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1.
Jonathan Porter Joan Robinson Roger Pickup Clive Edwards 《FEMS microbiology letters》1995,133(1-2):195-199
Abstract The effectiveness of immunofluorescence flow cytometry and cell sorting to detect, quantify and separate indigenous bacterial populations present in low concentrations in sewage outflow was investigated. Preparatory experiments for targeted recovery revealed indigenous, immunoglobulin-G-binding particles present at low levels in sewage outflow samples taken from Coniston Water. Fluorescence-activated cell sorting of this population was employed to enrich for these particles, which were confirmed as bacterial cells. This cell population comprised approximately 23% of the total plate count on MacConkey agar before cell sorting, rising to approximately 95% after sorting. These results corresponded to cell densities of less than 5% of the total plate count on R2A agar. Taxonomic tests suggested the bacterium to be Ochrobactrum anthropi . 相似文献
2.
George V. Sharonov Eduard V. Bocharov Peter M. Kolosov Maria V. Astapova Alexander S. Arseniev Alexey V. Feofanov 《The Journal of biological chemistry》2014,289(21):14955-14964
The EphA2 receptor tyrosine kinase plays a central role in the regulation of cell adhesion and guidance in many human tissues. The activation of EphA2 occurs after proper dimerization/oligomerization in the plasma membrane, which occurs with the participation of extracellular and cytoplasmic domains. Our study revealed that the isolated transmembrane domain (TMD) of EphA2 embedded into the lipid bicelle dimerized via the heptad repeat motif L535X3G539X2A542X3V546X2L549 rather than through the alternative glycine zipper motif A536X3G540X3G544 (typical for TMD dimerization in many proteins). To evaluate the significance of TMD interactions for full-length EphA2, we substituted key residues in the heptad repeat motif (HR variant: G539I, A542I, G553I) or in the glycine zipper motif (GZ variant: G540I, G544I) and expressed YFP-tagged EphA2 (WT, HR, and GZ variants) in HEK293T cells. Confocal microscopy revealed a similar distribution of all EphA2-YFP variants in cells. The expression of EphA2-YFP variants and their kinase activity (phosphorylation of Tyr588 and/or Tyr594) and ephrin-A3 binding were analyzed with flow cytometry on a single cell basis. Activation of any EphA2 variant is found to occur even without ephrin stimulation when the EphA2 content in cells is sufficiently high. Ephrin-A3 binding is not affected in mutant variants. Mutations in the TMD have a significant effect on EphA2 activity. Both ligand-dependent and ligand-independent activities are enhanced for the HR variant and reduced for the GZ variant compared with the WT. These findings allow us to suggest TMD dimerization switching between the heptad repeat and glycine zipper motifs, corresponding to inactive and active receptor states, respectively, as a mechanism underlying EphA2 signal transduction. 相似文献
3.
C C Tsai C C Tsai J M Sligh M Yarnall K E Follis S T Roodman 《Journal of medical primatology》1989,18(3-4):175-183
Monoclonal antibodies (MoAbs) to the major gag core protein p27 and a viral protein p44 of type D retrovirus (SRV-2) were produced and used in the detection of SRV-2 antigens in infected Raji cells and in tissues from macaques with simian acquired immunodeficiency syndrome (SAIDS) and retroperitoneal fibromatosis (RF). Anti-p44 MoAb showed inhibition of syncytium formation by both SRV-1- and SRV-2-infected Raji cells. 相似文献
4.
Magali Ferrero Frdrique Spyratos Andre Desplaces Catherine Andrieu Edelmira Phillips Jacques Rouëss 《Biology of the cell / under the auspices of the European Cell Biology Organization》1989,65(3):305-308
Using four human tumor cell lines, MCF-7 and T47-D from breast tumors, MOLT-4 and K-562 from leukemia, flow cytometric DNA analysis of pure and mixed cell population was performed using monoclonal antibodies to cytokeratin to distinguish cytokeratin-containing carcinoma cells from leukemia cells which do not contain cytokeratins. Surprisingly, on pure or mixed K-562 cells, we found positive labeling with KL1, CK8, and CK18 antibodies (results confirmed by immunocytology). This preliminary study has allowed a DNA analysis on epithelial cells of human breast tumors. 相似文献
5.
