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Biomedical subjects

B B Boecker

Publications and source records attributed to B B Boecker.

At least 37 records · Page 2Linked to original sources
PubMed1990

Lung lavage therapy to lessen the biological effects of inhaled 144Ce in dogs.

To evaluate the therapeutic effects of removal of an internally deposited radionuclide on long-term biological effects, lung lavage was used to treat dogs that had inhaled 144Ce in a relatively insoluble form, in fused aluminosilicate particles. Either 10 lung lavages were performed between Days 2 and 56 after exposure or 20 lung lavages were performed between Days 2 and 84 after exposure. Approximately one-half of the 144Ce was removed by the lavages, resulting in a corresponding reduction in the total absorbed beta dose to lung. The mean survival time of the treated dogs was 1270 days compared to 370 days for untreated dogs whose initial pulmonary burdens of 144Ce were similar. Treated dogs died late from cancers of the lung or liver, whereas the untreated dogs died at much earlier times from radiation pneumonitis. Dogs treated with lung lavage but not exposed to 144Ce had a mean survival of 4770 days. We concluded that removal of 144Ce from the lung by lavage resulted in increased survival time and in a change in the biological effects from inhaled 144Ce from early-occurring inflammatory disease to late-occurring effects, principally cancer. In addition, the biological effects occurring in the treated dogs could be better predicted from the total absorbed beta dose in the lung and the dose rate after treatment rather than from the original dose rate to the lung. Therefore, we concluded that prompt treatment to remove radioactive materials could be of significant benefit to persons accidentally exposed to high levels of airborne, relatively insoluble, radioactive particles.

Administration, Inhalation↗
PubMed1988

Future development of biological understanding of radiation protection: implications of nonstochastic effects.

Radiation-protection standards are based on minimizing or preventing biological effects in exposed populations. Radiation-induced biological effects can be classified as stochastic--malignant and hereditary diseases for which the probability of an effect occurring is a function of dose without threshold--and nonstochastic--inflammatory and degenerative diseases for which the severity and frequency of the effect varies with the dose and for which a threshold is present. The current International Commission on Radiation Protection (ICRP) approach for setting limits for intakes of radionuclides by workers, which accounts for doses to significantly exposed organs of the body, is based on limitation of stochastic effects in most situations. When setting exposure limits, nonstochastic effects are generally considered to be unlikely at the limits for stochastic effects. In some situations, limits based on prevention of nonstochastic effects are lower than for stochastic effects. This review considers the threshold radiation doses for thyroid, bone, liver and lung and their relationship to the limits recommended by the ICRP and the cancer risks at the limits. This review indicates that the threshold dose for nonstochastic effects in thyroid and lung is much above the dose limit as advocated by ICRP. The threshold dose for nonstochastic effects in bone and liver is much closer to the dose limit, but protection from nonstochastic effects should still be afforded by the dose limits.

Animals↗
PubMed1988

Primary liver tumors in beagle dogs exposed by inhalation to aerosols of plutonium-238 dioxide.

Primary liver tumors developed in Beagle dogs exposed by inhalation to aerosols of 238PuO2. Initial deposition of 238PuO2 in the respiratory tract was followed by translocation of a portion of the 238Pu to the liver and skeleton, which resulted in a large dose commitment and tumor risk to all three tissues. In a population of 144 dogs exposed to 238PuO2, 112 dogs died or were killed 4000 days after 238Pu exposure, 100 dogs had osteosarcoma, and 28 dogs had lung cancers. At increasing times after exposure, however, liver lesions have become more pronounced. Ten primary liver tumors in nine animals were diagnosed in the dogs dying before 4000 days after exposure. An additional five primary liver tumors in three dogs occurred in 9 animals killed after 4000 days after exposure. The majority of these tumors have been fibrosarcomas. The liver tumors were usually not the cause of death, and rarely metastasized. The occurrence of liver tumors in this study indicates that 238Pu is an effective hepatic carcinogen. Liver carcinogenesis is assuming an increasing importance in this study at late times after inhalation exposure. These results suggest that the liver may be an important organ at risk for the development of neoplasia in humans at time periods long after inhalation of 238Pu.

