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.

November 6, 1998 -- Vol. 2 Number 45

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

It is impossible to dissociate language from science or science
from language, because every natural science always involves
three things: the sequence of phenomena on which the science is
based; the abstract concepts which call these phenomena to mind;
and the words in which the concepts are expressed. To call forth
a concept, a word is needed; to portray a phenomenon, a concept
is needed. All three mirror one and same reality. Words are thus
required to preserve and transmit ideas, so that it is clear that
the advancement of a science and the improvement of its technical
vocabulary go hand in hand. No matter how certain we are of the
phenomena, no matter how adequately our concepts reflect them, we
cannot help perpetuating wrong ideas unless we have a precise
terminology in which to express ourselves.
-- Antoine Laurent Lavoisier (1743-1794)

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

Contents of This Issue:

1. A Criticism of US Academic Research in Biology
2. Research Fraud Scandal in Germany: An Update
3. Particle Physics: On Gluons and Glueballs
4. Evidence of Earth Global Subsurface Temperature Increase
5. Human Evolution: The Fate of the Neanderthals
6. On Parkinson's Disease
7. Aging, Lifespan, and Senescence
8. An Evaluation of Chiropractic and McKenzie Treatments

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

1. A CRITICISM OF US ACADEMIC RESEARCH IN BIOLOGY
Most academic biologists over 50 remember a time when the center
of biology on the campus was the decaying zoology building, or
the connected decrepit zoology-botany buildings, display cases
crowding halls lit with yellow tungsten bulbs, tiny laboratories
cluttered with old microscopes and split wooden stools, and
everywhere the faint smell of formaldehyde wafting in from the
anatomy labs despite open windows to let in fresh air and the
smell of outside greenery. Those were the days before molecular
biology and millions of dollars for research abruptly loomed and
made the earth tremble. These days the center of biology on
campus is more likely to be a cluster of new multi-million-dollar
buildings housing the laboratories of molecular biology, the
windows in these corporate-appearing buildings sealed, the
circulating air carefully filtered, and on each floor a multitude
of laboratory technicians busy with the bench work formerly the
daily grind of professors. With apologies to Pinter, the past is
definitely another world. The emergence of heavily funded
molecular biology has been called a profound scientific
revolution in biology, a blessing of the biological sciences and
the research universities that foster them, but not everyone
agrees, and indeed some people think of the change in academic
biology as the ascendance of a research Godzilla.
... ... Steven Vogel reviews the current situation in US
university biology research, and the author makes the following
points: 1) Current American biology is experiencing the impact of
a growing institutional preference for expensive science -- a
preference with pernicious implications for universities and for
science. 2) At present, the majority of biologists focus on
molecules and subcellular phenomena, and most of the money spent
on biological research supports this work. The combination of
overall expense and high cost per investigator has turned
molecular biology into "academically correct" biology. 3)
Academically correct biology has 4 important features: a) it
seeks molecular explanations; b) it views scientific progress as
a matter of incremental accretion of detail; c) its fairly
immediate goal is human therapy; and, d) its operation is
unabashedly entrepreneurial. All four characteristics prove
conveniently consistent with an overall goal of institutional
growth, and used together as a basis for academic decision-
making, they produce a displacement of other kinds of scientific
investigation. 4) The dominance of academically correct biology
is produced by the availability of support for it, particularly
support from the US National Institutes of Health (NIH), which
has become the largest source of funding for scientific
activities at many universities -- and NIH seems especially fond
of the chemo-reductionist paradigm. 5) The unprecedented
concentration of personal and material resources in molecular
biology may have produced a peculiar paradox. The field may now
be progressing at a rate as slow as that of any area of science
ever actively pursued -- if we consider conceptual progress
relative to the number of active investigators. 6) Science
without data is unimaginable, but data are not science. Equating
the acquisition of data with the progress of science implies that
great generalizations will necessarily follow when sufficient
data are gathered -- an uncertain proposition. 7) The history of
science indicates that few major conceptual advances were driven
by anticipation of immediate utility... An excessive focus by a
university on medical therapy as a short-term research goal is
unhealthy. Too often resources will be concentrated on projects
of lower fundamental importance and intellectual interest. 8)
Especially pernicious are the self-serving attitudes that good
science costs large amounts of money and that the quality of
scientists -- and of science departments -- can be judged by the
funds they raise. 9) Academically correct biology damages mostly
by displacement. The multidimensionality of biological science,
the diversity of elements that should matter for academic
success, the idea of science as more than a compendium of facts
-- all are severely compromised.
-----------
S. Vogel (Duke University, US)
Academically correct biological science.
(American Scientist Nov/Dec 1998 86:504)
QY: Steven Vogel 
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 6Nov98

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

Related Background:

BIOLOGY FUNDING VS. PHYSICS FUNDING: UNEASE EXPRESSED
The journal *Nature*, in a recent editorial, criticizes US
President Bill Clinton for asserting that the next 50 years will
be "very likely characterized predominantly as the age of
biology." The journal also criticizes the emphasis on the news of
biology, "trumpeted by the media worldwide". Politicians ought to
understand, *Nature* says, that the results of physics "have a
way of unobtrusively and unpredictably invigorating apparently
unrelated disciplines and technologies, even to a revolutionary
extent..." Ergo, support for the physical sciences continues to
be in the best interests of society.
(Nature 8 Jan 98)

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

Related Background:

ON FASHIONS IN SCIENCE AND TECHNOLOGY
Rolf Landauer (IBM Corp., US), in a review of fashions in science
and technology, points out both the negative and positive aspects
of such fashions in general, and in particular in his own field,
condensed matter physics. Among other problems, Landauer notes:
1) Fashions in science and technology draw attention away from
other deserving areas. 2) Funding agencies make an apparently
sensible initial decision to support a particular exploratory
scientific path, but they too easily become emotionally tied to
their choice. 3) The competition for grants and employment causes
public relations activities to have an increasing greater role in
the practice of science. 4) Whereas in the past judgments in an
institution about the quality of a colleague's work were based on
an assumed understanding of that work, at present promotions
depend on the ability to get funding, citation index scores,
etc., and in-house evaluations often are less important than
external evaluations. 5) These days a single publication is lost
in the deluge of papers, and the only way to be heard in the
scientific community is to repeatedly publish essentially the
same information over and over again. This produces a large
publication volume per researcher, which in turn forces other
researchers to do the same if they want to advance in status in
their installations and in their field. As any working scientist
is aware, these are only some of the problems inherent in the
present structure of professional science. Landauer suggests that
fashions in science have a mostly negative impact, and that more
serious debate is needed about how fashions affect professional
science and the training of new scientists.
QY: Rolf Landauer, Thomas J. Watson Research Center, IBM Corp.,
Yorktown Hts, NY US.
(Physics Today December 1997) (Science-Week 12 Dec 97)


