Duke
scientists
solve
mystery
Bulls see red
Ohvas
By David Williamson
A Duke researcher believes he and his
associates have settled once and for all the
question of whether a bull can see red.
While it's not the kind of breakthrough
that will guarantee a Nobel Prize, there
are plenty of scientists and matadors who
will be pleased to know that the answer is
"yes."
Dr. Myron Wolbarsht, professor of
ophthalmology and biomedical
engineering, said in an interview that the
experiments were conducted on cats, but
the findings probably can be duplicated in
all mammals, including bulls, because
their eyes are so similar in structure.
Until now, he said, primates (man,
monkeys, etc.) were the only mammals
known to be able to distinguish all the
colors of the rainbow.
The investigators discovered that the
cat possesses three kinds of color receptor
cells in its retina, the sensory membrane
lining the inner surface of each eye.
Tlie brain needs all three varieties of
these cells, which are called "cones," to
recognize the primary colors red, blue and
green and blend them into other hues.
"Previously, people have identified only
two receptors in the cat so they assumed
that the cat and other mammals were
blind to either red or green," Wolbarsht
said.
The experiments, which were part of a
larger series of studies related to laser
safety, involved shining a range of
colored lights into the eyes of
anesthetized cats.
While the different lights were on, tiny
electrodes picked up changes in the
natural electric responses within the
(Continued on page 3)
Duke University
Medical Center
Intercom
VOL. 25, NO. 2
JAN. 13, 1978
DURHAM, N.C.
Shining light through head may save lives
Using the same principle that allows a
child to see light through his hand when
he presses a flashlight against it, a Duke
researcher has devised a method of
determining how well brain.cells take up
oxygen from blood.
Dr. Frans Jobsis, professor of
physiology, said he believes the new
technique eventually may help to save
lives in hospital intensive care units and
have a number of other useful medical
applications as well.
It involves sending harmless infrared
light through the skull and to the brain
and then measuring how much of the
light emerges on the opposite side of the
head.
Less than bright sunlight
Jobsis, who performed the first human
experiments on himself, said there is no
pain involved and no radioactivity. Less
infrared light is required than a person
would receive walking in bright sunshine.
"Science" magazine published an
account of his research in its Dec. 23
issue.
In an earlier interview, the scientist
explained that when blood squeezes
through capillaries in the brain,
hemoglobin molecules contained in red
cells release oxygen to a respiratory
enzyme found in nerve cells.
This enzyme, called cytochrome aa-3,
changes color as it becomes rich in oxygen
and absorbs more, infrared light particles
than it does when it is oxygen deficient.
More light, less oxygen
A device known as a photomultiplier
transforms infrared light that has passed
all the way through the head into an
electric current that can be continuously
monitored. Jobsis said that increases in
the amount of light recorded correspond
to decreases in oxygen.
• "Just about all deaths can be attributed
to a lack of oxygen in the brain," the
scientist said. "A person doesn't die
because his heart stops, for example, but
because the mechanism for transporting
oxygen to brain cells has broken down."
Currently, physicians in intensive care
units can record the oxygen content of
blood, blood pressure and the circulation
of blood within the head. Monitoring
circulation, however, requires radioactive
tracers tha^t are unsafe to use
continuously.
All of these measurements are indirect,
Jobsis said, and the brain may begin dying
before medical personnel are aware of it.
"The crucial difference here is that we
can now directly observe the enzyme that
takes oxygen so that we are as close as
possible to observing the whole purpose
of the vascular system," he said.
Lasers that produce exact wavelengths
of infrared light are used in the
continuing experiments since they
require little power. Flexible bundles of
glass fibers carry the light from the lasers
to the head and then back to the recording
equipment.
Infrared light was selected, the scientist
explained, because it has a much greater
ability than visible light to penetrate
biological materials. Infrared lies just
beyond what humans can see in the
visible spectrum as the color red.
Jobsis said he's been studying optical
(Continued on page 2)
IN ONE SIDE AND OUT THE OTHER—Dt. Pram Jobtis, profeisor of
physiology, modeb a new device he has created to measure how well
brain cells take up oxygen from hemoglobin. The equipment records
cnanges in ab«orptk>n of infrared light that hat passed all the way-
through the head. (Pheh by Jim WalUu)