Researchers Shed Insights into Higher Cells
Duke researchers have turned up new
evidence that the cells that make up
higher forms of life on earth evolved from
a primordial partnership between bacteria
and the progenitors of modern animal
cells.
The discovery, presented yesterday at
the 57th annual meeting of the
Federation of Societies for Experimental
Biology in Atlantic City, N.J., strongly
supports the theory that the
mitochondria of modern cells originated
as free-living bacteria.
The research was conducted by
Richard A. Weisiger, a medical science
trainee, under the direction of Dr. Irwin
Fridovich, professor of biochemistry.
The mitochondria are the tiny granules
A 14-year-old North Carolina boy
decided one day last fall to make a
batch of peanut brittle while his parents
were away.
He didn't realize that the peanuts he
used were seed peanuts, inappropriately
treated with a very toxic organic
phosphate insecticide, Thimet.
The boy shared the candy with five
brothers and sisters and a nephew. All
became ill and were taken to a local
hospital. One two-year-old was dead on
arrival at the hospital.
The doctor called the Duke Poison
Control Center, described the symptoms
and was given a recommended
treatment. The other six children
lecovered.
Cases like this come in to the Poison
Control Center at the rate of about 100
a month from all across the Southeast.
The center handled more than 1,500
poisonings during the year that ended in
November, about three-fourths of them
by telephone. The cases included five
deaths.
To Dr. Shirley Osterhout, a
pediatrician and clinical director of the
center, the most tragic thing about these
cases is that more than half involve
•children under four years of age. And
nearly all of them could have been
prevented if adults had been more
careful.
"It gives physicians a feeling of total
helplessness to treat a child whose
parents made no effort to make
themselves aware of potentially harmful
products and to keep them out of the
reach of children," she said.
There are thousands of household
items, from mouthwash and perfume to
bug sprays and bleach, that can be fatal.
Adults usually ingest such things by
accident, but a small child will eat or
drink almost anything he finds.
"It's really amazing how people get
into things," Dr. Osterhout said. "I hear
a new one every day."
Consider these recent cases handled
by the center:
— The man who died after drinking
the African Violet fertilizer which his
within the cell which carry out the
chemical reactions necessary to produce
energy for life functions. They are often
called the "powerhouses" of the cell.
Since the late 19th century, scientists
have been disputing the origin of this
primary unit of the cell.
Weisiger and Fridovich. have isolated
an essential enzyme—superoxide
dismutase—from liver mitochondria and
found that it is of the same type found in
present-day bacteria. This mitochondrial
form of the enzyme was found to be
different from the superoxide dismutase
found in the rest of the material that
composes higher cells.
This supports the theory that the
modern cell descended from a unit
wife had left in a lemonade pitcher.
— The teenage babysitter who
mistook the bottle of photographic
developing fluid in the refrigerator for
water and used it in the baby's formula.
— The man who woke up in the
middle of the night with indigestion,
fumbled in the medicine cabinet for
seltzer tablets and took a denture
cleaning tablet by mistake.
— The child who brushed his teeth
with a tube of skin ointment.
— The office worker who, without
reading the warning label, sprayed a
highly toxic industrial solvent onto a
co-worker who had spilled something on
her dress.
— The child who found a jar of
unlabeled liquid in an abandoned farm
outbuilding and drank it, also giving a
fatal dose to her dog.
The shelves of the Poison Control
Center in the Duke Hospital emergency
area are lined with dozens of empty
containers of oven cleaners, vitamins,
paint thinner, furniture polish, hair
sprays, moth balls, room deoderizers and
other products involved in past
poisonings. The walls are also lined with
reference books, literature and file
cabinets containing the chemical
compositions and treatment procedures
for thousands of toxic compounds.
Dr. Osterhout says the greatest
number of poisonings come from three
sources — cleaning agents,
over-the-counter medications and
insecticides.
"Just think about how many types of
cleaners, all of them toxic, there are in
the average home," she said. "There are
cleaners for ovens, rust, tires, windows,
floors, walls, toilet bowls, tile and
furniture and dishwasher detergents,
clothes detergents, liquid detergents,
bleaches, wax removers and drain
uncloggers."
