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Sample records for heat labile toxin

  1. Structure and function of cholera toxin and the related Escherichia coli heat-labile enterotoxin.

    PubMed Central

    Spangler, B D

    1992-01-01

    Cholera and the related Escherichia coli-associated diarrheal disease are important problems confronting Third World nations and any area where water supplies can become contaminated. The disease is extremely debilitating and may be fatal in the absence of treatment. Symptoms are caused by the action of cholera toxin, secreted by the bacterium Vibrio cholerae, or by a closely related heat-labile enterotoxin, produced by Escherichia coli, that causes a milder, more common traveler's diarrhea. Both toxins bind receptors in intestinal epithelial cells and insert an enzymatic subunit that modifies a G protein associated with the adenylate cyclase complex. The consequent stimulated production of cyclic AMP, or other factors such as increased synthesis of prostaglandins by intoxicated cells, initiates a metabolic cascade that results in the excessive secretion of fluid and electrolytes characteristic of the disease. The toxins have a very high degree of structural and functional homology and may be evolutionarily related. Several effective new vaccine formulations have been developed and tested, and a growing family of endogenous cofactors is being discovered in eukaryotic cells. The recent elucidation of the three-dimensional structure of the heat-labile enterotoxin has provided an opportunity to examine and compare the correlations between structure and function of the two toxins. This information may improve our understanding of the disease process itself, as well as illuminate the role of the toxin in studies of signal transduction and G-protein function. Images PMID:1480112

  2. Adhesin degradation accelerates delivery of heat-labile toxin by enterotoxigenic Escherichia coli.

    PubMed

    Roy, Koushik; Kansal, Rita; Bartels, Scott R; Hamilton, David J; Shaaban, Salwa; Fleckenstein, James M

    2011-08-26

    Many enteric pathogens, including enterotoxigenic Escherichia coli (ETEC), produce one or more serine proteases that are secreted via the autotransporter (or type V) bacterial secretion pathway. These molecules have collectively been referred to as SPATE proteins (serine protease autotransporter of the Enterobacteriaceae). EatA, an autotransporter previously identified in ETEC, possesses a functional serine protease motif within its secreted amino-terminal passenger domain. Although this protein is expressed by many ETEC strains and is highly immunogenic, its precise function is unknown. Here, we demonstrate that EatA degrades a recently characterized adhesin, EtpA, resulting in modulation of bacterial adhesion and accelerated delivery of the heat-labile toxin, a principal ETEC virulence determinant. Antibodies raised against the passenger domain of EatA impair ETEC delivery of labile toxin to epithelial cells suggesting that EatA may be an effective target for vaccine development. PMID:21757737

  3. Parenteral Adjuvant Effects of an Enterotoxigenic Escherichia coli Natural Heat-Labile Toxin Variant.

    PubMed

    Braga, Catarina J M; Rodrigues, Juliana F; Medina-Armenteros, Yordanka; Farinha-Arcieri, Luís E; Ventura, Armando M; Boscardin, Silvia B; Sbrogio-Almeida, Maria E; Ferreira, Luís C S

    2014-01-01

    Native type I heat-labile toxins (LTs) produced by enterotoxigenic Escherichia coli (ETEC) strains exert strong adjuvant effects on both antibody and T cell responses to soluble and particulate antigens following co-administration via mucosal routes. However, inherent enterotoxicity and neurotoxicity (following intra-nasal delivery) had reduced the interest in the use of these toxins as mucosal adjuvants. LTs can also behave as powerful and safe adjuvants following delivery via parenteral routes, particularly for activation of cytotoxic lymphocytes. In the present study, we evaluated the adjuvant effects of a new natural LT polymorphic form (LT2), after delivery via intradermal (i.d.) and subcutaneous (s.c.) routes, with regard to both antibody and T cell responses. A recombinant HIV-1 p24 protein was employed as a model antigen for determination of antigen-specific immune responses while the reference LT (LT1), produced by the ETEC H10407 strain, and a non-toxigenic LT form (LTK63) were employed as previously characterized LT types. LT-treated mice submitted to a four dose-base immunization regimen elicited similar p24-specific serum IgG responses and CD4(+) T cell activation. Nonetheless, mice immunized with LT1 or LT2 induced higher numbers of antigen-specific CD8(+) T cells and in vivo cytotoxic responses compared to mice immunized with the non-toxic LT derivative. These effects were correlated with stronger activation of local dendritic cell populations. In addition, mice immunized with LT1 and LT2, but not with LTK63, via s.c. or i.d. routes developed local inflammatory reactions. Altogether, the present results confirmed that the two most prevalent natural polymorphic LT variants (LT1 or LT2) display similar and strong adjuvant effects for subunit vaccines administered via i.d. or s.c. routes.

