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ScienceWeek
SCIENCE-WEEK
SCIENCE-WEEK - Part 1/3
A Free Weekly Digest of the News of Science
May 8, 1998 - Issue #54
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It is odd, but on the infrequent occasions when I have been
called upon in a formal place to play the bongo drums, the
introducer never seems to find it necessary to mention that I
also do theoretical physics.
-- Richard Feynman
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Contents of This Issue:
Part 1:
1. On the Interdependence of Science and Law
2. A Science Faculty Racial Discrimination Claim in Canada
3. Science and History: The Lost Colony of Roanoke Island
4. On the Presumption of Purity in Mathematics
5. On Microquasars in Our Galaxy
6. Earth's Obliquity and the Shrinkage of the Tropics
7. Surface Topography and Hydrophobic Hydration of Biomolecules
Part 2:
8. Biochemical Evolution: Polymerization on Mineral Surfaces
9. Discovery of Oldest Known Sea-Turtle Fossil
10. On Structure and Function in the Cell Nucleus
11. Storage of Visual Information and Landmark Guidance in Ants
12. Human Cerebral Cortex: Developmental Patterns 0 to 6 Years
Part 3:
13. Virulence of Antibiotic Resistant Salmonella
14. Emergence of Multidrug-Resistant Salmonella in the US
15. Maternal Pathogenesis Produced by Lingering Fetal Cells
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1. ON THE INTERDEPENDENCE OF SCIENCE AND LAW
Stephen Breyer (Supreme Court, US) reviews the interdependence of
science and law. The practice of science depends on sound law,
the law that makes possible the free inquiry upon which science
is based. It is equally true that the law itself requires access
to sound science, since society is more and more dependent on
scientifically complex technology, and this technology underlies
legal issues of importance to everyone. We must search for law
that reflects an understanding of the relevant underlying
science, but this search is not a search for scientific
precision. One could not hope to replicate the subtleties and
uncertainties that characterize good scientific work. A judge is
not a scientist, and a courtroom is not a scientific laboratory.
Rather, the law must seek decisions that fall within the
boundaries of scientifically sound knowledge and approximately
reflect the scientific state of the art. But any effort to bring
better science into the courtroom must respect the jury's
constitutionally specified role -- even if doing so means that
from a scientific perspective an incorrect result is sometimes
produced. The American Association for the Advancement of
Science, the American Bar Association, and the Federal Judicial
Center have initiated a pilot project to test the feasibility of
increased use of court-appointed experts in cases that present
technical issues. The author commends this project.
(Science 24 Apr 98) (Science-Week 8 May 98)
2. A SCIENCE FACULTY RACIAL DISCRIMINATION CLAIM IN CANADA
In Canada, the University of Toronto is being accused of racial
discrimination against minority science faculty. A specific case
involves Kin-Yip Chun, a seismologist of Chinese descent, who
accuses the university of racial discrimination by repeatedly
denying him a tenure-track professorship. Chun joined the physics
department of the university in 1985, received no salary during
almost 10 years of service, his income derived entirely from
external research contracts. During that time, he taught
students, published 26 research papers, and attracted more than
US$1 million in research grants. A university-appointed
investigator has concluded that Chun was indeed exploited by the
physics department, and the Canadian Association of University
Teachers has stated there are aspects of the case that "arouse a
suspicion of discrimination." The case is being investigated by
the Ontario Human Rights Commission. Information supplied by a
Chun support committee can be found at the URL below.
QY: (http://www.utoronto.ca/acc/chun)
WWW
(Nature 16 Apr 98 392:638) (Science-Week 8 May 98)
3. SCIENCE AND HISTORY: THE LOST COLONY OF ROANOKE ISLAND
The "Lost Colony" of Roanoke Island refers to an early British
colony in America that was founded in 1587 and which mysteriously
vanished sometime between 1587 and 1591, when the colony's
founder returned to find the colony abandoned. The network of
moisture-sensitive tree-ring chronologies now available for the
US has recently been used to reconstruct summer drought and
wetness on a continent-wide basis from 1700 to 1978 A.D. Much
longer chronologies are available for some areas, including a
network of 800-year-long baldcypress (Taxodium distichum)
chronologies for the southeastern US. These exactly dated tree-
ring proxies can provide unique information on environmental
conditions during the early Colonial history of the eastern US.
