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.

June 25, 1999 -- Vol. 3 Number 26

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If you give a 10 year old child a microscope or a
small telescope, and you return a week later to find
the child has dismantled the one to make the other,
then you know you have in your hands a creature called
"scientist" -- a doubter, an explorer, a potential
desperado in the fiefdoms of certainty.
-- Anonymous

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Contents of This Issue:

Letter to the Editor: On Snow's Two Cultures

1. On the Question of the Dangers of Science
2. On Quasars
3. On Neutrino Oscillations
4. Marine Viruses: Biogeochemical and Ecological Effects
5. Four Genomes Directing the Biology of a Single Organism
6. On Gene Therapy

In Focus: On Invertebrate Paleontology

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LETTER TO THE EDITOR: ON SNOW'S TWO CULTURES
Concerning the comments of the Editors of Scienceweek on the 
editorial in the journal _Nature_ re C.P. Snow and the Two
Cultures  (ScienceWeek 18 Jun 99), I agree with ScienceWeek.
During the final decades of this century, developed societies
have been, or are about to be, deprived of two major technologies
-- nuclear power and genetic engineering -- by means of single
issue politics and assessments of risks in error by many orders
of magnitude. A loss of the potential benefits of science at this
rate suggests the chasm envisaged by C.P. Snow has deepened and
widened these past 40 years as, ironically, the technology of
communications is being used to question the principles, and
indeed even the wisdom, of scientific enquiry. Whether science
will find it possible to fill that chasm by the dissemination of
ever more knowledge in the absence of an all pervading purpose
that goes beyond its mere acquisition is clearly open to
question. The present Editor of _Nature_ (successor to the former
Editor, John Maddox) apparently has yet to recognize the danger.

Dr. D.A.A. Fagandini
daaf@cerium.demon.co.uk

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1. ON THE QUESTION OF THE DANGERS OF SCIENCE
Lewis Wolpert (University College London, UK), in a "commentary"
article, considers the classic question whether science is
dangerous, the author making the following points:
     1) The idea that knowledge is dangerous is deeply embedded
in our culture. Indeed, Western literature is filled with images
of scientists meddling with nature with disastrous results.
Scientists are portrayed as a soulless group, unconcerned with
ethical issues.
     2) The social obligations that scientists have, as distinct
from those responsibilities they share with all citizens, come
from scientists having access to specialized knowledge of how the
world works, knowledge that is not easily accessible to others.
The obligation of scientists is to make public any social
implications of their work and its technological applications,
and to give some assessment of the reliability of their work. In
most areas of science, it matters little whether a particular
theory is right or wrong, but in some areas, such as human and
plant genetics, it matters a great deal.
     3) The most clear case of immorality in scientific research
was the eugenics movement. The scientific assumptions behind this
movement were crucial: that most human attributes (desirable and
undesirable) are inherited. The scientists concerned completely
failed to give an assessment of the reliability of their ideas or
sufficiently to consider the implications of their ideas. On the
contrary, and even more blameworthy, their conclusions seem to
have been driven by what they saw as desirable social
implications. In contrast, the Allied scientists who built the
atomic bomb behaved morally, and fulfilled their social
obligations by informing their governments about the implications
of atomic theory. The decision to build the bomb was taken by
politicians, not scientists.
     4) The very term "genetic engineering" conjures up the image
of Frankenstein and his monster. The media are aware of this and
often report what can be regarded as genetic pornography --
reports dressed up to titillate and frighten. Newspapers print
sensational and unjustifiable headlines such as the "Frankenstein
foods" idiocy surrounding genetically modified organisms in the
UK.
     5) Bioethics is a growth industry that purports to address
questions concerning the dangers to society posed by biological
science. But one should regard this field with caution, as
bioethicists have a vested interest in finding difficulties.
     6) Are there areas of research that are so socially
sensitive that they should be avoided, even proscribed? Once one
begins to censor the acquisition of objective knowledge, one is
on the most slippery edge of all. Scientists cannot easily
predict the social and technological implications of research, as
is demonstrated by numerous examples in the history of science
and technology.
     7) The author concludes: "National and international
councils that can assess the ethical issues relating to the
applications of science and promote public debate are no doubt
valuable. But one wonders what such a committee would have said
if the public had been offered a convenient form of transport,
but at the cost, in the United Kingdom alone, of more than 3000
lives per year, a quarter of a million injured and the untold
damage of pollution. Where are the car-ethicists?"
-----------
Lewis Wolpert: Is science dangerous?
(Nature 25 Mar 99 398:281)
QY: Lewis Wolpert [l.wolpert@ucl.ac.uk]
-------------------
Summary by SCIENCE-WEEK [http://scienceweek.com] 25Jun99


