Met-enkephalin-Arg6-Phe7, present in high amounts in brain of rat, cattle and man, is an opioid agonist

The enkephalins Met-enkephalin and Leu-enkephalin were first isolated from porcine brain by Hughes and co-workers. We have recently isolated from bovine adrenals another enkephalin with the structure Tyr-Gly-Gly-Phe-Met-Arg-Phe, or Met-enkephalin-Arg6-Phe7 (ref. 2). We report here that this new heptapeptide is found in human, rat and bovine striatum in concentrations comparable with or greater than that of Leu-enkephalin. This molecule should not be considered as a mere precursor of Met-enkephalin. A pharmacological study indicates that this naturally occurring enkephalin has similar properties to the two enkephalins characterized earlier.     

Presence in brain of synenkephalin, a proenkephalin-immunoreactive protein which does not contain enkephalin

The primary sequence of adrenal proenkephalin has recently been reported by three groups who have isolated and sequenced the cDNA for this prohormone. Several intermediates in the processing of proenkephalin, containing from one to four copies of [Met] enkephalin, have been purified from the adrenal medulla. Although there is evidence that the proenkephalin is identical in the brain and the adrenal medulla, similar intermediates have not been isolated from brain. We report here the production of an antiserum directed against a purified enkephalin precursor derived from the amino terminus of adrenal proenkephalin which cross-reacts with an antigen in brain. The immunoreactive protein in brain does not contain the sequence of enkephalin, but shows a pattern of distribution in immunohistochemical studies parallel to that of the enkephalins. In extracts of bovine caudate-putamen, this antigen is present in a molar concentration approximately one-fifth of that of [Met] enkephalin. The results demonstrate that the antiserum recognizes antigenic determinants within the N-terminal 72 amino acid residues of adrenal proenkephalin and that the enkephalin precursor in brain is similar to that found in the adrenal medulla. Furthermore, the absence of the enkephalin sequence in the brain protein indicates that concentrations of the larger intermediates in the processing of proenkephalin are much lower in the brain than in the adrenal medulla.     

Limitation of the size of the vulval primordium of Caenorhabditis elegans by lin-15 expression in surrounding hypodermis

In the nematode Caenorhabditis elegans six hypodermal cells, the vulval precursor cells, are each competent to generate vulval cells. Normally only the three nearest precursor cells to the uterine anchor cell generate the vulva (22 nuclei), while the three others fuse with the non-specialized hypodermal syncytium (hyp7) surrounding each precursor cell and covering the body. Without an inductive signal from the anchor cell, all six vulval precursor cells fuse with hyp7 and no vulva is formed. But without activity of the vulval determination gene lin-15(+), all six cells undergo vulval divisions whether the anchor cell is present or not. Using mosaic analysis, we demonstrate here that lin-15(+) expression is necessary in cells other than the vulval precursor cells or the anchor cell, most probably in the hyp7 syncytium. We propose that lin-15(+) is active in hyp7 in order to repress an intrinsic vulval program in the precursor cells. The inductive signal from the anchor cell counteracts this repression for three precursor cells, allowing them to generate vulval cells. Such a two-signal (repressor/derepressor) mechanism may operate in other cases of tissue induction.     

Characterization and <Emphasis Type="Italic">in-situ</Emphasis> formation mechanism of tungsten carbide reinforced Fe-based alloy coating by plasma cladding

The precursor carbonization method was first applied to prepare W-C compound powder to perform the in-situ synthesis of the WC phase in a Fe-based alloy coating. The in-situ formation mechanism during the cladding process is discussed in detail. The results reveal that fine and obtuse WC particles were successfully generated and distributed in Fe-based alloy coating via Fe/W-C compound powders. The WC particles were either surrounded by or were semi-enclosed in blocky M₇C₃ carbides. Moreover, net-like structures were confirmed as mixtures of M₂₃C₆ and α-Fe; these structures were transformed from M₇C₃. The coarse herringbone M₃C carbides did not only derive from the decomposition of M₇C₃ but also partly originated from the chemical reaction at the α-Fe/M₂₃C₆ interface. During the cladding process, the phase evolution of the precipitated carbides was WC → M₇C₃ → M₂₃C₆+M₃C.     

