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AUG 22 1967
MASTER
RADIATION EFFECTS IN THE SORICIDAE, CRICETIDAE, AND MURIDAE *
P. B. Dunaway, L. L. Lewis, J. D. Story, J. A. Payne", and J. M. Ingliss
· Radiation Ecology Section, Health Physics. Division,
Oak Ridge National laboratory, Oak Ridge, Tennessee
: ABSTRACT
Effects of acute, Cºco gamma irradiation under controlled conditions in
...the laboratory were compared in six species of rodents in the Cricetidae, two
8 species in the Muridae, and two species of shrews in the Soricidae. Estimates
of LD50-30 for these ten species ranged from 525 to 1069 rads. The most radio-
resistant species (two species of Peromyscus) and the most radiosensitive spet
cies (Oryzomys palustris)were cricetids. Average survival times of decedents
12 at highest radiation doses (1560-2060 rads) were longer among cricetias (5.6-
8.1 days) than in murids (4.4 - 5.1 days) or soricids (3.5 - 4.3 days), and
14 interspecific variation was manifested within families. Survival times were
longer and ID50 estimates were greater in RF-strain, female Mus musculus
caged alone than in females caged in groups of five or in males caged either
singly or in groups. At high doses, weight losses were rapid and severe in
all species, but at lower doses considerable interspecific differences were
seen in time of onset and magnitude of weight changes. Other symptoms of ra-
diation damage were conjunctivitis, ataxia, diarrhea, passiveness, cessation
of feeding, aggressiveness, and pelage "graying."
we
?Deceased
2présent address: USDA, Coastal Plain Experiment station, Tifton, Ga.
3present address: Texas A. and M University, College Station, Texas.
* Research sponsored by the v. S. Atomic Energy Commission under contract
with the Union Carbide Corporation. ?.
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DISTRIBUTION OF THIS DOCUMENU E UNILATES
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INTRODUCTION
A relatively narrow range of radiation sensitivity has been reported for
most small laboratory mammals. I.D.0-30 esiimates (hereinafter referred to as
"I D50") for these mammals usually range fror about 300 to 900 rad. Differ-
ences in radiosensitivity apparently exist even among strains of laboratory
rodents. For example, LD50 estimates for 13 strains of laboratory mice irradi.
ated under comparable conditions ranged from 567 to 795 R (Davis et al. 1963).
Kohn and Kallman (1956) reported differences in LD50 estimates (544-665 R) and
death řates among four inbred strains and F, reciprocal crosses of two of the
strains. Estimates of LD 50 for larger mammals, including man, usually fall
between 150 and 600 rad, ' but such estimations are complicated by significant
12 shielding afforded by tissues, and results must be specified in terms of
surface, tissue, or midline doses.
: One of the earliest studies of radiation effects in a wild rodent (Kohn
and Kallman, 1956) reported an Dian 08/615 R for feral house mi.ce (Mus musculus).
Haley. et al. (1960) showed that survival times and hematological changes in
19 the kangaroo rat Dipodomys merriami' were similar to responses in laboratory
mice and rats, and mortality after 550 R was 93% by the fourteenth day. Com-
paratively high ID5o estimates have been reported. recently for other
species of wild rodents. Gambino and Lindberg (1964) calculated LD50
estimates' of 1520 R for the little pocket mouse (Perognathus longimembris)
and 1300' R for the longtail pocket mouse (L. formosus). Chang (1964)
reported survival of 9 out of 10 mongolian gerbils (Merlones unguiculatus).
at 1000 R, and 'out of 10 survived .1500 R. Golley et al. (1965) estimated
25 IDEO doses of 1125 R for old-field mice (Feronyscus polionotus), 1130 R for
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tootage.
cotton mice (P. gossypinus), and about 1200 R for the eastern harvest mouse
(Reithrodontomys humulis); their estimate for wild M. musculus was only about
700 R. Kellogg (1965) reported an ID 50 of 1155 R for the cotton rat (Sigmo-
don hispidus). Radioresistant species thus have been reported in the rodent
families Heteromyidae and Cricetidae.
Measurements of radiation effects in captive indigencus marmals began
at Oak Ridge National Laboratory (ORNL) during the summer of 1964. Need for
such research was twofold: (1) radiation responses of various species under
standard conditions were required for design of future studies of the effects
of Irradiation on natural populations, and (2) comparisons of radiation effects
in native species and laboratory mamals were necessary for evaluating the
applicability of relevant radiobiological data from laboratory animals to
wild species. Furthermore, comparisons of radiation effects in various
classifications of mammals may help demonstrate to what extent radiation,
response is related to taxonomic status.
