Stimulation of B-cell progenitors by cloned murine interleukin-7

The events involved in the commitment and development of lymphoid lineage cells are poorly understood. We have used a recently described long-term culture system to establish a bioassay that can detect a novel growth factor capable of stimulating the proliferation of lymphoid progenitors. Using direct expression in mammalian cells we have isolated a complementary DNA clone encoding this novel haematopoietic growth factor, designated interleukin-7.     

Expression of functional acetylcholine receptor from cloned cDNAs

The cloned cDNAs encoding the four subunits of the Torpedo californica acetylcholine receptor, each carried by a simian virus 40 vector, direct the synthesis of the functional receptor in a combined expression system consisting of COS monkey cells and Xenopus oocytes. Our results suggest that all four subunits are required to elicit a normal nicotinic response to acetylcholine, whereas only the alpha-subunit is indispensable for alpha-bungarotoxin binding activity.     

Functional characterization of a heteromeric NMDA receptor channel expressed from cloned cDNAs.

The glutamate receptor (GluR) channel plays a key part in brain function. Among GluR channel subtypes, the NMDA (N-methyl-D-aspartate) receptor channel which is highly permeable to Ca2+ is essential for the synaptic plasticity underlying memory, learning and development. Furthermore, abnormal activation of the NMDA receptor channel may trigger the neuronal cell death observed in various brain disorders. A complementary DNA encoding a subunit of the rodent NMDA receptor channel (NMDAR1 or zeta 1) has been cloned and its functional properties investigated. Here we report the identification and primary structure of a novel mouse NMDA receptor channel subunit, designated as epsilon 1, after cloning and sequencing the cDNA. The epsilon 1 subunit shows 11-18% amino-acid sequence identity with rodent GluR channel subunits that have been characterized so far and has structural features common to neurotransmitter-gated ion channels. Expression from cloned cDNAs of the epsilon 1 subunit together with the zeta 1 subunit in Xenopus oocytes yields functional GluR channels with high activity and characteristics of the NMDA receptor channel. Furthermore, the heteromeric NMDA receptor channel can be activated by glycine alone.     

Molecular cloning and expression of cDNAs for the human interleukin-2 receptor

We have purified the human T-cell growth factor (interleukin-2) receptor and have cloned, sequenced and expressed cDNAs corresponding to this receptor. We identify one gene, but two interleukin-2 receptor mRNAs which differ in their polyadenylation signals. We have isolated an additional cDNA that may correspond to an alternatively spliced mRNA that lacks a 216 base segment and appears to encode an altered membrane protein which cannot bind interleukin-2.     

Structure and expression of a cloned cDNA for human interleukin-2

A cDNA coding for human interleukin-2 (IL-2) has been cloned from a cDNA library prepared from partially purified IL-2 mRNA. The DNA sequence codes for a polypeptide which consists of 153 amino acids including a putative signal sequence. A biologically active polypeptide, characteristic of human IL-2, was produced when the cDNA was fused to a simian virus 40 promoter sequence and used to transfect cultured monkey COS cells.     

Primary structure of Torpedo californica acetylcholinesterase deduced from its cDNA sequence

Acetylcholinesterase, an essential enzyme of the nervous system, rapidly terminates the action of acetylcholine released into the synapse. Acetylcholinesterase is also found (in lower abundance) in extrajunctional areas of muscle and nerve and on erythrocyte membranes. Hydrodynamic analyses of the native enzyme and characterization of its dissociated subunits have revealed multiple enzyme forms which can be divided into two classes: dimensionally asymmetric forms which are usually found within the synapse and contain a collagen-like structural subunit disulphide-linked to the catalytic subunits; and globular forms which appear to be widely distributed on the outer surface of cell membranes. Both forms have been characterized in the ray Torpedo californica and, although their catalytic behaviours seem to be identical, they differ slightly in amino-acid composition, peptide maps and reactivity with certain monoclonal antibodies. Here, we report the complete amino-acid sequence of an acetylcholinesterase inferred from the sequence of a complementary DNA clone. The 575-residue protein shows significant homology with the C-terminal portion of thyroglobulin.     

