ScienceWeek

SCIENCE-WEEK - Part 1/3

A Free Weekly Digest of the News of Science

February 27, 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:

Part 1:
1. On Confronting Creationist Fallacies
2. On Beauty and Truth in Scientific Theories
3. Questions Concerning Open Access to Crystallographic Data
4. Gamma Ray Burst Fireball Model May Need Revision
5. Lower Lithosphere Flow and Continental Strike-Slip Faults
6. Mountain Waves and Increased Stratospheric Ozone Depletion

Part 2:
7. Prediction of Small Protein Conformations
8. On the Transport of Water in Plants
9. An Estrogen Metabolite that Forms a DNA Adduct
10. Antigen-Specific T-Cell Anergy and Tumor Progression
11. Animal Intestinal Symbiont Stage of a Common Soil Bacterium
12. Cell-Cycle Kinetics During Development of Primate Cortex
13. Amyloid Secretion and Apoptosis in Cerebellum Cells
14. Anomalous Calcium Ion Flux Through Cardiac Sodium Channels

Part 3:
15. Variations in Neuron Number and Vocal Imitation in Birds
16. Prevention of Age-Related Vascular Changes by Aminoguanidine
17. On the Metastasis of Cancer Cells
18. Cellular Interactions of Ebola Virus Glycoproteins
19. Acorns, Gypsy Moth Outbreaks, and Lyme Disease Risk
20. Health Insurance and the Access of Children to Primary Care

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1. ON CONFRONTING CREATIONIST FALLACIES
If there is any arena in which the interface between the
scientific community and society at large is of importance it is
the education of the public, and especially the education of the
young public. And perhaps no part of that arena in the US is of
more consequence to many citizens than the attempt by certain
groups to fashion the teaching of science according to
preconceived religious views. ... ... D. Wise (Franklin and
Marshall College, US) reviews the current controversy between the
scientific community and creationists and discusses a strategy of
intellectual confrontation. Among other things, Wise enumerates
the following creationist ideas from the Bible that are totally
irreconcilable with extant scientific data: 1) the Earth came
into existence before the sun and stars; 2) the land plants came
into existence before the Sun; 3) the first life forms were
plants; 4) fruit trees appeared before fish; 5) fish appeared
before insects; 6) birds appeared before land reptiles. Indeed,
the acceptance of any of these ideas with a restraint of
consistency results in the tearing down of the entire fabric of
modern science (and the tearing down  of all its applications,
including modern medicine). Wise concludes, "As scientists, we
must emphasize repeatedly that the argument against creationism
is not against religion as such but rather against a fringe
group's attempt to force the Bible into the public schools in the
guise of a science textbook... The time has come to stop fighting
defensive skirmishes and start challenging creationists to defend
in toto what they call science -- humorous absurdities and all."
QY: Donald U. Wise  (American Scientist
Mar/Apr 1998)


2. ON BEAUTY AND TRUTH IN SCIENTIFIC THEORIES
There is an old adage, particularly in the physical sciences,
that of two theories arising from the same set of facts, one
theory beautiful and the other theory ugly, the beautiful theory
is more likely to be correct. There are indeed theories that are
difficult or impossible to test that have extensive and expansive
lives because of their aesthetic appeal, and that are discarded
with great reluctance when testing of the theory does eventually
become possible. ... ... J. McAllister (University of Leiden,
NL), in a review of the relation between the aesthetic properties
of scientific theories and their acceptance by the scientific
community, notes that many scientists claim to be able to tell by
means of aesthetic judgment how close a theory is to the truth,
but that in fact it often happens that a theory that is aesthet-
ically innovative strikes most scientists as ugly when it is
first put forward. For example, Kepler's theory of planetary
motions was initially considered ugly because it involved
ellipses rather than circles; Newton's theory of gravitation was
considered ugly because it postulated action at a distance;
quantum electrodynamics was first considered ugly for relying on
nonstandard mathematical operations for renormalization; and,
indeed, there is the famous rejection of quantum theory by
Einstein because he felt it lacked aesthetic appeal. Noting that
what is called beautiful changes as society and science change,
McAllister concludes the evidence that any aesthetic property of
theories is a sign of truth is at present scarce.
QY: James W. McAllister 
(American Scientist Mar/Apr 1998)


3. QUESTIONS CONCERNING OPEN ACCESS TO CRYSTALLOGRAPHIC DATA
In structural biology, among x-ray crystallographers, it is a
common practice on publication of results to enter crystallo-
graphic atomic coordinates in a repository but keep the data
inaccessible for a year. All sorts of reasons are put up for
this, but when the stew of reasons is boiled down the essence of
the matter is that the x-ray crystallographers (particularly
those at industrial installations) want a head-start on any
applications of their research, since crystallographic data
usually cannot be protected by patents. This is of course
antithetical to science and obnoxious to many scientists, since
most scientists expect and depend upon ready access to the
experimental results of other scientists and have no
"repositories" designed to make possible publication without
dissemination of research results. There is now an apparent
movement underway to end this quasi-publication custom in x-ray
crystallography, and of note is the announcement last week of a
collaboration by the competing journals Nature and Science to
determine the views of the scientific community at large about
the practice, and then reach a decision concerning what to do
about it -- if anything is to be done at all. Opinions on the
matter can be expressed to the editors of Nature at
, and to the editors of Science at
.
QY: Philip Campbell  (Nature 12 Feb 98)


