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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.
August 10, 2001 -- Vol. 5 Number 32
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They were gentlemen under cracked ceilings.
A.V. Hill sat with an umbrella protecting his
head from a leaking roof. Imagine doing your
work in a laboratory without airconditioning
in summer and not much heating in winter, with
not a plastic receptacle anywhere, and with
measurement of the concentration of an ion
in aqueous solution requiring days of laborious
gravimetric analysis.
-- Unknown
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Section 1
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Contents of this Issue (Full reports in Section 2):
1. IN BRIEF
Blocking messenger RNA
Gregarious behavior in desert locusts
Green tea and UV protection
Regeneration of cardiac muscle cells
Stabilization of carbenes
Chemisorption of organic compounds on silicon
Warming oceans and greenhouse gases
Missing neutrinos riddle apparently solved
2. A CRITICISM OF BEHAVIORAL AND SOCIAL SCIENCE
An anthropologist sharply criticizes other social scientists,
with accusations of fabrications and word-play and lack of
intellect, including accusations against two pioneers of
behavioral science.
3. PHAGE DISRUPTION OF BACTERIAL WALLS
Bacteriophages (bacterial viruses; phages) are the largest virus
group, with approximately 4000 different types isolated. They are
viruses that infect bacteria only, usually no more than one or a
few particular species of bacteria for each type of phage, and
they occur throughout the bacterial world and in all bacterial
habitats, even volcanic hot springs.
4. NEW METHOD FOR CHIRAL SELECTION
Researchers report evidence that a macroscopic chiral factor
(vortex motion) selects the chirality of a supramolecular
structure, with the chirality detected at the molecular level.
The authors interpret their observations in terms of hydrodynamic
and steric effects that act during the growth of supramolecular
complexes.
5. QUININE SYNTHESIS
Although quinine (6'-methoxycinchonan-9-ol) has been synthesized,
first by the legendary synthetic organic chemist R.B. Woodward
(1917-1979) in 1944, the procedure is complex, and quinine and
other clinically active alkaloids have been for the most part
obtained entirely from natural sources.
6. CHEMICAL PRINCIPLES AND ELECTRONIC STRUCTURES
The reactivity indices of electronegativity and hardness can be
used to formulate principles that guide analysis of reaction
pathways in chemical systems, and these principles are apparently
substantiated by density functional theory calculations.
7. IN FOCUS: ON GRATINGS, SPECTROSCOPY, AND HENRY ROWLAND
Until the advent of electronic feedback control technology
following the Second World War, the perfection of spectroscopy
was owing to the pleasure that Henry Augustus Rowland [1848-1901]
found in contending with physical reality, after the manner of
Galileo, with bare hands.
8. FROM THE SCIENCEWEEK ARCHIVE:
MEDICAL BIOLOGY:
ANALYSIS OF A MASS PSYCHOGENIC ILLNESS IN A HIGH SCHOOL
Epidemic hysteria, also called "mass psychogenic illness" or
"mass sociogenic illness" or "transient situational disturbance"
was first described in the Middle Ages, and it has been reported
in a variety of cultures and settings.
9. SOURCES
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Section 2
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1. IN BRIEF
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BLOCKING MESSENGER RNA
A major focus of molecular biology is now the identification of
gene function, a task that will require more effort and more time
than sequencing genomes. Brenda L. Bass (2001) discusses the
technique of RNA interference. Although this technique was
discovered only a few years ago, it is now a standard approach.
Once the sequence of a gene is known, RNA interference offers a
quick and easy method to determine its function, and the
technique is accessible to small as well as to large
laboratories. The method involves sequence-specific post-
transcriptional gene-silencing in animals and plants, using an in
vitro-synthesized double-stranded RNA homologous in sequence to
the gene to be silenced. When this in vitro double-stranded RNA
is introduced into a cell, it triggers the degradation of
messenger RNA that matches its sequence, thus effectively
shutting off the expression of the corresponding gene. From the
observed consequences of this gene-specific silencing, the
function of the gene can often be identified. RNA interference
(RNAi) was first discovered in the nematode worm C. elegans in
1998. But although the technique is now routine in studies of
gene function in a wide range or organisms, its use in mammalian
cells has not been secure. Now S.M. Elbashir et al (2001) have
demonstrated that the RNA interference technique can be used
effectively in mammalian cells. (SCI 2001 411:428,494)
------------------------------------
GREGARIOUS BEHAVIOR IN DESERT LOCUSTS
S.J. Simpson et al (2001) report on signals for gregarious
behavior in desert locusts. In many animal species, crowding
stimulates changes in physiology, behavior, and morphology, and
these changes can be interpreted as adaptations for high
population density or migration. An extreme example is density-
dependent phase polyphenism in locusts, where being kept in a
crowd stimulates individuals to change from the "shy"
cryptically-colored "solitarious" phase into the conspicuously-
colored swarm-forming "gregarious" phase. Phase transition
includes rapid behavioral change (occurring in a matter of
hours), whereas color, shape, and reproductive physiology change
more gradually. The authors conducted experiments to identify the
site of mechanosensory input in the locust that elicits the
transition to gregarious phase behavior, and they report that a
significant switch from solitarious to gregarious behavior occurs
when the outer face of a hind femur of the locust is stimulated,
but mechanical stimulation of 10 other body regions does not
result in significant behavioral change. The authors conclude
that a primary cause of the switch to behavior that seeds the
formation of locust swarms is individuals regularly touching
other individuals on the hind legs within populations that have
become concentrated by the environment. (PNAS 2001 98:3895)
------------------------------------
GREEN TEA AND UV PROTECTION
C.A. Elmets et al (2001) report a study of cutaneous
photoprotection from ultraviolet (UV) injury by green tea
polyphenols. In animal models, extracts from green tea have been
shown to be remarkably effective at reducing the severity of
adverse human health effects resulting from overexposure to UV
radiation. Although sunscreens and other photoprotective measures
have traditionally been used for this purpose, there is a need
for additional measures, and natural products are being
increasingly explored for that purpose. The study involved
treating areas of skin of normal volunteers with an extract of
green tea or one of its constituents. The authors report that
application of green tea extracts resulted in a dose-dependent
inhibition of the reddening (erythema) response evoked by UV
radiation. On histologic examination, skin treated with green tea
extracts showed a reduced number of sunburn cells and also
Langerhans cells protected from UV damage. Green tea extracts
also reduced the DNA damage that formed after UV radiation. The
polyphenolic fractions of (-)-epigallocatechin-3-gallate and (-)-
epicatechin-3-gallate were most efficient in inhibiting erythema.
