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121.
We have previously shown in cultured rat microvascular endothelial cells (RMEC) that lipopolysaccharide (LPS) stimulates a protein tyrosine kinase (PTK)-dependent reduction in cellular coupling. We hypothesized that connexin 43 (Cx43) becomes phosphorylated following exposure to LPS. Cx43 was immunoprecipitated from control and LPS-treated RMEC monolayers. Tyrosine phosphorylation of Cx43, detected by immunoblot, was found only in the LPS treatment. To verify these results, Cx43 was radiolabeled with [(32)P]-orthophosphate. Radiolabeled Cx43 exhibited a slight increase in phosphorylation in response to LPS; phosphoamino acid analysis displayed equivalent amounts of phosphoserine in control and LPS treatments, but detected phosphotyrosine only in the LPS treatment. The PTK inhibitors PP-2 (10 nM) and geldanamycin (200 nM) were found to block the response to LPS in terms of Cx43 tyrosine phosphorylation and cellular coupling. The phosphatase inhibitor BpV (1 microM) accentuated the effect of LPS, while the putative phosphatase activator C(6)-ceramide prevented it. When measuring cell communication, phosphatase inhibition also blocked the reversal of the LPS response following LPS washout. We conclude that Cx43 is tyrosine phosphorylated following exposure to LPS and suggest that the LPS-induced increase in intercellular resistance may be mediated by tyrosine phosphorylation of this connexin. Altering tyrosine kinase and phosphatase activities can modulate the LPS-induced tyrosine phosphorylation of Cx43 and reductions in cellular coupling. 相似文献
122.
Hoeks FW Boon LA Studer F Wolff MO van der Schot F Vrabél P van der Lans RG Bujalski W Manelius A Blomsten G Hjorth S Prada G Luyben KCh Nienow AW 《Journal of industrial microbiology & biotechnology》2003,30(2):118-128
Foam disruption by agitation—the stirring as foam disruption (SAFD) technique—was scaled up to pilot and production scale
using Rushton turbines and an up-pumping hydrofoil impeller, the Scaba 3SHP1. The dominating mechanism behind SAFD—foam entrainment—was
also demonstrated at production scale. The mechanistic model for SAFD defines a fictitious liquid velocity generated by the
(upper) impeller near the dispersion surface, which is correlated with complete foam disruption. This model proved to be scalable,
thus enabling the model to be used for the design of SAFD applications. Axial upward pumping impellers appeared to be more
effective with respect to SAFD than Rushton turbines, as demonstrated by retrofitting a 12,000 l bioreactor, i.e. the triple
Rushton configuration was compared with a mixed impeller configuration from Scaba with a 20% lower ungassed power draw. The
retrofitted impeller configuration allowed 10% more broth without risking excessive foaming. In this way a substantial increase
in the volumetric productivity of the bioreactor was achieved. Design recommendations for the application of SAFD are given
in this paper. Using these recommendations for the design of a 30,000 l scale bioreactor, almost foamless Escherichia coli fermentations were realised.
Electronic Publication 相似文献
123.
Extracellular phosphatase activity of natural plankton studied with ELF97 phosphate: fluorescence quantification and labelling kinetics 总被引:4,自引:0,他引:4
ELF(R)97 phosphate (ELFP) is a phosphatase substrate which produces ELF(R)97 alcohol (ELFA), a fluorescent water-insoluble product, upon hydrolysis. We studied the kinetics of ELFA precipitation in freshwater samples at levels of total plankton and single phytoplankton cells, and tested the suitability of ELFP for measurement of surface-bound algal extracellular phosphatases. Samples from acidic Plesné Lake (pH approximately 5; high phosphatase activity) and eutrophic Rímov reservoir (pH approximately 7-10; moderate phosphatase activity) were incubated with ELFP for 5-300 min, fixed with HgCl2 and filtered through polycarbonate filters. Relative fluorescence of filter-retained ELFA precipitates was quantified with image analysis. Time-courses of ELFA formation exhibited lag periods followed by finite periods of linear increase. In Plesné Lake, lag-times were shorter (1-18 min) and rates of increase in ELFA fluorescence higher (by approximately 2 orders of magnitude) than in Rímov reservoir (lag-times 30-200 min). Similar patterns of ELFA formation kinetics were also observed in Plesné Lake samples in cuvette spectrofluorometer measurements (which failed in Rímov reservoir). Linear regression of seasonal data on rates of increase in ELFA fluorescence from image cytometry and spectrofluorometry (r2 = 0.65, n = 10) allowed for calibration of image cytometry in terms of amount of cell-associated ELFA. Preliminary measurements of extracellular phosphatase activities of several algae resulted in rates (10-2260 fmol cell-1 h-1) which are comparable to data reported in the literature for algal cultures. 相似文献
124.
