ScienceWeek

SCIENCE-WEEK

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A journal devoted to the improvement of communication
between the scientific disciplines, and between scientists,
science educators, and science policy makers.

June 4, 1999 -- Vol. 3 Number 23

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We have entered the cell, the mansion of our birth,
and have started the inventory of our acquired wealth.
-- Albert Claude (1899-1983)

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Contents of This Issue:

1. Scientific Fraud: An Important Case in Plant Biology
2. On the Origin of the Earth and the Moon
3. Measurement of the Rupture Force of Single Covalent Bonds
4. On the Gestural Origins of Human Language
5. Development of Neural Pathways in Children and Adults
6. Bacteria and Human Heart Disease: Effects of Antibiotics

In Focus: On the Spectra of the Stars

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1. SCIENTIFIC FRAUD: AN IMPORTANT CASE IN PLANT BIOLOGY
Here is an interesting case of scientific fraud, albeit with the
appearance of an opera surrounding a farce:
     1) A laboratory invents a new important technology which is
validated by other laboratories and becomes widely used.
     2) The inventing laboratory then proceeds to apply the
technology to a particular problem. In the course of the
application, one of the laboratory researchers apparently
fabricates data to achieve important results, and a number of
"co-authors" in the laboratory join with the fabricating
researcher to publish the results in a series of papers in
various leading international journals.
     3) Ultimately, the results cannot be replicated by others,
the results are considered fabrications, and the group leader of
the laboratory and the fabricating researcher are forced to
resign. The co-author fabricating researcher is identified as a
"technician" (see the related background report below).
     4) A research team led by the head of the department that
housed the laboratory takes on the task of determining which
published papers are suspect, and reports that 10 papers in
various leading journals (Science, Nature, EMBO Journal, Proc.
Natl. Acad. Sci. US, etc.), published between 1992 and 1998,
probably contain serious fabrications.
     5) The former group leader and the involved laboratory
researcher-technician both refuse to comment on the case.
     6) Two of the 10 papers have already been retracted by other
co-authors, but there are apparently no plans by any co-authors
to retract the other papers.
     7) The editors of the various leading journals say they have
no plans to retract the remaining published papers themselves,
but will wait for retractions by the authors. The journal editors
have evidently been criticized because at least some of the
fabrications might have been detected by proper review of the
papers when they were originally submitted.
     The laboratory in question is part of the Max Planck
Institute for Plant Breeding Research in Cologne, DE. The group
leader of the laboratory was Richard Walden, who resigned in
1998, and who is apparently now working in a laboratory in the
UK. The implicated "technician" is Inge Czaja. The research
involved a new technique to study the actions of plant genes
(activation T-DNA tagging), a validated technique now widely used
in plant biology. The investigating team consisted of researchers
at the Cologne institute and colleagues from other European
laboratories, the team led by Jeff Schell, head of the department
containing the fabricating laboratory. The investigation report
concerning the 10 suspected fraudulent papers was recently
published in the March 1999 issue of _Plant Journal_. Alan Jones
(University of North Carolina, Chapel Hill US), a researcher in
the field, is quoted as saying: "I can no longer believe any
parts of the data in any parts of the papers... When the papers
came out, I was extremely enthusiastic." Jones states that the
discovery of the fabrications will have a "negative effect on the
field" because major conclusions were drawn from the papers.
-----------
Michael Balter: Data in key papers cannot be reproduced.
(Science 26 Mar 99 283:1987)
QY: Michael Balter [science_editors@aaas.org]
-------------------
Summary by SCIENCE-WEEK [http://scienceweek.com] 4Jun99
-------------------
Related Background:
RUMBLINGS OF A NEW SCIENTIFIC FRAUD SCANDAL IN GERMANY
Another major scientific fraud scandal appears to have surfaced
in Germany, coming into view while the last scandal is still
fresh. This time the problem is fraudulent work at the Max Planck
Institute for Plant Breeding in Cologne. A laboratory head and
his technician have already resigned, the technician, Inge Czaja,
admitting fabrication of data in at least one scientific paper
while she worked in the laboratory of Richard Walden. A
commission is now investigating the possibility of systematic
manipulation of important experimental results for 6 years by
this team. Experiments in at least half a dozen papers have
apparently proved to be non-reproducible using specially
developed tests. The research involves the identification of
certain enzymes in the signaling system of the hormone auxin, a
promoter of plant cell growth. Walden claims no direct
involvement in the fraud, but admits responsibility, as group
leader, for the quality of work done by his group. Apparently,
questions are also being raised concerning the responsibility of
Jeff Schell, one of the institutes four directors and head of the
department of plant genetics, where the work was carried out. The
fraud was first revealed in March 1998.
(Nature 28 May 98 393:293) (Science-Week 12 Jun 98)