2. ON QUASARS
The radius of a *black hole depends upon how much matter has
fallen into the region 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 were first
discovered in 1963. Quasars are extremely luminous sources
radiating energy over the entire spectrum from x-rays to radio
waves, and 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. Quasar spectra show emission lines with extremely large
*redshifts, and these large redshifts are interpreted to mean the
redshifted quasars are at great distances and thus must be
superluminous. Active galactic nuclei are central regions of
galaxies in which considerable energy is generated by processes
apparently other than those operating in ordinary stars. It is
believed the energy may result from the accretion of material
into a massive black hole situated at the core of the galaxy, and
that observed quasars are associated with these active galactic
centers. Quasars are often found in galaxies that are distorted
or interacting with other galaxies, and the rapid flow of matter
into a central massive black hole could indeed produce so much
energy that the quasars would be visible at great distances. The
*look-back time to the most distant quasar is approximately 15
billion years, and it believed that quasars may represent an
early stage in the formation of galaxies. ... ... G. Mark Voit
(Space Telescope Science Institute, US) presents a review of
recent research concerning quasars, the author making the
following points:
     1) The current view is that quasars flourished from 2 to 4
billion years after the *Big Bang, a period during which many of
the present galaxies were still under construction. Since that
time, the number of quasars in the Universe has apparently
steadily declined, while galaxies have gradually matured. The
formation of stars is now much less vigorous, and galaxies appear
more settled than several billion years ago. If the decline of
quasars is indeed directly linked to the maturation of galaxies,
the detailed nature of the link remains unclear.
     2) Before the *Hubble Space Telescope, it was believed that
quasars resided mostly in *spiral galaxies because that is where
the majority of active galactic nuclei occur. But the Hubble
Space Telescope has revealed that quasars are also present in
*elliptical galaxies in numbers more than expected, and that in
general the host galaxies surrounding quasars appear to be
disturbed by collisions with other galaxies.
     3) According to the current consensus model for quasar
phenomena, supermassive black holes at the centers of galaxies
attract gas clouds from surrounding interstellar space. As these
clouds accumulate around the black hole, they settle into a
swirling disk that gradually circulates inward in an extremely
violent death spiral that involves gas clouds traveling at
velocities near the velocity of light. At such speeds, colliding
gas clouds are heated to millions of degrees, and the disk of gas
orbiting a supermassive black hole therefore grows extremely hot
and radiates enormous amounts of energy.
     4) The current best case for a supermassive black hole is
the galaxy known as M106 (NGC 4258). Radio telescope network
observations indicate the gas clouds in this galaxy orbit a dark
object weighing 36 million Suns, the orbits in nearly perfect
circles and only light-months in diameter. Either the object at
the focus is a black hole or it is something inconceivably
strange and totally unknown.
     5) Once created, black holes are virtually impossible to
destroy. If supermassive black holes indeed powered a multitude
of quasars approximately 10 billion years ago, these black holes
must still exist, and may be hidden at the centers of normal-
looking galaxies throughout the Universe. From the orbital speeds
of stars in our own Galaxy, it has been deduced that a mass
between 2 and 3 million Suns lies at the center of our Galaxy,
and the view is that this central object must be either a black
hole or something even more exotic.
     6) In conclusion, the author suggests that the interplay in
the near future between the study of quasars and ultra-deep
imaging surveys will solve some of the mysteries surrounding the
past epoch when the Universe was more actively under
construction.
-----------
G. Mark Voit: The rise and fall of quasars.
(Sky & Telescope May 1999)
QY: G. Mark Voit, Space Telescope Science Institute, 3700 San
Martin Drive, Baltimore, MD 21218 US.
-----------
Text Notes:
... ... *black hole: When the fuel of a star is exhausted, the
outward pressures may undergo a marked decrease relative to the
gravitational forces, with a resultant gravitational collapse. If
the terminal stages of star death, which may involve a "blow-
off" of a large amount of matter, leave a remnant star mass
greater than 3 solar masses, the ultimate gravitational collapse
is expected to 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.
... ... *redshifts: Redshift (symbol: z) is a lengthening of the
wavelengths of electromagnetic radiation from a source caused
either by the movement of the source (Doppler effect) or by the
expansion of the universe (cosmological redshift). Redshift is
defined as the change in wavelength of a particular spectral line
divided by the unshifted wavelength of that line. Large redshifts
imply large radial velocities (which imply large distances,
according to current cosmological theory), but at redshifts
greater than about 0.2 there is a relativistic divergence from a
linear relation. A redshift of 4.0 corresponds to an object
receding with a radial velocity 92% that of the velocity of
light. The largest astrophysical redshifts so far observed are of
the order of z = 4.9.
... ... *look-back time: In general, the time taken for light
from a distant object to reach the Earth.
... ... *Big Bang: The Big Bang theory is 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.
... ... *Hubble Space Telescope: The *Hubble Space Telescope,
named after the astronomer Edwin Hubble (1889-1953), was launched
from a space shuttle in 1990 into a 600-kilometer low-Earth orbit
and has been providing extensive imaging and spectroscopic
observations critical for the development of astronomy and
astrophysics. The new information has concerned hot stars,
stellar chromospheres and coronas, the interstellar medium,
galaxies and galactic clusters, quasars, etc. -- all of it
information uncorrupted by the Earth's atmosphere, which is the
problem for ground based telescopes.
... ... *spiral galaxies: A type of galaxy with bright arms of
stars, gas, and dust that extend in a spiral pattern from a
central hub. The arms of the spiral apparently contain young
stars, while the hub contains old stars.
... ... *elliptical galaxies: These are galaxies that have no
disc component, the shape varying from almost circular to narrow
ellipses. The stars within elliptical galaxies are predominantly
old stars. Elliptical galaxies display the greatest variation in
mass, ranging down to extreme dwarf galaxies (approximately
10^(6) solar-mass).
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 25Jun99
-------------------
Related Background:
ASTROPHYSICS: ELECTRON-POSITRON JETS FROM A QUASAR
The most luminous objects in the Universe are distant *quasars
and *active galactic nuclei. Some of these objects emit strongly
at radio wavelengths, the emission evidently powered by twin jets
of *plasma streaming at close to the speed of light from the
nucleus of the underlying galaxy. The core of such a nucleus is
believed to be a supermassive *black hole of 10^(8) to 10^(9)
solar-masses. The composition of the jet plasma has been an
unresolved issue ever since the discovery of the jets, but the
two main candidates for the composition are an ordinary plasma
consisting of protons and *relativistic electrons, and a "pair"
plasma consisting only of relativistic electrons and *positrons.
... ... J.F.C. Wardle et al now report the detection of
*circularly polarized radio emission from the jets of quasar
3C279. This quasar, at an apparent *redshift of z = 0.538, is one
of the most luminous objects in the sky from radio to gamma-ray
wavelengths, and is violently variable across the electromagnetic
spectrum. The authors propose that the observed circular
polarization is produced by *Faraday conversion, and following
certain assumptions concerning energy flux and energy
distribution, the authors demonstrate the implication of this is
that electron-positron pairs must be an important component of
the jet plasma of quasar 3C279. The authors further suggest that
similar detections in 3 other radio sources indicate that, in
general, *extragalactic radio jets are composed mainly of
electron-positron pairs.
-----------
J.F.C. Wardle et al (3 authors at Brandeis University, US)
Electron-positron jets associated with the quasar 3C279.
(Nature 1 Oct 98 395:457)
QY: J.F.C. Wardle [jfcw@quasar.astro.brandeis.edu]
-----------
Text Notes:
... ... *quasars: (quasi-stellar objects) Extremely luminous
sources radiating energy over the entire spectrum from x-rays to
radio waves, and which are apparently the oldest and most distant
astronomical objects known. Their cores are thought to be massive
*black holes.
... ... *active galactic nuclei: Central regions of galaxies in
which considerable energy is generated by processes other than
those operating in ordinary stars. The energy may result from the
accretion of material into a massive black hole situated at the
core of the galaxy.
... ... *plasma: A state of matter consisting of ions and
electrons moving freely. Stars, for example, consist of plasma.
Because a plasma is highly ionized, it can be affected by
external electrical and magnetic fields, and the charged
particles of the plasma interact electrically and magnetically.
... ... *black hole: 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.
... ... *relativistic electrons: This refers to electrons
traveling close to the speed of light.
... ... *positrons: The positron is the antiparticle of the
electron. It has a charge identical but opposite to that of the
electron, and a rest mass identical to that of the electron.
In general, antiparticles are homologs of elementary particles
but with opposite charge. Matter composed entirely of
antiparticles is called antimatter.
... ... *circularly polarized: Electromagnetic radiation involves
the propagation of both electric and magnetic forces, and at each
point in a light beam, there is a component electric field and a
component magnetic field, both of which oscillate in all
directions perpendicular to each other and to the direction in
which the beam is propagated. In plane-polarized light, the
component electric field oscillates as in ordinary light except
that the direction of oscillation is contained within a plane.
Likewise, in plane-polarized light, the component magnetic field
oscillates within a plane, the planes in question being
perpendicular. Circularly polarized light has a component
electric field that varies in direction but not in magnitude, so
that the field traverses a spiral path in either a clockwise or
counterclockwise direction.
... ... *redshift: Redshift (symbol: z) is a lengthening of the
wavelengths of electromagnetic radiation from a source caused
either by the movement of the source (Doppler effect) or by the
expansion of the universe (cosmological redshift). Redshift is
defined as the change in wavelength of a particular spectral line
divided by the unshifted wavelength of that line. Large redshifts
imply large radial velocities (which imply large distances,
according to current cosmological theory), but at redshifts
greater than about 0.2 there is a relativistic divergence from a
linear relation. A redshift of 4.0 corresponds to an object
receding with a radial velocity 92% that of the velocity of
light. The largest astrophysical redshifts so far observed are of
the order of z = 5.
... ... *Faraday conversion: This is a conversion of linear
polarization to circular polarization which can occur with
radiative transfer in an anisotropic plasma.
... ... *extragalactic radio jets: The term "extragalactic" here
means outside our own Galaxy. Inside our own galaxy, radio jets
are associated with protostars (embryonic stars) or microquasars
(small versions of ordinary quasars [see below]).
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 30Oct98
-------------------
Related Background:
ON QUASARS
... Michael Disney (University of Wales, UK) provides an
excellent review of the history and current status of quasar
research. Recent observations have led astronomers to the idea
that quasars are associated with massive galactic-center black
holes generating huge amounts of energy under special
circumstances. The author suggests that in terms of theory, we
need to understand how and when massive black holes form in the
first place. Did they precede or follow the formation of their
host galaxies? Secondly, we need a convincing physical model to
explain exactly how such black holes convert in-falling matter
into all the varieties of quasar radiation, from gamma rays to
superluminal radio jets, and the formulation of such a model may
not be easy. The author concludes with a quote by Carole Mundell
of the Jodrell Bank Observatory (UK): "Observing quasars is like
observing the exhaust fumes of a car from a great distance and
then trying to figure out what is going on under the hood."
QY: Michael Disney, University of Wales, Cardiff, UK.
(Scientific American June 1998) (Science-Week 5 Jun 98)
-------------------
Related Background:
ON MICROQUASARS IN OUR GALAXY
... Mirabel and Rodriguez (2 installations, FR MX) review the
accumulated evidence concerning microquasars in our Galaxy.
Microquasars mimic on a smaller scale many of the phenomena seen
in quasars, and their discovery opens the way for a new
understanding of the connection between the accretion of matter
onto black holes and the origin of the relativistic jets observed
in remote quasars. The repeated observation of two-sided moving
jets in microquasars has led to a much greater acceptance of the
idea that the emission from quasar jets is associated with
material moving at speeds close to that of light.
QY: I.F. Mirabel [mirabel@discovery.saclay.cea.fr]
(Nature 16 Apr 98 392:673) (Science-Week 8 May 98) 


