Howard H. Vogel

The effect of streptomycin therapy on mice irradiated with fast neutrons.

In a recent communication (1) it was shown that the mortality of mice after acute fast neutron irradiation was closely correlated in time with the development of generalized infection as demonstrated by the recovery of enteric bacteria from hearts blood and/or spleen. Such positive cultures were first obtained on the fourth day post-irradiation, coinciding with the onset of mortality. Between the fourth and the eighth days after exposure, the period of maximum mortality, approximately 40 % of the sacrificed mice showed positive cultures. It seemed to be established, therefore, that generalized infection, including invasion of the blood stream, occurred in mice after a single acute irradiation with fast neutrons. The present series of experiments was designed to determine the effect of streptomycin therapy on the mortality of neutron-irradiated mice in order to evaluate the importance of infection as a cause of death. Streptomycin was chosen because it had been found to be the most effective of the antibiotics used in the treatment of mice exposed to X-rays (2).

Neutron irradiation of late mouse embryos (15-19 days) in utero.

Pregnant female C57B1/6 mice were irradiated with a single whole-body dose of 0.5 Gy neutrons. The F1 hybrid embryos were exposed to the neutrons in utero on Day 17 +/- 2 of gestation. 178/439 (40.6%) of the irradiated fetuses and 26/217 (12%) of the control mice died within 2 weeks after birth. In both irradiated and control mice, most deaths (95 and 77%, respectively) occurred within 3 days of birth: most animals in both groups died on Day 2. There was no significant difference in the number of living young born per litter (7.2) between the neutron-irradiated mothers and their unirradiated controls. The irradiated mice weighed significantly less than their controls. On the first day after birth, body weights of mice irradiated in utero averaged only 85% of control weights. Body weights did not reach control levels until 6 months after birth. Several organs were weighed at regular intervals in both irradiated and control mice. Spleens and thymus glands showed no significant differences between the two groups. The livers and kidneys of the irradiated mice weighed slightly less than their controls. The brain weight of 21-day-old neutron-irradiated mice was 30-35% less than control brains. The weight loss of the brain was not only a relative loss, but also an absolute one, based on brain weight/body weight ratios. Histological analysis of the central nervous system showed pycnotic nuclei, inhibition of mitosis in neuroblasts, and cell death in the irradiated brains. The weight reduction of the brain was not due to water loss. Our hypothesis is that the early mortality after birth is related to the killing of the radiation-sensitive neuroblasts. When newborn mice (1-7 days old) were irradiated in vivo with the same neutron dose of 0.5 Gy, neither the reduction in brain weight nor the early mortality was observed. The early deaths of the neutron-irradiated mouse embryos does not appear to be caused by either the hematological or the gastrointestinal radiation syndrome.

Cocarcinogenesis: the interaction of chemical and physical agents.

The physical agent used in this study was fission neutrons (300-360 rads). The chemical carcinogen was 2,7-FAA, injected intraperitoneally for 23 weeks, total dose: 414 mg. The aim of this experime...

Comparative Mortality Following Single Whole-Body Exposures of Mice to Fission Neutrons and Co60 Gamma Rays

During the past several years experiments have been planned and undertaken to test the radiobiological additivity of fast neutrons and Co60 gamma rays in their acute lethal action on mice (1). Since high-energy gamma rays and fission neutrons are often encountered together, the question of whether they are additive in producing certain biological effects has practical as well as theoretical significance. As a basis for these studies, complete dose-survival curves for the mouse were constructed following exposure to each of the two radiations alone. The object of this paper is to present these survival data for the thirty-day acute period following such exposures. Material and Methods Animals: The mice used in these experiments were CF #1 females, shipped to our Laboratories at five to six weeks of age. Upon arrival each week, they were divided into groups of eight, by means of a table of random numbers. Each group was housed in a plastic cage (2) and placed in isolation for two to four weeks before being ...

Genetic component in rat mammary carcinogenesis

Five genetically defined strains of female rats were exposed to whole-body radiation with a single dose of 50 rad of fission neutrons. After 1 year 56% of the Long-Evans and Sprague-Dawely strains showed at least one mammary tumor; 25-29% of the Buffalo and Fischer-344 strains and only 5% of the Wistar-Lewis strain and palpable mammary tumors. Only one tumor was found among 73 unirradiated controls during the 1-year observation period. Approximately two-thirds of 50 mammary analyzed pathologically were adenofibromas and fibroadenomas; one-third were adenocarcinomas. The Kaplan-Meier method of life table analysis was used to deal with the problem of intercurrent mortality. A genetic factor seems evident in rat mammary tumorigenesis following exposure to fission neutrons.

The Effect of Variations in LET and Cell Cycle on Radiation Hepatocarcinogenesis

The effect of variations in LET and cell cycle on radiation carcinogenesis was studied in

The effects of dose rate variation of fission neutrons and of Co60 gamma-rays on survival in young chicks.

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Life-Shortening in Mice Irradiated With Either Fission Neutrons or Cobalt-60 Gamma Rays

mouse liver. Our results are consistent with those of Cole and Nowell in that both the quality (LET) of the radiation and the addition of a proliferative stimulus significantly alter the hepatocarcinogenic endpoint. A single, whole-body, 200-rad dose of137 Cs gamma rays increased the hepatoma incidence by approximately 3- to 4-fold over the control rates, when a pure proliferative stimulus (partial hepatectomy) was added. Also a single, whole-body, 200-rad dose of fission neutron irradiation increased the hepatoma incidence by approximately 6 -to 9-fold over the control rate, when combined with partial hepatectomy. Furthermore, both the137 Cs and fission neutron hepatocarcinogenic rates were enhanced regardless of whether the irradiation was given either during liver regeneration or 8-13 weeks prior to partial hepatectomy. However, neither137 Cs nor fission neutron irradiation alone (i.e., ...

Relative Biological Effectiveness of Fast Neutrons, Gamma Rays, X-Rays on Grasshopper Nymph Ovarioles. (Melanoplus differentialis)

It has been shown that survival of young birds after X-radiation is dependent on the total dose, the dose rate, and the age at the time of exposure (1). It seemed of interest to determine whether the dependence of death on dosage rate would be found when birds were exposed to radiations of different specific ionization. Survival studies, following fast neutron exposures of CF No. 1 female mice, have shown that the 30-day LD50 (210 rep) did not change significantly when the neutron dose was delivered in 1.5 or in 24 hours, a sixteenfold change in dose rate (2). On the other hand, similar exposures to y-rays showed a definite dose rate dependence. This investigation includes: (1) observations on survival of young chicks exposed to fast neutrons and to y-rays at different dose rates; (2) the estimation of the relative biological effectiveness (RBE) of these two ionizing radiations in causing lethality in the chick.

THE RELATIVE BIOLOGICAL EFFECTIVENESS OF CO

During the past decade the Neutron Toxicity Group has been investigating the biological effects of fission neutrons and Co60 gamma rays on a variety of organisms (1). During the early years of the program, efforts were devoted largely to the study of the acute effects of single exposures of neutrons and gamma rays on mammals (2). The problem of lack of additivity of the two types of radiation was investigated; different modes of mortality were found following each, in mice, and different mechanisms of death were postulated (3). The present experiments were carried out at the CP-5 research reactor to compare the results of earlier acute studies with those at lower dose levels. They were undertaken to evaluate the effects of a series of brief fractionated exposures ranging from the 30-day acute dose of both fission neutrons and Co60 gamma rays, through the subacute area, to low total-dose levels. Such information will be useful in planning experiments in which animals will be exposed for the length of their...