2. ON THE ORIGIN OF THE EARTH AND THE MOON
Two of the central questions in planetary and Earth science
concern the origin of the Earth and Moon. How did these two
bodies form and what forces defined their basic physical
structures? ... ... A.N. Halliday and M.J. Drake (2
installations, CH US) present a short review of current research
in this area, the authors making the following points:
     1) Advances in this field have come mainly with progress in
simulating the dynamics of planetary accretion, in measuring
isotopes that act as chronometers for early Solar System
processes, in analysis of noble gas isotopes that yield clues
about the early atmosphere, and in melting experiments at
previously unattainable pressures and temperatures. Although a
general picture may be emerging, many issues remain hotly
debated.
     2) Planet formation is believed to begin with sticking and
frictional coagulation of dust particles in a gaseous nebula that
persists in the *circumstellar disk. The particles grow in size
until there is substantial gravitational attraction between
kilometer-sized bodies, and these coalesce further. Major
collisions between small proto-planets eventually result in
objects the size of Earth.
     3) The energy of late-stage planet-building impacts would be
colossal, sufficient to melt the entire planet. *Magma oceans
would be formed, and some volatile elements would escape into
space. The most widely accepted theory for the origin of the Moon
is that it coalesced from a ring of debris produced by such a
late-stage collision between two Earth-forming proto-planets.
This "Giant Impact Theory", established over a decade ago,
explains the rotational speed of the Earth-Moon system, a
critical feature that must be reproduced by any satisfactory
model. But in spite of a growing consensus, some researchers are
still opposed to the Giant Impact Theory on both dynamical and
geochemical grounds.
     4) All isotopic data are consistent with Earth being fully
formed within 50 to 100 million years after the start of the
Solar System. The isotopic record from Moon rocks is consistent
with the formation of the Moon at about the same time.
     5) The authors conclude: "We have recently come a long way
in obtaining hard constraints on the origin of Earth and the
Moon. The issues have changed from discussion of whether or not
there was a giant Moon-forming impact to debate about the
accretion rates of the Earth and the chemical, isotopic, and
physical effects of such catastrophic accretionary scenarios."
... ... In a contiguous short review of the same research area,
Frank A. Podosek (Washington University St. Louis, US) makes the
following points:
     1) The age of the Solar System as a whole is easier to
determine than the age of Earth. The age of the Solar System is
reliably inferred from the age of *refractory element-rich
inclusions in meteorites to be approximately 4.57 billion years,
thus providing an upper limit to the age of Earth. These
inclusions are the oldest known objects in the Solar System, and
their content indicates that the Solar System did not exist for
more than approximately 1 million years before the inclusions
formed.
     2) In contrast to these ancient extraterrestrial objects,
there are no known terrestrial rocks or minerals whose formation
essentially coincides with the formation of Earth, and therefore
the age of Earth must be inferred indirectly. Several independent
approaches indicate that Earth formed approximately 100 million
years later than the Solar System as a whole.
     3) All the various isotopic chronometers are intrinsically
capable of considerably higher precision, but this precision
cannot yet be realized. It is not even clear whether the
chronometers are consistent or in conflict with each other. All
methods rely on models of varying complexity involving
assumptions difficult to verify and parameters difficult to
measure.
     4) The author concludes: "For testing the giant impact
scenario in particular, it would be useful to have a quantitative
theory for whether a preexisting atmosphere is lost in the
impact, whether preexisting planetary structures (*core, mantle,
and crust) are re-equilibrated after such an impact, and how much
of the Moon comes from the impactor and how much comes from the
target."
-----------
A.N. Halliday and M.J. Drake: Colliding theories.
(Science 19 Mar 99 283:1861)
QY: A.N. Halliday [halliday@erdw.ethz.ch]
-----------
Frank A. Podosek: A couple of uncertain age.
(Science 19 Mar 99 283:1863)
QY: Frank A. Podosek [fap@levee.wustl.edu]
-----------
Text Notes:
... ... *circumstellar disk: One of the important discoveries of
the 1980s was the existence of circumstellar disks of dust around
some stars, the disks apparently replenished by unseen parent
bodies such as comets and asteroids.
... ... *Magma: In general, any mass of molten rock.
... ... *refractory: Refractory materials are materials resistant
to decomposition by heat, pressure, or chemical attack. The term
is most commonly applied to heat resistance.
... ... *core, mantle, and crust: Seismic studies indicate the
interior of the Earth consists of three parts: a metallic core, a
dense rocky mantle, and a thin low-density crust. The central
part of the core is solid, but the outer part of the core is
evidently liquid.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 4Jun99
-------------------
Related Background:
AGE AND ORIGIN OF EARTH'S MOON
The most widely accepted theory for the origin of the Earth's
moon is that during the late stages of the Earth's accretion an
impact with another planet at least the size of Mars occurred,
and the impact generated both the hot debris that formed the moon
and the angular momentum of the Earth-moon system. In geology,
the mantle of a planet or moon is the layer that lies between the
crust and the core. 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, and "chondritic" is the term used to describe a
rock composition similar to that of chondrites, which implies an
age of 4.2 to 4.5 billion years. The term "radiogenic", on the
other hand, is used to describe a rock composition apparently
resulting from varying isotope decays, and the oldest radiogenic
compositions on Earth have been dated at 3.6 to 3.8 billion
years. A hafnium-tungsten chronometer is not an actual instrument
but a method of radiometric age determination using the isotope
ratios of the elements hafnium and tungsten. Hafnium is
lithophilic (silicate-loving), which means it tends to associate
with chondritic materials, while tungsten is siderophilic (metal-
loving), which means it tends to associate with metal cores, and
using these differing affinities of these elements, one can
attempt a construction of the age and origin of the moon by
analysis of moon rock samples and comparisons with Earth rocks.
Lee et al (4 authors at 2 installations, US) report a study of
the age and origin of the moon with the hafnium-tungsten
chronometric method. The tungsten isotopic compositions of 21
lunar samples were found to range from chondritic to slightly
radiogenic. The authors suggest this heterogeneity is probably
the result of late radioactive decay within the moon itself, and
that the moon formed 4.52 to 4.50 billion years ago and its
mantle has since remained poorly mixed.
QY: Der-Chuen Lee [dclee@umich.edu]
(Science 7 Nov 97) (Science-Week 28 Nov 97)
-------------------
Related Background:
THE ORIGIN OF EARTH'S MOON
The large impact hypothesis of the origin of the Earth's moon is
the current consensus view. The essential idea is that the moon
formed from debris ejected into a disk around Earth by the impact
of a large body. A version of this is that Earth and its moon
were created more or less simultaneously by the collision of two
large planetesimals, the resultant large body becoming Earth, and
the ejected debris formed the moon. What is accepted by nearly
everyone is that an accretion disk of debris was the first stage
of the moon's formation. Shigeru Ida et al (Tokyo Institute of
Technology, JP; University of Colorado Boulder, US) have
evidently now provided the most detailed simulation calculations
of lunar growth in an impact-generated accretion disk. Using
direct N-body simulations, they show that a single dominant moon
can grow from such a disk within a year, but to satisfy the
present angular momentum and mass constraints on the analysis,
the impacting body must have been at least twice as massive as
Mars, and had to provide the resultant system with a few times
more angular momentum than it now possesses. There is presently
no explanation for the subsequent loss of angular momentum, and
the required massive size of the impacting object is also
puzzling. Although this is apparently the best set of simulation
calculations to date, the authors emphasize that further
simulation modeling is needed [*Note #1].
QY: S. Ida [ida@geo.titech.ac.jp]
(Nature 25 Sep) (Science-Week 10 Oct 97)
-----------
Text Notes:
... ... *Note #1: Accretion is considered an important factor in
the evolution of stars, planets, and comets. The essential idea
is the coalescence of small particles in space as a result of
collisions, and the gradual formation of larger bodies from
smaller ones as a result of gravitational attraction. An
accretion disk is a disk of gas or particles in orbit around an
object, the disk formed by inflowing matter. A simulation of the
sort mentioned in the report involves computational solutions of
the dynamical equations for the history of a chosen mass of
particulate matter initially ejected from a larger body. By
solving the equations for the mathematical model, one can follow
the evolution of the accretion disk and the agglomeration that
forms the final orbiting satellite. The study mentioned here was
first presented at a meeting of the American Astronomical Society
in July, and here is part of the related SCIENCE-WEEK (1 Aug 97)
report: Until the 1980s, there were three extant theories, with
no data available to support or refute any of them. The Fission
Hypothesis proposed that the moon broke away from a rapidly
spinning proto-Earth after the proto-Earth's differentiation, the
moon forming from iron-poor crust. But the moon rocks in hand
have been found to differ chemically from those of Earth. Also,
if the proto-Earth had been spinning fast enough to break up, the
present Earth-moon system should contain a great deal more
angular momentum than is observed. The Fission Hypothesis
therefore had to be abandoned. The Condensation Hypothesis was
based on the idea that the Earth and the moon condensed
simultaneously from the same cloud of material in the solar
nebula. This hypothesis did not survive because analysis of moon
rocks has shown the Earth and the moon have greatly different
densities and compositions. The Capture Hypothesis proposed that
the moon was formed elsewhere in the solar system and later
"captured" by Earth. This hypothesis was always the least popular
because it required too many coincidental events. Thus, after the
mid-1980s, there was no satisfactory theory of the moon's origin.
During the past decade, a new idea gradually developed, the
Large-Impact Hypothesis, the idea of which is that the moon
formed from debris ejected into a disk around the Earth after a
major collision of the Earth with another large body about 4.5
billion years ago, the other body a planet perhaps as large as
Mars. The Large-Impact Hypothesis is at present the consensus
theory in planetary science. 


