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Preliminary experiments suggested that total levels of radioactivity disappeared from the blood of male, Fischer rats much more rapidly following intragastric administration of 14C-Δ9-tetrahydrocannabinol (14C-THC) than 3H-THC. Collaborative experiments at the Stanford Research Institute (SRI) and the Research Institute on Alcoholism (RIA) verified and characterized the initial observations. In rats that had food available throughout the experiments, the concentrations of total 3H and 14C in fresh plasma reached a maximum at 2 – 4 hours after treatment with 3H-THC plus 14C-THC. Thereafter, 14C levels fell while 3H levels decreased very slowly or not at all. In fasted rats, peak plasma concentrations of both isotopes were not attained until about 8 hours following drug administration. The concentrations of 14C then decreased more rapidly than 3H. The differences between the plasma disappearance curves for 14C and 3H were not dependent upon the method of blood collection or the techniques of isotope counting. However, when plasma or whole blood samples were dried before radioisotope analysis, the difference between 14C and 3H concentrations was virtually abolished in fed and fasted rats. Experiments suggest that tritiated water, produced during the metabolism of 3H-THC, may be responsible for the prolonged maintenance of high 3H levels in the blood. 相似文献
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本文以河口底栖鱼类,不具鳞片,对环境适应力强的乌塘鳢为材料,研究它们以摄食和渗透两种方式对~(51)Cr,~(60)Co、~(131)I和~(141)Ce的吸收。为了观察在渗透吸收期间个体的差异,测定了单条活鱼的放射性。在实验中采用多核素示踪法并用S-80智能多道分析器和Ge(Li)探头测量放射性。 结果发现,当~(131)I的浓度为3.4×10~(-7)居里/升时,在10小时内所有的乌塘鳢都被杀死,而~(131)I在鱼体各组织器官的积累是明显的。器官积累核素数量的顺序是~(131)I>~(141)Ce>~(51)Cr,在任何组织器官均未检出~(60)Co。 在渗透吸收实验里,对单条活鱼的测量结果表明,核素是能够通过皮肤的渗透积累在鱼体内,并且存在个体差异。同时表明,生命元素的同位素如~(131)I,~(60)Co容易渗透到鱼体内部器官,而非生命元素的同位素例如~(141)Ce、~(51)Cr的渗透是慢的。 ~(51)Cr、~(60)Co、~(131)I、~(141)Ce是沿海核设施常见的放射性废物成分,有的是具有生态学意义的核素(Goldberg,1957),随着沿海核电站的不断兴建,它们在河口港湾存在的机会越来越多。虽然海洋鱼类和淡水鱼类对它们的浓集有过报道(Hiyama et al.,1964),但河口生物,特别是河口的底栖鱼类对它们的吸收和积累,则研究甚少。 乌塘鳢是生活在河口滩涂的底栖鱼类,适应于半咸淡的水质, 相似文献
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通过在野外28.5 hm2的坡耕地上采集土壤样品,定量评价了利用137Cs和210Pbex研究土壤有机碳(SOC)动态的潜力,以探讨东北黑土区土壤侵蚀对土壤有机碳的影响.结果表明:农耕地土壤137Cs、210Pbex和SOC在平面和垂直深度上均具有相似的分布特征.在平面上,尽管受土壤侵蚀沉积的影响,137Cs、210Pbex面积活度及SOC储量变异很大,但它们具有相同的变化趋势.在垂直断面上,侵蚀区137Cs、210Pbex和SOC在0~25 cm耕层内分布均匀,25 cm以下放射性活度减小,SOC含量也相应下降;沉积区0~100 cm深度上137Cs和210Pbex呈现先增加后减小的分布规律,SOC也具有类似的变化特征.农耕地SOC与137Cs、210Pbex呈显著线性相关,表明它们在黑土区农耕地上具有相似的物理运移特征,137Cs和210Pbex可直接用来定量评价黑土侵蚀下SOC的时空分布特点. 相似文献
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Since cannabinoids lead to dose-related tachycardia in man but dose dependent bradycardia has been reported thus far in laboratory animals, there would seem to be a need for an experimental model in which the effect seen in man (tachycardia) could be reproduced and explored. In the conscious rat, the compounds Δ9-tetrahydrocannabinol (Δ9-THC) and dimethylheptylpyran (DMHP) injected i.p. led to dose-related increases in heart rate at 10–20 minutes after administration. In vehicle (ethanol) control rats there were small increases in heart rate. Propranolol given before Δ9-THC resulted in a parallel shift to the right of the dose-effect curve. Adrenalectomy led to a significant (p<0.01) decrease in tachycardia following Δ9-THC and DMHP while ganglionic block markedly decreased the heart rate increases after Δ9-THC (p<0.001). Systolic blood pressure at nearly all doses of Δ9-THC was minimally affected, although it tended to decrease with increasing dose. Tachycardia in the rat may be the result of a centrally mediated release of epinephrine from the adrenal gland. 相似文献