... ... Stahle et al (5 authors at 2 installations, US) report
that tree-ring data from Virginia indicate that the Lost Colony
of Roanoke Island disappeared during the most extreme drought in
800 years (1587-1589), and that the alarming mortality and the
near abandonment of the later Jamestown colony occurred during
the driest 7 year episode in 770 years (1606-1612). The authors
suggest these extraordinary droughts can now be implicated in the
fate of the Lost Colony and in the appalling death rate during
the early occupations at Jamestown, the first permanent English
settlement in America. The authors further suggest that although
the Roanoke and Jamestown colonists have been criticized for poor
planning, poor support, and a startling indifference to their own
subsistence, the tree-ring reconstruction indicates that even the
best planned and supported colony would have been supremely
challenged by the climate conditions of 1587-1589 and 1606-1612.
QY: David W. Stahle (dstahle@comp.uark.edu)
EMAIL
(Science 24 Apr 98 280:564) (Science-Week 8 May 98)
4. ON THE PRESUMPTION OF PURITY IN MATHEMATICS
Solomon W. Golomb (University of Southern California, US)
discusses the attitudes of professional mathematicians toward
pure and applied mathematics in the context of his own
development as a mathematician. It was G.H. Hardy, in his famous
exposition *A Mathematician's Apology* (1940), who in modern
times proposed that very little of mathematics is of practical
value, and that the mathematics that is of practical value is
usually trivial. Golomb points out that today, fifty years after
Hardy's death, it seems incredible that a book so at odds with
reality was so influential for so long. Golomb then examines the
questions of when and how the concept of inviolable purity became
entrenched in many departments of mathematics by the end of the
19th century and what has happened in the last 40 years to weaken
this presumption. What has happened, essentially, is that many
branches of mathematics presumed "pure" and without application
when they were discovered have proved to be of enormous practical
significance: non-Euclidean differential geometry, group theory,
finite fields, formal mathematical logic, number theory,
topology, graph theory, and so on. Most mathematicians now
recognize the basic principle that good "pure" mathematics is
most certain to have major applications *eventually*. Finally,
Golomb presents the case for "realist" mathematics as follows: If
the Big Bang had gone slightly differently, or if we were able to
spy on an entirely different universe, the laws of physics could
be different from the ones we know, but 17 would still be a prime
number. Golomb calls Isaac Newton a realist mathematician, a
mathematician who erected no artificial barriers between theory
and applications. In the 40 years since the launching of Sputnik
and Explorer -- the watershed events that produced significant
funding by society of pure mathematics -- Golomb says most
mathematicians, including himself, have moved further from
Hardy's outlook and closer to Newton's.
(The American Scholar Spring 1998) (The Monday Review 4 May 98)
5. ON MICROQUASARS IN OUR GALAXY
If the terminal stages of star death leave a remnant star mass
greater than 3 solar masses, the ultimate gravitational collapse
will produce a black hole, a relativistic singularity. A black
hole is a localized region of space from which neither matter nor
radiation can escape. The "trapping" occurs because the requisite
escape velocity, which can be calculated from the relevant
equations, exceeds the velocity of light and is therefore
unattainable. Another view of a black hole is that it is a mass
that has collapsed to such a small volume that its gravity
prevents the escape of all radiation. Space and time essentially
have no meaning in a black hole. The boundary of the black hole
is called the "event horizon", because any event within the
boundary is invisible outside, the invisibility resulting from
the fact that no radiation can escape to be detected. The radius
of the black hole depends upon how much matter has fallen into
the region; it is called the "Schwarzchild radius", and it is
usually a few kilometers. However, massive black holes are
possible and are thought to be the source of quasars (quasi-
stellar objects), which are extremely luminous sources radiating
energy over the entire spectrum from x-rays to radio waves, and
which are apparently the oldest and most distant objects in the
universe. If quasars indeed involve black holes, the radiation is
from material just outside the black hole, and not from anything
within it. Nothing inside a black hole can get out of it. Quasar
black holes are believed to black holes of several million solar
masses. In contrast to quasar black holes, there have been
identified black holes of mere stellar mass associated with
"microquasars". ... ... 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 light.
QY: I.F. Mirabel (mirabel@discovery.saclay.cea.fr)
EMAIL
(Nature 16 Apr 98 392:673) (Science-Week 8 May 98)
6. EARTH'S OBLIQUITY AND THE SHRINKAGE OF THE TROPICS
The "obliquity" of the Earth is the angle between the plane of
the equator and the plane of the Earth's orbit, and it is quite
important in determining climate belts around the Earth's sphere.
... ... Rubincam et al (National Aeronautics and Space
Administration, US) review the periodic shrinkage of Earth's
tropical zone. In the past year, the Earth completed one
revolution around the Sun, the Moon went through its phases 13
times, and the tropic of Cancer moved another 14.7 meters south.
