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Detoxification of ochratoxin A can be achieved by chemical or enzymatic hydrolyzation, the products of such reactions are ochratoxin α and phenylalanine. Ochratoxin α like ochratoxin A, is a fluorescing molecule, therefore sensitive analysis is possible at very low concentration levels. Methods have been established that make it possible to look for residues of ochratoxin A and its main metabolite ochratoxin α in blood and tissues at very low concentration levels. Plasma is extracted by the use of small amounts of chloroform; the extract is cleaned with water and afterwards evaporated to dryness]. The residue is re-dissolved and analysed by HPLC-FLD. Using this method a limit of detection of 0.5μg/l for both ochratoxin A and ochratoxin α can be reached. 相似文献
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66.
Endogenous chloride channels of insect sf9 cells. Evidence for coordinated activity of small elementary channel units 总被引:1,自引:0,他引:1
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EH Larsen SE Gabriei MJ Stutts J Fullton EM Price RC Boucher 《The Journal of general physiology》1996,107(6):695-714
The endogenous Cl- conductance of Spodoptera frugiperda (Sf9) cells was studied 20-35 h after plating out of either uninfected cells or cells infected by a baculovirus vector carrying the cloned beta-galactosidase gene (beta-Gal cells). With the cation Tris+ in the pipette and Na+ in the bath, the reversal potential of whole-cell currents was governed by the prevailing Cl- equilibrium potential and could be fitted by the Goldman-Hodgkin-Katz equation with similar permeabilities for uninfected and beta-Gal cells. In the frequency range 0.12 < f < 300 Hz, the power density spectrum of whole-cell Cl- currents could be fitted by three Lorentzians. Independent of membrane potential, >50% of the total variance of whole-cell current fluctuations was accounted for by the low frequency Lorentzian (fc = 0.40 +/- 0.03 Hz, n = 6). Single-Cl- channels showed complex gating kinetics with long lasting (seconds) openings interrupted by similar long closures. In the open state, channels exhibited fast burst-like closures. Since the patches normally contained more than a single channel, it was not possible to measure open and closed dwell-time distributions for comparing single-Cl- channel activity with the kinetic features of whole-cell currents. However, the power density spectrum of Cl- currents of cell-attached and excised outside-out patches contained both high and low frequency Lorentzian components, with the corner frequency of the slow component (fc = 0.40 +/- 0.02 Hz, n = 4) similar to that of whole-cell current fluctuations. Chloride channels exhibited multiple conductance states with similar Goldman-Hodgkin-Katz-type rectification. Single-channel permeabilities covered the range from approximately 0.6.10(-14) cm5/s to approximately 6.10(-14) cm3/s, corresponding to a limiting conductance (gamma 150/150) of approximately 3.5 pS and approximately 35 pS, respectively. All states reversed near the same membrane potential, and they exhibited similar halide ion selectivity, P1 > PCl approximately PBr. Accordingly, Cl- current amplitudes larger than current flow through the smallest channel unit resolved seem to result from simultaneous open/shut events of two or more channel units. 相似文献
67.
A change in twist of actin provides the force for the extension of the acrosomal process in limulus sperm: the false-discharge reaction 总被引:6,自引:5,他引:1
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One of the most spectacular motions is the generation of the acrosomal process in the limulus sperm. On contact with the egg, the sperm generates a 60-mum-long process that literally drills its way through the jelly surrounding the egg. This irresversible reaction takes only a few seconds. We suggested earlier that this motion is driven by a change in twist of the actin filaments comprising the acrosomal process. In this paper we analyze the so-called false discharge, a reversible reaction, in which the acrosomal filament bundle extends laterally from the base of the sperm and not anteriorly from the apex. Unlike the true discharge, which is straight, the false discharge is helical. Before extension, the filament bundle is coiled about the base of the sperm. In the coil, the bundle is not smoothly bent but consists of arms (straight segments) and elbows (corners) so that the coil looks like a 14-sided polygon. The extension of the false discharge works as follows: starting at the base of the bundle, the filaments change their twist which concomitantly changes the orientations of the elbows relative to each other; that is, in the coil, the elbows all like in a common plane, but after the change in twist, the plane of each elbow is rotated to be perpendicular to that of its neighbors. This change transforms the bundle from a compact coil into an extended left- handed helix. Because the basal end of the bundle is unconstrained, the extension is lateral. The true discharge works the same way but starts at the apical end of the bundle. The apical end, however, is constrained by its passage through the nuclear canal, which directs the extention anteriorly. Unlike the false discharge, during the true discharge the elbows are melted out, making the reaction irreversible. This study shows that rapid movement can be regenerated by actin without myosin and gives us insight into the molecular mechanism. 相似文献
68.
EM Armstrong 《BMJ (Clinical research ed.)》1996,312(7042):1320.2
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Andrzej Kalisz Robert Pokluda Aleš Jezdinský Agnieszka Sękara Aneta Grabowska Joanna Gil Jarmila Neugebauerová 《Acta Physiologiae Plantarum》2016,38(8):196
Six cultivars of basil, ‘Genovese’, ‘Purpurascens’, ‘Cinnamon’, ‘Crispum’, ‘Citriodora’, and ‘Siam Queen’, at the age of 8 weeks, were subjected to low temperature (6 °C for 8 days) or 18 °C (control). Content of hydrogen peroxide (H2O2), malondialdehyde (MDA), total phenolics, and l-ascorbic acid were assessed in basil leaves after low temperature exposure. Activity of peroxidase (POD), and catalase (CAT) enzymes and 2,2-diphenyl-1-picrylhydrazyl (DPPH·) radical scavenging activity were also determined. The greatest increase in H2O2 was observed for lettuce leaf basil, by 104 % in comparison to the control, while most noticeable increase in the content of MDA was noted for lemon basil (by 77 %). Chilling treatment resulted in higher POD activity in two cultivars: Thai and green basil, changes in CAT activity was negligible for almost all tested genotypes, with an exception of Thai basil, for which activity of this enzyme dropped. Chilling induced the increase of l-ascorbic acid in most tested basil cultivars, but total phenolic content increased significantly only in lettuce leaf basil. Higher ability in scavenging free radicals was shown in basil treated with 6 °C, especially the red basil cultivar. For this genotype, DPPH· radical scavenging activity was the highest among tested cultivars and was parallel to the highest content of phenolics. The results indicated overproduction of H2O2, deterioration of membrane integrity, and activation of enzymatic and/or non-enzymatic defence mechanisms in basil with an evidence of genotypic variation as the response to low temperature. 相似文献
70.
Structure and regulation of the anthranilate synthase genes in Pseudomonas aeruginosa: II. Cloning and expression in Escherichia coli 总被引:7,自引:0,他引:7
Crawford IP; Wilde A; Yelverton EM; Figurski D; Hedges RW 《Molecular biology and evolution》1986,3(5):449-458
The genes for the large and small subunits of anthranilate synthase (trpE
and trpG, respectively) have been cloned from Pseudomonas aeruginosa PAC174
into E. coli by R-prime formation with the broad-host- range plasmid
R68.44. Sequential subcloning into plasmid vectors reduced the active
Pseudomonas DNA fragment to a length of 3.1 kb. We obtained evidence that
this region contains the promoter for its own expression and retains a
vestigial regulatory response to tryptophan scarcity or excess.
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