荧光法在对-二苯氨基苯基硼酸(DPBA)对单糖的识别作用中的应用

采用荧光光谱法研究了具有分子内电荷转移性质的一种新型硼酸衍生物,对-二苯氨基苯基硼酸(DPBA)与羧甲基-β-环糊精(CM-β-CD)的包合行为,并考察了包合物DPBA在CM-β-CD存在下与四种单糖分子的识别作用,实验结果表明,DPBA与果糖,葡萄糖,半乳糖,甘露糖分子的结合计量比均为1∶1,结合常数从大到小的顺序为:D-果糖>>D-甘露糖>D-半乳糖≈D-葡萄糖.CM-β-CD对DPBA具有增溶增敏性,从而能够在水溶液中更好地对糖分子进行识别.     

Evolution of neoplastic cell lineages in Barrett oesophagus.

It has been hypothesized that neoplastic progression develops as a consequence of an acquired genetic instability and the subsequent evolution of clonal populations with accumulated genetic errors. Accordingly, human cancers and some premalignant lesions contain multiple genetic abnormalities not present in the normal tissues from which the neoplasms arose. Barrett oesophagus (BE) is a premalignant condition which predisposes to oesophageal adenocarcinoma (EA) that can be biopsied prospectively over time because endoscopic surveillance is recommended for early detection of cancer. In addition, oesophagectomy specimens frequently contain the premalignant epithelium from which the cancer arose. Neoplastic progression in BE is associated with alterations in TP53 (also known as p53) and CDKN2A (also known as p16) and non-random losses of heterozygosity (LOH). Aneuploid or increased 4N populations occur in more than 90-95% of EAs, arise in premalignant epithelium and predict progression. We have previously shown in small numbers of patients that disruption of TP53 and CDKN2A typically occurs before aneuploidy and cancer. Here, we determine the evolutionary relationships of non-random LOH, TP53 and CDKN2A mutations, CDKN2A CpG-island methylation and ploidy during neoplastic progression. Diploid cell progenitors with somatic genetic or epigenetic abnormalities in TP53 and CDKN2A were capable of clonal expansion, spreading to large regions of oesophageal mucosa. The subsequent evolution of neoplastic progeny frequently involved bifurcations and LOH at 5q, 13q and 18q that occurred in no obligate order relative to each other, DNA-content aneuploidy or cancer. Our results indicate that clonal evolution is more complex than predicted by linear models.     

Molecular characterization and expression of the gene encoding human erythroid-potentiating activity

Erythropoietin is the primary physiological regulator of erythropoiesis; however, in vitro studies have identified another class of mediators which appear to be important in stimulating erythroid progenitors. These factors have generally been referred to as burst-promoting activities (BPA), because they stimulate the growth of early erythroid progenitors referred to as burst-forming units-erythroid (BFU-E) which give rise to colonies of up to thousands of haemoglobinized cells. We recently reported purification of a burst-promoting activity from medium conditioned by the Mo T-lymphoblast cell line infected with human T-cell lymphotropic virus type II (HTLV-II). This purified glycoprotein of relative molecular mass (Mr) 28,000 also stimulates colony formation by more mature erythroid precursors (CFU-E) and is therefore referred to as erythroid-potentiating activity (EPA). Purified EPA specifically stimulates human and murine cells of the erythroid lineage, unlike murine interleukin-3 (IL-3) which stimulates precursor cells from all haematopoietic lineages. We report here the isolation of a complementary DNA molecular clone encoding EPA and its use in producing EPA in COS (monkey) cells and CHO (Chinese hamster ovary) cells. We also define the organization of the EPA gene in human DNA.     

Resistance to positional noise in human vision

Human eyes are in constant and rapid motion even when observers try to maintain steady fixation. Also, the visual system has a sluggish temporal response. In combination, these two factors would be expected to blur stimuli and reduce spatial sensitivity. But observers are able to detect a difference in separation of a few seconds of arc between two closely spaced parallel lines. Here we report that even very large amounts of positional jitter of the line pair has minimal impact on this ability. This result is in marked contrast to the deterioration observed when targets are swept linearly across the retina, but is consistent with a system that must ignore oculomotor jitter. To explain these results will require a re-evaluation of current models of position coding in human vision.     

GABAA responses in hippocampal neurons are potentiated by glutamate

In the mammalian cortex, glutamate and gamma-aminobutyric acid (GABA) are the principal transmitters mediating excitatory and inhibitory synaptic events. Glutamate activates cation conductances that lead to membrane depolarization whereas GABA controls chloride conductances that produce hyperpolarization. Here we report that the GABAA-activated conductance in hippocampal pyramidal cells is enhanced by glutamate at concentrations below that required for its excitatory action. The GABA-potentiating effect can be induced, with comparable potency, by several glutamate analogues such as quisqualate, N-methyl-D-aspartate (NMDA), kainate and, surprisingly, by D-2-amino-5-phosphonovalerate (APV), an antagonist for NMDA receptors. Data from dose-response curves show that glutamate enhances the GABAA conductance without significantly changing GABA binding affinity. The low concentration of glutamate needed to enhance GABAA responses raises the possibility that glutamate modulates the strength of GABA-mediated transmission in the cortex.     

河南浮戏山植物区系地理及其近缘关系

浮戏山有种子植物９６科３１３属５５２种，区系成分以北温带、泛热带和旧世界温带三种成分为主，其次是东亚和东亚北美间断成分，植物区系具有明显的温带性质。以植物地理成分为指标，将浮戏山和全国其它１９个地区进行系统聚类分析，结果表明，浮戏山植物区系成分和与其同处于中纬度地区的河南境内的桐柏山、大别山、小秦岭、老君山及山西中条山山东泰山最为相似，而与高纬度地区的长白山。低纬度地区的广西大瑶山和海南五指山最为