3. MEASUREMENT OF THE RUPTURE FORCE OF SINGLE COVALENT BONDS
From an elementary standpoint, what we call a "chemical bond" is
something that ties two or more atoms together to form a
molecular entity with sufficient stability for us to measure or
describe some of the entity's properties. The idea of the
chemical bond, including the notion of valence and the way we
draw the connections between atoms in a molecule, is usually
ascribed to Friedrich Kekule (1829-1896), but in fact it was
Edward Frankland (1825-1899) who first suggested the idea of
valence, and Archibald Couper (1831-1892) who first suggested the
depiction of the bond between 2 atoms by a dash. The use of
Couper's dashes to depict bonds was made popular by a chemist
well-known at the time for various discoveries in synthetic
chemistry, Richard Erlenmeyer (1825-1909). So today we have the
irony that Erlenmeyer is known primarily for the name of a glass
flask that he designed, Cooper and Frankland are hardly known at
all, and Kekule is often described to students as having
concocted these beginnings of structural chemistry in a dream.
Kekule may have indeed dreamt of the resonating benzene ring, but
his dream had the intimate help of his generation of chemists.
Putting aside the personal history of the concept of the chemical
bond, during its relatively short 150-year-old existence, this
concept has without any doubt been one of the most important
ideas in modern science. During this century, the focus has been
to understand the chemical bond in terms of quantum physics, but
certain classical aspects remain of great practical interest,
particularly the question of the relative strengths of the bonds
between different types of atoms. There are various ways to
approach this question of "bond strength", including actual
determinations of the mechanical force necessary to rupture
bonds. The mechanical stabilities of covalent bonds, bonds that
involve sharing of electrons, have in the past been investigated 
indirectly in ensemble measurements or by flow-induced chain
fracture in liquids. The recent development of nanoscale
manipulation techniques has made it possible to directly address
single atoms or molecules and probe their mechanical properties.
... ... M. Grandbois et al (5 authors at 3 installations, DE US)
now report a study of the rupture force of single covalent bonds
under an external load measured with an *atomic force microscope.
Single polysaccharide molecules were covalently anchored between
a surface and an atomic force microscope tip and then stretched
until the molecule became detached. The authors report that by
using different surface chemistries for the attachment, it was
found that the silicon-carbon bond ruptured at 2.0 +- 0.3
nanonewtons, whereas the sulfur-gold anchor ruptured at 1.4 +-
0.3 nanonewtons, at force-loading rates of 10 nanonewtons per
second. The authors report these results agree with bond rupture
probability calculations based on *density functional theory. The
authors conclude: "Although chemical compounds play a dominant
role in material sciences, the forces that chemical bonds can
withstand could previously not be directly measured in
experiments. The experiments reported here demonstrate that the
individual chemical bonds can be probed in mechanical
experiments. An important feature of such experiments is the
mechanical activation of chemical bonds (here in the simplest
form as bond rupture), which can now be studied on an individual
basis."
-----------
M. Grandbois: How strong is a chemical bond?
(Science 12 Mar 99 283:1727)
QY: Hermann E. Gaug, Lehrstuhl fur Angewandte Physik, Ludwig-
Maximillians-Universitat, Amalienstrasse 54, D-80799 Munich, DE.
-----------
Text Notes:
... ... *atomic force microscope: In general, in atomic force
microscopy, a tip is fixed to a cantilever whose position is
monitored while the tip scans a surface. The force between the
tip and the surface determines the position of the cantilever.
When recorded in atomic resolution, the image represents a map of
atomic forces at the surface. In the present study, the active
polymer molecule was first coupled to the substrate surface. The
tip was then slowly brought into contact with the surface,
allowing the polymer to bind to the tip (which occurred in
approximately 30 percent of the cases). The tip and the substrate
where then gradually separated while the force was recorded. The
polymer was repeatedly stretched and relaxed through one or more
conformational transitions. After analysis confirmed that a
single molecule was bound, the force was gradually increased
until the molecular bridge ruptured.
... ... *density functional theory: For atomic force calculations
on solids, 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.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 4Jun99