4. GAMMA RAY BURST FIREBALL MODEL MAY NEED REVISION
Gamma rays are radiation of high energy, from about 10^(5)
electronvolts to more than 10^(14) electronvolts -- radiation
with the shortest wavelengths and highest frequencies, the gamma
ray region of the electromagnetic spectrum merging into the
adjacent lower energy x-ray region. Gamma ray bursts are intense
flashes of gamma rays detected at energies up to 10^(6) electron
volts. Neutron stars are one of the possible end-products of
stellar evolution. 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 current consensus is
that gamma ray bursts are produced by the merger of two neutron
stars, and up to this point, the bursts that have been noted
apparently originate outside our own galaxy. ... ... Castro-
Tirado et al (27 authors at 15 installations, ES DE SE DK IT UK
US) report an optical transient from a gamma ray burst (GRB
970508) imaged 4 hours after the event, displaying a strong
ultraviolet excess and reaching maximum brightness 2 days later.
The optical spectra did not show any emission lines, and no
variations on time scales of minutes were observed for 1 hour
during the decline phase. The authors suggest the observations
are incompatible with the fireball and afterglow models of gamma
ray bursts, and that another physical mechanism may be respons-
ible for the constant phase seen the first few hours after the
burst occurs. QY: T. Broadhurst, Univ. of Calif. Berkeley, Dept.
Astronomy 510-643-8520 (Science 13 Feb 98)

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Related Background:

OPTICAL STUDIES OF A GAMMA-RAY BURST SUGGEST FIREBALL MODEL
Studies of the mysterious gamma-ray bursts seen in every part of
the sky daily continue to be reported. This week we have the
results of observations of gamma ray burst (GRB) GRB970508, which
occurred on May 8, 1997 (hence the name). Optical studies of the
source of the burst by M. R. Metzger et al (California Institute
of Technology, US; National Radio Astronomy Observatory, US;
Institute of Space Astrophysics, Frascati IT; University of
Ferrara, IT) using data from the recently orbited Italian-Dutch
satellite BeppoSAX indicate the source of the GRB is extra-
galactic at a distance of 5 billion parsecs (1 parsec = about 20
trillion miles). Taking into account the recorded energy and its
loss by intervening absorption across that distance, we are
considering an initial energy burst with a magnitude equal to
the total radiation from our Sun during the entire age of the
universe. The computed energy figure is 10^(51) ergs of
gamma-rays. A consensus among astrophysicists is forming that
these GRBs involve "relativistic fireballs" produced by
colliding neutron stars, either two neutron stars colliding with
each other, or single neutron stars colliding with black holes.
The various radiant energy data are coming in so rapidly now,
there is a feeling the physical nature of GRBs will soon be
completely understood.
(Nature 26 Jun 97)

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AN HISTORIC MEETING DEVOTED TO GAMMA RAY BURSTS
Gamma ray bursts (GRBs) have been much in the news the past 10
months, principally because of correlative data from x-ray,
optical, and radio instruments. Last month saw the Fourth
Huntsville Symposium on Gamma Ray Bursts (15-20 Sep 1997,
Huntsville AL US), and the meeting is being called "historic".
There is apparently now a consensus that GRBs are cosmological
rather than galactic in origin, in other words from outside our
Milky Way galaxy. So that part of the 30-year puzzle concerning
GRBs is evidently solved. The other part of the puzzle concerns
the physical events producing the bursts, and for that part of
the puzzle there is apparently no consensus yet. It has recently
been proposed that GRBs are associated with the cataclysmic end
of massive stars, and if this is true, it is believed the
appearance of GRBs should provide data concerning the rate of
formation of such stars, a critical parameter that has evidently
been established by observation. In any case, the gamma ray burst
field has apparently now shifted to data analysis at new
wavelengths of the electromagnetic spectrum, with the emphasis
now on x-ray, optical, and radio observations from several
instrument sources, including the valuable BeppoSAX satellite,
the Hubble Space Telescope, and the Burst and Transient Source
Experiment (BATSE) aboard the Compton Gamma Ray Observatory.
QY: Bohdan Paczynski  (Nature 9 Oct 1997)


5. LOWER LITHOSPHERE FLOW AND CONTINENTAL STRIKE-SLIP FAULTS
A geophysical fault is a break in rock structure that occurs when
pressures in the Earth's crust are strong enough to cause
fracture and displacement, and earthquakes are common at such
break points. A strike-slip fault is a movement parallel to the
fault plane, and the San Andreas fault of California is of this
type. The term "lithosphere" refers to the outer layer of the
Earth, comprising the crust and upper mantle, and extending to a
depth of 50 to 70 kilometers. The traditional view of tectonics
(changes in the structure of the Earth's crust) is that the
lithosphere consists of a strong brittle layer overlying a weak
ductile layer, the system producing two forms of deformation,
namely, brittle fracture in the upper layer (accompanied by
earthquakes), and aseismic (without earthquakes) ductile flow in
the lower layer. The current consensus is that this view is
generally correct but imprecise, since the accumulated evidence
is now interpreted to indicate that frictional events along fault
lines, rather than new fractures, are the causes of earthquakes.
The essential idea is that fault lines, which are the interfaces
between the crustal plates, build up stresses resulting from the
movements of the plates, and at intervals these stresses are
suddenly relieved by interface slippages the surface manifest-
ations of which are earthquakes. One important question is how
movements of the lithosphere relate to the faults and to earth-
quakes, with one view holding that lithosphere deformations are
secondary, and the other view holding that lithosphere deform-
ations are of great significance for fault behavior. The Marl-
borough fault zone is found in the South Island of New Zealand.
Geodetic measurements, in this context, are measurements of
contemporary terrestrial structure, as opposed to determinations
based on geological (historical) analysis. ... ... Bourne et al
(University of Oxford, UK) report an investigation of the
consequences of the lithosphere deformation model. They tested
predictions of the model in two plate boundary regions, the
Marlborough fault zone and the Southern California fault zone,
and they found that slip rates on the faults predicted from
geodetic measurements are in good agreement with geologically
determined slip rates. The authors suggest their results support
the view that flow in the ductile portion of the lithosphere
drives the accumulation of strain in the brittle upper layer
where faulting occurs, and must play a role in the post-seismic
relaxation of strain resulting from slip during earthquakes, and
that the upper-crustal blocks must follow the flow of the lower
layer. QY: S.J. Bourne 
(Nature 12 Feb 98)


