Increased messenger RNA from protein synthesis inhibited human fibroblasts

Numerous reports have demonstrated that specific protein synthesis in response to specific inducers is markedly stimulated by a simultaneous brief exposure to protein synthesis inhibitors such as cycloheximide. This phenomenon is known as "superinduction" and is most often attributed to the accumulation of cytoplasmic messenger RNA during the inhibition period. Messenger RNA, as defined by rapid labeling, oligo (dt)-cellulose binding, and cell free protein synthesis stimulation was measured in cycloheximide treated human fibroblasts. In spite of a consistent 40% decrease in total polysomal 3H-uridine labeled RNA, a 1.5- to 2-fold increase in extractable mRNA was observed. These data provide direct evidence that protein synthesis inhibition stimulates the appearance of cytoplasmic mRNA and/or completely blocks its degradation and, are consistent with the hypothesis that mRNA accumulation partly underlies the superinduction phenomena.     

Small structural changes of chromosome 8. Two cases with evidence for deletion

The degeneration of the substantia nigra that characterises Parkinson's disease may cause an alteration in sensitivity of striatal dopamine receptors. The development of denervation supersensitivity has been held to be responsible for some of the effects of chronic levodopa therapy. The rotating rodent is an animal model commonly used to study the phenomenon of striatal dopamine receptor supersensitivity, and to investigate drugs which may prove to be beneficial in the treatment of Parkinson's disease. We have investigated as to whether long-term oral administration of levodopa to mice with unilateral destruction of striatal dopaminergic nerve terminals influences dopaminergic receptor denervation supersensitivity as judged by the circling response following systemically administered levodopa. It does not do so and the relevance of these findings to the treatment of Parkinson's disease is discussed.     

微波辅助合成甘露糖基三氯乙酰亚胺酯及其传统方法优化

甘露聚糖及甘露糖蛋白在很多生理过程中扮演重要的角色,它们的合成研究也是目前糖化学热点之一,甘露糖基三氯乙酰亚胺酯是它们合成中十分有效的糖给体。研究了甘露糖基三氯乙酰亚胺酯新型微波辅助合成方法,并对传统合成方法进行优化改进。以D-甘露糖为原料,通过全苯甲酰基化、端位选择性水解,再与三氯乙腈反应合成了2,3,4,6-四-O-苯甲酰基-β-D-甘露糖三氯乙酰亚胺酯,对传统合成方法进行了优化,使得总产率达到85%以上。同时首次通过微波辅助的方法合成了该种产物,结果表明,微波辅助合成方法产物产率是传统方法的1.12倍,合成时间缩短了15倍。     

模拟酶解大豆7S、11S蛋白及其抗氧化活性的研究

以"活性肽搜寻与蛋白模拟水解系统"为工具,选择碱性蛋白酶和中性蛋白酶对大豆7S、11S蛋白进行模拟水解,得到不同水平的抗氧化肽肽段,以重均分子量为手段,评价理论模拟与实验水解的相关性;以还原力、清除二苯代苦味酰基苯肼(DPPH·)自由基能力比较以上蛋白酶水解物的抗氧化活性.结果表明:模拟与实验水解得到的分子量分布在比例以及重均分子量方面有显著相关性(P<0.01);四种酶解产物均具有一定的抗氧化活性,其中,以7S蛋白的碱性蛋白酶产物表现出最高的还原力和DPPH·清除能力(P<0.05).     

Increasing incidence of carcinoma of the gastric cardia in Sweden from 1970 to 1985

Several American, Japanese and European centres have reported an increase in carcinoma of the gastric cardia, contrary to the general trend in the incidence of gastric cancer. The aim of this nationwide population-based study was to describe trends in the incidence of tumours of the gastric cardia in Sweden over the 16-year period from 1970 to 1985. The Swedish cancer register, which is more than 95 per cent complete, was used to identify cases. There were 1514 men and 481 women with cancer of the gastric cardia. The age-standardized rates increased in men from 1.9 per 10(5) population in 1970-1973 to 3.0 per 10(5) in 1982-1985, corresponding to a mean annual increase of 2.5 per cent (95 per cent confidence interval (c.i.) 1.6-3.4 per cent). In women, the age-standardized rates increased from 0.5 per 10(5) in 1970-1973 to 0.8 per 10(5) in 1982-1985, the mean annual increase being 0.9 per cent (95 per cent c.i. 0.0-1.8 per cent). The highest incidences were found in southern Sweden, contrary to the geographical distribution of gastric cancer in general, which shows a south-to-north gradient. The disparate epidemiological features of cancer of the cardia and gastric cancer at other sites suggest that the aetiologies may also be different. Since little is known about the aetiology of cancer of the cardia, and the incidence seems to be rising rapidly, analytical studies are urgently needed.     

ZAP-70 association with T cell receptor zeta (TCRzeta): fluorescence imaging of dynamic changes upon cellular stimulation

The nonreceptor protein tyrosine kinase ZAP-70 is a critical enzyme required for successful T lymphocyte activation. After antigenic stimulation, ZAP-70 rapidly associates with T cell receptor (TCR) subunits. The kinetics of its translocation to the cell surface, the properties of its specific interaction with the TCRzeta chain expressed as a chimeric protein (TTzeta and Tzetazeta), and its mobility in different intracellular compartments were studied in individual live HeLa cells, using ZAP-70 and Tzetazeta fused to green fluorescent protein (ZAP-70 GFP and Tzetazeta-GFP, respectively). Time-lapse imaging using confocal microscopy indicated that the activation-induced redistribution of ZAP-70 to the plasma membrane, after a delayed onset, is of long duration. The presence of the TCRzeta chain is critical for the redistribution, which is enhanced when an active form of the protein tyrosine kinase Lck is coexpressed. Binding specificity to TTzeta was indicated using mutant ZAP-70 GFPs and a truncated zeta chimera. Photobleaching techniques revealed that ZAP-70 GFP has decreased mobility at the plasma membrane, in contrast to its rapid mobility in the cytosol and nucleus. Tzetazeta- GFP is relatively immobile, while peripherally located ZAP-70 in stimulated cells is less mobile than cytosolic ZAP-70 in unstimulated cells, a phenotype confirmed by determining the respective diffusion constants. Examination of the specific molecular association of signaling proteins using these approaches has provided new insights into the TCRzeta-ZAP-70 interaction and will be a powerful tool for continuing studies of lymphocyte activation.