Administration, Inhalation↗
PubMed1987

Single inhalation exposure to 90SrCl2 in the beagle dog: late biological effects.

Late-occurring biologic effects were studied in beagle dogs that were given graded levels of 90SrCl2 via single brief inhalation exposures and were subsequently observed for their life-span. Due to the soluble chemical form of the aerosol, 90Sr was rapidly translocated from lung and deposited in bone where it was subsequently retained for a long period of time. Radiation-induced lesions were confined to the bone, bone marrow, and adjacent soft tissue. Forty-five primary bone tumors occurred in 31 of 66 exposed dogs. Metastasis occurred from 21 tumors, with the lung being the most frequent site of metastasis (76%). Twenty-seven tumors were classified as different subtypes of osteosarcoma, 14 as hemangiosarcomas, 3 as fibrosarcomas, and 1 as a myxosarcoma. Four carcinomas arising from soft tissues adjacent to bone were also considered to be 90Sr induced. In contrast to bone tumors arising in beagles chronically exposed to 90Sr through ingestion, histologic lesions of radiation osteodystrophy were minimal in this study, indicating that these lesions are not a necessary precursor of osteosarcoma development. The incidences of hemangiosarcomas (31%) and telangiectatic osteosarcomas (11%) in addition to osteosarcomas suggest that the cell of origin for all of these neoplasms is a multipotent mesenchymal cell with the potential for various morphologic expressions dependent on local environmental factors.

Aerosols↗
PubMed1987

Dosimetry of 239Pu in dogs that inhaled monodisperse aerosols of 239PuO2.

Existing data from human exposure cases and experimental animal studies on the fate and dosimetry of inhaled insoluble Pu particles are inadequate to provide a comprehensive description and evaluation of the tissues at risk from the alpha radiations of Pu. To improve our knowledge of the dosimetry of inhaled insoluble 239PuO2, this paper describes the uptake and retention of 239Pu in the tissues of dogs that received single inhalation exposures to monodisperse aerosols of 239PuO2. These data include times through 3 years after exposure. Using analytical functions fitted to each tissue data set, 1100-day radiation doses were calculated for lung, liver, skeleton, kidney, spleen, and tracheobronchial, mediastinal, sternal, hepatic, mandibular, and retropharyngeal lymph nodes. The dosimetry results suggest that the lung and lymph nodes associated with lymphatic drainage of the respiratory tract are the principal sites of alpha irradiation. However, the doses for the different respiratory tract lymph nodes vary by a factor of 2000, suggesting that assuming equivalent doses to respiratory tract lymph nodes is not appropriate. Other tissues receive radiation doses also but at levels one to three orders of magnitude less than the lung. Particle size dependence on uptake and retention was noted for the skeleton, mediastinal lymph nodes, hepatic lymph nodes, retropharyngeal lymph nodes, and mandibular lymph nodes.

Administration, Inhalation↗
PubMed1987

Single inhalation exposure to 90SrCl2 in the beagle dog: hematological effects.

The toxicity of 90Sr administered by the inhalation route was studied in young adult Beagle dogs exposed once to aerosols containing 90SrCl2. Due to its relatively soluble chemical form, 90Sr was rapidly translocated from lung to bone where a substantial portion was retained for a long period of time. This resulted in only a brief radiation exposure of the respiratory tract and a protracted exposure of the skeleton. The long-term retained burdens ranged from 0.037 to 4.4 MBq 90Sr/kg body wt. Dogs were subsequently observed throughout their life span. Six dogs with long-term retained burdens of 1.7 to 4.1 MBq 90Sr/kg died at less than 32 days after exposure from radiation-induced bone marrow hypoplasia. Review of hematological parameters of all dogs showed a similar, consistent, and dose-related pancytopenia in those animals having a long-term retained burden of greater than 0.37 MBq 90Sr/kg. Thrombocytopenia and neutropenia persisted in all exposed dogs through 1000 days after exposure. For reference purposes, a burden of 0.37 MBq 90Sr/kg is calculated to deliver an average radiation dose to the skeleton over 30, 100, and 1000 days after intake of 1.0, 2.8, and 17 Gy, respectively. The hematologic changes were similar to those seen in people exposed to high doses of whole-body external radiation.