The authors conclude that polyphenolic extracts of green tea are
effective chemopreventive agents for many of the adverse effects
of sunlight on human health and may thus serve as natural
alternatives for photoprotection. (JAAD 2001 44:425)
------------------------------------
REGENERATION OF CARDIAC MUSCLE CELLS
In general, an "infarct" is an area of necrosis caused by a
sudden insufficiency of blood supply, and a "myocardial
infarction" (cardiac infarction) is such damage of an area of
heart muscle, usually as a result of occlusion of a coronary
artery. A.P. Beltrami et al (2001) report evidence that human
cardiac muscle cells (myocytes) divide after myocardial
infarction. The scarring of the heart that results from
myocardial infarction has been interpreted as evidence that the
heart is composed of myocytes that are unable to divide. Recent
observations, however, have provided some evidence of
proliferation of myocytes in the adult heart. Beltrami and
colleagues studied the extent of mitosis among myocytes after
myocardial infarction in humans, and they suggest that their
results challenge the dogma that the adult heart is a postmitotic
organ, and that their results raise the possibility that the
regeneration of myocytes may contribute to the increase in muscle
mass of the myocardium. The adult heart apparently has a
subpopulation of myocytes that are not terminally differentiated,
and these myocytes evidently reenter the cell cycle and undergo
nuclear mitotic division early after infarction. The number of
cell-cycling myocytes is significantly larger in the zone
bordering the infarct than in the distant myocardium.
(NEJM 2001 344:1750)
------------------------------------
STABILIZATION OF CARBENES
The term "carbene" refers to chemical species of the type
R(sub2)C, in which the carbon atom has two electrons that do not
form bonds. Methylene is the simplest example. Carbenes are
highly reactive and ordinarily exist only as transient
intermediates in certain organic reactions. In general, carbenes
attack double bonds to give cyclopropane derivatives, and they
also cause insertion reactions in which the carbene group is
inserted between the carbon and hydrogen of a C-H bond. Curt
Wentrup (2001) discusses carbene chemistry. Although stable free
radicals were first prepared in 1900, stable carbenes have long
remained elusive. Carbenes have become well-established synthetic
intermediates, their high reactivity making them versatile
targets for preparative, mechanistic, and theoretical studies.
Now Sole et al (2001) report an important synthetic advance that
enables the preparation of unusually stable yet highly reactive
carbenes, and related carbene species may find future
applications as efficient catalysts. Certain carbenes have been
shown to form exceptionally strong bonds with virtually all the
transition elements and many lanthanides, and carbenes may thus
surpass the ubiquitous phosphine ligands in organometallic
catalytic chemistry. (SCI 2001 292:1846,1901)
------------------------------------
CHEMISORPTION OF ORGANIC COMPOUNDS ON SILICON
The phenomenon of "chemisorption" involves the adsorption of a
single layer of molecules, atoms, or ions to a surface with
chemical (covalent) bonds rather than van der Waals forces
responsible for the interactions. J.A. Barriocanal and D.J. Doren
(2001) discuss chemisorption on silicon. Interest in the
chemisorption of organic molecules on semiconductor surfaces has
been energized by a variety of present and potential
applications. The controlled deposition of organic films on
surfaces has been used in sensor technology, combinatorial
analysis, optoelectronic devices, nonlinear optic materials, and
microelectronics. By developing new reactions that might be used
to form well-defined layers on silicon or other semiconductor
surfaces, new methods may be developed that take advantage of the
particular properties of these surfaces. In particular, the
electronic response, ready availability of well-ordered single
crystal surfaces, inherent orientational order of the surface
atoms, and the existing highly developed technology for accurate
surface patterning provide unique opportunities for developing
new devices on silicon. These ideas have motivated a large number
of recent theoretical and experimental investigations on the
attachment chemistry of organic molecules on silicon surfaces.
Studies have indicated that organic molecules with pi bonds can
react with the Si(100) surface dimer bond by a variety of
cycloaddition mechanisms. (JACS 2001 123:7340)
------------------------------------
WARMING OCEANS AND GREENHOUSE GASES
Barbara Goss Levi (2001) discusses warming of the oceans
apparently linked to atmospheric greenhouse gases. Global surface
temperatures rose in the last century approximately 0.6 degrees
Celsius, according to a recent report from the Intergovernmental
Panel on Climate Change (IPCC). That estimate was based on
observations of surface air temperatures and sea surface
temperatures, the most commonly used measures of climate change.
If trapped greenhouse infrared radiation is heating the
atmosphere, it should also warm the oceans as well. The oceans
cover nearly three-fourths of the Earth's surface and have the
greatest capacity to store heat of any component of the climate
system. But detailed studies of ocean heat storage have been
hindered by lack of data on subsurface temperatures. Now an
expanded data set for ocean temperatures has enabled climate
modelers to compare predicted heating of the ocean with
observations during the past 40 years. The conclusion is that
neither changes in solar irradiance nor geothermal heating can
come close to supplying the heat required to cause the ocean
temperature changes seen over the past 40 years, and thus
anthropogenic sources as the only explanation. In addition, a
recent estimate suggests that considering the large thermal
inertia of the oceans, even if man-made greenhouse gas emissions
were to cease immediately, heat coming out of the oceans would
continue to raise atmospheric temperatures by an additional 1
degree Celsius before the system equilibrated. (PT 2001 June)
------------------------------------
MISSING NEUTRINOS RIDDLE APPARENTLY SOLVED
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. One of the best sources of neutrinos should
be the nuclear reactions in our own Sun. At the present time, the
fluxes of solar neutrinos measured by various detector
installations have been no more than 60% of that predicted by
theory, and the deficits are a puzzle. 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"). The apparent solar neutrino deficit
could be explained if some electron neutrinos were changing into
tau or muon neutrinos en route to Earth, since neutrino detectors
are particularly sensitive to electron neutrinos. Now the Sudbury
Neutrino Observatory in Canada, a joint venture of Canada, the
US, and the UK, has apparently solved the puzzle by accurately
measuring the flux of electron neutrinos reaching the Earth. By
comparing this flux with those measured by the other more general
neutrino detectors, the Sudbury team concludes that some electron
neutrinos emitted by the Sun are indeed switching flavors.