2. RESEARCH FRAUD SCANDAL IN GERMANY: AN UPDATE
What has been called in Germany and elsewhere "Germany's biggest
ever scientific fraud" is apparently still without closure. The
essence of the case (details are provided in the attached
background material) is the involvement of 2 molecular
biologists, Marion Brach and Friedhelm Herrmann (who both worked
and lived together during their scientific collaboration at
Harvard, Freiburg, and Berlin), in an alleged systematic
fabrication of data in 37 publications over a 9 year period
ending in 1996. It is now nearly 2 years after the affair was
first revealed, but no case has yet been brought to court.
Prosecutors in Germany are evidently finding it more difficult
than expected to bring charges against the two scientists
involved, both of whom achieved full professorships on the basis
of the apparently fraudulent research reports. After being
dismissed as full professor at the University of Lubeck in 1997
(she assumed the post in 1996), Brach evidently left Germany and
she is now reported to be working in New York. Herrmann resigned
his professorship at the University of Ulm and now works in
private medical practice in Munich. Herrmann continues to deny
any involvement in misconduct, and says the failure to bring
charges against him is proof of his innocence. Meanwhile
Germany's main university research funding agency, Deutsche
Forschungsgemeinschaft, has set up a task force to determine the
"full extent of any scientific damage" caused by the alleged
fraudulent publications.
-----------
A. Abbott (*Nature*)
German scientists may escape fraud trial.
(Nature 8 Oct 98 395:532)
QY: Alison Abbot 
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 6Nov98

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

Related Background:

ABDERHALDEN'S FRAUD REVISITED
Last year was not a good year for German biological and medical
science, since 1997 was marked by a major fraud scandal involving
two full professors apparently involved in the fabrication of
data published in dozens of scientific papers during a 9-year
period. That story is not yet finished (see background material
below). Now from Germany comes the publication of a "commentary"
by two scientists, U. Deichmann and B. Muller-Hill, the
commentary revisiting what has come to be considered the
fraudulent career of German scientist Emil Abderhalden
(1877-1950). Abderhalden was a biochemist involved in designing
tests for various clinical disease entities, the tests involving
what he called "defense enzymes" (Abwehrfermente), enzymes which
he claimed to have identified, and which according to his
analyses were specific proteases produced when humans were
challenged by foreign proteins. During the years 1912 to 1950,
Abderhalden enjoyed the status of one of the most eminent
scientists in Germany, was professor of physiology and
physiological chemistry at Halle University, president of the
oldest German academy of science (the Leopoldina), editor of
several journals, and author of several books and more than 1000
research papers -- and all of this notwithstanding, the consensus
today is that nearly all of his research on the so-called
"defense enzymes" was completely fraudulent, with scores of
colleagues and underlings either explicitly or implicitly
colluding in the fraud over a period of decades. It is an ugly
story with political tangents (e.g., Joseph Mengele, the
notorious Auschwitz doctor, was one of Abderhalden's proteges).
In their commentary, Deichmann and Muller-Hill conclude: "The
elite of today [the biomedical elite in Germany] are loyal
students of the old elite, and they have learned and internalized
the old values. Has medical, clinical science in Germany today
really changed that much? We doubt it. The Brach-Herrmann-
Mertelsmann affair provides a brief glimpse into the abyss of
medical science in Germany. Will it be soon forgotten by the
German medical elite, or will there be real change in the spirit
of true science?" [Editor's note: Roland Mertelsmann, Professor
Herrmann's department head, was co-author of 25 suspected papers
produced by Herrmann, but has pleaded non-involvement in the
research.]
QY: Ute Deichmann, Institute of Genetics, Cologne University,
Weyertal 121, 50931, Koeln, DE.
(Nature 14 May 98 393:109) (Science-Week 5 Jun 98)

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

Related Background:

GERMAN RESEARCHER ADMITS FRAUD AND CHARGES ACADEMIC COVER-UP
Producing another chapter in the scientific fraud case that has
caused an apparent sensation in Germany, Marion A. Brach, one of
the accused scientists, has published a letter in the journal
*Nature* in which she points out the following: 1) She has
confessed to falsifying scientific papers; 2) she has resigned
her position as a full professor at the University of Lubeck; 3)
she does not believe further victimization is appropriate; 4) she
has concluded that the various German investigating commissions
met only with the intention of limiting damage to the German
academic community rather than with the intention of discovering
the full extent of culpability; 5) the German government has
reneged on its legal agreement to provide her with severance pay
following her early confession and resignation; 6) official
bodies have found it expedient to imply that she was the major or
only culprit in the affair.
QY: Marion A. Brach, c/o Walter F. Kalthoff, Pacellistr. 14,
D-80333, Muenchen, DE.
(Nature 2 Apr 98) (Science-Week 17 Apr 98)

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

Related Background:

MORE DEVELOPMENTS IN GERMAN SCIENTIFIC FRAUD CASE
The scientific fraud case that has been shocking the German
intellectual community these past months, and which is claimed to
be the worst case of scientific fraud in that country since 1945,
continues to be a public spectacle. The scandal involves two
German molecular biologists, Marion Brach (who has resigned as a
Professor at Lubeck University), and Friedhelm Herrmann (a
suspended Professor at Ulm University). Brach has admitted
falsifying published data while she worked under the supervision
of Herrmann at the Max Delbruck Center for Molecular Medicine a
few years ago. Herrmann claims he is only a clinician and had
nothing to do with the laboratory bench work. Herrmann is a
prominent hematologist and a leading genetic therapy researcher.
The two biologists had worked together for some time, and each
received professorships on the basis of that work. (Herrmann's
salary was apparently US$278,000 per year). Now it has been
announced that Herrmann is suing various academic investigators
in the case for DM10 million (US5.6 million) in compensation for
damage to his career. In addition, there is now a claim by a new
investigation team that the two accused researchers also
published falsified data earlier in their careers. (Nature 11
Sep) (Science-Week 26 Sep 97)
-------------------
AN UPROAR OVER SCIENTIFIC FRAUD IN GERMANY
The German scientific community was rocked by scandal this
spring, and the resulting repercussions are apparently not yet
complete. The brouhaha involves two German molecular biologists,
Marion Brach (recently resigned as a Professor at Lubeck
University), and Friedhelm Herrmann (a suspended Professor at Ulm
University). Brach has admitted falsifying published data while
she worked under the supervision of Herrmann at the Max Delbruck
Center for Molecular Medicine a few years ago. Herrmann claims he
is only a clinician and had nothing to do with the laboratory
bench work. Herrmann is a prominent hematologist and a leading
genetic therapy researcher. The two biologists have worked
together for some time, and each received professorships on the
basis of that work. All of that work is now being investigated,
and the German government has established a commission of
international scientific experts to discuss research standards
and the procedures for scientific oversight in German and
internationally.
(Science 11 Jul 97) (Science-Week 18 Jul 97) 


