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1.
Occurrence of Fumonisin B<Subscript>1</Subscript> in Corn from the Main Corn-Producing Areas of China 总被引:1,自引:0,他引:1
Fumonisin B1 (FB1) is the most abundant of the fumonisin mycotoxins, mainly produced in maize by F. verticillioides and F. proliferatum. A total of 282 corn samples harvested in 2005 from six provinces, the main corn-producing areas of China, were analyzed
for FB1 using high-performance liquid chromatography. All samples except one were (99.6%) positive for FB1 at levels varying from 3 to 71,121 ng/g with mean and median levels for all samples of 6,662 and 1,569 ng/g, respectively.
During an analysis of the distribution pattern for FB1, it became apparent that 43.6% of tested samples had FB1 concentrations below 1,000 ng/g, while 25.2% contained in excess of 5,000 ng/g. The average exposure to FB1 (1.1 μg/kg body weight/day) is within the provisional maximum tolerable daily intake of 2 μg/kg body weight/day set by the
Joint FAO/WHO Expert Committee on Food Additives. 相似文献
2.
Fumonisin production by <Emphasis Type="Italic">Fusarium</Emphasis> species isolated from freshly harvested corn in Iran 总被引:1,自引:0,他引:1
Ghiasian SA Rezayat SM Kord-Bacheh P Maghsood AH Yazdanpanah H Shephard GS van der Westhuizen L Vismer HF Marasas WF 《Mycopathologia》2005,159(1):31-40
Fifty-one strains of Fusarium verticillioides and F. proliferatum isolated from corn collected from four different geographic areas in Iran, namely Fars, Khuzestan, Kermanshah and Mazandaran (an endemic oesophageal cancer (OC) area) were evaluated for their ability to produce fumonisins B1 (FB1), B2 (FB2) and B3 (FB3) in corn culture. Fumonisin levels were determined by high-performance liquid chromatography. All tested strains of F. verticillioides and F. proliferatumproduced fumonisins within a wide range of concentrations, 197–9661 g/g, 18–1974 g/g, and 21–1725 g/g for FB1, FB2, and FB3, respectively. The highest mean concentrations of FB1, FB2, and FB3 were 3897, 806 and 827 g/g, respectively. Overall, 61% of the F. verticillioides and F. proliferatum strains produced higher levels of FB3 than FB2. The mean ratios of FB1:FB2, FB1:FB3 and FB1:total fumonisins were 8, 7 and 0.7 for F. verticillioides and 5.7, 10.7 and 0.7 for F. proliferatum, respectively. Significant differences in some of the meteorological data (rainfall, relative humidity and minimum temperature) from the four provinces were observed. Fumonisin levels produced by F. verticillioides strains isolated from Khuzestan province (tropical zone) were significantly (P < 0.01) higher than the other three provinces. This is the first report of the fumonisin-producing ability of F.verticillioides and F. proliferatum strains isolated from corn harvested from different geographic areas in Iran. 相似文献
3.
Gutiérrez-Nájera N Muñoz-Clares RA Palacios-Bahena S Ramírez J Sánchez-Nieto S Plasencia J Gavilanes-Ruíz M 《Planta》2005,221(4):589-596
Fumonisin B1 (FB1) is an amphipathic toxin produced by the pathogenic fungus Fusarium verticillioides which causes stem, root and ear rot in maize (Zea mays L.). In this work, we studied the action of FB1 on the plasma membrane H+-ATPase (EC 3.6.1.34) from germinating maize embryos, and on the fluidity and lipid peroxidation of these membranes. In maize embryos the toxin at 40 M inhibited root elongation by 50% and at 30 M decreased medium acidification by about 80%. Irrespective of the presence and absence of FB1, the H+-ATPase in plasma membrane vesicles exhibited non-hyperbolic saturation kinetics by ATPH-Mg, with Hill number of 0.67. Initial velocity studies revealed that FB1 is a total uncompetitive inhibitor of this enzyme with an inhibition constant value of 17.5±1 M. Thus FB1 decreased Vmax and increased the apparent affinity of the enzyme for ATP-Mg to the same extent. Although FB1 increased the fluidity at the hydrophobic region of the membrane, no correlation was found with its effect on enzyme activity, since both effects showed different FB1-concentration dependence. Peroxidation of membrane lipids was not affected by the toxin. Our results suggest that, under in vivo conditions, the plasma membrane H+-ATPase is a potentially important target of the toxin, as it is inhibited not only by FB1 but also by its structural analogs, the sphingoid intermediates, which accumulate upon the inhibition of sphinganine N-acyltransferase by this toxin. 相似文献
4.
