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21.
Uptake of GABA by rat brain synaptic vesicles isolated by a new procedure. 总被引:19,自引:5,他引:14
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Uptake of GABA was demonstrated in rat brain synaptic vesicles which were prepared by a new and efficient procedure. The uptake activity co-purified with the synaptic vesicles during the isolation procedure. The purity of the vesicle fraction was rigorously examined by analysis of marker enzymes and marker proteins and also by immunogold electron microscopy using antibodies against p38 (synaptophysin). Contamination by other cellular components was negligible, indicating that GABA uptake by the synaptic vesicle fraction is specific for synaptic vesicles and not due to the presence of other structure possessing GABA uptake or binding activities. GABA uptake was ATP dependent and similar to the uptake of glutamate, which was assayed for a comparison. Both uptake activities were independent of sodium. They were inhibited by the uncoupler carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone, indicating that the energy for the uptake is provided by an electrochemical proton gradient. This gradient is generated by a proton ATPase of the vacuolar type as suggested by the effects of various ATPase inhibitors on neurotransmitter uptake and proton pumping. Competition experiments revealed that the transporters for GABA and glutamate are selective for the respective neurotransmitters. 相似文献
22.
Water culture, growth chamber, greenhouse and field experiments were conducted to compare the effect of NH4−N and NO3−N on yield and N uptake of rapeseed (Brassica campestris L.). In water culture, the yields of 28-day old rapeseed plants grown at 14 μg N ml−1 were double with NO3 compared to NH4, but N uptake was little affected. There was no such effect when concentration was reduced to 3.5 or 7 μg N ml−1. The yield and N uptake of 26-day old rapeseed grown on six soils (pH 4.6 to 6.5) in pots in a growth chamber were much greater
with NO3 than with NH4, although N concentration was more in the NH4- than the NO3-grown plants. In a greenhouse experiment with rapeseed grown on 12 potted soils, the N uptake of applied N was greater with
NO3 than with NH4 on all soils. Averages were 63% with NH4 and 78% with NO3. However, NH4-fixation capacities of the soils were only weakly correlated with yield from the two sources of N (r=0.48) and the relation
was similar with N uptake. In contrast to the behavior of water culture, growth chamber and greenhouse experiments, the 33
field experiments did not show consistent difference in seed yield with NH4 and NO3 applied at time of seeding. In nine field experiments where band application was used for Ca(NO3)2, (NH4)2 SO4, NH4 NO3, yield tended to be greatest for (NH4)2SO4. However, in 19 experiments on acid soils with and without lime, yields in most cases were similar with (NH4)2SO4 and NH4 NO3. Nitrification inhibitors were added to spring banded NH4-based fertilizers in five experiments, but the yields were not influenced.
Scientific Paper No. 558, Lacombe Research Station, Agriculture Canada. 相似文献
23.
24.
Tina Pallesen Annette Vangsted Lars Drivsholm Henrik Clausen Jesper Zeuthen Håkan Wallin 《Glycoconjugate journal》1992,9(6):331-335
We here report an enzyme linked immunosorbent assay (ELISA) and a scintillation proximity assay (SPA) for detection of the ganglioside FucGM1 in sera from small cell lung cancer (SCLC) patients. The SPA was more sensitive and reproducible than the ELISA. In this assay, monoclonal antibodies specific for FucGM1 were bound to SPA particles and incubated with labelled FucGM1 and 100 µl test-serum overnight, and counted in a -counter. The sensitivity was 0.2 ng. Seven out of twenty sera from SCLC patients were positive, whereas none of twenty sera from healthy individuals were positive for FucGM1. The SPA was more sensitive than the previously reported HPTLC as well as a direct ELISA.Abbreviations MAb
monoclonal antibody
- SPA
scintillation proximity assay
- HPTLC
high performance thin layer chromatography
- SCLC
small cell lung cancer
- FucGM1
Fuc1-2Gal1-3GalNAc1-4(NeuAc2-3)-Gal1-4Glc1-1Cer
- ELISA
enzyme linked immunosorbent assay
- FCS
foetal calf serum
- PBS
phosphate buffered saline 相似文献
25.