(NAT 2001 411:877)
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2. A CRITICISM OF BEHAVIORAL AND SOCIAL SCIENCE
Although it sometimes happens that social scientists
publish diatribes against other social scientists in journals
devoted to one or more of the social sciences, it is not common
to find such critiques by social scientists in journals devoted
primarily to physics, chemistry, and biology. Melvin Konner, an
anthropologist at Emory University (US), who identifies himself
as a social scientist, presents an essay critical of people and
ideas in the social sciences, with much of the essay quite
controversial. Konner makes the following points:
1) Concerning Sigmund Freud (1856-1939), Konner states:
"There is little evidence that a process akin to fixation ever
occurs in childhood, least of all in the anal realm...
Fortunately for civilization, orderly people do exist. The trait
runs in families, so it is probably partly genetic, although it
undoubtedly also rests on patterns of child-rearing... Freud
invented a mental process out of whole cloth..." [Editor's note:
These are strong words, an accusation of misconduct, that Freud
fabricated his theories of child development with no evidence at
all. After nearly 100 years, Freud's theories may no longer be
fashionable, but most social scientists do not accuse Freud of
fabrication. There are certainly stages in child development, but
what one calls these stages and which variables and behaviors are
the focus of scientific attention are more a matter of fashion
than of discriminating reality. There is a difference between
inventing something out of whole cloth, i.e., deliberate
fallacious fabrication, and a falling out of fashion. In
addition, Konner's idea that the appearance of a behavioral trait
in families is evidence that the trait is probably genetic --
that idea is a fallacy. Behavioral traits are under environmental
constraints, which means sets of variables imposed by culture,
economics, and family relations, all of which variables can
continue through generations. Familial behavior by itself is no
basis for an assumption of an involvement of genetic
inheritance.]
2) Concerning the experimental psychologist B.F. Skinner
(1904-1990), Konner states: "[Skinner] and his followers grandly
ignored brain science, which had become pretty heavy sledding.
But some kind of justification for ignoring it was needed,
because the brain is, after all, the organ that generates
behavior. So the brain became a _black box_, and for all intents
and purposes an empty one." [Editor's note: Skinner's most
influential contributions to experimental psychology were
formulated in _Behavior of Organisms_ (1938), _Walden Two_
(1948), and _Science and Human Behavior_ (1953). At the time
Skinner made his greatest impact (1940-1960), there was no such
thing as "brain science", and the terms "neuroscience",
"neurobiology", and "cognitive science" were uncommon and in most
places nonexistent. What is today called "neuroscience" was in
the 1940s and 1950s a relatively primitive scientific endeavor,
with comparatively little understanding of nerve cells and neural
circuits and their possible relations to various forms of
behavior. At that time, not enough was known in what we now call
"brain science" that could be useful in studies of behavior. Both
biologists and behavioral scientists were at that time struggling
with various experimental approaches to behavior, and "brain
science" had little to offer. Skinner's contribution in those
years was to present a paradigm for objective experimental
research on animal and human behavior, the paradigm essentially
involving an attempt to establish the rules relating input to
output of the observed organism. Skinner did not invent the term
"black box" -- the term was then in current use by information
engineers, who were at that time struggling to understand the
input-output relations of information systems. Skinner was
awarded the US National Medal of Science in 1968, and currently
one of his best known experimental inventions, the "Skinner box"
is widely used in pharmaceutical research for observing how drugs
may modify animal behavior. Konner's apparent view that "brain
science" was too complicated for Skinner's talents is an insult
to both Skinner and the generation of experimental psychologists
who worked with his methods (some of whom later became
neurobiologists who made important contributions to
neuroscience).]
3) Konner states: "Now geneticists with their knockouts are
picking learning apart at the macromolecular level -- and, sure
enough, genes for learning do exist." [Editor's note: No gene for
"learning" of any kind, in animals or humans, has ever been
identified. What have been identified by "knockout" experiments
are certain genes for specific proteins apparently necessary for
certain neural or other cellular events related to an apparent
learning process. As an extreme example, if the absence of a
certain gene results in blindness in a child, and that child
cannot learn to read, is that gene a "learning" gene?]
4) Konner concludes: "Physics cannot explain biology, and
complexity theory tells us that we will not get the answers we
need about mind and culture merely by reasoning upward from
below... We social scientists should stop our silly word-play and
hit the biology books." [Editor's note: It may be true that
current physics cannot explain biology (or even mesoscopic
emergent phenomena), but it is also true that "complexity
theory", as known in the natural sciences, is not a reasonable
basis for evaluating strategies of research on mind and culture.
Concerning Konner's call for an end to word-play, we heartily
agree -- but we also suggest more attention to the history and
context of the work of dead scientists might be useful.]
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Melvin Konner: Bad words.
(NAT: 2001 411:743)
QY: Melvin Konner: Department of Anthropology, Emory University,
Atlanta, GA 30322 US.
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Summary by SCIENCE-WEEK http://scienceweek.com 10Aug01
For more information: http://scienceweek.com/swfr.htm
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3. PHAGE DISRUPTION OF BACTERIAL WALLS
Bacteriophages (bacterial viruses; phages) are the largest
virus group, with approximately 4000 different types isolated.
They are viruses that infect bacteria only, usually no more than
one or a few particular species of bacteria for each type of
phage, and they occur throughout the bacterial world and in all
bacterial habitats, even volcanic hot springs. Their dimensions
are on the order of 50 to 200 nanometers, depending on phage
type.
Bacteriophages were discovered independently by Frederick W
Twort (1877-1950) in 1915 and Felix d'Herelle (1873-1949) in
1917. It was D'Herelle who coined the term "bacteriophage"
(bacteria-eater) to describe the bacteriocidal action of the
virus. Neither discovery involved direct observation of
bacteriophages; instead, clear spots in bacterial culture films
were recognized (particularly by d'Herelle) as indicating the
presence of an organism killing bacteria.
In general, phages destroy or genetically modify bacteria,
with destruction caused by disintegration produced by disruption
of cell walls (lysis) of infected bacteria. Alternatively,
surviving bacteria can become phage-infected without lysis and
simply acquire new properties as a consequence of incorporation
of phage DNA into the bacterial genome.
Phages consist essentially of nucleic acid (DNA or RNA), a
protein coat (capsid), and, in some cases, lipid. Four structural
groups of phages have been categorized: a) isometric particles
with cubic symmetry; b) helical filaments or rods; c) tailed
phages with cubic capsids (the "heads") and helical tails; d)
pleomorphic particles without definite structure. When capsids
with cubic symmetry are present, these are icosahedra or related
bodies.