3. PARTICLE PHYSICS: ON GLUONS AND GLUEBALLS
The physics of elementary particles is in the midst of an era of
conceptual complexity that some people find unsettling and other
people find invigorating. A quark is a hypothetical fundamental
particle, having charges whose magnitudes are one-third or
two-thirds of the electron charge, and from which the elementary
particles that have an apparent internal structure may in theory
be constructed. Quarks are believed to be held together through
the exchange of gluons, massless particles that carry the *strong
force. At the present time, 18 different quarks with various
properties are thought to exist, with a corresponding number of
*antiquarks. Gluons have a "sticking" property -- they can
agglomerate -- and agglomerations of gluons alone are called
"glueballs". ... ... F.E. Close and P.R. Page review current
ideas concerning gluons and glueballs, and the authors make the
following points: 1) Along with fractional electric charge,
quarks also have "flavor" in 6 varieties (up, down, charm,
strange, top, and bottom), and "color" (red, yellow, or blue).
[*Note #1] 2) Quarks may also attach to antiquarks, particles
that have opposite charge, and an antiquark comes in anticolors
(antired, antiyellow, antiblue). An anticolor is mathematically
denoted by negative color, and a color and its anticolor attract.
3) The theory of electromagnetism describes the attraction
between opposite electric charges. In the 1940s, physicists
merged electromagnetism with relativity and quantum theory,
creating quantum electrodynamics (QED). This theory -- the most
successful theory known to physics -- holds that the
electromagnetic force is transmitted by massless objects called
photons. These quanta of light banish the classical idea of
action at a distance. It can be said that photons bounce between
an electron and an antiparticle (the positron) in such a manner
as to draw the two together. 4) The equivalent theory of color
charges, which communicate via the *strong force, is called
quantum chromodynamics (QCD). Gluons, the massless quanta of the
strong force, transmit the color interactions. 5) Gluons are
fundamentally different from photons. Photons do not have charge,
so one photon cannot push or pull on another photon. Gluons,
however, are themselves colored. A red quark, for example, can
turn into a blue quark by radiating a red/antiblue gluon.
Basically, a gluon can attract another gluon. Another difference
between photons and gluons is that while photons uniformly
surround electrons, forming a shell with spherical symmetry whose
density falls off with distance, gluons are not uniformly
distributed and instead clump together into a tube linking a
quark and an antiquark. The color originating in the quark can be
thought to "flow" through the tube to the antiquark, where it
becomes absorbed. 6) In 1972 H. Fritzch and M. Gell-Mann
predicted that two or more gluons can combine into a strongly
bound, neutral-colored particle of pure "glue". This hypothetical
object is called a "glueball". A glueball is thought to have a
radius of 0.5 x 10^(-15) meters (less than that of a proton), and
exist for less time than light takes to cross a hydrogen atom. 7)
The authors state that although the idea of glueballs was
elegant, quantum chromodynamics is a "rather messy theory", since
the peculiar "sticky" character of the strong force makes it
impossible to perform exact calculations. Almost everything known
about color and glue comes not from direct calculation but from
massive computer simulations known as "lattice QCD". 8) Finally,
the authors discuss various current and planned future attempts
to detect the existence of glueballs, and they conclude: "One of
these experiments will, we fondly hope, upturn unambiguous
evidence of unadulterated glue."
----------
F.E. Close and P.R. Gage (2 installations, UK US)
Glueballs.
(Scientific American November 1998)
QY: Frank E. Close, University of Oxford, UK.
-----------

Text Notes:
... ... *strong force: The fundamental forces comprise the
gravitational force, the electromagnetic force, the nuclear
strong force, and the nuclear weak force.
... ... *antiquarks: The antimatter quark entity. In general,
antiparticles are homologs of elementary particles but with
opposite charge. The positron, for example, is the antimatter
particle homologous to the electron. Matter composed entirely of
antiparticles is called antimatter.
... ... *Note #1: In this context, flavors and colors are labels
for specific sets of properties associated with specific types of
quarks. Some people call these labels "whimsical", but perhaps
there is some sense to the whimsy, since it emphasizes that at
the present time we are apparently unable to describe the
properties and behaviors of the fundamental particles with
classical language (i.e., with the language of old models).
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 6Nov98

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

Related Background:

EVIDENCE FOR A QUARK-GLUON PLASMA
... According to current theory, quarks and gluons cannot exist
in isolation. But theory also predicts that at temperatures
10^(12) degrees Kelvin or greater (such as existed during the
first 0.01 second of the history of the universe) a drastic
change in the structure of nuclear matter occurs, and only
descriptions in terms of quarks and gluons apply. A plasma is a
gas consisting entirely of equal numbers of positive and negative
charges. ... ... F. Wilczek (Institute for Advanced Study
Princeton, US), in a short review of recent experiments that for
the first time apparently produced a quark-gluon plasma, "an
extraordinary new state of matter", suggests that an important
question is whether, as a function of temperature, the transition
from ordinary matter to a quark-gluon plasma is continuous or
discontinuous. A discontinuous transition could imply explosive
instabilities, which in turn may have been important in the
evolution of the early universe.
QY: Frank Wilczek 
(Nature 22 Jan 98) (Science-Week 23 Jan 98)

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

Related Background:

FIRST EVIDENCE OF AN EXOTIC MESON
In particle physics, the term "meson" has had an interesting
history. Between 1939 and 1947, it was used to refer to what are
now called "muons". In 1947, the definition changed, and meson
now refers to an unstable, strongly interacting sub-nuclear
particle that consists of a quark bound to an anti-quark. There
is more than one type of meson, but they all consist of quarks
and anti-quarks bound together by "gluons". In the 1970s,
theorists predicted the existence of "exotic" mesons whose gluon
linkages between quarks and anti-quarks had the mathematical
properties of vibrating strings. But no one had or has yet
provided evidence of exotic mesons. ... ... Now Suh-Urk Chung et
al (Brookhaven National Laboratory, Upton NY US) have apparently
finally identified such a particle in collisions of fast-moving
mesons called "pions" with protons in a liquid hydrogen target.
They have determined the exotic meson's mass to be approximately
1.4 Gev (billion-electron-volts), and another laboratory, using a
completely different experimental method, has evidently
independently confirmed an exotic meson with the same mass of 1.4
Gev. But whatever excitement there is about finally identifying
the exotic meson, it is apparently combined with puzzlement,
because the revealed mass is less than what had been predicted.
Revisions of theory may be in order, since in the arena of
particle physics, revisions are the usual consequence of
puzzlement.
QY: S-H. Chung, Brookhaven National Lab. (516) 344-8000.
(Phys. Rev. Lett. 1 September) (Science-Week 12 Sep 97)


