Search results for "toxin"
showing 10 items of 1434 documents
Transmembrane beta-barrel of staphylococcal alpha-toxin forms in sensitive but not in resistant cells.
1997
Staphylococcal α-toxin is a 293-residue, single-chain polypeptide that spontaneously assembles into a heptameric pore in target cell membranes. To identify the pore-forming domain, substitution mutants have been produced in which single cysteine residues were introduced throughout the toxin molecule. By attaching the environmentally sensitive dye acrylodan to the sulfhydryl groups, the environment of individual amino acid side chains could be probed. In liposomes, a single 23-amino acid sequence (residues 118–140) was found to move from a polar to a nonpolar environment, indicating that this sequence forms the walls of the pore. However, periodicity in side chain environmental polarity coul…
Evidence that clustered phosphocholine head groups serve as sites for binding and assembly of an oligomeric protein pore.
2006
High susceptibility of rabbit erythrocytes toward the pore-forming action of staphylococcal alpha-toxin correlates with the presence of saturable, high affinity binding sites. All efforts to identify a protein or glycolipid receptor have failed, and the fact that liposomes composed solely of phosphatidylcholine are efficiently permeabilized adds to the enigma. A novel concept is advanced here to explain the puzzle. We propose that low affinity binding moieties can assume the role of high affinity binding sites due to their spatial arrangement in the membrane. Evidence is presented that phosphocholine head groups of sphingomyelin, clustered in sphingomyelin-cholesterol microdomains, serve th…
Control de micotoxines en cereals i derivats per cromatografia liquida espectrometria de masses : avaluació de les ingestes
2012
Mycotoxins are secondary metabolites produced by few fungal species that readily colonize crops and contaminate them with toxins in the field or after harvest. Surveillance studies have showed that mycotoxin contamination is a world-wide problem, since it is estimated that 25% of the world's crop production and 20% of crop production within the European Union may be contaminated with these contaminants. Economic losses deriving from that are tremendous, including reduction of livestock production and agricultural production, health care, veterinary and regulatory costs. The methods described in this Thesis for the extraction of mycotoxins from cereal and derivates used conventional techniqu…
Cross-resistance and mechanism of resistance to Cry1Ab toxin from Bacillus thuringiensis in a field-derived strain of European corn borer, Ostrinia n…
2011
The cross-resistance spectrum and biochemical mechanism of resistance to the Bacillus thuringiensis Cry1Ab toxin was studied in a field-derived strain of Ostrinia nubilalis (Hubner) (Lepidoptera: Crambidae) that was further selected in the laboratory for high levels (>1000-fold) of resistance to Cry1Ab. The resistant strain exhibited high levels of cross-resistance to Cry1Ac and Cry1Aa but only low levels of cross-resistance (<4-fold) to Cry1F. In addition, there was no significant difference between the levels of resistance to full-length and trypsin-activated Cry1Ab protein. No differences in activity of luminal gut proteases or altered proteolytic processing of the toxin were observed in…
Analyses of Cry1Ab binding in resistant and susceptible strains of the European corn borer, Ostrinia nubilalis (Hubner) (Lepidoptera: Crambidae).
2006
ABSTRACT Cry1Ab toxin binding analysis was performed to determine whether resistance in laboratory-selected Ostrinia nubilalis strains is associated with target site alteration. Brush border membrane vesicles were prepared using dissected midguts from late instars of susceptible and resistant strains (Europe-R and RSTT) of O. nubilalis . Immunoblot analysis indicated that three different proteins bound to Cry1Ab toxin and were recognized by an anticadherin serum. In a comparison of resistant and susceptible strains, reduced Cry1Ab binding was apparent for all three bands corresponding to cadherin-like proteins in the Europe-R strain, while reduced binding was apparent in only one band for t…
Quantitative genetic analysis of Cry1Ab tolerance in Ostrinia nubilalis Spanish populations
2013
30 p.-2 fig.-3 tab.
Fusaproliferin, beauvericin and enniatins: occurrence in food – a review
2012
The present review summarises data on the prevalence and concentration of fusaproliferin, beauvericin and enniatins in small grains, maize and processed grain-based foods. These fungal secondary metabolites possess interesting biological activities and are presently often referred to as 'emerging mycotoxins'. They have been considered as less important since they are likely not of acute toxicity. However, their high prevalence in foodstuffs, occasionally in higher mg/kg concentrations, warrants an assessment of their true importance for food (and feed) safety. Thorough surveys that determine the contamination of raw and processed foods with fusaproliferin, beauvericin and enniatins are sti…
Effects of fumonisin B1 on performance of juvenile Baltic salmon (Salmo salar)
2013
Fumonisin B1 is a mycotoxin produced by fungi of the genus Fusarium that frequently occurs on maize (Zea mays) and feeds containing it. The use of plant-based protein sources in feeds designed for aquaculture has increased due to their low costs compared with fishmeal. This trend has resulted in a global increase in feed formulations contaminated with mycotoxins, producing economical losses in aquaculture industry. The topic also causes concerns because of the potential health consequences that aquaculture products could have on human consumers. FB1 mainly disrupts sphingolipid metabolism and also has immune suppressive effects. Fish mycotoxicosis produces a wide range of symptoms from poor…
Transformation of Ochratoxin A by Microorganisms Isolated from Tempranillo Grapes in Wine Systems
2020
Mycotoxins are toxic metabolites produced by various genera of fungi. Fungi belonging to species of the genera Aspergillus and Penicillium are the main source of ochratoxin A (OTA) in wine. The reduction of OTA in must and wine has been studied using physical, chemical, and biological technologies. In this paper, we report on the capacity of different cultures isolated from Tempranillo winegrapes contaminated with fungus to degrade OTA in tryptic soy broth (TSB) medium at pH 3.5 and 6.5. We studied the interaction between OTA and four isolates during alcoholic fermentation of red wine. This study showed that microorganism isolates reduced the content of OTA in TSB medium and in the wine exp…
Prenatal diazepam exposure functionally alters the GABA(A) receptor that modulates [3H]noradrenaline release from rat hippocampal synaptosomes.
2002
In rats, exposure to diazepam (DZ) during the last week of gestation is associated with behavioral alterations (in some cases sexually dimorphic) that appear when the animals reach adulthood. This study was conducted to evaluate the effects of prenatal DZ exposure on the function of the gamma-aminobutyric (GABA)(A) receptor complex. The method used - perfusion of rat hippocampal nerve terminals labeled with [3H]noradrenaline (NA) - allowed us to evaluate the effects of DZ on a specific native GABA(A) receptor subtype which is located on hippocampal noradrenergic nerve endings and mediates the release of NA. Muscimol stimulated synaptosomal release of [3H]NA in a concentration-dependent mann…