We thank L. E. Tucker, B. E. Jacobs, C. M. McConnell, N. A. Miller, Jr.,
T. P. O'Farrell, and R. S. Berry for assistance during parts of this study.
Thanks are due R. E. Textor and A. A. Brooks for help with mortality and sur-
vival-time analyses. D. G. Gosslee did the probit analyses of IDEO: E. B.
Darden, Jr., provided the RF-strain mice. G. E. Cosgrove examined pathologies
in some animals. This research was supported by the AEC under contract with
the Union Carbide Corporation.
MATERIALS AND METHODS
Eight species of indigenous rodents, two species of shrews, and one
strain of laboratory mouse were used in these experiments. Species in the
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iwi.ly Cricetidae 'were, in increasing order of weight (nones after Hall and
Kelson, 1959):. eastern harvest mouse, Reithrodontomys humulis; white-footed
mouse, Peroinyscus leucopus; golden mouse, Perómyscus nuttalli; pine vole,
Microtus pinetorum; marsh rice rat, Oryzomys palustris; and hispid cotton
rat, Sigmodon hispidus. Members of the Muridae used were: house mouse,
Mus musculus; a laboratory strain (RF) of M. musculus; and Norway rat, Rattus
norvegicus. Species in the Soricidae were; least shrew, Cryptotis parva;
and short-tailed shrew, Blarina brevicauda. The wild rodents were either
live-trapped locally or raised in the laboratory; the shrews were all live-
trapped. The RF-strain wice were from a colony at the Biology Division, ORNL
All animals were subadults or adults. Animals were caged individually, ex-
12 | cept for M. musculus used in crowding-stress experiments. Nest boxes or
cans were provided for all animals except the shrews. Shrews were kept in
cages containing chunks (~1.5 x 2.2 x .8. 2) of sod because their fur
became oily and matted if soil or a similar material was not available to
them.
Food and water were given ad Libitum. Temperature was 224 2°C. Hunid-
ity for wild species was 50+ 5%, but hymidity was not controllable in the
room in which RF-strain mice were kept. The wild species were held in two
adjacent and interconnected colony rooms, but the RF-strain mice were kept
in a separate room because these laboratory mice, like many inbred strains,
are subject to diseases endemic in wild forms. Fluorescent lights were on 12
hr per day. Irradiation and daily inspections were done between 0800. and
1100. Disturbance in the colony rooms was kept to a minimum, because the
wild species did not become teme and reacted quickly to sudden movamants or
LEGAL NOTICE

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Animals were irradiated in a Gammacell-200 °°Co unit. Dose rate ranged
I'ron 828 rad/min at the beginning of the series of experiments to 600 rad/min
at the end. Dose was measured with Toshiba low-2 silver metaphosphate glass
dosimeters. Glass rods irradiated with known doses at ORNL and the National
Bureau of Standards were used as standards. Groups of euch species received
0, 500, 690, 875, 1065, 1250, 1625, or 2000 rad. Preliminary estimates of
ID go for each species were then made on probit graphs, and additional groups
of each species were given bracketing doses around the estimated Liban doses
in order to refine the estimates. Final probit analyses were made with the
ORNL "PROBIT" computer program that provided 95% significance. limits around
the IDsoestimates.
:...RESULTS
:::.. Mortality
No significant differences in mortality of indigenous species were demont
16 strable between sexes and between wild-caught or laboratory-bred animals.
The two species of Pe.romyscus were the most radioresistant, with respect to
mortality, of all wild species tested, but ID50 estimates for most of the
other cricetids were not much less and tell within a narrow range of 939-958
20 rad (Table I). The rice rat, however, was by far the most radiosensitive of
all species tested. Estimates for the two wild murids were slightly lower
22 Iwan estimates for all cricetids except 0. palustris. The shrews also seem
to be relatively radiosensitive.
The LDgo estimate for RF-strain mice caged alone was significantly high-
er than that for RF mice caged in groups. The difference was primarily at-
20 tributable to the significant difference between the females of the two groups
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and not to a difference between males (Table I). Estimates for the wild
male or female M. musculus caged together were not siguilicantly lower than
estimates for their singly-caged couñierparts. Although close observations
of social interactions were not practical, it was obvious that wild or for
| house mice caged in groups quickly set up hierarchies after initial fighting,
but individuals were still bitten occasionally, especially on the tail,
during the 30-day postirradiation period. However, the mortality among
most-bitten individuals was not significantly greater than that of nonbitten
or less-bitten animals.
