Food intake and growth of burro foals after 250 roentgens of cobalt-60 whole-body gamma irradiation

Possible late effects of sublethal levels of whole-body gamma irradiation on growth of burro foals were studied. Two trials included 31 nonirradiated foals and 32 foals that were exposed to 250 R of 60Co gamma radiation during their fourth month of life. The foals were weaned 90 days postirradiation and allotted into treatment groups based on radiation treatment, weight, sex, and size. Each group was then randomly selected to be fed a ration containing either 9 %, 14 %, or 18 % crude protein in the first trial and either 9 % or 18 % in the second trial. The length of these trials was 364 days. Criteria used to evaluate the treatments included feed consumption, body weight gains, feed efficiency, increase in height, and increase in heart girth. Least-squares analysis of these data indicated that radiation had no significant effect on any of the traits tested. There was a consistent though nonsignificant trend for irradiated foals to be less efficient in feed utilization than their nonirradiated counterparts.     

Histological changes in rat duodenum mucosa after whole-body gamma irradiation.

In order to understand the mechanisms of intestinal injuries due to ionizing radiation, various groups of rats have been whole-body irradiated by gamma-rays at two dose rates (1 Gy/min and 1 Gy/hr), three doses (1, 2 and 4 Gy) and two post-irradiation times (24 and 48 hr). Duodenum samples of the animals were prepared for light microscopy, according to classical methods for histology and TUNEL reaction. A small number of morphological differences were observed within the mucosa between the two dose rates used. The extent and the number of lesions were more important at the slower dose rate (1 Gy/hr) and increased with the total dose. Clear cavities were seen inside the lamina propria which appeared like capillaries free of blood cells. The mitotic index calculated from crypt cells showed a regular decrease with the dose, which was exacerbated at 48 hr post-irradiation. On the other hand, the apoptotic index increased with the dose and the postirradiation time. Our results lead to hypothesize another mechanism of intestinal mucosa renewal allowing to explain mucosa denudations observed after radiotherapy. Thus we propose a new concept in which the duodenal mucosa renewal may occur by whole villi shedding into the duodenal lumen.     

The effect of perinatal 60Co gamma radiation on brain weight in beagles

Beagle dogs were given single, whole-body 60Co gamma-radiation exposures at one of three prenatal (8, 28, or 55 days postcoitus) or three postnatal (2, 70, or 365 days postpartum) ages to evaluate the relative radiosensitivity of various stages of brain development. A total of 387 dogs received mean doses ranging from 0.16 to 3.83 Gy, and 120 dogs were sham-irradiated. Groups of dogs were sacrificed at preselected times from 70 days to 11 years of age. Brain weight decreased significantly with increasing dose in dogs irradiated at 28 or 55 days postcoitus or at 2 days postpartum. Irradiations at 28 days postcoitus were dramatically more effective in causing a reduction in brain weight than those at 55 days postcoitus or 2 days postpartum. Among dogs given 1.0 Gy or more and followed for up to 4 years, there was a radiation effect evident at all three sensitive exposure ages. Among dogs given lower doses and followed for up to 11 years, there was a significant decrease in brain weight in dogs given 0.80-0.88 Gy at 28 days postcoitus. All decreases in brain weight were present after normalization for radiation-induced reductions in skeletal (body) size. No specific morphologic changes were noted in the brains which showed the radiation-related reductions in size.     

Blood-brain barrier permeability after gamma whole-body irradiation: an in vivo microdialysis study

The effects of total-body irradiation on the permeability of rat striatal blood-brain barrier (BBB) to [3H]alpha-aminoisobutyric acid (AIBA) and [14C]sucrose were investigated using the microdialysis technique. Seven days, 3 and 6 weeks, and 3, 5, and 8 months after gamma exposure at a dose of 4.5 Gy, no modification of the permeability to both [3H]AIBA and [14C]sucrose was observed. But, in the course of the initial syndrome, we observed a significant but transient increase in the BBB permeability to the two markers between 3 and 17 h after exposure. A secondary transient "opening" of the BBB to [14C]sucrose was noticed about 28 h following irradiation without the corresponding increase in BBB permeability to [3H]AIBA. On the contrary, the transport of [3H]AIBA through the BBB was decreased between 33 and 47 h postradiation. In conclusion, our experiments showed early modifications of BBB permeability after a moderate-dose whole-body exposure. Confirmation of these results with other tracers, in another experimental model or in humans, would have clinical applications for designing appropriate pharmacotherapy in radiotherapy and treatment of accidental overexposure.     

Changes of lipofuscin-like pigments in erythrocytes and spleen after whole-body gamma irradiation of rats

Whole-body gamma irradiation of rats induced the formation of lipofuscin-like pigments in erythrocytes. Erythrocytes that were damaged by oxidation were scavenged in the spleen, and lipofuscin-like pigments were transferred from erythrocytes to the spleen during this process. The time course of lipofuscin-like pigments in erythrocytes and spleen indicates that the pigments were not induced by the action of free radicals produced by ionizing radiation but rather were a sequela of postirradiation metabolic changes.     

Haemopoiesis in the beagle foetus after in utero irradiation

On day 33 of gestation, foetal beagles were irradiated in utero (0.9 Gy of 60Co gamma-irradiation, 0.4 Gy/min). Foetal haematocytopoiesis was studied during the third trimester of gestation (days 42-55). Peripheral blood nucleated cell counts were 33 per cent lower than normal on day 44 and continued to be lower until day 49, when values became higher than normal. Splenic cellularities of irradiated pups on day 44 were more than 3 times those of the nonirradiated, but thereafter they were similar to normal. Differences in haemopoietic progenitor cell activity between irradiated and normal foetuses were observed. In comparison with the other foetal tissues, the foetal liver appeared to experience greater radiation injury. For example, on day 44, the irradiated liver BFU-E, CFU-E, and GM-CFC per 10(5) cells were almost fivefold lower than normal values. Spleens of irradiated foetal beagles contained a marked increase in all haemopoietic progenitor cells (BFU-E, CFU-E, and GM-CFC) and recognizable proliferative granulocytic cells and nucleated erythroid cells. The haemopoietic activity of the irradiated bone marrow during days 42-44 was similar to that of the irradiated spleen, and compensated for the damaged liver. However, unlike the irradiated spleen, the irradiated bone marrow had decreased BFU-E activity compared with the values for the nonirradiated bone marrow during days 48-55. Until day 50, the irradiated marrow contained fewer recognizable proliferative granulocytic cells but more nucleated erythroid cells.