Dual role of cAMP duringDictyostelium development

cAMP plays an essential role duringDictyostelium development both outside and inside the cell. Membrane-bound receptors and adenylyl cyclase are responsible for sensing and producing extracellular cAMP, whereas a phosphodiesterase is responsible for maintaining a low basal level. The molecular events underlying this type of hormone like signalling, which are now beginning to be deciphered, will be presented, in the light of cAMP analogue studies. The importance of intracellular cAMP for cell differentiation has been demonstrated by the central role of the cAMP dependent protein kinase. Mutants as well as strains obtained by reverse genetics will be reviewed which lead to our current understanding of the role of intracellular cAMP in the differentiation of both stalk and spore cells.     

Response ofPhloeotribus scarabaeoides (Coleoptera,Scolytidae) to ethylene in an olfactometer

The role of ethylene, pure or in formulation, in the colonization behaviour of the olive bark beetle,Phloeotribus scarabaeoides (Coleoptera, Scolytidae) has been investigated in the laboratory. Ethylene has been found to be attractive in both sexes; the formulation ethrel 48 was active in an olfactometer up to several months. Ethylene, whose concentration varies with the developmental stage or the condition of the tree or its wood, may play an important role in the primary attraction of these scolytids to their host.     

The influence of prostacyclin (PGI2) on contractile properties of isolated right ventricle of rat heart

The mechanism of the positive inotropic effect of prostacyclin (PGI₂) (2.6×10^?6 mol/l) on the isolated right ventricle of rat heart was studied. Our results show that the positive inotropic effect of prostacyclin is produced indirectly through beta adrenoceptors and slow Ca²⁺ channels, because blockade of slow Ca²⁺ channels with verapamil (10^?6 mol/l) and beta adrenoceptors with propranolol (10^?6 mol/l) abolishes this effect. Alpha adrenoceptors do not mediate the action of PGI₂.     

A state space approach to forecasting the final vintage of revised data with an application to the index of industrial production

There is considerable interest in the index of industrial production (IIP) as an indicator of the state of the UK's industrial base and, more generally, as a leading economic indicator. However, this index, in common with a number of key macroeconomic time series, is subject to revision as more information becomes available. This raises the problem of forecasting the final vintage of data on IIP. We construct a state space model to solve this problem which incorporates bias adjustments, a model of the measurement error process, and a dynamic model for the final vintage of IIP. Application of the Kalman filter produces an optimal forecast of the final vintage of data.     

贵州植物园珍稀濒危蕨类植物

本文介绍引种自贵州各地及我国华中、华东和华东的贵州植物园内的珍稀濒危蕨类植物。除列表表示来源、现状等情况外，还对桫椤Ａｌｓｐｈｉｌａ ｓｐｉｎｕｌｏｓａ （Ｈｏｏｋ）Ｔｒｙｏｎ，扇蕨Ｎｅｏｃｈｅｉｒｏｐｔｅｒｉｓ ｐｌａｍａｔｏｐｅｄａｔａ （Ｂａｋ．）Ｃｈｓｉｓｔ，宽叶水韭Ｉｓｏｅｔｅｓ ｊａｐｏｎｉｃａ Ａ．Ｂｒ．，中华水韭Ｉ．ｓｉｎｅｎｓｉｓ Ｐａｌｍｅｒ和截基盾蕨Ｎｅｏｌｅｐｉｓｏｒｕｓ     

灰色理论在化学研究中用作建模与预测新的方法

研究了灰色理论作为一种有用的化学计量学多元建模与定量预测新方法的可行性，将其应用于某些不确定关系如电泳迁移率，色谱保留值和农药需求量等建模，定量预测结果良好。     

铬酸钒为基的PTC陶瓷的研究

本文使用ＳＥＭ、ＥＤＳ、ＥＡＳ、ＸＲＤ和电阻率测量技术，研究了工艺参数和加入（Ｃｏ，Ｆｅ２Ｏ３）对ＰＴＣ（Ｖ１－ｘ，Ｃｒｘ）２Ｏ３陶瓷的显微结构和电性能的影响。实验结果表明，为了制造优良性能、高可靠的热敏电阻器，必须精确控制陶瓷组份和工艺。引人象Ｃ。这样的添加物是重要的，它主要以金属形式分布在基体中，同时发现添加物对试样致密度和电性能的影响也是有益的。     

