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181.
Symplastic Transfer of Fluorescent Dyes from Mesophyll to Sieve Tube in Stripped Leaf Tissue and Partly Isolated Minor Veins of Commelina benghalensis 总被引:3,自引:1,他引:2 下载免费PDF全文
We have stripped small (3 × 3 mm) fields of the upper and the opposite lower epidermis of Commelina benghalensis leaves. Pectinase treatment of the resulting chlorenchyma windows produced free-lying viable minor veins with small lumps of mesophyll cells attached. These veins were still connected with the intact remainder of the leaf. Fluorescent dyes were injected into mesophyll cells or mestome sheath cells. Continuous following of the dye from the moment of injection and use of the simple vein system allowed an unhindered and precise assessment of the cell-to-cell route of dye transfer. Disodium fluorescein and Lucifer Yellow CH injected into mesophyll or mestome sheath cells readily moved to the sieve tube. This symplastic dye transfer from mesophyll to sieve tube was also observed after injection into unmacerated stripped leaf tissue. The displacement of fluorescent dyes substantiates a symplastic continuity between mesophyll and sieve tube and therefore supports the possibility of symplastic phloem loading. 相似文献
182.
J Nakagawa D von der Ahe D Pearson B A Hemmings S Shibahara Y Nagamine 《The Journal of biological chemistry》1988,263(5):2460-2468
183.
A J Marcus L B Safier H L Ullman N Islam M J Broekman J R Falck S Fischer C von Schacky 《The Journal of biological chemistry》1988,263(5):2223-2229
In the course of a cell-cell interaction, 12-HETE (12-hydroxy-5,8,10,14-eicosatetraenoic acid), the arachidonic acid lipoxygenase product released from stimulated platelets, is metabolized by a cytochrome P-450 enzyme system in unstimulated neutrophils to 12,20-DiHETE (12,20-dihydroxy-5,8,10,14-eicosatetraenoic acid). This report describes time-dependent formation of a new eicosanoid by unstimulated neutrophils exposed to 12-HETE, which is more polar than 12,20-DiHETE (reversed-phase high performance liquid chromatography). Time course studies indicated that the precursor compound of this new eicosanoid was 12,20-DiHETE. This was determined by incubation of purified 12,20-DiHETE with neutrophils, which resulted in a progressive decrease in 12,20-DiHETE as formation of the polar metabolite increased. In the absence of neutrophils, 12,20-DiHETE was quantitatively unchanged. The new metabolite of 12,20-DiHETE was identified as 12-hydroxyeicosatetraen-1,20-dioic acid, based upon its UV spectrum, co-chromatography with a chemically synthesized standard in both high performance liquid chromatography and thin layer chromatography systems, and gas chromatography-mass spectrometry. Formation of 12-HETE-1,20-dioic acid was partially inhibited by 20-hydroxy-LTB4. This indicated that the neutrophil dehydrogenase responsible for further metabolism of 12,20-DiHETE may also be involved in conversion of 20-hydroxy-LTB4 to 20-carboxy-LTB4. The 12,20-DiHETE dehydrogenase enzyme system specifically requires NAD as cofactor and has subcellular components in both cytosolic and microsomal fractions which are synergistic in their activity. These results provide additional evidence for the occurrence of multicellular metabolic events during hemostasis, thrombosis, and the inflammatory response. 相似文献
184.