The tropic of Cancer is the latitude at which the Sun is overhead
at the June solstice, and that latitude is moving toward the
equator. Similarly, the tropic of Capricorn, where the Sun stands
at the December solstice, moved 14.7 meters northward. Almost
1100 square kilometers move from the tropics into the temperate
zone each year. The reason for the shrinkage is the changing
obliquity of the Earth, which is getting progressively smaller by
approximately 47.5 arc-seconds per century. Various gravitational
torques of the Sun, Moon, and other planets cause the Earth's
obliquity to oscillate with a period of approximately 41,000
years. QY: David P. Rubincam, NASA Goddard Space Flight Center,
Greenbelt, MD 20771 US.
(Sky & Telescope June 1998) (Science-Week 8 May 98)
7. SURFACE TOPOGRAPHY AND HYDROPHOBIC HYDRATION OF BIOMOLECULES
Cheng and Rossky (University of Texas Austin, US) present
computer simulations of the interactions between the polypeptide
mellitin and water. Many biomolecules are characterized by
surfaces containing extended nonpolar regions, and the
aggregation and removal of such surfaces from water is believed
to play a critical role in the biomolecular assembly in cells. A
better understanding of the hydrophobic hydration of biomolecules
may therefore yield new insights into intracellular assembly.
Conventional views hold that the hydration shell of small
hydrophobic solutes is clathrate-like, characterized by local
cage-like hydrogen-bonding structures and a distinct loss in
entropy. The hydration of extended nonpolar planar surfaces,
however, appears to involve structures that are orientationally
inverted relative to clathrate-like hydration shells, with
unsatisfied hydrogen bonds directed toward the hydrophobic
surface. The authors suggest their computer simulations
demonstrate that the two different hydration structures also
exist near a biomolecular surface, and that the two structures
are distinguished by a substantial difference in water-water
interaction enthalpy. The authors further suggest that the strong
influence of surface topography on the structure and free energy
of hydrophobic hydration is likely to hold in general, and will
be particularly important for the many biomolecules whose
surfaces contain convex patches, deep or shallow concave grooves,
and roughly planar areas.
QY: Peter J. Rossky (rossky@mail.utexas.edu)
EMAIL
(Nature 16 Apr 98 392:696) (Science-Week 8 May 98)
(continued in Part 2)
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
SCIENCE-WEEK - Part 2/3
A Free Weekly Digest of the News of Science
May 8, 1998
Contents of Part 2:
8. Biochemical Evolution: Polymerization on Mineral Surfaces
9. Discovery of Oldest Known Sea-Turtle Fossil
10. On Structure and Function in the Cell Nucleus
11. Storage of Visual Information and Landmark Guidance in Ants
12. Human Cerebral Cortex: Developmental Patterns 0 to 6 Years
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8. BIOCHEMICAL EVOLUTION: POLYMERIZATION ON MINERAL SURFACES J.
Smith (University of Chicago, US) proposes a conceptual framework
for consideration of the origins of replicating biopolymers.
Although extended Darwinian natural selection coupled with
Mendel-Watson-Crick genetic inheritance/mutation provides a
plausible framework for integrating the patchy paleontological
record with the increasingly complex biochemical zoo of the
present Earth, the actual chemical beginning of "life" still
poses major challenges. How could the first replicating and
energy-supplying molecules have been assembled from simpler
materials that were undoubtedly available on the early proto-
continents? Catalysis at mineral surfaces might generate replic-
ating biopolymers from simple chemicals supplied by meteorites,
volcanic gases, and photochemical gas reactions. But many ideas
are implausible in detail because the proposed mineral surfaces
strongly prefer water and other ionic species to organic ones.
The molecular sieve silicalite (Union Carbide; = Al-free Mobil
ZSM-5 zeolite) has a 3-dimensional 10-ring channel system whose
electrically neutral silicon-oxide surface strongly adsorbs
organic species over water, and the ZSM-5 type zeolite mutinaite
has recently been found in Antarctica. The author proposes that
zeolites with similar structures may have existed on the surface
of Earth during its life-origin phase, and that polymer migration
along weathered silicic surfaces of micrometer-wide channels of
feldspars might have led to assembly of replicating catalytic
biomolecules and perhaps primitive cellular organisms. The author
suggests that weakly metamorphosed Archaean rocks might retain
microscopic clues to the proposed mineral adsorbent/catalysts,
and that other frameworks are also possible, including ones with
laevo/dextro one-dimensional channels.