Low levels of fumonisins have been found frequently in corn based breakfast cereals and can occur bound to protein and other
matrix components.In vitro digestion of two samples of corn flakes was carried out under "fed conditions." Fumonisins were measured as o-phthaldialdehyde/mercaptoethanol
derivatives by LC-fluorescence. One sample of corn flakes (FN12) had high concentrations of fumonisin B1 (FB) (average 125 ng/g) and total bound FB1, (TB FB1) (average 92 ng/g) and the other (FN11) had a low level of free FB1 (average 29 ng/g) and no detectable TB FB1. After incubation of the samples with gastrointestinal tract solutions simulating saliva plus stomach and duodenal juices,
chyme was analysed for FB1, hydrolyzed FB1 (HFB1) and partially hydrolyzed fumonisin B1 (PHFB1). The bioaccessibility (percentage of FB1 released from corn flakes into chyme) was 38-78% for incurred FB1 in FN12, 8-54% for incurred plus spiked FB1 in FN12, and 19-66% for incurred plus spiked FB1 in FN11. HFB1 and PHFB1 were not detected. If free FB1 was first extracted from sample FN12, no FB1 was detected in the chyme, indicating no contribution from TB FB1. Concentrations were corrected for method recovery of FB1 or, for bound FB1, partial method recovery of HFB1
Presented at the XIIth IUPAC International Symposium on Mycotoxins and Phycotoxins, Istanbul, Turkey, 21–25 May, 2007 相似文献
5.
Fusarium verticillioides is the most important seed transmitted pathogen that infects maize. It produces fumonisins, toxins that have potential toxicity for humans and animals. Control of F. verticillioides colonisation and systemic contamination of maize has become a priority area in food safety research. The aims of this research were (1) to characterise the maize endorhizosphere and rhizoplane inhabitant bacteria and Fusarium spp., (2) to select bacterial strains with impact on F. verticillioides growth and fumonisin B1 production in vitro, (3) to examine the effects of bacterial inoculum levels on F. verticillioides root colonisation under greenhouse conditions. Arthrobacter spp. and Azotobacter spp. were the predominant genera isolated from maize endorhizosphere and rhizoplane at the first sampling period, whilst F. verticillioides strains showed the greatest counts at the same isolation period. All F. verticillioides strains were able to produce fumonisin B1 in maize cultures. Arthrobacter globiformis RC5 and Azotobacter armeniacus RC2, used alone or in a mix, demonstrated important effects on F. verticillioides growth and fumonisin B1 suppression in vitro. Only Azotobacter armeniacus RC2 significantly reduced the F. verticillioides root colonisation at 106 and 107 CFU g–1 levels under greenhouse conditions. 相似文献
6.
In Escherichia coli, the F1FO ATP synthase b subunits house a conserved arginine in the tether domain at position 36 where the subunit emerges from the membrane. Previous
experiments showed that substitution of isoleucine or glutamate result in a loss of enzyme activity. Double mutants have been
constructed in an attempt to achieve an intragenic suppressor of the b
arg36→ile and the b
arg36→glu mutations. The b
arg36→ile mutation could not be suppressed. In contrast, the phenotypic defect resulting from the b
arg36→glu mutation was largely suppressed in the b
arg36→glu,glu39→arg double mutant. E. coli expressing the b
arg36→glu,glu39→arg subunit grew well on succinate-based medium. F1FO ATP synthase complexes were more efficiently assembled and ATP driven proton pumping activity was improved. The evidence
suggests that efficient coupling in F1FO ATP synthase is dependent upon a basic amino acid located at the base of the peripheral stalk. 相似文献
7.
