One-electron reduction of chromate by NADPH-dependent glutathione reductase

Electron spin resonance (ESR) measurements provide evidence for the formation of Cr(V) intermediates in the enzymatic reduction of Cr(VI) by glutathione reductase (GSSG-R) in the presence of NADPH, indicating an initial single-electron transfer step in the reduction mechanism. Depending on the pH, at least two different Cr(V) species are generated which are relatively long-lived. In addition, we have detected the hydroxyl (.OH) radical formation during the GSSG-R catalyzed reduction of Cr(VI) by spin trapping, employing 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN) as spin traps. Superoxide dismutase (SOD) causes only a minor effect on the .OH radical and Cr(V) formation, indicating that the O2- is not significantly involved in the reaction mechanism. Catalase enhances the Cr(V) formation and substantially inhibits the .OH radical formation, indicating the involvement of hydrogen peroxide (H2O2) in the reaction mechanism. Addition of H2O2 suppresses Cr(V) and enhances the .OH radical formation. Measurements involving N-ethylmaleimide show that the Cr(V) species, produced enzymatically by the reduction of Cr(VI) by GSSG-R, react with H2O2 to generate .OH radicals, which might participate in the initiation of Cr(VI) carcinogenicity.     

Ⅱ型限制性核酸内切酶NcrⅠ的研究

 在肉色诺卡氏菌C-212株Nocardia carnea C-212中筛选到一种Ⅱ型限制性核酸内切酶NcrⅠ,经与BglⅡ的λDNA降解物的酶谱比较,以及酶识别特异性和切割位点的检测,证明了NcrⅠ是已知的限制酶BglⅡ的同切限制酶,而且其切割位点也与BglⅡ相同,其为:     

Cell proteins bind specifically to West Nile virus minus-strand 3' stem-loop RNA.

The first 96 nucleotides of the 5'noncoding region (NCR) of West Nile virus (WNV) genomic RNA were previously reported to form thermodynamically predicted stem-loop (SL) structures that are conserved among flaviviruses. The complementary minus-strand 3' NCR RNA, which is thought to function as a promoter for the synthesis of plus-strand RNA, forms a corresponding predicted SL structure. RNase probing of the WNV 3' minus-strand stem-loop RNA [WNV (-)3' SL RNA] confirmed the existence of a terminal secondary structure. RNA-protein binding studies were performed with BHK S100 cytoplasmic extracts and in vitro-synthesized WNV (-)3' SL RNA as the probe. Three RNA-protein complexes (complexes 1,2, and 3) were detected by a gel mobility shift assay, and the specificity of the RNA-protein interactions was confirmed by gel mobility shift and UV-induced cross-linking competition assays. Four BHK cell proteins with molecular masses of 108, 60, 50, and 42 kDa were detected by UV-induced cross-linking to the WNV (-)3' SL RNA. A preliminary mapping study indicated that all four proteins bound to the first 75 nucleotides of the WNV 3' minus-strand RNA, the region that contains the terminal SL. A flavivirus resistance phenotype was previously shown to be inherited in mice as a single, autosomal dominant allele. The efficiencies of infection of resistant cells and susceptible cells are similar, but resistant cells (C3H/RV) produce less genomic RNA than congenic, susceptible cells (C3H/He). Three RNA-protein complexes and four UV-induced cross-linked cell proteins with mobilities identical to those detected in BHK cell extracts with the WNV (-)3' SL RNA were found in both C3H/RV and C3H/He cell extracts. However, the half-life of the C3H/RV complex 1 was three times longer than that of the C3H/He complex 1. It is possible that the increased binding activity of one of the resistant cell proteins for the flavivirus minus-strand RNA could result in a reduced synthesis of plus-strand RNA as observed with the flavivirus resistance phenotype.     

用光谱技术鉴定植物色素突变体

1983年我国报道了从γ-射线处理的“矮杆齐”大麦中得到了一株黄绿色的突变体1832C[1]。本文用光谱技术对该突变体的光合色素成分进行了鉴定。1　材料和方法　　材料为六棱裸大麦“矮杆齐”和由该品种大麦诱变形成的黄绿色突变体1832C(Mb1832C),以及作为对照的缺失Chlb的突变体大麦Chlorina-f2[2]都于3月初播种于实验田中。　　每个样品取30g新鲜的叶片,先用自来水后用蒸馏水冲洗干净。把洗净的叶片摊放在干净的纱布上吸干表面水分,剪碎,加入100mL预冷的含有0.4mol/L山梨醇、0.1mol/LTris-HCl(pH7.6)的缓冲液,用组织捣碎机先慢速捣碎1…     