Administration, Inhalation↗
PubMed1984

Biokinetics of inhaled 239PuO2 in the beagle dog: effect of aerosol particle size.

This study was designed to measure the effect of aerosol particle size on the deposition, retention, excretion and translocation of 239Pu inhaled as the dioxide by Beagle dogs. To address these questions, young adult male and female Beagle dogs received single brief inhalation exposures to one of three monodisperse aerosols of 239PuO2 having sizes of 0.72, 1.4 or 2.8 microns activity median aerodynamic diameter (AMAD). Periodic collections of urine and faeces were made for each dog until sacrifice at times ranging from 4 hours to 2 years after exposure. The results indicate long term retention of a substantial percentage of the initial pulmonary burden (IPB), and that the retention was affected by particle size. The percentage of the initial pulmonary lung burden retained in the long term component and its effective half time (TE) were 90 per cent with TE = 680 days for the 0.72 micron AMAD aerosol, 68 per cent with TE = 1400 days for the 1.4 microns AMAD aerosol and 82 per cent with TE = 1800 days for the 2.8 microns AMAD aerosol. The major route of elimination of 239Pu from lung was via the faeces, but significant amounts were also translocated to thoracic lymph nodes (approximately 15 per cent IPB by 2 years). Small amounts were translocated to liver (0.2 per cent IPB) and skeleton (0.1 per cent IPB) by 2 years after exposure. The average alpha-radiation dose to the lung was projected to be twice as large for the 2.8 microns AMAD group as for the 0.72 micron AMAD group at 10 years after exposure.

Aerosols↗
PubMed1983

Retention of monodisperse or polydisperse aluminosilicate particles inhaled by dogs, rats, and mice.

This study compared long-term retention of 134Cs-labeled fused aluminosilicate particles inhaled by three animal species. Dogs, rats, and mice were briefly exposed to 0.7-, 1.5-, or 2.8-micron activity median aerodynamic diameter (AMAD) monodisperse particles or a polydisperse aerosol with 1.5 to 2.0 micron AMAD and geometric standard deviation of 1.5 to 2.0. Tissues and excreta were collected for up to 850 days after exposure to determine retention and clearance patterns of the inhaled particles. Simulation models were developed for each animal species and aerosol. Solubilization was the dominant factor in long-term lung clearance for most of the particles inhaled by dogs; mechanical clearance was dominant in rats and mice. After accounting for solubility, physical clearance from the lung to the gastrointestinal tract and to lung-associated lymph nodes (LALNs) was independent of particle size within the size range investigated. Rats and mice demonstrated a rapid clearance from the pulmonary region, with most of the mechanically cleared particles going to the gastrointestinal tract; significant translocation to the LALNs occurred for only a few days. The dogs cleared deposited particles at a slower rate, with most of the long-term clearance going to LALNs. A small portion of the initial deposit was retained in the upper respiratory tract of all three species. Results from the data for dogs were used to make long-term predictions for chronic inhalation of particles by humans.

Air Pollutants↗
PubMed1983

Dose-response relationships for bone cancers from plutonium in dogs and people.