Phages typically adsorb to specific receptors on the
bacterial cell wall, but also to other parts of bacteria (e.g.,
to flagella). Most phages have apparent fixation organelles such
as fibers, spikes, or adsorption proteins. Tailed phages have
molecular devices for injecting their nucleic acid into the
bacterial host cell. A typical lysis cycle (lytic cycle) involves
a latent period of 20 to 40 minutes after phage infection of a
bacterium, the latent period ending in the release of 50 to 200
new phages, with the release accomplished by lysis (bursting) of
the host cell.
Phage morphogenesis, always inside a host cell, is a complex
and highly ordered process which may involve separate pathways
for different phage constituents. In tailed and most cubic
phages, phage nucleic acid enters capsids after the capsids are
formed. In other types of phages, the capsid condenses around the
phage nucleic acid. In still other types of phages, the capsid
and nucleic acid assemble at the host-cell periphery as the virus
particle is extruded.
It is believed that bacteriophages came into existence
perhaps earlier than 3 billion years ago, apparently before the
separation of bacteria into two kingdoms (eubacteria and
archaebacteria), with tailed phages probably originating first.
Phage viruses such as the T4 phage, with its jointed "legs" and
injection apparatus that moves its genome into the interior of a
bacterial cell, are among the most fascinating replicating
supramolecular systems known to biologists.
... ... Graham F. Hatfull (University of Pittsburgh, US)
discusses current research on phage lysis of bacteria. Lytic
bacteriophages face a conundrum: Once the invading phage has
replicated inside the bacterial host cell, how can its progeny
escape from the bacterium to infect other cells? Most bacteria
are surrounded by a tough wall composed of a cross-linked
peptide-sugar (peptidoglycan) matrix that protects the bacterial
cell membrane and that helps to maintain the shape of the
bacterium. Building and maintaining this peptidoglycan matrix is
problematic for bacteria because the wall must be strong enough
to withstand the osmotic pressure from within, yet flexible
enough to be constantly remodeled as the bacterium divides and
grows. T.G. Bernhardt et al (2001) have demonstrated that some
bacteriophages have adopted strategies to block bacterial enzymes
in the peptidoglycan synthesis pathway. It is already known that
other phages produce their own enzymes to smash through bacterial
cell walls and permeabilize bacterial cell membranes. Lysis of
bacterial walls needs to be closely coordinated with virus
replication and the assembly of viral progeny, since premature
rupture of the bacterial membrane and wall would kill forming
phage progeny by stopping the assembly process.
-----------
Graham F. Hatfull: The great escape.
(SCI 2001 292:2263)
QY: Graham F. Hatfull: gfh@pitt.edu
-----------
T.G. Bernhardt et al: A protein antibiotic in the phage Q-beta
virion: Diversity in lysis targets.
(SCI 2001 292:2326)
QY: Ryland Young: ryland@tamu.edu
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 10Aug01
For more information: http://scienceweek.com/swfr.htm
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4. NEW METHOD FOR CHIRAL SELECTION
One of the great puzzles of biology is the homochirality of most
amino acids and sugars present in biological systems. In general,
chirality is a property of certain asymmetric objects such that
the object and its mirror image cannot be superimposed one on the
other while both objects are restricted to the same plane (e.g.,
a left- and right-handed glove). In chemistry, chiral molecules
are optically active, a phase of each form rotating the plane of
incident polarized light. The two possible forms are called
"optical isomers", and each form is called an "enantiomer". An
equal mixture of the two forms is called a "racemic mixture".
Homochirality is the preference of a process or system for a
single optical isomer in a pair of isomers. Optically active
substances are termed "dextrorotatory" (the D- form; the + form)
or "levorotatory" (the L- form; the - form) according to whether
the plane of polarization of the incident polarized light is
rotated to the right or to the left with respect to the direction
of incidence of the light. The great puzzle in biology is that
nearly all amino acids in biological systems are of the L- form,
while nearly all sugars are of the D- form. (Glycine is the only
biological amino acid that is not chiral). The question is how
did this arise?
... ... J.M. Ribo et al (5 authors at University of Barcelona,
ES) report on the experimental induction of chirality by
vortices, the authors making the following points:
1) The authors point out that in the context of
crystallization, it is known that stirring can lead to
enantiomeric excess, but there is no chirality sign selection,
because the actual handedness of crystals produced in a single
experiment is unpredictable. Apart from the context of
crystallization, the spontaneous appearance of chirality,
although also without sign induction, has been reported in
aggregation processes of both *thermotropic and lyotropic liquid
crystals.
2) The authors report statistically robust experimental
evidence that a macroscopic chiral factor (vortex motion) selects
the chirality of a supramolecular structure, with the chirality
detected at the molecular level. The experimental system
consisted of diluted solutions of homoassociates of diprotonated
meso-sulfonatophenyl substituted porphyrins, which at higher
concentrations give colloid-like solutions that can form
lyotropic liquid-crystal structures. The authors interpret their
observations in terms of hydrodynamic and steric effects that act
during the growth of supramolecular homoassociates, their
analysis taking into account the specific binding characteristics
of the achiral porphyrin units.
... ... In a commentary on this work, Ben L. Feringa (University
of Groningen, NL) states: "There are many theories regarding the
origin of biomolecular homochirality, from photochemistry to the
*electroweak force. It has been suggested that vortex motion
during key aggregation processes at some stage of chemical
evolution may have led to biomolecular homochirality. Ribo et al
provide some support for this theory. More experimental work is
needed to establish whether we must consider simple stirring as a
serious candidate for chiral selection in prebiotic stages of
evolution. This promises to be an exciting endeavor."
-----------
J.M. Ribo et al: Chiral sign induction by vortices during the
formation of mesophases in stirred solutions.
(SCI 2001 292:2063)
QY: Josep M. Ribo: jmr@qo.ub.es
-----------
Ben L. Feringa: A new twist on chirality.
(SCI 2001 292:2021)
QY: Ben L. Feringa: b.l.feringa@chem.rug.nl
-----------
Text Notes:
... ... *thermotropic and lyotropic liquid crystals: Certain
liquids may have short-range order in one direction and
long-range order in another direction: these comprise the "liquid
crystals". "Thermotropic liquid crystals" are liquid crystals
prepared by heating or cooling: the liquid-crystal state occurs
only within a certain temperature range. "Lyotropic liquid
crystals" are liquid crystals prepared by mixing two or more
components at certain concentrations.
