Project Title:
16.
Effects of Radiation on Living Organisms
Early and Late Effects of Radiation of Different
Quality and at Different Dose Rate
RX-03-O1-{a)|
Technical Progress in FY 1973:
(Cont'd.)
In the CNS studies,cesting continued on the visual acuity of monkeys
that previously received bilateral x-ray exposures in the 500-2,000 rad
range.
At sixteen months post-exposure no decrement in visual acuity has
been observed.
Due to budget Limitation additional animals have not been
irradiated;
however,
data on
the present animals will
collected until they exhibit a decrement or until
terminate the study.
continue to be
it is necessary to
The last of the sharks exposed to 30,000 rads were sacrificed and
the brains examined for both gross and microscopic changes. The earlier
findings indicating essentially no effect
radiation were confirmed.
from these massive doses of
“%
>
The feasibility of making electrophysiological measurements on the
shark brains using implanted electrodes was investigated.
Some base-line
recordings were obtained which were encouraging.
However, the techniques
must be improved before they can be used to determine whether any functional
changes take place in the irradiated shark brain.
(Carsten)
The genetic effects of neutron irradiation were studied in Drosophila,
using the frequency of translocations, sex-linked recessive lethal mutations,
and dominant lethal mutations as endpoints, For translocations, the x-ray
curve is curvilinear while the neutron curve is linear.
The RBE is less
than one at all dose levels studied.
For sex-linked recessive mutations,
the response curve appeared to be Linear for both neutrons and x rays,
and the RBE of neutrons is less than unity.
Using sex-linked recessive
lethal mutations, the RBE was determined for cells in various stages
of spermatogenesis in order to see if the low RBE values might be due
to the shape and small size of the sperm nucleus,
The RBE for early
Spermatids, although less than unity, was no greater chan that for
mature sperm.
Thus the low RBE is not due entirely cto the small size
of the sperm nucleus nor to the highly condensed state of the chromosomes.
:
.
Also, extensive work was carried out to verify the work of Per Oftedal
indicating that genetic effects of very low doses may be greater than
that predicted with extrapolation from high doses.
Unfortunately, chis entire program had to be terminated with the
Dr. Abramson has collected and is studying
untimely death of Dr. Gonzalez.
Mra obtained by Dr. Gonzalez, and it is hoped that the material can be
It is hoped,
ately analyzed and reported.
©
continue
these
important
studies.
ta
also,
that means can be
‘Extensive work, particularly important to testing theories of radiobiological action, have been carried out in the Biology Department using
Tradescantia stamen hair test systems (A. H. Sparrow and A, J. Underbrink).
(See Continuation Sheet)
[119263
RX-170