Many bacteria adapt to microoxic conditions by synthesizing a particular cytochrome c oxidase (cbb
3) complex with a high affinity for O2, encoded by the ccoNOQP operon. A survey of genome databases indicates that ccoNOQP sequences are widespread in all sub-branches of Proteobacteria but otherwise are found only in bacteria of the CFB group (Cytophaga, Flexibacter, Bacteroides). Our analysis of available genome sequences suggests four major strategies of regulating ccoNOQP expression in response to O2. The most widespread strategy involves direct regulation by the O2-responsive protein Fnr. The second strategy involves an O2-insensitive paralogue of Fnr, FixK, whose expression is regulated by the O2-responding FixLJ two-component system. A third strategy of mixed regulation operates in bacteria carrying both fnr and fixLJ-fixK genes. Another, not yet identified, strategy is likely to operate in the -Proteobacteria Helicobacter pylori and Campylobacter jejuni which lack fnr and fixLJ-fixK genes. The FixLJ strategy appears specific for the -subclass of Proteobacteria but is not restricted to rhizobia in which it was originally discovered. 相似文献
8.
This study examined the effects of season-long exposure of Chinese pine (Pinus tabulaeformis) to elevated carbon dioxide (CO2) and/or ozone (O3) on indole-3-acetic acid (IAA) content, activities of IAA oxidase (IAAO) and peroxidase (POD) in needles. Trees grown in
open-top chambers (OTC) were exposed to control (ambient O3, 55 nmol mol−1 + ambient CO2, 350 μmol mol−1, CK), elevated CO2 (ambient O3 + high CO2, 700 μmol mol−1, EC) and elevated O3 (high O3, 80 ± 8 nmol mol−1 + ambient CO2, EO) OTCs from 1 June to 30 September. Plants grown in elevated CO2 OTC had a growth increase of axial shoot and needle length, compared to control, by 20% and 10% respectively, while the growth
in elevated O3 OTC was 43% and 7% less respectively, than control. An increase in IAA content and POD activity and decrease in IAAO activity
were observed in trees exposed to elevated CO2 concentration compared with control. Elevated O3 decreased IAA content and had no significant effect on IAAO activity, but significantly increased POD activity. When trees
pre-exposed to elevated CO2 were transferred to elevated O3 (EC–EO) or trees pre-exposed to elevated O3 were transferred to elevated CO2 (EO–EC), IAA content was lower while IAAO activity was higher than that transferred to CK (EC–CK or EO–CK), the change in
IAA content was also related to IAAO activity. The results indicated that IAAO and POD activities in Chinese pine needles
may be affected by the changes in the atmospheric environment, resulting in the change of IAA metabolism which in turn may
cause changes in Chinese pine’s growth.
An erratum to this article can be found at 相似文献
9.
The histochemical and cytochemical localization of abscisic acid (ABA)-induced H2O2 production in leaves of maize (Zea mays L.) plants were examined, using 3,3-diaminobenzidine (DAB) and CeCl3 staining, respectively, and the relationship between ABA-induced H2O2 production and ABA-induced subcellular activities of antioxidant enzymes was studied. H2O2 generated in response to ABA treatment was detected within 0.5 h in major veins of the leaves and maximized at about 2–4 h. In mesophyll and bundle sheath cells, ABA-induced H2O2 accumulation was observed only in apoplast, and the greatest accumulation occurred in the walls of mesophyll cells facing large intercellular spaces. Meanwhile, ABA treatment led to a significant increase in the activities of the leaf chloroplastic and cytosolic antioxidant enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR), and pretreatment with the NADPH oxidase inhibitor diphenyleneiodonium (DPI), the O
2
−
scavenger Tiron and the H2O2 scavenger dimethylthiourea (DMTU) almost completely arrested the increase in the activities of these antioxidant enzymes. Our results indicate that the accumulation of apoplastic H2O2 is involved in the induction of the chloroplastic and cytosolic antioxidant enzymes. Moreover, an oxidative stress induced by paraquat (PQ), which generates O
2
−
and then H2O2 in chloroplasts, also up-regulated the activities of the chloroplastic and cytosolic antioxidant enzymes, and the up-regulation was blocked by the pretreatment with Tiron and DMTU. These data suggest that H2O2 produced at a specific cellular site could coordinate the activities of antioxidant enzymes in different subcellular compartments. 相似文献
10.
