No abstract available

[en] When considering which laboratory animal species to use in inhalation studies, it is important to evaluate the similarities and differences in deposition and fate of the inhaled materials in various laboratory animals compared with humans. Beagle dogs have deposition and clearance patterns of inhaled particles similar to humans. However, some studies require smaller laboratory animals to be cost effective or to allow an adequate number of animals to address the scientific questions. This study evaluated the deposition and clearance of a relatively insoluble aerosol inhaled by guinea pigs. The test aerosol was monodisperse ¹³⁴Cs-labeled fused aluminosilicate particles inhaled during 75 minute inhalation exposure. The guinea pigs had deposition similar to rats but respiratory tract retention and clearance patterns were similar to dogs and humans. 5 references, 2 figures, 1 table

[en] Beagle dogs and guinea pigs were used in inhalation studies to provide comparative data for deposition and fate of inhaled ¹³⁴Cs-labeled fused aluminosilicate particles (¹³⁴Cs-FAP). Results from tissue and excreta analyses for ¹³⁴Cs at various times after exposure were used to produce simulation models which accounted for the fate of the inhaled ¹³⁴Cs-FAP. These models, as well as results from a recent human experiment with radiolabeled FAP, were used to make projections for lung and lung-associated lymph node burdens in chronically exposed people. Results indicated that retention patterns for trace amounts of particles were comparable for Beagle dogs and guinea pigs. Both species may be useful in laboratory investigations directed to understanding the mechanisms of particle clearance in people. 4 references, 2 figures, 1 table

No abstract available

[en] A biological effects study has been initiated in which Syrian hamsters have been repeatedly exposed by inhalation to ¹⁶⁹Yb-labeled ²³⁹PuO₂ to reestablish lung burdens of 2, 10 or 50 nCi of ²³⁹Pu at 60-day intervals. Control Syrian hamsters have been either nonexposed, or exposed once or repeatedly exposed to stable Yb₂O₃ or ¹⁶⁹Yb₂O₃ to achieve an initial lung burden of 50 nCi ¹⁶⁹Yb. Additional Syrian hamsters have been exposed once to ¹⁶⁹Yb-labeled ²³⁹PuO₂ to achieve initial lung burdens of 2, 10 or 50 nCi of ²³⁹Pu. All scheduled exposures have been completed. Preliminary observations indicate the cumulative percent survival has been shortened only in the Syrian hamsters repeatedly exposed to reestablish lung burdens at 50 nCi. There has been no evidence of pulmonary tumors in animals that have died through 460 days after initiation of the study. A similar study has been initiated in mice

[en] Guinea pigs were given a single nose-only inhalation exposure to monodisperse ¹³⁴Cs-labeled fused aluminosilicate particles having a 2.0 μm activity median aerodynamic diameter. Amounts of ¹³⁴Cs in bodies, excreta and tissues were determined as functions of time after exposure. The emphasis of the study was on pulmonary retention and translocation of ¹³⁴Cs from the pulmonary region to the mucociliary escalator and lung-associated lymph nodes. Results to 384 days after exposure showed a long-term effective half-time of ¹³⁴Cs in the pulmonary region of approximately 280 days. Particles were translocated to lung-associated lymph nodes at a rate of 0.00003 of the lung burden per day. Retention and fate of these particles in guinea pigs were similar to what is observed in short-term studies for these particles inhaled by humans. Guinea pigs might provide a useful model for projecting the deposition and retention patterns for materials inhaled by humans. 4 references, 3 figures

No abstract available

[en] The effects of protracted beta irradiation of the lungs of rats are being studied. Rats were exposed seven times at 60-day intervals by inhalation to aerosols of ¹⁴⁴CeO₂ to re-establish lung burdens of 0.04, 0.20, 1.0 or 5.0 μCi of ¹⁴⁴Ce. These rats are being compared with rats exposed once to ¹⁴⁴CeO₂ to achieve similar initial lung burdens of ¹⁴⁴Ce. Repeated exposure to ¹⁴⁴CeO₂ resulted in about a fivefold increase in the radiation doses to the lungs compared with rats exposed once to achieve similar lung burdens of ¹⁴⁴Ce

No abstract available

[en] Syrian hamsters have been repeatedly exposed by inhalation to ¹⁶⁹Yb-labeled aerosols of ²³⁹PuO₂ to compare the resulting biological effects with those after a single exposure. Groups of Syrian hamsters have been repeatedly exposed to ²³⁹PuO₂ to reestablish lung burdens (LB) of 2, 10 or 50 nCi ²³⁹Pu during the first 12 months after the initial exposure. Control Syrian hamsters were either unexposed or exposed once or repeatedly to stable Yb₂O₃ or ¹⁶⁹Yb₂O₃. Repeat inhalation exposure to ²³⁹PuO₂ has resulted in a 2.4- to 7.2-fold increase in the radiation dose (rads) to lungs of the hamsters in this study compared with those exposed once at the same level. Preliminary histological findings include only one bronchioloalveolar tumor which was in a repeatedly exposed hamster