ScienceWeek

SCIENCE-WEEK

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A journal devoted to the improvement of communication
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science educators, and science policy makers.

October 1, 1999 -- Vol. 3 Number 40

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What is the path? There is no path.
-- Niels Bohr (1885-1962)

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Contents of This Issue:

1. On Educating Physicians Concerning Tobacco Dependence
2. On the Biological Substrates of Memory Formation
3. Microbiology: On Antibiotics and Selman Waksman
4. A Radio Pulsar that Challenges Emission Models
5. First Discovery of an Asteroid Water Inclusion
6. On Global Climate Change

In Focus: On Big Science and Little Science

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

1. ON EDUCATING PHYSICIANS CONCERNING TOBACCO DEPENDENCE
Tobacco use is the leading cause of preventable death and
disability in the US, accounting for nearly 500,000 premature
deaths per year. Although 70 percent of smokers visit a physician
each year, most patients are not advised or assisted in an
attempt to quit smoking. A 1991 survey indicated that only 21
percent of practicing physicians felt their formal medical
training prepared them to help patients stop smoking.
... ... L.H. Ferry et al (3 authors at Loma Linda University, US)
now present the results of a survey designed to assess the
content and extent of tobacco curricula in US undergraduate
medical education. In this context, the phrase "tobacco
curricula" includes epidemiology of tobacco use, prevention, risk
of tobacco-related diseases, and tobacco dependence treatment.
The phrase "smoking cessation" includes behavior modification
techniques, pharmacotherapy, and counseling skills. The authors
received data from 122 US medical schools (98.6 percent of the
total medical schools in the US). The authors report that a
majority of US medical school graduates are not adequately
trained to treat nicotine dependence. The authors suggest that
the major deficit is the lack of smoking cessation instruction
and evaluation in the clinical years of medical training, and
that a model core tobacco curricula that meets national
recommendations should be developed and implemented in all US
medical schools. The authors conclude: "Until all medical schools
place sufficient emphasis on the knowledge base and intervention
skills needed to prevent and treat chronic tobacco-related
diseases, it is unlikely we will see a decline in tobacco-related
morbidity and mortality. However, if medical schools provide
universal training of medical students in nicotine dependence
intervention, tobacco users will have access to the professional
expertise they need to end the deadly cycle of nicotine
addiction."
-----------
L.H. Ferry et al: Tobacco dependence curricula in US
undergraduate medical education.
(J. Amer. Med. Assoc. 1 Sep 99 282:825)
QY: Linda Hyder Ferry [lferry@sph.llu.edu]
-------------------
Summary by SCIENCE-WEEK [http://scienceweek.com] 1Oct99
-------------------
Related Background:
ON THE TOBACCO INDUSTRY AND NICOTINE AS AN ADDICTIVE DRUG
In 1994 the state of Minnesota filed suit against the tobacco
industry, and although this trial is now history, there are many
people who feel the legacy of the trial will carry on into the
21st century because of the revelations contained in the millions
of pages of previously secret internal tobacco industry documents
made public in the trial. ... ... R.D. Hurt and C.R. Robertson
now present an extensive review of the material in a medical
journal from the perspective of medical science, and the authors
make the following points: 1) The litigation tobacco industry
documents reveal that for decades the tobacco industry knew and
internally acknowledged that *nicotine is an addictive drug and
that cigarettes are the ultimate nicotine delivery device. The
following statements by executives, for example, are found in
tobacco industry documents: "Very few consumers are aware of the
effects of nicotine, i.e., its addictive nature and that nicotine
is a poison." (H.D. Steele, Brown and Williamson Tobacco Company,
1978). And in another Brown and Williamson memo: "Nicotine is the
addicting agent in cigarettes." (A.J. Mellman, Brown and
Williamson Tobacco Company, 1983). Concerning cigarettes as a
drug delivery device, the litigation documents reveal that C.E.
Teague Jr., assistant director of research at R.J. Reynolds
Tobacco Company, wrote in 1972 in an internal memorandum: "In a
sense, the tobacco industry may be thought of as being a
specialized, highly ritualized and stylized segment of the
pharmaceutical industry. Tobacco products, uniquely, contain and
deliver nicotine, a potent drug with a variety of physiological
effects... Thus a tobacco product is, in essence, a vehicle for
delivery of nicotine." 2) The authors report that perhaps their
most surprising finding in the document review was the evidence
of tobacco industry efforts spanning 3 decades to alter the
chemical form of nicotine to increase the percentage of freebase
nicotine delivered to smokers. Depending on pH, nicotine exists
as a diprotonated salt, a monoprotonated salt, or an uncharged 
neutral species. The salt forms are called the "bound" forms, and
the neutral species is called the "freebase" form. Nicotine
favors the salt form at low values of pH (e.g., pH = 3) and the
freebase form at high values of pH (e.g., pH = 8). Freebase
nicotine apparently crosses biological membranes more easily than
the charged counterparts, and this affects the physiological
response to the drug. The tobacco industry was apparently well
aware of these properties of nicotine as far back as 1966, and
for 3 decades the tobacco industry had a focus on developing high
pH delivery of nicotine to increase its physiological effects.
The authors conclude: "When the breadth and depth of tobacco
industry actions are understood, it becomes evident that allowing
a tobacco settlement that honors the industry demands for legal
and financial immunity would be a public health disaster of epic
proportions and would allow the industry to continue to promote
its deadly product throughout the 21st century. Congress must use
its power to stop the carnage of more than 400,000 Americans
dying each year of cigarette-related diseases."
-----------
R.D. Hurt and C.R. Robertson (2 installations, US)
Prying open the door to the tobacco industry's secrets about
nicotine.
(J. Amer. Med. Assoc. 7 Oct 1998 280:1173)
QY: Richard D. Hurt, Mayo Clinic, 200 First St. SW, Rochester, MN
55905 US.
-----------
Text Notes:
... ... *nicotine: The alkaloid nicotine
[3-(1-methyl-pyrrolidyl)pyridine] is a tertiary amine composed of
pyridine and pyrrolidine rings. The current consensus among
neuropharmacologists is that nicotine is the psychoactive drug
primarily responsible for the addictive nature of tobacco use. 
Nicotine is highly selective for so-called "nicotinic receptors"
for *acetylcholine in the peripheral and central nervous systems,
and activation of these receptors is the likely source of the
psychoactive effects of the drug. The nicotinic-acetylcholine
receptor is a molecularly well-characterized receptor, and its
activation evidently leads to conformation changes in its 5
subunits that result in a transient increase of permeability of
the neuron membrane to the sodium ion. The nicotinic-
acetylcholine receptor is therefore characterized as a
neurotransmitter-gated ion channel. Concentrations of nicotine in
blood rise quickly during cigarette smoking and peak at its
completion. Nicotine is also deposited in the lungs, spleen,
liver, and brain, where concentrations are typically twice those
of measurable blood concentrations. Nicotine readily crosses the
*blood-brain barrier, leading to the release of acetylcholine,
*norepinephrine, *dopamine, *serotonin, *vasopressin, *growth
hormone, *cortisol, *prolactin, *neurophysin 1, and
*adrenocorticotropic hormone, and release of these substances
causes various neuropharmacological effects. Apart from the
neuropharmacological effects of nicotine, nicotine and other
constituents in cigarette smoke elevate blood pressure, cause
*tachycardia, *arrhythmia, and *vasoconstriction in *cutaneous
tissue and skin; lower body temperature; inhibit *diuresis;
increase *gastrointestinal tonus; antagonize ulcer healing; and
decrease pain threshold.
... ... *acetylcholine: A prevalent *neurotransmitter substance,
both in the brain and in the peripheral nervous system, where it
controls the actions of skeletal and smooth muscle.
... ... *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.
... ... *blood-brain barrier: A selective mechanism opposing the
passage of most ions and large molecular-weight compounds from
the blood to brain tissue, the mechanism operating in a
continuous layer of endothelial cells connected by tight
junctions between cells. (Endothelial cells are flat cells
forming a layer lining blood vessels, lymphatic vessels, the
heart, etc.)
... ... *norepinephrine: The principal neurotransmitter substance
released from nerve endings of the sympathetic nervous system.
(The sympathetic nervous system is a part of the autonomic
nervous system involved in the mobilization of energy resources
during stress and arousal.
... ... *dopamine: A neurotransmitter substance.
... ... *serotonin: A neurotransmitter substance involved in
nearly everything occurring in the brain, including psychological
states such as anxiety and depression, and dysfunctions producing
migraine and epilepsy.
... ... *vasopressin: A peptide hormone important in the
regulation of *diuresis.
... ... *growth hormone: A vertebrate polypeptide hormone that
regulates growth. In general, hormones are signaling molecules
secreted into the blood stream by endocrine cells and acting on
target cells that possess receptors for the hormone.
... ... *cortisol: A corticosteroid hormone secreted by the
adrenal gland.
... ... *prolactin: A polypeptide hormone synthesized and
released by the pituitary gland.
... ... *neurophysin 1: Neurophysins are a family of proteins
synthesized in the hypothalamus, and function as carriers in the
transport and storage of a number of hypothalamic-pituitary
hormones.
... ... *adrenocorticotropic hormone: (ACTH) A pituitary hormone.
... ... *tachycardia: Rapid beating of the heart, conventionally
applied to rates over 100 per minute.
... ... *arrhythmia: Irregularity of the heartbeat.
... ... *vasoconstriction: Narrowing of the blood vessels.
... ... *cutaneous tissue: In general, tissue associated with
skin.
... ... *diuresis: Excretion of large volumes of urine.
... ... *gastrointestinal tonus: In general, contraction of
gastrointestinal muscle.
-------------------
Summary & Notes by SCIENCE-WEEK  13Nov98
-------------------
Related Background:
EFFECTS OF NICOTINE ON BRAIN NERVE CELLS
... Dopamine is a neurotransmitter found in several major areas
of the brain, and the degeneration of so-called dopamine neurons
is apparently involved in Parkinson's disease. Dopamine has also
been implicated in the intricate effects of the psychostimulating
drugs associated with drug abuse. The dietary precursors of
dopamine are phenylalanine and l-tyrosine. The mesolimbic
dopamine system is a dopamine-involved system of nerve cells and
nerve fibers connecting the mesencephalon (the midbrain) to the
limbic system and cerebral cortex.
... ... Pidoplichko et al (4 authors at 2 installations, US)
report that the same concentration of nicotine achieved by
smokers activates and desensitizes multiple nicotinic receptors
with a resultant regulation of the activity of dopamine neurons.
The authors suggest these results further support the hypothesis
that the mesolimbic dopamine system is involved in the cellular
and behavioral effects of many addictive drugs.
QY: John A. Dani 
(Nature 27 Nov 97) (Science-Week 19 Dec 97)
-------------------
Related Background:
SECOND-HAND TOBACCO SMOKE DOUBLES RISK OF CORONARY PATHOLOGY
The most significant public health news of the week was probably
the report of a 10 year study by Ichiro Kawachi and colleagues
(Harvard School of Public Health, Cambridge MA US), which
tracked more than 32,000 healthy women who never smoked and
found that regular exposure to the smoke of other people at home
or work almost doubled the risk of heart disease. These new
findings are the largest increase in risk ever reported for
second-hand smoke, and the researchers state the findings apply
equally to men and women.
(Circulation 20 May 97) (Science-Week 22 May 97)


