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101.
Manju Bhandari Kathryn D. Campbell Matthew D. Collins Alison K. East 《Current microbiology》1997,35(4):207-214
The cluster of genes encoding components of the progenitor botulinum neurotoxin complex has been mapped and cloned in Clostridium botulinum type G strain ATCC 27322. Determination of the nucleotide sequence of the region has revealed open reading frames encoding
nontoxic components of the complex, upstream of the gene encoding BoNT/G (botG). The arrangement of these genes differs from that in strains of other antigenic toxin types. Immediately upstream of botG lies a gene encoding a protein of 1198 amino acids, which shows homology with the nontoxic-nonhemagglutinin (NTNH) component
of the progenitor complex. Further upstream there are genes encoding proteins with homology to hemagglutinin components (HA-17,
HA-70) and a putative positive regulator of gene expression (P-21). Sequence comparison has shown that BoNT/G has highest
homology with BoNT/B. The sequence of the BoNT-cluster of genes in non-proteolytic C. botulinum type B strain Eklund 17B has been extended to include the complete NTNH and HA-17, and partial HA-70 gene sequences. Comparison
of NTNH/G with other NTNHs reveals that it shows highest homology with NTNH/B consistent with the genealogical affinity shown
between BoNT/G and BoNT/B genes.
Received: 28 January 1997 / Accepted: 24 March 1997 相似文献
102.
Musa A Haxhiu Prabha Kc Constance T Moore Sandra S Acquah Christopher G Wilson Syed I Zaidi V John Massari Donald G Ferguson 《Journal of applied physiology》2005,98(6):1961-1982
This review summarizes recent work on two basic processes of central nervous system (CNS) control of cholinergic outflow to the airways: 1) transmission of bronchoconstrictive signals from the airways to the airway-related vagal preganglionic neurons (AVPNs) and 2) regulation of AVPN responses to excitatory inputs by central GABAergic inhibitory pathways. In addition, the autocrine-paracrine modulation of AVPNs is briefly discussed. CNS influences on the tracheobronchopulmonary system are transmitted via AVPNs, whose discharge depends on the balance between excitatory and inhibitory impulses that they receive. Alterations in this equilibrium may lead to dramatic functional changes. Recent findings indicate that excitatory signals arising from bronchopulmonary afferents and/or the peripheral chemosensory system activate second-order neurons within the nucleus of the solitary tract (NTS), via a glutamate-AMPA signaling pathway. These neurons, using the same neurotransmitter-receptor unit, transmit information to the AVPNs, which in turn convey the central command to airway effector organs: smooth muscle, submucosal secretory glands, and the vasculature, through intramural ganglionic neurons. The strength and duration of reflex-induced bronchoconstriction is modulated by GABAergic-inhibitory inputs and autocrine-paracrine controlling mechanisms. Downregulation of GABAergic inhibitory influences may result in a shift from inhibitory to excitatory drive that may lead to increased excitability of AVPNs, heightened airway responsiveness, and sustained narrowing of the airways. Hence a better understanding of these normal and altered central neural circuits and mechanisms could potentially improve the design of therapeutic interventions and the treatment of airway obstructive diseases. 相似文献
103.
Salinity is the major environmental constraint that affects legume productivity by inducing oxidative stress. Individually, both silicon (Si) nutrition and mycorrhization have been reported to alleviate salt stress. However, the mechanisms adopted by both in mediating stress responses are poorly understood. Thus, pot trials were undertaken to evaluate comparative as well as interactive effects of Si and/or arbuscular mycorrhiza (AM) in alleviating NaCl toxicity in modulating oxidative stress and antioxidant defence mechanisms in two Cicer arietinum L. (chickpea) genotypes—HC 3 (salt-tolerant) and CSG 9505 (salt-sensitive). Plants subjected to different NaCl concentrations (0–100 mM) recorded a substantial increase in the rate of superoxide radical (O2 ·?), H2O2, lipoxygenase (LOX) activity and malondialdehyde (MDA) content, which induced leakage of ions and disturbed Ca2+/Na+ ratio in roots and leaves. Individually, Si and AM reduced oxidative burst by strengthening antioxidant enzymatic activities (superoxide dismutase (SOD), catalase (CAT) and guaiacol peroxidase (GPOX)). Si was relatively more efficient in reducing accumulation of stress metabolites, while mycorrhization significantly up-regulated antioxidant machinery and modulated ascorbate-glutathione (ASA-GSH) cycle. Combined applications of Si and AM complemented each other in reducing reactive oxygen species (ROS) build-up by further enhancing the antioxidant defence responses. Magnitude of ROS-mediated oxidative burden was lower in HC 3 which correlated strongly with more effective AM symbiosis, better capacity to accumulate Si and stronger defence response when compared with CSG 9505. Study indicated that Si and/or AM fungal amendments upgraded salt tolerance through a dynamic shift from oxidative destruction towards favourable antioxidant defence system in stressed chickpea plants. 相似文献
104.