4. ON THE GESTURAL ORIGINS OF HUMAN LANGUAGE
A view currently held by many anthropologists and linguistics
researchers is that the remarkable flexibility of human language
is achieved at least in part through the human invention of
grammar, a recursive set of rules that allows the generation of
sentences of any desired complexity. The linguist Noam Chomsky
has attributed this to a unique human endowment termed "universal
grammar", with Chomsky suggesting that all human languages are
variants of this fundamental endowment.
... ... Michael C. Corballis (University of Auckland, NZ)
presents a review of current ideas concerning the origins of
human language, with emphasis on a scenario involving gestural
antecedents. The author makes the following points:
     1) There is little doubt that the great apes (orang-utan,
gorilla, chimpanzee) (and perhaps other species such as dolphins)
can use symbols to represent actions and objects in the real
world, but these animals lack nearly all the other ingredients of
true language.
     2) Since the common ancestor of human beings and chimpanzees
lived approximately 5 million years ago, it is a reasonable
inference that grammatical language must have evolved in the
hominid line (i.e., the line of human primates) at some point
following the split from the line that led to the modern
chimpanzee. There has been much disagreement as to when this
might have happened.
     3) One major view holds that it is impossible to conceive of
grammar as having been formed incrementally; grammar therefore
must have evolved as a single catastrophic event, probably late
in hominid evolution. But many researchers hold a contrary view,
that language evolved gradually, shaped by natural selection, and
that the cognitive prerequisites of language are already present
in the great apes and antedated the split of our hominid
ancestors from the chimpanzee line, probably by several million
years.
     4) The author suggests that at least a partial
reconciliation of these alternative perspectives may be that
language emerged not from vocalization, but from manual gestures,
and switched to a vocal mode relatively recently in hominid
evolution, perhaps with the emergence of Homo sapiens. This is an
old idea, apparently first suggested by Condillac in the 17th
century, but argument in its favor has continued to grow.
     5) The author points out that there are countless different
sign languages invented by deaf people all over the world, and
there is little doubt that these are genuine languages with fully
developed grammars. The spontaneous emergence of sign languages
among deaf communities everywhere confirms that gestural
communication is as natural to the human condition as is spoken
language. Indeed, children exposed from an early age only to sign
language go through the same basic stages of acquisition as
children learning to speak, including a stage when they "babble"
silently in sign.
     6) The authors proposes the following speculative scenario
concerning the historical development of human language:
... ... a) 6 or 7 million years ago: Simple gestures first
anticipated more complex forms of communication, shortly after
the human line diverged from the great apes. At this stage
vocalizations served only as emotional cries and alarm calls.
... ... b) Approximately 5 million years ago: With the advent of
bipedalism, a more sophisticated form of gesturing involving hand
signals may have evolved among the early hominids now labelled as
"Australopithecus".
... ... c) Approximately 2 million years ago: In association with
the increasing brain size of the genus Homo, hand gestures became
fully syntactic (i.e., with syntax; with ordered arrangements),
but vocalizations also became prominent.
... ... d) 100,000 years ago: Homo sapiens switched to speech as
its primary means of communication, with gestures now playing a
secondary role.
... ... e) Modern times: The development of telecommunication now
permits the routine use of spoken language in the complete
absence of hand gestures, but even so, many people find
themselves gesturing when they speak on the telephone.
     7) Concerning the question of what it was that enabled our
species to prevail over other large-brained hominids, the author
concludes: "Perhaps the most plausible answer is that they
prevailed because of superior technology. But that technology
might have resulted, not from an increase in brain size or
intelligence, but from a switch from manual to vocal language
that allowed them to use their hands for the manufacture of tools
and weapons and their voices for instruction."
-----------
Michael C. Corballis: The gestural origins of language.
(American Scientist Mar-Apr 1999 87:138
QY: Michael C. Corballis [m.corballis@auckland.ac.nz]
-------------------
Summary by SCIENCE-WEEK [http://scienceweek.com] 4Jun99
-------------------
Related Background:
HYPOGLOSSAL CANAL SIZE AND HOMINID SPEECH
The mammalian *hypoglossal canal transmits the *nerve that
supplies the *motor innervation to the tongue. Hypoglossal canal
size has been used to date the origin of human-like speech
capabilities to at least 400,000 years ago, and to assign modern
human vocal abilities to *Neandertals. These conclusions are
based on the hypothesis that the size of the hypoglossal canal is
indicative of speech capabilities.
... ... D. DeGusta et al (3 authors at 2 installations, US) now
present the results of a study to test the hypothesis that
hypoglossal canal size is indicative of speech. The authors
report they measured the following: a) the hypoglossal canals of
75 nonhuman primates and 104 modern humans; b) the hypoglossal
canal in specimens of the early *hominid *taxa *Australopithecus
afarensis and *Australopithecus boisei; c) both the nerve and
canal diameter and estimated nerve axon number in a sample of
human cadavers. The authors report the following results: a) Many
nonhuman primate specimens have hypoglossal canals that are
absolutely and relatively within the size range of modern humans.
b) The hypoglossal canals of Australopithecus afarensis,
Australopithecus boisei, and *Australopithecus africanus are also
within the modern human size range. c) The size of the
hypoglossal nerve and the number of axons it contains do not
appear to be significantly correlated with the size of the
hypoglossal canal. The authors conclude: "The size of the
hypoglossal canal is not a reliable indicator of speech.
Therefore the timing of the origin of human language and the
speech capabilities of Neandertals remain open questions." [*Note
#1].
-----------
Editor's note: The authors present this report essentially as a
refutation of a paper by R.F. Kay et al, a summary of which