Molecular cloning establishes proenkephalin as precursor of enkephalin-containing peptides

Molecular cloning and DNA sequencing have yielded considerable structural information about proenkephalin. All previously characterized intermediate peptides of the enkephalin pathways in bovine adrenal medulla have now been aligned into an unambiguous primary structure. Two basic amino acid residues serve as processing signals for release of each of the different components.     

Crystal structure of leucine-enkephalin

The crystal structure of leucine-enkephalin has been determined in a crystal form that has four independent enkephalin molecules and much water and dimethylformamide solvent in the asymmetric unit. All four enkephalins have extended peptide backbones with the Tyr, Phe and Leu side chains above and below the plane of the backbone. There is evidence that this extended conformation may provide an acceptable model for enkephalin binding to opiate mu-receptors.     

用共沉淀法合成烧绿石型氧化物Y_2Sn_2O_7的过程研究

本文用 TG—DTA,IR,Raman 和 XRD 等手段研究了共沉淀法合成烧绿石型复合氧化物 Y_2Su_2O_7的过程.实验结果表明,溶液中 Y~(3+)和 SnCl_6~(2-)离子可能同时沉淀,各自形成微晶,随后相互作用形成复合胶体微晶,形成共沉淀的初始产物 YSn_2.它的 X 射线衍射是非晶态的.对YSn_2进行热处理时,Y 和 Sn 的氧化物发生固体反应.最后生成烧绿石型复合氧化物 Y_2Sn_2O_7粉晶.     

铈—钼复合氧化物超微粒子的合成

以硝酸铈和钼酸铵为原料,采用溶胶-凝胶法和微波加热技术制备了Ce2（MoO4）3超微粒子催化剂,使用DTA-TG、IR、XRD以及BET比表面测试等表征手段,考察了制备条件对复合氧化物超微粒子形成、晶相和比表面积的影响,结果表明：制备Ce2(MoO4)3超微粒子的适宜条件为：初始溶液pH=1.0,柠檬酸/（铁 钼）摩尔比等于0.4,在此条件下制得的干凝胶,经微波加热处理后,粒子的比表面积为35.8m^2/g,粒径约为40nm。     

An abundant population of small irregular satellites around Jupiter

Irregular satellites have eccentric orbits that can be highly inclined or even retrograde relative to the equatorial planes of their planets. These objects cannot have formed by circumplanetary accretion, unlike the regular satellites that follow uninclined, nearly circular and prograde orbits. Rather, they are probably products of early capture from heliocentric orbits. Although the capture mechanism remains uncertain, the study of irregular satellites provides a window on processes operating in the young Solar System. Families of irregular satellites recently have been discovered around Saturn (thirteen members, refs 6, 7), Uranus (six, ref. 8) and Neptune (three, ref. 9). Because Jupiter is closer than the other giant planets, searches for smaller and fainter irregular satellites can be made. Here we report the discovery of 23 new irregular satellites of Jupiter, so increasing the total known population to 32. There are five distinct satellite groups, each dominated by one relatively large body. The groups were most probably produced by collisional shattering of precursor objects after capture by Jupiter.     

h-BN前驱体的制备与研究

实验以硼酸铵和三聚氰胺为原料,考察了反应原料配比,反应物总浓度对湿化学法制备氮化硼前驱体的影响,确定了制备前驱体的适宜原料配比是n（C3N6H6）：n（NH4HB4O7·3H2O）=1：1,总浓度为0.5mol/L;并通过FT-IR、XRD、化学分析、元素分析和SEM等方法对前驱体进行了表征,研究结果表明：该方法制备的氮化硼前驱体是通过分子间氢键形成的组成为C3N6H6·2H3BO3的超分子棒状加合物,在空气气氛中950℃下高温培烧4h能得到晶化程度良好的六方氮化硼粉体.     