  4. Escherichia coli K88ac fimbriae expressing heat-labile and heat-stable (STa) toxin epitopes elicit antibodies that neutralize cholera toxin and STa toxin and inhibit adherence of K88ac fimbrial E. coli.

    PubMed

    Zhang, Chengxian; Zhang, Weiping

    2010-12-01

    Enterotoxigenic Escherichia coli (ETEC) strains are a major cause of diarrheal disease in humans and animals. Bacterial adhesins and heat-labile (LT) and heat-stable (ST) enterotoxins are the virulence determinants in ETEC diarrhea. It is believed that vaccines inducing anti-adhesin immunity to inhibit bacterial adherence and anti-toxin immunity to eliminate toxin activity would provide broad-spectrum protection against ETEC. In this study, an ETEC fimbrial adhesin was used as a platform to express LT and STa for adhesin-toxin fusion antigens to induce anti-toxin and anti-adhesin immunity. An epitope from the B subunit of LT toxin (LTP1, (8)LCSEYRNTQIYTIN(21)) and an STa toxoid epitope ((5)CCELCCNPQCAGCY(18)) were embedded in the FaeG major subunit of E. coli K88ac fimbriae. Constructed K88ac-toxin chimeric fimbriae were harvested and used for rabbit immunization. Immunized rabbits developed anti-K88ac, anti-LT, and anti-STa antibodies. Moreover, induced antibodies not only inhibited adherence of K88ac fimbrial E. coli to porcine small intestinal enterocytes but also neutralized cholera toxin and STa toxin. Data from this study demonstrated that K88ac fimbriae expressing LT and STa epitope antigens elicited neutralizing anti-toxin antibodies and anti-adhesin antibodies and suggested that E. coli fimbriae could serve as a platform for the development of broad-spectrum vaccines against ETEC. PMID:20980482

  5. Allele variants of enterotoxigenic Escherichia coli heat-labile toxin are globally transmitted and associated with colonization factors.

    PubMed

    Joffré, Enrique; von Mentzer, Astrid; Abd El Ghany, Moataz; Oezguen, Numan; Savidge, Tor; Dougan, Gordon; Svennerholm, Ann-Mari; Sjöling, Åsa

    2015-01-01

    Enterotoxigenic Escherichia coli (ETEC) is a significant cause of morbidity and mortality in the developing world. ETEC-mediated diarrhea is orchestrated by heat-labile toxin (LT) and heat-stable toxins (STp and STh), acting in concert with a repertoire of more than 25 colonization factors (CFs). LT, the major virulence factor, induces fluid secretion after delivery of a monomeric ADP-ribosylase (LTA) and its pentameric carrier B subunit (LTB). A study of ETEC isolates from humans in Brazil reported the existence of natural LT variants. In the present study, analysis of predicted amino acid sequences showed that the LT amino acid polymorphisms are associated with a geographically and temporally diverse set of 192 clinical ETEC strains and identified 12 novel LT variants. Twenty distinct LT amino acid variants were observed in the globally distributed strains, and phylogenetic analysis showed these to be associated with different CF profiles. Notably, the most prevalent LT1 allele variants were correlated with major ETEC lineages expressing CS1 + CS3 or CS2 + CS3, and the most prevalent LT2 allele variants were correlated with major ETEC lineages expressing CS5 + CS6 or CFA/I. LTB allele variants generally exhibited more-stringent amino acid sequence conservation (2 substitutions identified) than LTA allele variants (22 substitutions identified). The functional impact of LT1 and LT2 polymorphisms on virulence was investigated by measuring total-toxin production, secretion, and stability using GM1-enzyme-linked immunosorbent assays (GM1-ELISA) and in silico protein modeling. Our data show that LT2 strains produce 5-fold more toxin than LT1 strains (P < 0.001), which may suggest greater virulence potential for this genetic variant. Our data suggest that functionally distinct LT-CF variants with increased fitness have persisted during the evolution of ETEC and have spread globally. PMID:25404692