Flow cytometry (FCM) in conjunction with immunocytochemical-labeling was used to analyze and screen a population of Escherichia coli clones containing a genomic library from the oil-degrading microorganism Acinetobacter calcoaceticus RAG-1 for the isolation of clones which expressed specific RAG-1 surface antigens. Reconstruction experiments using mixed populations indicated that RAG-1 cells could be clearly distinguished at a ratio of one RAG-1 cell to 500 Escherichia coli cells. Using this technique two clones, WM143 and WM191, were isolated and shown by restriction endonuclease cleavage and Southern hybridization to contain plasmids carrying inserts of RAG-1 DNA of 9.4 and 9.8 kb respectively.Non-common abbreviations FCM
flow cytometry
- FITC
fluorescein-iso-thiocyanate
- LB
Luria broth
- MM
minimal salt medium
- PBS
phosphate buffered saline
- PMSF
phenylmethylsulfonyl fluoride 相似文献
6.
W. Junger H. J. Dahmen 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,169(5):641-646
Waterstriders (Gerris paludum) often try to maintain a nearly stationary position on a moving water surface. Passive motion is restricted to 3 degrees of freedom: yaw, longitudinal, and transverse displacement. They correct for passive rotation and translation by distinct behavioral sequences. The compensatory behavior is predominantly visually controlled.
The restriction of degreess of freedom reduces the complexity of the motion-induced visual flow field. Each motion component induces its own flow field component. We propose that those areas of the visual field are preferred for analysis where the directions of the 3 flow field components differ most. These areas (Figs. 2 and 3) have their largest extent at 45° above the horizon. 相似文献
1. | When waterstriders are rotated and translated simultaneously, they are able to discriminate their own rotation and translation visually. |
2. | They discriminate their rotation from their translation even if the visible pattern is restricted to a monocular visual field. |
3. | They detect rotation only if they see an extended pattern. |
7.
本文用流式细胞光度术(FCM)等方法研究了MNNG,ENNG和DMS对HeLa细胞DNA含量分布的影响。经MNNG(6.8μmol/L)处理后,细胞分裂减少,DNA合成速率下降,S期细胞的比例随处理时间的延长而增加。DMS显示有类似的现象而ENNG的效应则较小。 相似文献
8.
Jill Lancaster 《Oecologia》1996,107(3):321-331
The effects of hydraulic disturbances on the impact of two predatory benthic invertebrates on their prey were examined in a stream at two distinct spatial scales. At the scale of small habitat patches (0.0625 m2), hydraulic patch type was an important determinant of the microdistribution of prey and predators. Prey abundances were similar across all patch types at baseflow, but local densities were higher in patches identified as low-flow refugia after periods of high and fluctuating flow. The microdistribution pattern of predatory larvae of a caddisfly, Plectrocnemia conspersa, was similar to that of its prey, whereas predatory larvae of an alderfly, Sialis fuliginosa, did not shift their microdistribution significantly with discharge and were always most abundant in lowflow refugia. There was little evidence of an aggregative response of predators with prey, even though both predators and prey are mobile. Both predator species showed similar patch-specific patterns of per capita consumption rates: uniform consumption rates across hydraulic patch types at low and moderate flows, but highest in flow refugia during high flows. Species-specific patterns, however, were apparent in the magnitude and direction of differences between consumption rates during disturbance events, and in comparable patches at base flow: At high flow, consumption rates for P. conspersa were exaggerated (3.9 times higher) in flow refugia but at par in other patches; for S. fuliginosa they were at par in flow refugia but reduced in other patches (up to 3.3. times lower). These differences may be related to species-specific foraging behaviours (search vs ambush predators) and the influence of prey movements on feeding success. Using the patch-scale results only, it is difficult to predict the effects of physical disturbance on predation intensity at the larger scales of whole habitats, populations or communities. At the large scale (>200 m2), net predator impacts were estimated over the stream reach, using a spatially explicit model that accounts, in an additive way, for habitat heterogeneity and patch-specific responses of predators and prey. The relationship between predator impact over the whole reach and hydraulic disturbance differed for the two predators. The predator impact of S. fuliginosa decreased with increasing hydraulic disturbance, as predicted by the harsh-benign hypothesis. There was no directional trend for P. conspersa, however, and maximum predator impact may occur at intermediate disturbance levels. For the prey community in this stream, predation pressure from S. fuliginosa appears to fluctuate directly with the discharge hydrograph, whereas predation from P. conspersa may be more persistent. Flow refugia may play a dual role in the sructure of stream communities by preventing catastrophic mortality of animals (predators and prey) from physical forces during disturbances, and by maintaining (or perhaps increasing) predation pressure. Summing the effects of species interactions in small habitat patches to the larger scale of a whole stream reach indicates that the scale of approach influences the observed patterns and their implied underlying process. 相似文献
9.
