Glycolipid- and glycoprotein-based blood group A antigen expression in human thrombocytes. A1/A2 difference

Total non-acid glycolipid fractions and total sodium dodecylsulphate (SDS) solubilized protein fractions were isolated from human thrombocytes obtained from single human donors having different blood group A₁/A₂ phenotypes. The blood group A glycolipid antigens were characterized by immunostaining of thin layer plates with different monoclonal anti-A antibodies. The glycoproteins carrying blood group A epitopes were identified by SDS-PAGE and Western blot analysis using a monoclonal anti-A antibody. Blood group A glycolipid antigens were found in both A₁ and A₂ thrombocytes but the A₂ individuals expressed at least ten times less A glycolipids compared to the A₁ individuals. Expression of A type 3/4 chain and small amounts of A type 1 chain glycolipids were seen in thrombocytes of both A₁ and A₂ individuals, while the type 2 chain A glycolipids appeared to be missing from the A₂ thrombocytes. Blood group A reactive glycoproteins were only found in thrombocytes of A₁ individuals and could not be detected in A₂ individuals or a blood group O individual. The major blood group A glycoprotein were found as a double band migrating in the 130 kDa region.Abbreviations SDS sodium dodecyl sulfate - PAGE polyacrylamide gel electrophoresis - HPTLC high performance thin layer chromatography - CBB Coomassie brilliant blue - GVH graft versus host Part of this work was presented at the Xth International Symposium on Glycoconjugates, Jerusalem, Israel. September, 1989.In the short hand designation for glycolipids, the letter indicate blood group determinant, the first numeral, the number of sugar residues, and the second numeral, the type of carbohydrate chain. Thus, A-6-1 means a hexaglycosylceramide with a blood group A determinant based on the type 1 carbohydrate chain.     

香薷中的化学成分

从香[Eltholtzia ciliata(Thund.)Hyland]中分出14个化合物,用波谱和化学等方法确定为6-甲基三十三烷(Ⅰ),13-环己基二十六烷(Ⅱ),β-谷甾醇(Ⅲ),棕榈酸(Ⅳ_a),亚油酸(Ⅳ_b),亚麻酸(Ⅳ_c),熊果酸(Ⅴ),5-羟基-6、7-二甲氧基黄酮(Ⅵ),5-羟基-7、8-二甲氧基黄酮(Ⅶ),5、7-二羟基-4′-甲氧基黄酮(Ⅷ),5-羟基-7、4′-二甲氧基双氢黄酮醇(Ⅸ),β-谷甾醇-3-β-D-葡萄糖甙(Ⅹ),5-羟基-6-甲基-7-O-α-D-半乳吡喃糖双氢黄酮甙(Ⅺ),刺槐素-7-O-β-D-葡萄糖甙(Ⅻ)。其中化合物Ⅺ为新化合物,除(Ⅳ_b)和(Ⅳ_c)外,其余为首次从该属植物中得到。     

北京地区大葱和玉米根际VA菌根的季节变化及其与环境因子之间的关系

1986-1987年连续两年系统调查了北京地区大葱(Allium fistulosum L.)和玉米(Zeamays L.)根际 VA 菌根侵染百分率及菌根真菌孢子密度的季节变化。分析了菌根和菌根真菌的发生与几种土壤因子(土壤硝态氮、铵态氮、速效磷和有机质含量,土壤 pH 值)和气候因子(气温、积温、土温、光照、降水量,相对湿度等)之间的关系。结果表明:大葱和玉米的侵染百分率随作物生育期的增长而增加,并以6月和9月的增长速度最快。一年中,植物根际菌根真菌的孢子密度有二个高峰,分别在6-7月和10月。在北京的同一地区,一年中,几种测定的土壤因子变化很小,因此,认为气候因子对菌根发生的季节变化具有更大的影响。用线性相关和关联度分析的结果表明:一年中,菌根的发生与积温的关系最为密切。     

Recombinational resolution in primate cells of two homologous human DNA segments with a gradient of sequence divergence.