... ... *electroweak force: "Electroweak theory" is essentially
the mathematical unification of the electromagnetic force and the
nuclear weak force. The nuclear weak interactions are the
interactions involved in radioactive decay.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 10Aug01
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
POLARIZED STARLIGHT AND AMINO ACID HOMOCHIRALITY
... Is the basis of biological homochirality terrestrial or
extraterrestrial? Stuart Clark (University of Hertfordshire, UK)
presents a review of recent astronomical observations that
suggest a solution to the puzzle, the author making the following
points:
1) The author suggests that the nature of the starlight
present when the Earth first formed may be responsible for the
asymmetry of the amino acids now found in all living systems. In
general, the idea is that bombardment of comets, large and small,
brought water, gases, and a number of other volatile compounds to
Earth billions of years ago, and the rain of this material from
space may have seeded the young planet with a preponderance of L-
amino acids.
2) The author points out that the decades old controversy
concerning the *Murchison meteorite was finally settled in 1997
when it was confirmed that L-alanine is twice as abundant in the
meteorite as its optical isomer, that L-glutamic acid is 3 times
as abundant. The previous ambiguities that had caused some
researchers to consider the amino acids in the meteorite in
racemic mixture are now resolved, and the author suggests that
the asymmetries in the meteorite make it almost certain that the
Solar System formed with an excess of amino acids (see background
material below).
3) The author delineates some of the observational evidence
concerning circularly polarized infrared starlight associated
with certain young stars (see background material below).
Circularly polarized ultraviolet light is of special significance
in this context, since if a racemic mixture is subjected to
circularly polarized ultraviolet light, under the proper
conditions, one of the isomers can be preferentially destroyed
(asymmetric photolysis) (see background material below).
Theoretical work suggests that dust grains associated with stars
can indeed generate circularly polarized radiation at both
visible and ultraviolet wavelengths, as well as in the infrared
part of the spectrum. The general idea is that circularly
polarized light forms when initially unpolarized or plane
polarized starlight is scattered by a group of spinning dust
particles oriented by a local magnetic field.
4) The author suggests that planets forming around stars in
regions bathed in ultraviolet light with high circular
polarization will naturally incorporate amino acids with
enantiomeric excesses of one sort or the other, and that the same
probably held true for Earth approximately 5 billion years ago.
The author suggests that one consequence of this hypothesis is
that if carbon-based life exists on extrasolar planets, a
biochemistry based on D- amino acids could well be the rule.
-----------
Stuart Clark: Polarized starlight and the handedness of life.
(AS 1999 87:336)
QY: Stuart Clark: sclark@star.herts.ac.uk
-----------
Text Notes:
... ... *Murchison meteorite: A *carbonaceous chondrite that fell
in 1969 near Murchison, Australia. Analysis of the interior of
the meteorite revealed evidence of amino acids.
... ... *carbonaceous chondrite: "Stony" meteorites (aerolites)
are meteorites formed solely of rock-forming silicates, and
chondrites are a type of stony meteorite consisting of an
agglomeration of millimeter-sized globules (chondrules) that are
thought to be unchanged since the original condensation out of
the nebula from which the Sun and Solar System formed. A
carbonaceous chondrite is a chondritic meteorite that contains a
relatively large amount of carbon, with a resultant dark
appearance.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 20Aug99
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
STELLAR CIRCULAR POLARIZATION AND BIOMOLECULAR HOMOCHIRALITY
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. In the laboratory, high
levels of *enantiomeric excess in *racemic substances can be
produced by asymmetric photolysis by circularly polarized light.
Biological molecules exhibit extensive *homochirality (e.g.,
living systems use almost exclusively L-amino acids and D-
sugars), and this has been a puzzle since its discovery in the
19th century. It has been suggested that homochirality may be a
prerequisite for the origin of life, and a number of processes
have been proposed that may have produced enantiomeric excess in
prebiotic organic molecules, including the action of circular
polarization from the daylight sky, but these effects are
considered too small to account for homochirality. Another view
is that the origin of homochirality is extraterrestrial, and
apparent support for this view has been provided by the recent
discovery of an excess of L-amino acids in the *Murchison
meteorite. ... ... Bailey et al (8 authors at 4 installations, AU
UK FR JP) now report strong infrared circular polarization
resulting from dust scattering in *reflection nebula in an Orion
star formation region (OMC-1), and the authors suggest that
circular polarization at shorter wavelengths might have been
important in inducing chiral asymmetry in interstellar organic
molecules that could be subsequently delivered to the early Earth
by comets, interplanetary dust particles, or meteors. The authors
suggest this could account for the excess of L-amino acids found
in the Murchison meteorite, and could explain the origin of the
homochirality of biological molecules. The authors conclude:
"Whether a very high enantiomeric excess is a prerequisite for
the origin of life, or a very small effect is amplified in the
process, the ultimate source [of the excess] is likely to be of
extraterrestrial origin."
-----------
QY: Jeremy Bailey: Anglo-Australian Observatory, PO Box 296,
Epping, New South Wales 2121, AU.
(SCI 1998 281:672) (SW 21 Aug 98)
-------------------
Related Background:
... ... *enantiomeric: In chemistry, an enantiomer is a compound
whose structure is not superimposable on its mirror image, the
compound being one of a pair of optical isomers, each of which
interacts differently with polarized light (i.e., shows optical
activity). A mixture of two optical isomers in equal amounts is
called a *racemic mixture, and racemic mixtures do not show
optical activity. A reactant or process that produces an
enantiomeric excess is simply a reactant or process that produces
or selects one enantiomer in excess over the other enantiomer.
... ... *racemic: (see *enantiomeric)
... ... *homochirality: Chirality is a property of certain
asymmetric molecules (or of any object), the property being that
the mirror images of the molecules cannot be superimposed one on
the other while facing in the same direction. Homochirality is
the preference of a process or system for a single optical isomer
in a pair of isomers.
... ... *Murchison meteorite: This meteorite, which fell near
Murchison AU in 1969, contains 8 amino acids and the nucleotide
bases adenine, guanine, and uracil.
