Liquid scintillation based quantitative measurement of dual radioisotopes (3H and 45Ca) in biological samples for bone remodeling studies.

Acute and prolonged bone complications associated with radiation and chemotherapy in cancer survivors underscore the importance of establishing a laboratory-based complementary dual-isotope tool to evaluate short- as well as long-term bone remodeling in an in vivo model. To address this need, a liquid scintillation dual-label method was investigated using different scintillation cocktails for quantitative measurement of (3)H-tetracycline ((3)H-TC) and (45)Ca as markers of bone turnover in mice. Individual samples were prepared over a wide range of known (45)Ca/(3)H activity ratios. Results showed that (45)Ca/(3)H activity ratios determined experimentally by the dual-label method were comparable to the known activity ratios (percentage difference ∼2%), but large variations were found in samples with (45)Ca/(3)H activity ratios in range of 2-10 (percentage difference ∼20-30%). Urine and fecal samples from mice administered with both (3)H-TC and (45)Ca were analyzed with the dual-label method. Positive correlations between (3)H and (45)Ca in urine (R=0.93) and feces (R=0.83) indicate that (3)H-TC and (45)Ca can be interchangeably used to monitor longitudinal in vivo skeletal remodeling.

The effect of a simultaneous dietary administration of xylitol and ethanol on bone resorption.

Our previous studies have shown that dietary xylitol supplementation diminishes bone resorption in rats, as well as protects against ovariectomy-induced increase of bone resorption during experimental osteoporosis. Interestingly, ethanol, when given simultaneously with xylitol, is known to increase blood concentration of xylitol. On the other hand, ethanol, when given alone, has been shown to increase bone resorption. The aim of the present study was to evaluate the effects of a simultaneous dietary administration of 10% xylitol and 10% ethanol on bone resorption. Bone resorption was determined using measurement of urinary excretion of hydrogen 3 (3H) radioactivity in 3H-tetracycline prelabeled rats. Already 4 days after the beginning of dietary supplementations, excretion of 3H was about 15% lower in the xylitol group (diet supplemented with 10% xylitol) and about 25% lower in the xylitol-ethanol group (diet supplemented with 10% xylitol and 10% ethanol) as compared to the controls. The excretion of 3H in these groups remained smaller than that of the controls throughout the entire study period of 40 days. The excretion of 3 H in the xylitol-ethanol group remained also smaller than that of the xylitol group. Bone mineral density and bone mineral content were determined with a peripheral quantitative computed tomography (pQCT) system from the rat tibiae at the end of the experiment. Trabecular bone mineral density and trabecular bone mineral content were significantly greater in the xylitol group and in the xylitol-ethanol group compared to the controls. They were also greater in the xylitol-ethanol group as compared to the xylitol group. Cortical bone mineral density and cortical bone mineral content did not differ significantly between the groups. In conclusion, a simultaneous dietary supplementation with 10% xylitol and 10% ethanol seems to diminish bone resorption and to increase trabecular bone mineral density and trabecular bone mineral content in rats. These effects seem to be stronger than the effects induced by 10% xylitol supplementation alone.

The Canadian National Calibration Reference Center for Bioassay and in-vivo Monitoring: a program summary.

The Canadian National Calibration Reference Center for Bioassay and in-vivo Monitoring is part of the Radiation Protection Bureau, Department of Health. The Reference Center operates a variety of different intercomparison programs that are designed to confirm that workplace monitoring results are accurate and provide the necessary external verification required by the Canadian regulators. The programs administered by the Reference Center currently include urinalysis intercomparisons for tritium, natural uranium, and 14C, and in-vivo programs for whole-body, thorax, and thyroid monitoring. The benefits of the intercomparison programs to the participants are discussed by example. Future programs that are planned include dual spiked urine sample which contain both tritium and 14C and the in-vivo measurement of 99mTc.

Radiotoxicological intercomparisons organised by the Commissariat à l'Energie Atomique group in France.

People working in French nuclear plants are monitored either by whole body counting or by the measurement of biological samples. The radiochemical and radiometric procedures used have to be periodically reviewed. A working group, including practising biologists from CEA, EDF and the Armed Forces Health Service, instituted comparisons of radiotoxicological test assessments. Since 1978, about 60 intercomparisons have been made. Currently 30 European laboratories are involved in these intercomparisons. This paper provides a brief history of the intercomparison exercises, describes the logistics of sample collection and preparation, and presents the results, showing the position of each laboratory in relation to the reference and median values. Diagrams produced by radiochemical analysis, relating to plutonium in urine and in faecal samples, and to tritium, strontium and enriched uranium in urine, are analysed.