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Amount of Dosage
Some radiation phenomena, such
as genetic effects, are apparently
independent of the rate of delivery
of the radiation, and depend only
on the total dosage.
In the majority of instances, however, the
biological effect of a given dose of
radiation decreases as the rate of
exposure decreases.
Thus, to cite an extreme case,
600r would certainly be fatal if absorbed by the whole body in one
day, but it would probably have
no
noticeable
consequences
if
spread over thirty years. The most
reasonable explanation of this fact
is that if the dosage rate, that is,
the amount of radiation taken per
day, is very small, the damaged
tissues have a chance to recover.
If the intensity or rate of delivery
of the radiation is increased, re-
covery cannot keep up with the
damage.
It is apparently
the
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Hereditary Factors
Because of the possible importance of the subject for the future
of the human race, no discussion
of radiation injury would be complete without consideration of the
genetic (hereditary) effects. These
effects differ from most other
changes produced by radiation in
mutations may actually be ultra-
and, within limits, independent of
an individual must receive the mutated gene from both parents be-
that they appear to be cumulative
the dosage rate of the energy of
the radiation.
The
mechanism of
heredity
is
essentially similar in al! sexually
reproducing plants and animals,
including man. The material re-
sponsible for inheritance is organ-
ized into discrete structures, the
chromosomes,
Which
are
visible
microscopically in the nuclej of dividing cells.
The chromosomes,
rod-shaped
bodies, are considered to be fine
threads of nucleoproteins
(group
recovery
of proteins combined with nucleic
human beings to accept limited
doses of radiation, at least 0.3 r
per week for long periods without
any
apparent
harmful
conse-
length into thousands of distinctive
but
submicroscopic
units,
the
factor that makes it possible for
quences.
While little of a specific nature
can be done in the treatment of
radiation sickness where the acute
dose is 600r or more, there is a
possibility that where the dose is
smaller, particularily 400r, or less,
many lives can be saved with proper treatment. Immediate hospitalization, to insure complete rest,
and avoidance of chills and fatigue,
is an essential first step.
Whole blood transfusion should
be given, as required, until the
bone marrow, the blood-forming
tissue quickly damaged by radiation, has had time to regenerate
and produce blood cells. Adequate
nourishment could be provided by
intravenous feeding to supply the
necessary sugars, proteins, vita-
mins, etc.
The danger of infection, from destruction of the
germ-fighting
white blood cells, may be con-
trolled by the use of penicillin and
other antibiotics. The whole sub-
ject of radiation sickness, a rare
occurrence before the bombings of
Hiroshima and Nagasaki,
is in-
tensively studied. and important
advances in its treatment may be
expected.
3
acid, the latter a constituent of
the nuclei of living cells), which
are differentiated along their
genes,
The development of inherited
characteristics is controlled by the
action of the genes. Chromosomes,
A Matter of Time
Incomplete experimental work
on mice leads to the important
microscopic changes in chromosome structure.
Mutated genes are commonly
classified as either dominant over
the normal genes, in which case
the individual will show the particular characteristic if he receives
the mutated gene from either
parent, or recessive, in which case
practical conclusion that the prob-
ability of passing on chromosome
aberrations to the next generation
will be greatly reduced if individ-
uals exposed to doses of radiation
refrain from begetting offspring
for two to three months after exposure.
It should, however, be stressed
that,
fore exhibiting the characteristic.
deleterious,
the occurrence éf
beneficial mutations being very
rare.
calculate the exact magnitude of
the risk. It is obvious, therefore,
There is a large body of data
which indicates that any doSe of
radiation. no matter how small, increases the probability of genetic
changes.
Until recently the risk
would have been thought to apply
mainly
to
distant descendants,
that until more basic knowledge is
available, exposures of personnel
should be kept to a minimum.
It may be mentioned, however,
that the possibility of the produc-
tion of a race of monsters in Japan
as a result of radiation emitted by
the atomic bombs is extremely im-
when the probability of two recessives mating would be greater.
New information on the frequency
of partial dominants indicates that
the risk may not be negligible even
to the first generation.
probable in the opinion of geneticists who have made careful study
of the subject.
classified roughly into two categories. Microscopically detectable
changes in chromosome structure
are called chromosomal] mutations
or aberrations. They may be re-
sponsible for visible changes in inherited characteristics, may cause
reduced fertility, and frequently
may be lethal, preventing development of the embryos.
The Gene Mutations
The second category, gene mutations, include those cases in which
sudden changes in inherited charthe result
of
demonstrable changes in chromo-
some structure but rather are believed to be from changes in the
chemical composition of the nor-
mal gene.
evidence
man populations have not yet been
obtained. We are not yet able to
Mutations, defined as changes in
inherited characteristics, may be
not
the
Many of the basic data necessary for a reliable estimate of the
genetic effects of radiation in hu-
contributed by each parent through
the sperm or egg.
are
to
little or no reduction in the risk
of transmitting gene mutations.
pear
to
be recessive,
recent
evidence indicates that many socalled recessives are partially dominant.
Almost all mutations are
and hence the genes, occur in pairs
in the nuclei of the cells of individuals, one member of each pair
acteristics
according
available, this practice would cause
While most gene mutations ap-
The possibility remains,
however, that many so-called gene
tI