... ... *reflection nebula: A bright cloud of interstellar gas
and dust that lies in the vicinity of a star or stellar group,
with the starlight scattered in all directions by the dust
grains, and the scattered light visible because of the high
density of the dust.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 21Aug98
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
POSSIBLE EXPLANATION FOR LEVOROTATORY AMINO ACIDS IN BIOlOGY
A chiral molecule is an asymmetric molecule that cannot be super-
imposed on its mirror image. The molecule has two forms, called
enantiomorphs, that are mirror images of each other, the
solutions of which rotate the plane of polarized light in
different directions, left or right, making the enantiomers
levorotatory or dextrorotatory. Only levorotatory amino acids are
present in biological systems, and the reason for this is
unknown. M. H. Engel and S. A. Macko (University of Oklahoma, US;
University of Virginia, US) now report that individual amino-acid
enantiomers from the Murchison meteorite contain higher
concentrations of the nitrogen isotope N(15) compared to similar
materials on Earth. The authors suggest this confirms that the
asymmetries in enantiomorph concentrations in the meteorite are
extraterrestrial in origin, and indicates an extraterrestrial
source for an L-enantiomeric excess in our solar system that may
predate the origin of life on Earth.
-----------
QY: M. H. Engel: ab1635@ou.edu
(NAT 18 Sep 97) (SW 3 Oct 97)
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5. QUININE SYNTHESIS
The disease malaria is caused by a protozoan parasite of the
genus Plasmodium, and it is one of the most dangerous diseases
infecting human populations. Approximately 300 million to 500
million people are infected annually, and 1.5 million to 2.7
million lives are lost to malaria each year, with most deaths
occurring among children in sub-Saharan Africa. Of the 4 species
that cause malaria in humans, P. falciparum is the greatest cause
of infection and mortality. The growing resistance of the malaria
parasite to drugs and the resistance of mosquitoes to
insecticides have resulted in a current resurgence of malaria in
many parts of the world and a pressing need for vaccines and new
drugs.
Malaria is an ancient infection, noted in some of the West's
earliest medical records in the 5th century BC, when Hippocrates
(460-370 BC) differentiated malarial fevers into three types
according to their temporal cycles. The first appearance of
malaria in the Americas is not known, but it is believed highly
probable that malaria was a post-Columbian importation. Several
severe epidemics of malaria were first noted in 1493.
"Cinchona" is a genus of approximately 40 species of plants,
mostly trees, the plants native to the Andes of South America.
The chief alkaloid of cinchona is quinine, and already in the
17th century, cinchona was known in Peru as a treatment for
malaria and publicized as a treatment for malaria in Europe by
Thomas Syndenham (1624-1689). Jesuit priests were the main
importers and distributors of cinchona in Europe, and cinchona
was known in Europe as "Jesuit's bark". In 1820, Pierre Pelletier
(1788-1842) and Joseph Cavantou (1795-1877) isolated quinine from
cinchona.
Although quinine (6'-methoxycinchonan-9-ol) has been
synthesized, first by the legendary synthetic organic chemist
R.B. Woodward (1917-1979) in 1944, the procedure is complex, and
quinine and other clinically active alkaloids have been for the
most part obtained entirely from natural sources. Cinchona
contains a mixture of more than 20 alkaloids, the
pharmacologically most important of which are two pairs of
optical isomers, quinine and quinidine, and cinchonidine and
cinchonine.
The quinine molecule contains a quinoline group attached
through a secondary alcohol linkage to a quinuclidine ring. A
methoxy side chain is attached to the quinoline ring and a vinyl
to the quinuclidine. Quinidine has the same structure as quinine
except for the steric configuration of the secondary alcohol
group. As an antimalarial, quinidine is both more potent and more
toxic than quinine.
Quinine acts by interfering with the growth and reproduction
of the malarial parasite, apparently by preventing the parasite
from oxidizing glucose. One of the main disadvantages of quinine
as a clinical drug is that it kills only the malarial parasites
that inhabit red blood cells, and not the parasites in other
types of host cells. The result is that the parasites persist and
eventually reinvade red blood cells to precipitate a second
malarial attack.
Considering its utility and chemical complexity, the
laboratory synthesis of quinine has been a classic challenge to
organic chemists.
... ... Steven M. Weinreb (Pennsylvania State University, US)
presents a commentary on a new synthesis of quinine by G. Stork
et al (JACS 2001 123:3239), the author (Weinreb) making the
following points:
1) Weinreb points out that the famous wartime synthesis of
quinine claimed by Woodward and Doering in 1944 was in response
to limited supplies of the natural drug. But Woodward and Doering
achieved only a partial synthesis of the compound, making the
intermediate compound homomeroquinene, and relying on a
previously reported sequence for turning this into the final
product.
2) Later work by G. Grethe et al (1978) produced a full
synthesis of quinine, but the method could not control the
crucial arrangement of atoms around two central carbons. This
meant that several structural variations (stereoisomers) of
quinine were produced, which then had to be separated from the
active drug.
3) G. Stork et al (2001) have now succeeded in synthesizing
quinine by a different route, which involves a more complex
intermediate, but which yields the correct configuration at the
two central carbons.
4) Weinreb concludes: "It is unlikely that total synthesis
of quinine will ever provide an economical supply of the drug.
Nevertheless, the lessons in synthetic methodology and strategy
learned over the years [by] the many chemists who have worked on
quinine have been significant."
-----------
Steven M. Weinreb: Synthetic lessons from quinine.
(NAT 2001 411:429)
QY: Steven M. Weinreb: smw@chem.psu.edu
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 10Aug01
For more information: http://scienceweek.com/swfr.htm
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6. CHEMICAL PRINCIPLES AND ELECTRONIC STRUCTURES
The term "ionization potential" refers to the minimum energy
required to remove an electron from a specified atom or molecule
to a distance at which there is effectively no electrostatic
interaction.
The term "electron affinity" refers to the energy change
occurring when an atom or molecule gains an electron to form a
negative ion.
In general, the electron cloud that is conceived to bond two
atoms is not symmetrical except when the two atoms are identical
and have the same substituents. The electron cloud is necessarily
distorted toward one side of the bond or the other, depending on
which atom (nucleus plus electrons) maintains the greater
attraction for the electron cloud. This attraction is called
"electronegativity". There are various schemes for quantifying
electronegativity, in the search for principles that may predict
chemical reactivity, and one scheme, discussed below, is to
consider the electronegativity as simply the average of the
ionization potential and the electron affinity.
