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排序方式: 共有101条查询结果,搜索用时 15 毫秒
1.
The detection of apple chlorotic leafspot virus by a modified procedure of enzyme-linked immunosorbent assay (ELISA) 总被引:1,自引:0,他引:1
The technique of enzyme-linked immunosorbent assay (ELISA) was modified to enable detection of apple chlorotic leafspot virus (CLSV) both in herbaceous hosts and in several naturally infected fruiting and ornamental woody host species. Some of the characteristics of the modified method as used with different virus-host combinations are described. 相似文献
2.
Transient Cytoplasmic pH Changes in Correlation with Opening of Potassium Channels in Eremosphaera 总被引:1,自引:0,他引:1
Steigner, W. Khler, K., Simonis, W. and Urbach, W. 1988. Transientcytoplasmic pH changes in correlation with opening of potassiumchannels in Eremosphaera.J. exp. Bot. 39: 2336. The role of the cytoplasmic pH (pHc) of Eremosphaera viridisin the signal transduction chain after light-off from the chloroplaststo the K+ channels in the plasmalemma of this unicellular algawas investigated. The temporary opening of K+ channels is indicatedby a transient hypcrpolarization (TP). To record rapid changesof pHc, continuous measurements with pH sensitive micro-electrodeswere carried out. (i) Under normal conditions pHc in the light(7·56 ±0·2) did not differ from pHc inthe dark (7·62 ±0·2). (ii) The vacuolepH ranged between 4·8 and 5·2. (iii) After light-offa rapid transient acidification of pHc O19±0·07occurred and a TP was released, (iv) In every case, the startof the transient acidification after light-off preceded thehyperpolarization by about 3s. (v) Light-on caused a rapid transientalkalinization but never a TP. (vi) Change to acid externalmedium (3.2) transiently acidified the cytoplasm and was ableto release a TP. (vii) After addition of NH4Cl, pHc again showeda rapid transient acidification and the release of a TP. The origin of the protons appearing in the cytoplasm after light-offis discussed critically with respect to the buffer capacity.Either direct or indirect translocation is a possible mechanismfor the movement of H+ from the chloroplasts into the cytoplasm.The intracellular acidification and its relation to the openingof potassium channels in the plasmalemma leads us to suggestthat a sudden change of pHc is a potent internal signal factorin Eremosphaera viridis. Key words: Cytoplasmic pH, transient potential, K+channels, Eremosphaera viridis 相似文献
3.
THALER M.; STEIGNER W.; F?RSTER B.; K?HLER K.; SIMONIS W.; URBACH W. 《Journal of experimental botany》1989,40(11):1195-1203
The role of cytoplasmic calcium activity in activation of K+-channelsin the unicellular green alga Eremosphaera viridis has beenstudied. As reported previously, after a light offsignal a voltage independent opening of K+-channels in the plasmalemmais observed. This effect is indicated by a transient polarization(TP) with a simultaneous increase of the membrane conductance.TPs can also be triggered by different treatments, which allowinvestigations within a short-circuited signalchain. (i) After incubation with EGTA a single extended TP canbe released by a sudden increase of the external calcium concentration.The Ca2+-channel inhibitors nifedipine (10 2 mol m3)and verapamil (5 ? 102 mol m3) suppress the releaseof this TP. (ii) In the presence of external calcium the additionof the ionophore A23187
[GenBank] (103 mol m3) causes anextremely prolonged TP. (iii) Low external concentrations ofbarium (102 mol m3) induce repetitive TPs in thepresence of external calcium. In this case the Ca2+-channelinhibitors are less effective. (iv) Strontium (0.11.0mol m3) is able to trigger repetitive TPs even withoutexternal calcium. Whereas barium may stimulate a calcium influx,strontium can serve as a substitute for calcium to induce anopening of K+-channels. These results indicate strongly a Ca2+-dependentand voltage-independent activation of K+-channels in the plasmalemmaof Eremosphaera. The participation of cytoplasmic calcium inthe signal transduction chain after a light offsignal is discussed. Key words: Ca2+-dependent K+-channels, Ca2+-channel effectors, A23187, transient membrane potential, Eremosphaera 相似文献
4.