4. EVIDENCE OF EARTH GLOBAL SUBSURFACE TEMPERATURE INCREASE
Temperature changes at the surface of the Earth propagate slowly
downward into the rocks beneath the surface and modify the
ambient thermal conditions. Present-day subsurface temperatures
thus provide evidence of temperature changes that have occurred
at the surface in the past. The information contained in this
geothermal archive is a complement to instrumentally acquired
temperature data and to various types of indirect methods for
understanding Earth's recent surface temperature history. Drilled
boreholes are a direct method of measuring subsurface
temperatures. Borehole temperature measurements are typically
made at 10 meter depth intervals with an electrical resistance
thermometer that can resolve temperature changes of 0.01 degree
centigrade. ... ... H.N. Pollack et al now report analyses of
underground temperature measurements from 358 boreholes in
eastern North America, central Europe, southern Africa, and
Australia. The authors report the measurements indicate that in
the 20th century the average surface temperature of Earth has
increased by approximately 0.5 degrees centigrade, and that the
20th century has been the warmest of the past 5 centuries. Also,
the subsurface temperatures indicate that Earth's mean surface
temperature has increased by approximately 1.0 degrees centigrade
over the past 5 centuries. The authors suggest these geothermal
data offer an independent confirmation of the unusual character
of 20th century climate that has emerged from recent indirect
thermal history measurements.
-----------
H.N. Pollack et al (3 authors at 2 installations, US CA)
Climate change record in subsurface temperatures: A global
perspective.
(Science 9 Oct 98 282:279)
QY: H.N. Pollack, Univ. of Michigan 313-764-7433.
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 6Nov98

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

Related Background:

A PROPOSAL FOR A COMMON-SENSE CLIMATE INDEX
Hansen et al (National Aeronautics and Space Administration, US)
propose an index of climate change based on practical climate
indicators such as heating degree days and the frequency of
intense precipitation. The authors report they find that in most
regions the index is positive, the sense predicted to accompany
global warming. In a few regions, especially in Asia and western
North America, the index indicates that climate change should be
apparent already, but in most places climate trends are too small
to stand out above year-to-year variability. The climate index is
strongly correlated with global surface temperature, which has
increased as rapidly as projected by climate models in the 1980s.
The authors suggest that the global area with obvious climate
change will increase notably in the next few years, but the
growth of greenhouse gas climate forcing has declined in recent
years, providing an opportunity to keep climate change in the
21st century at levels less than "business-as-usual" scenarios.
QY: James Hansen 
(Proc. Natl. Acad. Sci. US 14 Apr 98 95:4113)
(Science-Week 15 May 98)

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

Related Background:

A SIMULATION MODEL FOR MODERN AND GLACIAL CLIMATES
In 1920, the meteorologist Milutin Milankovic proposed that small
changes in Earth's orbit, precession, and inclination affect the
heat balance and modify climate (the alterations called "solar
forcing"). The Milankovic hypothesis was not taken seriously
until 1976, when teams studying sediment cores from the ocean
floor constructed a history of ocean temperature that matched the
predictions of the Milankovic hypothesis, with two different
ocean cores providing similar results. Until now, simulation
models of Earth's climate history have been either ocean models
or atmosphere models, with no model accounting for the interact-
ions between the ocean and the atmosphere aside from adjustable
heat flux parameters that result in only a weak theory. In
general, complete solutions of these individual models have
involved prohibitive computation times. The term "glacial
maximum" refers to the time or position of the greatest extent of
glaciation, and the term "hydrologic cycle" refers to the
complete cycle through which water passes: from the ocean,
through the atmosphere, to the land, and back to the ocean.
... ... Ganopolski et al (4 authors at Potsdam Institute for
Climate Impact Research, DE) now report a moderately simplified
global coupled ocean-atmosphere model to simulate the equilibrium
climate of both the present and of the last glacial maximum, and
that the model successfully predicts the atmospheric and oceanic
circulations, temperature distribution, hydrologic cycle, and
sea-ice cover of both periods without using flux adjustments. The
authors suggest that changes in oceanic circulation, particularly
in the Atlantic Ocean, play an important role in glacial cooling,
and that ultimately the challenge is to produce a simulation of
glacial cycles driven only by the Milankovic cycles in solar
forcing.
QY: Stefan Rahmstorf 
(Nature 22 Jan 98) (Science-Week 6 Feb 98)


5. HUMAN EVOLUTION: THE FATE OF THE NEANDERTHALS
The current consensus in paleoanthropology is that the
Neanderthals were an extinct side-line of human evolution.
European Neanderthals are thought to have diverged from the
lineage that gave rise to modern humans at least 500,000 years
ago. The current view is that approximately 30,000 to 40,000
years ago the Neanderthals were replaced by modern populations,
probably from an ultimately African source. A present debate
concerns how this population replacement occurred.
... ... Paul Mellars, in a short review of a recent conference
(28-30 Aug 1998, Gibraltar, UK) on the Neanderthals, makes the
following points: 1) The current consensus is that in the
southern part of the Spanish peninsula, roughly to the south of
the Ebro valley, the local Neanderthals survived for at least
5000 to 10,000 years after the arrival of modern populations in
the adjacent parts of northern Spain and the Mediterranean coast.
2) The most likely explanation for the prolonged coexistence of
these two populations lies in the ecological differences between
the northern and southern parts of the Iberian peninsula. 3)
Studies of Neanderthal skeletal remains reinforce the conclusion
that the Neanderthals were a divergent lineage that probably made
no contribution to the evolution of anatomically modern humans.
This is consistent with the DNA evidence that the two lineages
separated at least 500,000 years ago, and even longer divergence
times are favored by some researchers. 4) The impression at the
end of the conference was that the Neanderthals were really quite
different from humans -- well adapted to survive in the harsh
glacial environments of Europe, but with distinct anatomical and
behavioral patterns different from their modern human successors.
The author concludes: "The eagerness of some scientists to claim
close kinship with the Neanderthals could come close to denying
that human evolution actually took place."
-----------
Paul Mellars (University of Cambridge, UK)
The fate of the Neanderthals.
(Nature 8 Oct 98 395:539)
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 6Nov98

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

Related Background:

FIRST ANALYSIS OF DNA FROM A NEANDERTHAL BONE
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 -- or was the
Neanderthal a separate branch that became extinct? Until
recently, the primary laboratory method of investigation of such
a question was analysis of the morphology of bone fragments. This
week, the field of paleoanthropology has apparently crossed an
important watershed, as M. Krings et al (University of Munich,
DE; Pennsylvania State University, US) report the first analysis
of DNA from an extinct human, in this case DNA extracted from the
actual Neanderthal skeleton found near Dusseldorf in 1856. The
key to the investigation was the analysis of mitochondrial rather
than nuclear DNA. Mitochondrial DNA is usually present in
concentrations two or three orders of magnitude greater than
nuclear DNA, and they were able to find enough of it still intact
to amplify with the PCR technique and piece together a total DNA
sequence of 379 base pairs. Comparison of this sequence with
contemporary human sequences leads to the conclusion that
Neanderthal and modern man are separate evolutionary lines, and
that the latter did not evolve from the former. The work will
have to be replicated with other Neanderthal fossils, but most
paleoanthropologists are excited by the results and expect them
to be confirmed. The technology of evolutionary paleoanthropology
has evidently now progressed from caliper measurements of bones
to measurements of bone DNA fragments.
(Cell 11 July) (Science-Week 18 Jul 97)

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

Related Background:

A POSSIBLE COMMON ANCESTOR OF NEANDERTHAL AND HOMO SAPIENS
The reconstruction of human evolutionary history is a slow and
halting process, the evidence scattered and fragmentary. But
paleoanthropologists persist. They gather the evidence, when they
can find it, and at intervals they conclude it necessary to
redraw the theoretical lines of evolution leading to modern man.
This week, from Spain, there is a suggestion that once again the
lines need to be redrawn. Antonio Rosas et al [National Museum of
Natural Sciences, Madrid ES; Complutense University of Madrid
(ES); Rovira i Virgili University, Tarragona (ES)] have presented
evidence from a find of 80 human fossil remains recovered between
1994 and 1996 in the Pleistocene cave site of Gran Dolina, Sierra
de Atapuerca, Burgos (ES). Included among the fossils is that of
an adolescent male, the bones approximately 800,000 years old,
with facial features a mix of both Neanderthal and modern
aspects. The Spanish team has named this a new species, Homo
antecessor, and they suggest the simplest explanation for the
various skeletal attributes is that H. antecessor is the common
ancestor of both H. neanderthalensis and H. sapiens, and that the
evolutionary lines need to be redrawn to show these two as
separate branches from the H. antecessor stem. Not all
paleoanthropologists agree, primarily because the basis for the
introduction of a new species into the evolutionary gallery is
the partial fossil of a single immature individual, in this case
a boy 10 or 11 years old. Despite the disagreement, what is
certain is that the evidence will be the focus of attention among
paleoanthropologists for some time.
(Science 30 May) (Science-Week 5 Jun 97)


6. ON PARKINSON'S DISEASE
Parkinson's disease, first described by James Parkinson more than
180 years ago, is a major neurodegenerative disease of unknown
cause. ... ... A.E. Lang and A.M. Lozano present the first of a
2-part extensive review of the disease and make the following
points: 1) The disease effects over 1 million people in North
America. Age is the single most consistent risk factor, and the
prevalence of the disease is expected to rise steadily in the
future with the increasing age of the general population.
Mortality is 2 to 5 times as high among affected persons as among
age-matched controls, resulting in a marked reduction in life
expectancy. In general, neurodegenerative diseases (Parkinson's
disease, motor neuron disease, and dementia) are projected to
surpass cancer by the year 2040 as the second most common cause
of death among the elderly. 2) Parkinson's disease occurs
throughout the world, in all ethnic groups, and affects both
sexes approximately equally or with a slight predominance among
males. The prevalence increases exponentially with age between 65
and 90 years. Approximately 0.3 percent of the general population
and 3 percent of people over the age of 65 have the disease. 5 to
10 percent of patients have symptoms before the age of 40. The
lowest reported incidence is among Asians and African blacks,
whereas the highest reported incidence is among whites. 3) The
classic triad of major signs of Parkinson's disease consists of
tremor, rigidity, and akinesia (absence or loss of the power of
voluntary movement). The diagnosis is made on the basis of
clinical criteria, and underdiagnosis is common. Misdiagnosis is
also common, because the syndrome may be produced by different
causes such as drugs, *Wilson's disease, and other
neurodegenerative diseases. Although the neuropathological
examination is the standard for diagnosis of Parkinson's disease,
there is still no biological marker that unequivocally confirms
the diagnosis. 4) At the cellular level, Parkinson's disease is
characterized by the progressive death of specific but
heterogeneous populations of neurons, including *dopaminergic
neurons in the *substantia nigra, *aminergic *brainstem nuclei,
the *cholinergic *nucleus basalis of Meynert, *hypothalamic
neurons, and small *cortical neurons. In addition, degeneration
of nerve cells in the *olfactory bulb, *sympathetic ganglia, and
*parasympathetic neurons in the gut may also be involved in the
disease. 5) The mechanisms responsible for cell death in
Parkinson's disease are largely unknown. Evidence suggests that
neuronal death in the substantia nigra may involve *apoptosis,
but this idea is not universally accepted. Among the factors that
have been implicated in neuronal degeneration in this disease are
*mitochondrial dysfunction, *oxidative stress, the actions of
*excitotoxins, deficient *neurotrophic support, and immune
mechanisms. A critical question is why specific neurons are
selectively vulnerable to the disease.
-----------
A.E. Lang and A.M. Lozano (2 installations, CA)
Parkinson's disease.
(New England J. Med. 8 Oct 98 339:1044)
QY: Anthony E. Lang, Toronto Hospital, 399 Bathurst St., MP 11,
Toronto, ON M5T 2S8 CA.
-----------

