeed true feathers -- we are forced
to revise our idea of the association of feathers with the
animals we call birds. 4) By admitting that plumage did not first
spring full-blown on the wings of Archaeopteryx, we are free to
examine how feathers evolved in the first place. 5) The evolution
of carnivorous dinosaurs through basal (relatively "primitive")
*coelurosaurs into birds shows some unmistakable trends in the
morphology of wishbones, breastbones, hollow bones, long arms,
hands, etc. 6) Padian concludes: "The work of Ji et al should lay
to rest any remaining doubts that birds evolved from small
coelurosaurian dinosaurs. These new discoveries will excite the
public and scientists alike by showing that down-like and later
vaned body feathers evolved before flight feathers, and that a
full complement of feathers was present in coelurosaurs before
birds were invented."
QY: Kevin Padian 
QY: Philip J. Currie 
(Nature 25 Jun 98 393:729,753) (Science-Week 17 Jul 98)

-------------------

Related Background:

... ... *coelurosaurs: These are a group of relatively small and
lightly built dinosaurs in the suborder Theropoda having long
necks and narrow pointed skulls.

-------------------

Related Background:

ON THE ORIGINS OF BIRDS AND BIRD-FLIGHT
In paleontology, the theropods are dinosaurs with four or fewer
toes on the hind feet, a suborder of bipedal reptiles that first
appeared in the Upper Triassic period (about 215 million years
ago) and culminated in the Upper Cretaceous period (about 70
million years ago). A difficult problem in paleontology has been
the tracing of the evolution of birds, with most paleontologists
believing birds evolved from dinosaurs. The first feathered bird-
like fossils are classified as Archaeopteryx and were found in
Upper Jurassic deposits dating at about 150 million years ago,
but unfortunately there are no feathered intermediates yet dis-
covered between these fossils and any dinosaur ancestors. Birds
are rather unique in several aspects: feathers, toothless beaks,
hollow bones, perching feet, etc., with a combination of skeletal
features unknown in other living animals. ... ... Padian and
Chiappe (2 installations, US), in a review of extant data and the
controversies concerning the evolution of birds, conclude there
is no reasonable doubt that all groups of birds, living and
extinct, are descended from small meat-eating therapods, and that
"in fact, living birds are nothing less than small, feathered,
short-tailed therapod dinosaurs."
QY: Kevin Padian, Univ. of Calif. Berkeley 510-642-5130.
(Scientific American February 1998) (Science-Week 23 Jan 98)

-------------------

Related Background:

THERAPOD DINOSAURS AND THE ORIGIN OF FEATHERS
Chen et al (3 authors at 3 installations, CN) describe two nearly
complete skeletons of a small therapod dinosaur,
Sinosauropteryx.
The specimen has the longest tail of any known therapod, a 3-
fingered hand dominated by the first finger, and integumentary
structures that could be related to the origin of feathers. The
larger specimen has stomach contents and two eggs in the abdomen.
The authors suggest the integumentary structures indicate that
avian feathers may have evolved from simpler branched structures
appearing in non-avian therapod dinosaurs, possibly for
insulation.
QY: Pei-ji Chen 
(Nature 8 Jan 98) (Science-Week 23 Jan 98)

-------------------

Related Background:

FOSSIL EVIDENCE LINKS BIRDS AND DINOSAURS
Most paleontologists agree that birds are descendants of
dinosaurs, but the precise linkage is still to be determined,
and many questions remain. Now paleontologist Fernando Novas
(Museo Argentino de Ciencias Naturales, Buenos Aires AR) has
unveiled a reconstruction of a 90 million year old fossil of a
meat-eating dinosaur found in Argentina, the most birdlike
dinosaur ever discovered. The fossil's structure provides a link
between dinosaurs and birds, and will help explain how dinosaur
limbs evolved into bird wings. The creature was almost four feet
tall at the hip, and nearly seven feet long. It has been named
Unenlagia comahiensis.
(Nature 22 May 97)

-------------------

Related Background:

NEW FOSSIL EVIDENCE FUELS BIRD-DINOSAUR LINKAGE DEBATE
Paleobiologists continue to debate whether birds evolved from
dinosaurs or from earlier reptiles. This week Jose L. Sanz et al
(Autonomous University of Madrid ES, Smithsonian Institution,
Washington DC US, University of Barcelona ES) report the
discovery, in the Pyrenees of northern Spain, of a well-preserved
nestling bird dating from approximately 135 million years ago,
the specimen the earliest hatchling bird yet discovered,
apparently existing only 10 million years after Archaeopteryx,
considered the first undisputed bird. The hatchling is reported
to show a mix of primitive and advanced features, and is the
second claimed bird-dinosaur link in two weeks. Those who dispute
the bird-dinosaur link, however, say the hatchling provides no
evidence one way or the other. But partisans on both sides of the
issue admit this is an important find because it is indeed a
hatchling.
(Science 6 Jun 97)