SALLY LYMAN ALLEN JULIAN ADAMS CAROLINE L. RUSHFORD 《The Journal of eukaryotic microbiology》1983,30(1):143-147
ABSTRACT. Up to five zones of acid phosphatase activity appear in gels after electrophoresis of detergent-treated extracts from 13 of the 14 species of the Paramecium aurelia complex. The overall pattern is somewhat similar for all species: differences in intensity and mobility of individual zones permit the grouping of these sibling species into eight groups. All 14 species can be identified using the procedure of enzyme electrophoresis, although two of them are more similar than is usually the case. Problems of misclassification are discussed in terms of the nature and frequency of variants. With the judicious choice of enzymes used to screen new stocks, these problems can be circumvented. Species relationships are updated using 11 enzymes. A dendrogram constructed from the matrix of genetic distances shows four clusters of species: (i) P. biaurelia, P. triaurelia; (ii) P. primaurelia, P. pentaurelia, P. sexaurelia, P. novaurelia; (iii) P. septaurelia, P. undecaurelia, P. tredecaurelia, P. quadecaurelia; and (iv) P. tetraurelia, P. octaurelia, P. decaurelia, P. dodecaurelia. Distances between the species are large, on the order of the differences between Drosophila species. The species are characterized by an extraordinary lack of geographical differentiation and great morphological similarity, which contrasts strongly with the molecular differentiation. 相似文献
5.
- 1 Six 800-sweep samples of English and Michigan (“old field”) secondary vegetation arthropods are compared with Costa Rican samples taken in the same way.
- 2 Parasitic Hymenoptera and spiders accounted for a larger proportion of the arthropod fauna in the mid-latitude than the tropical samples.
- 3 In one English field, the seasonal change in insect numbers was 88% of that recorded over all the seasonal and elevational changes examined in Costa Rica. Furthermore, the difference in the total dry weights of the arthropod fauna between December and July was similar to the difference found between the wet and dry seasons in tropical secondary vegetation (also similar to the difference between day and night values during the dry season).
- 4 Aphids and Psyllidae were far more abundant in the English site than in the Costa Rican mainland sites.
- 5 In mid-summer, the English field had far more arthropods in it than did any of the tropical sites sampled.
6.
MARTIN CLÉMENT CAROLINE CHAMBERLAND JACQUELINE PÉRODIN RICHARD LEDUC GAÉTAN GUILLEMETTE EMANUEL ESCHER 《Journal of receptor and signal transduction research》2013,33(5-6):417-433
Several models of activation mechanisms were proposed for G protein-coupled receptors (GPCRs), yet no direct methods exist for their elucidation. The availability of constitutively active mutants has given an opportunity to study active receptor conformations within acceptable limits using models such as the angiotensin II type 1 (AT1)1 receptor mutant N111G-hAT1 which displays an important constitutive activity. Recently, by using methionine proximity assay, we showed for the hAT1 receptor that TMD III, VI, and VII form the ligand-binding pocket of the C-terminal amino acid of an antagonistic AngII analogue. In the present contribution, we investigated whether the same residues would also constitute the ligand-binding contacts in constitutively activated mutant (CAM) receptors. For this purpose, the same Met mutagenesis strategy was carried out on the N111G double mutants. Analysis of 43 receptors mutants in the N111G-hAT1 series, photolabeled and CNBr digested, showed that there were only subtle structural changes between the wt-receptor and its constitutively active form. 相似文献
7.
PHILLIP A. WACKYM CAROLINE T. CHEN AKIRA ISHIYAMA ROBERT M. PETTIS IVN A. L
PEZ LARRY HOFFMAN 《Cell biology international》1996,20(3):187-192
The expression of the five muscarinic acetylcholine receptor (mAChR) subtypes (m1–m5) in the vestibular end-organs and in the primary afferent vestibular ganglia of the human and rat was studied using RT-PCR from the two tissue populations from both species. In the human, although all five mAChR subtypes were expressed in brain, only the m1, m2, and m5 mAChR subtypes were amplified from both the vestibular ganglia and the vestibular end-organs, while in the rat, all five mAChR subtypes were expressed. These data suggest that the efferent cholinergic axo-dendritic and axo-somatic synapses have a muscarinic component and that there are pharmacologic implications for patients with vestibular dysfunction. 相似文献
8.
