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1.
The actions of the neonicotinoid imidacloprid on cholinergic neurons of Drosophila melanogaster 总被引:2,自引:0,他引:2
The neonicotinoid insecticide imidacloprid is an agonist on insect nicotinic acetylcholine receptors (nAChRs). We utilised
fura-2-based calcium imaging to investigate the actions of imidacloprid on cultured GFP-tagged cholinergic neurons from the
third instar larvae of the genetic model organism Drosophila melanogaster. We demonstrate dose-dependent increases in intracellular calcium ([Ca2+]i) in cholinergic neurons upon application of imidacloprid (10 nM–100 μM) that are blocked by nAChR antagonists mecamylamine
(10 μM) and α-bungarotoxin (α-BTX, 1 μM). When compared to other (untagged) neurons, cholinergic neurons respond to lower
concentrations of imidacloprid (10–100 nM) and exhibit larger amplitude responses to higher (1–100 μM) concentrations of imidacloprid.
Although imidacloprid acts via nAChRs, increases in [Ca2+]i also involve voltage-gated calcium channels (VGCCs) in both groups of neurons. Thus, we demonstrate that cholinergic neurons
express nAChRs that are highly sensitive to imidacloprid, and demonstrate a role for VGCCs in amplifying imidacloprid-induced
increases in [Ca2+]i. 相似文献
2.
The effect of low doses of UV-A (320–400 nm) and UV-B (280–320 nm) radiation on photosynthetic activities inPhaseolus mungo L. was investigated under field condition. Supplementation of UV-A enhanced the synthesis of chlorophyll and carotenoids
than the UV-B supplemented plants. Significant increase was seen in the concentration of UV-B absorbing compounds of UV-B
treated plants. Increase of PS 2 activity in UV-A treated plants was seen. Changes in photosynthetic activity were measured
in terms of PS 2 mediated O2 evolution and Chl a fluorescence. 相似文献
3.
Joseph Selvin S. Shanmughapriya R. Gandhimathi G. Seghal Kiran T. Rajeetha Ravji K. Natarajaseenivasan T. A. Hema 《Applied microbiology and biotechnology》2009,83(3):435-445
The sponge-associated actinomycetes were isolated from the marine sponge Dendrilla nigra, collected from the southwest coast of India. Eleven actinomycetes were isolated depending upon the heterogeneity and stability
in subculturing. Among these, Nocardiopsis dassonvillei MAD08 showed 100% activity against the multidrug resistant pathogens tested. The culture conditions of N. dassonvillei MAD08 was optimized under submerged fermentation conditions for enhanced antimicrobial production. The unique feature of
MAD08 includes extracellular amylase, cellulase, lipase, and protease production. These enzymes ultimately increase the scope
of optimization using broad range of raw materials which might be efficiently utilized. The extraction of the cell free supernatant
with ethyl acetate yielded bioactive crude extract that displayed activity against a panel of pathogens tested. Analysis of
the active thin layer chromatography fraction by Fourier transform infrared and gas chromatography-mass spectrometry evidenced
11 compounds with antimicrobial activity. The ammonium sulfate precipitation of the culture supernatant at 80% saturation
yielded an anticandidal protein of molecular weight 87.12 kDa. This is the first strain that produces both organic solvent
and water soluble antimicrobial compounds. The active extract was non-hemolytic and showed surface active property envisaging
its probable role in inhibiting the attachment of pathogens to host tissues, thus, blocking host–pathogen interaction at an
earlier stage of pathogenesis. 相似文献
4.
The first successful isolation of discharged ejectisomes from pigmented cryptophytes is reported. Discharged ejectisomes from
a Chroomonas and two Cryptomonas species were characterized by transmission electron microscopy using negative staining and freeze-etching. Tubular-shaped
fragments of variable lengths and diameters were obtained which showed a paracrystalline lattice. Particle periodicities of
4.1 nm along the longitudinal axis and 3.1 nm in the transverse direction were measured in negative-stained fragments. The
dimensions measured from freeze-etched ejectisome fragments were about 0.5–1 nm larger. Sodium dodecyl sulfate polyacrylamide
gel electrophoresis revealed a protein banding pattern, dominated by polypeptides of 40–44, 23–25 and 16–18 kDa. The results
are discussed in the context of what is currently known about extrusomes of protists. 相似文献
5.