Two transmembrane aspartates in presenilin-1 required for presenilin endoproteolysis and gamma-secretase activity

Accumulation of the amyloid-beta protein (Abeta) in the cerebral cortex is an early and invariant event in the pathogenesis of Alzheimer's disease. The final step in the generation of Abeta from the beta-amyloid precursor protein is an apparently intramembranous proteolysis by the elusive gamma-secretase(s). The most common cause of familial Alzheimer's disease is mutation of the genes encoding presenilins 1 and 2, which alters gamma-secretase activity to increase the production of the highly amyloidogenic Abeta42 isoform. Moreover, deletion of presenilin-1 in mice greatly reduces gamma-secretase activity, indicating that presenilin-1 mediates most of this proteolytic event. Here we report that mutation of either of two conserved transmembrane (TM) aspartate residues in presenilin-1, Asp 257 (in TM6) and Asp 385 (in TM7), substantially reduces Abeta production and increases the amounts of the carboxy-terminal fragments of beta-amyloid precursor protein that are the substrates of gamma-secretase. We observed these effects in three different cell lines as well as in cell-free microsomes. Either of the Asp --> Ala mutations also prevented the normal endoproteolysis of presenilin-1 in the TM6 --> TM7 cytoplasmic loop. In a functional presenilin-1 variant (carrying a deletion in exon 9) that is associated with familial Alzheimer's disease and which does not require this cleavage, the Asp 385 --> Ala mutation still inhibited gamma-secretase activity. Our results indicate that the two transmembrane aspartate residues are critical for both presenilin-1 endoproteolysis and gamma-secretase activity, and suggest that presenilin 1 is either a unique diaspartyl cofactor for gamma-secretase or is itself gamma-secretase, an autoactivated intramembranous aspartyl protease.     

微片结构Gd3GaO6：Eu3＋荧光粉的合成及其发光特性

以柠檬酸为燃烧剂,乙二醇为分散剂采用燃烧固相法制备Gd3GaO6：Eu3＋新型荧光粉．利用X线粉末衍射、扫描电镜和荧光光谱分别对热处理后产物的结构、形貌和发光性能进行表征．结果表明：700℃燃烧10min并在1200℃热处理5h即可获得产物Gd3GaO6：Eu3＋,其空间点群为P21（4）,形貌为微米片结构;产物的特征发射峰来自于Eu3＋的5D0→7FJ（J=1,2,3,4）跃迁,其中在616nm处发射最强,为Eu3＋的。5D0→7F2的特征红色发射;宽激发带主要来自于O2-→Eu3＋的荷移跃迁吸收．该产物是一种性能优良的红色荧光粉．     

The protein-coding sequence of the bovine ACTH-beta-LPH precursor gene is split near the signal peptide region

The pituitary hormones corticotropin (ACTH) and beta-lipotropin (beta-LPH) are formed from a large common precursor. Recently, we have elucidated the whole primary structure of the bovine ACTH-beta-LPH precursor (designated alternatively as preproopiocortin) by determining the nucleotide sequence of cloned DNA complementary to the mRNA coding for the precursor protein. The amino acid sequence assigned has disclosed a characteristic repetitive structure of the ACTH-beta-LPH precursor. The repetitive units of the precursor protein each contain a melanotropin (MSH) sequence (alpha-, beta- or gamma-MSH) as well as other peptide components such as beta-endorphin and corticotropin-like intermediate lobe peptide (CLIP). The repetitive units as well as their peptide components are each bounded by paired basic amino acid residues, which apparently represent the sites of proteolytic processing. Several studies have confirmed the translational initiation site and protein structure assigned (see also ref. 11 and refs therein). In view of the recent knowledge about the organization of eukaryotic genes (see refs 12, 13 for reviews), it would be of particular interest to investigate the relationship between the repetitive structure of the ACTH-beta-LPH precursor containing different functional components and the arrangement of the protein-coding sequence in its gene. We have now isolated and characterized bovine genomic DNA fragments encoding this precursor protein and have demonstrated that the protein sequence is encoded by two non-consecutive DNA segments. An intron (intervening sequence) of approximately 2.2 kilobase pairs separates the smaller exon (mRNA-coding sequence), which contains the gene sequence encoding the signal peptide, from the larger exon, which contains the gene sequence for most of the protein structure, including the known biologically active component peptides.     

Signalling by the sevenless protein tyrosine kinase is mimicked by Ras1 activation.