Survival Times
Postirradiaticn survival times of decedents were fairly predictable for
each species at high doses (120C-2060 raä), but results varied more at lower
doses, variability at those doses depending in large part on relative radio-
sensitivity of the species. No significant differences in the wild species
were apparent in survival times of sexes or in the wild-caught or laboratory-
bred specimens. Survival times of most cricetids at the highest doses were
relatively long in comparison to the other families (Fig. 1). Peromyscus
leucopus, the most radioresistant species ( in terms of LD., had the short-
est survival times of the cricetids. On the other hand, p. nuttalli, another
radioresistant species, exhibited longest survival time of all species. The
most radiosensitive species, O. palustris, had second shortest survival times
22 of the cricetids. The wild murids caged alone did not survive long at the
highest doses. Survival times of the soricids also were relatively short.
At highest doses (1560-2060 rad), where times were almost identical for each
species, average times' ranged from 3.5-4. 3 days for the soricids, 4.4-5.1 days
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for the murids, and 5.6-8.i days for the cricetids.
Species size was not related to survival times, even within families.
In the Cricetidae, the two Peromyscus were virtually the same size, but, as
pointed out, one species had the longest and the other the shortest survival
times in the family. The tiny R. humulis survived longer than the rat-sized
cricetids, but the pine" vole lived about as long as the rats. Similarly,
house mice usually lived longer than the much larger Norway rat, but the
short-tailed shrew, four or five times larger than the least shrew, lived
about as long.
Survive! times for grouped RF nice were considerably less fron about
900-2060 rad than for solitary RF mice (Fig.1). However, this difference
was attributable to the singly-caged females, which had consistently longer
survival times then did singly-caged males; times for males caged alone
were not consistently different from times of either sex caged together.
On the other hand, survival times for singly-caged wild M. musculus were
shorter than times for grouped wild house mice, in spite of the fighting
that occurred among the grouped mice. No consistent difference in survival
times of the wild mice at the highest doses was seen between sexes caged
alone or in groups, but times of each sex caged singly were consistently less
than times of the respective sexes caged together.,
* Weight Changes
Postirradiation weight losses at all doses for all species at death ranged
from 9-38%, and differences in extremes for each species ranged from 6-24%.
Considzring only the three highest dose groups, weight losses of all species
were 24-34%, and differences in extremes for each species reduced to 2-10%

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(Table. II). Animals losing most weight (average) at these highest üoses
were: RF mice caged singiy, 33%; RF mice caged together, 31%; vild M. muscu-
lus caged together, 31%; and P. nuttalli, 29%. Species showing least loss
at the highest doses were P. leucopus, 16%; R. humulis, 176; O. palustris,
19%; and R. norvegicus, 20%. Differences in weight loss among species were
not ascribable to taxonomic status, at least at levels under consideration,
and no relation with species size was discernible.
Weight changes of control animals of each group were plotted in terms of
percent weight change from day o. Of the four irradiated groups losing most
10 | weight, controls of both groups of RF mice and the p. nuttalli gained weight
steadily during the month following day o. Controls of the other irradiated
group exhibiting considerable weight loss (wila M. musculus caged together)
gained weight until about day 15, after which average weight dropped to about
the same level as weight at day o. Controls of three species (P. leucopus, it
Q. palustris, and S. hispidus) lost about 5% of their weight during the
first week, then gained weight during the subsequent three weeks, but
did not recover the loss. M. musculus. caged alone, R. norvegicus, and M.
pinetorum lost approximately 5% during the first week, but gained slowly
to near or slightly above original values. R. humulis was the only species
in which controls'increased in weight (106%) during the first week and then
lost weight slowly until, during the last week, average weight loss was
about 4%.
. Other Radiation-Effects Symptoms
Symptoms in irradiated mice included conjunctivitis, ataxia, passiveness,
cessation of feeding, diarrhea, aggressiveness, and "graying" of hair.
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Appearances of the first four symptoms usually, not invariably, were followed
by death, but death was not always preceded by all of these symptoms.
Conjunctivitis caused "wavering of the eyes," and in many cases the exudate
matted the eyelids together so that animals could not see. Ataxia in most
species was sometimes present for several days and was characterized by
uncoordinated and slow movements. Ataxia in shrews, however, usually was
not pronounced until a few hours before death. Passive animals of all.
species in a terminal stage, exhibited the "righting reaction" until they
were moribund. Cessation of feeding ordinarily was gradual, but little or
no food usually was ingested for 2-3 days before death. In some cases, even
shrews ate little or nothing for 1-2 days before death, suggesting a drastic
slowing of metabolism in these animals, which normally must ingest a con-
siderable amount of food each day. Diarrhea was noted mostly at higher
doses, and in a few cases blood was present in the discharge. Increased. ).
aggressiveness occasionally appeared in some individuals. This change in
behavior was particularly noticeable in R. humulis acd P. nuttalli, species
which characteristically cowered in their nests during inspection and were
relatively slow-moving. Irradiated individuals sometimes became aggressive,
sat up on their hind legs, and attacked fingers or other objects inserted
ato their nests.