6. MOUNTAIN WAVES AND INCREASED STRATOSPHERIC OZONE DEPLETION
The term "mountain wave" refers to an undulating flow of wind on
the downwind side of a mountain ridge caused by wind blowing
strongly over the ridge. In meteorology, the term "synoptic"
refers to the use of meteorological data obtained simultaneously
over a wide area to present a comprehensive picture of the state
of the atmosphere. ... ... Carslaw et al (11 authors at 4
installations, DE US) report aircraft observations of mountain-
wave-induced polar stratospheric clouds in which temperatures
were 12 degrees kelvin lower than expected synoptically.
Theoretical calculations indicate that despite their localized
nature, these polar stratospheric clouds can cause almost
complete conversion of inactive chlorine species to ozone-
destroying forms in air flowing through the clouds, and using a
global mountain-wave model, the authors identify regions where
mountain waves can develop, and show they can cause frequent
chlorine activation of air in the Arctic stratosphere. The
authors suggest such processes are a possible explanation for the
underprediction of reactive chlorine concentrations and ozone
depletion rates calculated by 3-dimensional models of the Arctic
stratosphere. QY: K.S. Carslaw 
(Nature 12 Feb 98)

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

Related Background:

A FOOTNOTE TO THE HISTORY OF CHLOROFLUOROCARBONS
In chemistry, chlorofluorocarbons (CFCs) are any of a variety of
gaseous compounds that are derivatives of methane or ethane with
hydrogen atoms replaced by fluorine and chlorine. They were first
introduced in the 1930s, and they have been especially useful as
refrigerants, aerosol propellants, and foaming agents for poly-
urethane products. In the early 1970s, a chemist named F. Sher-
wood Rowland stepped down as Chairman of the Department of
Chemistry at the University of California Irvine (US), and looked
around for a new project. He was an established chemist with over
170 publications under his name. He happened to hear a lecture on
the biosphere and heard news that a sensitive instrument to
measure trace organic compounds in the atmosphere had detected
CFCs throughout the troposphere, which is the atmosphere layer
between ground and the stratosphere. The atmosphere scientists
were excited by the possibility of using CFCs to measure air-mass
movements, since the CFCs were thought to be chemically stable
and thus remain in the atmosphere indefinitely. Rowland, however,
decided that if the CFCs would drift upward to the stratosphere
and be subjected to ultraviolet light, they would release
chlorine, which in turn would immediately react with ozone,
initiating a long and complex chain reaction that would quickly
destroy thousands of ozone molecules for every molecule of
chlorine. The presence of the oxygen molecule ozone in Earth's
atmosphere shields the surface from ultraviolet radiation, which
in turn can cause cancer, crop failure, and general disruption of
the food chain. Rowland and a photochemist named Mario Molina
started working on the problem of determining the eventual fate
of CFCs in the atmosphere. The measurements suggested there was
no chance the CFCs would be rinsed out of the atmosphere by rain,
and indicated the amount of CFCs already in the atmosphere was
equal to the total amount ever manufactured, or several million
tons. In 1973, they calculated the eventual loss of approximately
20 to 40 per cent of the ozone layer. In 1974, they published a
paper in Nature, and presented their findings at a meeting of the
American Chemical Society, but hardly anyone paid any attention.
But a few people did pay attention, including a U.S government
atmosphere scientist named Paul Crutzen, and the Rowland and
Molina calculations were confirmed. The press then got hold of
the story, and national and international efforts soon resulted
in the banning of CFCs. In 1984, the Antarctic ozone hole was
discovered, with 40% ozone depletion and a 10% increase in
ultraviolet penetration. In 1995, Rowland, Molina, and Crutzen
shared the Nobel Prize in Chemistry for their work with CFCs.
This week, in a published interview, Rowland reveals that between
1974 and 1988, when DuPont agreed to halt production of CFCs, he
was ostracized by the chemical industry, called an agent of the
KGB, and shunned by academic colleagues in chemistry everywhere.
During those years he did not receive any applications from
graduate students or postdocs from outside the California
university system -- he was effectively banned by the chemical
community for 14 years. (Univ. of Chicago Magazine August 1997)


(continued in Part 2)

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SCIENCE-WEEK - Part 2/3

A Free Weekly Digest of the News of Science

February 27, 1998

Contents of Part 2:

