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showing 10 items of 5147 documents
Immunohistochemical Detection of Binding of Cryia Crystal Proteins of Bacillus thuringiensis in Highly Resistant Strains of Plutella xylostella (L.) …
1995
We detected binding of insecticidal crystal proteins from Bacillus thuringiensis in one susceptible strain and six resistant strains of diamondback moth, Plutella xylostella, from Hawaii. Immunohistochemical tests with tissue sections from larval midguts showed specific binding of CryIA(a), CryIA(b), and CryIA(c) to brush border membranes. CryIE, which is not toxic to P. xylostella, did not bind to midgut tissues. Larvae from one of the resistant strains ingested extremely high concentrations of a commercial formulation containing the three CryIA proteins without suffering midgut cell damage or mortality. This same resistant strain had previously been found to have greatly reduced binding o…
Selective inhibition of binding of Bacillus thuringiensis Cry1Ab toxin to cadherin-like and aminopeptidase proteins in brush-border membranes and dis…
2007
Binding analyses with denatured epithelial membrane proteins from Bt (Bacillus thuringiensis) demonstrated at least two kinds of proteins, APNs (aminopeptidases N) and cadherin-like proteins, as possible receptors for the Cry1A class of Bt toxins. Two alternative models have been proposed, both based on initial toxin binding to a cadherin-like protein, but one involving APN and the other not. We have used two Bombyx mori strains (J65 and Kin), which are highly susceptible to Cry1Ab, to study the role of these two types of receptors on Cry1Ab toxin binding and cytotoxicity by means of the inhibitory effect of antibodies. BBMVs (brush-border membrane vesicles) of strain J65 incubated with lab…
Bacillus thuringiensis crystal proteins CRY1Ab and CRY1Fa share a high affinity binding site in Plutella xylostella (L.).
1996
The future success of Bacillus thuringiensis based insecticides depends in part on our ability to prevent insects from developing resistance against their insecticidal crystal proteins. Two recent papers indicated cross-resistance between Cry1A proteins and Cry1Fa in two different insect species (Tabashnik et al., 1994, Appl. Environ. Microbiol. 60, 4627-4629; Gould et al., 1995, J. Econ. Entomol. 88, 1545-1559). Brush border membrane vesicles were prepared from Plutella xylostella and used in binding assays with 125I-labeled trypsin-activated crystal proteins. Competition experiments showed that Cry1Fa competed with Cry1Ab for a same binding site, though the latter still bound to a differe…
Development and Characterization of Diamondback Moth Resistance to Transgenic Broccoli Expressing High Levels of Cry1C
2000
ABSTRACT A field-collected colony of the diamondback moth, Plutella xylostella , had 31-fold resistance to Cry1C protoxin of Bacillus thuringiensis . After 24 generations of selection with Cry1C protoxin and transgenic broccoli expressing a Cry1C protein, the resistance that developed was high enough that neonates of the resistant strain could complete their entire life cycle on transgenic broccoli expressing high levels of Cry1C. After 26 generations of selection, the resistance ratios of this strain to Cry1C protoxin were 12,400- and 63,100-fold, respectively, for the neonates and second instars by a leaf dip assay. The resistance remained stable until generation 38 (G38) under continuous…
Association of Cry1Ac toxin resistance in Helicoverpa zea (Boddie) with increased alkaline phosphatase levels in the midgut lumen.