Text Notes:
... ... *Wilson's disease:  A rare genetic disease involving
copper metabolism dysfunction.
... ... *dopaminergic neurons: Nerve cells that use dopamine as a
*neurotransmitter substance. "Levodopa", which is used in the
treatment of Parkinson's disease, is the biologically active form
of "dopa", which is converted into dopamine. Dopamine = 3,4-
dihydroxyphenylethylamine. Dopa = 3,4-dihydroxypheynylalanine.
... ... *neurotransmitter substance: Neurotransmitters are
chemical substances released at the terminals of nerve axons in
response to the propagation of an impulse to the end of that
axon. The neurotransmitter substance diffuses into the synapse,
the junction between the presynaptic nerve ending and the
postsynaptic neuron, and at the membrane of the postsynaptic
neuron the transmitter substance interacts with a receptor.
Depending on the type of receptor, the result may be an
excitatory or an inhibitory effect on the postsynaptic nerve
cell.
... ... *substantia nigra: A large cell mass at the base of the
brain that receives input from a number of cortical and
subcortical structures ("cortical" refers to cerebral cortex).
... ... *aminergic: In this context, the term refers in general
to neurons whose neurotransmitters are amines.
... ... *brainstem nuclei: Clusters of nerve cells in the
brainstem, which is a phylogenetically old region of the central
nervous system that among other things contains control centers
for fundamental physiological processes such as breathing and
heart rate. Anatomically, the brainstem is the connecting region
between the brain above it and spinal cord below it.
... ... *cholinergic: Refers to synaptic transmission mediated by
the release of acetylcholine.
... ... *nucleus basalis of Meynert: One of the basal nuclei
(neuron clusters) lying deep in the subcortical white matter of
the frontal lobes and involved in the organization of motor
behavior.
... ... *hypothalamic neurons: A deep brain structure with
various clusters of nerve cells controlling several important
homeostatic functions such as temperature regulation and food
intake, and in addition the sex drive, aggressive emotions,
psychosomatic effects, etc. The hypothalamus essentially
integrates the activity of the autonomic nervous system, and it
acts as an intermediary between the endocrine (hormone) system
and the nervous system, with various hypothalamic neuron types
secreting hormones themselves. In general, the term "hormones"
refers to chemical messengers which are distributed systemically
via the bloodstream. 
... ... *cortical neurons: In general, neurons of the cerebral
cortex, the phylogenetically newer part of the brain that
controls the higher analysis of sensory data and most non-
automatic activities.
... ... *olfactory bulb: Olfactory relay station that receives
axons from the olfactory cranial nerve and transmits the
information via the olfactory tract to higher centers.
... ... *sympathetic ganglia: Nerve cell clusters in the
sympathetic nervous system, which is a division of the peripheral
autonomic nervous system in vertebrates comprising, for the most
part, adrenergic neurons (nerve cells that secrete
norepinephrine
or epinephrine as neurotransmitters) located relatively distant
from target organs.
... ... *parasympathetic neurons: The parasympathetic nervous
system is a division of the autonomic nervous system comprising
cholinergic nerve cells clusters located near target organs.
... ... *apoptosis: Programmed cell death produced by control
mechanisms designed to destroy defective cells.
... ... *mitochondrial dysfunction: Mitochondria are organelles
of the cell cytoplasm, and they are the principal energy source
of the cell, containing various enzymes involved in electron
transport and metabolic cycles.
... ... *oxidative stress: In this context, the term "oxidative"
refers to oxidative metabolism, a set of biochemical pathways
dependent on the utilization of supplied oxygen.
... ... *excitotoxins: Toxins that bind to certain neuron
receptors and which may be involved in neuron cell death. Certain
amino acids (e.g., glutamic acid) can act as excitotoxins, and
their study has given rise to the "excitotoxicity hypothesis",
which proposes that the effects produced by these amino acids are
caused by a prolonged depolarization of receptive neurons, the
process leading somehow to the eventual damage or death of these
nerve cells.
... ... *neurotrophic support: In general, neurons in the central
nervous system apparently depend for their survival on a number
of secreted substances called neurotrophins (neurotrophic
factors).
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 6Nov98

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

Related Background:

IDENTIFICATION OF A GENE FOR JUVENILE PARKINSONISM
Parkinson's disease is a common neurodegenerative disease with
complex clinical features. Autosomal recessive juvenile
parkinsonism has been related to the long arm of chromosome 6 and
to several genetic markers. Kitada et al (9 authors at 4
installations, JP) now report the identification of the gene
related to autosomal recessive juvenile parkinsonism. The entire
gene spans more than 500 kilobases. Mutations in this newly
identified gene appear to be responsible for the pathogenesis of
the disease, and the authors have named the protein product
"parkin". The authors suggest the protein parkin is apparently
similar to the ubiquitin family of proteins, which are involved
in the pathogenesis of several neurodegenerative diseases and are
an evident component of certain molecular entities in Alzheimer's
disease. Further investigation is necessary to establish the
exact physiological function of Parkin and how the parkin gene
defects induce selective degeneration of specific neurons.
QY: Nobuyoshi Shimizu 
(Nature 9 Apr 98 392:605) (Science-Week 1 May 98)

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

Related Background:

DISCOVERY OF GENE IMPLICATED IN PARKINSON'S DISEASE
Defects in the structure of the protein alpha-synuclein have been
implicated in several human brain pathologies, including
Alzheimer's disease and Creutzfeld-Jacob disease. Now a specific
type of familial, early-onset Parkinson's disease has been added
to the list. Mihael H. Polymeropoulos (20 authors at various
installations, US, IT, GR) have identified a mutation in the
alpha-synuclein gene in three unrelated families of Greek origin
exhibiting inherited early-onset Parkinsonism. A consensus is
growing that defects in the structure of alpha-synuclein may be
responsible for an array of human brain pathologies, with at
least some of the protein structural defects caused by inherited
genetic mutations. Alpha-synuclein has been previously shown to
be a presynaptic nerve terminal protein. The early visible
symptoms of Parkinsonism are produced by destruction of nerve
cells producing the hormone dopamine. In later stages of the
disease, destruction of other types of nerve cells occurs. This
new study does not provide evidence for a genetic basis for all
cases of Parkinsonism, but it serves as a pointer for researchers
studying the molecular biology of the disease.
(Science 27 Jun 97) (Science-Week 3 Jul 97)


