Lung carcinogenesis in rats after inhalation exposure to (237)NpO2.

The results of several studies of experimental carcinogenesis suggest that, after inhalation of alpha-particle emitters, lung tumor incidence varies depending on the exposure rate and dose distribution in the tissue. In the case of transuranics, the main influencing factor would be the specific alpha-particle activity of the inhaled actinide. To confirm these results, long-term studies were performed using male Sprague-Dawley rats exposed to (237)NpO(2) by inhalation. The initial lung burdens of the animals ranged from 0. 1 to about 7 kBq. The rats were followed during their life span and weighed regularly, and their lung burdens were determined in vivo and at death to estimate the lung dose. At death, the incidence of lung tumors and their malignancy and histological types were analyzed. The analysis revealed a typically linear-quadratic dose response for incidence of malignant lung neoplasm and a differential dose response for various types of tumors. Although these results confirm the influence of the activity of the inhaled actinide oxide, further experiments are needed to be able to compare a more homogeneous population of animals.

Localization of plutonium retention in the small intestine of the neonatal rat, guinea pig, baboon and macaca after Pu-citrate ingestion.

The retention of Pu-citrate in the gastrointestinal wall was compared at similar post ingestion times after ingestion at 2 days of age by rats and guinea pigs and at 1 to 34 days by neonatal primates. The small intestine was the main site of the Pu retention in all species. In rats and primates, most of the Pu was retained in the distal ileum, whereas in guinea pigs it was more homogeneously distributed. In the rats, Pu was retained in the epithelial cells on villi, but in the guinea pigs and primates it was confined to the macrophages under the epithelial cells in the lacteal region.

[Consequences of pulpectomy followed by canal obturation on the renewal of periodontal ligament in the baboon (Papio papio)]. / Conséquence d'une pulpectomie suivie d'obturation canalaire sur le renouvellement du desmodonte chez le Singe Babouin (Papio-papio).

Endodontic root filling following pulpectomy in Baboons was shown to induce diphasic consequences at the level of the periodontal ligament according to the time of the observation. Initially the specific activity of previously incorporated 3H Glycine decreased and the weight of extractible ligament increased at the same time. Later on, the turnover slowed down and, unexpectedly, the weight of the extractible ligament decreased. This could be explained since the periodotal ligament was shown to exhibit a transient inflammatory reaction followed initially by a tissue accretion and progressively by a partial amputation of the ligament volume compensated by an excess of bone deposit on the surface of the alveolar bone socket.