QY: Joseph V. Smith (smith@geol.uchicago.edu)
EMAIL
(Proc. Natl. Acad. Sci. US 31 Mar 98 95:3370)
(Science-Week 8 May 98)
-------------------
Related Background:
ORIGIN OF LIFE: THE PRESENT STATUS OF CHEMICAL THEORY
The essential question involved in the origin of what we call
life is how can order arise from disorder? At the present time,
this question is approached on two fronts: 1) study of the
principal features of self-organizing systems, systems in which
order does arise from disorder, systems in which order is indeed
demanded from disorder on thermodynamic grounds; and 2) study of
the detailed chemistry of such systems, the chemistry of
organization and the chemistry of components. In the case of
components, it is essential that appropriate self-organizing
components exist in the first place if they are to become self-
organized, and such candidate components are thus the focus of
much chemical research in this area. In 1953, the chemist Stanley
Miller reported what soon became a famous experiment. To water
under a gas mixture of methane, ammonia, and hydrogen, he added
an electrical discharge. After one week of continuous electrical
discharge, he found that a number of important biological
molecules, including amino acids, had been formed. Miller
proposed his experiment as a model for the conditions under which
the essential compounds necessary for life originated . The
Miller experiment was a watershed, and it began a new era of
experimentation and analysis of possible primordial components.
Coupled with this, were the new important discoveries by
astrophysicists of the presence of organic molecules in the
interstellar medium and in meteorites. In a review of origin of
life theories, P. Radetsky (Univ. of California Santa Cruz, US)
points out that the Miller theory is no longer the consensus
theory, that contemporary geologists believe the primordial
atmosphere consisted primarily of carbon dioxide and nitrogen,
which are less reactive than the gases in the Miller experiment,
and that the field is currently embroiled in controversy fueled
for the most part by an absence of hard fact. QY: Peter Radetsky,
Univ. of California Santa Cruz 408-429-4008 (Earth February
1988) (Science-Week 2 Jan 98)
-------------------
Related Background:
RNA POLYMERIZATION A FOCUS AT ORIGIN OF LIFE MEETING
If the complex molecules necessary for life originated on Earth
rather than elsewhere, then a natural question is how? How and
under what conditions did the first polymerizations occur? Under
ordinary laboratory conditions, without special outside agencies
such as catalysts, RNA monomers, for example, will not assemble
into polymers unless the monomer concentration is impossibly
large. So how was polymerization achieved on the early Earth?
Such questions are now the essential questions in the origin-of-
life branch of biological science, and at a recent regional
meeting of the American Chemical Society, a group of researchers
in this area presented results of their latest studies. David
Usher et al have used a "day-night machine", an apparatus that
exposes solutions to alternating cycles of daylight and darkness,
and have apparently found evidence of RNA polymerization from
monomers, the polymerization dependent on the alternating cooling
and heating produced by the light-dark cycles. James Ferris and
Gozen Ertem (Rensselaer Polytechnic Institute, NY US) presented
evidence that clay or pyrite minerals can catalyze polymer
formation from RNA monomers by serving as adsorption templates.
And Tom Waddell et al (University of Tennessee Chattanooga, US)
reported that if intermediates of the citric acid cycle, so vital
in biological processes, are exposed to sunlight, the production
of other intermediates in the cycle is catalyzed. The hunt for
efficient catalysts for RNA polymerization that may have been
present on primeval Earth continues. (Science 22 Aug 97)
(Science-Week 5 Sep 97)
9. DISCOVERY OF OLDEST KNOWN SEA-TURTLE FOSSIL
R. Hirayama (Teikyo Heisei University, JP) reports the discovery
of an exceptionally well-preserved skeleton of the oldest known
chelonioid (sea turtle). Reptiles constitute a primarily
terrestrial assemblage, but several groups returned to the marine
environment after the first appearance of reptiles in the
Paleozoic era. Successful diversification of the chelonioid sea
turtles, particularly during the Cretaceous period, was perhaps
one of the most important events in the history of turtles (and
marine reptiles). The fossil record of chelonioids before the
Late Cretaceous has been poorly documented. The skeleton reported
by the author is from the Early Cretaceous stage (about 110
million years before the present) of eastern Brazil. This
specimen represents a new taxon, extending the history of
chelonioids by 10 million years, and the author suggests it sheds
new light on the early evolution of the group: the details of the
discovery support the idea that the establishment of the salt-
excreting system, and the occupation of a marine habitat, may
have preceded the formation of rigid paddles in the history of
chelonioids.
QY: Ren Hirayama (renhrym@ab.mbn.or.jp)
EMAIL
(Nature 16 Apr 98 392:705) (Science-Week 8 May 98)
10. ON STRUCTURE AND FUNCTION IN THE CELL NUCLEUS
Lamond and Earnshaw (2 installations, UK) review recent progress
in understanding the organization of the cell nucleus,
highlighting in particular the dynamic aspects of nuclear
structure. First described by Brown in 1831, the cell nucleus is
one of the best known but least understood of cellular
organelles, and the structure and functional organization of the
nucleus remains a subject of energetic debate. At one extreme,
the nucleus has been proposed to have its own nucleoskeleton and
distinct organelles, while at the other extreme, it is viewed as
a largely disordered membrane-bound bag of DNA and other
molecules, in which all "structures" are no more than transient
complexes that form and disperse as a result of transcription,
replication and RNA processing activities in various regions of
the genome. Understanding in molecular detail the organizing
principles of the nucleus -- including the arrangement of
chromosomal DNA and how the synthesis, processing, assembly, and
transport of macromolecules are coordinated and regulated -- is a
major goal for cell biology. The authors conclude they are
confident that future studies will illuminate the basic
principles underlying nuclear organization and will increase our
understanding of how disruptions of this organization contribute
to human disease.