appears in the background material below. Also, for more
generally related material, see the SW Focus Report
"Anthropology: Human Evolution" at URL
[http://scienceweek.com/swfr017.htm].
-----------
D. DeGusta et al: Hypoglossal canal size and hominid speech.
(Proc. Natl. Acad. Sci. US 16 Feb 99 96:1800)
QY: David DeGusta [degusta@uclink.berkeley.edu]
-----------
Text Notes:
... ... *hypoglossal canal: This canal, at the level of the
brainstem, is a passageway through bone for the XII cranial
nerve, the nerve bundle that innervates the tongue.
... ... *nerve: In general, the term "nerve" refers to a bundle
of nerve axons (nerve fibers; neuron axons), the nerve usually
visible to the naked eye. Nerves can contain large number of
individual axons: the optic nerve in humans, for example,
contains approximately 1 million nerve fibers. The hypoglossal
nerve, the cranial nerve of relevance in this report, contains
mostly nerve axons whose cell bodies are in the hypoglossal
nucleus in the brainstem (efferent fibers carrying information to
activate the muscles of the tongue), and perhaps some axons
carrying information from sensory receptors in the tongue to the
central nervous system (afferent fibers).
... ... *motor innervation: This refers to the anatomical
connections of nerve fibers to muscle cells, the electrical
activity of the nerve axons resulting in the activation of the
muscle cells.
... ... *Neandertals: (Neanderthals) About 10 kilometers east of
Dusseldorf in Germany, in the valley of the Dussel, there is a
little town called Neander. One hundred and forty-one years ago,
in the summer of 1856, some workmen broke into a cave to get at
the limestone inside and discovered a set of ancient bones. Most
of the bones were smashed to bits by the workmen, but some of the
bones, including part of the skull, survived, and the skeleton
was soon recognized by anthropologists as belonging to an ancient
race of men who came to be known as the Neanderthals. A
Neanderthal fossil had actually been discovered some years
earlier in Gibraltar, but not recognized as such. Neanderthal-
like fossils have also been found in France, Spain, Italy,
Yugoslavia, Iraq, China, Java, and Israel. For more than a
century, one of the central questions in paleoanthropology has
been whether modern man evolved from this race.
... ... *hominid: The term "hominid" refers to any primate in the
human family (Hominidae) of which Homo sapiens (modern man) is
the only living specimen.
... ... *taxa: In general, a grouping defined in terms of shared
similar characters.
... ... *Australopithecus afarensis: The first record of human
footprints, of hominids walking upright, was discovered at
Laetoli in East Africa, and has been dated at 3.6 million years
ago. This ancestor, Australopithecus afarensis, probably weighed
25 to 50 kilograms (60 to 120 lbs.) as an adult.
... ... *Australopithecus boisei: Discovered by Mary Leakey in
the Olduvai Gorge in Tanzania, this fossil has been dated at 1.75
million years ago.
... ... *Australopithecus africanus: Apparently derived from
Australopithecus afarensis were several species, including
Australopithecus africanus, a species which is believed to have
appeared approximately 3 million years ago.
... ... *Note #1: Although the focus in this report is on the
role of the neural innervation of the tongue in human speech, it
must be emphasized that the organization of information and motor
output necessary for speech apparently occurs concomitantly in
several localized region of the cerebral cortex, and the
evolution of these regions of the brain most likely played a
significant role in the appearance of speech in humans.
Essentially, the hypoglossal nerve merely transmits information
originating in the brain, and both the origin and transmission of
this information must be considered in any analysis of the
evolution of human speech. Unfortunately, the brain is soft
tissue and is not preserved in fossils; what we have is bone, and
the data provided by bone and relevant archeological entities.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 16Apr99
-------------------
Related Background:
ORIGIN OF HUMAN VOCAL BEHAVIOR: AN ANATOMICAL CONSIDERATION
It can be argued that language is the most important behavioral
attribute that distinguishes humans from other animals, and one
of the important problems in anthropology and human evolution is
to demarcate as narrowly as possible the time frame during which
language in humans first appeared. Such demarcations have been
based on either apparent anatomical correlates (e.g., bone and
soft tissue analysis) or apparent archeological correlates (e.g.,
analysis of apparent symbolic behavior), with no firm specific
consensus among specialists. One of the important anatomical
features related to language is the nerve supply controlling the
muscles of the tongue. The mammalian hypoglossal canal is a bony
canal that contains the trunk of nerve fibers that constitute
this nerve supply. This canal is absolutely and relatively larger
in modern humans than it is in the African apes. ... ... Kay et
al (3 authors at Duke University, US) report a study of the
cross-sectional areas of hypoglossal canals in adult skulls of
contemporary humans, African apes, and several key fossil
hominids. They propose that hypoglossal canal size in fossil
hominids may provide an indication of the motor coordination of
the tongue and reflect the evolution of speech and language. What
they report is that the hypoglossal canals of gracile
Australopithecus, and possibly Homo habilis, fall within the
range of extant African apes, and are significantly smaller than
those of modern Homo. The canals of Neanderthals and an early
"modern" Homo sapiens (Skhul 5), as well as of African and
European middle Pleistocene Homo (Kabwe and Swanscombe), fall
within the range of contemporary Homo and are significantly
larger than those of Pan troglodytes (a chimpanzee species). In
summary, the authors suggest these anatomical findings indicate
the vocal capabilities of Neanderthals were the same as those of
humans today. The authors further suggest that the vocal
abilities of Australopithecus were not advanced significantly
over those of chimpanzees, whereas those of Homo may have been
essentially modern by at least 400,000 years ago, which is
consistent with the evidence for accelerated encephalization
rates in middle Pleistocene Homo. The authors conclude: "Thus,
human vocal abilities may have appeared much earlier in time than
the first archeological evidence for symbolic behavior."
QY: Richard F. Kay [Rich.Kay@baa.mc.duke.edu]
(Proc. Natl. Acad. Sci. US 28 Apr 98 95:5417)
(Science-Week 19 Jun 98)