Vi Khanh Truong Stuart Rundell Rimma Lapovok Yuri Estrin James Y. Wang Christopher C. Berndt David G. Barnes Christopher J. Fluke Russell J. Crawford Elena P. Ivanova 《Applied microbiology and biotechnology》2009,83(5):925-937
The influence of the ultrafine crystallinity of commercial purity grade 2 (as-received) titanium and titanium modified by
equal channel angular pressing (modified titanium) on bacterial attachment was studied. A topographic profile analysis of
the surface of the modified titanium revealed a complex morphology of the surface. Its prominent micro- and nano-scale features
were 100–200-nm-scale undulations with 10–15 μm spacing. The undulating surfaces were nano-smooth, with height variations
not exceeding 5–10 nm. These surface topography characteristics were distinctly different from those of the as-received samples,
where broad valleys (up to 40–60 μm) were detected, whose inner surfaces exhibited asperities approximately 100 nm in height
spaced at 1–2 μm. It was found that each of the three bacteria strains used in this study as adsorbates, viz. Staphylococcus aureus CIP 68.5, Pseudomonas aeruginosa ATCC 9025 and Escherichia coli K12, responded differently to the two types of titanium surfaces. Extreme grain refinement by ECAP resulted in substantially
increased numbers of cells attached to the surface compared to as-received titanium. This enhanced degree of attachment was
accompanied with an increased level of extracellular polymeric substances (EPS) production by the bacteria.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
6.
The aim of this study was to determine the in vitro fungicidal and growth inhibitory activity of ciclopirox olamine alone (1% and 1.5%) or in association with 1% zinc pyrithione
compared to 2% ketoconazole, against Malassezia species particularly involved in the pathogenesis of seborrheic dermatitis. Experiments were performed on Malassezia globosa IP 2387.96 and M. restricta IP 2392.96 strains. Growth inhibitory activity of the active compounds in solution was evaluated by measuring minimal inhibitory
concentrations using a broth micro-method and their fungicidal activity by a filtration method after contact times between
solutions and yeasts ranging from 3–5 to 30 min. Concerning the determination of minimal inhibitory concentration of ciclopirox
olamine/zinc pyrithione, it revealed the marked synergistic inhibitory effect of the association, leading to a higher efficacy
compared to ketoconazole. As to the fungicidal activity of ciclopirox olamine, it significantly increased with the contact
time. After 15–30 min of contact between 1.5% ciclopirox olamine and Malassezia strains, a 2-log reduction of Malassezia counts was observed. The 1.5% ciclopirox olamine/1% zinc pyrithione association was characterized by a steady fungicidal
efficacy whereas the 2% ketoconazole solution did not express any fungicidal effect. In conclusion, this study demonstrates
the in vitro inhibitory and fungicidal efficacy of the ciclopirox olamine/zinc pyrithione association against Malassezia species and underscores its potential interest in the treatment of seborrheic dermatitis. 相似文献
7.
The recombinant Bordetella pertussis CyaA pore-forming (CyaA-PF) fragment was previously shown to be expressed separately in Escherichia coli as a soluble precursor that can be in vivo palmitoylated to exert haemolytic activity. In this study, PCR-based mutagenesis
was employed to investigate the contributions to haemolysis of five predicted helices within the N-terminal hydrophobic region
of the CyaA-PF fragment. Single proline substitutions were made for alanine near the centre of each predicted helix as a means
of disrupting local secondary structure. All mutant proteins were over-expressed in E. coli as a 126-kDa soluble protein at levels comparable to the wild-type. Marked reductions in haemolytic activity against sheep
erythrocytes of mutants, A510P, A538P, A583P and A687P pertaining to the putative helices 1500–522, 2529–550, 3571–593 and 5678–698, respectively, were observed. However, a slight decrease in haemolytic activity was found for the proline replacement in
the predicted helix 4602–627 (A616P). MALDI–TOF–MS and LC–MS–MS analyses verified the palmitoylation at Lys983 of all five mutants as identical to that of the CyaA-PF wild-type protein, indicating that toxin modification via this acylation
was not affected by the mutations. Altogether, these results suggest that structural integrity of the predicted helices 1,
2, 3 and 5, but not helix 4, is important for haemolytic activity, particularly for the putative transmembrane helices 2 and
3 that might conceivably be involved in pore formation of the CyaA-PF fragment. 相似文献
8.