Jurjevic Z Wilson DM Wilson JP Geiser DM Juba JH Mubatanhema W Widstrom NW Rains GC 《Mycopathologia》2005,159(3):401-406
This study was designed to identify and compare the Fusarium species of the Gibberella fujikuroi complex on pearl millet (Pennisetum glaucum (L.) R. Br) and corn (Zea mays L.) crops grown in southern Georgia, and to determine their influence on potential fumonisin production. Pearl millet and corn samples were collected in Georgia in 1996, 1997 and 1998. Three percent of the pearl millet seeds had fungi similar to the Fusarium species of the G. fujikuroi species complex. One hundred and nineteen representative isolates visually similar to the G. fujikuroi species complex from pearl millet were paired with mating population A (Fusarium verticillioides (Sacc.) Nirenberg), mating population D (F. proliferatum (Matsushima) Nirenberg) and mating population F (F. thapsinum (Klittich, Leslie, Nelson and Marasas) tester strains. Successful crosses were obtained with 50.4%, 10.1% and 0.0% of these isolates with the A, D and F tester strains, while 39.5 of the isolates did not form perithecia with any tester strains. Two of the typical infertile isolates were characterized by DNA sequence comparisons and were identified as Fusarium pseudonygamai (Nirenberg and ODonnell), which is the first known isolation of this species in the United States. Based on the pattern of cross-compatibility, conidiogenesis, colony characteristics and media pigmentation, a majority of the infertile isolates belong to this species. Fumonisins FB1 and FB2 were not detected in any of the 81 pearl millet samples analyzed. The species of the G. fujikuroi species complex were dominant in corn and were isolated from 84%, 74% and 65% of the seed in 1996, 1997 and 1998, respectively. Representative species of the G. fujikuroi species complex were isolated from 1996 to 1998 Georgia corn survey (162, 104 and 111 isolates, respectively) and tested for mating compatibility. The incidence of isolates belonging to mating population A (F. verticillioides) ranged from 70.2% to 89.5%. Corn survey samples were assayed for fumonisins, and 63% to 91% of the 1996, 1997 and 1998 samples were contaminated. The total amount of fumonisins in the corn samples ranged from 0.6 to 33.3 g/g. 相似文献
11.
A higher Coenzyme Q10 (CoQ10) concentration of 25.04 mg/l was found in airlift bioreactor than the value of 18.11 mg/l obtained in stirred tank under
the aerobic-dark cultivation of Rhodobacter sphaeroides. Aeration rate didn’t show obvious impact to CoQ10 production in airlift bioreactor. The fed-batch operation in airlift bioreactor could increase the biomass concentration
and led to the maximum CoQ10 concentration of 33.91 mg/l measured, but a lower CoQ10 cell content (3.5 mg CoQ10/DCW) was observed in the fed-batch operation as compared to the batch operation. To enhance the CoQ10 content, an aeration-change strategy was proposed in the fed-batch operation of airlift bioreactor. This strategy led to
the maximum CoQ10 concentration of 45.65 mg/l, a 35% increase as compared to the simple fed-batch operation. The results of this study suggested
that a fed-batch operation in airlift bioreactor accompanying aeration-change could be suitable for CoQ10 production. 相似文献
12.