  6. Different assay conditions for detecting the production and release of heat-labile and heat-stable toxins in enterotoxigenic Escherichia coli isolates.

    PubMed

    Rocha, Letícia B; Ozaki, Christiane Y; Horton, Denise S P Q; Menezes, Caroline A; Silva, Anderson; Fernandes, Irene; Magnoli, Fabio C; Vaz, Tania M I; Guth, Beatriz E C; Piazza, Roxane M F

    2013-12-02

    Enterotoxigenic Escherichia coli (ETEC) produce heat-labile (LT) and/or heat-stable enterotoxins (ST). Despite that, the mechanism of action of both toxins are well known, there is great controversy in the literature concerning the in vitro production and release of LT and, for ST, no major concerns have been discussed. Furthermore, the majority of published papers describe the use of only one or a few ETEC isolates to define the production and release of these toxins, which hinders the detection of ETEC by phenotypic approaches. Thus, the present study was undertaken to obtain a better understanding of ST and LT toxin production and release under laboratory conditions. Accordingly, a collection of 90 LT-, ST-, and ST/LT-producing ETEC isolates was used to determine a protocol for toxin production and release aimed at ETEC detection. For this, we used previously raised anti-LT antibodies and the anti-ST monoclonal and polyclonal antibodies described herein. The presence of bile salts and the use of certain antibiotics improved ETEC toxin production/release. Triton X-100, as chemical treatment, proved to be an alternative method for toxin release. Consequently, a common protocol that can increase the production and release of LT and ST toxins could facilitate and enhance the sensitivity of diagnostic tests for ETEC using the raised and described antibodies in the present work.

  7. Comparative Adjuvant Effects of Type II Heat-Labile Enterotoxins in Combination with Two Different Candidate Ricin Toxin Vaccine Antigens

    PubMed Central

    Greene, Christopher J.; Rong, Yinghui; Mandell, Lorrie M.; Connell, Terry D.

    2015-01-01

    Type II heat-labile enterotoxins (HLTs) constitute a promising set of adjuvants that have been shown to enhance humoral and cellular immune responses when coadministered with an array of different proteins, including several pathogen-associated antigens. However, the adjuvant activities of the four best-studied HLTs, LT-IIa, LT-IIb, LT-IIbT13I, and LT-IIc, have never been compared side by side. We therefore conducted immunization studies in which LT-IIa, LT-IIb, LT-IIbT13I, and LT-IIc were coadministered by the intradermal route to mice with two clinically relevant protein subunit vaccine antigens derived from the enzymatic A subunit (RTA) of ricin toxin, RiVax and RVEc. The HLTs were tested with low and high doses of antigen and were assessed for their abilities to stimulate antigen-specific serum IgG titers, ricin toxin-neutralizing activity (TNA), and protective immunity. We found that all four HLTs tested were effective adjuvants when coadministered with RiVax or RVEc. LT-IIa was of particular interest because as little as 0.03 μg when coadministered with RiVax or RVEc proved effective at augmenting ricin toxin-specific serum antibody titers with nominal evidence of local inflammation. Collectively, these results justify the need for further studies into the mechanism(s) underlying LT-IIa adjuvant activity, with the long-term goal of evaluating LT-IIa's activity in humans. PMID:26491037

  8. Cooperative role of antibodies against heat-labile toxin and the EtpA Adhesin in preventing toxin delivery and intestinal colonization by enterotoxigenic Escherichia coli.