Ai Min Ma Lin Jun Shan Hui Jie Wang Zhao Ping Du Bi Jun Xie 《World journal of microbiology & biotechnology》2008,24(4):501-507
Hydrophobins fulfill various physiological functions in fungal development and growth, based on their mechanism of self-assembly
at hydrophilic–hydrophobic interfaces into nano-scale, amphipathic membranes. One hydrophobin with an approximate molecular
weight of 15 kDa, designated Po.HYD1, was purified from aerial hyphae of Pleurotus ostreatus strain Pm039. Ultrastructures of self-assembled films formed by Po.HYD1 on hydrophobic and hydrophilic substrates were revealed
by atomic force microscopy (AFM). A monomolecular adsorption layer, thickness ranging from 3.2 to 3.8 nm, was observed on
the surface of highly oriented pyrolytic graphite (HOPG), while a typical rodlet layer with uniform thickness of 4.2 ± 0.1 nm
formed on the mica surface. Comparison of CD spectra showed significant secondary structural changes between monomeric and
self-assembled states. The spectrum of monomeric Po.HYD1 had a maximum ellipticity at 190 nm and a minimum at 209 nm, and
that of assemblage showed the maximum at 195 nm and the minimum shifted to 215–218 nm. Po.HYD1 showed high surface activity,
based on the dramatic drop of surface tension through self-assembly at the water–air interface. Moreover, Po.HYD1 is capable
of stabilizing the emulsion consisting of water and hexane. 相似文献
9.
Summary In recent years, public concern about indoor mould growth has increased dramatically in the United States. In this study,
lactic acid bacteria (LAB), which are known to produce antimicrobial compounds important in the biopreservation of food, were
evaluated to determine if the same antimicrobial properties can be used to inhibit mould fungi that typically colonize wood.
Based on biomass measurement, cell-free supernatants from Lactobacillus casei subsp. rhamnosus and Lactobacillus acidophilus grown in deMan Rogosa Sharpe (MRS) broth inhibited 95–100% growth of three mould fungi and one stain fungus associated with
wood-based building materials. Lactic acid and four unknown compounds ⩽ kDa molecular weight were fractionated from the culture
supernatant by thin layer chromatography and high-performance liquid chromatography. Antifungal activity, which was attributed
to one or more unknown metabolites, was retained during heating and neutralization. A 1:2 dilution of L. casei supernatant inhibited 100% growth of all test fungi. 相似文献
10.
Wang H Van Blitterswijk CA Bertrand-De Haas M Schuurman AH Lamme EN 《In vitro cellular & developmental biology. Animal》2004,40(8-9):268-277
Summary The number of medical applications using autologous fibroblasts is increasing rapidly. We investigated thoroughly the procedure
to isolate cells from skin using the enzymatic tissue dissociation procedure. Tissue digestion efficiency, cell viability,
and yield were investigated in relation to size of tissue fragments, digestion volume to tissue ratio, digestion time, and
importance of other protease activities present in Clostridium histolyticum collagenase (CHC) (neutral protease, clostripain, and trypsin). The results showed that digestion was optimal with small
tissue fragments (2–3 mm3) and with volumes tissue ratios ≥2 ml/g tissue. For incubations ≤10 h, the digestion efficiency and cell isolation yields
were significantly improved by increasing the collagenase, neutral protease, or clostripain activity, whereas trypsin activity
had no effects. However, a too high proteolytic activity of one of the proteases present in CHC digestion solution or long
exposure times interfered with cell viability and cell culture yields. The optimal range of CHC proteases activities per milliliter
digestion solutions was determined for digestions ≤10 h (collagenase 2700–3900 Mandl U/ml, neutral protease 5100–10,000 caseinase
U/ml, and clostripain 35–48 BAEE U/ml) and for longer digestions (>14 h) (collagenase 1350–3000 U/ml, neutral protease 2550–7700
U/ml, and clostripain 18–36 U/ml). Using these conditions, a maximum fibroblast expansion was achieved when isolated cells
were seeded at 1×104 cells/cm2. These results did not only allow selection of optimal CHC batches able to digest dermal tissue with an high cell viability
but also significantly increased the fibroblast yields, enabling us to produce autologous dermal tissue in a clinically acceptable
time frame of 3 wk. 相似文献
11.