M M Mulder H M Van der Gulden P W Postma K Van Dam 《Journal of general microbiology》1988,134(3):777-783
The steady-state bacterial dry wt of Escherichia coli, growing under K+-limited conditions in the chemostat, was inversely dependent on the growth rate. This phenomenon was more carefully investigated in medium-flow stop experiments. Growth did not stop immediately but continued for a time, initially at the same rate as before. The dry wt increased to a value corresponding to a steady-state growth rate near zero, independent of the initial specific growth rate. This was observed in both the wild-type strain and a mutant that lacked the high-affinity K+ uptake system. The wild-type strain maintained a low extracellular K+ concentration both in the chemostat under steady-state conditions and after stopping the medium flow. The mutant, on the other hand, maintained a much higher extracellular K+ concentration in the steady state, which decreased to much lower values after stopping the medium flow. From the increase in bacterial dry wt and the low external K+ concentration after stopping the medium flow it is concluded that the intracellular K+ is redistributed among the cells, including new cells. The growth yield on K+ was highest in the stationary growth phase of a batch culture and all steady-state cultures converged ultimately to this yield value after the medium flow had been stopped. It is proposed that the growth rate of E. coli under K+-limited conditions is determined by the intracellular K+ concentration. 相似文献
185.
M Capron M Tomassini E Van der Vorst J P Kusnierz J P Papin A Capron 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1988,307(7):397-402
The existence of receptors for immunoglobulin A on human eosinophils is demonstrated by flow cytofluorometry. Between 5 and 60% of eosinophils purified from peripheral blood of hypereosinophilic patients are able to bind monomeric serum IgA. The addition of antihuman IgA antibodies to surface IgA-bearing eosinophils induces the exocytosis of peroxidase contained in the granules suggesting a cell activation due to IgA receptors. The inhibition of antiparasitic cytotoxicity by eosinophils preincubated with IgA under a polymeric form only, indicates the low affinity of IgA receptors as well as their participation in the effector function of eosinophils. 相似文献
186.
Mechanism of neutrophil activation by NAF, a novel monocyte-derived peptide agonist 总被引:27,自引:0,他引:27
The rise in cytosolic free Ca2+, shape change, superoxide formation, and granule exocytosis induced in human neutrophils by N-formyl-Met-Leu-Phe (fMLP) and by a newly discovered activating peptide, neutrophil-activating factor, termed NAF, were compared. NAF was effective in the concentration range of 0.1-10 nM and was 10- to 100-fold more potent than fMLP. In qualitative terms, the single responses to either stimulus were remarkably similar: they showed virtually identical onset and initial kinetics, and were all inhibited by pretreatment of the neutrophils with Bordetella pertussis toxin. In addition, the respiratory burst elicited by either stimulus was inhibited by 17-hydroxywortmannin and staurosporine. Two conclusions are drawn from these results: 1) neutrophil activation by NAF (as by fMLP) is dependent on a GTP-binding protein and on protein kinase C; 2) a similar, or even identical, mechanism of signal transduction must be assumed on stimulation of human neutrophils with NAF, fMLP, and other chemotactic agonists. Human monocytes, lymphocytes, and platelets did not show cytosolic free Ca2+ changes when exposed to NAF, which suggests that NAF is selective for the neutrophils. 相似文献
187.
Total cellular fatty acids for 20 strains of Erwinia amylovora grown on trypticase soy agar (TSA) for 3 days at 27°C, and for 3 strains grown on nutrient agar (NA), King's B (KB), glucoseyeast extract carbonate (GYCA) and TSA for 1, 3 and 6 days were analyzed by gas-liquid chromatography. Forty one percent of total fatty acids were saturated even-carbon straight chains, 6 % were saturated odd-carbon chains, 34 % unsaturated acids, 6 % hydroxy-substituted acids, 1 % branched chains, 7 % cyclic acids, and 4 % unidentified components. Composition was affected by growth medium, physiological age of cells, and chromatograph sensitivity. On TSA and NA saturated odd-carbon and cyclic acids of the 3 strains (combining 1, 3 and 6-day data) were higher than on KB and GYCA. Cyclic acids increased with physiological age on GYCA and KB medium. Even-carbon straight chain and unsaturated fatty acids (major components) constituted a significantly lower percentage of total fatty acids in chromatograms of high sensitivity (30–50 components) than of low instrument sensitivity (15–20 components). 相似文献
188.
