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241.
242.
A A Selyanko C E Stansfeld D A Brown 《Proceedings. Biological sciences / The Royal Society》1992,250(1328):119-125
The M-current (IK(M)) is a slow voltage-gated K+ current which can be inhibited by muscarinic acetylcholine-receptor (mAChR) agonists. In the present experiments we have tested whether this inhibition results from a local (membrane-delimited) interaction between the receptor and adjacent channels, or whether channel closure is mediated by a diffusible messenger. To do this, single KM(+)-channel currents were recorded from membrane patches in dissociated rat superior cervical sympathetic neurons by using cell-attached patch electrodes. Channel activity was inhibited when muscarine was applied to the cell membrane outside the patch but persisted when channels were exposed to muscarine added to the pipette solution. We conclude that a diffusible molecule (or molecules) is (are) required to induce intrapatch channel closure following activation of extra-patch receptors. 相似文献
243.
Jack T. Trevors 《Applied microbiology and biotechnology》1991,35(3):416-419
Summary Alginate-entrapped cells of Pseudomonas fluorescens were introduced into soil microcosms to evaluate their respiratory activity (O2 consumption and CO2 evolution) and survival during a 14-day incubation period at 20°C. Alginate-entrapped cells and cells resuspended in sterile distilled water and introduced into sterile soil exhibited relatively similar O2 consumption/CO2 evolution and survival over the 14-day period. The same treatments in non-sterile soil exhibited lower respiratory activity and a population density decrease of about 2.0 Log. cfu/g after 14 days. Alginate-entrapped bacterial cells may be a useful method for introducing genetically-engineered and non-engineered bacterial strains into the soil environment. 相似文献
244.
Introduction of exogenous DNA into Chlamydomonas reinhardtii by electroporation. 总被引:4,自引:0,他引:4 下载免费PDF全文
The fate of exogenous DNA introduced into Chlamydomonas reinhardtii by electroporation was analyzed. With single and double electrical pulses, plasmids as large as 14 kb were introduced into cells with and without intact cell walls. Within hours after introduction, exogenous plasmid DNA was associated with nuclei isolated from cells; several weeks after introduction, exogenous DNA was stably integrated into the Chlamydomonas genome. These studies establish electroporation as a method for introducing DNA, and potentially other molecules, into C. reinhardtii. 相似文献
245.
246.
G G Simpson P Vaux G Clark R Waugh J D Beggs J W Brown 《Nucleic acids research》1991,19(19):5213-5217
U1 and U2snRNPs play key roles in pre-mRNA splicing. The interactions between the U1 and U2snRNP-specific proteins, U1A, U2A' and U2B' and their respective UsnRNAs are of interest both to elucidate their roles in splicing, and as models to study RNA-protein interactions. We have cloned a full-length cDNA, encoding U2B', from potato. This is the first report of a sequence for a plant UsnRNP protein. The plant U2B' sequence exhibits extensive similarity with the human U2B' protein at both the DNA and amino acid levels. The evolutionary conservation at the protein level, particularly in sequences implicated in determining specific binding to U2snRNA, suggests conservation of U2B' function from plants to man. The significance of amino acid substitutions in the RNP-80 motif with respect to U2snRNA binding in plants is discussed. 相似文献
247.
The molecular mechanism of inhibition of alpha-type DNA polymerases by N2-(butylphenyl)dGTP and 2-(butylanilino)dATP: variation in susceptibility to polymerization. 总被引:2,自引:2,他引:0 下载免费PDF全文
Calf thymus DNA polymerase alpha (pol alpha) and bacteriophage T4 DNA polymerase (pol T4) were exploited as model enzymes to investigate the molecular mechanism of inhibitory action of N2-(p-n-butylphenyl)dGTP (BuPdGTP) and 2-(p-n-butyl-anilino)dATP (BuAdATP) on the BuPdNTP-susceptible alpha polymerase family. Kinetic analysis of inhibition of pol alpha with mixtures of complementary and noncomplementary template:primers indicated that both nucleotides induced the formation of a polymerase: inhibitor:primer-template complex. Primer extension experiments using the guanine form as the model analog indicated that pol alpha cannot utilize these nucleotides to extend primer termini. In contrast, pol T4 polymerized BuPdGTP, indicating that resistance to polymerization is not a common feature of the inhibitor mechanism among the broad membership of the alpha polymerase family. 相似文献
248.