3. ON NEUTRINO OSCILLATIONS
The fundamental particles of 20th century physics came into
existence as theoretical constructions designed to explain
certain specific experimental observations. In some cases, the
existence of a particular particle has been verified by direct
experiment; in other cases, the required verification experiments
are extremely difficult to accomplish, and the particles related
to these experiments have remained theoretical constructions.
The neutrino was first theoretically postulated by Wolfgang Pauli
(1900-1958) in 1930 in order to maintain the conservation of
energy principle in the analysis of the results of certain *beta-
decay experiments. The Pauli neutrino was a particle with no
charge and zero rest mass. Experimentally, the particle was
tentatively identified by F. Reines and C. Cowan in 1953 and more
definitely in 1956. Neutrinos are "leptons", which are a group of
point-like particles with *spin of 1/2 that are not affected by
so-called "*strong interactions" and that are not constructed of
*quarks. In the *Standard Model in particle physics, there are 6
particle types categorized as leptons: the electron, the *muon,
the massive *tau lepton, and a neutrino associated with each of
these (denoted as 3 neutrino "flavors" or "generations"). 
Neutrinos are produced in great numbers by the Sun, but they
almost never interact with atoms, and an estimated 10^(12) solar
neutrinos flow through our bodies each second without any
consequence. Measurements of solar neutrinos, however, have
produced a mystery: the neutrino density measured by detectors is
approximately one-third that expected from theoretical
calculations of solar neutrino emission. Two kinds of solutions
have been proposed to resolve this mystery, one solution
involving revisions to the theory of stellar structure, and the
other solution involving revisions to nuclear particle theory. In
the latter case, the proposal is that the neutrino may oscillate
among the 3 different flavors (states), with the result that
neutrino detectors detect only one flavor or one-third of the
solar emission. The existence of such neutrino oscillation would
have important implications, since it has been believed that
neutrinos, like photons, have zero mass. But theory indicates
that if neutrinos oscillate they must have mass, and neutrinos
are so numerous that even an extremely small mass would
theoretically be sufficient to affect the future of the Universe
as a whole. The question of neutrino oscillation, therefore, is a
critical problem affecting a good deal of fundamental physics and
cosmology, and there is recent evidence interpreted to indicate
that such oscillation does indeed occur and that neutrinos do
indeed have nonzero mass.
... ... K. Kaneyuki and K. Scholberg (2 installations, JP US)
present a detailed review of current research concerning neutrino
oscillations, the authors making the following points:
     1) The basic strategy for measuring neutrino oscillations is
simple. Given a source of neutrinos, either natural or
artificial, one allows the neutrinos to propagate for a known
distance, and then one obtains as much quantitative information
as possible concerning their energy and flavor. If the amount of
a given flavor, as a function of energy and distance, is that
expected from the quantum mechanical predictions arising from the
oscillation hypothesis, then neutrino oscillation has been
discovered.
     2) Three neutrino sources are currently used in research:
The Sun, atmospheric *cosmic-ray showers, and particle
accelerators. At present, the clearest neutrino oscillation
evidence from atmospheric neutrinos comes from the "Super-
Kamiokande" experiment, which observes neutrino interactions by
detecting *Cherenkov (Cerenkov) radiation. The Super-Kamiokande
experiment has been built and operated by a collaboration of
approximately 130 scientists from Japan and the US, the project
headed by Y. Totsuka (University of Tokyo, JP). The apparatus
consists of 50 kilotons of ultrapure water housed approximately
one kilometer underground in the Kamioka mine in Japan. The
detector consists of 2 concentric cylinders 40 meters high and
with an outer radius of 20 meters. The inner cylinder contains
11,146 inward-facing photomultiplier tubes, each 50 centimeters
in diameter. These photomultiplier tubes detect Cherenkov
radiation from particle interactions inside the inner cylinder
(which contains the ultrapure water). The outer cylinder has 1885
20-centimeter-diameter photomultiplier tubes facing outward to
check for non-neutrino related Cherenkov radiation from entering
charged particles (cosmic-ray muons and radioactivity). Super-
Kamiokande began operation on April 1, 1996.
     3) The essential basis of the Super-Kamiokande experiment is
as follows: When a high-energy cosmic-ray particle (e.g., a
proton) hits an atomic nucleus in the upper atmosphere, the
collision produces a shower of secondary particles. Some of these
particles decay to other particles, some of which are neutrinos.
Most of the charged particles produced in the shower lose energy
as they move through the atmosphere and into the Earth's surface.
Neutrinos, however, because of their extremely small rate of
interaction, pass through the atmosphere and the ground, the vast
majority penetrating to the other side of the Earth. But a few
neutrinos do interact (e.g., with the ultrapure water in the
Super-Kamiokande reservoir), and the Super-Kamiokande apparatus
can detect the interaction of approximately 8 neutrinos per day
in its inner volume.
     4) The authors conclude: "These are exciting times for
neutrino physics, and for elementary particle physics as a whole.
The atmospheric neutrino data fit the neutrino-oscillation
hypothesis beautifully, and this verification that at least some
neutrinos have mass is an enormous step forward: It is the first
clear indication of physics beyond the Standard Model."
-----------
K. Kaneyuki and K. Scholberg: Neutrino oscillations.
(American Scientist May-Jun 99 87:222)
QY: Kenji Kaneyuki, Dept. of Physics, Tokyo Institute of
Technology, JP.
-----------
Text Notes:
... ... *beta-decay: A type of interaction in which an unstable
atomic nucleus changes into a nucleus of the same mass number but
different proton number. The change involves the conversion of a
neutron into a proton with the emission of an electron and an
electron *antineutrino, or of a proton into a neutron with the
emission of a positron and an electron neutrino. The electrons or
positrons emitted are called "beta particles". (Positrons are
electron antiparticles. See *antineutrino.)
... ... *antineutrino: An antiparticle (antimatter) is a
subatomic particle that has the same mass as another particle and
equal but opposite values of some other property or properties.
For example, the antiparticle of the electron is the positron. An
antineutrino, the antiparticle to the neutrino, has zero mass,
*spin 1/2, and positive helicity. There are 2 antineutrinos, one
associated with the electron and one associated with the *muon.
... ... *spin: In quantum mechanics, "spin" is the intrinsic
angular momentum of a subatomic particle. Spin states are
quantized, multiples of h/2ã, where h = Planck's constant, and
each particle is characterized by a quantum spin number which is
the multiple factor.
... ... *strong interactions: According to the *Standard Model,
the fundamental forces comprise the gravitational force, the
electromagnetic force, the nuclear strong force, and the nuclear
weak force.
... ... *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.
... ... *Standard Model: In particle physics, the Standard Model
is a theoretical framework whose basic idea is that all the
visible matter in the universe can be described in terms of the
elementary particles leptons and quarks and the forces acting
between them.
... ... *muon: The 3 leptons (electron, muon, tau) differ from
each other only in mass. The muon is 200 times more massive than
the electron.
... ... *tau: (tauon) The mass of the tau particle is 3560 times
the mass of the electron.
... ... *cosmic-ray: Cosmic rays are highly energetic particles
moving at close to the speed of light and continuously bombarding
the Earth's atmosphere from all directions. The energies of the
particles are enormous and range from 10^(8) to over 10^(19)
electronvolts.
... ... *Cherenkov (Cerenkov) radiation: Discovered in 1934 by
Cerenkov (1904-1990), Cerenkov radiation is electromagnetic
radiation, usually bluish light, emitted by a beam of high-energy
charged particles passing through a transparent medium at a speed
greater than the speed of light in that medium. The radiation is
essentially a shock wave, the effect analogous to that of a sonic
boom.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 25Jun99
-------------------
Related Background:
THEORETICAL IMPLICATIONS OF NEUTRINO DEFICITS
Leptons are a class of point-like fundamental particles showing
no internal structure and no involvement with the strong forces.
There are 6 leptons: the electron, the muon, the massive tau
lepton, and a specific neutrino associated with each of the
former (3 neutrino "flavors"). An antilepton is an anti-particle
of a lepton, for example an antineutrino (an anti-particle of a
neutrino) or a positron (an anti-particle of an electron). The
term "lepton-number" refers to a conserved quantum number equal
to the number of leptons minus the number of antileptons in a
system, with the lepton-number conservation laws separately
individualized for each flavor. Neutrinos have zero charge,
possibly zero mass, and an angular momentum factor (spin) of 1/2.
Various processes produce neutrinos: stellar nuclear reactions,
reactions occurring during supernova explosions, cosmic ray
collisions with matter, etc., and installations have been
constructed to measure the flux of neutrinos impacting Earth. To
avoid contamination by cosmic rays, such installations are deep
underground. One such installation is the Kamioka mine in Japan,
which houses the Kamiokande detector, an emplacement of a large
volume of ultrapure water. One of the best sources of neutrinos
should be the nuclear reactions in our own Sun. At the present
time, the fluxes of neutrinos measured by various detector
installations have been no more than 60% of that predicted by
theory, particularly in the case of solar neutrinos, and the
deficits are a puzzle. One possibility is that since current
detectors measure only one lepton flavor, the deficits may be a
result of neutrinos oscillating (converting) from one flavor to
another, which would imply neutrinos have mass. Another
possibility is that there is something wrong with the current
theory of stellar nuclear reactions or with the current theory of
fundamental particles. ... ... F. Wilczek (Instit. for Advanced
Study Princeton, US), reviewing discussions at a recent neutrino
conference (Santa Barbara, Calif. US, 2-6 Dec 97), notes the
anomalies and contradictions produced by current neutrino
research, particularly the anomalies in cosmic ray neutrino
flavor ratios reported by the SuperKamiokande detector, and
suggests that it seems probable the separate laws of lepton-
number conservation will soon fall.
QY: Frank Wilczek  (Nature 8 Jan 98)


