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21.
AB Kane RP Stanton EG Raymond ME Dobson ME Knafelc JL Farber 《The Journal of cell biology》1980,87(3):643-651
The relationship between intracellular lysosomal rupture and cell death caused by silica was studied in P388d(1) macrophages. After 3 h of exposure to 150 μg silica in medium containing 1.8 mM Ca(2+), 60 percent of the cells were unable to exclude trypan blue. In the absence of extracellular Ca(2+), however, all of the cells remained viable. Phagocytosis of silica particles occurred to the same extent in the presence or absence of Ca(2+). The percentage of P388D(1) cells killed by silica depended on the dose and the concentration of Ca(2+) in the medium. Intracellular lyosomal rupture after exposure to silica was measured by acridine orange fluorescence or histochemical assay of horseradish peroxidase. With either assay, 60 percent of the cells exposed to 150 μg silica for 3 h in the presence of Ca(2+) showed intracellular lysosomal rupture, was not associated with measureable degradation of total DNA, RNA, protein, or phospholipids or accelerated turnover of exogenous horseradish peroxidase. Pretreatment with promethazine (20 μg/ml) protected 80 percent of P388D(1) macrophages against silica toxicity although lysosomal rupture occurred in 60-70 percent of the cells. Intracellular lysosomal rupture was prevented in 80 percent of the cells by pretreatment with indomethacin (5 x 10(-5)M), yet 40-50 percent of the cells died after 3 h of exposure to 150 μg silica in 1.8 mM extracellular Ca(2+). The calcium ionophore A23187 also caused intracellular lysosomal rupture in 90-98 percent of the cells treated for 1 h in either the presence or absence of extracellular Ca(2+). With the addition of 1.8 mM Ca(2+), 80 percent of the cells was killed after 3 h, whereas all of the cells remained viable in the absence of Ca(2+). These experiments suggest that intracellular lysosomal rupture is not causally related to the cell death cause by silica or . Cell death is dependent on extracellular Ca(2+) and may be mediated by an influx of these ions across the plasma membrane permeability barrier damaged directly by exposure to these toxins. A23187相似文献
22.
Maino James L. Schouten Rafael Lye Jessica C. Umina Paul A. Reynolds Olivia L. 《Biological invasions》2022,24(7):2155-2167
Biological Invasions - The Spotted Lantern Fly (SLF), Lycorma delicatula (Hemiptera: Fulgoridae), is a sap feeding pest native to southeast Asia that has become a global biosecurity threat... 相似文献
23.
Archaeal and Bacterial Glycerol Dialkyl Glycerol Tetraether Lipids in Hot Springs of Yellowstone National Park 总被引:1,自引:1,他引:1
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Stefan Schouten Marcel T. J. van der Meer Ellen C. Hopmans W. Irene C. Rijpstra Anna-Louise Reysenbach David M. Ward Jaap S. Sinninghe Damst 《Applied microbiology》2007,73(19):6181-6191
Glycerol dialkyl glycerol tetraethers (GDGTs) are core membrane lipids originally thought to be produced mainly by (hyper)thermophilic archaea. Environmental screening of low-temperature environments showed, however, the abundant presence of structurally diverse GDGTs from both bacterial and archaeal sources. In this study, we examined the occurrences and distribution of GDGTs in hot spring environments in Yellowstone National Park with high temperatures (47 to 83°C) and mostly neutral to alkaline pHs. GDGTs with 0 to 4 cyclopentane moieties were dominant in all samples and are likely derived from both (hyper)thermophilic Crenarchaeota and Euryarchaeota. GDGTs with 4 to 8 cyclopentane moieties, likely derived from the crenarchaeotal order Sulfolobales and the euryarchaeotal order Thermoplasmatales, are usually present in much lower abundance, consistent with the relatively high pH values of the hot springs. The relative abundances of cyclopentane-containing GDGTs did not correlate with in situ temperature and pH, suggesting that other environmental and possibly genetic factors play a role as well. Crenarchaeol, a biomarker thought to be specific for nonthermophilic group I Crenarchaeota, was also found in most hot springs, though in relatively low concentrations, i.e., <5% of total GDGTs. Its abundance did not correlate with temperature, as has been reported previously. Instead, the cooccurrence of relatively abundant nonisoprenoid GDGTs thought to be derived from soil bacteria suggests a predominantly allochthonous source for crenarchaeol in these hot spring environments. Finally, the distribution of bacterial branched GDGTs suggests that they may be derived from the geothermally heated soils surrounding the hot springs. 相似文献
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25.