QY: Angus I. Lamond (a.i.lamond@dundee.ac.uk)
EMAIL
(Science 24 Apr 98) (Science-Week 8 May 98)
11. STORAGE OF VISUAL INFORMATION AND LANDMARK GUIDANCE IN ANTS
Diptera is the order of insects that contains flies with only one
pair of wings, and Hymenoptera is the order of insects containing
bees, wasps, and ants. ... ... Judd and Collett (Sussex Centre
for Neuroscience, UK) report a study of the visual guidance
system of ants. Under some circumstances, Diptera and Hymenoptera
learn visual shapes retinotopically, only recognizing a shape
when it is viewed by the same region of retina that was exposed
to it during learning. One use of such retinotopically stored
views is in guiding an insect's path to a familiar site. The
authors report that wood ants take several "snapshots" of a
familiar beacon from different vantage points. An ant leaving a
newly discovered food source at the base of a landmark performs a
tortuous walk back to its nest during which it periodically turns
back and faces the landmark. The ant, on revisiting the familiar
landmark, holds the edges of the landmark's image steady at
several discrete positions on its retina. These preferred retinal
positions tend to match the positions of landmark edges that the
ant captured during its preceding "learning walks". The
methodology in this investigation involved first training ants to
distinguish an upright and inverted cone, followed by fine-grain
analysis of the approaches of individual ants towards cones and
related borders.
QY: S.P.D. Judd, Sussex Centre for Neuroscience, School of
Biological Sciences, Brighton BN1 9QG, UK.
(Nature 16 Apr 98 392:710) (Science-Week 8 May 98)
12. HUMAN CEREBRAL CORTEX: DEVELOPMENTAL PATTERNS 0 TO 6 YEARS
Shankle et al (3 installations, US JP) report a statistical
analysis of the classic data of Conel on the early development of
the human cerebral cortex. The basic processes of mammalian
cerebral cortical development in early fetal life are accepted to
be fundamentally alike in all cortical regions (e.g., localized
neuron proliferations, routes of migrations, long distance
cortical connections, etc.), but there has been no research
synthesizing developmental profiles across distinct regions. A
unique source of data for such a synthesis is the work of J.L.
Conel, who from 1939 to 1967 published 8 volumes of data on the
microscopic neuroanatomical features of the human cerebral cortex
from term birth to age 72 months. Applying multivariate analysis
to the Conel data, the authors of the present report found that
the profiles for any given combination of feature and cortical
layer are remarkably similar in all regions of the brain, and
therefore the developmental patterns of different cytoarchitect-
ural regions are not distinguishable from one another. The
authors suggest their analysis indicates Conel's data are highly
consistent and reliable and should be used for studies relating
cytological development to the development of cortical functional
capabilities.
QY: William R. Shankle (rshankle@uci.edu)
EMAIL
(Proc. Natl. Acad. Sci. US 31 Mar 98 95:4023)
(Science-Week 8 May 98)
(continued in Part 3)
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
SCIENCE-WEEK - Part 3/3
A Free Weekly Digest of the News of Science
May 8, 1998
Contents of Part 3:
13. Virulence of Antibiotic Resistant Salmonella
14. Emergence of Multidrug-Resistant Salmonella in the US
15. Maternal Pathogenesis Produced by Lingering Fetal Cells
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13. VIRULENCE OF ANTIBIOTIC RESISTANT SALMONELLA
Bjorkman et al (3 authors at 2 installations, SE) report a study
of the virulence of antibiotic resistant Salmonella typhimurium.
During the last decade there has been an alarming increase in the
appearance of antibiotic-resistant bacteria as a result of an
increased use of antibiotics combined with the exceptional
ability of bacteria to develop resistance. One strategy to
reverse this development is to decrease the use of antibiotics to
promote the disappearance of the resistant bacteria present in
human and environmental reservoirs. Implicit in this reasoning is
that mutated resistant bacteria will be less viable in an
antibiotic-free environment. An associated question is whether
resistant bacteria with reduced or no virulence might accumulate
compensating mutations that restore fitness and virulence without
loss of resistance. In this study, the authors examined the
fitness of S. typhimurium in mice, and their results indicate
that most resistant mutants are less virulent than the wild type,
but that the avirulent mutants rapidly accumulate various types
of compensating mutations that restore virulence to wild-type
levels without loss of high-level resistance. The authors suggest
that if their results are general and apply to other medically
relevant pathogens, then the strategy of getting rid of
antibiotic resistant bacteria by a decreased use of antibiotics
may not be successful.