7. Prediction of Small Protein Conformations
8. On the Transport of Water in Plants
9. An Estrogen Metabolite that Forms a DNA Adduct
10. Antigen-Specific T-Cell Anergy and Tumor Progression
11. Animal Intestinal Symbiont Stage of a Common Soil Bacterium
12. Cell-Cycle Kinetics During Development of Primate Cortex
13. Amyloid Secretion and Apoptosis in Cerebellum Cells
14. Anomalous Calcium Ion Flux Through Cardiac Sodium Channels

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7. PREDICTION OF SMALL PROTEIN CONFORMATIONS
As long chain polymers with a variety of subunit (residue)
sequences, proteins assume complicated configurations that depend
on their chemical constitutions and ambient conditions. The
"primary" structure of a protein refers to the sequence of amino
acid subunits that constitute the chain of the polymer; the
"secondary" structure refers to a chain configuration (for
example, alpha-helix or beta-pleated-sheet) caused by amino acid
interactions (e.g., via hydrogen bonds); the "tertiary" structure
refers to a higher order folding of the configured chain
(stabilized, for example, by disulfide bonds); the term
"quaternary" structure refers to a still higher order assembly
involving multiple polypeptide folded chains interacting to form
a large and complex protein entity. In the context of this
report, the term "nonhomologous proteins" refers to a group of
proteins whose differences in basic constitution are other than
merely additive; the term "native" refers to structures found in
living systems; the term "sequence alignment" refers to close
(proximal) higher order structure alignments of particular amino
acid sequences actually in different parts of the chain as
expected from related empirical observations or fundamental
chemical considerations. In general, the idea here is essentially
to constrain simulations into tractable forms that still yield
useful results. ... ... Ortiz et al (3 authors at Scripps
Research Institute, US) report that by incorporating secondary
and tertiary structure restraints derived from multiple sequence
alignments into folding simulations, it has been possible to
assemble native-like tertiary structures of 19 nonhomologous
proteins ranging from 29 to 100 residues in length and
representing all secondary structural classes. The authors
suggest this study indicates the use of restraints derived from
multiple sequence alignments combined with a fold assembly
algorithm is a promising approach to the prediction of the global
topology of small proteins.
QY: Jeffrey Skolnick 
(Proc. Natl. Acad. Sci. US 3 Feb 98)


8. ON THE TRANSPORT OF WATER IN PLANTS
In the context of this report, the term "stretched water" refers
to bulk water stretched under tension, and the term "embolism"
refers to any air hiatus in a water column. Osmosis is the
movement of water through a barrier permeable only to water from
a region of high water concentration to a region of low water
concentration (e.g., from a dilute salt solution [high water
concentration] to a concentrated salt solution [low water
concentration]), and "reverse osmosis" refers to the reverse
movement of water through such a membrane (from low to high water
concentration) forced by pressure change (or change in some other
thermodynamic state variable) in the low water concentration
phase. The essential idea is that when water is the solvent in
phases separated by a barrier permeable only to water, the
molecules of water will partition across the barrier in accord-
ance with the thermodynamics of the two-phase system.
... ... M. Canny (Carleton University, CA) reviews the mechanisms
of water transport in plants, the history of research in this
field, and current controversies. The author suggests that in
general evaporation from the leaves of a tree pulls water to the
top of the tree through small-dimension dead cellulose pipes (the
classical concept), but living cells make that possible by
protecting the stretched water and repairing it when it breaks.
He introduces a compensating pressure theory, in which the water
in plants is weak under tension, breaking frequently at modest
operating pressures to form embolisms, but tissue pressure
refills the embolisms by squeezing water out of cells and into
the pipes by reverse osmosis.
QY: M.J. Canny 
(American Scientist Mar/Apr 1998)


9. AN ESTROGEN METABOLITE THAT FORMS A DNA ADDUCT
In chemistry, an "adduct" is a compound composed of the simple
addition of two other compounds, and a "metabolite" is a compound
produced by the metabolic breakdown or other metabolic
transformation of a parent compound. Quinones are conjugated
cyclic diketones, and a semiquinone is the result of a single-
electron transfer involving a quinone that produces a form (a
semiquinone radical) with both a negative charge and an odd
electron. Estrogen is a collective term for the female hormones,
the most powerful of which is estradiol; the estrogens control
female secondary sexual characteristics, and prepare and maintain
the uterine lining. Equilenin is an estrogen that comprises
approx-imately 6% of the mixture of estrogens in the drug
Premarin, which is used by about 10 million women in the US in
estrogen replacement therapy. Catechol is 1,2-dihydroxybenzene.
... ... Bolton et al (University of Illinois Chicago, US) report
novel adducts between a predicted metabolite (the catechol
4-hydroxyequilenin) of the estrogen equilenin and DNA, and
nuclear magnetic resonance experiments to determine the structure
of these adducts. The authors suggest the mechanism of adduct
formation involves a one-electron oxidation of the catechol to a
semiquinone radical, which then interacts with DNA bases, and
that estrogen and estrogen-like compounds may produce stable and
potentially damaging adducts with DNA. The idea that semiquinone
radical intermediates bind to DNA is apparently unique.
QY: Judy L. Bolton, Univ. of Illinois Chicago 312-996-4350
(Chem. & Eng. News 16 Feb 98)