2. ON THE BIOLOGICAL SUBSTRATES OF MEMORY FORMATION
The capacity of the nervous system to change (often referred to
as neural or brain "plasticity") is particularly prominent during
development, but the ability to learn new skills and establish
new memories clearly continues throughout life. The central
question is simply stated: How does the adult nervous system
mediate such changes? An understanding of the mechanisms
responsible for learning and other plastic changes in the adult
brain continues to be one of the most important challenges of
neuroscience, with a great deal of devoted research effort in
many laboratories in a number of associated disciplines. At the
present time, after nearly a century of research, there is a
consensus among investigators that the mechanisms of memory
formation involve carefully regulated changes in the strength of
existing connections between nerve cells (*synapses). Experiments
carried out in a variety of animals have demonstrated that
synaptic strength can be altered over periods ranging from
milliseconds to months, and that the cellular mechanisms
underlying these changes are transient modifications of the
transmission of activity from one nerve cell to another
(*neurotransmission) and, in the case of longer-lasting
alterations, changes in *gene expression.
... ... Jerry Chi-Ping Yin (Cold Spring Harbor Laboratories, US)
presents a review of current research on the localization of
memory functions, the author making the following points:
     1) Concerning investigations of memory localization at the
anatomical/systems level, Karl Lashley (1890-1958) used
anatomical lesions in the rat brain to search for the memory
"engram", the physical locus of long-term memory. Over a 30-year
period, Lashley performed surgical removal ("ablations") of
various regions in the rat *cerebral cortex, and came to the
disappointing view that no single well-defined lesion could
totally disrupt learning and memory formation [*Note #1]. This
resulted in the general hypothesis that memories are distributed
throughout the brain. Beginning in the late 1930s, however,
Wilder Penfield (1891-1976), in the course of neurosurgical
procedures for the treatment of human epilepsy, electrically
stimulated the temporal cortex of patients and caused them to
experience extremely vivid "memories" [*Note #2]. These
observations led Penfield to conclude that memories are
localized. Recent studies using non-invasive brain imaging,
coupled with refined animal ablation studies, have led to the
contemporary view that interacting widely distributed networks of
neurons participate in memory formation. A complication is the
apparent existence of functional redundancy ("backup" circuits)
and the possibility that different anatomical regions may be used
at different times after memory formation.
     2) Concerning investigations of memory localization at the
cellular level, neurophysiologists during the second half of this
century have developed a conceptual framework involving activity
dependent strengthening of neuronal connections. The search for
the loci of memory formation has become reduced to a search for
mechanisms that strengthen synaptic connectivity. The current
favorite cellular model for learning and memory formation is
"long-term potentiation", a physiological description of
increased synaptic efficacy following high-frequency stimulation.
A continuing controversy is whether the primary locus of changes
is on the pre- or post-synaptic side of the synapse. Proponents
of presynaptic change suggest that potentiation results from
changes in the amount of *transmitter release through one of many
possible mechanisms. Advocates of postsynaptic change propose
alterations in the efficiency of *receptor activation, perhaps
modulated through the "unmasking" of silent synapses.
     3) Concerning investigations of memory localization at the
molecular level, recent insights have been made into key
molecules whose activity apparently affects the process of memory
formation. These studies highlight two different uses of the term
"location": a) the various subcellular compartments where
important molecular entities are located; b) the changes in
specific protein amino-acid-residues produced by *post-
translational modification. In both cases, the activity and
interactions of important proteins are involved. At the present
time, there are at least 4 major *kinase systems believed to be
involved in memory formation: a) the *cyclic-AMP (cAMP)-dependent
protein kinase (protein kinase A); b) the *calcium-calmodulin
kinases; c) the *protein kinase C family; and d) the *mitogen-
activated protein (MAP) kinase pathway. The subcellular
localization of these kinases are apparently all regulated
through interactions with other proteins.
     4) The author suggests that the experimental results
gathered from different levels of analysis of learning and memory
formation can be integrated through the use of molecular
"reporters" -- molecular tags that allow monitoring of the
activity of important proteins and other molecular entities. For
example, a large amount of data collected from *Drosophila,
*Aplysia, the mouse, and the rat, have demonstrated the
importance of the *transcription factor cAMP-response-element-
binding protein (CREB) (and possibly its related family members)
in the process of consolidating long-lasting plastic changes.
CREB acts by binding to DNA sequences. This body of data,
collected from experiments involving a variety of behavioral
tasks and models of plasticity, supports the hypothesis that
learning-induced changes in gene transcription, at least
partially initiated through the activation of CREB family
members, are critical in the process of long-lasting changes in
plasticity.
-----------
Jerry Chi-Ping Yin: Location, location, location: The many
addresses of memory formation.
(Proc. Natl. Acad. Sci. US 31 Aug 99 96:9985)
QY: Jerry Chi-Ping Yin, Cold Spring Harbor Laboratory, Cold
Spring Harbor, NY 11724-2213.
-----------
Text Notes:
... ... *synapses: In general, nerve cells have a single long
extension (the "axon") that propagates the electrical output (the
action potential) of the cell. The term "synapse" refers to the
junction between the terminal of a neuron's axon and another
neuron. When studying the synapse, the first neuron is called the
"presynaptic" neuron, and the second neuron is called the
"postsynaptic" neuron.
... ... *neurotransmission: The term "neurotransmission" refers
to all the events at a synapse, particularly the release of
"neurotransmitters" and their action on the postsynaptic neuron.
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.
... ... *gene expression: In general, the term "gene expression"
includes any gene activity, but particularly an activity that
produces the synthesis or activation of a specific protein.
... ... *cerebral cortex: (cortex) The cerebral cortex is a thin
surface layering of nerve cells of the brain, the region only
several millimeters thick but covering all of the brain surface.
This is the part of the central nervous system most intimately
involved with the so-called "higher faculties", although the
cortex operates in concert with other parts of the brain. The
structure is primitive in lower mammals, and is found
progressively more pronounced and with greater surface area in
primates and man.
... ... *Note #1: Lashley's failure to localize memory in a
specific region of the mammalian cerebral cortex was one of the
great puzzles of the middle part of the 20th century. In 1950,
Lashley wrote: "This series of experiments... has discovered
nothing directly of the real nature of the engram. I sometimes
feel, in reviewing the evidence on the localization of the memory
trace, that the necessary conclusion is that learning just is not
possible."
... ... *Note #2: The observations that came out of Penfield's
surgery and laboratory at McGill University had dramatic
theoretical consequences in psychology and neurobiology.
Penfield, a neurosurgeon with training in physiology who
specialized in therapeutic surgery in the treatment of certain
forms of epilepsy, used electrical currents to stimulate the
surface of the brain. The therapeutic objective was to make a
brain map for that particular patient prior to deciding exactly
which damaged parts of the brain could be safely removed without
producing problems more severe than the epileptic condition. The
technique had been developed in 1909 by the neurosurgeon Harvey
Cushing. Penfield's research on the neurological basis of
language and long-term memory, much of it in collaboration with
Herbert Jasper and Lamar Roberts, revolutionized the concepts of
brain maps that existed in the 1950s.
... ... *transmitter release: (neurotransmitter release) See
above: "neurotransmission".
... ... *receptor activation: In this context, the term
"receptor" refers to postsynaptic membrane receptors.
... ... *post-translational modification: In this context,
translation is protein synthesis, the process during which
polypeptides are synthesized on ribosomes in accordance with RNA
code. The term "post-translational modification" refers to a
modification of protein that occurs after synthesis of that
protein, i.e., the modification is not a result of changes in the
DNA or RNA coding for that protein.
... ... *kinase: In general, a "kinase" is any enzyme involved in
the transfer of a phosphate group.
... ... *cyclic-AMP (cAMP): Cyclic adenosine monophosphate (cAMP)
is an important postsynaptic intracellular substance activated by
incoming synaptic activity, a "messenger" involved in various
aspects of cell regulation and protein synthesis.
... ... *calcium-calmodulin kinases: Calmodulin is a calcium-ion-
binding protein that mediates many of the regulatory effects of
calcium ions in eukaryotic cells (cells with organelles such as
nuclei). A "calcium-calmodulin kinase" is a kinase enzyme whose
activity is dependent on the presence of calcium-calmodulin.
... ... *protein kinase C family: (PKC family) Any of a family of
protein kinase enzymes that require anionic phospholipid for
activity and are regulated by diacylglycerol and calcium ion.
These enzymes phosphorylate hydroxyl groups in substrate serine
and threonine residues.
... ... *mitogen-activated protein (MAP) kinase: A family of
protein kinases that perform a crucial step in relaying signals
from the plasma membrane to the cell nucleus. They are activated
by a wide range of proliferation- or differentiation-inducing
signals. (A "mitogen" is any compound that stimulates mitotic
cell division.)
... ... *Drosophila: A fruit fly genus.
... ... *Aplysia: A large gastropod mollusk with readily
identifiable individual nerve cells in its central nervous
system. It has been used extensively in neurobiological research
since the 1960s. (The class "gastropods" contains the snails,
slugs, limpets, and conchs.)
... ... *transcription factor: "Transcription" is the process by
which the genetic information in DNA is converted into RNA, and
transcription factors are a class of DNA-binding proteins that
regulate RNA transcription.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 1Oct99