Pelage graying is one of the most striking consequences in mammals
receiving substantial but sublethal doses of irradiation. Because of
colony-space limitations, graying sequences were followed in only a few
specimens of B: brevicauda, P. leucopus, s. hispidus, and M. musculus. In
most of the individuals observed, development of graying was similar to
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1 that shown for laboratory animals; 1.e., unpigmented hair replaced pigmented
2. hair when the animals inolted. "Chase (1949) showeä that response (percentage
of white or mosaic hairs) was proportional to dose and that response was rauch
greater in resting follicles than in growing follicles. Graying 10. P. ieu-
copus is shown in Fig. 2. The pattern of graying shown is similar to that
seen in all rodents examined, i.e., graying began on the head, appeared next
on the dorsum and/or sides, and progressed posteriorly. However, graying
tine varied between individuals. In Fig. 2, note' that graying progression
was less advanced in No. 1510, 135 days postirradiation, than in No. 1514,
105 days after irradiation with the same dose. A different pattern of cutaneous
response was observed in B. brevicauda. Three of these shrews developed
erythema and epilation of their. backs during the month following irradiation.
One died 28 days after 875 rad, and another died after 142 days (690 rad)
with chronic, ulcerative dermatitis and abscesses associated with the epi-
lated area. Tapigmented hair appeared in the two epilated areas of the
remaining shrew (875 rad) and other patches of unpigmented hair developed
17 later, giving the animal a piebald appearance (Fig. 3), Iwo other shrews,
one receiving 780 rad and the other 690 rad, exhibited no graying after 250
and 255 days, respectively. Hamilton (1940) was of the opinion that molt in
B. brevicauda did not proceed in any conventional manner and that molting
21 could occur in a few days.
DISCUSSION
Intraspecific and interspecific comparisons of radiation effects in
captive mammals require careful consideration of a hyst of factors known to
influence radiation responses. We found differences in mortality, survival
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times, and weight changes among our experimental species, which were confined,
irradiated, and handled under similar conditions. However, we do not know to
what degree captivity stresses and other influences may have modified these
responses in each species. Specimens of wild species, even those born in
the laboratory, cannot be regarded as "domesticated" and react to handling
and caging differently from conventional laboratory animals. Sex, age,
temperature, diseases, parasites, fatigue, and diets are but a few of the
factors known to influence radiation-effects syndromes, and it would be
naive to assume that interactions of such factors with radiation were iden-
tical in all species.
Dose rate must be considered carefully in intraspecific and inter-
specific comparisons of mortality, survival times, and other irradiation
responses. At dose rates much below 100 rad/min, increasing amounts of radiation
were required to produce 50% mortality in mice in 30 days (Lindop and Rot-
blat, 1963). Dacquisto (1960) found that, even at 3 or 30 R/min, LD50-30
estimates differed in laboratory mice (743 vs 650 R, respectively) and
laboratory Fats (684 vs 498 R, respectively). Data by Logie et al. (1960):
for Sprague-Dawley R. norvegicus are particularly instructive on this point;
at dose rates of 0.176, 0.487, 3.41., 55, and 474 R/min, their LDer estimates
were 21.10, 1885, 1277, 1044, and 908 R, respectively. Consequently, com-
| parisons of our IDao estimates with the higher estimates of Golley et al.
(1.965), and Kellogg (1965) for certain species should be made with caution.
23. Dose rates in their experiments were 1.8-25.9 rad/min as compared with our
24 | 600-828 rad/min. Similarly, the radioresistance reported by Chang (1964)
for Meriones unguiculatus, should be viewed with knowledge that his dose rates
were 7.3-9 and 22 R/min (dose rates given by personal communication). The
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LD50 estimates of 1520 and 1300 R for two pocket mice, Perognathus longi-
membris and P. formosus, respectively, were obtained at a dose rate of 102
R/min (Gambino and Lindberg, 1964). It appears that these pocket mice are
comparatively radioresistant, even though another heteromyid rodent,
Dipodomys merriami, was relatively radiosensitive (Haley et al., 1960)..
All cricetids, except'o. palustris, examined so far seem to be more radio-
resistant than all murids or soricids studied to date.
Heterozygosity has been suggested repeatedly as a cause of increased
radioresistance. Rugh and Wolff (1958) suggested that heterosis resulted
in increased survival of C57 X CF, hybrids, compared with survival of the pure
strains. Work by Kohn and Kaliman (1965) with four inbred strains of mice
and reciprocal crosses of two of the strains also indicated increased radio-
resistance in the hybrids, but their IDEo estimate for wila M. musculus
was lower than all except the radiosensitive BALB/C strain. Of eighteen
strains used at ORNL, three were hybrids and were among the most radioresis-
tant of the strains (Davis et al., 1963). No significant difference is
apparent between LD o estimates of Golley et al. (1965) for wild house mice
and a strain of laboratory mice from crosses of four other strains. In our
experiment no significant difference was seen between RF-strain and wila M.
musculus males, and the RF females cageđ alone were more, not less, radio-
resistant than male or female wild house mice. It may be unfair to compare
results for wild species with data for domesticated inbred and hybrid animals
because of possible differences in captivity stresses between wild and domes-
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Rajewsky (1954) 'depicted a sigmoid curve for survival times of white
mice irradiated at doses 'from 250 to 200,000 R and pointed out that this.
