微波氚标记法与化合物结构的关系

本文报道了应用微波氚标记了许多不同类型的化合物,这些化合物的放射比度与结构紧密相关,对于在相同条件下研究不同化合物的标记比度提供了一些参考数据。     

No disturbance of myelination in the central nervous system by selective3Hβ-irradiation

Summary The effect of a selective irradiation of myelin by³H -particles was studied by light and electron microscopic methods in guinea pig spinal cord. The animals were injected with [³H]leucine shortly after birth when the rate of myelin biosynthesis is high and sacrificed 130 days later. In spinal cord the radioactivity was mainly preserved in myelin because the half life of myelin proteins is much higher than that of most other CNS protein. As a consequence the irradiation dose in the white matter was much higher than in the gray matter. In myelin internally irradiated by³H -particles within 130 days at a dose of 10 Gy no alterations could be detected either by morphological or by morphometric methods.Supported by the Deutsche Forschungsgemeinschaft     

气动磁镜氘氚聚变体中子源的辐射安全管理初探

随着聚变能研究进入工程化阶段,迫切需要高通量聚变体中子源开展材料和部件的辐照测试。基于气动磁镜（Gas Dynamic Trap,GDT）装置的聚变中子源具有中子通量高、测试空间大、建造成本低等优点,是高通量聚变体中子源的理想方案。作为一种新型的放射性装置,在我国现行核安全监管法律法规体系下,如何对其开展辐射安全管理是在该装置建造之前必须要理清的问题。本文分析了GDT聚变体中子源的辐射安全特性,阐明了GDT聚变体中子源的主要辐射源项,并结合我国现有核安全监管法律法规要求,提出GDT聚变体中子源在建造及应用过程中的辐射防护与安全管理要点,建议GDT中子源作为I类射线装置管理,运行之前应取得辐射安全许可证和核材料许可证,特别需要注意对放射性氚的安全防护。本文为国际高通量聚变体中子源ALIANCE的辐射安全管理工作提供指导,同时可供我国的核与辐射安全管理部门参考。     

Tritiation and characterization of several suicide substrate enzyme inactivators

Methods are presented to tritiate the enzyme inhibitors pargyline and caracemide.     

Cellular- and micro-dosimetry of heterogeneously distributed tritium

Abstract

Purpose: The assessment of radiotoxicity for heterogeneously distributed tritium should be based on the subcellular dose and relative biological effectiveness (RBE) for cell nucleus. In the present work, geometry-dependent absorbed dose and RBE were calculated using Monte Carlo codes for tritium in the cell, cell surface, cytoplasm, or cell nucleus.

Materials and methods: Penelope (PENetration and Energy LOss of Positrins and Electrons) code was used to calculate the geometry-dependent absorbed dose, lineal energy, and electron fluence spectrum. RBE for the intestinal crypt regeneration was calculated using a lineal energy-dependent biological weighting function. RBE for the induction of DNA double strand breaks was estimated using a nucleotide-level map for clustered DNA lesions of the Monte Carlo damage simulation (MCDS) code.

Results: For a typical cell of 10 μm radius and 5 μm nuclear radius, tritium in the cell nucleus resulted in much higher RBE-weighted absorbed dose than tritium distributed uniformly. Conversely, tritium distributed on the cell surface led to trivial RBE-weighted absorbed dose due to irradiation geometry and great attenuation of beta particles in the cytoplasm. For tritium uniformly distributed in the cell, the RBE-weighted absorbed dose was larger compared to tritium uniformly distributed in the tissue.

Conclusions: Cellular- and micro-dosimetry models were developed for the assessment of heterogeneously distributed tritium.     

Hemicholinium-3 binding sites in rat brain: a quantitative autoradiographic study

Quantitative in vitro autoradiography was used to study the distribution of [3H]hemicholinium-3 ([3H]HC-3) binding sites in the rat brain. Regional concentrations of HC-3 binding sites were corrected for regional tissue quenching of tritium in a number of brain structures. Specific binding of 10 nM [3H]HC-3 was highest in the interpeduncular nucleus, followed by the caudate-putamen, olfactory tubercle, amygdala, and the medial and lateral habenulae. There was a high positive correlation between regional HC-3 binding and choline acetyltransferase activity in rat brain; however, a novel pattern of the distribution of cholinergic terminals in the subnuclei of the interpeduncular nucleus was discovered. The apparent Kd in the 1-5 nM range and the pharmacological specificity of the HC-3 binding site agreed with data for choline uptake and for the HC-3 binding site as determined in membrane preparations. HC-3 autoradiography appears to be a useful anatomical marker for cholinergic terminals.     