    PubMed

    Roy, Koushik; Hamilton, David J; Fleckenstein, James M

    2012-10-01

    Enterotoxigenic Escherichia coli (ETEC) is an important cause of diarrheal disease in developing countries, where it is responsible for hundreds of thousands of deaths each year. Vaccine development for ETEC has been hindered by the heterogeneity of known molecular targets and the lack of broad-based sustained protection afforded by existing vaccine strategies. In an effort to explore the potential role of novel antigens in ETEC vaccines, we examined the ability of antibodies directed against the ETEC heat-labile toxin (LT) and the recently described EtpA adhesin to prevent intestinal colonization in vivo and toxin delivery to epithelial cells in vitro. We demonstrate that EtpA is required for the optimal delivery of LT and that antibodies against this adhesin play at least an additive role in preventing delivery of LT to target intestinal cells when combined with antibodies against either the A or B subunits of the toxin. Moreover, vaccination with a combination of LT and EtpA significantly impaired intestinal colonization. Together, these results suggest that the incorporation of recently identified molecules such as EtpA could be used to enhance current approaches to ETEC vaccine development. PMID:22875600

  9. Single Chain Variable Fragments Produced in Escherichia coli against Heat-Labile and Heat-Stable Toxins from Enterotoxigenic E. coli

    PubMed Central

    Andrade, Fernanda B.; Nepomuceno, Roberto; Silva, Anderson; Munhoz, Danielle D.; Yamamoto, Bruno B.; Luz, Daniela; Abreu, Patrícia A. E.; Horton, Denise S. P. Q.; Elias, Waldir P.; Ramos, Oscar H. P.; Piazza, Roxane M. F.

    2015-01-01

    Background Diarrhea is a prevalent pathological condition frequently associated to the colonization of the small intestine by enterotoxigenic Escherichia coli (ETEC) strains, known to be endemic in developing countries. These strains can produce two enterotoxins associated with the manifestation of clinical symptoms that can be used to detect these pathogens. Although several detection tests have been developed, minimally equipped laboratories are still in need of simple and cost-effective methods. With the aim to contribute to the development of such diagnostic approaches, we describe here two mouse hybridoma-derived single chain fragment variable (scFv) that were produced in E. coli against enterotoxins of ETEC strains. Methods and Findings Recombinant scFv were developed against ETEC heat-labile toxin (LT) and heat-stable toxin (ST), from previously isolated hybridoma clones. This work reports their design, construction, molecular and functional characterization against LT and ST toxins. Both antibody fragments were able to recognize the cell-interacting toxins by immunofluorescence, the purified toxins by ELISA and also LT-, ST- and LT/ST-producing ETEC strains. Conclusion The developed recombinant scFvs against LT and ST constitute promising starting point for simple and cost-effective ETEC diagnosis. PMID:26154103

  10. The LT1 and LT2 variants of the enterotoxigenic Escherichia coli (ETEC) heat-labile toxin (LT) are associated with major ETEC lineages.

    PubMed

    Joffré, Enrique; Sjöling, Åsa

    2016-01-01

    The heat-labile toxin (LT) is one of the major virulence factors of enterotoxigenic Escherichia coli (ETEC). We recently described that 20 polymorphic LT variants are present in ETEC strains isolated globally. Two of the variants, LT1 and LT2, are particularly common and we found that they were associated with clonal ETEC lineages that express the colonization factors (CFs), CFA/I, CS1+CS3, CS2+CS3, and CS5+CS6. ETEC expressing these CFs are frequently found among ETEC strains isolated from cases with diarrhea. ETEC expressing the colonization factors CS1+CS3, and CS2+CS3 are found in 2 discrete clonal lineages and express the LT1 variant and heat stable toxin (STh). Although they clearly are virulent they neither produce, nor secrete, high amounts of LT toxin. On the other hand ETEC strains expressing LT, STh, CFA/I and LT, STh, CS5+CS6, carry the LT2 variant and produce and secrete significantly more LT toxin. Despite differences in toxin production, LT1 and LT2 are found in ETEC lineages that have managed to spread globally confirming that these variants are important for ETEC virulence. PMID:26939855