The effects of the local anesthetic dibucaine on coupling between electron transport and ATP synthesis-hydrolysis by the coupling-factor complex (CF0CF1 ATPase) were investigated in thylakoid membranes from Spinacia oleracea L. cv. Monatol. Evidence is presented that inhibition of ATP synthesis was produced by a specific uncoupling mechanism which was based on dibucaine-membrane surface interactions rather than on the interaction of dibucaine with the ATPase complex. Dibucaine reduced the osmotic space of thylakoid vesicles. At low pH of the medium it stimulated ATP hydrolysis beyond the rates obtained with optimum concentrations of ‘classical’ uncouplers. After addition of dibucaine, there was displacement of membrane-bound Mg2+ and strong thylakoid stacking in the presence of only low Mg2+ concentrations. Inhibition of ATP synthesis and transmembrane pH gradient increased with medium pH. Hydrolysis of ATP by isolated CF1 and the CF0CF1 complex was only slightly affected by dibucaine. The data are discussed assuming the involvement of localized proton channels on the membrane surface in protonic coupling of electron transport and ATP synthesis. A hypothesis for the mechanisms of action of local anesthetics at the thylakoid membrane is presented. 相似文献
26.
Ingemar Fries Aasne Aarhus Henrik Hansen Seppo Korpela 《Experimental & applied acarology》1991,10(3-4):279-287
Thirty-five honey-bee colonies, originally free fromVarroa jacobsoni (Oudemans) were monitored approximately every third week for the presence of the mite during 16 months following an initial introduction of five to eight adultVarroa females in early July. Investigations of hive debris detected the presence ofV. jacobsoni in 22 colonies (63%) within three months of the mite introduction. During the first winter period (October–April), mites were found in the hive debris of 13 colonies (37%). In terms of detectingVarroa during the summer in colonies with sealed brood, investigations of hive debris were more effective than sampling of brood. Brood sampling was more effective than sampling of live bees. In colonies without sealed brood, investigations of hive debris or of live bee samples seemed approximately equally efficient. The highest correlation between sampling methods was found between daily mite downfall and mites per live bee (r=0.81) in colonies with sealed brood. During the winter, investigations of dead bees and hive debris were approximately equally efficient in detectingVarroa. 相似文献
27.
Summary The production of somatic embryos from carrot suspension cultures invariably decreases through simple, repeated subculturing.
Extracellular, concentrated compounds extracted from already established embryo culture not only recovered the embryogenic
capability, but also accelerated the embryo production as much as two-fold (up to 1600 embryos/ml) compared with that of a
control culture. Sugars, which were only a small portion of the total concentrate, were excluded as possible causative factors.
It is likely that a protein fraction that is generated directly by competent, embryogenic cultures is important for the restoration
of embryogenic potential. 相似文献
28.
29.
In the hypotrichous ciliated protozoan Oxytricha nova, approximately 95% of the micronuclear genome, including all of the repetitive DNA and most of the unique sequence DNA, is eliminated during the formation of the macronuclear genome. We have examined the interspersion patterns of repetitive and unique and eliminated and retained sequences in the micronuclear genome by characterizing randomly selected clones of micronuclear DNA. Three major classes of clones have been defined: (1) those containing primarily unique, retained sequences; (2) those containing only unique, eliminated sequences; and (3) those containing only repetitive, eliminated sequences. Clones of type one and three document two aspects of organization observed previously: clustering of macronuclear destined sequences and the presence of a prevalent repetitive element. Clones of the second type demonstrate for the first time that eliminated unique sequence DNA occurs in long stretches uninterrupted by repetitive sequences. To further examine repetitive sequence interspersion, we characterized the repetitive sequence family that is present in 50% of the clones (class three above). A consensus map of this element was obtained by mapping approximately 80 phage clones and by hybridization to digests of micronuclear DNA. The repeat element is extremely large (approximately 24 kb) and is interspersed with both macronuclear destined sequences and eliminated unique sequences. 相似文献
30.
Extracellular Overflow of Neuroactive Amino Acids During Severe Insulin-Induced Hypoglycemia: In Vivo Dialysis of the Rat Hippocampus 总被引:21,自引:11,他引:10
Hypoglycemia-evoked changes in levels of extracellular excitatory and inhibitory amino acids were studied using the microdialysis technique. A newly designed dialysis probe was inserted stereotaxically into the rat hippocampus. Animals were then subjected to insulin-induced hypoglycemia; then blood glucose levels were restored by glucose injections after a 30-min period of isoelectric electroencephalography. Dialysates were collected before, during, and after the isoelectric period. Amino acids in the dialysates were analyzed by liquid chromatography and fluorescence detection following automatic precolumn derivatization with o-phthaldialdehyde. During the isoelectric phase, the concentration of aspartate increased 15-fold, whereas glutamate, gamma-amino-butyric acid, taurine, and phosphoethanolamine levels were elevated three- to sixfold. Smaller increases were observed for nonneuroactive amino acids such as asparagine, alanine, and phenylalanine. In contrast to all other amino acids, the glutamine content was reduced to less than 30% of preisoelectric values. The concentrations of the neuroactive amino acids were restored to normal in the post-isoelectric phase. These data demonstrate that there is an extracellular overflow of neuroactive amino acids, especially aspartate, during severe hypoglycemia. 相似文献