T gamma protein is expressed on murine fetal thymocytes as a disulphide-linked heterodimer

During the search for genes coding for the mouse alpha and beta subunits of the antigen-specific receptor of mouse T cells we encountered a third gene, subsequently designated gamma. This gene has many properties in common with the alpha and beta genes, somatic assembly from gene segments that resemble the gene segments for immunoglobulin variable (V), joining (J) and constant (C) regions; rearrangement and expression in T cells and not in B cells; low but distinct sequence homology to immunoglobulin V, J and C regions; other sequences that are reminiscent of the transmembrane and intracytoplasmic regions of integral membrane proteins; and a cysteine residue at the position expected for a disulphide bond linking two subunits of a dimeric membrane protein. Despite these similarities the gamma gene also shows some interesting unique features. These include a relatively limited repertoire of the germ-line gene segments, more pronounced expression at the RNA level in immature T cells such as fetal thymocytes and an apparent absence of in-frame RNA in some functional, alpha beta heterodimer-bearing T cells or cultured T clones and hybridomas. To understand the function of the putative gamma protein it is essential to define the cell population that expresses this protein. To this end we produced a fusion protein composed of Escherichia coli beta-galactosidase and the gamma-chain (hereafter referred to a beta-gal-gamma) using the phage expression vector lambda gt11 and raised rabbit antisera against the gamma determinants. Using the purified anti-gamma antibody we detected a polypeptide chain of relative molecular mass 35,000 (Mr 35K) on the surface of 16-day old fetal thymocytes. The gamma-chain is linked by a disulphide bridge to another component of 45K. No such heterodimer was detected on the surface of a cytotoxic T lymphocyte (CTL) clone 2C from which an in-phase gamma cDNA clone was originally isolated.     

Cloning of decay-accelerating factor suggests novel use of splicing to generate two proteins

Decay-accelerating factor (DAF), a glycoprotein that is anchored to the cell membrane by phosphatidylinositol, binds activated complement fragments C3b and C4b, thereby inhibiting amplification of the complement cascade on host cell membranes. Here, we report the molecular cloning of human DAF from HeLa cells. Analysis of DAF complementary DNAs revealed two classes of DAF messenger RNA, one apparently derived from the other by a splicing event that causes a coding frameshift near the C terminus. The apparent 'intron' sequence contains an Alu family member and encodes contiguous protein sequence. Two DAF proteins are therefore possible, having divergent C-terminal domains which differ in their hydrophobicity. Both mRNAs are found on polysomes, suggesting that both are translated. We propose that the major (90%) spliced DAF mRNA encodes membrane-bound DAF whereas the minor (10%) unspliced DAF mRNA may encode secreted DAF and we present expression data supporting this. The deduced DAF sequence contains four repeating units homologous to a consensus repeat found in a recently described family of complement proteins.     

cDNA cloning of bovine substance-K receptor through oocyte expression system

The neuropeptide receptors which are present in very small quantities in the cell and are embedded tightly in the plasma membrane have not been well characterized. Mammals contain three distinct tachykinin neuropeptides, substance P, substance K and neuromedin K, and it has been suggested that there are multiple tachykinin receptors. By electrophysiological measurement, we have previously shown that Xenopus oocytes injected with brain and stomach mRNAs faithfully express mammalian substance-P and substance-K receptors, respectively. Here we report the isolation of the cDNA clone for bovine substance-K receptor (SKR) by extending this method to develop a new cloning strategy. We constructed a stomach cDNA library with a cloning vector that allowed in vitro synthesis of mRNAs and then identified a particular cDNA clone by testing for receptor expression following injection of the mRNAs synthesized in vitro into the oocyte system. Because oocytes injected with exogenous mRNAs can express numerous receptors and channels, our new strategy will be applicable in the general molecular cloning of these proteins. The result provides the first indication that the neuropeptide receptor has sequence similarity with rhodopsin-type receptors (the G-protein-coupled receptor family) and thus possesses multiple membrane-spanning domains.