Health Scan: New test studies how bacteria spread disease
By Judy Siegel
A way to monitor
toxic bacteria, designed
by Hebrew University
researchers, could pave
way for new antibiotics.
The system is being
called a "breakthrough"
in monitoring the
toxin-delivery system of
highly pathogenic
bacteria, as it could
help pave the way for
new drugs capable of
neutralizing those
germs.
Most bacteria are
harmless. Some, however,
are pathogenic and
equipped with special
accessories used to
deliver toxins (also
termed "effectors") into
the cells of an infected
person.
Bacteria that can result
in anything from food
poisoning to
life-threatening
infection use a
syringe-like nano-organelle
(a specialized part of a
cell having a specific
function) to inject
toxic effectors into
host cells. This process
is termed a type III
secretion system (TTSS).
Among these pathogens
are Salmonella; the
cause of typhoid fever,
Yersinia; and
intestinalE. coli, which
is responsible for the
death of up to a million
infants per year.
The bacterial syringe is
an excellent potential
target for
as-yet-unavailable
drugs. But to develop
such drugs, scientists
need to better
understand syringe
functions and develop
improved methods for
measuring syringe
activity.
The HU researchers -
Prof. Ilan Rosenshine (a
bacteriology expert at
the medical faculty) and
colleagues Erez Mills,
Kobi Baruch, Xavier
Charpentier and Simi
Kobi have designed a
new, real-time test that
allows monitoring of
syringe activity. Using
this test, they have
discovered new
properties of this
system which might be
used to develop drugs
that will inhibit the
activity and thereby
prevent disease and
infection.
Their achievement was
described in a recent
article in Cell Host &
Microbe.
DIABETES AND HEARING
Hearing loss is twice as
common in diabetics than
in healthy people,
according to US
researchers who advise
adults with diabetes to
have their hearing
checked.
Dr. Catherine Cowie of
the US National
Institute of Diabetes
and Digestive and Kidney
Diseases in Maryland
told UPI that the link
between diabetes and
hearing loss is evident
across all frequencies,
with a stronger
association in the
high-frequency range.
Mild or greater hearing
impairment of low- or
mid-frequency sounds in
the worse ear was about
21 percent in 399 adults
with diabetes, compared
to about 9% in 4,741
adults without diabetes,
Cowie says.
The study, published in
the Annals of Internal
Medicine, found that
adults with metabolic
syndrome (pre-diabetes)
had a 30%higher rate of
hearing loss compared to
those with normal blood
sugar. "Hearing loss may
be an under-recognized
complication of
diabetes," Cowie said.
"Our study found a
strong and consistent
link between hearing
impairment and diabetes
using a number of
different outcomes."
SUPPRESSING A RIOT OF
CELLS
A new approach to
fighting autoimmune
disease - in which the
immune system turns
against the body's own
tissues and organs for
no apparent reason - has
been developed by
Weizmann Institute
researchers. Partly
because the origins of
these diseases are so
obscure, no effective
treatment exists, and
the suffering they
inflict is enormous. But
a method that may make
it possible to treat
autoimmune diseases
effectively without
necessarily knowing
their exact cause has
been developed in the
Rehovot institute. The
approach is equivalent
to sending a police
force to suppress a riot
without seeking out the
individuals who
instigated the unrest.
In healthy people, a
small but crucial group
of immune cells called
regulatory T cells, or
T-regs, keeps
autoimmunity in check,
but in people with
inflammatory bowel
disease (IBD) - one of
the most common
autoimmune disorders -
too few of these cells
appear in the diseased
intestine, and the ones
that do fail to function
properly. The new
approach consists of
delivering highly
selective, genetically
engineered functioning
T-regs to the intestine.
The study was conducted
by Dr. Eran Elinav, a
physician from Tel Aviv
Sourasky Medical
Center's
gastroenterology
institute who is working
toward his doctorate at
Weizmann, and assistant
Tova Waks, in the
laboratory of immunology
Prof. Zelig Eshhar.
Relying on Eshhar's
earlier work, in which
he equipped a different
type of T cell to zero
in on cancerous tumors,
the team genetically
engineered T-regs,
outfitting these cells
with a modular receptor
consisting of three
units. One of these
units directed the cells
to the intestine while
the other two made sure
they became activated.
As reported in
Gastroenterology, the
approach proved
effective in laboratory
mice with a disease that
simulates human IBD:
Most of the mice treated
with the
genetically-engineered
T-regs developed only
mild inflammation or no
inflammation at all.
The cells produced what
the scientists called a
"bystander" effect: They
were directed to the
diseased tissue using
neighboring, or
"bystander" markers that
identified the area as a
site of inflammation,
and suppressed the
inflammatory cells in
the vicinity by
secreting soluble
suppressive substances.
The scientists, who are
currently experimenting
with human T-regs for
curing ulcerative
colitis, believe that in
addition to IBD, their
"bystander" approach
could work in other
autoimmune disorders,
even if the causes
remain unknown. They
also think the method
could be valuable in
suppressing unwanted
inflammation in diseases
unrelated to
autoimmunity, as well as
in preventing graft
rejection and certain
complications in bone
marrow and organ
transplantation.
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Mercury
sources and
toxicity ROCHESTER, NEW YORK. Mercury is a highly toxic metal associated with damage to the kidneys and central nervous system. Mercury vapour is emitted from volcanoes, coal-burning power stations, and municipal incinerators and returns to the earth through rain contaminated with metallic mercury. Metallic mercury is methylated to methyl mercury in oceans and lakes and enters the food chain via fish and other seafood. Long-lived predator fish such as shark, swordfish, tilefish, king mackerel, and pike and bass in fresh water are the main sources of methyl mercury. Dental amalgams are an important source of mercury vapour and the vaccine preservative thimerosal is a significant source of ethyl mercury. Researchers at the University of Rochester School of Medicine recently published a review of what is currently known about mercury toxicity. Among the highlights:
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ADA fighting the
mercury battle
GAITHERSBURG, MARYLAND.
The American Dental
Association (ADA) has
launched an advertising
campaign to discourage
patients from having
their amalgam (silver)
fillings removed. Many
patients and sometimes
even their physicians
believe that mercury,
the main component of
amalgams, plays a role
in promoting such varied
diseases as Alzheimer's,
multiple sclerosis, and
autism. The ADA says the
evidence is not there
and their Code of Ethics
forbids dentists from
advising their patients
that there could be a
link. Scientists at the
University of Milan
disagree with the ADA
and point out that
several studies have
confirmed that mercury
from amalgam dental
fillings does enter
tissues and that the
mercury content of
brain, thyroid, kidney,
and pituitary gland
tissue is proportional
to the number of amalgam
fillings. They conclude
that the health effects
of amalgam fillings are
not at all clear and
need further
investigation. German
researchers point out
that some of the
composite materials used
in the replacement of
amalgam fillings may in
themselves be toxic.
Larkin, M. Don't
remove amalgam fillings,
urges American Dental
Association. The Lancet,
Vol. 360, August 3,
2002, p. 393