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G R Hesseltine

Publications and source records attributed to G R Hesseltine.

4 recordsLinked to original sources
PubMed1986

Deposition of ultrafine aggregate particles in exercising rats.

The effect of exercise on particle deposition in rats was investigated. Twenty male rats were trained to run on a treadmill and were exposed to gallium-67 oxide (67Ga2O3) particles (0.1 micron activity median diffusion diameter) for 30 min while running at 30 m min-1. Twenty resting controls were exposed in the same system while confined in wire mesh cages. Ten exercising and 10 resting rats were killed 2 h and 12 days after exposure. Tissue radioactivity levels of 67Ga2O3 were measured and normalized for differences in exposure concentration and body weight. Significantly (P less than 0.05) more 67Ga was deposited in the nasal passages (20 vs 5 nCi) and in the trachea and mainstem bronchi (0.05 vs 0.03 nCi) of exercising rats than in resting rats. There were no significant differences between the exercising and resting rats in amounts of 67Ga in the lung lobes at 2 h after exposure. Using assumed minute volumes, exercising rats had a significantly (P less than 0.05) lower lung deposition efficiency, expressed as percentage of estimated inhaled material, than did resting rats (3 vs 10%). The results suggest that exercising rats inhale more ultrafine particles, but deposit a smaller fraction of them in their lungs. The result is a similar lung burden of 0.1 micron particles in resting and exercising animals.

Aerosols↗
PubMed1985

Comparison of lung burdens of inhaled particles of rats exposed during the day or night.

Inhalation studies frequently involve daytime exposures of nocturnal animals to toxicants. Such exposures may result in different respiratory tract depositions than would be obtained if rodents were exposed at night. Our study assessed the effect of night versus day exposures on lung burdens of particles inhaled by Fischer 344 rats. One group of 15 female rats was exposed to 0.3 micron volume median diameter particles of gallium oxide (Ga2O3) for 11.2 h during the day and a second group of 15 female rats was exposed to the same aerosol for 11.2 h at night. Gallium in the lungs at the end of exposure was measured by electrothermal atomic absorption spectrometry. Rats exposed during the night had significantly (p less than 0.05) higher lung burdens than day-exposed rats when burdens were expressed as either microgram Ga2O3/lung (mean +/- SD = 896 +/- 175 versus 698 +/- 150) or microgram Ga2O3/g lung (mean +/- SD = 683 +/- 134 versus 465 +/- 103). The greater amount of material in lungs of rats exposed at night probably reflected increased ventilation accompanying nocturnal activity.

Aerosols↗
PubMed1985

Metabolism of benzo[a]pyrene on the nasal mucosa of Syrian hamsters: comparison to metabolism by other extrahepatic tissues and possible role of nasally produced metabolites in carcinogenesis.

The formation of metabolites of nasally instilled benzo[a]pyrene [(BP) CAS: 50-32-8] was determined. The study was prompted by a report that a high incidence of tumors occurred in tissues of the upper respiratory and alimentary tracts of Syrian hamsters exposed to BP aerosols. The esophagi of anesthetized hamsters were surgically catheterized so that radiolabeled material instilled as BP in the nose could be collected and analyzed for metabolites. About 50% of the instilled BP was metabolized in the nose and, potentially, would have been swallowed in an awake animal. In auxiliary experiments, homogenates of respiratory and alimentary tissues were tested for metabolic activity for BP. The nose, trachea, and lungs had about equally high activities on a per organ basis (5-7 nmol/hr), whereas all other tissues had considerably less activity. The results of the study indicate that nasal metabolism may be important in causing tumors in alimentary as well as upper respiratory tissues.

Aerosols↗