Chen GT Yang M Song Y Lu ZQ Zhang JQ Huang HL Wu LJ Guo DA 《Applied microbiology and biotechnology》2008,77(6):1345-1350
Preparative-scale fermentation of ginsenoside Rb1 (1) with Acremonium strictum AS 3.2058 gave three new compounds, 12β-hydroxydammar-3-one-20 (S)-O-β-d-glucopyranoside (7), 12β, 25-dihydroxydammar-(E)-20(22)-ene-3-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside (8), and 12β, 20 (R), 25-trihydroxydammar-3-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside (9), along with five known compounds, ginsenoside Rd (2), gypenoside XVII (3), ginsenoside Rg3 (4), ginsenoside F2 (5), and compound K (6). The structural elucidation of these metabolites was based primarily on one- and two-dimensional nuclear magnetic resonance
and high-resolution electron spray ionization mass spectra analyses. Among these compounds, 2–6 are also the metabolites of ginsenoside Rb1 in mammals. This result demonstrated that microbial culture parallels mammalian metabolism; therefore, A. strictum might be a useful tool for generating mammalian metabolites of related analogs of ginsenosides for complete structural identification
and for further use in pharmaceutical research in this series of compounds. In addition, the biotransformation kinetics was
also investigated. 相似文献
13.
The increasing CO2 concentration in Earths atmosphere is expected to cause a greater decline in the nutritional quality of C3 than C4 plants. As a compensatory response, herbivorous insects may increase their feeding disproportionately on C3 plants. These hypotheses were tested by growing the grasses Lolium multiflorum C3) and Bouteloua curtipendula C4) at ambient (370 ppm) and elevated (740 ppm) CO2 levels in open top chambers in the field, and comparing the growth and digestive efficiencies of the generalist grasshopper Melanoplus sanguinipes on each of the four plant × CO2 treatment combinations. As expected, the nutritional quality of the C3 grass declined to a greater extent than did that of the C4 grass at elevated CO2; protein levels declined in the C3 grass, while levels of carbohydrates (sugar, fructan and starch) increased. However, M. sanguinipes did not significantly increase its consumption rate to compensate for the lower nutritional quality of the C3 grass grown under elevated CO2. Instead, these grasshoppers appear to use post-ingestive mechanisms to maintain their growth rates on the C3 grass under elevated CO2. Consumption rates of the C3 and C4 grasses were also similar, demonstrating a lack of compensatory feeding on the C4 grass. We also examined the relative efficiencies of nutrient utilization from a C3 and C4 grass by M. sanguinipes to test the basis for the C4 plant avoidance hypothesis. Contrary to this hypothesis, neither protein nor sugar was digested with a lower efficiency from the C4 grass than from the C3 grass. A novel finding of this study is that fructan, a potentially large carbohydrate source in C3 grasses, is utilized by grasshoppers. Based on the higher nutrient levels in the C3 grass and the better growth performance of M. sanguinipes on this grass at both CO2 levels, we conclude that C3 grasses are likely to remain better host plants than C4 grasses in future CO2 conditions. 相似文献
14.
15.
Smirnova IA Zaslavsky D Fee JA Gennis RB Brzezinski P 《Journal of bioenergetics and biomembranes》2008,40(4):281-287
The ba
3-type cytochrome c oxidase from Thermus thermophilus is phylogenetically very distant from the aa
3–type cytochrome c oxidases. Nevertheless, both types of oxidases have the same number of redox-active metal sites and the reduction of O2 to water is catalysed at a haem a
3-CuB catalytic site. The three-dimensional structure of the ba
3 oxidase reveals three possible proton-conducting pathways showing very low homology compared to those of the mitochondrial,
Rhodobacter sphaeroides and Paracoccus denitrificans aa
3 oxidases. In this study we investigated the oxidative part of the catalytic cycle of the ba
3
-cytochrome c oxidase using the flow-flash method. After flash-induced dissociation of CO from the fully reduced enzyme in the presence
of oxygen we observed rapid oxidation of cytochrome b (k ≅ 6.8 × 104 s−1) and formation of the peroxy (PR) intermediate. In the next step a proton was taken up from solution with a rate constant of ~1.7 × 104 s−1, associated with formation of the ferryl (F) intermediate, simultaneous with transient reduction of haem b. Finally, the enzyme was oxidized with a rate constant of ~1,100 s−1, accompanied by additional proton uptake. The total proton uptake stoichiometry in the oxidative part of the catalytic cycle
was ~1.5 protons per enzyme molecule. The results support the earlier proposal that the PR and F intermediate spectra are similar (Siletsky et al. Biochim Biophys Acta 1767:138, 2007) and show that even though the architecture of the proton-conducting pathways is different in the ba
3 oxidases, the proton-uptake reactions occur over the same time scales as in the aa
3-type oxidases.