3. MICROBIOLOGY: ON ANTIBIOTICS AND SELMAN WAKSMAN
Drugs as chemical entities have been used for the treatment of
infectious diseases since the 17th century (e.g., *quinine for
malaria and *emetine for *amebiasis), but chemotherapy as a
science is considered to have begun with Paul Ehrlich (1854-1915)
in the first decade of the 20th century. Ehrlich formulated the
principles of selective toxicity and recognized the specific
chemical relationships between microbial pathogens and drugs, the
development of drug resistance, and the role of combined therapy.
Ehrlich's experiments led to the *arsphenamines for syphilis, the
first planned chemotherapy. The current era of antimicrobial
chemotherapy began in 1935 with the discovery of the
*sulfonamides. In 1940, *penicillin (discovered more than a
decade before in 1929) was demonstrated to be an effective
therapeutic substance, and during the next 25 years research on
chemotherapeutic agents for the most part focused on substances
of microbial origin called "antibiotics". The isolation,
concentration, purification, and mass production of penicillin
were followed by the development of *streptomycin, *tetracylines,
*chloramphenicol, and many other agents. These substances were
originally isolated from filtrates of media in which their
respective molds had grown. Since then others have been
synthesized, and in recent years biosynthetic modification of
specific molecules has been an important technique for the
discovery of new antimicrobial agents. One of the key researchers
in the development of antimicrobial agents in this century was
Selman Waksman (1888-1973), who developed the first antibiotic
(streptomycin) effective against human tuberculosis (and who
proposed the term "antibiotics"). Waksman received the Nobel
Prize in Physiology and Medicine in 1952. In a recent report, the
US Centers for Disease Control and Prevention presents a short
biographical essay on Selman Waksman, the report making the
following points:
     1) Selman Abraham Waksman grew up in the small Russian
village of Novoya Priluka. In 1910, he settled in New Jersey,
where a cousin operated a small farm. An interest in scientific
farming brought Waksman to the nearby Rutgers College of
Agriculture, where he earned a bachelor's degree in science in
1915 and a master's degree a year later. He completed his
doctorate at the University of California Berkeley in two years,
and returned to Rutgers to take a position as lecturer in soil
microbiology.
     2) Waksman preferred the term "microbiology" to the
conventional term "bacteriology" because "not the bacteria but
the *fungi and the *actinomycetes formed my major interests among
the microorganisms." By the 1930s, Waksman was a leading
researcher in microbiology, attracting talented graduate
students, including Rene Dubos (1901-1982), whose work led to the
discovery in 1939 of *gramicidin, the first clinically useful
*topical antibiotic.
     3) The success of Dubos and the introduction of penicillin
prompted Waksman to put his graduate students and assistants to
work looking for antibiotics. In 1943, a Waksman student, Albert
Schatz, isolated streptomycin. In 1944, clinical trials
demonstrated the effectiveness of streptomycin against *gram-
negative bacteria, including *Mycobacterium tuberculosis. Despite
substantial problems with toxicity and drug resistance,
streptomycin soon formed the foundation of multidrug therapies
for tuberculosis.
     4) With the introduction and use of antibiotics, mortality
of tuberculosis was reduced drastically. In the US, from 1945 to
1955, tuberculosis mortality decreased from 39.9 to 9.1 deaths
per 100,000 population. Around the world, tuberculosis remained a
substantial health problem, but in 1964 Waksman stated the
consensus opinion that "the final chapter of the battle against
tuberculosis appears to be at an end." That optimism is now
understood to have been premature: the recent emergence of
multidrug-resistant tuberculosis has alarmed microbiologists and
clinicians in all countries.
-----------
US Centers for Disease Control and Prevention: Selman Abraham
Waksman, PhD.
(CDC Morbidity and Mortality Weekly Report 1999 48:621)
(J. Amer. Med. Assoc. 15 Sep 99 282:1029)
QY: Cntrs. for Dis. Contrl. and Prev., Atlanta, GA 30333 US.
-----------
Text Notes:
... ... *quinine: C(sub20)H(sub24)N(sub2)O(sub2)3H(sub2)O. The
most important of the alkaloids derived from cinchona bark,
quinine is an anti-malarial effective only against certain forms
of the parasite. It is also used in the treatment of certain non-
malarial conditions. ("Cinchona" is a genus of South American
trees and shrubs.)
... ... *emetine: C(sub29)H(sub40)N(sub2)O(sub4). Cephaline
methyl ether. Emetine is the principal alkaloid of ipecac. Its
salts are used in the treatment of *amebiasis. "Ipecac" is a
South American "creeping" plant; emetine is derived from the
roots.
... ... *amebiasis: (amoebiasis) Infection with any of a variety
of pathogenic amoebas, particularly with Entamoeba histolytica.
... ... *arsphenamines: (arsphenamine = phenarsenamine)
3,3'-diamino-4,4'-dihydroxyarsenobenzene dihydrochloride.
Formerly used in the treatment of syphilis, yaws, and certain
other diseases of protozoan origin.
... ... *sulfonamides: ("sulfa drugs") A group of bacteriostatic
drugs containing the sulfonamide group (sulfanilamide,
sulfapyridine, sulfathiazole, sulfadiazine, and other
sulfanilamide derivatives. The sulfonamides inhibit the
utilization of an important metabolite (p-aminobenzoic acid) in
bacteria. A "bacteriostatic" agent is an agent that inhibits or
retards the growth of bacteria; a "bacteriocidal" agent is an
agent that kills bacteria.
... ... *penicillin: The penicillin antibiotics are
derived from molds of the genus Penicillium and obtained by
extraction of submerged cultures grown in special media. The most
widely used natural penicillin is Penicillin G. In general, with
6-aminopenicillanic acid as the fundamental chemical entity, an
almost unlimited variety of penicillin compounds can be
synthesized by coupling different radical carboxyl groups to the
free amino group.
... ... *streptomycin: A glucoside obtained from the mold
Streptomyces griseus. Active against the tuberculosis bacillus
and a large number of gram-positive and gram-negative (see below)
bacteria. It is used almost exclusively in the treatment of
tuberculosis.
... ... *tetracylines: A group of naphthacene derivatives
that are broad-spectrum antibiotics. The tetracyclines inhibit
protein synthesis in susceptible bacteria. (The term "broad-
spectrum" refers to activity against a wide range of
microorganisms.)
... ... *chloramphenicol: An antibiotic originally produced from
cultures of the mold Streptomyces venezuelae but now manufactured
synthetically. The drug is a potent inhibitor of protein
synthesis in microorganisms.
... ... *fungi: One of the phylogenetic "kingdoms" into which
life forms are divided for academic discussion. The organisms
develop from spores, have cell walls, and are non-motile. The
cells are eukaryotes (i.e., cells with internal membrane-bound
organelles such as a nucleus) and are devoid of chlorophyll or
other pigments capable of photosynthesis. Fungal organisms may
multicellular or unicellular, and many species are parasitic in
humans.
... ... *actinomycetes: This term refers to any members of the
genus Actinomyces, a group of slow-growing non-motile bacteria.
Most of the organisms produce a filamentous microcolony, and they
are pathogenic in humans.
... ... *gramicidin: One of a group of polypeptide antibiotics
produced by Bacillus brevis. They are primarily bacteriostatic in
action against certain gram-positive bacteria.
... ... *topical antibiotic: In this context, the term "topical"
refers to a local application (e.g., a region of skin).
... ... *gram-negative bacteria: Most bacteria can be classified
into two types, depending on the chemistry of their outer coat,
which chemistry determines whether a bacterium will admit certain
dyes into the interior. The classification, according to the
differential staining technique, is gram-negative vs.
gram-positive, named after the bacteriologist H.C. Gram
(1853-1938). Gram-positive bacteria take up a crystal violet
stain and turn purple, while gram-negative bacteria exclude the
crystal violet and counterstain instead with stains such as
safranin, eosin red, or brilliant green. As might be expected,
since the technique differentiates the outer coats of bacteria,
some antibiotics are effective against one type and not the other
type, and vice versa.
... ... *Mycobacterium tuberculosis: The mycobacteria (of which
there are more than 50 species) are rod-shaped aerobic bacteria
that do not form spores. The two chief mycobacteria human disease
pathogens are M. tuberculosis (which causes tuberculosis) and M.
leprae (which causes leprosy). The form of the tuberculosis
bacterium actually varies, since on artificial media spherical
and filamentous forms are seen, while in tissue the tubercle
bacilli are thin straight rods measuring approximately 0.4 x 3
microns. (An "aerobic" organism is an organism that can live and
grow in the presence of oxygen.)
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 1Oct99
-------------------
Related Background:
ANTI-TUBERCULOSIS DRUG RESISTANCE 1994-1997
In the past 50 years, the proliferation of anti-microbial agents
for use in humans and animals has placed enormous selective
pressure on microorganisms. Drug resistance in patients with
Mycobacterium tuberculosis infection became apparent soon after
the introduction of effective antituberculosis agents in the
1940s, but it was not until the early 1990s, when outbreaks of
multidrug-resistant tuberculosis were reported in patients with
human immunodeficiency virus (HIV) infection in the US and
Europe, that the problem received international attention.
... ... Pablos-Mendez et al (12 authors at 7 installations, US FR
CA NL KR and the World Health Organization) report a study of the
prevalence of resistance to 4 first-line drugs (isoniazid,
rifampin, ethambutol, streptomycin) in 35 countries participating
in an international collaborative study of the problem between
1994 and 1997. Among patients with no prior treatment, a median
of 9.9 percent of M. tuberculosis strains were resistant to at
least one drug. The prevalence of primary multidrug resistance
(resistance to at least isoniazid and rifampin) in this group was
1.4 percent. Among patients with histories of treatment for one
month or less, the prevalence of resistance to any of the four
drugs was 36 percent, and the prevalence of multidrug resistance
was 13 percent. Particularly high prevalences of multidrug
resistance were found in the former Soviet Union, Asia, the
Dominican Republic, and Argentina. The authors conclude that
resistance to antituberculosis drugs exists in all 35 countries
and regions surveyed, and they suggest that it is a global
problem. In an editorial in the same issue of the journal, D.E.
Snider and K.G. Castro (Centers for Disease Control, US) warn
that a greater commitment by the developed countries is needed
"if we are to ward off what could become a global health
disaster."
QY: Ariel Pablos-Mendez, Columbia University (US) 212-854-1754.
QY: Dixie E. Snyder, Centers for Disease Control and Prevention,
Atlanta, GA 30333 US.
(New England J. Med. 4 Jun 98 338:1641,1689)
(Science-Week 26 Jun 98)
-------------------
Related Background:
ON THE PROBLEM OF MULTI-DRUG MICROBIAL RESISTANCE
S. Levy (Tufts University, US) reviews the problem of multi-drug
resistant microbes. Antibiotic resistance, initially a problem in
hospitals and developing countries, today affects the world at
large. Some strains of disease-causing bacteria in the US may now
be untreatable: the vancomycin-resistant enterococcus,
Mycobacterium tuberculosis, Pseudomonas aeruginosa, and
Acinetobacter baumanii. The author proposes 5 principles
underlying the problem: 1) Given sufficient time and drug use,
antibiotic resistance will emerge. 2) Resistance is progressive,
evolving from low levels through intermediate to high levels. 3)
Organisms that are resistant to one drug are likely to become
resistant to others. 4) Once resistance appears, it is likely to
decline slowly, if at all. 5) The use of antibiotics by one
person affects others in the extended as well as immediate
environment.
QY: Stuart B. Levy, Tufts Univ. School of Medicine 617-636-6639
(New England J. Med. 7 May 98 338:1377) (Science-Week 15 May 98)
-------------------
Related Background:
APPARENT IRREVERSIBILITY OF BACTERIAL ANTIBIOTIC RESISTANCE
At a recent meeting of the European Society for Evolutionary
Biology (Arnhem NL), several research groups have apparently
independently confirmed the unhappy news that bacteria that have
mutated to exhibit resistance to specific antibiotics do not
evolve susceptible strains when they are no longer exposed to
these antibiotics. Bruce Levin and Bassam Tomah (Emory Univers-
ity, US) report that 25% of bacteria sampled from infant diapers
are strains of E. coli still resistant to the antibiotic
streptomycin, which has been rarely used during the past 30
years. Richard Lenski (Michigan State University, US) has
independently shown that after 20,000 generations in the absence
of streptomycin, E. coli still carries the gene that confers
resistance to the antibiotic. The consensus is apparently that a
compensatory mutation has occurred, a mutation that compensates
for the loss of fitness produced by the gene that confers
antibiotic resistance, and which results in long-term survival of
the resistant strain. Levin suggests the same kind of
compensatory mutations "will almost certainly be found in other
resistant bacteria." The implication is that the evolutionary
development of bacterial resistance to antibiotics will not be
reversed by reducing the use of these antibiotics, which means
the effectiveness of these antibiotics is essentially
irreversibly lost.
QY: B. Levin, Emory Univ., Population Genetics (404) 727-5660.
(Science 24 Oct 97) (Science-Week 14 Nov 97)