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dose-survival curve can be divided into several dose ranges in which differ-
ent mechanisms of damage may predominaţe. It is well known that acute-radia-
tion death is not assignable to damage of one system or organ alone, but that
radiation-death syndromes actually result from complex organismal responses.
However, the multiple events preceding early irradiation deaths after doses
from about 500-10,000 rad usually follow more or less characteristic pat-
"terns, and these syndromes seem to be related primarily to cellular damage
in hemopoietic and gastrointestinal systems (Quastler and Zucker, 1959).
Rajewsky (1954) also showed that adrenal and pituitary glands are of decis-
Ive importance in terms of dose dependence and survival times in this dose
range.
The curvilinear nature of survival-time curves for our species indicates
13 taat survival times in the 1560-2060 rad range are on the first part of the
plateau wherein mortality times are independent of dose. The cricetids
| exhibited relatively long survival times in this. dose range, while the wild
murids and shrews had relatively short survival times. Since the gastro-
intestinal-death syndrome begins to predominate in this dose range, it may
be that basic differences exist in cellular differentiation or proliferation
19 rates in the GI tracts of these families. The ascending limbs of our curves
20 toward the lower doses cannot be projecteà very far beyond the ID-n estimates
because of the small number of animals dying and the increasing variability
of survival times in these few animals, but it is apparent that all LDGO
estimates lie in the dose ranges where the hemopoietic-death mode predomin-
ates in most laboratory rodents, Reductions in lymphocyte number, erythrocyte
number, hemoglobin concentration, and hematocrit percentages were much more
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rad (Dunaway et al. 1967).
4.1 Michaelson and Odland (1962) suggested that radiation recovery hall-time
and leukocytė depression time are inversely related to size of mammal and to
metabolic rate. In our study, body size and metabolic rate, even within
families, were not related to survival time, mortality, weight change, or
other radiation effects 'observed.
Differences in patterns of weight changes in the various species may
10 reflect, at least in part, differences in captivity stresses and/or fat
11 accumulation. For example, controls oz the two irradiated groups that lost
most weight (RF-strain M: musculus caged' alone and in groups) consistently
13 gained weight. Controls of wild, singly-caged M. musculus also gained weight,
14 at least during the first two weeks, and irradiated individuals lost considera
ble weight.
The RF mice have been domesticated for many generations, of course,
16 and house mice commonly live in proximity to man: such animals may experience
17 less captivity stress. Irradiated golden mice were the fourth group that lost
18 much weight;. controls of these animals were slow-moving, generally inactive, and
19. gained weight. Although accumulation and loss of stored fat was not measured
20 in this experiment; it may be that much of the weight loss in irradiated an-
21 imals reflects fat loss. Furthermore, it is possible that survival time of
22 fat animais may be longer than for animals with little fat. Obesity was mark-
23 edly more common in golden mice than in any other species, and P. nuttalli
24 had the longest survival times of all species tested. Ershoff (1960) found
25 considerably shorter survival times in mice on low-fat diets compared with
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..
.
.
.
14
.
4
lir
ht
..
mice receiving rations supplemented with cottonseed oil, desiccated liver, on
methyl lineolate.
Results of experiments in which animals are caged singly or in groups
should be evaluated carefully. Raventos (1955) reported a cage effect but
found no significant differences in mortality between irradiated mice caged
singly and those caged together, in contrast to our higher LDe estimates for
singly-caged female RF mice and the similar results of Hahn and Howland (1963)
for female Wistar rats. However, designs of crowaing-stress experiments have
varied. . We kept randomly-selected individuals together (5 per cage) for one
week prior to irradiation and did not redistribute survivors after irradia.
11 tion to maintain group numbers. Hahn and Howland used animals from a corner-
cial supplier, assigned 1, 2, 4, or 6 randomly-selected rats per cage 4 to 5
:13 days before irradiation, and recombined survivors to maintain constart numbers
14 per cage. Raventos used mice from a supplier, put one or ten individuals in
a cage, daily shuffled groups of mice caged together, did not shuffle other
16 groups of mice caged together, and did not recombine survivors; he warned,
bowever, that "... there were construction differences between the individual
and the group cages which must have produced environmental differences."