In rural areas, insecticides are a
particularly big problem, especially those
jars and bags of unlabeled chemicals
passed from neighbor to neighbor. These
get stuck away in cabinets and
outbuildings until no one can rerpember
formed when a primordial bacteria
entered into a symbiotic, or mutually
beneficial, relationship inside the
membrane of a primitive animal cell.
Although the two evolved into a single
living unit, the Duke researchers found
that each part has retained its own
distinct form of superoxide dismutase.
The opposing theory has been that the
primitive animal cell itself gradually
evolved the mitochondrion from its own
cellular material.
Superoxide dismutase is an enzyme
necessary to all organisms which
metabolize oxygen. It exists to protect
the body against the toxic potential of
oxygen.
Billions of years ago, the primordial
exactly what’s in them. If a child drinks
some or a man collapses from breathing
the dust, the doctor has to treat them
without knowing what poisoned them.
Aspirin and vitamin poisonings of
children often occur when parents have
left the bottles on a table or counter.
The children, having been convinced by
television or their parents that the
flavored or sugarcoated products are
"just like candy," may consume the
whole bottle. Analgesics and the
"combination of ingredients" (Jain
relievers all contain aspirin, Dr.
Osterhout said. But many people don't
realize this and take several types of
cold and sinus preparations along with
aspirin. Before long they end up with
nausea and a ringing in the ears, a sign
of aspirin overdose. Some unwittingly
take more aspirin, then in an attertipt to
atmosphere is believed to have been
composed largely of ammonia, methane
and water. Ultraviolet radiation from the
sun reacted with these gases and slowly
converted the atmosphere to nitrogen and
carbon dioxide. Eventually, as nitrogen
reacted with the minerals of the earth's
crust, carbon dioxide became the major •
component of the atmosphere.
It was in this ancient oxygenless
atmosphere that scientists believe life
started, in the "organic soup" that made
up the primordial ocean. The first living
molecules, therefore, were anerobic.
But, as chlorophyll-containing cells
proliferated in the ancient seas, carbon
dioxide was gradually consumed and
molecular oxygen took its place. Cells
without chlorophyll were forced to adapt
to a toxic oxygen environment by
developing some form of the enzyme
superoxide dismutase.
Duke researchers found in 1968 that
eukaryotes-higher cells in which the
nucleus is bounded by a
membrane—possess a blue-green form of
superoxide dismutase containing zinc and
copper. Bacteria or prokaryotes-in which
the nuclear material is scattered
throughout the cell—developed a pink
form of superoxide dismutase containing
manganese.
Weisiger and Fridovich have for the
first time isolated superoxide dismutase
from the mitochondria of eukaryotes and
found it to be the bacterial form
containing manganese. The mitochondria
useo were from chicken liver. The same
•situation was shown to exist in
mitochondria from pig hearts and wheat
germ, and the researchers believe the
same results will be found in all higher
cells.
They believe this means that at some
time in the ancient ocean, a eukaryote
ingested a bacteria but didn't digest it.
The bacteria stayed on inside the host
cell, aiding with the respiration, and this
relationship helped the cell to flourish
and multiply, becoming the forerunner of
higher life today.
"The only likely explanation for
finding the manganese superoxide
dismutase in both bacteria and
mitochondria is that each is evolved from
the same ancestral enzyme," the
researchers said. "This is consistentonly
with the symbiotic theory of the origin of
mitochondria."
-YVONNE BASKIN
(Continued on page 3)
II
COMMON VILLAINS-Or. Shirley Osterhout, clinical director of the Poison Control
Center, examines her collection of products involved in past poisonings. Duke
treats-either directly or by telephone consultation with physicians-about 100
poisoning cases a month. (Photo by Jim Wallace)
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VOLUME 20, NUMBER 16 APRIL 20, 1973 DURHAM, NORTH CAROLINA
Toxic Substances Are Targeted
P.C. Center Assaults Accidental Death