4. A RADIO PULSAR THAT CHALLENGES EMISSION MODELS
*Black holes, neutron stars, and *white dwarf stars are perhaps
the three most exotic objects in the known Universe, the object
in each case the result of a gravitational collapse following
exhaustion of the fuel of a star ("star death"). According to
theory, which particular object results depends on the remnant
mass of a star following its final blow-off of gas and matter
[*Note #1]. If the remnant mass of a star is between 1.4 and 2 to
3 solar-masses, the star will collapse into a neutron star, a
body with a radius of 10 to 15 kilometers, with a core so dense
that its component protons and electrons have merged into
neutrons. The average density of a neutron star is 10^(15) grams
per cubic centimeter, and the weight of an object on the surface
of a neutron star would be 10^(11) its weight on the surface of
the Earth. Neutron stars apparently have an outer shell of iron,
but it is iron like no Earth iron, an iron of 4 orders of
magnitude greater density. Theory predicts that a neutron star
should rotate very rapidly, be extremely hot, and have an intense
magnetic field. "Radio pulsars" are apparently rotating neutron
stars that emit beams of radio waves from regions above their
magnetic poles, with the radio emission arising from the
acceleration of charged particles above the magnetic poles. As
the neutron star rotates, a beam of radio waves sweeps across the
Earth and a radio pulse is observed, much like the beam from a
lighthouse. The pulse periods of neutron stars can be measured to
an accuracy of approximately 1 part in 10^(10). Current theories
of the emission mechanism require continuous electron-*positron
pair production, with the potential responsible for accelerating
the particles inversely related to the spin period. According to
theory, production of electron-positron pairs will cease when the
potential drops below a threshold, and thus the models predict
that radio emission will cease when the pulsation period exceeds
a value that depends on the strength and configuration of the
magnetic field. For a number of years, this general scheme has
been the consensus view concerning pulsars, but new evidence has
now arrived which is in apparent serious conflict with current
ideas concerning pulsar dynamics.
... ... M.D. Young et al (3 authors at 3 installations, AU) now
report that the pulsar PSR J2144-3933, previously thought to have
a period of 2.84 seconds, actually has a period of 8.51 seconds,
which is by far the longest period of any known radio pulsar. The
authors point out that under the usual model assumptions this
slowly rotating pulsar should not be emitting a radio beam. The
authors suggest that either the model assumptions are wrong, or
current theories of radio emission must be revised. The authors
further point out that consideration of the luminosity parameters
of PSR J2144-3933 imply that we can observe only a very small
proportion of the total population of such objects in the Galaxy.
The authors conclude: "While extrapolation from the detection of
a single object is always uncertain (some would say foolhardy),
there is no reason to suppose that PSR J2144-3933 is unique. With
this caveat, this detection implies a Galactic population of
similar pulsars of the order of 10^(5), comparable to previous
estimates of the size of the total pulsar population [in our
Galaxy]."
-----------
M.D. Young et al: A radio pulsar with an 8.5-second period that
challenges emission models.
(Nature 26 Aug 99 400:848)
QY: M.D. Young [matthew@physics.uwa.edu.au]
-----------
Text Notes:
... ... *Black holes: See Note #1 below.
... ... *white dwarf stars: See Note #1 below.
... ... *Note #1: If the terminal stages of star death leave
a remnant star mass greater than 3 solar masses, the ultimate
gravitational collapse will produce a black hole, a relativistic
singularity. A black hole is a localized region of space from
which neither matter nor radiation can escape. The "trapping"
occurs because the requisite escape velocity, which can be
calculated from the relevant equations, exceeds the velocity of
light and is therefore unattainable. Another view of a black hole
is that it is a mass that has collapsed to such a small volume
that its gravity prevents the escape of all radiation. White
dwarf stars are approximately the size of Earth, but with a mass 
approximately that of the Sun. If the remnant mass after star-
death blow-off is less than 1.44 solar masses (the Chandrasekhar
limit for a star with no hydrogen content), the star collapses
into a white dwarf.
... ... *positron: The positron is the antiparticle of the
electron. It has a charge identical but opposite to that of the
electron, and a rest mass identical to that of the electron.
In general, antiparticles are homologs of elementary particles
but with opposite charge. Matter composed entirely of
antiparticles is called antimatter.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 1Oct99
-------------------
Related Background:
ON THE BIRTH AND LIFE OF NEUTRON STARS
In this century, astronomy and astrophysics have contributed
greatly to what might be called the "Hall of Wonders", the
gallery of real-world spellbinding objects. Perhaps the two most
outstanding contributions to this gallery are black holes and
neutron stars. Black holes, born of the death of super-massive
stars, are in this century the most spectacular astronomical
objects known; neutron stars, born of the death of merely massive
stars, are not far behind on any gauge of the extraordinary. A
neutron star is an extremely dense and compact star that has
undergone gravitational collapse to such an extent that much of
the material has been compressed into neutrons. Such stars were
theoretically postulated in the 1930s, but it was not until 1967
that their existence was actually confirmed by observations.
Neutron stars are believed to form when a massive star exhausts
its fuel and the mass of the stellar core remaining after a
consequent supernova explosion exceeds 1.4 solar masses (the
Chandrasekhar limit). With diameters of only 10 to 15 kilometers,
intense magnetic fields [e.g., 10^(8) tesla], and extremely rapid
spin (e.g., as much as 500-700 rotations per second), young
neutron stars are evidently responsible for various intrinsic
pulsation phenomena, and thus are called "pulsars". It is also
thought that gamma-ray bursts may have neutron star origins.
Models of the structure of neutron stars have been derived from
study of the sudden changes in pulsar spin rates ("glitches").
... ... Joshua N. Winn (Massachusetts Institute of Technology,
US) presents a review of current research on neutron stars, the
author making the following points:
     1) Perhaps one problem with the "jaw-dropping" statistics
concerning pulsars is that the statistics are too extreme. Using
Earthly analogies, it is difficult to comprehend an entity with a
density of 10^(14) grams per cubic centimeter [*Note #1] in a
gravitational field that produces an acceleration of free fall
(g) 600 billion times that produced at the surface of Earth. It
is even more difficult to visualize such a dense city-size object
"as it spins furiously, squirting plasma (ionized gases) from
electric arcs near the poles of its inconceivable magnetic field
and swirling up a superfluid of neutrons in its interior." But
after 30 years of research, enough is known about pulsars to
reconstruct the outlines of their existences.
     2) The newborn neutron star, produced by a dead massive
star, possesses four salient characteristics: a) a fast rotation
rate, typically 50 times per second; b) a directed velocity in
excess of 1000 kilometers per second that may be caused by
violent asymmetry in the supernova explosion of the parent star;
c) extreme temperature due to the small radiative surface area
(e.g., temperatures of 100,000 to 1 million degrees kelvin; d) an
immense magnetic field, typically a million times stronger than
that of the Earth. (The author notes: "It is easier to write the
figure 10^(12) gauss than to ponder its zeros.")
     3) A spinning magnet generates voltages, as was demonstrated
by Michael Faraday in 1831, and a neutron star is a gargantuan
spinning magnet, the resultant voltage tearing electrons,
positrons, and ions from its surface and flinging them outward
into space along the magnetic field lines. This is the so-called
"pulsar wind", whose effects can observed in the turbulence of
gas clouds associated with supernova, the so-called "pulsar-wind
nebula."
     4) A second consequence of the intense magnetic field of the
spinning neutron star is the pulsation of the pulsar. The
magnetic poles of neutron stars emit narrow beams of radiation in
addition to the pulsar-wind, and since the magnetic axis is
offset from the spin axis, the beams execute an oscillation in
space observed from Earth as a pulsing of radiation. The
