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Biomedical subjects

P E Hamrick

Publications and source records attributed to P E Hamrick.

At least 19 recordsLinked to original sources

A computerized radioactive material inventory system using a commercially available database program.

An accurate and current radioactive materials inventory is essential for efficient control and use of radioactive material. In order to facilitate data entry, a computerized radioactive material inventory procedure has been developed using a commercially available database program. This system allows inventory records to be entered and updated quickly and efficiently with desired reports generated, without needing extensive computer training or programming skills.

Documentation

Monitoring of 35S in ash of incinerated waste.

The National Institute of Environmental Health Sciences incinerates low-level radioactive waste containing 3H, 14C, and 35S as a means of volume reduction. The primary isotope remaining in the ash is 35S. Some effects of the chemical and physical form of the waste on sulfur retention in ash and several methods for determining the activity remaining in the ash have been explored. It was found that the sulfur in sodium sulfate has a higher retention in ash than the sulfur in methionine and that the presence of glass appears to enhance the retention. Liquid scintillation and proportional counting methods were compared. A sulfur extraction procedure using liquid scintillation counting was found to give the lowest minimum detectable activity. However, it was determined that a more practical method for routine monitoring is to suspend a small quantity of ash in a liquid scintillation gel.

Environmental Monitoring

A small, multi-element fingertip dosimeter for beta radiation.

Many occupations involve potential exposures, directly or indirectly, to sources of beta radiation. The region of highest exposure, in many cases, will be the extremities and in particular the fingertips of people handling beta sources. Because current extremity dosimeters can significantly underestimate beta doses to the fingertips, an improved fingertip beta dosimeter was developed. The dosimeter employs a multi-element, multi-filter concept by stacking four or five thin (0.13 mm) LiF-Teflon TLDs to form the beta detector element. The entire dosimeter is approximately 1 mm thick, flexible and rugged enough for field use without interference of the user's manual dexterity. The fingertip dosimeter provides data for determining the beta energy of each exposure. The beta energy can be used to determine the TLD correction factor for converting the TLD output to beta dose. The data can be used to reconstruct the beta depth dose curve and the depth dose curve can be used to calculate the beta dose in tissue at 7 mg cm-2, for legal reporting purposes, or at any other desired depth within the range of the beta radiation. Relationships between the effective mass absorption coefficient and beta energy and between the beta correction factor and beta energy were determined for use in this study. Beta sources were fabricated for these studies, and an extrapolation chamber was used to determine reference beta doses. Tests of the fingertip dosimeter were performed by exposing it to single beta sources and to multiple beta sources. The dosimeter should be useful for monitoring exposures to beta energies ranging from 0.29-2.5 MeV.

Beta Particles

Incineration and monitoring of low-level 3H and 14C wastes at a biological research institution.

Low-level radioactive waste containing liquid scintillation fluid and known amounts of 14C and 3H has been incinerated in a modified pathological incinerator with the incinerator effluent, refractory surface and ash being monitored. The study relates the activity monitored to that incinerated and discusses how this relation was affected by a modification of the incinerator and monitoring conditions. No significant activity was found to be associated with the ash, particulates or the refractory surface. These data suggest that most of the activity is released as tritiated water vapor and 14C-labeled carbon dioxide. However, incomplete oxidation may occur for short periods of time depending on the amount of liquid scintillation fluid incinerated, with the possible release of 14C-labeled carbon monoxide.

Carbon Radioisotopes

Water permeability of the endolymph-perilymph barrier in the guinea pig cochlea.

The diffusional water permeability of the endolymph-perilymph barrier was determined in guinea pigs by perfusing the perilymphatic space with tritiated water and measuring the uptake of tritiated water into the endolymph. Assuming that the volume flow across the endolymph-perilymph barrier is negligible for short periods of perfusion, the water permeability of the barrier is approximately 130 times greater than its permeability to K+ in normal guinea pigs.

Animals

Effects of hypothermia on ionic movement in the guinea pig cochlea.

Anesthetized and immobilized guinea pigs were subjected to hypothermia. During cooling, the cochlear microphonics and endocochlear potential decreased and K+ concentrations in both endolymph and perilymph were not significantly affected. The rate constant for K+ turnover to endolymph was determined by uptake of 43K into the endolymph when the perilymphatic space was perfused with artificial perilymph containing 43K. The rate constant for K+ decreased significantly in hypothermic guinea pigs when compared with that in normal guinea pigs. The K+ conductance of the endolymph-perilymph barrier, estimated from the rate constant, showed a marked decrease in hypothermic guinea pigs and was comparable with the K+ conductance, calculated from the rate of change of the endolymph K+ concentrations relative to the K+ electrochemical potential difference, recorded during permanent anoxia. These results suggest that hypothermia not only suppresses the active K+ transport system but also decreases the K+ permeability of the endolymph-perilymph barrier.

Animals

Effects of exposure to noise on ion movement in guinea pig cochlea.