9. MECHANISMS OF TUMOR SUPPRESSOR GENES
Cancer is fundamentally a genetic disease in which damage to
cellular DNA leads to disruption of the normal mechanisms that
control cellular proliferation. ... ... Ellisen and Haber (2
installations, US) review current knowledge concerning the genes
targeted in human cancer, and they make the following points: 1)
In general, cancer genes have been divided into 2 classes, proto-
oncogenes and tumor suppressor genes. 2) Proto-oncogenes are
genes that sustain activating changes in human cancer. These
changes may take the form of point mutations or gene
rearrangements that lead to increased or uncontrolled activity of
the encoded protein, or they make take the form of gene
amplification, which results in increased levels of protein
expression. 3) Tumor suppressor genes are characterized by
inactivating changes in human cancer, typically point mutations
that result in truncation or functional inactivation of the
encoded protein, or gross deletions of chromosomal fragments
carrying these genes. 4) Tumor suppressor genes are of particular
interest in cancer genetics because they are the genes most
commonly associated with hereditary predisposition to cancer. In
cases where familial cancer is linked to inheritance of a mutant
allele of a tumor suppressor gene, inactivation of the remaining
wild-type allele of that gene constitutes the critical genetic
event that initiates the development of cancer. 5) Although much
attention has focused on the initial tumor suppressor gene
mutation that initiates malignant transformation, cancer actually
results from the accumulation of a large number of genetic
events, both in tumor suppressor genes and in proto-oncogenes.
The authors tabulate 14 selected different tumor suppressor
genes, indicating the related familial syndrome, the types of
sporadic tumors containing mutations of these genes, and the
presumed normal function (mechanism of action) of these genes.
Mutations of the tumor suppressor gene  have been found in
approximately 50 percent of all cancers. The authors conclude:
"As the understanding of genetic heterogeneity evolves,
population studies are likely to uncover the contribution of
common subtle genetic variations to the risk of developing
different types of cancer. Together with societal and ethical
guidelines on the use of such genetic information, the study of
mutations in tumor suppressor genes and of their role in cancer
predisposition may provide important clues to the clinical
management of human cancer."
QY: Leif W. Ellisen, Dana-Farber Cancer Institute, Boston, MA US.
(Science & Medicine Jul/Aug 1998) (Science-Week 17 Jul 98)

-------------------

Related Background:

EVIDENCE THAT BREAST CANCER GENE IS APOPTOSIS COACTIVATOR
In molecular biology, the term "transcription" refers to the
sequence of biochemical events producing the conversion of DNA
code to RNA code. Apoptosis is programmed cell death produced by
control mechanisms designed to destroy defective cells or cells
that must be discarded in the process of tissue differentiation.
Mutations of the gene {BRCA1} have been linked to 45% of the
cases of familial breast cancer, and to 80% to 90% of families
with both breast and ovarian cancer. ... ... Now Ouchi et al (5
authors at 4 installations, US) report that {BRCA1} stimulates
artificial and genomic entities that contain elements responsive
to the tumor suppressor protein p53, which is known to be
involved in apoptosis. The authors suggest their findings
indicate the gene {BRCA1} is involved in transcriptional
regulation and has a function as a p53 coactivator.
QY: Hidesaburo Hanafusa (saburo@rockvax.rockefeller.edu)
(Proc. Natl. Acad. Sci. US 3 Mar 98)
(Science-Week 2 Apr 98)

-------------------

Related Background:

NEW TECHNIQUE USES COMMON COLD VIRUS TO KILL TUMOR CELLS
Human cells have a suicide program that is triggered by a
protein (p53) when the cell's genetic machinery is damaged. Some
viruses possess a gene that inactivates the protein p53, which
enables them to use the cell's genetic apparatus to reproduce,
with the eventual death of the host cell. The common cold virus
(adenovirus) is one of these viruses. That is fact #1. Fact #2
is that in many kinds of tumor cells, their protein p53 has
become intrinsically inactivated. Fact #3 is that a strain of
adenovirus exists that has lost the p53 jamming gene. This
mutant adenovirus will therefore be lethal to tumor cells with
already inactivated p53, but not to ordinary cells. So Frank
McCormack and his colleagues (Onyx Pharmaceuticals, Richmond CA
US) injected the mutant strain of adenovirus into head and neck
tumors in patients who had failed to respond to surgery,
radiation, or chemotherapy, and they found significant
destruction of tumors in 25% of the patients. The mutant
adenovirus killed the tumor cells in these large, refractory
cancers. These are preliminary trials, but the beginning of
what may be an extremely important approach to cancer therapy --
the use of pathogens with a specificity for tumor cells. The
results were reported at the recent meeting of the American
Society of Clinical Oncology.
(New York Times 20 May 97

-------------------

Related Background:

EVIDENCE FOR RECEPTOR DECOYS IN APOPTOSIS
In the previous report, we mentioned tumor suppressor genes,
sequences of DNA that code for proteins that prevent or inhibit
the growth of tumors. One of these genes codes for a protein
called p53, and evidently the function of this protein, closely
studied in many laboratories, is to trigger an internal suicide
program after the DNA of a cell has been damaged by drugs or
radiation. The process is called apoptosis -- programmed cell
death -- and what is characteristic of many types of cancer cells
is that the gene that codes for p53 has been damaged, the damaged
gene replicated from one generation of cancer cell to another,
and in the resulting absence of the protein p53 no apoptosis
occurs. In other words, the program whose function is to elim-
inate cells with corrupted DNA has itself been corrupted, and an
important fail-safe mechanism has been destroyed. There are other
endogenous cytotoxic proteins beside p53. One of them is called
TRAIL (also called Apo2L), and it is quite remarkable in that it
apparently induces apoptosis of many transformed cancer cell
lines but not of normal cells, even though its receptor is
evidently present in both cell types. Reports this week by Guohua
Pan et al (University of Michigan, US; Human Genome Sciences,
Rockville MD US) and James P. Sheridan et al (Genentech, San
Francisco CA US) indicate that normal cells contain a decoy
receptor for TRAIL, the decoy receptor not activating apoptosis,
while cancer cells susceptible to TRAIL do not contain the decoy
receptor, only the receptor that does activate apoptosis. Why
this difference in receptors should exist, given the evolution
pressures on cancer cells, is a mystery. But there is some hope
now that if the complexities of these "death-domain" receptors
can be unraveled, means may be found to use the TRAIL receptors
in cancer cells to kill them.
QY: V. M. Dixit ; A. Ashkenazi 
(Science 8 Aug 97)

-------------------

Related Background:

MECHANISM OF ACTION OF TUMOR SUPPRESSOR PROTEIN P53
Tumor suppressor genes apparently code for proteins that either
prevent cell division or provoke cell death, and since the
molecular mechanisms involved in these events are of great
importance in current efforts in cancer research, all the
elements in the sequences are of significance. Apoptosis is the
name given to the programmed cell death provoked by the proteins
expressed by tumor suppressor genes. Kornelia Polyak et al (Johns
Hopkins University, US) have investigated the genes whose
transcription is activated by protein p53, perhaps the most
important tumor suppressor protein, and they present a model for
the mechanism of apoptosis produced by this protein. The model
involves the transcriptional induction of redox related genes,
the formation of reactive oxygen species, and finally the
oxidative degradation of mitochondrial components, this sequence
then culminating in the death of the cell.
QY: Kenneth W. Kinzler, Johns Hopkins Oncology Center, 424 N.
Bond St., Baltimore MD 21241 US.
(Nature 18 Sep 97) 


10. DRUG ADDICTION AND THE GLUTAMATE NEUROTRANSMITTER
Dopamine is an important neurotransmitter in the human brain, and
it has been implicated in several serious behavioral pathologies.
There is a dopamine hypothesis of depression, a dopamine
hypothesis of schizophrenia, and dopamine has also been
implicated in the reinforcing effects of psychostimulant drugs of
abuse such as cocaine and amphetamine. Another neurotransmitter,
glutamate, is a major excitatory amino acid neurotransmitter
accounting for an estimated 40 percent of all nerve signals in
the human brain, and involved in phenomena such as neural
development, learning, and memory formation. Glutamate is
ordinarily released under close cellular biochemical control and
reuptake, and in excess amounts it is an intense excitant of
nerve cells and potentially toxic. Glutamate is suspected as an
important contributor to the pathogenesis of a number of
neurodegenerative disorders, including amyotrophic lateral
sclerosis and parkinsonian dementia. The glutamate receptor is
the molecular site that mediates the actions of glutamate
neurotransmitters, and this receptor has been a focus of
intensive research and has been differentiated into N-methyl D-
aspartate (NMDA), kainate, and quisqualate subtypes. Neurons that
release glutamate are called "glutamatergic", and they have been
located in many important areas of the human brain. Until the
past few years, the study of the neurobiological basis of drug
addiction has focused on dopamine, but there is apparent growing
interest in the involvement of glutamate as a key neurotrans-
mitter. This was the focus of a recent meeting (May 3-5, 1998) at
the US National Institutes of Health in Rockville, Maryland (US),
at which evidence was presented that blockade of glutamate
transmission prevents behavioral sensitization in rats to
repeated doses of amphetamine or cocaine. Behavioral sensitiz-
ation, also called "reverse tolerance", is the development of
increased sensitivity to the effects of drugs such as
pyschostimulants, and its occurrence in animals is considered a
prime model for human drug abuse. The idea that glutamate
biochemistry and neurophysiology may play a key role in human
drug addiction is apparently exciting many researchers in the
field.
QY: Ingrid Wickelgren 
(Science 26 Jun 98 280:2045) (Science-Week 17 Jul 98)

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