In 1923, in a general theory of acids and bases, G.N. Lewis
(1875-1946) introduced the concept that an acid is a substance
that can accept an electron pair, and a base is a substance that
can donate an electron pair; these are now the definitions of a
"Lewis acid" and a "Lewis base". Beginning in the 1960s, as a
further generalization, R.G. Pearson and others classified Lewis
acids and Lewis bases into "hard" and "soft" categories. As a
rule, hard acids react preferentially with hard bases, and soft
acids react preferentially with soft bases. The terms "hard" and
"soft" were chosen to suggest that the atomic structures
associated with hard acids and hard bases are rigid and
impenetrable, whereas structures associated with soft acids and
soft bases are more readily deformable. Although the dividing
line between the hard and soft categories is not sharp, and the
theoretical basis for the division is still obscure, much factual
information can apparently be coordinated on the basis of
preferential reactions of hard acids with hard bases and soft
acids with soft bases.
For quantitative electron structure analysis of many types
of chemical entities, the current method of choice is "density
functional theory", due to Kohn, Hohenberg, and Sham. Its name
comes from its predicted connection between the total ground
state electronic energy of a system and the electronic charge
density. The theory was first proposed in 1964, and has since
been useful as a simplifying alternative to more rigorous but
intractable many-electron wavefunction calculations. In general,
in density functional theory, it is the electron density which is
the fundamental variable: the ground state of a system is defined
by that electron density distribution which minimizes the total
energy. In this approach, once the ground state electron density
is known, all other ground state properties (lattice constants,
cohesive energies, etc.) follow, at least in principle. In
mathematics, a "functional" is a function whose value depends on
the set of all values of another function. In density functional
theory, the ground state properties of a system are functionals
of the ground state electron density function. Walter Kohn
received the Nobel Prize in Chemistry in 1998 for his development
of density functional theory.
... ... P.K. Chattaraj and B. Maiti (Indian Institute of
Technology, IN) discuss electronic structure principles from a
chemical standpoint, the authors making the following points:
1) The authors point out that important chemical reactivity
parameters such as electronegativity and hardness are defined
within density functional theory. Originally, the concept of
"electronegativity" was introduced by Linus Pauling (1901-1994)
as the power of an atom in a molecule to attract electrons to
itself. The concept of "hardness" was introduced by R.G. Pearson
in his hard-soft acid-base principle, which states that "hard
likes hard and soft likes soft". Acids, the acceptors of
electrons, are termed hard if they do not have easily excitable
outer electrons and have small sizes and high positive charges;
bases, the donors of electrons, are called hard if they have low
polarizabilities and high electronegativity values, are difficult
to oxidize, and are associated with empty high-energy orbitals.
Otherwise, they are termed "soft". Electronegativity and hardness
can be defined as the following:
Electronegativity =~ (I + A)/2
Hardness =~ (I - A)/2
where (I) is the ionization potential, (A) is the electron
affinity of the atom or molecule, and (=~) signifies a numerical
approximation.
2) The authors point out that the reactivity indices of
electronegativity and hardness are better appreciated in terms of
associated electronic structure principles. Electronegativity
difference is the major driving force behind the electron-
transfer process in chemical reactions. Electrons are transferred
from a species of lower electronegativity to one with higher
electronegativity until the electronegativity values of the two
species become equal. Within a stable molecule, all the
constituent atoms have the same electronegativity value, which is
approximately equal to the geometric mean of the
electronegativities of the isolated atoms.
3) An important hardness-related principle is the "maximum
hardness principle", which states that it is an apparent rule of
nature that molecules arrange themselves so as to be as hard as
possible. Formal proofs of the electronegativity equalization and
the maximum hardness principles are provided by density
functional theory, and it has been demonstrated that the validity
of the electronegativity equalization principle demands the
validity of the maximum hardness principle. The validity of both
principles has been tested in physicochemical processes. In
general, a stable state (minimum energy configuration) or a
favorable process is associated with maximum hardness and minimum
polarizability, and a transition state is associated with minimum
hardness and maximum polarizability.
-----------
P.K. Chattaraj and B. Maiti: Electronic structure principles and
atomic shell structure.
(JCE 2001 78:811)
QY: P.K. Chattaraj: pkc@chem.iitkgp.ernet.in
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 10Aug01
For more information: http://scienceweek.com/swfr.htm
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7. IN FOCUS: ON GRATINGS, SPECTROSCOPY, AND HENRY ROWLAND
"The precision of spectroscopy depends ultimately upon the
precision of some human being's hand and eye. In a research
spectroscope, a diffraction grating rather than the familiar
prism disperses the radiant energy of light. This is a flat or
spherically curved slab of mirrored glass from which the light is
diffracted by parallel lines -- hence the term grating --
scratched on the reflecting surface. The resolution of a grating
-- the narrowness and faintness of the spectral lines it captures
-- is a function of the number of lines per inch and the
exactitude with which they are spaced in the scratching. Until
the advent of electronic feedback control technology following
the Second World War, the perfection of spectroscopy was owing to
the pleasure that Henry Augustus Rowland [1848-1901] found in
contending with physical reality, after the manner of Galileo,
with bare hands. His tangible legacy is 1000 of the most perfect
diffraction gratings and a million or more precisely established
spectral lines in the catalogue recorded from them. The founding
professor of physics, at age 27 in 1875, at Johns Hopkins
University, Rowland acted on his determination to get the
foundation work of spectroscopy done quickly and precisely. He
settled on a standard of 14,400 two-inch lines of identical width
and depth, to be plowed in the mirrored surface exactly parallel
to one another across each inch and at exactly the same spacing
from one another across a width of five or six inches. To
eliminate the focusing lens and the loss of light it would
entail, he hit on the self-focusing spherical surface. Rowland
once boasted that he never saw a machine that he did not
immediately understand. He recognized that to make the perfect
"ruling engine" to rule the perfect grating required the
perfection of the critical engine part: the lead screw that would
advance a diamond stylus exactly 1.44 x 10^(-4) inches at each
step across a stretch of five or six inches. At 20 threads to the
inch, each full rotation of the screw would advance the diamond
stylus of his ruling engine one-twentieth of an inch; each of the
720 settings in each rotation advanced it 1.44 x 10^(-4) inches.