Summary A novel stable isotope labelling procedure for microbeam analysis was developed to monitor exchange and uptake of nutrients, primarily Mg, K and Ca, by root tips at the cellular level. Initially root samples were analysed from 2-year-old spruce trees, originating both from a nursery and from a polluted forest site, (1) for the cortex cell wall accessibility and nutrient binding properties, (2) for the influence of low pH and elevated aluminum concentrations on Ca binding to cortex cell walls, and (3) for long-range transport into the secondary xylem, proximal to the labelled root tip. In nursery control plants, Ca is localized mainly in the apoplast of the cortex. Exchange of Mg, K, Ca in the cell wall of the cortex and the primary xylem with label in incubation solutions is almost completed to equilibration within 30 min. In the secondary xylem we could detect Mg, K, and Ca from labelling solutions in minute amounts after 30 min, and as a major fraction after 48 h. This indicates that stable isotope labelling can be used to study both ion-exchange properties of the apoplast and long-range transport. Slight acidification of the labelling incubation media to pH 4.5 reduced Ca binding to the cortex cell walls slightly, but acidification to the extreme value of pH 2.3 reduced binding 41%. A combination of pH 4.5 and increased free aluminum reduced the binding by 83%. In a preliminary attempt to analyse the nutrient binding capability of the root-tip apoplast from pollution affected trees, we exposed fine roots of 2-year-old spruce from an acidified and polluted site showing typical low levels of Ca and Mg in the cortical cell walls to Ca-enriched media. Under these conditions the Ca content of cortex cell walls doubled upon incubation at pH 4.7, reaching 40% of the total binding capacity of our nursey control plants. 相似文献
189.
In situ hybridization as a tool to study numerical chromosome aberrations in solid bladder tumors 总被引:14,自引:0,他引:14
A. H. N. Hopman F. C. S. Ramaekers A. K. Raap J. L. M. Beck P. Devilee M. van der Ploeg G. P. Vooijs 《Histochemistry and cell biology》1988,89(4):307-316
Summary Methods for single- and double-target in situ hybridization (ISH) to, cells isolated from solid transitional cell carcinomas (TCC's) of the urinary bladder are described. Single cell suspensions were prepared from solid tumors of the urinary bladder by mechanical disaggregation and fixed in 70% ethanol. Using two DNA probes specific for the centromeres of chromosomes #1 and #18, ISH procedures were optimized for these samples. Human lymphocytes and cells from the T24 bladder tumor cell line were used as controls. In lymphocyte nuclei and metaphase chromosome spreads, ISH showed two major spots for each of the probes. About 80% of the nuclei from T24 cells showed three spots for both the chromosome #1 and #18 specific probes. When nuclei from TCC's were analyzed, often the number of spots for chromosome #1, and to a lesser extent for chromosome #18, differed from the number expected on basis of flow cytometric ploidy measurements. The double target-ISH method in all cases allowed the correlation of numerical aberrations for chromosomes #1 and #18 in one and the same cell. By such analyses a profound heterogeneity in chromosome number was detected in most tumors. In order to optimize the reproductbility of the method and the interpretation of the ISH-signals, criteria for their analysis have been determined. This procedure can now be applied on a routine basis to solid tumor specimens. 相似文献
190.
Three copies of a single protein II-encoding sequence in the genome of Neisseria gonorrhoeae JS3: evidence for gene conversion and gene duplication 总被引:13,自引:8,他引:5
Gonococci express a family of related outer membrane proteins designated protein II (P.II). These surface proteins are subject to both phase variation and antigenic variation. The P.II gene repertoire of Neisseria gonorrhoeae strain JS3 was found to consist of at least ten genes, eight of which were cloned. Sequence analysis and DNA hybridization studies revealed that one particular P.II-encoding sequence is present in three distinct, but almost identical, copies in the JS3 genome. These genes encode the P.II protein that was previously identified as P.IIc. Comparison of their sequences shows that the multiple copies of this P.IIc-encoding gene might have been generated by both gene conversion and gene duplication. 相似文献