Smirnova and Zaslavsky contributed equally to the work described in this paper. 相似文献
16.
Bhatt D Cole SP Grabar TB Claggett SB Cain BD 《Journal of bioenergetics and biomembranes》2005,37(2):67-74
The peripheral stalk of F1F0 ATP synthase is composed of a parallel homodimer of b subunits that extends across the cytoplasmic membrane in F0 to the top of the F1 sector. The stalk serves as the stator necessary for holding F1 against movement of the rotor. A series of insertions and deletions have been engineered into the hydrophilic domain that interacts with F1. Only the hydrophobic segment from {val-121} to {ala-132} and the extreme carboxyl terminus proved to be highly sensitive to mutation. Deletions in either site apparently abolished enzyme function as a result of defects is assembly of the F1F0 complex. Other mutations manipulating the length of the sequence between these two areas had only limited effects on enzyme function. Expression of a b subunit with insertions with as few as two amino acids into the hydrophobic segment also resulted in loss of F1F0 ATP synthase. However, a fully defective b subunit with seven additional amino acids could be stabilized in a heterodimeric peripheral stalk within a functional F1F0 complex by a normal b subunit. 相似文献
17.
Miriam G. Etcheverry Andrea Scandolara Andrea Nesci Marta Sofia Vilas Boas Ribeiro Paola Pereira Paola Battilani 《Mycopathologia》2009,167(5):287-295
Biological control represent an alternative to the use of pesticides in crop protection. A key to progress in biological control
to protect maize against Fusarium verticillioides and Aspergillus flavus maize pathogens are, to select in vitro, the best agent to be applied in the field. The aim of this study was to examine
the antagonistic activity of bacterial and yeast isolates against F.verticillioides and A. flavus toxigenic strains. The first study showed the impact of Bacillus amyloliquefaciens BA-S13, Microbacterium oleovorans DMS 16091, Enterobacter hormomaechei EM-562T, and Kluyveromyces spp. L14 and L16 isolates on mycelial growth of two strains of A. flavus MPVPA 2092, 2094 and three strains of F. verticillioides MPVPA 285, 289, and 294 on 3% maize meal extract agar at different water activities (0.99, 0.97, 0.95, and 0.93). From this
first assay antagonistics isolates M. oleovorans, B. amyloliquefaciens and Kluyveromyces sp. (L16) produced an increase of lag phase of growth and decreased a growth rate of all fungal strains. These isolates were
selected for futher studies. In vitro non-rhizospheric maize soil (centrally and sprayed inoculated) and in vitro maize (ears
apex and base inoculated) were treated with antagonistics and pathogenic strains alone in co-inoculated cultures. Bacillus amyloliquefaciens significantly reduced F. verticillioides and A. flavus count in maize soil inoculated centrally. Kluyveromyces sp. L16 reduced F. verticillioides and A. flavus count in maize soil inoculated by spray. Kluyveromyces sp. L16 was the most effective treatment limiting percent infections by F. verticillioides on the maize ears. 相似文献
18.
Effects of exogenous H2O2 application on vinblastine (VBL) and its precursors, vindoline (VIN), catharanthine (CAT) and α-3′,4′-anhydrovinblastine
(AVBL), were measured in Catharanthus roseus seedlings in order to explore possible correlation of VBL formation with oxidative stress. VBL accumulation has previously
been shown to be regulated by an in vitro H2O2-dependent peroxidase (POD)-like synthase. Experimental exposure of plants to different concentrations of H2O2 showed that endogenous H2O2 and alkaloid concentrations in leaves were positively elevated. The time-course variations of alkaloid concentrations and
redox state, reflected by the concentrations of H2O2, ascorbic acid (AA), oxidative product of glutathione (GSSG) and POD activity, were significantly altered due to H2O2 application. The further correlation analysis between alkaloids and redox status indicated that VBL production was tightly
correlated with redox status. These results provide a new link between VBL metabolisms and redox state in C. roseus. 相似文献
19.