It is well known that, in general, less fighting occurs among litter
mates of the same sex kept together than between recently-combined groups
21 from different litters, and fighting is more severe in a group during es-
22 tablishment of a social hierarchy than after dominance-subordinance rela-
23 tionships have been established. Brown and White (1958) showed that mortal-
ity is less and survival times longer in rats fatigued and then irradiated
25 than in rats irradiated and then fatigued or even in rats receiving no treat-
26 ment except irradiation. Even sexual activity caused drastis increases in
YON.8867
*
mortality of irradiated mice (Rugh and Grupp, 1960). Consequently, fighting
or other social stresses prior to or after irradiation may affect the outcome
of crowding-stress experiments. Temperature may be important in such experi-
ments, but laboratory or colony-room temperatures are not specified in many
reports.. At temperatures below thermoneutrality.for a given species, grouped
animals may be at an advantage because of better heat retention in hudaling
groups. Shipman and Cole (1966) indicate the care that must be exercised in
evaluating modifications of radiation effects by environmental stressors: :
"... tiie constellation of nonspecific neuro-endocrine reactions to a stress
which Selye has termed the adaptation syndrome, is very complex, and is not
easily amenable to quantitative measurement; it is likely that the degree
of stress', and its timing relative to radiation exposure, are critical de-
terminants as to whether the elicited response is radioprotective, or indeed
deleterious."
Radiation effects such as conjunctivitis, ataxia, agressiveness, and
pelage graying probably would make affected small mammals more vulnerable
to predation. This aspect may be almost aca emic, since doses of the magni-
tude required to produce these effects may sterilize these animals. On the
other hand, selective removal of such sterilized individuals by predators
may reduce intraspecific competition and predator pressure on the less-
affected members of the populations.
The comparative radiosensitivities reported here for wild small mammals
in the laboratory. are useful for planning fieid experiments, and certain
findings may be provocative to laboratory radiobiologists. An observation
that arises from comparisons of relevant radiobiological and radioecological
UCN. $607
16
i
..
when
reserch 1s that radiobiologists need to be aware of pertinent ecological inf.
formation (e.g., population-density studies) and radioecologists should be
cognizant of pertinent radiobiological findings (e.g., dose-rate effects).
Extensive ecological and radiobiological knowledge is available, and perhaps
such information can be joined for rough, first-approximation predictions,
but only research with actual populations in irradiated environments will
provide data needed for predicting consequences of ionizing radiation in
Large ecological systems. Successful descriptions of holoecological respon-
ses to irradiation will require: (1) natural environments subjected to con-
trollable or uniform radiation, (2) adequate laboratory and field instrumen-
tation, and (3). concerted, cooperative efforts by large teams of investigators
representing many disciplines. These requirements are yet to be fulfilled.
.
.
.
UCN-8867
ma
...
...
17
.
"..
1
1
.
- LITERATURE CITED...
Brown, W. L., and R. K. White. 1960. A study of fatigue and mortality in
Irradiated rats. Rad. Res. 13:610-616.
Chang, M. C., D. M. Hunt, and C. Turbyfill. 1964. High resistance of mongol-
:: lan gerbils to Irradiation. Nature 203:536-537:
Chase, H. B. 1949. Greying of hair. I. Effects produced by single doses of
X-rays on mice. J. Morph. 84:57-80.
Dacquisto, M. P., and E. W. Blackburn. 1960. The influence of delivery rate
5. Of whole body 250 Kv roentgen irradiation (30 or 3 roentgens per minute)
on mice, rats and guinea pigs. Amer. J. Roentgenol. 84:699-704.
Davis, M. L., G. E. Cosgrove, and D. Gö Gosslee. 1963. X radiation doses i
and mortality in mouse strains used in transplantation experiments in
thė Biology Division. ORNL-CF-63-2-17. ..
Dunaway, P. B., J. D. Story, J. T. Kitchings, III, L. E. Tucker, L. L. Lewis,
C. Koh, and C. M. McConnelli 1967. Radiation effects in blood of in-
* digenous small mammals. In Health Phys. Div. Ann. Prog. Rept. July 31,
1967 (in press).
18 Ershoff, B. H. 1960. Effects of low-fat diets on survival time of mice ex-
posed to multiple sublethal doses of total-body X-irradiation. Rad.
Res. 13: 704–71.1.
Gambino, J. J. and R. G. Lindberg. 1964. Response of the pocket mouse to
ionizing radiation. Rad. Res. 22:586-597.
Golley, F. B., J. B. Gentry; E. F. Menhinick, and J. I. Carmon. 1965. Response.
...of wild rodents to acute gamna radiation. Rad. Res. 24:350-356.
.
.
CN8867
(3 6.60)
.
.
?

+
it
yo
4
.