M. Baranyi J. Greilhuber W. K. Swięcicki 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1996,93(5-6):717-721
Genome size was measured in 75 samples of the wild pea species Pisum abyssinicum, P. elatius, P. fulvum and P. humile by ethidium-bromide (EB) flow cytometry (internal standard: Triticum monococcum) and Feulgen densitometry (internal standard: Pisum sativum Kleine Rheinländerin). Total variation of EB-DNA between samples covered 97.7% to 114.9% of the P. sativum value, and Feulgen DNA values were strongly correlated with EB-DNA values (r=0.9317, P < 0.001). Only P. fulvum was homogeneous in genome size (108.9% of P. sativum). Wide variation was observed between samples in P. abyssinicum (100.9–109.7%), P. elatius (97.7–114.9%) and P. humile (98.3–111.1% of P. sativum). In view of the world-wide genome size constancy in P. sativum, the present data are interpreted to show that the pea taxa with variable genome size are genetically inhomogeneous and that the current classification is not sufficient to describe the biological species groups adequately. 相似文献
10.
S. Saisingtong J. E. Schmid P. Stamp B. Büter 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1996,92(8):1017-1023
Efficient methods of chromosome doubling are critical for the production of microspore-derived, doubled-haploid (=DH) plants, especially if, as in maize anther culture, spontaneous chromosome doubling occurs infrequently. In the present study, colchicine (5–1000 mg/l) was added to the induction medium and maize anthers were incubated in the colchicine-containing medium for different durations (1–7 days). In order to improve overall anther culture response, the culture temperature was adjusted to 14°C during the first 7 days. Colchicine applied at low concentration, i.e. 5 mg/l (7 days), or for short duration, i.e. 1–3 days (250 mg/l), showed beneficial effects on the formation of embryolike structures (=ES) and thus led to increased plant production, but was comparatively ineffective regarding chromosome doubling. Optimal doubling effects were observed when anthers had been exposed to culture medium containing 250 and 1000 mg/l of colchicine (7 days); in these treatments the doubling index (=DI), defined as the quotient of the number of DH plants and the number of totally regenerated plants in a specific treatment, rose to 0.56 and 0.53, respectively, compared to 0.20 in the untreated control. However, colchicine administered at concentrations higher than 250 mg/l seemed to be detrimental to general plant production; thus, in spite of a high DI, the overall DH plant production was even lower than in the control treatment. Maximum DH plant production for three different genotypes was accomplished with culture medium containing 250 mg/l of colchicine (7 days). With the best-responding genotype (ETH-M 36) a DH plant production of 9.9 DH plants/100 anthers was accomplished, i.e. a 7-fold increase compared to the non-treated anthers. This is the first report on efficient chromosome doubling in anther culture by subjecting anthers to colchicinecontaining induction medium during a post-plating cold treatment. Chromosome doubling as described here becomes an integral part of the maize anther culture protocol and thus represents a rapid and economical way to produce DH plants. 相似文献