Human alpha-thalassemia-2 genotype -alpha 4.2 is the result of meiotic recombination between two 1.3 kb long, homologous DNA segments, X(alpha 2) and X(alpha 1), located in the adult alpha globin locus. The two segments can also undergo intramolecular recombination on extrachromosomal vectors transfected into mitotically dividing primate cells (COS 7). The existence of a gradient of sequence divergence between X(alpha 2) and X(alpha 1) makes them an interesting system to study the relationship between efficiencies of homologous DNA recombination and the extent of dispersed and localized base mismatches. By partial restriction mapping and DNA sequencing of plasmids recombined in COS 7 cells and rescued from bacteria HB 101, we have determined the distribution of recombinational resolution sites along the two X blocks. Most, if not all, of the homologous recombination events between the two X blocks appear to be single crossing-over without efficient gene correction or repair of base mismatches. The distribution of the sites of recombinational resolution is inversely correlated with that of the gradient of sequence divergence, with only approximately 7% of the X recombinants resolved within the 3' third of the X blocks where two diverged Alu family repeats reside. The Alu sequence within which one of the X recombinants resolved is homologous to a previously characterized alpha thalassemia deletion point.     

Loss of CpG dinucleotides from DNA. VI. Methylation of mitochondrial and chloroplast genes

From nucleotide sequences of mitochondrial and chloroplast genes the probable frequency of the CpG----TpG + CpA substitutions was determined. These substitutions may indicate the level of prior DNA methylation. It was found that the level of this methylation is significantly lower in mitochondrial DNA (mtDNA) and chloroplast DNA (chDNA) than in nuclear DNA (nDNA) of the same species. The species (taxon) specificity of mtDNA and chDNA methylation was revealed. A correlation was found between the level of CpG methylation in nDNA, and mtDNA and chDNA in different organisms. It is shown that cytosine residues in CpG were not subjected to significant methylation in the fungi and invertebrate mtDNA and also in the algae chDNA. In contrast, the vertebrate mtDNA bears the impress of CpG-supression, which is confirmed by direct data on methylation of these DNA. Here the first data on the possible enzymatic methylation of the plant mtDNA and chDNA were obtained. It was shown that the degree of CpG-suppression in the 5S rRNA nuclear genes of lower and higher plants is significantly higher in the chloroplast genes of 4,5S and 5S rRNA. From data on pea chDNA hydrolysis with MspI and HpaII it was established that in CCGG sequences this DNA is not methylated. The role of DNA methylation in increasing the mutation rate and in accelerating the evolutionary rates of vertebrate mtDNA is discussed.     

A developmentally regulated hydroxyproline-rich glycoprotein in maize pericarp cell walls

We have studied the accumulation of peptidyl hydroxyproline in the pericarp of developing maize (Zea mays L., Golden cross Bantam sweet corn) kernels. Although this hydroxyproline accumulates throughout development, it is most soluble and its content per milligram dry weight greatest at midmaturation stages of development. Salt-soluble proteins containing this hydroxyproline from isolated cell walls of developing kernels were fractionated on a CsCl density gradient and on a Chromatofocusing column, resulting in the purification of an hydroxyproline-rich glycoprotein, PC-1. PC-1 is a basic protein of approximately 65 to 70 kilodaltons in molecular weight with an isoelectric point of at least 10.2 and a density of 1.38 to 1.39 in CsCl. Amino acid composition data indicate that it is rich in hydroxyproline, threonine, proline, lysine, and glycine. Its relation to dicot extensin is discussed.     

大剂量~(60)Co照射后造血干细胞潜在的残留损伤

本文对受到临界全致死剂量——8.5Gy~(60)Co照射后的小鼠造血干细胞(HSC)的自我更新力进行了测试,并对照射后4个月,造血功能业已恢复的小鼠HSC的造血重建功能进行了研究。结果表明:应用骨髓连续移植实验所测得的照后3个月中骨髓CFU_s的自我更新潜能明显衰退了。用照射后造血恢复小鼠的CFU_s给全致死剂量照射的受体进行移植治疗,发现其移植效力比正常的显著减弱。在受体存活30天时,CFU_s的再生速率只有正常的1/17。通过对性染色体追踪观察的资料分析,此种小鼠的??造血细胞在受体中难以形成长期稳定的嵌合体。以上事实反映出,照射后小鼠的HSC的造血重建功能大大削弱了,揭示出残存干细胞质量上的缺陷。对于这种潜在的残留损伤的机制,从“干细胞增殖力耗竭学说”和“基因自我修整假说”的角度进行了讨论。