Healthy guinea pigs were exposed to broad band noise at levels between 95 and 115 dBA for 7 days. A significant decrease of the sound-induced cochlear responses, together with a substantial increase of the endocochlear potential, was observed in guinea pigs exposed to noise at 105 or 115 dBA. Microsamples of the endolymph obtained from these guinea pigs showed a significant increase of K+ and Cl- concentrations and a decrease of Na+ concentration, when compared with those from control animals. The K+, Na+ and Cl- concentrations in the perilymph were not markedly affected by noise exposure. When the perilymphatic space was perfused with artificial perilymph containing 43K, 22Na or 36 Cl, the uptake of radiotracers into the endolymph showed a single exponential function of the perfusion time. When compared with rate constants in normal animals, the value of rate constant for K+ was significantly decreased in animals exposed to noise. These results indicate that ionic permeability changes of the endolymph-perilymph barrier are a significant factor in the physiological mechanisms underlying noise-induced hearing loss.

Animals

The uptake of methyl mercury in guinea pig cochlea in relation to its ototoxic effect.

Guinea pigs were treated for 7 days by daily subcutaneous injection of methyl mercury chloride labeled with 14C, the total dose of which was 17 mg Hg/kg. In these animals the cochlear microphonics and whole-nerve action potentials were suppressed in the basal turn but there was no marked losses in the third turn of the cochlea. The endocochlear potential was not decreased in magnitude. At the end of the treatment there was no accumulation of mercury in the perilymph, endolymph and cerebrospinal fluid. Uptake and elimination of mercury in the cochlear fluids were studied in guinea pigs which were treated by a single intravenous injection of 203Hg-labeled methyl mercury, the dose of which ranged from 0.2 to 17 mg Hg/kg. The results indicated that mercury concentration ratio of the blood relative to cochlear fluids was comparable with the blood to plasma ratio reported previously. In contrast to lack of accumulation in the extra cellular environment, it is likely that tissues of the sensory end organs in the cochlea accumulated methyl mercury.

Action Potentials

Rat lymphocytes in cell culture exposed to 2450 MHz (CW) microwave radiation.

Rat lymphocytes were exposed to continuous wave microwave radiation at a frequency of 2450 MHz at intensities of 5, 10 and 20 mW/cm2. The corresponding rates of absorption of energy were determined to be 0.7, 1.4 and 2.8 mW/g. The lymphocytes were exposed for 4, 24 or 44 h either with or without the addition of a mitogen (phytohemagglutinin). The transformation of lymphocytes into lyphoblasts was monitored by the addition of tritiated thymidine. No significant differences (P less than .05) were found in the uptake of tritiated thymidine between exposed and control cultures.

Animals

Some effects of exposure of the Japanese quail embryo to 2.45-GHz microwave radiation.

Exposure of quail eggs 4 hr per day during the first 5 incubation days at 2450 MHz and in an exposure field of 30 mW/cm-2 and at an absorbed power of 14 mW/g does not cause any great change in body weight, observed gross malformations, rbc, wbc, hematocrit, hemoglobin, or differential wbc percentages. If small differences exist in these parameters due to microwave exposure, they are obscured by the large variability between individual quail. This variability is believed to partially result from changing blood values in the developing young quail, and the 2-day spread in ages at the time of sacrifice could account for some of the variability. The overall hatch percentages for the exposed and control eggs were approximately equal. A slight significant decrease (11%) in hemoglobin was noted in the birds irradiated on Day 2. Additional verification, however, is needed, because the observed change is less than the normal range of values observed in young quail. These data do suggest, however, that exposure of developing Japanese quail embryo to microwave radiation of the frequency and power density level used in this study does not preclude normal systemic development, hematologic differentiation, or the general hardiness of the hatched quail.

Animals

Leukopenia in neonatal Japanese quail.

Japanese quail were sacrificed at one or two days after hatching. several hematological parameters were measured. A leukopenia occurred in the two-day-old quail. Concomitantly the circulating numbers of lymphocytes were reduced in the older quail. It appears that this functional leukopenia is attributable to reduced numbers of lymphocytes and may represent an heretofore undefined physiological adaptive mechanism which occurs during the early neonatal period.

Animals

Hematology of neonatal Japanese quail.

The hematologic development of Japanese quail was studied as a function of time through the first 49 hr post-hatching. Packed cell volumes, hemoglobin levels, erythrocyte and leukocyte numbers, as well as differential percentages of lymphocytes, heterophils, basophils, eosinophils, and monocytes were determined. Additionally, the mean corpuscular volumes, mean corpuscular hemoglobins, and mean corpuscular hemoglobin concentrations were calculated. Of particular interest are the increasing mean corpuscular volume and the increasing number of erythrocytes which were observed as the birds aged. Between the 13th and 19th hr after hatching, an almost 2-fold increase in the erythrocyte number was detected with a concomitant decrease in the mean corpuscular volume. These findings indicate that the state of the hematologic system in quail is highly dependent on the stage of post-embryonic maturation.

Animals

Environmental radiation and the lung.

Environmental sources of radioactive materials and their relation to lung doses and lung burdens are described. The approaches used and the problems encountered in estimating lung doses are illustrated. Exposure to radon daughter products is contrasted to exposure to plutonium as particular examples of the hazards associated with radioactive materials of different chemical and physical characteristics.

Air Pollution, Radioactive