miRISC and the CCR4–NOT complex silence mRNA targets independently of 43S ribosomal scanning
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Duygu Kuzuoğlu‐Öztürk Dipankar Bhandari Eric Huntzinger Maria Fauser Sigrun Helms Elisa Izaurralde 《The EMBO journal》2016,35(11):1186-1203
miRNAs associate with Argonaute (AGO) proteins to silence the expression of mRNA targets by inhibiting translation and promoting deadenylation, decapping, and mRNA degradation. A current model for silencing suggests that AGOs mediate these effects through the sequential recruitment of GW182 proteins, the CCR4–NOT deadenylase complex and the translational repressor and decapping activator DDX6. An alternative model posits that AGOs repress translation by interfering with eIF4A function during 43S ribosomal scanning and that this mechanism is independent of GW182 and the CCR4–NOT complex in Drosophila melanogaster. Here, we show that miRNAs, AGOs, GW182, the CCR4–NOT complex, and DDX6/Me31B repress and degrade polyadenylated mRNA targets that are translated via scanning‐independent mechanisms in both human and Dm cells. This and additional observations indicate a common mechanism used by these proteins and miRNAs to mediate silencing. This mechanism does not require eIF4A function during ribosomal scanning. 相似文献
105.
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107.
Extracts ofAscophyllum nodosum, Fucus serratus, F. vesiculosus andPelvetia canaliculata contain inhibitors of α-amylase, lipase and trypsin. The inhibitors were isolated and identified by1H NMR spectroscopy as polyphenols which have apparent molecular weights in the range from 30 000 to 100 000 daltons, as determined
by ultra-filtration with Amicon membranes. These polyphenols account for the whole of the inhibitory activity in crude algal
extracts. The compounds inhibit α-amylase and trypsin in an apparently non-competitive manner, when preincubated with the
enzymes, and the inhibition is directly proportional to the concentration of the inhibitor. Starch protects α-amylase when
added to the enzyme together with the inhibitors. Under this condition the effectiveness of the inhibitors is reduced ten-fold. 相似文献
108.
Summary The present investigation deals with some of the organizational and histochemical aspects of the embryo sac ofScilla sibirica. Both the synergids and egg cell are invested by PAS-positive complete walls. The filiform apparatus comprises an elaborate system of fibrillar projections, showing extensive ramifications. The micropylar region of the embryo sac wall from where the filiform apparatus originates is composed of three distinct layers. On a histochemical basis it may be surmised that, unlike the egg cell, the synergids are metabolically very active. Two kinds of wall ingrowths (i) massive and highly branched very much akin to the filiform apparatus, and (ii) small tuberculate wall projections, are unique to the antipodal cells of S.sibirica. Small tuberculate projections have also been observed along the wall of the central cell adjacent to the nutrient-rich nucellar cells. The antipodals and the central cell show the presence of starch grains and abundant total proteins. All the cell types in the embryo sac ofS. sibirica are structurally so organized as to meet the requirements of its nutrition during pre- and postfertilization development. The presence of abundant PAS-positive granular substance in the cells of nucellar epidermis probably establishes a gradient which assists in the pollen tube growth. 相似文献
109.
110.
The light activated proton pump, bacteriorhodopsin was modified with varying amounts of flourescamine, the fluorescamine to
protein ratio ranging from 1 to 100. The modified protein was washed free of excess of fluorescamine and reconstituted into
phospholipid vesicles to check the proton pumping activity. Although the spectral investigations indicated chemical modification,
the circular dichroism measurements pointed to an overall loss of the trimeric structure of the protein. The implications
of the present study are that the modifying agent can interact non-specifically with the protein, altering its structural
parameters, which in turn affects the function of the protein 相似文献