Cell-fate specification of R7 photoreceptors in the developing Drosophila eye depends on an inductive signal from neighbouring R8 cells. Mutations in three genes, sevenless (sev), bride-of-sevenless (boss) and seven-in-absentia (sina) cause the R7 precursor to become a non-neural cone cell. The sev gene encodes a receptor protein tyrosine kinase (Sev) localized on the R7 surface, activated by a boss-encoded ligand presented by R8. The sina gene encodes a nuclear factor required in R7. Reduction in the dosage of the Ras1 gene impairs Sev-mediated signalling, suggesting that activation of Ras1 may be an important consequence of Sev activation. We report here that Ras1 activation may account for all of the signalling action of Sev; an activated Ras1Va112 protein rescues the normal R7 precursor from transformation into a cone cell in sev and boss null mutants and induces the formation of supernumerary R7 cells. Similar activation of the Drosophila Ras2 protein does not produce these effects, demonstrating Ras protein specificity.     

一种适用于地震监测的地声传感探头

为了研究地声信号能否作为一种可靠的地震前兆信号,设计一种基于压电薄膜的地声传感探头,用于地震监测。该探头支持0.1 Hz～7 kHz宽频段地声信号采集,电压分辨率为19.073μV,幅值一致性误差小于5.5%(0.47 dB)。该探头通过盐雾试验、随机振动及包装跌落等6项可靠性测试,并应用到包括川滇国家试验场的178个台站的地声监测中。现场观测表明,震中周边的台站能够捕捉到地震前后的地声信号。     

cDNA sequence and chromosomal localization of human platelet-derived growth factor A-chain and its expression in tumour cell lines

The amino-acid sequence of the precursor of the human tumour cell line-derived platelet-derived growth factor (PDGF) A-chain has been deduced from complementary DNA clones and the gene localized to chromosome 7. The protein shows extensive homology to the PDGF B-chain precursor. Expression of the PDGF A-chain gene is independent of that of the PDGF B-chain in a number of human tumour cell lines, and secretion of a PDGF-like growth factor of relative molecular mass 31,000 correlates with expression of A- but not B-chain messenger RNA.     

纳米YAG粉体的制备与表征

以Y(NO3)3·6H2O、Al( NO3)3·9H2O、Nd(NO3)3·6H2O、NH4HCO3为原料,以乙醇为分散剂,采用共沉淀法制备Nd:YAG前躯体,将前躯体在不同温度下煅烧得到Nd:YAG粉体.分别采用红外光谱仪(FT-IR)、热重/差热分析仪(TG/DSC)、X射线衍射仪(XRD)、透射电子显微镜(TEM...     

Identification of two related pentapeptides from the brain with potent opiate agonist activity.

Enkephalin, a natural ligand for opiate receptors is composed of the pentapepides H-Tyr-Gly-Gly-Phe-Met-OH and H-Tyr-Gly-Gly-Phe-Leu-OH. The evidence is based on the determination of the amino acid sequence of natural enkephalin by the dansyl-Edman procedure and by mass spectrometry followed by synthesis and comparison of the natural and synthetic peptides.     

棒束花状α-Fe_2O_3的制备及其气敏特性

以FeCl_3·6H_2O为前驱体,聚乙烯基吡咯烷酮(PVP,分子量为8 000)为表面活性剂,先通过水热反应,再经高温煅烧制备具有棒束花状多级结构的α-Fe_2O_3,并用场发射扫描电子显微镜(FESEM)和透射电子显微镜(TEM)表征样品结构.结果表明:样品结构由棒束以自组装的方式形成,每个棒束由多个单晶纳米棒构成;由该结构制成的传感器件在200℃对丙酮具有良好的选择性及较高的灵敏度.     

Spleen colony-forming cell as common precursor for tissue mast cells and granulocytes

The haematopoietic stem cells which produce colonies in the spleen of irradiated mice (CFU-S) can differentiate into erythrocytes, granulocytes, megakaryocytes and B lymphocytes. Although mast cell precursors are known to be present in the bone marrow, spleen, fetal liver and peripheral blood of mice, the relationship between the mast cell precursor and CFU-S has remained unclear. We have now made use of mice of two mutant genotypes to determine whether or not the tissue mast cell is a progeny of CFU-S. Giant granules of beige (C57BL/6-bg/bg, Chediak-Higashi syndrome) mice can be used for identification of the origin of both tissue mast cells and granulocytes, and WBB6F1-W/Wv mice are useful recipients because they lack tissue mast cells owing to a defect in mast cell precursors. We injected the cells from a single spleen colony into each WBB6F1-W/Wv mouse and demonstrated directly that the tissue mast cell is a progeny of CFU-S.