4. MARINE VIRUSES: BIOGEOCHEMICAL AND ECOLOGICAL EFFECTS
Viruses are small particles, usually 20 to 200 nanometers in
their largest dimension, and their unique properties set them
apart from all living creatures. Heterogeneity among viruses is
ensured by their dependence upon a host for replication. Host-
virus interactions tend to be highly specific, and the biologic
range of viruses mirrors the diversity of potential host cells.
Further diversity of viruses is exhibited by their broad array of
strategies for replication and survival. Essentially, a viral
particle consists of a nucleic acid molecule, either DNA or RNA,
enclosed in a protein coat (capsid). The capsid proteins
determine the specificity of interaction of a virus with its host
cell, the capsid both protecting the nucleic acid and
facilitating attachment and penetration of the host cell by the
virus. Once inside the cell, viral nucleic acid redirects the
enzymatic machinery of the host to functions associated with
replication of the virus. In some cases, genetic information from
the virus is incorporated as DNA into the host genome. In other
cases, viral genetic information outside the host genome serves
as a basis for cellular manufacture and release of copies of the
virus. In both cases, complete replication of a virus is a
process which requires replication of viral nucleic acid and
production of specific viral proteins. Maturation consists of the
assembly of newly synthesized nucleic acid and protein subunits
into mature viral particles which are then liberated into the
extracellular environment. In general, there are two types of
viral release from the host cell: in one type the host cell is
destroyed by the process and all the intracellular viral
particles are released at once; in the second type of release,
viral particles are released over several generations,
translocated through the host cell membrane by extrusion or
budding, the continuing translocation and release leaving the
host cell viable. ... ... Jed A. Fuhrman (University of Southern
California, US) presents an extensive review of marine viruses
and their biogeochemical and ecological effects, the author
making the following points:
     1) Viruses are consistently the most abundant biological
entities in the sea -- nearshore and offshore, tropical to polar,
sea surface to sea floor, and in sea ice and sediment pore water.
Viral abundances are typically 10^(10) per liter in surface
waters (approximately 5 to 25 times the bacterial abundance), and
follow the same general location abundance patterns as bacteria.
     2) One of the reasons biological oceanographers first looked
for abundant viruses was a missing sink apparently associated
with excess bacterial production. In the decade since the
discovery of high viral abundance, several lines of evidence have
converged to the conclusion that viruses are significant agents
in both the mortality of aquatic microbes and in the
restructuring of aquatic communities.
     3) Probably the most uncertain aspect of marine viruses is
their role in genetic exchange among microorganisms, and the
effect of this on short term adaptation, population genetics, and
evolution. Direct effects would involve transduction, in which a
virus picks up DNA from one host and transfers it to another
host. The overall effect over large scales of space and time
would be to homogenize genes among the susceptible host
populations. An indirect effect might involve the release of free
DNA from the host organism by viral lysis (destruction of the
host cell upon release of new replicated viruses), with this free
DNA transferred to other organisms through natural
*transformation. Dissolved DNA is in fact readily found in sea
water, and it has been reported that viral lysis may be a major
source mechanism. These two processes, generalized viral
*horizontal gene transfer and transformation, would have the
effect of mixing genes among a broad variety of species, with
wide-ranging effects on adaptation and evolution. The author
suggests these considerations should be included in the
evaluation of the potential spread of genetically engineered
microbial genes, or of the spread of antibiotic resistance
introduced by the use of antibiotics in intensive fish farming.
     4) The author suggests the principal conclusion concerning
marine viruses is that these viruses can exert significant
control on marine bacterial and *phytoplankton communities, with
respect to both biological production and species composition,
influencing the pathways of matter and energy transfer in the
marine system.
     5) The author concludes: "New molecular methods that enable
the diversity of viruses and their hosts to be studied within
their natural habitats will make it easier to unravel the complex
web of interactions in marine communities."
-----------
Jed A. Fuhrman: Marine viruses and their biogeochemical and
ecological effects.
(Nature 10 Jun 99 399:541)
QY: Jed A. Fuhrman [fuhrman@usc.edu]
-----------
Text Notes:
... ... *transformation: Biologists recognize two types of gene
transfer from one organism to another: vertical and horizontal.
Vertical gene transfer occurs between parents and offspring, and
horizontal gene transfer is the transfer that may occur between
organisms otherwise. It is in bacteria that horizontal gene
transfer has been studied most extensively, particularly in the
last decade. Three types of horizontal gene transfer exist:
conjugation, transduction, and transformation. Conjugation is a
type of sexual reproduction exhibited by some bacteria, the
process involving the exchange of genetic material by means of a
tube or bridge, the transfer of DNA occurring either in one
direction or in both directions. Transduction involves the
transfer of genetic material from one bacterium to another with
the intermediation of a virus. Essentially, when the virus
infects one bacterium, it often carries away pieces of that
bacterium's genome, and those pieces, upon the infection of a new
bacterium, become incorporated into another genome. Finally,
transformation is the process involving the uptake or
incorporation of DNA fragments (or plasmids) by a bacterium,
first observed in 1944 by Oswald Avery. Transformation is a
common laboratory technique used in genetic engineering. One
significant aspect of these modes of horizontal bacterial gene
transfer is that in principle they make possible the horizontal
gene transfer of genetic material from genetically engineered
bacteria to other organisms without predictable results. So if
genetically engineered bacteria are to be widely used in
industry, for example, it is of some importance to have a
thorough understanding of the mechanisms in order to limit any
harmful ecosystem transfer effects.
... ... *horizontal gene transfer: See previous note.
... ... *phytoplankton: (photoplankton) Small, usually
microscopic, aquatic plants capable of photosynthesis; e.g.,
unicellular algae. Phytoplankton and plankton are not equivalent.
The term "plankton" is a general designation for various drifting
microscopic aquatic organisms in the upper regions of the oceans,
both photosynthetic and non-photosynthetic.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 25Jun99
-------------------
Related Background:
ON THE CHEMISTRY AND BIOLOGY OF THE OCEANS
The combination of vast areas of liquid water on its surface
together with a high concentration of free molecular oxygen in
its atmosphere is unique to Earth in this solar system.
Calculations based on *ultraviolet absorption cross sections
indicate that whereas direct photolysis of water could have
produced small amounts of O(sub2), almost all of the gas was
produced by biological systems through the photobiologically
catalyzed oxidation of the liquid. ... ... Falkowski et al (3
authors at 3 installations, US DE) review the controls and
feedbacks between oceanic *phytoplankton and geochemical
processes with an emphasis on factors that cause a deviation from
the steady state. The authors make the following points: 1)
Changes in oceanic primary production, linked to changes in the
network of global biogeochemical cycles, have profoundly
influenced the geochemistry of Earth for over 3 billion years. 2)
In the contemporary ocean, photosynthetic *carbon fixation by
marine phytoplankton leads to the formation of approximately 45
gigatons of organic carbon per year, of which 16 gigatons are
exported to the ocean interior. 3) Changes in the magnitude of
total and export production can strongly influence atmospheric
CO(sub2) levels (and hence climate) on geological time scales, as
well as set upper bounds for sustainable fisheries harvest. 4)
Because the average turnover time of phytoplankton carbon in the
ocean is on the order of a week or less, total and export
production are extremely sensitive to external forcing, and
consequently are seldom in steady state. 5) Elucidating the
biogeochemical controls and feedbacks on primary production is
essential to understanding how oceanic biota responded to and
affected natural climate variability in the geological past, and
to understanding how oceanic biota will respond in the coming
decades to changes influenced by human activities.
QY: Paul G. Falkowski 
(Science 10 Jul 98 281:200) (Science-Week 31 Jul 98)
-------------------
Related Background:
... ... *ultraviolet absorption cross sections: The ratios of the
amount of energy removed from incident UV by absorption to the
total energy of incident UV. In other words, in this context, a
measure of how much energy is (was) actually available for direct
photolysis of liquid water.
... ... *phytoplankton: Also called photoplankton. Small, usually
microscopic, aquatic plants capable of photosynthesis; e.g.,
unicellular algae. Phytoplankton and plankton are not equivalent.
The term "plankton" is a general designation for various drifting
microscopic aquatic organisms in the upper regions of the oceans,
both photosynthetic and non-photosynthetic.
... ... *carbon fixation: Refers to the process of converting the
carbon in a substance into a form usable by an organism. For
example, the conversion of the carbon in CO(sub2) into organic
carbon (the carbon in organic compounds).
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 31Jul98