pulsation rate of neutron stars declines with their age, and the
pulse period (P) and the "spin-down rate" ("P-dot"; the time-
derivative of P) are at present the two most important
observables concerning pulsars. A plot or P-dot versus P of the
approximately 700 pulsars that have been identified has been
useful in research on these objects in the same way that the
*Hertzsprung-Russell diagram, plotting luminosity versus
temperature, has been useful in understanding the general
evolution of ordinary stars.
     5) Most pulsars slow down at a steady rate, but a few
pulsars exhibit slight and sudden "glitches" in their periods,
and these glitches have been used as the basis for studying the
structure of pulsars. It is presently believed that glitches
probably originate beneath the thin crust of a pulsar, in a dense
mantle of heavy nuclei permeated by a *superfluid of neutrons,
and that the *angular momentum of the superfluid is broken up
into discrete quantized vortices which migrate outward to the
crust as the neutron spin-rate decreases. It is believed the
migrations and surface eruptions of superfluid quantum vortices
(which transfer angular momentum to the crust) cause the sudden
changes in spin-rate which are observed as "glitches" in pulsar
behavior [*Note #2].
-----------
Editor's note: In addition to the background material below, see
the SW Focus Report "The Death of Stars" available at URL
[http://scienceweek.com/swfr002.htm]
-----------
Joshua N. Winn: The life of a neutron star.
(Sky & Telescope July 1999)
QY: Joshua N. Winn, Mass. Inst. of Technology 617-253-1000.
-----------
Text Notes:
... ... *Note #1: At such a density, the entire human species
could exist as an object the size of small marble -- with the
total mass of the entire human species retained: i.e., the marble
would weigh approximately 10^(14) grams.
... ... *Hertzsprung-Russell diagram: The Hertzsprung-Russell
diagram is a plot of stellar absolute magnitude against spectral
type (luminosity vs. temperature), and is one of the most useful
diagrammatic aids in astrophysics. The course of a star's
evolution can be traced as a particular path in the H-R diagram,
with the paths of various types of stars showing significant
differences.
... ... *superfluid: In general, a "superfluid" is a fluid that
flows without any resistance (i.e., zero viscosity).
... ... *angular momentum: The momentum of a body by virtue of
its rotation and/or orbital revolution. It is a conserved
quantity, and as a consequence a body spins faster as it becomes
smaller.
... ... *Note #2: Quantum vortices were discussed in the last
issue of SW (20 Aug 99 #34) in connection with the superfluid 
behavior of liquid helium-3. Here is the material from that issue
on quantum vortices: A quantum vortex is a type of flow pattern
exhibited by superfluids under certain experimental conditions,
e.g., liquid helium in a rotating container. The term "vortex"
designates the familiar whirlpool pattern where the fluid moves
circularly around a central line and the velocity decreases in
inverse proportion to the distance from the center. A superfluid
is considered to be characterized by a macroscopic
quantum-mechanical wave function that locks the superfluid into a
*coherent state. This forces certain mathematical constraints on
the wave function, so that for a superfluid in a rotating
container, the system (the wave equation for the system) produces
a lattice of quantized vortex lines, each line the axis of a
microscopic vortex, with the entire array of vortex lines
rotating rigidly with the container. The essential idea is that
when superfluid helium is in a rotating container, the
mathematics of the system wave function are such that a set of
discrete microscopic vortex states are produced by each
particular set of boundary conditions, and these microscopic
vortex states are experimentally observable [*Note #3]. In short,
the result is a system where the "quantum world" becomes visible
on a macroscopic scale.
... ... *coherent state: In quantum physics, coherence is matter
of locking of phase differences between wave functions. The wave
functions of two or more particles are said to be coherent if the
phase difference between their wave functions remains constant.
In general, a perfectly coherent system of particles can be
described by a single macroscopic wave function.
... ... *Note #3: Below a certain rotation speed threshold, no
vortices exist, and the superfluid remains at rest while the
container rotates (the Landau state). At the threshold speed, the
first vortex appears and corresponds to the first excited
rotational state of the system. If the container continues to
accelerate, additional quantized vortices appear, and at any
given speed the vortices form a regular array that rotates with
the vessel.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 27Aug99
-------------------
Related Background:
ON NEUTRON STARS
... ... L. Bildsten and T. Strohmayer (2 installations, US)
present a review of current research concerning neutron stars,
the authors making the following points: 1) With a density
comparable to that of an atomic nucleus, a neutron star provides
an extreme environment for fast and violent phenomena. Matter
orbiting a neutron star can have a period as short as a
millisecond. When such matter crashes into the star (i.e., is
"accreted" by the star), such matter can be moving at one-third
the speed of light. In general, because their behavior can vary
over readily observable timescales, neutron stars can be rich
sources of information about nuclear physics, general relativity,
and astrophysics. 2) Though relatively elusive, neutron stars
have been detected and studied over a broad range of
electromagnetic frequencies, from radio frequencies to *gamma
rays. To date, astronomers have identified more than 1000 of the
estimated 10^(8) neutron stars in our galaxy. New orbiting
astronomical satellites have produced recent rapid growth in our
knowledge of these objects, with much of the progress occurring
in our understanding of neutron stars that undergo sudden large
energy releases. 3) Although most neutron stars have been
discovered as radio pulsars, only a small fraction of the
radiated energy of a neutron star (typically approximately
10^(-5)) is expected to be radio emission energy. Most of the
energy instead departs as photons with energies above 10^(8)
*electronvolts. 4) The precise timing of radio pulsars has
yielded astonishing astronomical discoveries, such as multiple
Earth-mass planets orbiting a neutron star, and the direct
confirmation of the loss of orbital angular momentum due to
gravitational radiation in a double neutron star binary system
(for which Russell Hulse and Joseph Taylor received the 1993
Nobel Prize in Physics). 4) The brightest accreting neutron stars
reside in binary systems and accrete matter from their
companions. These accreting neutron stars typically have
luminosities more than a thousand times that of the Sun. 5) There
is every reason to believe that new classes of neutron stars will
be discovered by continued observations from the currently
orbiting satellites combined with the international fleet of new
x-ray and gamma-ray satellites planned for launch during the next
two years.
-----------
Editor's note: In addition to the background material below, see
the SW Focus Report "The Death of Stars" available at URL
[http://scienceweek.com/swfr002.htm]
-----------
L. Bildsten and T. Strohmayer: New views of neutron stars.
(Physics Today February 1999)
QY: Lars Bildsten, Univ. of Calif. Berkeley, 510-643-8520.
-----------
Text Notes:
... ... *Pulsars: Pulsars were originally discovered at
radio wavelengths, but there are optical, gamma-ray, and x-ray
pulsars, and some of the gamma-ray pulsars are extremely powerful
gamma-ray emitters.
... ... *binary systems: Binary stars are a pair of stars
revolving around a common center of mass under the influence of
their mutual gravitational attraction, and apparently the
majority of stars in the Universe are binaries and not singlets.
In some cases the binary system is resolvable into two
components, and in other cases the presence of a second star is
inferred by perturbations in the motion or emitted radiation of
the first star. If the binaries are close enough, they may share
stellar material, and this results in a particular kind of
stellar evolution.
... ... *gamma rays: Gamma rays are radiation of high energy,
from about 10^(5) *electronvolts to more than 10^(14)
electronvolts -- radiation with the shortest wavelengths and
highest frequencies, the gamma ray region of the electromagnetic
spectrum merging into the adjacent lower energy x-ray region.
... ... *electronvolts: An  electronvolt is defined as the energy
acquired by an electron falling freely through a potential
difference of one volt, and is equal to 1.6022 x 10^(-19) joule.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 16Apr99