Lisa G. Shaffer Colleen K. Jackson-Cook Joanne M. Meyer Judith A. Brown J. Edward Spence 《Human genetics》1991,86(4):375-382
Summary The largest class of de novo chromosomal rearrangements in Down syndrome are rea(21q21q). Classically, these rearrangements have been termed Robertsonian translocations, implying an attachment of two different chromosome 21 homologues. Additionally, a Robertsonian translocation between two chromosomes 21 cannot be distinguished from an isochromosome composed of genetically identical arms by cytogenetic analyses. Therefore, we have used molecular techniques to differentiate between true Robertsonian translocations and isochromosomes. Samples were obtained from 12 probands, ascertained for de novo rearrangements between homologous chromosomes 21 [11 rea(21q21q) and 1 rea (21;21)(q22;q22)], their parents (n = 24) and available siblings (n = 7). The parental origins of the de novo rearrangements were assigned using molecular and cytogenetic analyses. Although not statistically significant, there was a two-fold increase in the number of paternally derived de novo rearrangements (n = 8) as compared with maternally derived rearrangements (n = 4). To distinguish between rob(21q21q) and i(21q), we used restriction fragment length polymorphisms (RFLPs) spanning the length of chromosome 21. Using all informative and partially informative RFLPs, we used the method of maximum likelihood to assign the most likely rearrangement definition (i or rob) and parental origin in each family. The maximum likelihood estimates indicated that all rearrangements tested (n = 8) were isochromosomes. C-banding revealed two centromeres in three cases indicating that a U-type exchange occurred between sister chromatids in these rearrangements. Our results suggest that the majority of de novo rea(21q21q) are isochromosomes derived from a single parental chromosome 21. 相似文献
249.
Microtubule arrays associated with simultaneous cytokinesis in the coenocytic microsporocytes of Lonicera japonica and Impatiens sultani were studied by indirect immunofluorescence. The future division planes are not predicted prior to meiosis by either a preprophase band of microtubules or cytoplasmic lobing. Cleavage planes appear to be determined by position of the four haploid nuclei and the development of postmeiotic microtubule systems. Perpendicular second division spindles in Lonicera result in tetrahedrally arranged tetrads while parallel spindles in Impatiens result in tetragonal arrangement. Immediately following meiosis bands of microtubules, the secondary spindles, develop between both sister and nonsister nuclei. These arrays give way to systems of microtubules that radiate equally from each of the four nuclei in the coenocytic sporocyte. Simultaneous cytokinesis is initiated by centripetal wall deposition at the periphery of the sporocyte and proceeds along planes marked by interaction of the opposing arrays of nuclear-based microtubules. 相似文献
250.
G Burns T Brown K Hatter J M Idriss J R Sokatch 《European journal of biochemistry》1988,176(2):311-317
The genes encoding proteins responsible for activity of the E1 component of branched-chain-oxoacid dehydrogenase of Pseudomonas putida have been subcloned and the nucleotide sequence of this region determined. Open reading frames encoding E1 alpha (bkdA1, 1233 bp) and E1 beta (bkdA2, 1020 bp) were identified with the aid of the N-terminal sequence of the purified subunits. The Mr of E1 alpha was 45,158 and of E1 beta was 37,007, both calculated without N-terminal methionine. The deduced amino acid sequences of E1 alpha and E1 beta had no similarity to the published sequences of the E1 subunits of pyruvate and 2-oxoglutarate dehydrogenases of Escherichia coli. However, there was substantial similarity between the E1 alpha subunits of Pseudomonas and rat liver branched-chain-oxoacid dehydrogenases. In particular, the region of the E1 alpha subunit of the mammalian branched-chain-oxoacid dehydrogenase which is phosphorylated, was found to be highly conserved in the Pseudomonas E1 alpha subunit. There was also considerable similarity between the E1 beta subunits of Pseudomonas branched-chain-oxoacid dehydrogenase and human pyruvate dehydrogenase. 相似文献