QY: Dan I. Andersson (dan.andersson@smi.ki.se)
EMAIL
(Proc. Natl. Acad. Sci. US 31 Mar 98 95:3949)
(Science-Week 8 May 98)
-------------------
Related Background:
ON THE RESISTANCE OF BACTERIA TO ANTIBIOTICS
S. Levy (Tufts University, US), in a review of recent
developments in antibiotic resistance, notes that strains of at
least 3 pathogenic bacterial species -- Enterococcus faecalis,
Mycobacterium tuberculosis, Pseudomonas aeruginosa -- have
already developed resistance to every one of the 100 antibiotic
drugs in use by clinicians. Levy says a change in attitudes of
the public and clinicians concerning the overuse of antibiotics
is badly needed, and that a reversal of increasing bacterial
resistance to antibiotics, as well as increasing resistance of
parasites, fungi, and viruses to antimicrobials and antivirals,
will require a new global awareness of the broad consequences of
anti-pathogen drug usage. QY: Stuart B. Levy, Tufts Univ. School
of Medicine 617-636-6571 (Scientific American March 1998)
(Science-Week 20 Feb 98)
-------------------
Related Background:
STUDIES SHOW MARKED INCREASE IN DRUG RESISTANCE OF MICROBES
Widespread use of antibiotics continues to force the evolution of
strains of pathogens resistant to the drugs. For example, the
incidence in the U.S. of microbes resistant to penicillin has
increased fourfold since 1994. At the May 19th International
Conference of the American Lung Association and American Thoracic
Society in San Francisco, researchers from the State University
of New York (Buffalo NY US) and the University of Iowa College of
Medicine (Iowa City IA US) found the increase in resistance of
Streptococcus pneumoniae, a common cause of respiratory
infections, to be dramatic. 10.5% of the samples were highly
resistant to antibiotics and 24.9% moderately resistant. In 1994,
those figures stood at only 3.2% and 14.1%, respectively. In the
Southeastern part of the U.S., 41% of the samples were found to
be resistant. The researchers suggest that the medical community
must be on the watch for rapidly developing epidemics caused by
antibiotic resistant strains of pathogens, and that antibiotics
themselves should be administered only when necessary if we are
to slow down the evolution of these resistant microbes.
(UPI 19 May 97)
-------------------
Related Background:
APPEARANCE OF A STAPHYLOCOCCUS STRAIN RESISTANT TO VANCOMYCIN
Staphylococcus aureus is a common pathogenic bacterium in
hospitals, and causes thousands of often fatal infections each
year. Vancomycin is an antibiotic of last resort, which is used
when all other antibiotics fail. Now the first case has appeared
in Japan of a 4 year old boy infected with a strain of
Staphylococcus aureus resistant to vancomycin. Health experts
say it is only a matter of time before the pathogen reaches U.S.
hospitals. Fred Tenover, laboratory chief of the U.S. Center for
Disease Control Hospital Infections Branch says, "The strain is
marching up the ladder of resistance... It is not a cause for
panic, but it is a cause for concern." (UPI 28 May 97)
-------------------
Related Background:
REDUCED ANTIBIOTIC USAGE LOWERS BACTERIAL RESISTANCE
To understand the mechanism of the worldwide increase in
bacterial resistance to antibiotics one need only consider that
for all biological organisms most chemical aspects are more or
less displayed as a Gaussian distribution, the so-called "normal"
or "bell-shaped" curve. What this means in the context of
applying an antibiotic to a population of a particular bacterial
species is that something like 10% or 15% of the population will
show much lower than average resistance to the drug, about 60%
will have close to the average resistance to the drug, and about
10% to 15% will show above average resistance to the drug, all
because of the way the chemistry responsible for resistance to
the drug is distributed in the population. These numbers are
variable from one species of bacteria to another, and they also
vary with the antibiotic used, but the general idea is the same.