We investigated the effects of long-term acclimation of Eucalyptus nitens seedlings to ultraviolet-A (UV-A) irradiation (320–400 nm) on phenolic compounds (gallotannins, stilbenes, and flavonols),
photochemical efficiency, and chlorophyll and carotenoid contents. Seedlings were raised under four nutrient regimes, ranging
from low to high application rates, in an environment that included or excluded UV-A irradiance. Our aims were: to classify
phenolic compounds that absorb in the UV-A and their relative contribution to total UV-A absorption; to identify how phenolic
compounds respond to UV-A exposure and exclusion, and to determine how plant nutrient status affects acclimation of photo-and
pigment-chemistry to UV-A exposure and exclusion. Gallotannins contributed to only a minor fraction of total absorption within
the lower range (320–360 nm) of the UV-A spectrum. Stilbene and flavonol compounds dominated absorption within the 320–360
and 360–400 nm ranges, respectively. Contents of gallotannin were generally high in UV-A-exposed seedlings. Although there
was a significant effect of UV-A on contents of stilbenes, a general response (across nutrient treatment comparisons) was
not evident. Contents of flavonols were not affected by UV-A exposure. Contents of gallotannin, stilbene, and flavonols decreased
from low to high nutrient-application treatments. There were no effects of UV-A on photochemical efficiency or pigment-chemistry. 相似文献
12.
The effects of different spectral region of excitation and detection of chlorophyll (Chl) a fluorescence at room temperature on the estimation of excitation energy utilization within photosystem (PS) 2 were studied
in wild-type barley (Hordeum vulgare L. cv. Bonus) and its Chl b-less mutant chlorina f2 grown under low and high irradiances [100 and 1 000 μmol(photon) m−2 s−1]. Three measuring spectral regimes were applied using a PAM 101 fluorometer: (1) excitation in the red region (maximum at the wavelength of 649 nm) and detection in the far-red region beyond 710 nm, (2) excitation in the blue region (maximum at the wavelength of 461 nm) and detection beyond 710 nm, and (3) excitation in the blue region and detection in the red region (660– 710 nm). Non-photochemical quenching of maximal (NPQ)
and minimal fluorescence (SV0), determined by detecting Chl a fluorescence beyond 710 nm, were significantly higher for blue excitation as compared to red excitation. We suggest that
this results from higher non-radiative dissipation of absorbed excitation energy within light-harvesting complexes of PS2
(LHC2) due to preferential excitation of LHC2 by blue radiation and from the lower contribution of PS1 emission to the detected
fluorescence in the case of blue excitation. Detection of Chl a fluorescence originating preferentially from PS2 (i.e. in the range of 660–710 nm) led to pronounced increase of NPQ, SV0, and the PS2 photochemical efficiencies (FV/FM and FV′/FM′), indicating considerable underestimation of these parameters using the standard set-up of PAM 101. Hence PS1 contribution to the minimal fluorescence level in the irradiance-adapted state may reach up to about 80 %. 相似文献
13.
Biochemical characterisation of the esterase activities of wine lactic acid bacteria 总被引:1,自引:0,他引:1
Esters are an important group of volatile compounds that can contribute to wine flavour. Wine lactic acid bacteria (LAB) have
been shown to produce esterases capable of hydrolysing ester substrates. This study aims to characterise the esterase activities
of nine LAB strains under important wine conditions, namely, acidic conditions, low temperature (to 10°C) and in the presence
of ethanol (2–18% v/v). Esterase substrate specificity was also examined using seven different ester substrates. The bacteria
were generally found to have a broad pH activity range, with the majority of strains showing maximum activity close to pH 6.0.