5. DEVELOPMENT OF NEURAL PATHWAYS IN CHILDREN AND ADULTS
The human brain is not a finished organ at birth -- in fact,
another 10 or 12 years are needed before even a general
development is completed. Structural maturation of individual
brain regions and their connecting pathways is required for the
successful development of cognitive, motor, and sensory
functions. This maturation eventually provides for a smooth flow
of neural impulses throughout the brain, which allows for
information to be integrated across the many spatially segregated
brain regions involved in these functions. The speed of neural
transmission is an important factor, and this depends not only on
the junctions between nerve cells (synapses), but also on the
structural properties of the connecting fibers (axons). Critical
axon structural properties include their diameters and the
thickness of the special insulation (myelin) around many fibers
[*Note #1]. Large groups of myelinated axons, which connect
various regions in the brain, appear visibly as "white matter".
Axons of the major pathways in the human brain, such as those of
the corpus callosum (which connects the two halves of the brain)
or the corticospinal tract (which connects the brain to the
spinal cord and the rest of the body), continue to develop
throughout childhood and adolescence. Postmortem studies suggest
that axon diameters and myelin sheaths undergo conspicuous growth
during the first 2 years of life, but may not be fully mature
before adolescence or even late adulthood. The scarcity of human
brain specimens for postmortem analysis has made it difficult to
draw definite conclusions about the timetable of myelinization
during childhood and adolescence. ... ... T. Paus et al (8
authors at 2 installations, CA US) now report a computational
analysis of structural *magnetic resonance images obtained in 111
living children and adolescents. The authors report the analysis
reveals age-related increases in white-matter density in fiber
tracts constituting apparent corticospinal and *frontotemporal
pathways. The maturation of the corticospinal tract was
bilateral, but that of the frontotemporal pathway was found
predominantly in the left (speech-dominant) hemisphere. The
authors suggest these findings provide evidence for a gradual
maturation, during late childhood and adolescence, of fiber
pathways presumably supporting motor and speech functions. The
authors also suggest their finding may provide guidance for
further investigations of neurodevelopmental disorders such as
schizophrenia: "the abnormal rate of myelinization during
childhood or adolescence may very well underlie the emergence of
psychotic symptomatology." Finally, the authors suggest that the
demonstrated possibility of detecting subtle structural
variations in white matter in the living human brain opens up new
avenues of research on normal and abnormal cognitive development
and in the evaluation of the long-term effects of various
treatment strategies.
-----------
T. Paus et al: Structural maturation of neural pathways in
children and adolescents: In vivo study.
(Science 19 Mar 99 283:1908)
QY: Tomas Paus [tomas@bic.mni.mcgill.ca]
-----------
Text Notes:
... ... *Note #1: Our understanding of the propagation of nerve
impulses represents an interesting convergence of physics and
biology. The nerve impulse is a rapid propagating
wave (approximately 1 millisecond in duration) of depolarization
followed by repolarization. In the language of physics, the
neuron axon behaves as an electrical transmission line with a
transverse time-variant and voltage-dependent negative
conductance element in parallel with a high capacitance. In fact,
the equations describing the propagation of neuron action
potentials derive from the classical equations for wave
propagation along electrical transmission lines developed by
Maxwell and Kelvin. As expected from these equations, the cross-
sectional diameter of an axon is an important determinant of
impulse propagation velocity: the larger the diameter, the
greater the velocity of propagation. The myelin sheath that
surrounds certain types of axons is a periodically interrupted
electrical insulation, and on physical grounds it can be
demonstrated that the effect of this type of insulation,
considering the known electrical properties of the axon, is a
substantial increase in pulse propagation velocity over that of a
bare axon of the same diameter. Myelinization is thus a major
aspect of the workings of neural circuits.
... ... *magnetic resonance images: Magnetic resonance imaging
(MRI) is essentially a technique for examining morphology (as
opposed to _functional_ magnetic resonance imaging, which is a
technique for examining anatomical correlates of function). In
general, MRI involves magnetic coils producing a static magnetic
field parallel to the long axis of the patient or subject,
combined with inner concentric magnetic coils producing a static
magnetic field perpendicular to the long axis. A radio-frequency
coil specifically designed for the head perturbs the static
fields to generate a magnetic resonance image. The interaction
physics in this technique is that between the magnetic fields and
atomic nuclei in brain tissue. "Sliced" views can be obtained
from any angle, and the resolution is quite high and on the order
of millimeters for magnetic field strengths of 1.5 tesla.
... ... *frontotemporal: In this context, this term refers to
connections between the frontal lobes and temporal lobes of the
brain.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 4Jun99