5. FIRST DISCOVERY OF AN ASTEROID WATER INCLUSION
     The term "meteor" refers to a piece of solid matter from
space that penetrates the Earth's atmosphere at a hypersonic
speed of typically 10 to 20 kilometers per second, with
atmospheric friction causing it to become incandescent. Outside
the Earth's atmosphere, it is known as a "meteoroid"; any part
that survives passage through the atmosphere and reaches the
surface of the Earth is called a "meteorite". Most meteorites are
thought to originate in the asteroid belt between the orbits of
Mars and Jupiter, although tracking of entry paths indicates that
before colliding with Earth meteorites have highly elliptical
counterclockwise orbits about the Sun (in the same sense as the
planets).
     Meteorites are often named after the place on Earth where
they are found, and they divided roughly into 3 main classes
according to their composition. "Iron meteorites" consist of an
alloy of iron and nickel; "stony meteorites" consist of silicate
minerals; and "iron-stony meteorites" are a mixture of the two
previous types. The stony meteorites are further divided into
"chondrites" and "achondrites". Chondrites contain small
spherules of high-temperature silicates ("chondrules") and
constitute more than 85 percent of recovered meteorites. The
achondrites range in composition from rocks made up essentially
of single minerals (e.g., olivine) to rocks resembling *basaltic
lava. Each category is further subdivided on the basis of
chemical composition. "Carbonaceous chondrites" have little or no
metal but abundant carbon, and display evidence of chemical
alteration by water; they have the highest proportion of volatile
elements and are the most oxidized. "Ordinary chondrites" (the
most common type) are intermediate in volatile element abundance
and oxidation state.
     All main types of meteorite have been dated isotopically,
with most studies involving the dominant chondrite fraction.
There are no obvious age differences between the meteorites of
the various groups, and chondrites, achondrites, and iron
meteorites consistently yield ages of approximately 4.45 to 4.50
billion years, which places the origin of these objects in the
era of the formation of the Solar System.
     Over the past three decades, researchers have become
increasingly aware of the fundamental importance of water and
aqueous alteration on primitive Solar System bodies. Some
carbonaceous and ordinary chondrites, long proposed as primordial
material relatively unchanged since formation, have apparently
been altered by interactions with liquid water within the first
10 million years after formation of their parent asteroids. But
the location and timing of the aqueous alteration, or the nature
of the aqueous fluid itself, are not known. Researchers have
attempted to model this aqueous process through analysis of
hydrated minerals present in the meteorites, and through computer
simulations of the alteration process, but a major obstacle to
the understanding of aqueous alteration of meteorites has been
the absence of actual samples of aqueous fluids in meteorites.
... ... M.E. Zolensky et al (7 authors at 3 installations, US)
now report the discovery and characterization of aqueous fluid
inclusions in an ordinary chondrite, the Monahans (1998) object.
The Monohans (1998) meteorite fell on 22 March 1998 in Monahans,
Texas (US). The fall was witnessed by 7 boys, and the first of
two stones was recovered immediately and carried to the Johnson
Space Center, where it was broken open in a filtered-air, clean-
room facility less than 48 hours after the fall. The authors
suggest this effectively eliminated the opportunity for aqueous
or other contamination. The authors report the presence within
the Monahans (1998) meteorite of crystals of halite (NaCl) and
sylvite (KCl) containing aqueous fluid inclusions. The fluids are
dominantly sodium chloride-potassium chloride brines, but they
also contain divalent cations such as iron, magnesium, or
calcium. The authors suggest two possible origins for the brines
are a) indigenous fluids flowing within the asteroid, and b)
exogenous fluids delivered into the asteroid surface from a salt-
containing object such as a comet. The authors further suggest
that "in either case, the inclusions provide ground truth
concerning the nature of water in the early Solar System."
-----------
M.E. Zolensky et al: Asteroidal water within fluid inclusion-
bearing halite in an H5 chondrite, Monahans (1998).
(Science 27 Aug 99 285:1377)
QY: Michael E. Zolensky, NASA Johnson Space Center, Houston, TX
77058 US.
-----------
Text Notes:
... ... *basaltic lava: Basalt is a dark gray to black igneous
rock of volcanic origin that cools rapidly. "Igneous rocks" are
rocks that have congealed from a molten mass.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 1Oct99


