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521.
Summary The eggs of a sea hare,Aplysia kurodai, contained antibacterial factors which probably play a role in the defense of eggs against bacterial infection. The active factors were composed of several heat-labile proteins, unrelated to lysozyme, and were produced in the albumen gland. 相似文献
522.
Plasmodium falciparum strain-specific antibody blocks binding of infected erythrocytes to amelanotic melanoma cells 总被引:3,自引:0,他引:3
An important feature of Plasmodium falciparum malaria which differentiates it from other human malarias is that erythrocytes infected with trophozoites and schizonts are not present in the peripheral blood but are sequestered along capillary and venular endothelium. Infected erythrocytes attach via parasite-induced ultrastructural modifications on the surface of the infected cells, called 'knobs'. This sequestration may be important for parasite survival because it prevents infected erythrocytes from circulating through the spleen where they could be eliminated. We have established an in vitro correlate of sequestration and used it to demonstrate that immune sera from repeatedly infected Aotus monkeys inhibit binding of infected erythrocytes to endothelial cells. We have investigated whether antiserum that blocks binding of one isolate of P. falciparum to target cells can block or reverse binding of other isolates. We report here that sera which block or reverse binding are strain-specific, indicating that the corresponding antigens on the surface of the infected erythrocytes are strain (isolate)-specific. 相似文献
523.
Comparison of the survival, fecundity and offspring size of Glossina palpalis palpalis females fed reconstituted oven-dried blood, fresh, frozen/thawed, or reconstituted freeze-dried blood showed that oven-drying at 45 degrees C does not diminish the nutritional quality of blood. The significance of this finding is discussed with a view to optimizing costs and conditions of blood-diet storage and transportation in the context of mass-rearing of tsetse flies. 相似文献
524.
Optically active benzo[c]phenanthrene diol epoxides bind extensively to adenine in DNA 总被引:2,自引:0,他引:2
Reactions of diol epoxide metabolites of carcinogenic polycyclic aromatic hydrocarbons with DNA are thought to initiate the carcinogenic process. Although formation of a benzo[a]pyrene (BaP) diol epoxide-deoxyguanosine adduct has been held responsible for biological activity, the more potent carcinogen, 7,12-dimethylbenz[a]anthracene (DMBA) binds extensively to deoxyadenosine residues in DNA, suggesting that hydrocarbon carcinogen-deoxyadenosine adducts may be instrumental in tumour initiation. Because the bay region diol epoxides of benzo[c]phenanthrene (BcPh) are very active tumour initiators, and the relative activities of the four configurationally isomeric 3,4-diol 1,2-epoxides (Fig. 1) are known, we examined their reactions with DNA. Each BcPh diol epoxide isomer exhibits a remarkable preference for covalent binding to DNA over hydrolysis, each yields a unique distribution of products with the nucleosides of DNA and each reacts extensively with deoxyadenosine residues in DNA. The relative tumour initiating activities of these stereoisomers is best reflected by the relative yields of one of the deoxyadenosine adducts formed. 相似文献
525.
The efficacy of different hexacyanoferrates(II) in preventing the enteral absorption of 134Cs was studied in piglets. As compared to the controls, oral application of 134Cs together with KFe[Fe(CN)6], NH4Fe[Fe(CN)6], or Fe4[Fe(CN)6]3 resulted in a strong reduction of the 134 Cs-uptake by more than 97%. The decrease in enteral absorption depends on the dose of administered hexacyanoferrate(II), whereas differences between the compounds under study were small. The biological half-life of 134Cs in non-hexacyanoferrate(II) treated piglets was 21.6 +/- 3.3 days (mean +/- SD). 相似文献
526.
Complementary DNA for a novel human interleukin (BSF-2) that induces B lymphocytes to produce immunoglobulin 总被引:138,自引:0,他引:138
T Hirano K Yasukawa H Harada T Taga Y Watanabe T Matsuda S Kashiwamura K Nakajima K Koyama A Iwamatsu 《Nature》1986,324(6092):73-76
When stimulated with antigen, B cells are influenced by T cells to proliferate and differentiate into antibody-forming cells. Since it was reported that soluble factors could replace certain functions of helper T cells in the antibody response, several different kinds of lymphokines and monokines have been reported in B-cell growth and differentiation. Among these, human B-cell differentiation factor (BCDF or BSF-2) has been shown to induce the final maturation of B cells into immunoglobulin-secreting cells. BSF-2 was purified to homogeneity and its partial NH2-terminal amino-acid sequence was determined. These studies indicated that BSF-2 is functionally and structurally unlike other known proteins. Here, we report the molecular cloning, structural analysis and functional expression of the cDNA encoding human BSF-2. The primary sequence of BSF-2 deduced from the cDNA reveals that BSF-2 is a novel interleukin consisting of 184 amino acids. 相似文献
527.
528.
Myelin-associated glycoprotein (MAG) is a quantitatively minor component in both peripheral and central myelin sheaths that is thought to have a role in cell-cell interactions within the nervous system. We show here that a mouse monoclonal antibody, HNK-1, which is directed against human natural killer cells also recognizes an antigenic determinant of human central and peripheral nervous system white matter by immunoperoxidase staining of tissue sections. Immunoblot analysis of myelin proteins and purified extracted MAG indicates that the antigen recognized is MAG. 相似文献
529.
There is now good evidence that cytoplasmic pH (pHi) may have an important role in the metabolic activation of quiescent cells. In particular, growth stimulation of mammalian fibroblasts leads to a rapid increase in pHi (refs 3-6), due to activation of a Na+/H+ exchanger in the plasma membrane, and this alkalinization is necessary for the initiation of DNA synthesis. However, the mechanism by which mitogens activate the Na+/H+ exchanger to raise pHi is not known, although an increase in cytoplasmic free Ca2+ ([Ca2+]i) has been postulated as the primary trigger. We now present data suggesting that the Na+/H+ exchanger is set in motion through protein kinase C, a phospholipid- and Ca2+-dependent enzyme normally activated by diacylglycerol produced from inositol phospholipids in response to external stimuli. Using newly developed pH microelectrodes and fluorimetric techniques, we show that a tumour promoting phorbol ester and synthetic diacylglycerol, both potent activators of kinase C (refs 12-15), mimic the action of mitogens in rapidly elevating pHi in different cell types. Furthermore, we demonstrate that, contrary to previous views, an early rise in [Ca2+]i is not essential for the activation of Na+/H+ exchange and the resultant increase in pHi. Finally, we suggest that an alkaline pHi shift, mediated by Na+/H+ exchange, may be a common signal in the action of those hormones which elicit the breakdown of inositol phospholipids. 相似文献
530.
研制了一台动态范围为90dB以上的环境噪声自动监测及统计分析仪器。可以适用于声级起伏变化很大的环境噪声和交通噪声的全量程监测,并可以把测量结果和统计分析结果自动显示和打印出来,解决了随机性较强的环境噪声的自动监测问题。仪器內部有两只对数放大器,由于器件特性的限制,每只对数放大器的动态范围约60dB左右,但通过微处理器对双通道对数放大器的交替采样,并经过数据处理,实现了二对数放大器的测量动态范围的自动连接,这样扩大了量程(大于90dB)实现了仪器的全量程测试。 相似文献