Exceptions included an Oenococcus oeni strain that retained most activity even down to a pH of 4.0. Most strains exhibited highest activity across the range 30–40°C.
Increasing ethanol concentration stimulated activity in some of the strains. In particular, O. oeni showed an increase in activity up to a maximum ethanol concentration of around 16%. Generally, strains were found to have
greater activity towards short-chained esters (C2–C8) compared to long-chained esters (C10–C18). Even though the optimal physicochemical
conditions for enzyme activity differed from those found in wine, these findings are of potential importance to oenology because
significant activities remained under wine-like conditions. 相似文献
14.
Pattanayak Debasis Srinivasan K. Mandaokar Ajin D. Shukla Alok Bhalla Ritu Kumar Polumetla A. 《World journal of microbiology & biotechnology》2000,16(7):667-672
Amplified fragment length polymorphism (AFLP)-based fingerprinting of 24 serovars of Bacillus thuringiensis (Bt) representing different serotypes was performed using 13 EcoR1 (+2) and Mse1 (+3) primer combinations for genotypic characterization. A high degree of polymorphism was established among the Bt serovars.
A total of 1107 fragments ranging from 30–850 bp were generated out of which 1106 were polymorphic. Discrimination rates of
different primer combinations at various band levels (1–5) among different Bt serovars were more than 90%. Cluster analysis
revealed very low similarity values, ranging from 7–50%, among the Bt serovars indicating their remarkable genetic diversity.
AFLP analysis establishes the molecular relatedness between the serovars and serotypes.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
Katsuhiko Fujii Shintaro Kikuchi 《World journal of microbiology & biotechnology》2005,21(6-7):1311-1315
Summary Benzophenone (BPH) is an important intermediate in the production of medicines and cosmetics, but is also known as a xenoestrogen
in its effect on mammals. We screened BPH-degrading microbes for potential bioremediation, and found degradation activity
in the activated sludge of a sewage treatment plant in Hokkaido. A microbial strain with notable BPH-degrading activity (strain
MU-1) was isolated from the sample. MU-1 degraded more than 95% of BPH (100–1000 ppm) as a sole carbon source within several
days. However, it took a relatively long time for MU-1 to degrade a high concentration of BPH (5000–10,000 ppm), probably
due to a toxic effect of BPH. The GC/MS analysis of the metabolites of BPH degradation suggested that BPH was degraded into
hydrophilic compounds with very low molecular mass via conversion to phenol. The phylogenetic study based on rDNA sequences
suggested that MU-1 was the black yeast Rhinocladiella aquaspersa. To our knowledge, this is the first report describing a BPH-degrading microbe. 相似文献
16.
Extracellular cholesterol esterase of Burkholderia cepacia strain ST-200 was purified from the culture supernatant. Its molecular mass was 37 kDa. The enzyme was stable at pH 5.5–12 and active at pH 5.5–6, showing optimal activity at pH 7.0 at 45°C. Relative to the commercially available cholesterol esterases, the purified enzyme was highly stable in the presence of various water-miscible organic solvents. The enzyme preferentially hydrolyzed long-chain fatty acid esters of cholesterol, except for that of cholesteryl palmitate. The enzyme exhibited lipolytic activity toward various p-nitrophenyl esters. The hydrolysis rate of p-nitrophenyl caprylate was enhanced 3.5- to 7.2-fold in the presence of 5–20% (vol/vol) water-miscible organic solvents relative to that in the absence of organic solvents. The structural gene encoding the cholesterol esterase was cloned and sequenced. The primary translation product was predicted to be 365 amino acid residues. The mature product is composed of 325 amino acid residues. The amino acid sequence of the product showed the highest similarity to the lipase LipA (87%) from B. cepacia DSM3959. 相似文献
17.