Complete primary structure of a heterodimeric T-cell receptor deduced from cDNA sequences

Two related, but distinct, cDNA clones have been isolated and sequenced from a functional murine cytotoxic T-lymphocyte clone. The genes corresponding to these cDNA are expressed and rearranged specifically in T cells and both have similarities to immunoglobulin variable and constant region genes. It is concluded that these genes code for the two subunits of the heterodimeric antigen receptor on the surface of the T cell; its complete deduced primary structure is presented.     

Expression of murine H-2Kb histocompatibility antigen in cells transformed with cloned H-2 genes

Cosmids containing H-2 histocompatibility antigen genes of the H-2b haplotype have been isolated. One of these genes expresses a 45,000 molecular weight protein, indistinguishable from H-2Kb when introduced into mouse L cells. These H-2Kb transformed L cells can be killed by allospecific anti-H-2Kb cytotoxic T cells. Moreover, when infected with influenza virus, they can be killed by an H-2Kb-restricted, influenza virus-specific cytotoxic T cell line. These results show that expression of the H-2Kb gene product on the L-cell surface is sufficient to make it a target for specific T-cell killing.     

Nucleotide sequences of cloned cDNAs for two types of bovine brain substance P precursor

The primary structures of two types of bovine brain substance P precursors have been determined. One precursor contains a sequence homologous to that of the amphibian peptide kassinin. This new tachykinin sequence is bounded by paired basic amino acids Lys-Arg, which suggests that, like substance P, it can be liberated from the precursor and may serve as an endogenous hormone or neuromediator in mammalian organisms.     

Galaxy mass deduced from the structure of Einstein ring MG1654+1346

ELLIPTICAL galaxies acting as gravitational lenses occasionally produce spectacular images-Einstein rings-of distant objects. Giant arcs(1) and radio rings(2) have been observed. A wide variety of image morphologies is possible, the generation of which is qualitatively understood in terms of large magnifications at caustic and critical lines in the lensing geometry(3-5). From the angular size of the image, and with knowledge of the distances of the lensed and lensing object, rough estimates of the mass of the lensing galaxy can be obtained. We have made high-resolution radio-interferometric observations of MG1654 + 1346 (ref. 6) a radio quasar in near-perfect alignment with an elliptical galaxy, and show that radio emission is distorted into a narrow Einstein ring that lies within a diamond-shaped region bounded by caustic lines. From the details of the ring structure, a new model for the lensing geometry is deduced which leads to a more accurate estimate of the mass of the lensing galaxy.     

Primary structure of alpha-subunit precursor of Torpedo californica acetylcholine receptor deduced from cDNA sequence

DNA sequences complementary to the Torpedo californica electroplax mRNA coding for the alpha-subunit precursor of the acetylcholine receptor were cloned. The nucleotide sequence of the cloned cDNA indicates that the precursor consists of 461 amino acids including a prepeptide of 24 amino acids. Possible sites for acetylcholine binding and antigenic determinants on the alpha-subunit molecule are discussed.     

Primary structure of bovine thyroglobulin deduced from the sequence of its 8,431-base complementary DNA

In mammals, an adequate supply of thyroid hormones is essential for normal growth and neurological development. The biosynthesis of thyroid hormones involves an iodinated precursor protein, thyroglobulin, which may be considered an extreme example of a pro-hormone. Thyroglobulin is a dimeric glycoprotein of relative molecular mass (Mr) 660,000 (660K), which is secreted by the thyrocyte and stored in the lumen of the thyroid follicle. The hormonogenic reaction is extracellular, and involves iodination of tyrosyl residues of thyroglobulin and the intramolecular coupling of a subset of these into thyroxine (T4) and triiodothyronine (T3), which remain part of the polypeptide chain. Secretion of hormones results from the endocytosis of thyroglobulin followed by its complete hydrolysis in lysosomes. Considering that the maximum yield of hormones is approximately 6-8 per 660K protein, the whole process is apparently wasteful. However, the efficiency of thyroglobulin as a thyroid hormone precursor is extremely high when the supply of iodine is short; in such conditions, almost all the iodine incorporated is found in iodothyronine. Hence it is suggested that the thyroglobulin structure has evolved to allow for the preferential and efficient iodination and coupling of the hormonogenic tyrosines. Here we report the complete primary structure of bovine thyroglobulin, derived from the sequence of its 8,431-base-pair complementary DNA. The 2,769-amino-acid sequence is characterized by a pattern of imperfect repeats derived from three cysteine-rich motifs. Four hormonogenic tyrosines have been precisely localized near the amino and carboxyl ends of the protein.     

