A cellular 3,3',5-triiodo-L-thyronine binding protein from a human carcinoma cell line. Purification and characterization

A cellular binding protein for 3,3',5-triiodo-L-thyronine (T3) was solubilized with 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate (CHAPS) from A431 human epidermoid carcinoma cells. The binding activity is T3 specific. Analysis of the equilibrium binding data indicated that the binding protein has one class of binding sites for T3 with a Kd of (17 +/- 3) nM and Bmax of (1.8 +/- 0.6) pmol/50 micrograms of protein. The pH optimum for binding is 6.8. The T3 binding protein elutes from Sephadex G-200 in an included peak which has a Stokes radius of 40 A and sediments on glycerol gradients at 3.7 S. By affinity labeling with [3,5-125I]thyroxine a protein with a molecular weight of 58,000 was specifically labeled. Its isoelectric point was determined to be 7.1, which is different from the reported pIs of other thyroid hormone binding proteins. p58 was successively purified to apparent homogeneity by chromatography on Sephadex G-200, QAE-Sephadex, SP-Sephadex, and hydroxylapatite. Approximately 50 micrograms of purified protein was obtained from 2.5 X 10(9) cells with a yield of 1.1%. The purified protein retains its binding activity. The specific binding activity is enriched by approximately 1000-fold. With the availability of a purified protein with T3 binding activity, it becomes possible to study its cellular function.     

Block duplications of a zeta-zeta-alpha-theta gene set in the rabbit alpha-like globin gene cluster

In order to understand the coordinate regulation between the alpha-like and beta-like globins during the developmental switches in hemoglobin synthesis, we have studied the rabbit alpha-like globin gene family. A cluster of six linked genes arranged 5'-zeta 1-alpha 1-theta 1-zeta 2-zeta 3-theta 2-3' has been isolated as a set of overlapping clones from a library of rabbit genomic DNA. Blot-hybridization analysis of genomic DNA not only confirms this linkage arrangement but also reveals the presence of additional zeta and theta genes. We propose that this gene cluster was generated by a block duplication of a set of alpha-like genes; the proposed duplication unit is zeta-zeta-alpha-theta. Further duplications of a zeta-zeta-theta set are also proposed to have occurred. As expected for a duplicated locus, the rabbit alpha-like gene cluster contains long blocks of internal homology. The Z homology block is about 7.2 kilobase pairs long and contains the zeta genes; the T homology block is about 4.7 kilobase pairs long and contains a theta gene. Surprisingly, both Z and T homology blocks are flanked by a common junction sequence (J) which contains a region very similar to the 3'-untranslated sequence of an alpha-globin gene. Analysis of the J sequences suggests a recombination mechanism by which the alpha gene could have been deleted from the second set of genes in the cluster (zeta 2-zeta 3-theta 2). The relationships among the genes in characterized alpha-like gene clusters in mammals are summarized. The rabbit gene cluster differs from those of other mammals principally in the loss of a gene orthologous to the human psi alpha 1 and in the block duplication of the zeta-zeta-alpha-theta gene set.     

青海省长刺双蚤一新亚种

在整理青海省蚤类标本中,发现长刺双蚤 Amphipsylla longispina Scalon, 1950一新亚种,记述如下。 长刺双蚤共和亚种 Amphipsylla longis pina gongheensis新亚种 鉴别特征 新亚种可动突前缘较直,不动突较细长,阳茎钩突端部似鸟头状;     

冷冻或切除小脑蚓部山顶(Culmen)对豚鼠“踏步自动作用”(Stepping automatism)的影响

本研究探讨部分冷冻或切除小脑蚓部(vermis)对整体豚鼠“踏步自动作用”(steppingautomatism)的影响。“踏步自动作用”由我们近年来发现的诱发踏步物质(SIS)(4-R-2,2,5,5-四(三氟甲基)-咪唑啉)所引起。结果表明部分冷冻或切除小脑蚓部的山顶(culmen,Ⅴ和Ⅳ叶)和中央叶(Centralis,Ⅲa,b)明显增强豚鼠的“踏步自动作用”。冷冻小脑不能触发,但仅能调控“踏步自动作用”。这种调控作用对自动化程度差的弱“踏步自动作用”特别显著。蚓部山顶(Ⅴ叶为主)同时调控左右前肢踏步,而一侧蚓部山顶及其半球则主要调控同侧前肢踏步。此外,本研究的结果表明当介面温度(冷冻头和小脑幕间)致冷至5℃—0℃左右,冷冻小脑便可基本模拟部分切除小脑效应。     

柚花头香化学成分的研究(一)

本文首次报道柚花的香气成分。作者利用憎水性树脂XAD-4吸附柚鲜花的头香,并以毛细管气相色谱和毛细管气相色谱-质谱-计算机联用方法研究头香的化学组分,分离鉴定了17个已知化学成分。它们是芳樟醇、β-蒎烯、β-水芹烯、橙花叔醇等。     

Some physicochemical properties of rice mitochondrial DNA

Summary Certain physicochemical properties of rice mitochondrial DNA (mtDNA) were determined. Certain low-molecular-weight mtDNA bands were found in addition to the major mtDNA band. Rice mtDNA appeared in the electron microscope as a collection of linear molecules with heterogeneous length in the range of 1–156 kb. The major distribution area was 60–105 kb. A small fraction (less than 5%) of rice mtDNA was found in the form of a circular molecule. Some molecules had the appearance of being supercoiled. Replication fork structures were found in both circular and linear mtDNA molecules. In one rice species, Jin Nante, 15 different circular molecules were found. Rice mtDNA was digested with different restriction enzymes. The total molecular weight of rice mtDNA was calculated to be about 300 kb according to the data of restriction enzyme digestion and electron microscopy.