5. FOUR GENOMES DIRECTING THE BIOLOGY OF A SINGLE ORGANISM
Intracellular *symbiosis (endosymbiosis) is considered the most
sophisticated association between eukaryotes (cells with internal
membrane-bound organelles) and intracellular microorganisms.
Endosymbiosis implies the coordination between associated genomes
to form a new entity, sometimes called the "symbiocosm". In
insects, endosymbiosis often involves specialized adaptations.
Furthermore, insect endosymbionts are often involved in several
metabolic pathways of the host, and most insect endosymbionts
cannot divide by themselves in vitro. Endosymbiosis in insects is
generally considered to be *mutualistic, but the consensus is
that insect endosymbiosis exhibits a spectrum ranging from
parasitic to mutualistic relationships.
... ... A. Heddi et al (5 authors at Institut National des
Sciences Appliquees Villeurbanne, FR) now report that cell
physiology in certain cells of the weevil Sitophilus oryzae is
coordinated by 4 integrated genomes: the nuclear genome, the
*mitochondrial genome, the genome of a principal endosymbiont,
and the genome of a secondary endosymbiont. The principal
endosymbiont, whose endosymbiotic existence in the weevil was
recognized as long ago as 1927, is a *gamma-proteobacterium,
present at densities of approximately 2000 bacteria per cell in
"bacteriocytes" (specialized insect fat cells containing
endosymbiotic bacteria). The 4th endosymbiont, discovered by the
authors in 3 species of weevil, is an alpha-proteobacterium
(Wolbachia) disseminated throughout body cells and in
particularly high density in reproductive cells. The principal
endosymbiont is apparently fully integrated into the physiology
of the host, induces the specific differentiation of
bacteriocytes, and increases mitochondrial oxidative
phosphorylation by supplying pantothenic acid, riboflavin, and
biotin, and by increasing mitochondrial enzymatic activity,
apparently enhances the flight ability of adult insects. In
contrast, neither the presence nor the absence of the secondary
endosymbiont apparently affects the physiology of the weevil,
although certain genetic effects of the organism are evident
under special experimental circumstances and suggest an
involvement in the *speciation of the weevil. The secondary
weevil endosymbiont is a *rickettsia-like organism widespread in
*arthropods and is known to alter host reproduction and to be
possibly virulent and lethal in the fruit fly Drosophila. In the
weevil, however, the presence of this secondary endosymbiont is
apparently innocuous. The authors suggest the coexistence of 2
distinct types of intracellular proteobacteria at different
levels of endosymbiont integration in insects illustrates the
genetic complexity of animal tissue. The authors further suggest
an inferred evolutionary timing: first nucleocytoplasm, then
mitochondria, then the principal endosymbiont, and finally the
secondary endosymbiont, a scenario consistent with the "*serial
endosymbiotic theory". The authors suggest that symbiogenesis,
the genetic integration of long-term associated members of
different species, appears in the weevil to involve a mechanism
for speciation (in the case of the secondary endosymbiont) and a
mechanism for the acquisition of new genes for improved
environmental adaptation (in the case of the principal
endosymbiont).
-----------
Editor's note: In addition to the related background material
below, see the SW issue of 18 Jun 99, report #3: "Mitochondrial
Evolution".
-----------
A. Heddi et al: Four intracellular genomes direct weevil biology:
Nuclear, mitochondrial, principal endosymbiont, and Wolbachia.
(Proc. Natl. Acad. Sci. US 8 Jun 99 96:6814)
QY: Abdelaziz Heddi [heddi@insa.insa-lyon.fr]
-----------
Text Notes:
... ... *symbiosis: In biology, the term "symbiosis" refers to
any intimate and protracted association of individuals of
different species.
... ... *mutualistic: Mutualism is a type of symbiosis in which
both participants receive benefits from the association.
... ... *mitochondrial genome: Mitochondria are double-membrane
enclosed organelles of cells that are involved with several
important biochemical pathways, including electron transport and
oxidative metabolism. Various types of eukaryotic cells may
contain from a few to several thousand mitochondria in each cell
type. The mitochondria are relatively large cylindrical
structures up to 10 microns long and up to 2 microns in diameter,
and they are believed to have originated as organisms that became
symbiotic with eukaryotic cells.
... ... *gamma-proteobacterium: Proteobacteria are a general
category comprising a large number of diverse forms. At present,
the various subtypes of proteobacteria are classified according
to DNA sequences, and the classification scheme will no doubt
change in the future as the various genomes are more fully
sequenced.
... ... *speciation: In general, the evolutionary formation of
new species.
... ... *rickettsia: Small bacteria that are obligate
intracellular parasites. Most human rickettsial diseases (e.g.,
typhus) are transmitted by *arthropods.
... ... *arthropods: The largest phylum in the animal kingdom in
terms of both number of taxa and biomass. In general, arthropods
are bilaterally symmetrical and metamerically segmented. Thirteen
classes are recognized, including insects, centipedes, ticks,
spiders, etc.
... ... *serial endosymbiotic theory: As usually described, this
theory postulates that mitochondria and certain other cell
organelles are the direct descendants of bacterial endosymbionts
that became established at an early stage in a nucleus-containing
host cell without such entities.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 25Jun99
-------------------
Related Background:
ORIGIN OF A CHLOROPLAST PROTEIN IMPORTER
In general, photosynthesis is the utilization of light energy to
power biosynthesis, and chloroplasts are the plant cell
organelles in which photosynthesis occurs, the chloroplasts
containing several photosynthetic pigments (chlorophylls).
Chloroplasts are found in all photosynthetic plant cells, but not
in photosynthetic prokaryotes (i.e., not in cells without
membrane-bound organelles). The typical higher plant chloroplast
is lens-shaped, approximately 5 microns across the larger
dimension, and the number of chloroplasts per cell can vary from
1 to 100 depending on the type of cell. A mature chloroplast is
typically bounded by two membranes, an inner membrane and an
outer membrane, the membranes possessing significantly different
chemical constituents. In addition to a number of enzymes
involved in photosynthesis, chloroplasts also contain in their
interior a circular DNA molecule and protein synthetic machinery
typical of prokaryotes. The current consensus is that
chloroplasts may have originated from *cyanobacteria that became
*endosymbionts, an origin similar to that of mitochondria, which
are believed to have originated from so-called "*purple
bacteria". During evolution, chloroplasts (like mitochondria)
have apparently relinquished the majority of their genes to the
host nucleus, since chloroplast DNA codes only for some of the
proteins required by chloroplasts. The protein products of such
transferred genes are evidently imported into chloroplasts with
the help of biochemical import machinery distributed across the
inner and outer chloroplast membranes. The evolutionary origin of
this machinery is considered a puzzle, since the two bounding
membranes of the cyanobacteria have exhibited no functionally
similar protein import system. Recently, however, in the genome
of a species of cyanobacteria (Synechocystis), an apparent gene
(an "*open reading frame") has been identified that codes for an
amino acid sequence that shares an approximate 22 percent amino
acid identity with a protein-transporting channel in the outer
envelope of pea chloroplasts. ... ... B. Bolter et al (5 authors
at 2 installations, DE) now report that the protein coded by the
open reading frame of the Synechocystis cyanobacterium is located
in the outer membrane of that organism (the lipopolysaccharide
layer), and apparently transports polyamines and peptides. The
authors suggest their results indicate that a component of the
chloroplast protein import system may have been recruited from a
preexisting channel-forming protein of the cyanobacterial outer
membrane, and that in addition the presence of a protein in the
chloroplast outer envelope which is *homologous to a
cyanobacterial protein provides support for the general
prokaryotic nature of the outer membrane of chloroplasts.
-----------
B. Bolter et al: Origin of a chloroplast protein importer.
(Proc. Natl. Acad. Sci. US 22 Dec 98 95:15831)
QY: Jurgen Soll [jsoll@bot.uni-kiel.de]
-----------
Text Notes:
... ... *cyanobacteria: A phylum of bacteria characterized by
blue-green (cyan) photosynthetic pigments, abundant in a variety
of habitats, particularly in fresh water and soil. Cyanobacteria
are responsible for generating a large portion of the free oxygen
in the Earth's atmosphere. They apparently produced stromatolite
limestone deposits, as well as the bulk of modern petroleum
deposits. (Stromatolites are laminated calcareous microbial
fossil deposits formed principally by cyanobacteria and algae.)
... ... *endosymbionts: Endosymbiosis is an arrangement in which
one organism lives inside another organism, but the term is
usually restricted to arrangements of mutual benefit, thus not
including parasite-host relationships. A number of eukaryotic
cell organelles (including mitochondria) are believed to have
originated from endosymbiotic relationships between eukaryotic
cells and simpler cells.
... ... *purple bacteria: Specifically, any of the various
photosynthetic bacteria that contain bacteriochlorophyll, and are
thus distinguished by purplish or reddish-brown pigments. But the
term "purple bacteria" is sometimes used as a synonym for the
phylum Proteobacteria, a general category comprising a large
number of diverse forms.
... ... *open reading frame: The term "reading frame" refers to a
specific permutation of nucleotide triplets in DNA as "framed" by
a preceding start triplet (start codon), and an open reading
frame is any DNA sequence of triplets that potentially encodes a
protein.
... ... *homologous: In this context, the term refers to similar
sequences of amino acids in two proteins.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 26Mar99