The result of all of this is that if we use an antibiotic against
a specific bacterial population, those members of the population
that have superior resistance to the antibiotic will survive to
reproduce their genome, most of the others will be killed, and
before long we will have on our hands populations of that species
which are more or less totally resistant to the antibiotic. This
is nothing more than a concrete instance of the idea of
"selection pressure" in evolution. In 1946 about 90% of
Staphylococcus aureus (a common and dangerous pathogen bacterium)
in hospitals were killed by the antibiotic penicillin, which
first became widely available at about that time. By only 6 years
later, 75% of S. aureus caught and cultured in hospitals were
resistant to penicillin, and by the 1970s, 90% of S. aureus,
whether in hospitals or in the community, were resistant to the
drug. There are similar stories concerning other bacterial
species and other drugs, the worst scenarios evidently occurring
in hospitals; but one cannot fault hospitals, because in both
hospitals and the community antibiotics have been routinely
needlessly administered and/or over-administered, with a
consequent selection pressure that produces antibiotic-resistant
pathogens. Can the process be reversed? There may still be some
hope against bacterial species which are not already over-
whelmingly resistant. This week Helena Seppala et al (about 100
authors in FI) report that in Finland, after an organized
nationwide reduction in the use of macrolide antibiotics
(macrolides are large-ring molecules with many functional side
groups) for outpatient therapy, the resistance of group A
streptococci to the common antibiotic erythromycin dropped by
half from 16.5 per cent in 1992 to 8.5 per cent in 1996. In an
editorial in the New England Journal of Medicine, Morton N.
Swartz (Massachusetts General Hospital, Boston US) calls this "an
impressive example of how an enlightened national policy on
antibiotic use can become an effective public health measure."
QY: H. S. Seppala, Antimicrobial Research Laboratory, PO Box 57,
20521 Turku, FI (New England J. Med. 14 Aug 97)
-------------------
Related Background:
NEW MULTI-DRUG RESISTANCE OF PLAGUE PATHOGEN
Plague, also called bubonic plague or "Black Death", is a disease
with a notorious history. It is caused by the bacillus Yersinia
pestis, which infects wild rodents. The bubonic variant of the
disease is transmitted to humans from rodents by the bite of an
infected flea. Human to human transmission occurs by inhalation
of respiratory droplets spread by the cough of patients with
plague who have developed pulmonary lesions, and the result of
this is "primary pneumonic plague", which differs from "bubonic
plague" in that bubonic plague affects the lymph nodes, among
other tissues (producing "buboes", lymph node swellings). The
last plague pandemic began in Hong Kong in 1894 and spread
throughout the world. Plague still exists as an endemic disease
in many parts of the world, including the southwestern U.S.
Prevention of plague is based on rodent control, and the use of
insect repellents to minimize flea bites. Early treatment after
infection with the antibiotics streptomycin, chloramphenicol, or
tetracycline reduces mortality to less than 5%. Nevertheless,
plague is now considered a reemerging disease, with recent
epidemics in a number of countries after an absence of as much as
3 decades. The incidence of the disease has also been spreading
in the U.S. Now Marc Galimand et al (World Health Organization
and the Pasteur Institute, FR) report high-level resistance of Y.
pestis in a clinical isolate in Madagascar to multiple
antibiotics, including resistance to all the drugs recommended
for plague prophylaxis and therapy. The resistant genes are
apparently carried by a plasmid that can conjugate to other Y.
pestis isolates. So this pathogen species, heretofore considered
universally susceptible to antibiotics, is now exhibiting high
and spreadable resistance to these drugs. Epidemiologists are
alarmed and are urging an international effort to deal with the
problem. QY: Elisabeth Carniel, Institut Pasteur, 28 rue du Dr.
Roux, 75724 Paris CEDEX 15, FR. (New England J. Med. 4 Sep 97)
-------------------
Related Background:
APPARENT IRREVERSIBILITY OF BACTERIAL ANTIBIOTIC RESISTANCE
At a recent meeting of the European Society for Evolutionary
Biology (Arnhem NL), several research groups have apparently
independently confirmed the unhappy news that bacteria that have
mutated to exhibit resistance to specific antibiotics do not
evolve susceptible strains when they are no longer exposed to
these antibiotics. Bruce Levin and Bassam Tomah (Emory Univers-
ity, US) report that 25% of bacteria sampled from infant diapers
are strains of E. coli still resistant to the antibiotic strepto-
mycin, which has been rarely used during the past 30 years.
Richard Lenski (Michigan State University, US) has independently
shown that after 20,000 generations in the absence of strepto-
mycin, E. coli still carries the gene that confers resistance to
the antibiotic. The consensus is apparently that a compensatory
mutation has occurred, a mutation that compensates for the loss
of fitness produced by the gene that confers antibiotic
resistance, and which results in long-term survival of the
resistant strain. Levin suggests the same kind of compensatory
mutations "will almost certainly be found in other resistant
bacteria." The implication is that the evolutionary development
of bacterial resistance to antibiotics will not be reversed by
reducing the use of these antibiotics, which means the effective-
ness of these antibiotics is essentially irreversibly lost. QY:
B. Levin, Emory Univ., Population Genetics (404) 727-5660
(Science 24 Oct 97)
14. EMERGENCE OF MULTIDRUG-RESISTANT SALMONELLA IN THE US
Strains of salmonella that are resistant to antimicrobial agents
have become a worldwide health problem, with a distinct strain of
Salmonella enterica serotype typhimurium becoming a major cause
of illness in humans and animals in Europe, especially in the UK.