  11. The LT1 and LT2 variants of the enterotoxigenic Escherichia coli (ETEC) heat-labile toxin (LT) are associated with major ETEC lineages

    PubMed Central

    Joffré, Enrique; Sjöling, Åsa

    2016-01-01

    ABSTRACT The heat-labile toxin (LT) is one of the major virulence factors of enterotoxigenic Escherichia coli (ETEC). We recently described that 20 polymorphic LT variants are present in ETEC strains isolated globally. Two of the variants, LT1 and LT2, are particularly common and we found that they were associated with clonal ETEC lineages that express the colonization factors (CFs), CFA/I, CS1+CS3, CS2+CS3, and CS5+CS6. ETEC expressing these CFs are frequently found among ETEC strains isolated from cases with diarrhea. ETEC expressing the colonization factors CS1+CS3, and CS2+CS3 are found in 2 discrete clonal lineages and express the LT1 variant and heat stable toxin (STh). Although they clearly are virulent they neither produce, nor secrete, high amounts of LT toxin. On the other hand ETEC strains expressing LT, STh, CFA/I and LT, STh, CS5+CS6, carry the LT2 variant and produce and secrete significantly more LT toxin. Despite differences in toxin production, LT1 and LT2 are found in ETEC lineages that have managed to spread globally confirming that these variants are important for ETEC virulence. PMID:26939855

  12. Heterogenic virulence in a diarrheagenic Escherichia coli: evidence for an EPEC expressing heat-labile toxin of ETEC.

    PubMed

    Dutta, Sanjucta; Pazhani, Gururaja P; Nataro, James P; Ramamurthy, Thandavarayan

    2015-01-01

    We have encountered an Escherichia coli strain isolated from a child with acute diarrhea. This strain harbored eae and elt genes encoding for E. coli attaching and effacing property and heat-labile enterotoxin of EPEC and ETEC, respectively. Due to the presence of these distinct virulence factors, we named this uncommon strain as EPEC/ETEC hybrid. The elt gene was identified in a conjugally transferable plasmid of the EPEC/ETEC hybrid. In addition, several virulence genes in the locus of enterocyte effacement have been identified, which confirms that the EPEC/ETEC has an EPEC genetic background. The hybrid nature of this strain was further confirmed by using tissue culture assays. In the multi locus sequence typing (MLST) analysis, the EPEC/ETEC belonged to the sequence type ST328 and was belonging to ST278 Cplx. Sequence analysis of the plasmid DNA revealed presence of six large contigs with several insertion sequences. A phage integrase gene and the prophages of gp48 and gp49 have been found in the upstream of eltAB. In the downstream of elt, an urovirulence loci adhesion encoding (pap) cluster containing papG, and papC were also identified. Similar to other reports, we have identified a heterogenic virulence in a diarrheagenic E. coli but with different combination of genes. PMID:25465159

  13. Design and characterization of a chimeric multiepitope construct containing CfaB, heat-stable toxoid, CssA, CssB, and heat-labile toxin subunit B of enterotoxigenic Escherichia coli: a bioinformatic approach.