PL 1!
.
.
Te
.
L
*
.
1
'
.
.
*
ht
'
Ti.
..
.
-1.
123
.
.!
vo
-
.
.
Hahn, E. W., and T. W. Howland. 1963. Modification of irradiation response of
2 female rats by population density. Rad. Res. 19:675-681.
Haley, T. J., R. G. Lindberg, A. M. Flesher, K, Raymond, W. McKibben, and
P. Hayden. 1960. Response of the kangaroo rat (Dipodomys merriami
Mearns) to single whole-body. Irradiation. Rad. Res. 12:103-111.
121, E. R., and K. R. Kelson. 1959. The mammals of North America. Ronald
Press, New York, 2v, 1083 p.
Hamilton, W. J., Jr. 1940. The molt of Blarina brevicauda. J. Mammal. 21: ,
1 457-458.
10 Kellogg, F. E. 1965. Determination of the cobalt-60 LD60(20) for the wild-
caught cotton rat (Sigmodon hispidus). unpublished M.S. thesis, .
University of Georgia, Athens. 30 p.
Kohn, H. I., and R. F. Kallman. 1956. The influence of strain on acute x-ray
lethality in the mouse. I. ID. and death rate studies. Rad. Res.:5:
15 ... 309-317.
.':.:.:
Lindop, P., and J. Rotblat. 1963. Dependence of radiation-induced life-
shortening on dose-rate and anaesthetic, in Cellular Basis and Aeti-
18 nology of late Somatic Effects of Ionizing Radiation, p. 313
(Academic Press, New York).
Logie, L. C., M. D. Harris, R. E. Tatsch, and E. N. 'Van Hooser. 1960. An
analysis of the · LD50(20) as related to radiation intensity. Rad. Res.
22 . 12:349-356. .
:
23 Michaelson, s. M. and L. T. Odland. 1962. Relationship between metabolic rate
L and recovery from radiation injury. Rad. Res. 16:281-285. .
25 Quastler, H. and M. Zucker. 1959. The hierarchy of modes of radiation death
- in specifically protected mice. Rad. Res. 10:402-409.
I
..
•
!...
.
UCN-8867
3 6 66)
..
..
*Rajewsky, B. 1955. Radiation death in mammals, in Radiobiology Syir.posiun
P. 81 (Butterworths Scientific Publications, London).
Raventos, A. 1955. A factor influencing the significance of radiation
: mortality experiments. J. Radiol. 28:410-414.
Rugh, R., and E. Grupp. 1960. X-irradiation lethality aggravated by sexual
activity of male mice. Amer. J. Physiai. 198: 1352-1354.
Rugh, R., and T. Wolff. 1958. Increased radioresistance through heterosis.
.Science 1278 144-145.
Shipman, W. H., and L. J. Cole. 1966. Increased radiation resistance of mice
injected with bee venom one day prior to exposure. USNRDL-TR-67-4.
8
..
.
....
.....
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.
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.
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.
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.
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.
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.
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-
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.
.
ha
O
-
Table I. IDEO 20 Estimates for eight species of indigenous rodents, one strain
of laboratory mouse, and two species of shrews...
:
PE
!
it
X
M1
.
.
Total no.
individuals
LD 50-30
axon
he
(rad)
YE.
_
*
i-
Cricetidae
Im;
Reithrodontomys humulis
.
.
:
U
.
See
826-1015
924-1092
901-1002
Both sexes
138
2
.
'1
Peromyscus leucopus
po
od
Both sexes
1043
1091
1069
976-1111
1029-1168
1026-1115
.
Peromyscus nuttalli
99
1076
919
999
970-1206
743-1020
918-1071
..
..
...
Both sexes
Microtus pinetorum
1004
883
939
890-1168
772-983
865-1019
.
.
Both sexes
r
.
-
+
.
.
.1.
Oryzomys palustris
.
I-
:.:
.
480
348-551
A
.
.
584.
435-748
Both sexes
443-590
Sigmodon hispidus
950
000
966
958,
885-1037
901-1078
914-1013
Both sexes
...
Muridae .'
Mus musculus
Wild.
: 1 in cage
99
016
!
701-880
774-920
772-877
Both sexes
..
-
U
+.
L
.
U
.
.
.
L
...
.
.
L
..
.
.
-
-
-
-
-
-
Table 1. (continued)
Total no..
individuals
Taxon
1150-30
(rad)
95% SL
1
-
i
.
-
5 in cage
-.
-
.
99
00
Both sexes
659-928
751-900
755-861
.:
RF strain
i in cage
::
otot
Both sexes
5 in cage :
973-1145
784-979
894-1080
ii
581-860
703-976
694-860
1.725.
-.
II
.
.
..
.