Soror SH Verma V Rao R Rasool S Koul S Qazi GN Cullum J 《Journal of industrial microbiology & biotechnology》2007,34(8):525-531
The genome sequence of Streptomyces coelicolor A3(2) contains 51 putative lipase and esterase genes mostly of unknown function. The gene estB (locus SCO 6966) was expressed as a His-tagged protein in E. coli. Esterase B was active at low temperatures exerting its maximum activity at 30°C and retaining more than 25% of its activity
at 4°C. The optimum pH was 8–8.5. The enzyme was active against short synthetic p-nitrophenylesters (C2–C10) with maximum activity towards the acetate ester (C2). The esterase was tested on 13 series of racemic esters of potential interest for the synthesis of chiral pharmaceutical
compounds. 4 of the series were substrates and a modest degree of enantioselectivity was observed (enantiomeric ratios of
1.1–1.9). 相似文献
18.
Shamila S. Gunatilleke Cesar Augusto F. de Oliveira J. Andrew McCammon Amy M. Barrios 《Journal of biological inorganic chemistry》2008,13(4):555-561
Gold(I) compounds have been used in the treatment of rheumatoid arthritis for over 80 years, but the biological targets and
the structure–activity relationships of these drugs are not well understood. Of particular interest is the molecular mechanism
behind the antiarthritic activity of the orally available drug triethylphosphine(2,3,4,6-tetra-O-acetyl-β-1-d-thiopyranosato-S) gold(I) (auranofin, Ridaura). The cathepsin family of lysosomal, cysteine-dependent enzymes is an attractive biological
target of Au(I) and is inhibited by auranofin and auranofin analogs with reasonable potency. Here we employ a combination
of experimental and computational investigations into the effect of changes in the phosphine ligand of auranofin on its in
vitro inhibition of cathepsin B. Sequential replacement of the ethyl substituents of triethylphosphine by phenyl groups leads
to increasing potency in the resultant Au(I) complexes, due in large part to favorable interactions of the more sterically
bulky Au(I)–PR3 fragments with the enzyme active site. 相似文献
19.
The aim of this research was to study the mechanisms of Lactobacillus brevis antiviral activity towards HSV-2 and to identify the bacterial components responsible for the inhibiting effect. Bacterial extract and cell walls were prepared by lysozyme digestion of L. brevis cells untreated or treated with LiCl to remove S-layer proteins. Bacterial extract and cell wall fragments showed a dose dependent inhibitory effect on HSV-2 multiplication. In order to characterize the inhibitory activity of L. brevis, the bacterial extract was subjected to different physical and chemical treatments. The inhibitory activity was resistant to high temperature and proteases digestion and appeared to be associated with compounds with a molecular weight higher than 10 kDa. DNA, RNA and lipids isolated from bacterial cells were devoid of inhibitory effect. The antiviral activity of both bacterial extract and cell wall fragments obtained from L. brevis cells after the S-layer removal was significantly reduced compared to untreated cells suggesting that the inhibitory activity is likely due to a heat-resistant non-protein cell surface bacterial component. 相似文献
20.
Hemolymph chymotrypsin inhibitor 9 (CI-9) from the hemolymph of the silkworm, Bombyx mori, was purified by ammonium sulfate precipitation, Butyl Toyopearl hydrophobic chromatography, gel filtration through Sephadex
C-50 and chymotrypsin-sepharose 4B affinity chromatography. Checked by Native PAGE and SDS-PAGE in combination with silver
staining, the final preparation appeared homogeneous. In tricine SDS-PAGE, CI-9 displayed a molecular weight of 7.5 kD, which
was determined to be 7167 Da with the Voyager TOFMass analyser. The pI value for CI-9, revealed by 2D-PAGE (two-dimensional polyacrylamide gel electrophoresis), was 4.3. CI-9 exhibited inhibitory
activity at a temperature as high as 100°C and a stability against a wide range of pH (1–12). In N-terminal amino-acid analysis of CI-9, 40 amino acid residues were obtained. The C-terminal 22 amino acid residues were deduced
by subsequently cloned cDNA and genomic fragments. MW and pI of CI-9 were predicted to be 7170.98 Da and 4.61, respectively, on the website. Its low molecular weight, high stability,
conserved active site and Kunitz domain showed that CI-9 is a Kunitz-type CI. The difference of sequence and pI between CI-9 and other Kunitz type CIs indicated that it is a novel chymotrypsin inhibitor. 相似文献