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The 13C/12Cratio, photosynthetic rate and stomatie conductivity of leaves of Pinus massoniana, Schima superba,Psychotria rubra, Evodia lepta and Rhodomyrtus tomentasa are measured. No significant deviation (at 5% level) is observed between water use efficiencies calculated by these items. The13C/12Cis 25.41±0.61‰. In average for treerings of Pinus massoniana from 1971 to 1983(n=6), with the maximum in1977 when the lowest precipitation was recorded. The average water use efficiency of Pinus massoniana is 8.28±0.38 in1977—1983, which is higher than that of trees in natural site and might be caused by the changes of solar radiation and water condition. 13C/12Cratio ana lysis could provide usefull informations for studying water use efficiency of artificial forest. 相似文献
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M. Ferrez M. Renoir A. Alfsen E.E. Baulieu H. Weintraub 《Biochemical and biophysical research communications》1980,95(3):1238-1244
Antibodies to Pseudomonas testosteroni isomerase have been generated in rabbits immunized with the isomerase. Complexes between the isomerase and antibodies were characterized by double immunodiffusion and by enzymatic assays. The titre of antibodies was determined. The enzymatic activity was totally abolished with increasing antibody concentrations. Antibody-isomerase complexes were inactive. Total immunological identity was observed between the unpurified extract and the pure enzyme either free or bound to a competitive inhibitor. However, the denatured enzyme did not interact with antibodies. Antigenic identy could not be detected between the bacterial antibodies and the bovine adrenocortical isomerase from microsomes. 相似文献
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The sterols of Zea mays shoots were isolated and characterized by TLC, HPLC, GC/MS and 1H NMR techniques. In all, 22 4-demethyl sterols were identified and they included trace amounts of the Δ23-, Δ24- and Δ25-sterols, 24-methylcholesta-5,E-23-dien-3β-ol, 24-methylcholesta-5,Z-23-dien-3β-ol, 24-methylcholesta-5,25-dien-3β-ol, 24-ethylcholesta-5,25-dien-3β-ol and 24-ethylcholesta-5,24-dien-3β-ol. In the 4,4-dimethyl sterol fraction, cycloartenol and 24-methylenecycloartanol were the major sterol components but small amounts of the Δ23-compound, cyclosadol, and the Δ25-compound, cyclolaudenol, were recognized. These various Δ23- and Δ25-sterols may have some importance in alternative biosynthetic routes to the major sterols, particularly the 24β-methylcholest-5-en-3β-ol component of the C28-sterols. Radioactivity from both [2-14C]MVA and [methyl-14C]methionine was incorporated by Z. mays shoots into the sterol mixture. Although 24-methylene and 24-ethylidene sterols were relatively highly labelled, the various Δ23- and Δ25-sterols contained much lower levels of radioactivity, which is possibly indicative of their participation in alternative sterol biosynthetic routes. (24R)-24-Ethylcholest-5-en-3β-ol (sitosterol) had a significantly higher specific activity than the 24-methylcholest-5-en-3β-ol indicating that the former is synthesized at a faster rate. 相似文献
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病毒感染相关疾病严重威胁人类的健康,目前的抗病毒疗法难以治愈慢性病毒性感染引起的一些疾病,如获得性免疫缺陷综合征和乙型肝炎等,因此迫切需要新的治疗方法。可直接靶向遗传物质的基因编辑技术或将成为对抗病毒的有力工具。作为一种可编程的核酸酶介导的新型基因编辑技术,CRISPR/Cas9系统因其具有编辑效率高、操作简单、成本低、适用范围广等优点,而成功应用于多种人类相关疾病的研究中,也为病毒感染相关疾病的研究以及开发新的治疗方法提供了新的技术手段。主要对CRISPR/Cas9系统的作用机制以及在人类常见的病毒感染相关疾病治疗研究中的最新进展进行综述。 相似文献
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病毒感染相关疾病严重威胁人类的健康,目前的抗病毒疗法难以治愈慢性病毒性感染引起的一些疾病,如获得性免疫缺陷综合征和乙型肝炎等,因此迫切需要新的治疗方法。可直接靶向遗传物质的基因编辑技术或将成为对抗病毒的有力工具。作为一种可编程的核酸酶介导的新型基因编辑技术,CRISPR/Cas9系统因其具有编辑效率高、操作简单、成本低、适用范围广等优点,而成功应用于多种人类相关疾病的研究中,也为病毒感染相关疾病的研究以及开发新的治疗方法提供了新的技术手段。主要对CRISPR/Cas9系统的作用机制以及在人类常见的病毒感染相关疾病治疗研究中的最新进展进行综述。 相似文献
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