6. ON GLOBAL CLIMATE CHANGE
Environmental change involves jumps, fluctuations, and trends,
the environment changing through the operation of the internal
machinery of the *ecosphere (biosphere), and through the external
agencies of cosmic and geological forces. Evidence of past
environmental change, almost always incomplete, derives from
geochemical, physical, biological, historical, and instrumental
sources. In recent years, high-speed computers have allowed
researchers to manipulate complicated and reasonably realistic
models of environmental change, with modelling particularly
useful for studying changes in *sedimentary basins,
biogeochemical cycles, and climate. General circulation models,
run with appropriate boundary conditions, predict climates of the
past, and these predicted climates can be compared with
paleoclimatic indicators.
... ... R.B. Alley et al (3 authors 3 installations, US) present
a review of current research on global climate change, the
authors making the following points:
     1) Prediction of climate change requires observational
constraints on the current climate state, knowledge of the way
the coupled air-ocean-ice-earth-life system behaves, and
information on changing forcings such as solar variability.
Studies of past climate are also required to focus model-building
efforts on climate components that are likely to change, and to
allow testing of the ability of models to predict time-evolution
of the system.
     2) The last few million years have been generally cold and
icy compared with the previous hundred million years but have
alternated between warmer and colder conditions. These
alternations have been linked to changes over tens of thousands
of years in the seasonal and latitudinal distribution of sunlight
on Earth caused by features of Earth's orbit. Globally
synchronous climate change despite some hemispheric asynchrony of
the forcing is explained at least in part by lowering carbon
dioxide during colder times in response to changes in ocean
chemistry. We live in one of the warmer times of these orbital
cycles; the coolest times brought glaciation to nearly one-third
of the modern land area.
     3) Studies of past climate changes indicate that the Earth
system has experienced greater and more rapid changes over larger
areas that was generally believed possible, with jumping between
fundamentally different modes of operation in as little as a few
years. Most of the last 100,000 years or longer has been
characterized by large and abrupt regional-to-global climate
changes, and agriculture and industry have developed during
anomalously stable climatic conditions. New high-resolution
analysis of sediment cores indicates these past changes have been
caused by "*band jumps" between modes of operation of the climate
system. Recurrence of such band jumps is possible and might be
affected by human activities.
-----------
R.B. Alley et al: Global climate change.
(Proc. Natl. Acad. Sci. US 31 Aug 99 96:9987)
QY: Richard B. Alley [ralley@essc.psu.edu]
-----------
Text Notes:
... ... *ecosphere (biosphere): In general, the term "biosphere"
refers to the portion of the planet capable of supporting life.
It ranges from elevations of approximately 10,000 meters above
sea level to the deep ocean, and a few hundred meters below the
surface of the soil. The biosphere consists of the hydrosphere,
the lower atmosphere (troposphere), and the surface of the
*lithosphere, all three regions inhabited by metabolically active
organisms.
... ... *lithosphere: In current geology, the lithosphere is the
approximately 100 kilometer rigid upper layer of the crust and
upper mantle of the Earth.
... ... *sedimentary basins: The term "sedimentary basin" refers
to a subsiding area of the Earth's crust, which permits the net
accumulation of sediment, i.e., material derived from pre-
existing rock, from biogenic sources, or precipitated by chemical
processes.
... ... *band jumps: In this context, the term "band jump" refers
to an abrupt change from one range of variation to another.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 1Oct99
-------------------
Related Background:
ON THE POSSIBILITY OF RAPID CLIMATE CHANGE
Over the course of geologic history, the environment on Earth has
been far from static. Geologic evidence suggests that 600 million
years ago the atmosphere lacked sufficient oxygen to support
animal life. More recently, as indicated by sediments recording
conditions over the past 500,000 years, the climate of the planet
varied between at least two different states. The record from the
past 150,000 years is particularly well-preserved, offering
details concerning repeated climate changes. Between
approximately 131,000 and 114,000 years ago, a warm period
similar to the climate of today occurred. This was followed by
what is called the "Wisconsin ice age", which ended approximately
12,000 years ago when the current relatively warm *Holocene
period began. ... ... Kendrick Taylor (Desert Research Institute,
US) presents a review of the research of a large project to
develop a climate record for the past 110,000 years, the author
making the following points:
     1) The layerings of glacial ice record seasonal variations
of temperature, snowfall, concentrations of atmospheric gases,
and atmospheric circulation patterns. In general, the weight of
accumulating snow compresses the snow below it, trapping
atmospheric gases, dust, and chemicals, and a deep ice core thus
provides a sequential record amenable to analysis.
     2) The author reports that by examining ice cores from
Greenland, he and his colleagues have determined that climate
changes large enough to have extensive impacts on our society
have occurred in a time-frame of less than 10 years. The author
suggests that the climate of Earth could change significantly
during a lifetime, that we are still a long way from being able
to predict such a change, but we are getting closer to an
understanding of how it might occur. A pressing concern is
whether anthropogenic changes in the atmosphere of the planet
might perturb climate stability.
     3) The author points out that climate is the result of the
exchange of heat and mass between the land, ocean, atmosphere,
ice sheets, and space. As long as changes to the land, ocean,
atmosphere, and ice sheets stay below certain thresholds, climate
changes will occur slowly. But climate will change rapidly if
those thresholds are crossed. *Greenhouse warming, for example,
by altering ocean circulation and the flow of tropical heat to
the North Atlantic, could lead to rapid cooling in eastern North
America, Europe and Scandinavia. Altered ocean circulation could
lead to much larger changes. We have no experience predicting
climate switches between stable modes.
     4) The author suggests human ingenuity would most likely
allow us to adapt to a rapid change in climate, but we would pay
a larger price than our civilization has ever known. The author
poses a scenario: "Imagine the economic and social cost of
moving, in a 20-year period, most of our agricultural activities
500 miles south of their current locations. Imagine the social
cost and famine if agriculture could not be relocated quickly
enough."
     5) Although we do not know the critical level of greenhouse
gas concentration that would trigger a rapid climate change, we
do know that reducing the rate of greenhouse emissions would help
in two ways. First, the atmospheric concentration of greenhouse
gases would increase more slowly. Second, numerical models
predict that the climate threshold will occur at a higher
concentration of greenhouse gases if the concentration of
greenhouses increases slowly.
     6) The author suggests it will be another 20 years before
the climate changes that are predicted to be associated with the
greenhouse effect becomes large enough to be unambiguously
differentiated from naturally occurring variations in climate.
As a society we have the choice of ignoring the warning signs or
taking some action.
-----------
Kendrick Taylor: Rapid climate change.
(American Scientist Jul/Aug 1999 87:320)
QY: Kendrick Taylor [kendrick@dri.edu]
-----------
Text Notes:
... ... *Holocene period: The most recent epoch of the geologic
time scale, from approximately 10,000 years ago to the present.
... ... *Greenhouse warming: See notes to report #1, this issue.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 13Aug99
-------------------
Related Background:
ON CLIMATE FORCINGS IN THE INDUSTRIAL ERA
A "climate forcing" is an imposed perturbation of the Earth's
energy balance with space, for example, a change of the solar
radiation incident on the planet, or a change of carbon dioxide
in the Earth's atmosphere. The unit of measure of climate forcing
is Watts per square meter. Thus, the forcing due to the increase
of atmospheric carbon dioxide since pre-Industrial times is
approximately 1.5 Watts per square meter. Climate change is
combination of deterministic response to forcings and *chaotic
fluctuations -- the chaos a consequence of the nonlinear
equations governing the dynamics of the system. Quantitative
knowledge of all significant climate forcings is needed to
establish the contribution of deterministic factors in observed
climate change and to predict future climate. J.E. Hansen et al,
in a review of current considerations concerning climate forcings
in the Industrial era, make the following points: 1) The forcings
that drive long-term climate change are not known with an
accuracy sufficient to define future climate change. 2)
Anthropogenic greenhouse gases, which are well-measured, cause a
strong positive (warming) force. But other, poorly measured,
anthropogenic forcings, especially changes of atmospheric
aerosols, clouds, and land-use patterns, cause a negative forcing
that tends to offset greenhouse warming. 3) One consequence of
this partial balance is that the natural forcing due to solar
irradiance changes may play a larger role in long-term climate
change than inferred from comparison with greenhouse gases alone.
Current trends in greenhouse gas climate forcings are smaller
than in popular "business as usual" or 1 percent per year carbon
dioxide growth scenarios. The authors suggest that a summary
implication of their considerations is a paradigm change for
long-term climate projections: uncertainties in climate forcings
have supplanted global climate sensitivity as the predominant
issue. The authors further suggest that climate forcing scenarios
are essential for climate predictions, but if only one forcing
scenario is used in climate simulations, as has been a recent
tendency, the scenario itself is likely to be taken as a
prediction, as well as the calculated climate change. The authors
recommend that the use of multiple scenarios will aid objective
analysis of climate change as it unfolds in coming years.
-----------
J.E. Hansen et al (6 authors at National Aeronautics and Space
Administration, US)
Climate forcings in the Industrial era.
(Proc. Natl. Acad. Sci. US 27 Oct 98 95:12753)
QY: James E. Hansen [jhansen@giss.nasa.gov]
-----------
Text Notes:
... ... *chaotic fluctuations: The term "chaotic", in this
context, is specific. In the study of physical systems, the
term "chaotic behavior" has a specific meaning: the behavior of a
system is said to be "chaotic" if its final state is so sensitive
to the system's precise initial conditions that the behavior of
the system is in effect unpredictable and cannot be distinguished
from a random process, even though the behavior of the system is
strictly determinate in a mathematical sense. In other words, a
deterministic system characterized by extremely sensitive
instabilities, despite the system being determinate, can exhibit
behavior that is unpredictable, and the system is then called
"chaotic". During the past several decades, the analysis of such
chaotic systems has intrigued both physicists and mathematicians.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 4Dec98