Molecular cloning of cDNA for murine interleukin-3

The cDNA sequence for murine interleukin-3, one of the colony stimulating factors that regulate haematopoiesis, codes for a polypeptide of 166 amino acids including a putative signal peptide. The predicted amino acid sequence indicates that formation of mature interleukin-3 involves proteolytic removal of not only the signal peptide but additional amino-terminal amino acids.     

Origins of sulphate in Antarctic dry-valley soils as deduced from anomalous 17O compositions

The dry valleys of Antarctica are some of the oldest terrestrial surfaces on the Earth. Despite much study of soil weathering and development, ecosystem dynamics and the occurrence of life in these extreme environments, the reasons behind the exceptionally high salt content of the dry-valley soils have remained uncertain. In particular, the origins of sulphate are still controversial; proposed sources include wind-blown sea salt, chemical weatherings, marine incursion, hydrothermal processes and oxidation of biogenic sulphur in the atmosphere. Here we report measurements of delta18O and delta17O values of sulphates from a range of dry-valley soils. These sulphates all have a large positive anomaly of 17O, of up to 3.4/1000. This suggests that Antarctic sulphate comes not just from sea salt (which has no anomaly of 17O) but also from the atmospheric oxidation of reduced gaseous sulphur compounds, the only known process that can generate the observed 17O anomaly. This source is more prominent in high inland soils, suggesting that the distributions of sulphate are largely explained by differences in particle size and transport mode which exist between sea-salt aerosols and aerosols formed from biogenic sulphur emission.     

从MD4衍生的HASH函数解析

HASH函数MD4的设计是不基于任何假设和密码体制的，为了增强MD4的安全性和抗攻击程度，由MD4衍生出多种HASH函数如MD5、SHA-1、RIPEMD-160等，讨论了由MD4函数衍生出的MD5、SHA-1、RIPEMD-160算法设计及其安全性，比较分析各函数的相同与不同点．     

Autoimmune diabetes as a consequence of locally produced interleukin-2.

During cell differentiation in the thymus, self-reactive T cells can be generated. The majority of these seem to be deleted after intrathymic encounter with the relevant autoantigen. As all self antigens are unlikely to be present in the thymus, some autoreactive T cells may escape censorship. Here we study the fate of these cells using transgenic mice expressing the class I molecule H-2Kb (Kb) in the insulin-producing beta-cells of the pancreas. These mice were crossed with mice transgenic for genes encoding a Kb-specific T-cell antigen receptor (TCR) which could be detected using a clonotype-specific monoclonal antibody. Although T cells expressing the highest level of transgenic TCR were deleted intrathymically in double-transgenic mice, Kb-specific T cells were detected in the periphery. These cells caused the rejection of Kb-expressing skin grafts, but ignored islet Kb antigens even after priming. But when double-transgenic mice were crossed with transgenic mice expressing the lymphokine interleukin-2 in the pancreatic beta-cells, there was a rapid onset of diabetes. These results indicate that autoreactive T cells that ignore self antigens may cause autoimmune diabetes when provided with exogenous 'help' in the form of interleukin-2.     