百合离体生殖细胞骨架的扫描电镜观察

从百合的花粉管分离出来的生殖细胞,经表面活化剂Ｔｒｉｔｏｎ Ｘ－１００ 及核糖核酸酶、硫酸铵离析处理。离析后的细胞经临界点干燥,扫描电镜观察显示：在离体生殖细胞的胞质内有一个非常复杂的支架网络系统。这一网络系统有内外两层：外层（靠近细胞膜）网络结构紧密,纤维束粗长;内层（靠近核）网络结构疏松,纤维束短细。一些间接证据显示,这一支架网络系统可能为微管骨架     

蜜蜂脑中5—HT，GABA，Ach免疫反应阳性神经元分布的比较研究

通过免疫细胞化学方法－ＰＡＰ法,研究了中华峰（Ａｐｉｓｓｉｎｅｎｓｉｓ）和意大利峰（ＡｐｉｓｍｅｌｌｉｆｅｒａＬ）脑和视叶中乙酰胆碱（Ａｃｈ）、５－羟色胺（５－ＨＴ）、γ－氨基丁酸（ＧＡＢＡ）免疫反应阳性神经元胞体和纤维的形态、染色强度、分布和各种神经丛之间的联系．一方面将这些阳性分布系统和蜜蜂脑中相应的神经元类型进行比较,另一方面也分析了在一些特殊解剖学通路中存在的可能的神经递质及其作用．     

KM－1d突变株小鼠的模型建立及遗传分析

在饲养经剖腹产净化后的ＫＭ种群时,我们发现了一些后肢畸形的动物、通过挑选后已成为一个稳定遗传的突变株,由于此群体产生的后代１００％均为后肢畸形动物,因此可以认定为１ｄ／１ｄ纯合子动物。命名为ＫＭ—１ｄ小鼠。将ＫＭ－１ｄ纯合子动物与近交系ＤＢＡ／２小鼠杂交得到Ｆ１代,再经Ｆ１代互交或与双亲回交。通过对后代的形态学观察及遗传方式的分析,证明为常染色体隐性单基因遗传。另外,对１３８只ＫＭ－１ｄ畸形小鼠进行解剖观察还发现有４２％的动物在骨骼畸形的同时伴有左侧泌尿系统畸形。因此可以认定ＫＭ－１ｄ小鼠是一种患有骨－肾先天性畸形综合症的动物模型。     

DNA Fragmentation Induced by Cytotoxic T Lymphocytes Can Result in Target Cell Death

Cytotoxic T lymphocyte (CTL)-mediated lysis is accompanied by fragmentation of target cell DNA into an oligonucleosome ladder, a hallmark of apoptosis. Is this a fortuitous coincidence, or could CTL be inducing lysis by activation of the suicide signal? In this report we demonstrate that CTL-mediated target cell death can be blocked with the drug aurintricarboxylic acid (ATA). The abrogation of death correlates with the inhibition of DNA fragmentation. While ATA prevented DNA fragmentation, it failed to significantly alter protein, RNA, or DNA synthesis in the cell lines over the dose range used. In addition, there was no inhibition of cell-cell interaction or granule exocytosis during CTL-mediated killing. ATA also significantly inhibited the cytolysis and DNA fragmentation mediated by isolated cytolytic granules, as well as the granular protein fragmentin. We developed an assay in which target cells could be separated from CTL after binding and programming for lysis. Once they had received the "kiss of death," target cells could be rescued from lysis (as indicated by inhibition of DNA fragmentation and increased target cell viability) by treatment with ATA. These results suggest that ATA blocks target cell death by inhibition of DNA fragmentation, and further, that chromatin degradation is a cause rather than a result of cell death in CTL-mediated lysis.     

巨噬细胞激活及钙作用的初步研究

经TG诱发的小鼠腹腔渗出液的巨噬细胞及人的巨噬细胞样细胞株U937受PAF(100ng ml).Zymosan A(0.25mg ml).Can A(50μg ml)LPS(1μg ml)等作用后.能引起胞内游离Ca~(2-)浓度的增加,巨噬细胞内酸性磷酸酶增多,细胞骨架更为舒展、丰满.胞内游离Ca~(2-)的增加是由于胞内钙库的释放与胞外钙的内流.上述困子作用后,可使巨噬细胞产生呼吸爆发.其中.Zymosan A的作用尤为强烈.同时还出现胞膜流动性的降低、当胞外环境中有Ca~(2-)时.可增强巨噬细胞的呼吸爆发.以上提示:在巨噬细胞的激活中Ca~(2-)具有重要的作用.