6. ON GENE THERAPY
At the present time, more than 200 clinical trials of gene
therapy are apparently in place worldwide, with hundreds of
patients enrolled, but there is still not a single case of gene
therapy that can be called an unequivocal success. The major
problem is evidently gene delivery, getting the therapeutic gene
or genes or bits of DNA into cells in a way such that the new
genetic materials will be allowed to express their proteins in an
enduring cellular environment. There are basically two methods
for gene delivery, viral and non-viral, and neither method has
yet proved satisfactory. Success with either method, absent some
serendipitous laboratory or clinical discovery, will most likely
depend on further basic research. ... ... Eric B. Kmiec (Thomas
Jefferson University, US) presents a review of current
difficulties in gene therapy strategies, the author making the
following points:
     1) Most of the gene therapy techniques developed so far are
of the gene-addition variety, an attempt to provide a good copy
of a gene to cells that harbor bad copies of the gene. To date,
the results of clinical trials involving these techniques have
been disappointing. Even the most successful clinical trials has
fallen short of therapeutic efficacy.
     2) Many of these clinical trials may have been conducted
before the technology was fully mature, driven in part by
investor demands on biotechnology companies to rush products to
market. Such clinical trials were almost certainly destined to
fall short of the mark.
     3) Making gene therapy a successful endeavor will require
careful research to understand why traditional approaches have
not produced the hoped for results and, in turn, to improve them,
while exploring new ways to deal with genetic defects.
     4) In spite of increased government scrutiny of previous
gene-therapy protocols, the pressures to bring gene therapy to
the clinic do not seem to abate. This is in part because of the
formation of ventures aimed at commercializing products and
techniques. Financial pressures and constraints often force
biotechnology companies to forgo basic research in favor of
application-driven development. Unfortunately, the result is that
promising but technically difficult approaches may never be
adequately developed for lack of research funding.
     5) Increases in public funds for research may be part of the
answer to improving the technology. What is clearly needed is the
development of molecular analysis and rigorous testing at the
level of basic science, with an eye towards application in
clinically appropriate targets. Only then will gene therapy have
a hope of fulfilling its promise.
     6) The author suggests that pronouncements of gene therapy's
imminent demise are as premature as were the overly optimistic
pronouncements of its imminent success. At its core, the notion
of gene therapy or gene correction is scientifically sound and
commitment to programs of research must be maintained.
-----------
Eric B. Kmiec: Gene therapy.
(American Scientist May/Jun 1999 87:240)
QY: Eric B. Kmiec [kmiec@lac.jci.tju.edu]
-------------------
Summary by SCIENCE-WEEK [http://scienceweek.com] 25Jun99
-------------------
Related Background:
ON HUMAN GENE THERAPY
... W. Anderson (University of Southern California, US) reviews
the status of the field and the difficulties that have delayed
advances, the author making the following points: 1) Gene therapy
is a powerful new technology that will require several years
before it will make a noticeable impact on the treatment of
disease. 2) Several major problems still exist, including poor
delivery systems, both viral and non-viral, and poor gene
expression after genes are delivered. 3) The reason for the low
efficiency of gene transfer and expression in human patients is
that we still lack a basic understanding of how vectors should be
constructed, what regulatory sequences are appropriate for which
cell types, how in vivo immune defenses can be overcome, and how
to manufacture efficiently the vectors that we do make. 4)
Although it not surprising that we have not yet had notable
clinical successes, the lessons we are learning in the clinic are
invaluable in illuminating the problems that future research must
solve. 5) Despite our present lack of knowledge, gene therapy
will almost certainly revolutionize the practice of medicine over
the next 25 years. In every field of medicine, the ability to
give the patient therapeutic genes offers extraordinary
opportunities to treat, cure, and ultimately prevent a vast range
of diseases that now plague mankind.
QY: W. French Anderson, Univ. of Southern California 213-740-2311
(Nature 30 Apr 98 392/supp:25) (Science-Week 29 May 98)
-------------------
Related Background:
THE PROSPECTS FOR GENE THERAPY
... This has not been a good year for the gene therapy community,
considering the publicized lack of clinical success, and
considering that in Germany one of the foremost gene therapy
researchers has been accused of long-term fraud and suspended
from his professorship. But there are still optimists, and this
is still a field of vital importance to medicine. In a recent
review, Inder M. Verma and Nikunj Somia propose that "in the not
too distant future, gene therapy will become as routine a
practice as heart transplants are today."
QY: I. M. Verma, Laboratory of Genetics, The Salk Institute, La
Jolla CA 92037 US
(Nature 18 Sep 97)
-------------------
Related Background:
A RECOMBINANT GENE THERAPY FOR HUMAN RHEUMATOID ARTHRITIS
A cytokine is any substance that promotes cell growth and cell
division. Certain cytokines are endogenous, and need to be
controlled by cell regulatory mechanisms. When these mechanisms
fail, endogenous cytokines may be implicated in serious human
diseases such as rheumatoid arthritis, where apparently
deregulated cytokines cause the inflammatory response that
produces the symptoms. As a promoter of cell growth and division,
a cytokine acts as a messenger to cells, and the transmission of
the message requires a binding of the cytokine molecule to a
cytokine-specific receptor on the cell surface. This receptor is
either a protein or a protein complex or a part of a protein, and
one would expect that if we could synthesize the receptor and
introduce the synthesized product into the extracellular fluid,
the cytokine for which this receptor is specific would bind to
the receptor and be prevented from delivering its chemical signal
to the cells. Test-tube synthesis of most complex proteins
produced by biological cells is not yet possible, but what one
can do, after calculating the DNA code for the active part of the
receptor protein, is incorporate the necessary DNA sequence into
the genome of some mammalian cell line, and have these cells act
as chemical factories to produce the cytokine receptor that we
are unable to synthesize otherwise. We then gather the factory
product, administer it to the patient, and expect the cytokine
receptor to bind its specific cytokine in extracellular fluid and
thus reverse the course of the disease. This is essentially what
"recombinant gene therapy" is all about. It is a field less than
a decade old, and like all fields involving clinical medicine, it
moves slowly because procedures that involve human patients must
be carefully developed. This week, Larry W. Moreland et al (12
authors at various installations, US) report the successful
treatment of rheumatoid arthritis with a recombinant human
cytokine receptor complex produced by the method outlined above.
It is a beginning. Like all treatments involving recombinant gene
therapy, much work needs to be done. But the path ahead is clear,
and there is an expectation of important results from this area
of clinical medicine.
(New England Journal of Medicine 17 Jul 97)
-------------------
Related Background:
GENE-BASED IMMUNOTHERAPY FOR CERTAIN CANCERS EXPECTED SOON
Theodore Friedmann, director of the gene therapy program at the
University of California San Diego (US), points out that at
present no gene therapy approach has definitely improved the
health of a single one of the more than 2,000 patients who have
enrolled in gene therapy trials worldwide. Nevertheless,
Friedmann predicts that in the future gene therapy will be a
standard form of treatment for many diseases. In particular, he
says it seems likely that gene-base immunotherapies will succeed
with some malignancies such as neuroblastoma and melanoma in the
next few years, and will become helpful additions to existing
therapies for these diseases.
(Scientific American June 1997)