    PubMed

    Zeinalzadeh, Narges; Salmanian, Ali Hatef; Ahangari, Ghasem; Sadeghi, Mahdi; Amani, Jafar; Bathaie, S Zahra; Jafari, Mahyat

    2014-01-01

    Enterotoxigenic Escherichia coli (ETEC) strains are the most common cause of bacterial diarrhea in children in developing countries and travelers to these areas. Enterotoxins and colonization factors (CFs) are two key virulence factors in ETEC pathogenesis, and the heterogeneity of the CFs is the bottleneck in reaching an effective vaccine. In this study, a candidate subunit vaccine, which is composed of CfaB, CssA and CssB, structural subunits of colonization factor antigen I and CS6 CFs, labile toxin subunit B, and the binding subunit of heat-labile and heat-stable toxoid, was designed to provide broad-spectrum protection against ETEC. The different features of chimeric gene, its mRNA stability, and chimeric protein properties were analyzed by using bioinformatic tools. The optimized chimeric gene was chemically synthesized and expressed successfully in a prokaryotic host. The purified protein was used for assessment of bioinformatic data by experimental methods.

  14. Design and characterization of a chimeric multiepitope construct containing CfaB, heat-stable toxoid, CssA, CssB, and heat-labile toxin subunit B of enterotoxigenic Escherichia coli: a bioinformatic approach.

    PubMed

    Zeinalzadeh, Narges; Salmanian, Ali Hatef; Ahangari, Ghasem; Sadeghi, Mahdi; Amani, Jafar; Bathaie, S Zahra; Jafari, Mahyat

    2014-01-01

    Enterotoxigenic Escherichia coli (ETEC) strains are the most common cause of bacterial diarrhea in children in developing countries and travelers to these areas. Enterotoxins and colonization factors (CFs) are two key virulence factors in ETEC pathogenesis, and the heterogeneity of the CFs is the bottleneck in reaching an effective vaccine. In this study, a candidate subunit vaccine, which is composed of CfaB, CssA and CssB, structural subunits of colonization factor antigen I and CS6 CFs, labile toxin subunit B, and the binding subunit of heat-labile and heat-stable toxoid, was designed to provide broad-spectrum protection against ETEC. The different features of chimeric gene, its mRNA stability, and chimeric protein properties were analyzed by using bioinformatic tools. The optimized chimeric gene was chemically synthesized and expressed successfully in a prokaryotic host. The purified protein was used for assessment of bioinformatic data by experimental methods. PMID:24372617

  15. Quantitative Proteomic Analysis of Escherichia coli Heat-Labile Toxin B Subunit (LTB) with Enterovirus 71 (EV71) Subunit VP1

    PubMed Central

    Liu, Lin; Ma, Yongping; Zhou, Huicong; Wu, Mingjun

    2016-01-01

    The nontoxic heat-labile toxin (LT) B subunit (LTB) was used as mucosal adjuvant experimentally. However, the mechanism of LTB adjuvant was still unclear. The LTB and enterovirus 71 (EV71) VP1 subunit (EVP1) were constructed in pET32 and expressed in E. coli BL21, respectively. The immunogenicity of purified EVP1 and the adjuvanticity of LTB were evaluated via intranasal immunization EVP1 plus LTB in Balb/c mice. In order to elucidate the proteome change triggered by the adjuvant of LTB, the proteomic profiles of LTB, EVP1, and LTB plus EVP1 were quantitatively analyzed by iTRAQ-LC-MS/MS (isobaric tags for relative and absolute quantitation; liquid chromatography-tandem mass spectrometry) in murine macrophage RAW264.7. The proteomic data were analyzed by bioinformatics and validated by western blot analysis. The predicted protein interactions were confirmed using LTB pull-down and the LTB processing pathway was validated by confocal microscopy. The results showed that LTB significantly boosted EVP1 specific systematic and mucosal antibodies. A total of 3666 differential proteins were identified in the three groups. Pathway enrichment of proteomic data predicted that LTB upregulated the specific and dominant MAPK (mitogen-activated protein kinase) signaling pathway and the protein processing in endoplasmic reticulum (PPER) pathway, whereas LTB or EVP1 did not significantly upregulate these two signaling pathways. Confocal microscopy and LTB pull-down assays confirmed that the LTB adjuvant was endocytosed and processed through endocytosis (ENS)-lysosomal-endoplasmic reticulum (ER) system. PMID:27618897

  16. A live attenuated Salmonella Enteritidis secreting detoxified heat labile toxin enhances mucosal immunity and confers protection against wild-type challenge in chickens.