The risk of bone cancers developing from internally deposited plutonium must be estimated from studies in laboratory animals because no plutonium-induced cancers have been observed in people. Studies of the effects of 226Ra and 239Pu injected into beagle dogs at the University of Utah and 238PuO2 inhaled by beagle dogs at the Inhalation Toxicology Research Institute provide a key link to understanding the longterm effects of inhaled alpha-emitting radionuclides in people. Injected radium and plutonium are rapidly deposited in bone whereas plutonium deposited in lung by inhalation is translocated to bone more slowly, depending on its chemical form. The development of bone cancers is a late occurring effect seen after either injection of plutonium or radium or inhalation of plutonium. The incidence of bone cancers from alpha radiation to the skeletons of dogs was compared to bone cancer incidences in radium dial painters to estimate bone cancer risk from inhaled plutonium in people. A risk factor of 1200 bone cancers/10(6) rad to skeleton (average dose) was estimated.

Age Factors↗
PubMed1983

Bioassay model for estimating body burdens of 241Am from excretion analyses.

A simple bioassay model for predicting the organ burdens of 241Am from excretion rates is presented for inhalation exposures. The model uses three compartments representing lung, liver and skeleton. The model was developed using data from studies in laboratory animals of inhaled or injected 241Am and was validated for people by comparison to cases of accidental inhalation exposures to 241Am. The data for people have a large amount of variability but indicate that the retention half-time of 241Am in liver is approximately 2 yr and in skeleton is approximately 30 yr. These parameters can be used in the model to estimate body and organ burdens from excretion rates after inhalation of 241Am or the model can be fitted to an individual's measured excretion rates.

Americium↗
PubMed1983

Influence of radiation dose patterns on lung tumor incidence in dogs that inhaled beta emitters: a preliminary report.

Different radiation dose patterns to the lung from inhaled beta-emitting radionuclides may influence the frequency and kind of biological effects. To determine the magnitude of this influence, groups of Beagle dogs were exposed to aerosols of 90Y, 91Y, 144Ce, or 90Sr in relatively insoluble particles and observed for their life spans. Different dose patterns were achieved by using these radionuclides having similar beta emissions and chemical form but having physical half-lives ranging from 2.6 days to 28 years. The range of initial lung burdens of radionuclides studied resulted in a range of biological effects from early deaths at the highest radiation doses to no discernible effects at the lowest doses. The effective half-lives of the four radionuclides in the lung ranged from 2.5 to 600 days. Within 1.5 years after exposure, some dogs died with radiation pneumonitis and pulmonary fibrosis. Between 1.5 and 10 years after exposure, 42 pulmonary carcinomas and 28 pulmonary sarcomas were observed in 163 dogs that died. Protracted irradiation of the lung from 90Sr or 144Ce resulted in a relatively high radiation dose and produced more total lung tumors but fewer lung tumors per rad than less protracted irradiation from 90Y or 91Y. At 10 years after inhalation exposure, the difference in risk per rad among the different dose patterns was a factor of 4 to 8, indicating that the different radiation dose patterns from inhaled beta emitters do influence lung tumor risk factors, at least at high (greater than 20,000 rad) doses to lung.

Aerosols↗
PubMed1981

Primary bone neoplasms in beagle dogs exposed by inhalation to aerosols of plutonium-238 dioxide.

Primary bone neoplasms developed in beagle dogs briefly exposed by inhalation to aerosols of 238PuO2. 238PuO2 was initially deposited in the respiratory tract where it was retained with a half time greater than 100 days. A portion of the 238Pu was solubilized and translocated to the liver and skeleton. Five years after exposure, 46 osteosarcomas developed in 35 of 144 exposed dogs. The cumulative absorbed radiation doses to skeleton for these dogs ranged from 210 to 830 rad. Of the 46 bone tumors, 22 originated in the vertebrae, 12 in the humeri, 6 in the pelves, and 6 in miscellaneous long and flat bones. Most of the tumors were well-differentiated sarcomas. Only 10 of the tumors metastasized; the lung was the organ most often invaded. Bone tumors were associated with lesions of radiation osteodysplasia. The number of bone tumors found in this study indicated that inhaled 238PuO2 was an effective skeletal carcinogen. The rate of solubilization in the lung and translocation to bone may be a factor in the radiation dose pattern and type and location of bone tumors that developed after inhalation of 238PuO2.

Aerosols↗
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↗