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Biomedical subjects

R O McClellan

Publications and source records attributed to R O McClellan.

At least 109 records · Page 6Linked to original sources
PubMed1979

Nasal carcinomas in beagles after inhalation of relatively soluble forms of beta-emitting radionuclides.

Beagles were exposed by inhalation to relatively soluble forms of single beta-emitting radionuclides and are being held for life-span observation to evaluate biologic hazards associated with nuclear power production. The dogs were exposed to graded activity levels of 91YCl3, 144CeCl3, or 90SrCl2. With 91YCl3 and 144CeCl3, a significant radiation dose was delivered to the respiratory tract, liver, and skeleton. With 90SrCl2, the dose was almost totally to the skeleton. Squamous cell carcinomas associated with the nasal cavity have been the most frequently observed neoplasms in the 91YCl3 study and one of the most frequent in the 144CeCl3 study, whereas few squamous cell carcainomas have been seen in the 90SrCl2 study. One hemanglosarcoma in the nasal cavity was also seen in the 144Ce study. The incidence of nasal carcinomas may be related to higher relative concentrations of the radionuclides 91Y and 144Ce associated with the nasal turbinates. This relatively high risk of nasal cavity neoplasms suggests that standards for human exposure to these radionuclides should included a consideration of the nasal cavity epithelium as a major target tissue.

Air Pollutants↗
PubMed1975

Prevention of radiation pneumonitis from inhaled cerium-144 by lung lavage in beagle dogs.

This study was performed to evaluate bronchopulmonary lavage and chelation therapy as a treatment method to prevent the development of radiation pneumonitis after inhalation of a radioactive aerosol. Twelve beagle dogs were exposed to an aerosol of cerium-144 in fused clay particles resulting in initial lung burdens from 47 to 64 muCi of 144-Ce per kg of body weight. Eight of the dogs were treated with a series of 10 bronchopulmonary lavages and 10 intravenous injections of calcium diethylenetriamine pentaacetate acid during the first 56 days after exposure to remove the deposited 144-Ce; the remaing 4 exposed dogs receiged no treatment. An additional 4 dogs were exposed to stable cerium and were given the course of treatment as an additional control group. Three of the 4 untreated dogs and 2 of the 8 treated dogs died 171 to 246 days after exposure with radiation pneumonitis or pulmonary fibrosis, or both. All but one of the remaining dogs were alive and apparently in good clincial health 550 dyas after exposure; the one dog had radiographic indications of pulmonary fibrosis by 365 days after exposure. The relative distribution of 144-Ce in the lungs and other major organs was similar in the treated and untreated dogs that died.

Aerosols↗
PubMed1975

Accumulation and retention of 137Cs-labelled fused aluminosilicate particles by beagle dogs after repeated inhalation exposures.

A group of 12 beagle dogs was given weekly, individual, 10-min inhalation exposures to aerosols of 137Cs-labelled, fused aluminosilicate particles (AMAD approximately equal to 1.8 micron, sigmag approximately equal to 1.6). Whole-body counting was used to assess the pulmonary deposition associated with each exposure and the long-term retention after exposures. Groups of four dogs were removed from further exposures at the end of 10, 20 and 40 exposures, respectively. Two dogs in each group were sacrificed and the other two maintained for long-term retention measurements. The inhaled material was relatively insoluble in body fluids. In each of the sacrificed dogs, approximately equal to 96% of the body burden was in the lung and approximately equal to 1% in the tracheobronchial lymph nodes. The average pulmonary deposition was approximately equal to 20% of the inhaled aerosol for 10, 20 or 30 exposures, a value which was in agreement with previously reported single exposure data. Lower values observed for exposures 31 to 40 were apparently related to differences in respiratory patterns. The long-term, whole-body retentions appear to have effective half-lives ranging from 1200-1800 days in contrast to approximately equal to 400 days seen in singly exposed dogs. Possible reasons are discussed.

Aerosols↗
PubMed1975

Comparative pulmonary carcinogenicity of inhaled beta-emitting radionuclides in beagle dogs.

Beta-emitting radionuclides are important constituents of isotope inventories in light water reactors and may pose an inhalation hazard to industrial workers or the general population if they are released. To study the biological effects of such potential exposures, a series of life span studies was initiated in which beagle dogs were exposed to aerosols of relatively insoluble fused clay particles containing 90Y, 91Y, 144Ce or 90Sr. Groups of dogs exposed to each radionuclide received graded initial lung burdens of radioactivity. When combined with the varied physical half-lives of the four radionuclides, this resulted in a wide variety of radiation doses and dose patterns to the lung. Deaths (greater than 640 days after exposure) were generally associated with pulmonary neoplasia in dogs that inhaled 91Y, 144Ce or 90Sr. These dogs had cumulative lung doses to death greater than 20 000 rads. Exposure to 144Ce or 90Sr with dose rates that decreased slowly induced pulmonary haemangiosarcomas. Pulmonary irradiation from 91Y, with a rapidly decreasing dose rate, resulted in pulmonary epithelial tumours. No malignant lung tumours have been seen within 1540 days after exposure to 90Y. The animals in the main studies have been observed for 1342 to 2756 days after exposure.

Adenocarcinoma, Bronchiolo-Alveolar↗