    PubMed

    Lalsiamthara, Jonathan; Kamble, Nitin Machindra; Lee, John Hwa

    2016-01-01

    A live attenuated Salmonella Enteritidis (SE) capable of constitutively secreting detoxified double mutant Escherichia coli heat labile toxin (dmLT) was developed. The biologically adjuvanted strain was generated via transformation of a highly immunogenic SE JOL1087 with a plasmid encoding dmLT gene cassette; the resultant strain was designated JOL1641. A balanced-lethal host-vector system stably maintained the plasmid via auxotrophic host complementation with a plasmid encoded aspartate semialdehyde dehydrogenase (asd) gene. Characterization by western blot assay revealed the dmLT subunit proteins in culture supernatants of JOL1641. For the investigation of adjuvanticity and protective efficacy, chickens were immunized via oral or intramuscular routes with PBS, JOL1087 and JOL1641. Birds immunized with JOL1641 showed significant (P ≤ 0.05) increases in intestinal SIgA production at the 1(st) and 2(nd) weeks post-immunization via oral and intramuscular routes, respectively. Interestingly, while both strains showed significant splenic protection via intramuscular immunization, JOL1641 outperformed JOL1087 upon oral immunization. Oral immunization of birds with JOL1641 significantly reduced splenic bacterial counts. The reduction in bacterial counts may be correlated with an adjuvant effect of dmLT that increases SIgA secretion in the intestines of immunized birds. The inclusion of detoxified dmLT in the strain did not cause adverse reactions to birds, nor did it extend the period of bacterial fecal shedding. In conclusion, we report here that dmLT could be biologically incorporated in the secretion system of a live attenuated Salmonella-based vaccine, and that this construction is safe and could enhance mucosal immunity, and protect immunized birds against wild-type challenge. PMID:27262338

  17. The catalytic A1 domains of cholera toxin and heat-labile enterotoxin are potent DNA adjuvants that evoke mixed Th1/Th17 cellular immune responses

    PubMed Central

    Bagley, Kenneth; Xu, Rong; Ota-Setlik, Ayuko; Egan, Michael; Schwartz, Jennifer; Fouts, Timothy

    2015-01-01

    DNA encoded adjuvants are well known for increasing the magnitude of cellular and/or humoral immune responses directed against vaccine antigens. DNA adjuvants can also tune immune responses directed against vaccine antigens to better protect against infection of the target organism. Two potent DNA adjuvants that have unique abilities to tune immune responses are the catalytic A1 domains of Cholera Toxin (CTA1) and Heat-Labile Enterotoxin (LTA1). Here, we have characterized the adjuvant activities of CTA1 and LTA1 using HIV and SIV genes as model antigens. Both of these adjuvants enhanced the magnitude of antigen-specific cellular immune responses on par with those induced by the well-characterized cytokine adjuvants IL-12 and GM-CSF. CTA1 and LTA1 preferentially enhanced cellular responses to the intracellular antigen SIVmac239-gag over those for the secreted HIVBaL-gp120 antigen. IL-12, GM-CSF and electroporation did the opposite suggesting differences in the mechanisms of actions of these diverse adjuvants. Combinations of CTA1 or LTA1 with IL-12 or GM-CSF generated additive and better balanced cellular responses to both of these antigens. Consistent with observations made with the holotoxin and the CTA1-DD adjuvant, CTA1 and LTA1 evoked mixed Th1/Th17 cellular immune responses. Together, these results show that CTA1 and LTA1 are potent DNA vaccine adjuvants that favor the intracellular antigen gag over the secreted antigen gp120 and evoke mixed Th1/Th17 responses against both of these antigens. The results also indicate that achieving a balanced immune response to multiple intracellular and extracellular antigens delivered via DNA vaccination may require combining adjuvants that have different and complementary mechanisms of action. PMID:26042527

  18. Mutant Escherichia coli Heat-Labile Toxin B Subunit That Separates Toxoid-Mediated Signaling and Immunomodulatory Action from Trafficking and Delivery Functions

    PubMed Central

    Fraser, Sylvia A.; de Haan, Lolke; Hearn, Arron R.; Bone, Heather K.; Salmond, Robert J.; Rivett, A. Jennifer; Williams, Neil A.; Hirst, Timothy R.