Glynn et al (6 authors at 2 installations, US) report an analysis
of data collected in the US by local and state health departments
and public health laboratories between 1979 and 1996 in national
surveys of the antimicrobial-drug resistance of salmonella. The 5
drugs involved were ampicillin, chloramphenicol, streptomycin,
sulfonamides, and tetracycline. The authors report that the
prevalence of S. typhimurium resistance to the 5 antibiotics
increased from 0.6% in 1979-1980 to 34% in 1996, and they
conclude that multi-drug resistant S. typhimurium has become a
widespread pathogen in the US. The authors suggest that more
prudent use of antimicrobial agents in farm animals and more
effective disease prevention on farms are necessary to reduce the
dissemination of this bacterial mutant and to slow the emergence
of resistance to additional antimicrobial agents in this and
other strains of salmonella.
QY: M. Kathleen Glynn, Centers for Disease Control and
Prevention, Atlanta, GA 30333 US.
(New England J. Med. 7 May 98 338:1333) (Science-Week 8 May 98)
15. MATERNAL PATHOGENESIS PRODUCED BY LINGERING FETAL CELLS
A "stem cell" is a precursor cell, a daughter cell that may
differentiate into other types. Systemic sclerosis is a
connective tissue disease of unknown origin that is characterized
by various clinical manifestations similar to graft-versus-host
disease. The highest incidence of systemic sclerosis occurs
between 45 and 55 years of age, and it is 3 to 8 times as
frequent in women as in men. Recent studies indicate that fetal
stem cells can survive in the maternal circulation many years
after childbearing, and this finding suggests that fetal cells
persisting in the maternal circulation or in maternal tissues
could be involved in the pathogenesis of systemic sclerosis by
initiating a graft-versus-host reaction. ... ... Artlett et al (3
authors at Thomas Jefferson University, US) report the use of
molecular biological techniques to test for Y-chromosome DNA
(which is male-origin DNA) extracted from peripheral-blood cells
and skin lesions from 69 women with systemic sclerosis of recent
onset. Y-chromosome DNA sequences were found in the test material
from 46% of these women, compared with 4% in normal women.
Furthermore, Y-chromosome sequences were identified in skin
biopsy specimens from 11 of 19 women with systemic sclerosis
(58%), and 9 of the 11 were known to have carried male fetuses.
Note: the methodology involves detection of only male-origin DNA
(presumed to be of fetal origin); there are no data concerning
the presence of female fetal DNA in the test material from the
patients with systemic sclerosis. The authors suggest that fetal
antimaternal graft-versus-host reactions may be involved in the
pathogenesis of systemic sclerosis in some women. QY: Sergio A.
Jimenez, Dept. of Medicine, Thomas Jefferson University, 233 S.
10th St., Philadelphia, PA 19107-5541 US.
(New England J. Med. 23 Apr 98) (Science-Week 8 May 98)
---------------------------------------------
BOOK NOTES:
J.M. Balkin: CULTURAL SOFTWARE
Yale Univ., 1998, 352p, UK25 (June)
An attempt at an original theory of cultural evolution, with
foundations in anthropology, evolutionary theory, cognitive
science, linguistics, sociology, political theory, philosophy,
social psychology, and law.
A.C. Fabian (ed.): EVOLUTION
Society, Science, and the Universe
Cambridge Univ., 1998, 186p, US22.95
A collection of essays by Stephen Jay Gould, Freeman Dyson,
Martin Rees, and others. Considers the history of biological
evolution in the context of the evolution of cultures, society,
science, and the universe.
Jane Gregory and Steve Miller: SCIENCE IN PUBLIC
Communication, Culture, and Credibility
Plenum, 1998, 294p, US29.95 CA41.95
A review of the theory and practice of communicating science to
the public. The "Public Understanding of Science" movement,
science in public culture, popular science, popularization of
science, media issues, case studies in public science, science in
museums, initiatives and activities, a protocol for science
communication. 31 pages of references and notes. The authors are
specialists in science communication at University College London
(UK).
Heinz Herrmann: FROM BIOLOGY TO SOCIOPOLITICS
Conceptual Continuity in Complex Systems
Yale Univ., 1998, 256p, UK20 (July)
Conceptual continuity proposed as a new paradigm for comparing
systems of divergent complexity, and for resolving problems in
such complex systems as human societies.
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