10. ANTIGEN-SPECIFIC T-CELL ANERGY AND TUMOR PROGRESSION
T-cells are a class of cells of the vertebrate immune system, CD4
T-cells are T-cells expressing the surface receptor marker
protein CD4, and CD4(sup+) T-cells are a subtype of such cells
that ordinarily respond to and provoke the killing of cancer
cells. An antigen is any substance that reacts with immune system
cells to induce a form of immune response, and cancer cells are
known to produce certain antigens that provoke the immune
response. The term "clonal proliferation" refers to the
proliferation of a line of cells from a single progenitor or a
small number of progenitors. In immunology, the term "anergy"
refers to the absence of the ability to generate a sensitivity
reaction to an antigen. ... ... Stavely-O'Carroll et al (8
authors at Johns Hopkins University, US) report a study involving
the transfer of CD4(sup+) T-cells specific for an antigen
expressed by tumor cells into tumor-bearing mice. Transient
clonal proliferation of the T-cells occurred early after
transfer, accompanied by changes associated with antigen
recognition, but the cells had a diminished response to the
peptide antigen in vitro and were unable to be activated in vivo.
The authors suggest the development of antigen specific T-cell
anergy occurs early in the tumor-bearing host, that tolerance to
tumor antigens may be a significant barrier to therapeutic
vaccination, and that identification of the molecular basis for
tumor-induced T-cell anergy, and of strategies to restore T-cell
responsiveness, will be critical to the ultimate success of
active anti-tumor immunotherapy.
QY: Hyam Levitsky 
(Proc. Natl. Acad. Sci. US 3 Feb 98)


11. ANIMAL INTESTINAL SYMBIONT STAGE OF A COMMON SOIL BACTERIUM
The term "arthromitus inclusions" refers to apparent microbial
entities first identified and named by Joseph Leidy in 1849.
Eubacteria are a prokaryote (lacking a nucleus and other
organelles) subkingdom of bacteria, and bacilli are a genus of
rod-shaped bacteria, some of which show filamentous proliferation
(i.e., continued divisions produce a chain of attached progeny).
Agar, a crude extract from red algae that forms a gel, is used as
a solid culture medium in microbiology, with various nutrient
components added to it in solution before gelation occurs.
... ... Margulis et al (6 authors at 3 installations, US DE)
report the identification of Arthromitus inclusions in the guts
of more than 25 species of arthropods, that cultivation of these
entities from 10 different species of soil insects indicates
Arthromitus are spore-forming bacilli, and that gene sequencing
studies of 4 isolates confirm the entities as the eubacterium
Bacillus cereus. The authors suggest that B. cereus and its close
relatives, easily isolated from soil and grown on nutrient agar,
have an Arthromitus normal intestinal stage, showing filamentous
growth in the moist nutrient-rich intestines of healthy arthro-
pods and similar habitats. QY: Lynn Margulis, Univ. of Massachu-
setts, Dept. of Geosciences 413-545-2545
(Proc. Natl. Acad. Sci. US 3 Feb 98)


12. CELL-CYCLE KINETICS DURING DEVELOPMENT OF PRIMATE CORTEX
In this report, the term "cortical expansion" refers to the
observation that the volume (and number of constituent neurons)
of the cerebral cortex relative to the rest of the brain
increases from lower mammals to higher mammals, reaching its
greatest expansion in the primates (including humans). Since the
cerebral cortex is the region of the central nervous system most
intimately involved with the so-called "higher faculties", an
understanding of its evolution is of great interest. The term
"cell cycle" refers to the ordered sequence of phases through
which a cell passes from one mitotic cell division to the next,
and cell-cycle kinetics refers to the time parameters of the
cell-cycle. The term "neurogenesis" refers to the production of
nerve cells during embryological development. Extracellular
signaling molecules are molecules external to cells that interact
with specific receptors on the surfaces of cells, the interaction
then provoking a cascade of signal events that ultimately reach
important biochemical and genetic control centers in the
cytoplasm and nucleus. ... ... Kornack and Rakic (Yale Univers-
ity, US), in order to investigate whether cortical expansion in
primates reflects modification of cell-cycle kinetics, determined
cell-cycle length during neurogenesis in a proliferating cerebral
zone in fetal rhesus monkeys. They found that cell-cycle
durations in monkeys were as much as 5 times longer than those
reported in rodents, but that substantially more total rounds of
cell division elapsed during the prolonged neurogenetic period of
the monkey cortex, and that in contrast to the slowing of
cortical development that occurs in rodents, cell division
accelerated during neurogenesis of the enlarged cortical layers
in monkeys. The authors suggest that evolutionary modification of
the duration and number of progenitor cell divisions contribute
to both the expansion and laminar elaboration of the primate
neocortex, with species-specific regulation provided by specific
extracellular signaling molecules.
QY: David R. Kornack 
(Proc. Natl. Acad. Sci. US 3 Feb 98)


13. AMYLOID SECRETION AND APOPTOSIS IN CEREBELLUM CELLS
The term "amyloid" refers to a class of polypeptides showing
macroscopic fibrillar formations and found in extracellular
spaces in the brains of patients with Alzheimer's disease, Down
syndrome, and to a much lesser degree in association with normal
aging. A primary type of disease-associated amyloid is "amyloid
beta-protein", which is apparently produced by an enzyme that
cleaves a precursor protein into fragments, and there has been
much research on both this precursor protein and its cleavage
products. In general, the term "apoptosis" refers to any form of
programmed cell death, i.e., cell death involving a sequence of
triggered self-destruct mechanisms in the cell. In this report,
apoptosis was induced in cultured neurons by reducing external
potassium concentration from 25 mM to 5 mM, and the apoptotic
cells then subjected to "depolarization stimulation". The
technique of depolarization stimulation essentially involves the
exposure of neurons to high external concentrations (56 mM) of
potassium ions, the exposure producing severe membrane electrical
depolarization and release from secretory vesicles of
neurotransmitters, neuropeptides, and other entities. ... ...
Galli et al (7 authors at 3 installations, IT) investigated the
secretion of amyloid beta-protein in an in vitro model  (cultures
of rat cerebellar neurons) of neuronal apoptosis, report a 3-fold
increase in amyloid beta-protein secretion provoked by the
technique of depolarization stimulation of apoptosis. The authors
suggest that an overproduction of amyloid beta-protein may be the
consequence of neuronal damage from various causes, in addition
to any involvement as a provocation of neuronal damage.
QY: Cinzia Galli 
(Proc. Natl. Acad. Sci. US 3 Feb 98)


