Various problems have been pointed out in determining counting efficiency of a Gesemiconductor detector for volume samples. To study these problems, the source position dependence of counting efficiency was measured for a point γ-ray source which contains 9 nuclides, changing its position above the detector. A following simple model to reproduce the experimental values was worked out for the efficiency calculation. 1. The detector is replaced by an imaginary “ring”. 2. The “ring” is shielded by the upper part of detector material above the ring. 3. Only γ-rays directly reached the “ring” can be detected. With these assumptions, the source position dependence of counting efficiency becomes ε=∫exp(-μd⋅ld-μs⋅ls)/l2dr dr=diferential “ring”. l=distance between the “ring” and the source. la=γ-ray path length within the sample. ld=γ-ray path length within the detector. μs=linear attenuation coefficient for the sample material. μd=linear attenuation coefficient for the detector material. The efficiency for a volume sample can be calculated by numerical integration of the position dependent efficiency function over the space of the sample volume. The results calculated by this model were in very good agreement with the experimental values of efficiencies obtained for samples with various matrices and thickness.
The isotopic exchange method is studied for the simultaneous determination of radioactive and stable isotopes of cobalt in environmental samples. Radioactive cobalt is isotopically exchanged with Co-CyDTA in HCl solution of the sample. The solvent extraction method is used for the separation of Co2+and Co-CyDTA species from each other. The amounts of radioactive and stable cobalt isotopes are calculated with activities of Co and Co-CyDTA at the exchange equilibrium. The methods for eliminating interfering ions are discussed. The results are in good concordance with those obtained by the conventional analytical methods.
Sub- and super-equivalence method of isotope dilution analysis (SSE-IDA) using enzyme reaction was first applied for the determination of biological substance, DNA. Radioactive DNA (pUC18) to be analysed was prepared by incorporating3H-thymidine in growing E. coli. A part of DNA was cut into the linear form (L-form) DNA under definite conditions using a restriction enzyme HindIII, following the separation of each by gel electrophoresis. Radioactivities of separated L-form DNA of two series were measured. The quantity of DNA was obtained by a graph method of SSE-IDA. As preliminary experiments, it was examined under what conditions the enzyme reaction proceeds as zeroth or first order reaction. We used the enzyme and substrate concentrations near zeroth order, where ordinary subst-IDA seems not to give a satisfactory results. As the results, 0.25μg of DNA was determined the error of about 10%.
In this study, we developed a measuring system for proinsulin in human serum. Insulin-like substances (ILS) were isolated from serum by an affinity chromatography, and Proinsulin in ILS was separated from insulin by high-performance liquid chromatography (HPLC) . For the radioimmunoassay (RIA), porcine Proinsulin was used as the standard and as125I-labelled antigen, and porcine insulin anti-serum was as the antibody. Proinsulin-like immunoreactivity (PLI) can be estimated directly from a standard curve, and the detection limit of PLI is 0.0044 pmol/ml. By this method, the values of PLI and insulin-like immunoreactivity (IRI) in human blood were able to estimate precisely. PLI values in the fasting state and in 30, 60, 90, and 120 min after oral glucose stimulation from nine healthy subjects were 0.011±0.002, 0.045±0.014, 0.078±0.019, 0.064±0.016, and 0.027±0.006pmol/ml, respectively. The increase in PLI response was observed later than that in IRI response. PLI/total IRI ratio in the fasting state and 60 min after oral glucose were 24 and 36% respectively.
As there has been no data available on the variation of RIA through a year, we assessed within kit and component of between assay variation of TSH, LH, FSH, C-peptide and PRL kit through a year (more than 12 sequential assays) . The average of within kit variation was 6.9% (ranged from 4.7 to 9.8%) and that of component of between assay variation was 11.2% (ranged from 8.9 to 14.5%) . These values were almost similar to those obtained for the within kit variation and component of between assay variation employing single lot of kit. These results warrant that quality of kits produced by manufacturers was homogeneous throughout the observation period.
The significance of high renal uptake found in patients with hematological disease who underwent bone marrow scintigraphy with111In-chloride was investigated. In patients with a high renal uptake, the uptake in bone marrow was low, suggesting a reflection of erythropoietic activity. The reversal relationship, however, was not necessarily present. With regard to correlation with iron metabolism, significantly higher uptake of serum Fe and lower UIBC were found among those with high renal uptake, suggesting that the level of free traps ferrin in the serum is largely involved in the high uptake in the kidney.