7. AGING, LIFESPAN, AND SENESCENCE
Our knowledge of the basis of senescence of cells, tissues, and
organisms (including humans) has entered a new phase in recent
decades because of the new vistas opened by molecular biology.
Model systems have started to provide insights, and one important
approach has been the identification of genes that determine the
lifespan of an organism. The very existence of genes that when
mutated can extend lifespan suggests to many researchers that one
or a few processes may be critical in aging, and that a slowing
of these processes may slow aging itself. ... ... In a short
review of current research in the molecular biology of aging and
lifespan, L. Guarente et al make the following points: 1) In the
budding yeast Saccharomyces cerevisiae, aging results from the
asymmetry of cell division, which produces a large mother cell
and a small daughter cell arising from the bud. Much of the
macromolecular composition of the daughter cell is newly
synthesized, whereas the composition of the mother cell grows
older with each cell division. It has been shown that mother
cells of this yeast species divide a relatively fixed number of
times, and exhibit a slowing of the cell cycle, cell enlargement,
and sterility. Analysis of *ribosomal DNA in old cells reveals an
accumulation of *extrachromosomal ribosomal DNA of discrete
sizes, apparently representing a cumulative fragmentation of
chromosomal ribosomal DNA. The authors suggest it will be of
great interest to assess the generality of this process as an
aging mechanism. 2) In *Caenorhabditis elegans (a *nematode worm;
see notes), the *neurosecretory system regulates whether animals
enter the reproductive life cycle or arrest development at a
primitive *diapause stage. Developmental arrest is apparently
induced by a *pheromone and involves behavioral and morphological
changes in many tissues of the animal, with the lifespan becoming
4 to 8 times longer than that of the normal 3-week lifespan of
fully developed animals. Declines in pheromone concentration
induce recovery to reproductive adults with normal metabolism and
lifespan. Genes that regulate the function of the C. elegans
diapause and the neuroendocrine aging pathway have been
identified, and at least one of these genes codes for an
*insulin-like receptor apparently involved in metabolism. The
authors suggest that if the association of longevity and diapause
is general, it is possible that *polymorphisms in the human
insulin receptor-signaling pathway genes and related gene
*homologues may underlie genetic variation in human longevity. 3)
In plants, there is a large range of lifespans in the various
plant kingdoms. Certain tree species live for well over a
century, whereas other plants complete their life cycle in a few
weeks. The "yellowing" of leaves is often referred to in the
plant literature as leaf senescence or the "senescence syndrome"
-- referring to the process by which nutrients are mobilized from
the dying leaf to other parts of the plant to support their
growth. The senescence syndrome is characterized by distinct
cellular and molecular changes, with the chloroplast the first
part of the cell to undergo disassembly (producing the
"yellowing"). In many plant species, certain hormones can either
enhance or delay senescence. Although the genes that are
expressed during the plant senescence syndrome (as well as ways
to manipulate such senescence) have been identified, much remains
to be done to understand the molecular basis of aging in plants.
For example, nothing is known about the signal transduction
pathways that lead to altered gene expression during senescence,
or how plant hormones such as *cytokinin influence senescence.
But there are now many tools to explore this process. The authors
conclude: "It remains to be seen whether common mechanisms link
the aging process in diverse organisms."
-----------
L. Guarente et al (3 authors at 3 installations, US)
Aging, lifespan, and senescence.
(Proc. Natl. Acad. Sci. US 15 Sep 98 95:11034)
QY: Leonard Guarente, Mass. Inst. of Technology 617-253-1000.
-----------

Text Notes:
... ... *ribosomal DNA: A ribosome (not to be confused with
riboZYME) is a small particle, a complex of various ribonucleic
acid component subunits and proteins that functions as the site
of protein synthesis. The term "ribosomal DNA" refers to the gene
or genes that code for the RNA in ribosomes. In other words, the
term "ribosomal DNA" does not refer to any DNA in ribosomes
(there is no DNA in ribosomes).
... ... *extrachromosomal: In general, this refers to anything
outside of chromosomes, and in this case to DNA fragments
unincorporated into chromosomal DNA.
... ... *Caenorhabditis elegans: This is a small (1 mm) nematode
worm. It is transparent, hermaphroditic, free-living, and found
in soil. It has a relatively small genome (approximately 19,000
genes), and only a few types of cells in its body. It has a 16-hr
embryogenesis that can be achieved in a petri dish, and is thus
highly suitable for the study of developmental and behavioral
genetics.
... ... *nematode: An abundant and ubiquitous phylum of
unsegmented roundworms.
... ... *neurosecretory system: In general, all neural systems
contain both neurons that themselves secrete chemical messengers
and neurons that signal special secretory cells to secrete
chemical messengers. A neurosecretory pathway is a delineated
signaling system that involves such a resultant secretion.
... ... *diapause: In general, this refers to any programmed
period of suspended development in invertebrates. 
... ... *pheromone: In general, a chemical substance which, when
released into an animal's surroundings, influences the
development or behavior of other individuals of the same species.
... ... *insulin: A protein hormone that promotes uptake by body
cells of free glucose and/or amino acids, depending on target
cell type.
... ... *polymorphisms: A genetic polymorphism is a naturally
occurring variation in the normal nucleotide sequence of the
genome within individuals in a population. Variations are denoted
as polymorphisms only if they cannot be accounted for by
recurrent mutation and occur with a frequency of at least about 1
percent.
... ... *homologues: In general, the term "homologous" means
having the same structure. But the term has special uses in
genetics and evolution biology.
... ... *cytokinin: A group of plant growth substances. They are
chemically identified as derivatives of the purine base adenine.
They stimulate cell division and determine the course of
differentiation. They work synergistically with other plant
hormones called "auxins".
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 6Nov98

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

Related Background:

CELLULAR AGING: DONOR AGE AND CELLULAR REPLICATION LIFESPAN
Fibroblasts are a type of connective tissue cell, secreting
structural proteins such as collagen, the proteins forming a
matrix in which the fibroblasts become embedded. These cells can
be easily obtained from skin, and they can be easily cultured
outside the body. Normal human fibroblasts have a finite
replicative lifespan in vitro (i.e., they divide a finite number
of times), and this has been postulated to be a cellular
manifestation of aging of the human organism. Several studies
have indeed shown an inverse relationship between donor age (the
age of the persons from which cultured cells are derived) and
fibroblast culture replicative lifespan. But in all cases the
correlation was weak, and with few exceptions the health status
of the donors was unknown. Thus, the relationship between the
replicative lifespan and the age of the donor from which the
cells are derived has remained equivocal (*Note #1).
... ... V.J. Cristofalo et al now report a study of the
replicative lifespan of 124 skin fibroblast cell lines
established from donors of different ages. All donors were
medically examined and were declared "healthy" (according to
Baltimore Longitudinal Study of Aging protocols) at the time the
biopsies were taken. The authors report that both long- and
short-lived cell lines were observed in all age groups, but no
significant correlation between the proliferative potential of
the cell lines and donor age was found. A comparison of multiple
cell lines established from the same donors at different ages
also failed to reveal any significant trends between
proliferative potential and donor age. The authors suggest their
results clearly indicate that if health status and biopsy
conditions are controlled, the replicative lifespan of
fibroblasts in culture does not correlate with donor age.
-----------
V.J. Cristofalo et al (5 authors at 2 installations, US)
Relationship between donor age and the replicative lifespan of
human cells in culture: A reevaluation.
(Proc. Natl. Acad. Sci. US 1 Sep 98 95:10614)
QY: Vincent J. Cristofalo, Center for Gerontological Research,
Alleghany University of the Health Sciences, Philadelphia, PA
19129 US.
-------------------
... ... *Note #1: The possibility that the process of cell aging
and death is under genetic control was first suggested by Leonard
Hayflick in 1961. Hayflick reported that normal human fibroblasts
apparently have an intrinsic limit to the number of times they
can proliferate, with human fibroblasts removed from an embryo
and grown in culture dividing approximately 50 times before they
deteriorate and die. In contrast, human fibroblasts removed from
adults multiply only 15 to 30 times before dying. Also,
fibroblasts removed from young children suffering from Werner's
syndrome (a rare disease that causes premature aging) divide only
2 to 10 times in culture. Further evidence for a relationship
between aging and the replicative capacity of cells was provided
by the discovery that the number of replications in culture is
apparently related to the lifespan of organism. For example,
cultured cells of the Galapagos tortoise, whose maximum life span
is approximately 175 years, divide more than 100 times in
culture, whereas cells from the mouse, whose maximum life
expectancy is only a few years, divide fewer than 30 times in
culture. The correlation roughly holds for other species as well.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 16Oct98