14. ANOMALOUS CALCIUM ION FLUX THROUGH CARDIAC SODIUM CHANNELS
Beta-adrenergic receptors are characterized according to their
interactions with certain pharmacological agents, but in general
they are molecular receptors whose activation results in
physiological responses such as increases in cardiac rate and
force of contraction (beta-1 receptors), and relaxation of
bronchial and vascular smooth muscle (beta-2 receptors). Protein
kinases are a class of enzymes that phosphorylize other proteins,
with many kinases responding to important signaling molecules.
Tetrodotoxin (molecular wt. 319) is a potent neurotoxin produced
by the ovaries and livers of many species of fish (e.g., Japanese
blowfish), the toxin apparently binding specifically to a certain
type of sodium ion channel with a resultant blockade of sodium
current and prevention of the action potential response of the
nerve cell membrane. The steroids are a large class of chemical
substances comprising many hormones, body constituents, and
drugs, all containing the tetracyclic cyclopenta[alpha]phenan-
threne skeleton. The term "cardiotonic" refers to any effect that
involves a favorable action on the heart, e.g., an increase in
contraction force, and cardiotonic steroids are steroids with
such cardiac effects. Ouabain (G-strophanthin), a steroid
glycoside, is the chemical agent in an African arrow poison
obtained from the plant (tree) extract ouabaio, and digoxin is a
steroid glycoside obtained from the plant Digitalis lanata.
... ... Santana et al (University of Maryland, US) report that
activation of the beta-adrenergic receptor or protein kinase A in
rat heart cells transformed the tetrodotoxin-sensitive sodium ion
channel into a channel that permits calcium ions to permeate as
readily as sodium ions. Nanomolar concentrations of cardiotonic
steroids such as ouabain and digoxin produced the same effect,
called "slip-mode conductance". The authors suggest that slip-
mode conductance of the sodium channel can contribute signific-
antly to local and global cardiac calcium ion signaling and may
be a general signaling mechanism in excitable cells.
QY: W.J. Lederer  (Science 13 Feb 98)

(continued in Part 3)

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

SCIENCE-WEEK - Part 3/3

A Free Weekly Digest of the News of Science

February 27, 1998

Contents of Part 3:

15. Variations in Neuron Number and Vocal Imitation in Birds
16. Prevention of Age-Related Vascular Changes by Aminoguanidine
17. On the Metastasis of Cancer Cells
18. Cellular Interactions of Ebola Virus Glycoproteins
19. Acorns, Gypsy Moth Outbreaks, and Lyme Disease Risk
20. Health Insurance and the Access of Children to Primary Care

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15. VARIATIONS IN NEURON NUMBER AND VOCAL IMITATION IN BIRDS
In songbirds, a network of brain regions are apparently dedicated
to the learning, production, and perception of song, and there
are indications that the sizes of these regions correlate with
the capacity for song learning and production. The Australian
zebra finch memorizes song material from kindred birds ("social
tutors") during the period 20 to 60 days after hatching, begins
song-like vocalization at 30 to 45 days of age, and by 90 days of
age, the song pattern is stereotyped. ... ... Ward et al (3
authors at University of Rochester, US) report that in male zebra
finches individual differences in region volume and neuron number
in two song-related brain regions showed positive correlations
with differences in the number of song-syllables accurately
copied. Since previous work has shown that volume and neuron
number of these regions are not regulated by song learning, the
authors suggest the correlations indicate that naturally occur-
ring variations in neuron number constrain how much song material
can be copied or reproduced, with variation in the number of
song-related neurons possibly reflecting differences in cell
production, cell specification, or cell survival.
QY: K.W. Nordeen 
(Proc. Natl. Acad. Sci. US 3 Feb 98)


16. PREVENTION OF AGE-RELATED VASCULAR CHANGES BY AMINOGUANIDINE
A glycate is the product of a nonenzymatic reaction between a
sugar and free amino acid groups of a protein, and glycation is a
nonenzymatic reaction that forms a glycate. The term "cardiac
hypertrophy" refers to enlargement of the heart; collagen is the
major protein of the white fibers of connective tissue, cartil-
age, and bone; elastin is a fibrous mucoprotein and the major
protein of elastic tissues such as tendons; the term "extra-
cellular matrix" refers to the matrix of polymer substances
occupying the spaces between cells in a tissue.
... ... Corman et al (7 authors at 2 installations, FR) report
that aminoguanidine, an known inhibitor of the production of
advanced glycation end products, when administered in drinking
water to aging rats, did not modify body weight and kidney weight
of the rats, but prevented age-related cardiac hypertrophy and
arterial stiffening without any changes in collagen and elastin
content of the arterial wall. The authors suggest the prevention
of arterial stiffening and cardiac hypertrophy by aminoguanidine
is related to a decrease in cross-linking of the extracellular
matrix induced by advanced glycation end products.
QY: Bernard I. Levy 
(Proc. Natl. Acad. Sci. US 3 Feb 98)