Regional distribution of high-affinity [H]somatostatin binding sites in the human brain

The distribution of high-affinity binding sites for [³H]somatostatin has been studied in membrane preparations from a number of regions of normal human brain. The highest densities of binding sites (> 48 fmol/mg protein) were found in the cerebral and cerebellar cortices and the hippocampus, with intermediate binding densities (30–46 fmol/mg protein) being present in the basal ganglia, amygdala, septum and claustrum. The lowest densities of binding sites (<14 fmol/mg protein) were observed in the hypothalamus, thalamus and substantia nigra. The binding of [³H]somatostatin in both the frontal cortex and cerebellar cortex demonstrated pharmacological specificity, since somatostatin-28, but not somatostatin-28_1–12 or Des AA^{1,2,4,5,12,13}, -Trp⁸-somatostatin, competed for the binding sites. Scatchard analysis of the binding in both frontal cortex and cerebellar cortex revealed the presence of two classes of high-affinity binding sites.     

Tritium in [O]water containing [F]fluoride for [F]FDG synthesis

The presence of tritium in enriched [¹⁸O]water irradiated with 9.6 MeV protons used to produce [¹⁸F]fluoride by the ¹⁸O(p, n)¹⁸F reaction was inferred from the cross sections and threshold energies of the ¹⁸O(p, t)¹⁶O reaction, and the existence of tritium was confirmed experimentally. Tritium was also detected in both [¹⁸O]water recovered for recycling and waste acetonitrile solutions. The purified [¹⁸F]FDG was not contaminated with ³H. The amount of ³H discharged into the air was far less than the International Basic Safety Standard Level.     

Chromosome analysis of lymphocytes from radiation workers in tritium-applying industry

Objectives : The frequency of chromosomal aberrations (CA) and micronuclei (MN) in peripheral blood lymphocytes was compared in two groups of persons occupationally exposed to tritium either through the use of luminous paints or in the weapons industry, with the aim of finding a correlation between the CA and MN assays, the extent of radiation hazard, and the duration of occupational exposure to chemical forms of tritium and the ability of the latter to induce hazards in human lymphocytes. Methods : CA analysis and the cytochalasin B micronucleus test were performed. Urinary tritium in both groups was measured using a liquid scintillation method. For purposes of comparison, 2 control groups (40 persons) were examined; 24 exposed individuals were matched to their controls according to age, sex, and smoking habits. Results: Values recorded for the frequency of CA in the group of workers handling tritium in luminous dial painting were 0.015 ± 0.014 dicentrics/cell, 0.023 ± 0.017 total unstable CA/cell, and 0.035 ± 0.019 MN/binucleated cell. Urinary levels of tritium in this group of employees ranged from 1.35 to 9.43 MBq/l. As compared with their matched controls, in these workers the differences in the yield of CA as well as in MN were statistically highly significant (P<0.005 and P<0.003, respectively). The same parameters analyzed in workers employed in the armament industry gave values of 0.001 ± 0.003 dicentrics/cell, 0.010 ± 0.008 total unstable CA/cell, and 0.021 ± 0.029 MN/binucleated cell. No detectable concentration of urinary tritium was found. As compared with their matched controls, in these workers the differences were also statistically significant (P<0.027 and P<0.012, respectively). The yield of CA, particularly the yield of dicentrics, was significantly higher (P<0.005) in the group of luminous dial painters as compared with the weapons industry workers. The difference found in the yield of MN between the two groups of workers was also statistically significant (P<0.084). Intercontrol differences in the yields of spontaneous CA as well as in MN were insignificant (P<0.683 and P<0.735, respectively). The results are discussed with respect to individual variations in the response to low doses of ionizing radiation, disorders in the handling of radionuclides, the duration of occupational exposure, and the chemical properties of the radionuclides used. Conclusion : Tritium in the chemical form of luminous paint is a more powerful clastogenic agent than tritium gas. Statistical analysis demonstrated that lymphocyte effects are due to the concentration of tritium in urine rather than to the duration of occupational exposure. Since the radiation hazard measured by the MN assay did not differ from that determined by the CA assay, the MN test can be recommended as a rapid assay for screening purposes in cases of occupational exposure to low radiation doses. Received: 20 November 1996 / Accepted: 1 August 1997     

Whole head sectioning in [H] deoxyglucose mapping of auditory responses in gerbils

Stimulus-specific neuronal responses in the central auditory pathway of Psammomys obesus were studied with deoxyglucose autoradiography. Responses were revealed mainly in the inferior colliculus. With whole head sectioning and subsequent gentle freeze-drying, excellent structural preservation was achieved. With the use of doubletritiated deoxyglucose, Ultrofilm ³H and vacuum-contact exposure, a mean spatial resolution of 43 μm Full Width Half Maximum was achieved.