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

IN FOCUS: ON BIG SCIENCE AND LITTLE SCIENCE
"During a meeting at which a number of great physicists were to
give firsthand accounts of their epoch-making discoveries, the
chairman opened the proceedings with the remark: 'Today we are
privileged to sit side-by-side with the giants on whose shoulders
we stand.' This, in a nutshell, exemplifies the peculiar
immediacy of science, the recognition that so large a proportion
of everything scientific that has ever occurred is happening now,
within living memory. To put it another way, using any reasonable
definition of a scientist, we can say that 80 to 90 percent of
all the scientists that have ever lived are alive now... Because
the science we have now so vastly exceeds all that has gone
before, we have obviously entered a new age that has been swept
clear of all but the basic traditions of the old. Not only are
the manifestations of modern scientific hardware so monumental
that they have been usefully compared with the pyramids of Egypt
and the great cathedrals of medieval Europe, but the national
expenditures of manpower and money on it have suddenly made
science a major segment of our national economy. The large-scale
character of modern science, new and shining and all-powerful, is
so apparent that the happy term 'Big Science' has been coined to
describe it. Big Science is so new that many of us can remember
its beginnings. Big Science is so large that many of us begin to
worry about the sheer mass of the monster we have created. Big
Science is so different from the former state of affairs that we
can look back, perhaps nostalgically, at the Little Science that
was once our way of life."
-----------
Derek J. De Solla Price: _Little Science, Big Science_
(Columbia University Press, New York 1963, p.1)
[Editor's note: The term "Big Science" was first used by the
physicist Alvin M. Weinberg in 1961 (Science 21 Jul 61 134:164)]
 
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