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

IN FOCUS: ON INVERTEBRATE PALEONTOLOGY
"Little work of importance was done in paleontology until the
1700's, at which time both vertebrate and invertebrate fields
began to assume importance. Intensive work in the invertebrate
area arose from recognition of the fact, first clearly seen by
William Smith, an English civil engineer and amateur geologist of
the period, that a given set of beds tended to contain the same
species of shells over vast and widely separated areas. Accurate
determination of fossils could thus be of great practical use to
the stratigrapher; as a result, invertebrate paleontology tended
to develop not as an independent science, but as a handmaiden to
the geologist -- a working tool for the stratigrapher looking for
oil or ores or coal. The fossil shells were rarely thought of as
the remains of once-living organisms, but merely as convenient
markers for the identification of successive formations, and
would have been as useful had they been identifiable mineral
inclusions or distinctive assortments of nuts and bolts... With
this background, the invertebrate workers of Darwin's day not
merely lacked interest in evolutionary ideas, but were inclined
to view them with suspicion as detrimental to their work. For
clear-cut stratigraphic work, the species in a given formation
should be stable entities, clearly distinguishable from those in
the strata above and below. The idea of gradual change and of
transitional forms was abhorrent... With this to contend with, it
is apparent why Darwin was thrown on the defensive in his
treatment of the fossil record. He could not call on the
paleontologists for support; the most he could do was to attempt
appeasement, to show that it was at least possible to interpret
the geological story in evolutionary terms, and that there was no
insuperable objection."

-- A.S. Romer: "Darwin and the Fossil Record"
   (in S.A. Barnett [ed.]: _A Century of Darwin_, 1958, Chap. 6)


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