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1.
Scott P. Lawrence Nicholas A. Bright J. Paul Luzio Katherine Bowers 《Molecular biology of the cell》2010,21(20):3540-3551
The pH and lumenal environment of intracellular organelles is considered essential for protein sorting and trafficking through the cell. We provide the first evidence that a mammalian NHE sodium (potassium)/proton exchanger, NHE8, plays a key role in the control of protein trafficking and endosome morphology. At steady state, the majority of epitope-tagged NHE8 was found in the trans-Golgi network of HeLa M-cells, but a proportion was also localized to multivesicular bodies (MVBs). Depletion of NHE8 in HeLa M-cells with siRNA resulted in the perturbation of MVB protein sorting, as shown by an increase in epidermal growth factor degradation. Additionally, NHE8-depleted cells displayed striking perinuclear clustering of endosomes and lysosomes, and there was a ninefold increase in the cellular volume taken up by LAMP1/LBPA-positive, dense MVBs. Our data points to a role for the ion exchange activity of NHE8 being required to maintain endosome morphology, as overexpression of a nonfunctional point mutant protein (NHE8 E225Q) resulted in phenotypes similar to those seen after siRNA depletion of endogenous NHE8. Interestingly, we found that depletion of NHE8, despite its function as a sodium (potassium)/proton antiporter, did not affect the overall pH inside dense MVBs. 相似文献
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John G. Neuhoff Katherine L. Long Rebecca C. Worthington 《Evolution and human behavior》2012,33(4):318-322
Listeners consistently perceive approaching sounds to be closer than they actually are and perceptually underestimate the time to arrival of looming sound sources. In a natural environment, this underestimation results in more time than expected to evade or engage the source and affords a “margin of safety” that may provide a selective advantage. However, a key component in the proposed evolutionary origins of the perceptual bias is the appropriate timing of anticipatory motor behaviors. Here we show that listeners with poorer physical fitness respond sooner to looming sounds and with a larger margin of safety than listeners with better physical fitness. The anticipatory perceptual bias for looming sounds is negatively correlated with physical strength and positively correlated with recovery heart rate (a measure of aerobic fitness). The results suggest that the auditory perception of looming sounds may be modulated by the response capacity of the motor system. 相似文献
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The ultrasonic calls produced by three day old mice when separated from the nest mother and siblings increase in number when naloxone is injected. 相似文献
6.
1. Male Japanese quail were given 2.20 x 10(-4)-14.53 mg uranium/kg intravenously as uranyl ion (235U label). 2. The relationship between dosage and the 18-hr accumulation of U in leg bones, liver, kidneys and testes was linear. 3. Increases in U deposition with increased dosage were approximately 1:1, except for kidneys where 10-fold increases in dosage resulted in 25-fold increases in deposition. 4. Estradiol-17 beta increased U deposition in bones by 15-fold thereby providing some protection for the kidneys as now the ratio of dosage to accumulation was 1:1. 相似文献
7.
R Philipp J O McIntyre B H Robinson H Huth W Trommer S Fleischer 《Biochimica et biophysica acta》1984,790(3):251-258
Calcium efflux and EGTA-induced calcium release from an internal platelet membrane fraction have been studied after the oxalate-supported calcium uptake had reached steady state. Increasing external calcium concentrations stimulate the calcium efflux velocity, with an apparent half-maximal stimulation at about 5 microM outside calcium concentration and a maximal velocity of calcium efflux of 4.66 +/- 2.32 nmol X min-1 X mg-1. Moreover, the ratio of the liberated calcium on the loaded calcium seems to be independent of the increasing external calcium concentration. Increasing the calculated internal calcium concentration by varying the oxalate potassium concentration from 10 mM to 1 mM results in an increase of the liberated calcium from the membrane vesicles from 7.4% to 63%, respectively, without changing the calcium efflux velocity. Similar conclusions can be drawn from the observation of results from the calcium efflux and EGTA-induced calcium release methods. Moreover, calcium pump reversal does not seem to be responsible for the calcium efflux or calcium release. All these different points added to the previously described regulation of calcium efflux by the catalytic subunit of cAMP protein kinase suggest us that the mechanism of calcium liberation by the platelet membranes is different from the calcium uptake. 相似文献
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Ferdinand Bohlmann Elena Tsankova Jasmin Jakupovic Robert M. King Harold Robinson 《Phytochemistry》1983,22(2):557-560
The investigation of Encelia canescens afforded, in addition to several known compounds, four new dimeric p-hydroxyacetophenone derivatives, two epimeric chromene dimers and two epimeric mixed dimers of euparin and encecalin. Furthermore, derivatives of tremetone and of encecalin were present. The structures were elucidated hy high field 1H NMR spectroscopy. 相似文献
10.
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