6. BACTERIA AND HUMAN HEART DISEASE: EFFECTS OF ANTIBIOTICS
Throughout its individual existence as a biological entity, the
human body plays host to a large and variegated ensemble of
microorganisms, all of which are potentially pathogenic under
particular circumstances or if immune system control falters.
During the past decade, there has been increasing interest in the
medical community in the possible relation between microbial
infection and heart disease. Bacterial endocarditis, an infection
of the inner lining of the heart, is a relatively uncommon but
well-known clinical entity, a disease whose incidence in the US
has apparently not changed in 30 years. But what role, if any,
does bacterial infection play in coronary artery disease?
*Atherosclerotic cardiovascular disease, the most common variant
of coronary artery disease, is now the leading cause of death in
the US and is projected to be the leading cause of disability in
the world by 2020. The possibility that microbial infection might
be one of the risk factors for atherosclerotic cardiovascular
disease was hypothesized more than 100 years ago, and there is
now renewed interest in that hypothesis. From recent
observational studies and randomized clinical trials, there is
apparently increasing evidence that certain bacterial infections
may play a role in the etiology of coronary heart disease and
subsequent acute *myocardial infarction. In particular, the
bacterial species *Chlamydia pneumoniae, *Helicobacter pylori,
and bacterial infections associated with *periodontal diseases
have been related to an increased risk of developing acute
myocardial infarction as well as *thrombotic stroke. Such
infections, particularly with C. pneumoniae, have a high
prevalence, and are often without symptoms and undiagnosed and
untreated. If the causal relationships between bacterial
infections and acute myocardial infarction indeed exists, the
risk of such untreated chronic infections in the etiology of
ischemic heart disease might be substantial.
... ... C.R. Meier et al now report the results of a study to
explore the effects of previous use of various antibiotics on the
risk of developing subsequent first-time acute myocardial
infarction. The authors used a UK database comprising 350 general
medical practices, the analysis involving 3315 case patients 75
years or younger with a diagnosis of first-time acute myocardial
infarction between 1992 and 1997, and 13,139 matching controls.
The authors report that first-time acute myocardial infarction
cases were less likely to have used *tetracycline or *quinolone
antibiotics, with no effect found for previous use of *macrolides
(primarily *erythromycin), *sulfonamides, *penicillins, or
*cephalosporins. The authors suggest their findings provide
further (albeit indirect) evidence for an association between
bacterial infections with organisms susceptible to tetracycline
or quinolone antibiotics and the risk of acute myocardial
infarction. The authors conclude: "These potentially important
findings on the role of chronic infections in the etiology of
acute myocardial infarction need further confirmation,
particularly from large-scale *prospective randomized trials."
-----------
C.R. Meier et al: Antibiotics and risk of subsequent first-time
acute myocardial infarction.
(J. Amer. Med. Assoc. 3 Feb 99 281:427)
QY: Christoph R. Meier [chmeier@bu.edu]
-----------
Text Notes:
... ... *Atherosclerotic cardiovascular disease: The term
"arteriosclerosis" refers to any hardening of the arteries, and
"atherosclerosis" is a type of arteriosclerosis characterized by
irregularly distributed lipid deposits on the internal walls of
large and medium-sized arteries. Such deposits can be provoked by
various types of damage of the internal arterial walls, including
damage caused by high blood pressure, tobacco smoking, toxic
substances, etc.
... ... *myocardial infarction: In general, a sudden
insufficiency of the blood supply to any of the muscle tissues of
the heart.
... ... *Chlamydia pneumoniae: The chlamydiae are bacteria that
lack mechanisms for the production of metabolic energy (they
cannot synthesize adenosine triphosphate (ATP)), which restricts
them to an intracellular existence. The extracellular form is a
stable spherical particle approximately 0.3 microns in diameter.
This attaches to the surface of host cell, is taken in by the
host cell by phagocytosis ("cell eating"), and once inside the
host cell, the bacterium enlarges and begins to replicate. There
are various types of chlamydiae causing various diseases,
including trachoma (an eye disease), pneumonia, and psittacosis
(the human form of a parrot disease).
... ... *Helicobacter pylori: This is a rod-shaped bacterium
associated with inflammation of the lining of the stomach
(gastritis), peptic ulcer disease, and possibly cancer. The
organism has multiple *flagella at one pole and is actively
motile. Many patients infected with H. pylori do not have any
symptoms at all.
... ... *flagella: A flagellum is a long threadlike extension
providing locomotion for a cell.
... ... *periodontal diseases: In general, any disease of the
tissues surrounding the teeth.
... ... *thrombotic stroke: In general, a sudden loss of blood
supply to a region of the brain produced by a blood clot
(thrombus) in an artery.
... ... *tetracycline: One of a group of naphthacene derivatives
that are broad spectrum antibiotics. The tetracyclines inhibit
protein synthesis in susceptible bacteria.
... ... *quinolone: Synthetic analogs of nalidixic acid, they act
as antibiotics by inhibiting DNA synthesis in bacteria.
... ... *macrolides: A subclass of erythromycins (see next note).
... ... *erythromycin: One of a class of widely used antibiotics
(macrolides and azolides), all of which inhibit protein
synthesis.
... ... *sulfonamides: A large group of compounds inhibiting the
utilization of an important metabolite (p-aminobenzoic acid) in
bacteria.
... ... *penicillins: A class of chemically related antibiotics
which inhibit cell wall synthesis in bacteria. Originally derived
from the mold Penicillium.
... ... *cephalosporins: Derived from fungi, these antibiotics
inhibit bacterial cell wall synthesis.
... ... *prospective: A "prospective" trial or study is one
designed from the beginning to measure the results of controlling
specific variables. In other words, one follows the future
history of experimental and control populations, rather than
examining the past history of a general or selected population to
search for correlations between factors.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 4Jun99