Sara Borin Francesca Mapelli Eleonora Rolli Bongkeun Song Craig Tobias Markus C. Schmid Gert J. De Lange Gert J. Reichart Stefan Schouten Mike Jetten Daniele Daffonchio 《Extremophiles : life under extreme conditions》2013,17(2):289-299
To extend the knowledge of anaerobic ammonium oxidation (anammox) habitats, bacterial communities were examined in two hypersaline sulphidic basins in Eastern Mediterranean Sea. The 2 m thick seawater–brine haloclines of the deep anoxic hypersaline basins Bannock and L’Atalante were sampled in intervals of 10 cm with increasing salinity. 15N isotope pairing incubation experiments showed the production of 29N2 and 30N2 gases in the chemoclines, ranging from 6.0 to 9.2 % salinity of the L’Atalante basin. Potential anammox rates ranged from 2.52 to 49.65 nmol N2 L?1 day?1 while denitrification was a major N2 production pathway, accounting for more than 85.5 % of total N2 production. Anammox-related 16S rRNA genes were detected along the L’Atalante and Bannock haloclines up to 24 % salinity, and the amplification of the hydrazine synthase genes (hzsA) further confirmed the presence of anammox bacteria in Bannock. Fluorescence in situ hybridisation and sequence analysis of 16S rRNA genes identified representatives of the marine anammox genus ‘Candidatus Scalindua’ and putatively new operational taxonomic units closely affiliated to sequences retrieved in marine environments that have documented anammox activity. ‘Scalindua brodae’ like sequences constituted up to 84.4 % of the sequences retrieved from Bannock. The anammox community in L’Atalante was different than in Bannock and was stratified according to salinity increase. This study putatively extends anammox bacterial habitats to extremely saline sulphidic ecosystems. 相似文献
26.
Differences in acidity of apples are probably mainly caused by a malic acid transporter gene on LG16
Sabaz Ali Khan Jules Beekwilder Jan G. Schaart Roland Mumm Jose Miguel Soriano Evert Jacobsen Henk J. Schouten 《Tree Genetics & Genomes》2013,9(2):475-487
Acidity has profound effects on the taste of apples (Malus × domestica). Malic acid is the predominant organic acid in apples. Differences in malic acid content are caused by differences in accumulation of malic acid in the vacuole. This accumulation may be caused by a gene that is responsible for transport of malic acid from the cytosol into the vacuole. Here, we provide evidence that a malic acid transporter gene at the top of chromosome 16 caused significant differences in malic acid concentration and pH of apples. The pH of apples in a segregating F1 population was mapped and at the pH locus (named henceforth Ma locus for malic acid), two putative malic acid transporter genes were detected. These genes show high homology to AtALMT genes that code for malate channel proteins located in vacuolar membrane in Arabidopsis. The expression of one of the candidate genes (Ma1) cosegregated clearly with malic acid content. The inheritance of at least one dominant allele of this gene sufficed for an increased expression level that likely caused the observed threefold increase of the malic acid concentration and the reduction of the pH from 4 to 3 in mature apples, compared to the presence of the recessive, lowly expressed allele only. Our results show that differences in fruit acidity were probably caused by differences in expression levels of alleles of a malic acid transporter gene. 相似文献
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28.