17. ON THE METASTASIS OF CANCER CELLS
In general, the term "metastasis" refers to the spread of any
disease from one part of the body to another, but in the context
of this report the term refers specifically to the spread of
cancer cells from a primary tumor to other parts of the body via
the lymphatic system or blood vessels or any of the fluid-filled
body spaces. The essential aspect of metastasis is the break-out
of cancer cells from the tissue or organ of origin and into
tissues that may be near or quite distant if the cancer cells are
carried by the blood, for example. Apart from any deleterious
complications caused by a tumor in place, the metastasis of tumor
cells to vital organs is the most dangerous aspect of the cancer
diseases. The proteases are a group of enzymes that catalyze the
irreversible breakdown of proteins, and the production of
proteases by metastatic cancer cells facilitates the passage of
these cells through various tissues. ... ... Van Noorden et al (3
authors at 3 installations, NL US CH), in a review of carcino-
genesis and the production of metastatic cancer cells, note that
new discoveries are being reported daily, that a comprehensive
picture of the genetic, biochemical, and cellular alterations
involved is rapidly emerging, and that each new piece of the
picture provides a possibility for therapeutic intervention that
may someday eliminate cancer entirely. Concerning metastasis, the
authors further suggest an important potential target for drug
intervention is the group of proteases that allow metastatic
cancer cells to exit their tissues of origin and enter new
tissues to form new tumors.
QY: Cornelis J.F. Van Noorden 
(American Scientist Mar/Apr 1998)


18. CELLULAR INTERACTIONS OF EBOLA VIRUS GLYCOPROTEINS
The hemorrhagic fevers, of which there are a number of types, are
marked by a cluster of severely debilitating symptoms, and
especially by capillary bleeding (hemorrhaging). Ebola virus,
classified as a filovirus, is the pathogen of a hemorrhagic fever
prevalent in Africa. A glycoprotein is one of a group of protein-
carbohydrate compounds (conjugated proteins). In general, the
term "neutrophil" refers to any cell or tissue with no special
affinity for acid or basic dyes, but in immunology the term
specifically refers to certain cells of the immune system, a
certain type of mature leukocyte (white blood cell) that normally
comprises about half of the leukocytes that circulate in the
system. Surface markers, of which there are many types, are
surface proteins, or glycoproteins, or groups of proteins that
distinguish a cell or subset of cells from other defined cells or
subsets of cells. Endothelial cells are a variety of cells that
form flat layers (endothelia) lining the heart and vessels such
as blood vessels and lymphatic vessels. ... ... Yang et al (7
authors at 3 installations, US) report that the secreted form of
the Ebola virus glycoprotein interacts with neutrophils via the
surface marker CD16b, but the transmembrane form of the
glycoprotein interacts with endothelial cells but not with
neutrophils. The authors suggest the secreted glycoprotein
inhibits early neutrophil activation, which likely affects the
host response to infection, whereas binding of the transmembrane
glycoprotein to endothelial cells may contribute to the
hemorrhagic symptoms of this disease, and that therapeutic
inhibition of binding of the two forms of glycoprotein is likely
to ameliorate the effects of acute Ebola virus infection. QY:
Gary J. Nabel, University of Michigan, Dept. of Internal Medicine
313-764-7433 (Science 13 Feb 98)


19. ACORNS, GYPSY MOTH OUTBREAKS, AND LYME DISEASE RISK
Lyme disease is caused by a spirochete bacterium, Borrelia
burgdorferi, a spirally coiled organism in which 2 to 100
flagella (contractile strands that are responsible for bacterial
motion) are wound beneath a flexible outer cell wall, enabling
the spirochete to move by rhythmic flexing that causes a cork-
screw motion through the surrounding medium. The pathogen that
causes syphilis is also a spirochete. In humans, Lyme disease is
contracted through the bite of small ticks such as the minute
tick Ixodes dammini. The disease was first recognized in 1975 as
a result of an unusual clustering of cases in the small community
of Lyme, Connecticut (US), and hence the name. It has since
appeared in more than half the states in the U.S., especially the
northeastern coast, and in California and Oregon, and it has also
appeared abroad. In the U.S., 18,461 cases of Lyme disease were
reported in 1996, a 41% increase over 1995. This disease is now
the most commonly reported tick-borne illness in the U.S., and it
is an insidious pathological entity that if not treated early may
lead to severe arthritis, various serious neurological complic-
ations when the organism invades the central nervous system, and
in some cases death. Gypsy moths are large insects accidentally
transported into New England from Europe in the late 19th
century. In a metamorphosing insect, the pupa is the quiescent
intermediate form between the larva and the adult.
... ... Jones et al (5 authors at 3 installations, US) report
that in eastern US oak forests, both defoliation by gypsy moths
and the risk of Lyme disease are determined by interactions among
acorns, white-footed mice, moths, deer, and the black-legged
ticks that carry the Lyme disease pathogen. Experimental removal
of mice, which eat moth pupae, indicates that moth outbreaks are
caused by reductions in mouse density that occur when there are
no acorns. Experimental acorn addition increased mouse density.
Acorn addition also increased the densities of black-legged
ticks, evidently by attracting deer, which are key tick hosts. It
is already known that mice are primarily responsible for
infecting ticks with the Lyme disease agent. The authors suggest
their results have important implications for predicting and
managing forest health and human health, and clearly demonstrate
that both gypsy moth dynamics and Lyme disease risk have
contingent outcomes arising from a complex chain of strong
pairwise interactions among taxonomically diverse species that
are all interconnected within an ecosystem.
QY: Clive G. Jones 
(Science 13 Feb 98)
-------------------
Related Background:
ORAL ANTIBIOTIC AN EFFECTIVE TREATMENT OF EARLY LYME DISEASE
... Antibiotics are the treatments of choice for Lyme disease,
particularly oral doxycycline and parenteral (non-oral)
ceftriaxone. For most clinical cases of Lyme disease, if the
patient is treated early enough, especially during the first
year, there is a high total cure rate (approximately 85%).
Treatment with the parenteral antibiotic is much more expensive
than treatment with the oral antibiotic (the estimate is approx-
imately $5,000 vs. $500), and for some time there has been a
public non-medical debate about health policy, with complaints
that more effective parenteral antibiotics for Lyme disease were
not being offered to enough patients. This week, Raymond J.
Dattwyler et al (12 authors at various installations, US) report
a carefully controlled study of 140 Lyme disease patients
indicates that early treatment of patients with acute dis-
seminated Lyme disease (in the absence of meningitis) with oral
antibiotic is just as effective as treatment with the more
expensive parenteral antibiotic. Whether these results will
reduce the decibels of the public health policy debate is
uncertain, but at least now there are some results that can be
used to make decisions. Contact: R. J. Dattwyler, Dept. of
Medicine, State Univ. New York Stony Brook (516) 632-6868
(New England J. Medicine 31 Jul 97)