Carlos?Gonzalez-Rey Stefan?B.?Svenson Laila?M.?Eriksson Ivan?Ciznar Karel?KrovacekEmail author 《Polar Biology》2003,26(8):495-499
The occurrence of Plesiomonas shigelloides in fresh water from six lakes located north of the Polar Circle in the northern part of Sweden was investigated. Bacteriological analysis of the water samples revealed the presence of nine isolates of P. shigelloides from one of the six lakes. All nine isolates were tested for biochemical characterisation, and serological and genomic typing. The biochemical profiles of all nine isolates were identical. Two strains were non-agglutinating for the O and H antigens. The other seven displayed an O19 serotype, whereas H antigen showed non-agglutinating properties. The genotyping results showed that the O19 isolates presented the same pattern, while the two non-agglutinating strains presented patterns that were different to that of the seven others. The results show that P. shigelloides can occur in aquatic environments where the temperature conditions are extremely low for long periods. This could have ecological and clinical importance for the aquatic and terrestrial fauna at these latitudes. 相似文献
125.
Miroslav Vacek Marie Zarevúcka Zdeněk Wimmer Karel Stránský Kateřina Demnerová Marie-Dominique Legoy 《Biotechnology letters》2000,22(19):1565-1570
Selective enzymic esterification of free fatty acids, obtained from blackcurrant oil by chemical saponification, with n-butanol using four immobilized lipases under microwave irradiation and under classical heating was studied. A positive effect of microwave irradiation on chemical yields of the products of the enzymic reactions and specificity of lipases were observed in comparison with a controlled heating in an incubator equipped with shaking (classical heating) applied during the identical enzyme-mediated processes. The maximum quantity of -linolenic acid (30%) was obtained with Lipozyme used as biocatalyst of the reaction under microwave irradiation. The maximum quantity of butyl -linolenate (20%) was obtained by a Pseudomonas cepacia lipase catalyzed esterification under classical heating. 相似文献
126.
Inductively coupled plasma-mass spectrometry (ICP-MS) was used to determine the concentrations of 32 elements in the human liver and kidney and 20 elements in the bone, obtained from 70 autopsied dead individuals (54 males, 16 females) between 18 and 76 yr of age from the North Bohemia territory of the Czech Republic. Geometric means, median, minimal-maximal range, as well as distribution and correlation analysis were calculated. Some significant differences among tissue concentrations of trace elements of the women and men were found. In the liver, medians of the concentrations of some elements were higher for men than that for women (Al: 770 vs 610 microg/kg; As: 42 vs 27 microg/kg; Cd: 1800 vs 1390 microg/kg; Rb: 3955 vs 3210 microg/kg; V: 160 vs 105 microg/kg). On the contrary, the content of other elements for men was lower (Bi: 0.8 vs 3.2 microg/kg; Cr: 57 vs 72 microg/kg; Hg: 228 vs 325 microg/kg; Zn: 57.1 vs 68.5 mg/kg). In the kidney of men, there were higher contents of Al (360 vs 245 microg/kg) and Hg (135 vs 75 microg/kg) and lower contents of Zn (47.7 vs 59.7 mg/kg) and I (135 vs 220 microg/kg) than those of women. In the case of bone, the concentrations of Cu and Rb were higher for men (1410 microg Cu/kg and 405 microg Rb/kg, respectively) than for women (655 microg Cu/kg and 285 microg Rb/kg, respectively). On the contrary, the content of Mn was considerably lower for men (110 microg Mn/kg) than for women (215 microg Mn/kg). 相似文献
127.
Intracellular Glucose Concentration in Derepressed Yeast Cells Consuming Glucose Is High Enough To Reduce the Glucose Transport Rate by 50% 下载免费PDF全文
Bas Teusink Jasper A. Diderich Hans V. Westerhoff Karel van Dam Michael C. Walsh 《Journal of bacteriology》1998,180(3):556-562
In Saccharomyces cerevisiae cells exhibiting high-affinity glucose transport, the glucose consumption rate at extracellular concentrations above 10 mM was only half of the zero trans-influx rate. To determine if this regulation of glucose transport might be a consequence of intracellular free glucose we developed a new method to measure intracellular glucose concentrations in cells metabolizing glucose, which compares glucose stereoisomers to correct for adhering glucose. The intracellular glucose concentration was 1.5 mM, much higher than in most earlier reports. We show that for the simplest model of a glucose carrier, this concentration is sufficient to reduce the glucose influx by 50%. We conclude that intracellular glucose is the most likely candidate for the observed regulation of glucose import and hence glycolysis. We discuss the possibility that intracellular glucose functions as a primary signal molecule in these cells. 相似文献
128.
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130.
The response of a nematode community to a decreasing organic matter loading was studied. Monthly observations were made at three stations at an intertidal brackish-water mudflat in the Ems estuary in 1980 (highly polluted), 1987 (moderately polluted) and 1993 (no significant pollution). Nematodes were identified and counted in the upper 1 cm of the sediment.The decrease of organic pollution was followed by an increase in species diversity, whereas numerical densities decreased. Diatom eating nematodes, being dominant under eutrophic conditions in 1980, decreased strongly, partly as a consequence of decreasing diatom standing stock. Eudiplogaster pararmatus, an indicator of organic enrichment, decreased strongly to disappear completely in 1993. Bonger's maturity index was used to describe the response of the nematode community. At 2 most polluted stations a strong response was observed from 1980 to 1987: a decrease of colonizer species. After 1987, although persister species increased, no further development towards a more natural succession type community occurred, probably due to the natural stress of the habitat (high mudflat, low salinities). 相似文献