Generation of nuclear transfer-derived pluripotent ES cells from cloned Cdx2-deficient blastocysts

The derivation of embryonic stem (ES) cells by nuclear transfer holds great promise for research and therapy but involves the destruction of cloned human blastocysts. Proof of principle experiments have shown that 'customized' ES cells derived by nuclear transfer (NT-ESCs) can be used to correct immunodeficiency in mice. Importantly, the feasibility of the approach has been demonstrated recently in humans, bringing the clinical application of NT-ESCs within reach. Altered nuclear transfer (ANT) has been proposed as a variation of nuclear transfer because it would create abnormal nuclear transfer blastocysts that are inherently unable to implant into the uterus but would be capable of generating customized ES cells. To assess the experimental validity of this concept we have used nuclear transfer to derive mouse blastocysts from donor fibroblasts that carried a short hairpin RNA construct targeting Cdx2. Cloned blastocysts were morphologically abnormal, lacked functional trophoblast and failed to implant into the uterus. However, they efficiently generated pluripotent embryonic stem cells when explanted into culture.     

环状芽孢杆菌C-2几丁酶基因在荧光假单胞菌中的表达

将已克隆到的环状芽孢杆菌（Bacillus circulans)C-2的几丁酶基因chi1片段克隆到质粒载体pUXBF5中，得到重组质粒pUXCH1，该重组质粒在大肠杆菌中可以表达产生具有生物活性的几丁酶并分泌到胞外。将pUXCH1分别利用感受态法和三亲本杂交法转化荧光假单胞菌（Psendomonas fluorescens），在含有卡拉霉素的金氏B平板上筛得转化子。但将转化子点种于几丁质平板上却不能产生水解圈，提取细胞内容物后用比色法也没有检测到有效的酶活性。该研究表明环状芽孢杆菌 的几个酶基因chi1已经被成功的整合到荧光假单胞菌的染色体上，但却没有表达或表达效率极低，这可能是由于荧光假单胞菌的表达系统不能正确有效的识别存在于该chi1几丁酶基因片段中的环状芽孢杆菌基因启动子而造成的。     

Cloning and expression of murine interleukin-1 cDNA in Escherichia coli

Interleukin-1 (IL-1), a peptide hormone produced by activated macrophages, possesses the ability to modulate the proliferation, maturation and functional activation of a broad spectrum of cell types and may play a major role in the initiation and amplification of immune and inflammatory responses through its action on these diverse cell populations. IL-1 exhibits microheterogeneity in terms of its relative molecular mass (Mr, 13,000-19,000) and charge properties, and although murine IL-1 has been purified and some of its basic structure-function relationships have been elucidated, it has proved difficult to prepare sufficient amounts of IL-1 for direct and detailed sequence and structural studies. Here we report the cloning, sequence analysis and expression of murine IL-1 cDNA in Escherichia coli. The IL-1 cDNA codes for a polypeptide precursor of 270 amino acids. Biologically active IL-1 was produced in E. coli by expressing the carboxy-terminal 156 amino acids of the IL-1 precursor.     

Expression of interleukin-2 receptors as a differentiation marker on intrathymic stem cells

The thymus is regarded as the primary site for T-cell lymphopoiesis, but very little is known about the lineage inter-relationships of cells within that organ. At least four subpopulations of mouse thymocytes can be defined on the basis of staining with monoclonal antibodies directed against the T-cell differentiation antigens Lyt-2 and L3T4 (ref. 2). Thus immunocompetent (medullary) thymocytes, like peripheral T cells, express either Lyt-2 (cytotoxic phenotype) or L3T4 (helper phenotype) but not both, whereas non-functional (cortical) thymocytes express both markers. In addition, a small subpopulation comprising 2-3% of cells in the thymus and expressing neither Lyt-2 nor L3T4 has recently been described. The latter cells have the properties of intrathymic 'stem cells' in that they are the first to appear in the embryonic thymus and at least some can be shown to give rise, both in vivo (ref. 4. and our unpublished data) and in vitro, to other thymocyte subpopulations. We show here that 50% of Lyt-2-/L3T4- cells in the adult thymus express receptors for the polypeptide growth hormone interleukin-2 (IL-2) whereas other cells in the thymus do not. Furthermore, immunohistochemical localization studies on frozen sections indicate a disperse distribution of IL-2 receptor-positive cells in both the cortex and medulla. These novel findings have potential implications in the context of current models of differentiation pathways within the thymus.