Abstract: A bryozoan fauna from carbonate mud-mounds is described from subsurface well cores from the Upper Ordovician (Lower Ashgill) Jifarah (Djeffara) Formation of Tripolitania, north-west Libya. Among a diverse assemblage dominated by trepostomes, nine species of bryozoans are identified, including Jifarahpora libyensis gen. et sp. nov. Delicate and robust branching, encrusting and nodular bryozoan growth forms are all common. The bryozoan-rich limestones are mostly mudstones and wackestones, with bafflestone and floatstone textures, but the mounds apparently lack organic framework and microbial fabrics. Regional geophysical data indicate rapid thickness changes between wells, where mound complexes locally up to 100 m thick had limited topographic relief over the surrounding sea floor. The mounds formed in a high-latitude, cool-water carbonate belt that extended widely across the northern margin of Gondwana. Quaternary analogues from the Great Australian Bight suggest that these early Ashgill mounds may have developed in slope environments during an episode of glacial lowstand that preceded the late Ashgill, Hirnantian glacial event. 相似文献
9.
CAROLINE MÜLLER ALISON BARKER JEAN-LUC BOEVÉ PETER W. DE JONG HELENE DE VOS PAUL M. BRAKEFIELD 《Biological journal of the Linnean Society. Linnean Society of London》2004,83(2):219-227
This study compares the population genetic structure of two obligate parthenogenetic sawfly species, Aneugmenus padi (L.) Zhelochovtsev and Eurhadinoceraea ventralis (Panzer) Enslin (Hymenoptera: Tenthredinidae). Allozymes were used to detect genetic differences in larvae collected at different sites in six European countries. For A. padi , scoring six polymorphic enzymes revealed the existence of five dominant, widely distributed clones and several more with only very few individuals occurring locally. The clonal diversity and identity differed across collection sites, with up to at maximum eight clones coexisting at a single locality. In contrast, in E. ventralis , individuals from different localities were all monomorphic for at least six different enzymes and are therefore assumed to belong to the same clone. Differences in population genetic structure of these sawfly species can be related to the differing distributions of their host plants: the fern, Pteridium aquilinum , the host of A. padi , has been an invasive species for more than two hundred years. Spread of clones of A. padi is likely to have closely followed the complex invasive pattern of spread of the plant. Larvae of E. ventralis were collected from local, horticultural plantings of Clematis spp. of recent origin probably with gardeners having traded plants infested with the sawfly. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 219–227. 相似文献
10.
HOLGER PENNING CAROLINE M. PLUGGE† PIERRE E. GALAND‡ RALF CONRAD 《Global Change Biology》2005,11(12):2103-2113
Methane is a major product of anaerobic degradation of organic matter and an important greenhouse gas. Its stable carbon isotope composition can be used to reveal active methanogenic pathways, if associated isotope fractionation factors are known. To clarify the causes that lead to the wide variation of fractionation factors of methanogenesis from H2 plus CO2 (), pure cultures and various cocultures were grown under different thermodynamic conditions. In syntrophic and obligate syntrophic cocultures thriving on different carbohydrate substrates, fermentative bacteria were coupled to three different species of hydrogenotrophic methanogens of the families Methanobacteriaceae and Methanomicrobiaceae. We found that C‐isotope fractionation was correlated to the Gibbs free energy change (ΔG) of CH4 formation from H2 plus CO2 and that the relation can be described by a semi‐Gauss curve. The derived relationship was used to quantify the average ΔG that is available to hydrogenotrophic methanogenic archaea in their habitat, thus avoiding the problems encountered with measurement of low H2 concentrations on a microscale. Boreal peat, rice field soil, and rumen fluid, which represent major sources of atmospheric CH4, exhibited increasingly smaller , indicating that thermodynamic conditions for hydrogenotrophic methanogens became increasingly more favourable. Vice versa, we hypothesize that environments with similar energetic conditions will also exhibit similar isotope fractionation. Our results, thus, provide a mechanistic constraint for modelling the 13C flux from microbial sources of atmospheric CH4. 相似文献