To grind the perfect thread in the 9-inch lead screw, Rowland
invented a new machine tool. This was an 11-inch-long grinding or
lapping nut with the same threading, which he split lengthwise in
four sections. With the segments reassembled around the screw, he
could adjust the tightness of the nut through the course of
grinding with emery powder and oil and finally the rouge used to
polish telescope mirrors. 'Now grind the screw in the nut,'
Rowland wrote, 'making the nut pass backwards and forwards over
the whole screw... Turn the nut end for end every ten minutes and
continue for two weeks.' In that time the high spots on the
threading of the nut and the screw found one another and wore
themselves away."
-----------
Gerard Piel: _The Age of Science: What Scientists Learned in the
20th Century_
(Basic Books, New York 2001, p.54)
(To be published November 2001)
http://www.amazon.com/exec/obidos/ASIN/0465057551/scienceweek
-------------------
SCIENCE-WEEK http://scienceweek.com 10Aug01
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8. FROM THE SCIENCEWEEK ARCHIVE:
MEDICAL BIOLOGY:
ANALYSIS OF A MASS PSYCHOGENIC ILLNESS IN A HIGH SCHOOL
Epidemic hysteria, also called "mass psychogenic illness" or
"mass sociogenic illness" or "transient situational disturbance"
was first described in the Middle Ages, and it has been reported
in a variety of cultures and settings. In general, in an actual
acute situation, mass psychogenic illness may be difficult to
distinguish from a bioterrorist event, a rapidly spreading
infection, or acute exposure to toxic substances. Epidemics of
psychogenic illness often attract intense media attention and may
have profound public health, social, and economic repercussions.
... ... T.F. Jones et al (8 authors at 4 installations, US)
present a detailed analysis of a particular outbreak of mass
psychogenic illness, the authors (who essentially comprised a
medical and environmental team) making the following points:
1) On November 12, 1998, a teacher at Warren County High
School in McMinnville, Tennessee (US) noticed a "gasoline-like"
smell in her classroom, and soon thereafter she had a headache,
nausea, shortness of breath, and dizziness. The school was
evacuated, and 80 students and 19 staff members went to the
emergency room at the local hospital, where 38 persons were
hospitalized overnight. Five days later, after the school had
reopened, another 71 persons went to the emergency room. An
extensive investigation was performed by government agencies.
2) The authors report they were unable to find a medical or
environmental explanation for the reported illnesses. The persons
who reported symptoms on the first day came from 36 classrooms
scattered throughout the school. The high school population
consisted of 1825 students and 140 staff members. The building
was 4 years old and situated on land that had previously been
farmed. The property was located outside the town of McMinnville,
which has a population of approximately 11,000 persons. The
county has one high school and one hospital. The most frequent
symptoms (both in this group and in the group of people who
reported symptoms 5 days later) were headache, dizziness, nausea,
and drowsiness. Blood and urine specimens showed no evidence of
carbon monoxide, volatile organic compounds, pesticides,
polychlorinated biphenyls, paraquat, or mercury. There was no
evidence of toxic compounds in the environment. A questionnaire
administered 1 month later indicated that the reported symptoms
were significantly associated with female sex, seeing another ill
person, knowing that a classmate was ill, and reporting an
unusual odor at the school.
3) The authors conclude: "This illness, attributed to toxic
exposure, had features of mass psychogenic illness -- notably,
widespread subjective symptoms thought to be associated with
environmental exposure to a toxic substance in the absence of
objective evidence of an environmental cause."
4) In a critical commentary on this report in the same
journal, Simon Wessely (Guy's School of Medicine, UK) states:
"One of the less welcome aspects of the Freudian tradition has
been the widespread acceptance of the existence of symptoms that
are, in that destructive phrase, "all in the mind". Yet
psychogenic symptoms are physiologic experiences that are based
on identifiable physiologic processes that cause pain and
suffering. The children at McMinnville High School experienced
genuine symptoms. That the cause of these symptoms was probably
anxiety about toxic exposure, rather than any exposure itself,
does not detract from their reality. By labeling the episode
psychogenic or hysterical, however, that is precisely what we are
doing."
[Editor's note: Wessely's point is that although mental
health professionals are aware that physiologic symptoms in
psychogenic illness are real symptoms that can cause pain and
suffering, the public (and many professionals outside the field
of mental health) has a tendency to consider symptoms of
psychogenic illness as "imagined" and not worthy of attention.
Such symptoms, however, are indeed real, as real as the
psychogenic blushing of an individual's face (an opening of blood
capillary beds in the face), when that individual perceives (or
imagines) a social embarrassment, or as real as the increase in
heart rate that can be produced by a real or imagined physical
threat, or even by merely watching an action film. All the
symptoms in the reported high school case can be shown to be
produced by specific activations of the autonomic nervous system,
activations affecting the vascular system, heart rate,
respiration, etc., and these activations can follow specific
activations of the central nervous system by psychological
anxiety states. The biologic paradigm is simply stated: the
central nervous system receives (perceives) psychological input,
and, in addition to the effect of that input on other central
nervous system activity, that input, if capable of provoking
certain emotional states, is complexed, filtered, and converted
to activation of the autonomic nervous system, which in turn
activates physiologic output by controlling various involuntary
muscle groups and glandular secretions. In summary, the symptoms
of the high school population should be considered as most
definitely real; it was the source of the anxiety that was
evidently imagined.]
-----------
T.F. Jones et al: Mass psychogenic illness attributed to toxic
exposure at a high school.
(NEJM 2000 342:96)
QY: Timothy F. Jones, Tennessee Dept. of Health, Nashville TN
37247 US.
-----------
Simon Wessely: Responding to mass psychogenic illness.
(NEJM 2000 342:129)
QY: Simon Wessely, Guy's School of Medicine, London SE5 8AF UK
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 28Apr00
For more information: http://scienceweek.com/swfr.htm
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9. SOURCES:
AGP: Archives of General Psychiatry
APL: Applied Physics Letters
AS: American Scientist
CEN: Chemical & Engineering News
GD: Genes & Development
GR: Genome Research
ICAR: Icarus
JAAD: Journal of the American Academy of Dermatology
JACS Journal of the American Chemical Society
JAMA: Journal of the American Medical Association
JCE: Journal of Chemical Education
NAT: Nature
NEJM: New England Journal of Medicine
NYT: New York Times
PNAS: Proceedings of the National Academy of Sciences
PRL: Physical Review Letters
PT: Physics Today
SA: Scientific American
SCI: Science
SK: Skeptic
SW: ScienceWeek
TB: The Biochemist
TS: The Scientist
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