2012
ABSTRACT Resistance to Bacillus thuringiensis Cry1Ac toxin was characterized in a population of Helicoverpa zea larvae previously shown not to have an alteration in toxin binding as the primary resistance mechanism to this toxin. Cry1Ac-selected larvae (AR1) were resistant to protoxins and toxins of Cry1Ab, Cry1Ac, and the corresponding modified proteins lacking helix α-1 (Cry1AbMod and Cry1AcMod). When comparing brush border membrane vesicles (BBMVs) prepared from susceptible (LC) and AR1 larval midguts, there were only negligible differences in overall Cry1Ac toxin binding, though AR1 had 18% reversible binding, in contrast to LC, in which all binding was irreversible. However, no differe…
In Vivo and In Vitro Binding of Vip3Aa to Spodoptera frugiperda Midgut and Characterization of Binding Sites by 125 I Radiolabeling
2014
ABSTRACT Bacillus thuringiensis vegetative insecticidal proteins (Vip3A) have been recently introduced in important crops as a strategy to delay the emerging resistance to the existing Cry toxins. The mode of action of Vip3A proteins has been studied in Spodoptera frugiperda with the aim of characterizing their binding to the insect midgut. Immunofluorescence histological localization of Vip3Aa in the midgut of intoxicated larvae showed that Vip3Aa bound to the brush border membrane along the entire apical surface. The presence of fluorescence in the cytoplasm of epithelial cells seems to suggest internalization of Vip3Aa or a fragment of it. Successful radiolabeling and optimization of the…
Contrasting temperature responses in seasonal timing of cercariae shedding by Rhipidocotyle trematodes
2022
AbstractGlobal warming is likely to lengthen the seasonal duration of larval release by parasites. We exposed freshwater mussel hosts, Anodonta anatina, from 2 high-latitude populations to high, intermediate and low temperatures throughout the annual cercarial shedding period of the sympatric trematodes Rhipidocotyle fennica and R. campanula, sharing the same transmission pathway. At the individual host level, under warmer conditions, the timing of the cercarial release in both parasite species shifted towards seasonally earlier period while its duration did not change. At the host population level, evidence for the lengthening of larvae shedding period with warming was found for R. fennica…
Buerger`s Disease and Hyperhomocysteinemia: Is there a Relationship?
2009
Thromboangiitis obliterans, also known as Buerger's disease, is a cause of juvenile lower limb ischaemia. Buerger's disease is idiopathic and one of diagnostic criteria is the absence of atherosclerotic risk factors other than smok- ing. A possible involvement of thrombophilia has been investigated and the role of hyperhomocysteinemia is still matter of discussion. We describe 9 patients with Buerger's disease followed-up for the past 3 years. We found a significant in- crease in circulating homocysteine levels (mean: 31.6 in patients vs 8.2 μmol/L in control subjects). We also analyzed the C677T mutation of MTHFR; 5/9 Buerger's patients were heterozygotes and 4/9 homozygotes for the mutati…
Rapamycin stimulates arginine influx through CAT2 transporters in human endothelial cells
2007
In endothelial cells Tumor Necrosis Factor-alpha (TNFalpha) stimulates arginine transport through the increased expression of SLC7A2/CAT2 transcripts. Here we show that also rapamycin, an inhibitor of mTOR kinase, stimulates system y(+)-mediated arginine uptake in human endothelial cells derived from either saphenous (HSVECs) or umbilical veins (HUVECs). When used together with TNFalpha, rapamycin produces an additive stimulation of arginine transport in both cell models. These effects are observed also upon incubation with AICAR, a stimulator of Adenosine-Monophosphate-dependent-Protein Kinase (AMPK) that produces a rapamycin-independent inhibition of the mTOR pathway. Rapamycin increases …
Systemic Inflammation in Metabolic Syndrome: Increased Platelet and Leukocyte Activation, and Key Role of CX3CL1/CX3CR1 and CCL2/CCR2 Axes in Arteria…
2019
Background: Metabolic syndrome is associated with low-grade systemic inflammation, which is a key driver of premature atherosclerosis. We characterized immune cell behavior in metabolic syndrome, its consequences, and the potential involvement of the CX3CL1/CX3CR1 and CCL2/CCR2 chemokine axes. Methods: Whole blood from 18 patients with metabolic syndrome and 21 age-matched controls was analyzed by flow cytometry to determine the leukocyte immunophenotypes, activation, platelet-leukocyte aggregates, and CX3CR1 expression. ELISA determined the plasma marker levels. Platelet-leukocyte aggregates adhesion to tumor necrosis factor-&alpha