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

Related Background:

BIOLOGY OF AGING: ON TELOMERES AND REPLICATIVE SENESCENCE
Telomeres are defined ends of chromosomes that contain specific
repeated DNA sequences. They are essential for normal chromosome
replication, and since their length shortens a bit with each
replication, they are believed to be involved in the aging of the
cell. Telomerase is an enzyme that repairs damage to telomeres,
and it is thought by some that cancerous cells may have mutant
telomerase, the mutant enzyme conferring immortality on the
cancer cell. ... ... In a review of cell senescence, the aging of
cell cultures, and the immortalization of mammalian cells, John
M. Sedivy (Brown University, US) makes the following points: 1)
Finite replicative lifespan (senescence) of mammalian cells in
culture is a phenomenon that has generated much curiosity since
its description. The obvious significance of senescence to
organismal aging and the development of cancer has engendered a
long-lasting and lively debate about its mechanisms. 2) Three
classical observations are usually cited to argue that in vitro
replicative senescence is a phenomenon with biological
significance: a) the correlation of in vitro lifespan with the
age of the donor; b) the correlation of in vitro lifespan with
the average life expectancy of species; and, c) the reduced in
vitro lifespan of cells from patients afflicted with premature
aging syndromes. 3) Two major theories have been used to explain
limited replicative capacity. The first hypothesis invokes the
gradual accumulation of mutations, and the second hypothesis
invokes the existence of a molecular clock (or clocks) that can
keep track of cell divisions. The second theory is now believed
to be generally true. 4) It is known that cell senescence can be
overcome, because many cell lines in common laboratory use are
quite obviously immortal. Rodent cells can overcome senescence
spontaneously. Human, chicken, bovine, and horse cells rarely, if
ever, immortalize spontaneously. 5) Certain viral or biochemical
interventions in human cell cultures can overcome cell
senescence, typically by causing 20 to 30 extra population
doublings. At the end of this extended lifespan, there is a
decline and death of the culture in 4 to 6 weeks, which has been
termed "crisis". Senescent cells, on the other hand, can be
maintained in vitro in a viable non-proliferative state for very
long periods of time (reports of from 4 to 6 months, and up to 2
years). 6) The author suggests it is amazing that in spite of
very long periods of apparent "immortality", the senescent
program in cells remains intact in cells in which senescence has
been overridden, so that on removal of the overriding agent, the
program is capable of establishing rapid growth arrest. 7) The
current prevailing hypothesis for the nature of the molecular
clock involved in cell senescence is the attrition of telomeres.
*Germ cells, and some key *stem cells, are known to express
telomerase catalytic activity, whereas the majority of somatic
cells lack it. Murine (mouse) embryonic stem cells express
telomerase and are functionally immortal, and elimination of
telomerase eventually results in loss of proliferation. 8) The
author proposes that immortalization of human cells requires a
bypass of both cell senescence and crisis, whereas in rodent
cells cell crisis does not exist and culture lifespan is limited
only by senescence. 9) Evidence indicates that, at least in human
cells, telomere length appears to be linked critically to the
triggering of senescence. The author suggests that although it
remains to be rigorously demonstrated, this strongly implies that
activation of telomerase can result in one-step immortalization.
In conclusion, the author states the two most significant
questions in this field: a) Does cell senescence limit organismal
lifespan? And, b) Is telomerase expression necessary for cancer
progression in vivo?
QY: John M. Sedivy 
(Proc. Natl. Acad. Sci. US 4 Aug 98 95:9078)
(Science-Week 4 Sep 98)

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

Related Background:

... ... *Germ cells: Any cell from which gametes (sperm cells and
egg cells) are derived. All other cells are called "somatic"
cells.
... ... *stem cells: In general, a stem cell is any precursor
cell, a form prior to cell differentiation. E.g., stem cells in
bone marrow that give rise to blood cells.


8. AN EVALUATION OF CHIROPRACTIC AND MCKENZIE TREATMENTS
In theory, "chiropractic" is a therapeutic system that uses the
recuperative powers of the body and the relationship between the
musculoskeletal structures and functions of the body,
particularly as they involve the spinal column and the nervous
system, in the restoration and maintenance of health. The most
common method of chiropractic manipulation is a short lever,
high-velocity thrust directed specifically at a "manipulable
lesion". This procedure is typically performed with the patient
lying on his or her side on a segmental table. In the US, many
individuals are licensed and certified to practice chiropractic.
There is also extant in the US the "McKenzie method of physical
therapy", in which patients are placed in one of 3 broad
categories ("derangement", "dysfunction", and "postural"
syndromes) that determine therapy. In this formulation, most
back, buttock, and leg pain is considered to result from a
derangement syndrome treated by exercises that "centralize" pain
from the feet, legs, or buttocks to the lower back. Patients are
taught to perform exercises that centralize their symptoms and to
avoid movements that peripheralize them. The McKenzie method
relies on patient-generated forces and emphasizes self-care. In
the literature at the present time, there are few data on the
relative effectiveness and costs of various treatments for low
back pain. ... ... D.C. Cherkin et al now report a study
involving random assignment of 321 adults with low back pain that
persisted for 7 days after a primary care clinic visit, the
subjects assigned to a McKenzie group, a chiropractic group, and
to a minimal intervention group that only received an educational
booklet. All McKenzie physical therapy and chiropractic patients
were treated by certified practitioners of those methods for 1
month with as many as 8 visits per patient during that interval.
The study received the cooperation and assistance of local
McKenzie therapy and chiropractic professional groups. The
authors report that for patients with low back pain, the McKenzie
method of physical therapy and chiropractic manipulation had
similar effects and costs, and that patients receiving these
treatments had only marginally better outcomes than those
receiving the minimal intervention of an educational booklet. The
mean costs of treatment (Seattle, US) were US$238 per patient for
the physical therapy group, US$226 per patient for the
chiropractic group, and US$1 per patient for the booklet group.
The authors suggest that whether the limited benefits of the
McKenzie and chiropractic treatments are worth the additional
costs is open to question.
-----------
D.C. Cherkin et al (5 authors at 2 installations, US CA)
A comparison of physical therapy, chiropractic manipulation, and
provision of an educational booklet for the treatment of patients
with low back pain.
(New England J. Med. 8 Oct 98 339:1021)
QY: Daniel C. Cherkin, Univ. of Washington Seattle 206-543-8992.
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 6Nov98