20. HEALTH INSURANCE AND THE ACCESS OF CHILDREN TO PRIMARY CARE
The US National Health Interview Survey is a continuing household
survey of the non-institutionalized population of the US, cond-
ucted by trained personnel from the Bureau of the Census, and
sponsored by the National Center for Health Statistics. The sur-
vey instrument consists of a core questionnaire and supplemental
questionnaires on selected topics of interest to the public
health community. The Survey conducts field interviews in approx-
imately 50,000 US households annually. ... ... Newacheck et al (4
authors at University of California San Francisco, US) report an
analysis of data concerning 49,367 children under 18 years of age
from the 1993-1994 National Health Interview Survey indicates the
following: 1) An estimated 13% of US children did not have health
insurance in 1993-1994; 2) uninsured children were less likely
than insured children to have a usual source of health care (76%
vs. 96%); 3) among those with a usual source of health care,
uninsured children were more likely than insured children to have
no regular physician, to be without access to medical care after
normal business hours, and to have families that were dissatis-
fied with at least one aspect of their care; 4) uninsured
children were less likely to have had contact with a physician
during the previous year. The authors suggest that, among
children, having health insurance is strongly associated with
access to primary health care. QY: Paul W. Newacheck, Univ. of
Calif. San Francisco 415-476-4044 (New England J. Med. 19 Feb 98)

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BOOK NOTES:

R.J. Cone and P. Barnes-Svarney: HOW THE NEW TECHNOLOGY WORKS
A Guide to High-Tech Concepts
Oryx Press, 1998, 144p, US28.50
2nd Edition. Non-technical explanations of basic scientific
principles behind high-tech concepts. Biotechnology,
nanotechnology, planetary spacecraft, high definition television,
virtual reality, sheep cloning, computer chess, cryogenics, etc.
The authors are science journalists.

Ken Croswell: PLANET QUEST
The Epic Discovery of Alien Solar Systems
Oxford Univ., 1997, 324p, US25 UK18.99
A well-written journalistic account of astronomical research on
extrasolar planets, with extensive notes and a reference section.

Terrence W. Deacon: THE SYMBOLIC SPECIES
The Co-Evolution of Language and the Brain
W. W. Norton, 1997, 527p, US29.95
A wide-ranging monograph of interest to both general readers and
experts. Treats the evolution of the neurological basis of
language. A complete review of current data and concepts.

Michael T. Ghiselin: METAPHYSICS AND THE ORIGIN OF SPECIES
State Univ. of New York, 1997, 377p, US24.95 UK19.50
A monograph on the theoretical significance of species identities
by a noted theoretical biologist and philosopher of biology.

Martin Harwit: ASTROPHYSICAL CONCEPTS
3rd Edition
Springer, 1998, 696p, US69.95
An introductory text. The focus is a quantitative understanding
of the material. Cosmic events, astrophysical sketches,
astronomical calculations, recent developments. This edition
entails a thorough revision of the last edition.

C.J. Lumsden et al (eds.): PHYSICAL THEORY IN BIOLOGY
Foundations and Explorations
World Scientific, 1997, 486p, US85 UK59, paper US42 UK21
20 essays by specialists. Pattern formation, derivations of shape
and form, applications of statistical mechanics to membranes and
bilayers, biological evolution, the brain, statistics of DNA
sequences. The book may be of considerable use to physicists
seeking biological problems for research.

James B. Seaborn: UNDERSTANDING THE UNIVERSE
An Introduction to Physics and Astrophysics
Springer, 1998, 304p, US49.95
Teaches physics using astronomy and astrophysics. Newtonian
mechanics, electromagnetism, elementary quantum theory, the
structure of matter, the constitution of stars, kinetic theory,
nuclear physics, stellar structure and evolution, redshifts,
cosmology. The author is at the University of Richmond, US.

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