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 
IN FOCUS: ON THE SPECTRA OF THE STARS
"The rainbow is the spectrum of the Sun... In 1814... the
spectrum of the Sun was obtained in such purity than an amazing
detail was seen and studied by the German optician, Fraunhofer.
He saw that the multiple spectral tints, ranging from delicate
violet to deep red, were crossed by hundreds of fine dark lines.
In other words, there were narrow gaps in the spectrum where
certain shades were wholly blotted out. For fifty years, many
searched for a Rosetta-stone to solve the baffling mystery of
these hieroglyphics traced by Nature's hand in the radiant
sunbeams. The solution was actually found by studying the light
of one of the best-known and commonest substances existing on our
planet... This omnipresent earthly substance, salt, or at least
its sodium constituent, exists in the Sun and distant stars. We
must remember that the word spectrum is applied not only to
sunlight, but also to the light of any glowing substance when its
rays are sorted out by a prism or a grating. Each substance thus
treated sends out its own vibrations of particular wave lengths,
which may be likened to singing its own song. Now the spectrum of
salt, called sodium chloride by chemists, is very simple and
includes two bright yellow lines. In the spectrum of the Sun
exactly the same shades of yellow are cut out by two black lines. 
Could there be any connection? Could the earthly yellow lines be
made to change to black? Yes, it was found by experiment that
they would do so instantly if a cooler vapor of salt were placed 
between the prism and a source of light that emits all wave
lengths. Thus it was reasoned that some of the bright yellow
light from the Sun's hot surface was absorbed by cooler sodium
vapors in the Sun's atmosphere. Likewise two thousand black lines
in the Sun's spectrum were traced to iron, and indeed all the
common substances, so familiar to us here on the Earth, have been
found to exist in the Sun by comparing its absorption spectrum
with the bright line spectra given by these substances in
laboratories. It might have been expected that the Sun, our
parent, would contain the familiar earthly elements, as we were
certainly, in a distant age, bone of his bone and flesh of his
flesh. But what about the stars, so far away, apparently so
faint? The Sun outshines even the brilliant Sirius, the Dog Star,
ten billion times. But the light of a star may be magnified
several thousand fold by a telescope. Then, with a spectroscope
attached to the telescope, we may behold a radiant and beautiful
sight, for the twinkling starlight becomes a band showing all the
rainbow colors, also crossed by the tell-tale dark lines. The
stars then are suns."

--- Annie Jump Cannon: "Classifying the Stars" 
    In _The Universe of Stars_, H. Shapley and C.H. Payne (eds.)
    (Harvard College Observatory Press, Cambridge 1929)

[Astronomer Annie Jump Cannon (1863-1941), who held the title
"Curator of Photographs" at Harvard College Observatory, indexed
the spectra of more than 250,000 stars during her career, and
this work helped lay the foundation of modern astrophysics. She
studied astronomy at Wellesley College and Radcliffe College. In
her time, because she was a woman, she was barred from direct use
of the Harvard Observatory telescopes.]


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