A transgenic mouse model of sickle cell disorder

A single base-pair mutation (beta s) in codon 6 of the human beta-globin gene, causing a single amino-acid substitution, is the cause of sickle cell anaemia. The mutant haemoglobin molecule, HbS, polymerizes when deoxygenated and causes deformation of the erythrocytes to a characteristic 'sickled' shape. Sickling of cells in small vessels causes painful crises and other life-threatening complications. Although the molecular basis for sickle cell anaemia has been known for 30 years, no definitive treatment is available. An animal model of sickle cell anaemia would not only allow a detailed analysis of the factors that initiate erythrocyte sickling in vivo and of the pathophysiology of the disease, but would also permit the development of novel approaches to the treatment of the disease. By using the dominant control region sequences from the human beta-globin locus, together with human alpha- and beta s-globin genes, we have obtained three transgenic mice with HbS levels ranging from 10 to 80% of total haemoglobin in their red cells. As observed in homozygous and heterozygous Hbs patients, the erythrocytes of this mouse sickle readily on deoxygenation. Irreversibly sickled cells, which are characteristic of sickle-cell patients homozygous for beta s, are also observed in the peripheral blood of the mouse with high levels of HbS.     

Nucleation and growth of fibres and gel formation in sickle cell haemoglobin

Deoxygenated sickle haemoglobin polymerizes into long 210-A diameter fibres that distort and decrease the deformability of red blood cells, and cause sickle cell disease. The fibres consist of seven intertwined double strands. They can form birefringent nematic liquid crystals (tactoids) and spherulites. Rheologically, the system behaves as a gel. The equilibria show a phase separation and a solubility. The reaction kinetics show a delay time, are then roughly exponential and are highly dependent on concentration and temperature, and accord with the double nucleation model. But these conclusions are derived from macroscopic data, without direct observation of individual fibres. We have now used non-invasive video-enhanced differential interference contrast (DIC) and dark-field microscopy to observe nucleation, growth and interaction of sickle deoxyhaemoglobin fibres in real time. The fibres originate both from centres that produce many radially distributed fibres and on the surface of pre-existing fibres, from which they then branch. The resulting network is cross-linked and dynamic in that it is flexible and continues to grow and cross-link. Our results support most aspects of the double nucleation model.     

雷达回波的奇异性检测及目标识别

讨论了信号中奇异性的测度——Ｌｉｐｓｃｈｉｔｚ指数，分析了子波变换与Ｌｉｐｓｃｈｉｔｚ指数的内在联系，给出了使用子波变换计算信号的Ｌｉｐｓｃｈｉｔｚ指数的方法以及Ｌｉｐｓｃｈｉｔｚ指数在实际应用中的物理背景和意义。结合Ｌｉｐｓｃｈｉｔｚ指数及其检测方法，对三类飞机的雷达回波数据进行了实验模拟。通过计算回波波元的Ｌｉｐｓｃｈｉｔｚ指数来构造特征向量，并使用人工神经网络进行分类识别，给出识别的模拟结果。结果表明检测雷达回波波元的Ｌｉｐｓｃｈｉｔｚ指数进行雷达目标识别是一个有效的尝试。     

应用光敏生物素探针检测杂交瘤及细胞中的小鼠白血病病毒

采用ＢａｍＨＩ酶切和琼脂糖凝胶电泳技术，从重组质粒ＰｓＦｌｌ中回收５ｋｂ小鼠白血病病毒（ＭｕＬＶ）ＤＮＡ片段，经光敏生物素标记后制备ＤＮＡ探针，以斑点杂交法检测杂交瘤细胞、ＭｃＡｂ纯品以及ＳＰ２／０细胞中的ＭｕＬｖ。结果表明：此探针灵敏度可达２５ｐｇ，特异性好，在被检测的１３株杂交瘤细胞和２株ＳＰ２／０细胞中分别查出５株和１株为ＭｕＬｖ阳性，ＭｃＡｂ纯品中未发现ＭｕＬｖ。     

Detection of P-glycoprotein in multidrug-resistant cell lines by monoclonal antibodies

One reason for the failure of chemotherapy in the treatment of advanced cancers may be the outgrowth of multidrug-resistant tumour cells. Multidrug resistance has been modelled in numerous mammalian cell lines in which the phenotype is characterized by a pleiotropic cross-resistance to unrelated drugs. In the study reported here, we have produced monoclonal antibodies whose binding to plasma membranes of different multidrug-resistant mammalian cells correlates with the degree of drug resistance. All these antibodies are specific for P-glycoprotein, a cell surface component of relative molecular mass (Mr) 170,000 (170K) that has been described previously, and are directed against three spatially distinct epitopes which define a conserved cytoplasmic domain in the C-terminal region of the P-glycoprotein polypeptide. The conserved nature of P-glycoprotein and its low-level expression is drug-sensitive cells suggest that it has an important function at the cell surface. The monoclonal antibodies against P-glycoprotein described here might serve as diagnostic reagents for clinically unresponsive tumours.     

alpha-Chain contacts in the polymerisation of sickle haemogloblin.

Five new double-mutant haemoglobins composed of betaS chains and alpha chains with different substitutions, which are located at the surface of the tetramer, have been prepared. Although all the hybrids are more soluble than deoxyhaemoglobin S, the individual differences between these molecules make it possible to evaluate several regions on the alpha chains for intermolecular contacts in the polymerisation of deoxyhaemoglobin S.