Parodi TV Cunha MA Heldwein CG de Souza DM Martins ÁC Garcia Lde O Wasielesky W Monserrat JM Schmidt D Caron BO Heinzmann B Baldisserotto B 《Comparative biochemistry and physiology. Toxicology & pharmacology : CBP》2012,155(3):462-468
The aim of this study was to evaluate the anesthesia induction and recovery times of sub-adult and post-larvae white shrimp (Litopenaeus vannamei) that were treated with eugenol and the essential oils (EOs) from Lippia alba and Aloysia triphylla. Oxidative stress parameters in the hemolymph of this species were also analyzed. The concentrations of eugenol, A. triphylla EO and L. alba EO recommended for anesthesia were 200, 300 and 750 μL L(-1) for sub-adults and 175, 300 and 500 μL L(-1) for post-larvae, respectively. The concentrations studied during the transport of sub-adults were between 20 and 50 μL L(-1) eugenol, 20-30 μL L(-1)A. triphylla EO and 50 μL L(-1)L. alba EO. For post-larvae, the optimal concentrations for transport were 20 μL L(-1) eugenol and between 20 and 50 μL L(-1)A. triphylla EO. The white shrimp sub-adults that were exposed to A. triphylla EO (20 μL L(-1)) showed increases in their total antioxidant capacities (150%), catalase (70%) and glutathione-S-transferase (615%) activity after 6 h. L. alba EO (50 μL L(-1)) and eugenol (20 μL L(-1)) also increased GST activity (1292 and 1315%) after 6 h, and eugenol (20 μL L(-1)) decreased the total antioxidant capacity (100%). Moreover, concentrations above 30 μL L(-1) for the EOs of A. triphylla and L. alba and 20 μL L(-1) eugenol were effective at inducing anesthesia and improving the antioxidant system against reactive oxygen species (ROS) after 6 h. 相似文献
20.
Vassalle M 《Journal of biomedical science》2007,14(6):699-716
Summary The mechanisms underlying the pacemaker current in cardiac tissues is not agreed upon. The pacemaker potential in Purkinje
fibers has been attributed to the decay of the potassium current I
Kdd. An alternative proposal is that the hyperpolarization-activated current I
f underlies the pacemaker potential in all cardiac pacemakers. The aim of this review is to retrace the experimental development
related to the pacemaker mechanism in Purkinje fibers with reference to findings about the pacemaker mechanism in the SAN
as warranted. Experimental data and their interpretation are critically reviewed. Major findings were attributed to K+ depletion in narrow extracellular spaces which would result in a time dependent decay of the inward rectifier current I
K1. In turn, this decay would be responsible for a “fake” reversal of the pacemaker current. In order to avoid such a postulated
depletion, Ba2+ was used to block the decay of I
K1. In the presence of Ba2+ the time-dependent current no longer reversed and instead increased with time and more so at potentials as negative as −120 mV.
In this regard, the distinct possibility needs to be considered that Ba2+ had blocked I
Kdd (and not only I
K1). That indeed this was the case was demonstrated by studying single Purkinje cells in the absence and in the presence of
Ba2+. In the absence of Ba2+, I
Kdd was present in the pacemaker potential range and reversed at E
K. In the presence of Ba2+, I
Kdd was blocked and I
f appeared at potentials negative to the pacemaker range. The pacemaker potential behaves in a manner consistent with the underlying
I
Kdd but not with I
f. The fact that I
f is activated on hyperpolarization at potential negative to the pacemaker range makes it suitable as a safety factor to prevent
the inhibitory action of more negative potentials on pacemaker discharge. It is concluded that the large body of evidence
reviewed proves the pacemaker role of I
Kdd (but not of I
f) in Purkinje fibers. 相似文献