Phosphatidylinositol transfer protein alpha (PITP alpha) is a ubiquitous and highly conserved protein in multicellular eukaryotes that catalyzes the exchange of phospholipids between membranes in vitro and participates in cellular phospholipid metabolism, signal transduction and vesicular trafficking in vivo. Here we report the three-dimensional crystal structure of a phospholipid-free mouse PITP alpha at 2.0 A resolution. The structure reveals an open conformation characterized by a channel running through the protein. The channel is created by opening the phospholipid-binding cavity on one side by displacement of the C-terminal region and a hydrophobic lipid exchange loop, and on the other side by flattening of the central beta-sheet. The relaxed conformation is stabilized at the proposed membrane association site by hydrophobic interactions with a crystallographically related molecule, creating an intimate dimer. The observed open conformer is consistent with a membrane-bound state of PITP and suggests a mechanism for membrane anchoring and the presentation of phosphatidylinositol to kinases and phospholipases after its extraction from the membrane. Coordinates have been deposited in the Protein Data Bank (accession No. 1KCM). 相似文献
29.
Candidatus "Scalindua brodae", sp. nov., Candidatus "Scalindua wagneri", sp. nov., two new species of anaerobic ammonium oxidizing bacteria 总被引:1,自引:0,他引:1
Schmid M Walsh K Webb R Rijpstra WI van de Pas-Schoonen K Verbruggen MJ Hill T Moffett B Fuerst J Schouten S Damsté JS Harris J Shaw P Jetten M Strous M 《Systematic and applied microbiology》2003,26(4):529-538
Anaerobic ammonium oxidation (anammox) is both a promising process in wastewater treatment and a long overlooked microbial physiology that can contribute significantly to biological nitrogen cycling in the world's oceans. Anammox is mediated by a monophyletic group of bacteria that branches deeply in the Planctomycetales. Here we describe a new genus and species of anaerobic ammonium oxidizing planctomycetes, discovered in a wastewater treatment plant (wwtp) treating landfill leachate in Pitsea, UK. The biomass from this wwtp showed high anammox activity (5.0 +/- 0.5 nmol/mg protein/min) and produced hydrazine from hydroxylamine, one of the unique features of anammox bacteria. Eight new planctomycete 16S rRNA gene sequences were present in the 16S rRNA gene clone library generated from the biomass. Four of these were affiliated to known anammox 16S rRNA gene sequences, but branched much closer to the root of the planctomycete line of descent. Fluorescence in situ hybridization (FISH) with oligonucleotide probes specific for these new sequences showed that two species (belonging to the same genus) together made up > 99% of the planctomycete population which constituted 20% of the total microbial community. The identification of these organisms as typical anammox bacteria was confirmed with electron microscopy and lipid analysis. The new species, provisionally named Candidatus "Scalindua brodae" and "Scalindua wagneri" considerably extend the biodiversity of the anammox lineage on the 16S rRNA gene level, but otherwise resemble known anammox bacteria. Simultaneously, another new species of the same genus, Candidatus "Scalindua sorokinii", was detected in the water column of the Black Sea, making this genus the most widespread of all anammox bacteria described so far. 相似文献
30.
In previous work it has been shown in posture experiments of the human arm that reflexive dynamics were substantial for narrow-band
stochastic force disturbances. The estimated reflex gains varied substantially with the frequency content of the disturbances.
The present study analyses a simplified linear model of the reflexive feedback control loop, to provide an explanation for
the observed behaviour. The model describes co-activation and reflexive feedback. The task instruction `minimize the displacements'
is represented mathematically by a cost function that is minimized by adjusting the parameters of the model. Small-amplitude
displacements allow the system to be analysed with a quasi-linear approach. The optimization results clarify the limited effectiveness
of reflexive feedback on the system's closed-loop behaviour, which emanates from the time delay present in the reflex loops.
For low-frequency inputs less than 5 Hz, boundary-stable solutions with high reflex gains are predicted to be optimal. Input
frequencies near the system's eigenfrequency (about 5 Hz), however, would be amplified and result in oscillatory behaviour.
As long as the disturbance does not excite these frequencies, boundary stability will be optimal. The predicted reflex gains
show a striking similarity with the estimated reflex gains from the experimental study. The present model analysis also provides
a clear explanation for the negative reflex gains, estimated for near-sinusoidal inputs beyond 1.5 Hz.
Received: 24 January 2000 / Accepted in revised form: 7 July 2000 相似文献