Both sexes
Rattus norvegicus
1:29
oot
Both sexes
771-918
833-1069
739-989
Soricidae
Cryptotis parva
09
644-956
473-2106
634-1174
Both sexes
Blarina brevicauda
662-945
oo
Both sexes
593-981
...
.
.
667-904
.
.
.
.
i
:
..
.
..
.
..
-
-
-
.
.
.
:-*
.*.*
**.
tw
-
-
-

Table II. Weight losses at death of rodents and shrews in selected dose groups. 'Heights of control groups
are averages at day of irradiation. Values for irradiated groups are percent of weight remaining for the
respective groups from day of irradiation.
Contrcl
: Dose (rad)
Weights (g) 860-920 1030-1100_ 1200-1300 - 2560-1660 1890-2000
Cricetiäae
. Reithrodontomys humulis 8.3 78.3 + 3.44 : 80.3 + 3.45 82.4 * 3.37 81.14 2.89 85.2 + 4.00
Peromyscus leucopus 19.8 * - 78.5 * 4.30 84.5 2.82 . 84.9 + 2.59 83.3 * 2.24
Peromyscus nuttalli 26.6 83.8 + 3.82 80.0 + 3.63 - 69.3 2.34 72.0 + 2.04 72.9 * 2.26
Microtus pinetorum 30.6 79.2 + 2.55 85.4 = 4.33 .70.9 2.65 75.1 2.97 78.6 2.04
Oryzomys palustris 52.1 79.7 + 1.72 78.8 * 1.51 77.8 + 0.98 79.7 2.07 85.6 1.29
Sigmodon hispidus 118.2 81.6 £ 4.36 80.9 * 1.96 78.8 * 3.21 75.8 * 1.87 :77.6 1.54
Muridae
Mus musculus
.
:
:
.
Wild
1 per cage
18.7
15.4
77.5 # 3:53
76.0 £ 3.13
68.2 + 2.82
71.1 + 1.60
74.7 + 3.27.
71.5 £ 2:27.
76.3 * 1.93
69.6 3.79
82.3 = 2.01
.65.6 + 1.77
...
5 per cage
1
.
RF Strain
.
I per cage
66.6 1.90
29.2
30.4
238.7
69.8 3.6761.9 1.83
73.2 1.92 72.4 3.32
72.0 £ 2.00 74.2 £ 1.41
68.2 + 1.68
69.2 + 2.52
77.8 2.01
3.0
5 per cage
Rattus norvegicus
Soricidae
+
1.90
67.4 £ 1.56
69.6 * 2.07
80.3 + 1.41
...........
8 1:3 1.75
....
..
;
Cryorotis parva,
S
3.6
26.5
79.0 + 0.98
83.8 + 4.81
76.1 £ 2.63
90.8 + 2.65
71.8 + 4.89
67.0 * 3.84
78.6 $ 1.17
77.4 + 5.25
76.5 + 1.52
76.4 + 0.37
'ini!...
Plarina brevicauda.
A
fostudom.
* Less than three animals died
21
.
.
.
.
.
.
-
-
-
FIGURE CAPTIONS
FIO
Survival times of rodents and shrews. Curves are projected only
to lowest doses at which three or more individuals died. Vertical
bars indicate ID50_20 estimates.
FIGURE 2. Graying in Peromyscus leucopus irradiated with 1070 rad. A. Unir-
radiated control. B. No. 1510, 135 days postirradiation. C. No.
1514, 105 days: D. No." 1514, 215 days.
FIGURE 3. Graying in a Blarina brevicauda (No. 1531) irradiated with 8.75
rad. A. Unirradiated control. B. 92 days postirradiation. C. 202
days postirradiation. 1:
-
.
,
..
.
.
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ORNL-DWG 67-4744
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-

1
.
2
.
.
Ñ.
SURVIVAL TIME (days)
Ô
0
0
CRICETIDAE
...... REITHRODONTOMYS HUMULIS
-.- PEROMYSCUS LEUCOPUS
teki PEROMYSCUS NUT TALLI
---MICROTUS PINE TORUM
-- ORYZOMYS PALUSTRIS
SIGMODON HISPIDUS
te
E SORICIDAE
CRYPTOTIS PARVA
BLARINA BREVICAUDA
- ..
.
.
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Ñ .
SURVIVAL TIME" (days)
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0.
0
MURIDAE
MUS MUSCULUS
WILD
Dr.... 4 PER CAGE
..-...-5 PER CAGE
RF STRAIN
tofanskap 1 PER CAGE
- 5 PER CAGE
RATTUS NORVEGICUS
• •
•
400
600
80
800
1000
: 1400
1200 .
DOSE (rad)
1600
: 1800
2000
1
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END



DATE FILMED
10 / 31 / 67








2
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