    2003-01-01

    The homopentameric B-subunit components of Escherichia coli heat-labile enterotoxin (EtxB) and cholera toxin (CtxB) possess the capacity to enter mammalian cells and to activate cell-signaling events in leukocytes that modulate immune cell function. Both properties have been attributed to the ability of the B subunits to bind to GM1-ganglioside receptors, a ubiquitous glycosphingolipid found in the plasma membrane. Here we describe the properties of EtxB(H57S), a mutant B subunit with a His→Ser substitution at position 57. The mutant was found to be severely defective in inducing leukocyte signaling, as shown by failure to (i) trigger caspase 3-mediated CD8+-T-cell apoptosis, (ii) activate nuclear translocation of NF-κB in Jurkat T cells, (iii) induce a potent anti-B-subunit response in mice, or (iv) serve as a mucosal adjuvant. However, its GM1 binding, cellular uptake, and delivery functions remained intact. This was further validated by the finding that EtxB(H57S) was as effective as EtxB in delivering a conjugated model class I epitope into the major histocompatibility complex class I pathway of a dendritic cell line. These observations imply that GM1 binding alone is not sufficient to trigger the signaling events responsible for the potent immunomodulatory properties of EtxB. Moreover, they demonstrate that its signaling properties play no role in EtxB uptake and trafficking. Thus, EtxB(H57S) represents a novel tool for evaluating the complex cellular interactions and signaling events occurring after receptor interaction, as well as offering an alternative means of delivering attached peptides in the absence of the potent immunomodulatory signals induced by wild-type B subunits. PMID:12595472

  19. Quantitative Proteomic Analysis of Escherichia coli Heat-Labile Toxin B Subunit (LTB) with Enterovirus 71 (EV71) Subunit VP1.

    PubMed

    Liu, Lin; Ma, Yongping; Zhou, Huicong; Wu, Mingjun

    2016-01-01

    The nontoxic heat-labile toxin (LT) B subunit (LTB) was used as mucosal adjuvant experimentally. However, the mechanism of LTB adjuvant was still unclear. The LTB and enterovirus 71 (EV71) VP1 subunit (EVP1) were constructed in pET32 and expressed in E. coli BL21, respectively. The immunogenicity of purified EVP1 and the adjuvanticity of LTB were evaluated via intranasal immunization EVP1 plus LTB in Balb/c mice. In order to elucidate the proteome change triggered by the adjuvant of LTB, the proteomic profiles of LTB, EVP1, and LTB plus EVP1 were quantitatively analyzed by iTRAQ-LC-MS/MS (isobaric tags for relative and absolute quantitation; liquid chromatography-tandem mass spectrometry) in murine macrophage RAW264.7. The proteomic data were analyzed by bioinformatics and validated by western blot analysis. The predicted protein interactions were confirmed using LTB pull-down and the LTB processing pathway was validated by confocal microscopy. The results showed that LTB significantly boosted EVP1 specific systematic and mucosal antibodies. A total of 3666 differential proteins were identified in the three groups. Pathway enrichment of proteomic data predicted that LTB upregulated the specific and dominant MAPK (mitogen-activated protein kinase) signaling pathway and the protein processing in endoplasmic reticulum (PPER) pathway, whereas LTB or EVP1 did not significantly upregulate these two signaling pathways. Confocal microscopy and LTB pull-down assays confirmed that the LTB adjuvant was endocytosed and processed through endocytosis (ENS)-lysosomal-endoplasmic reticulum (ER) system.

  20. Quantitative Proteomic Analysis of Escherichia coli Heat-Labile Toxin B Subunit (LTB) with Enterovirus 71 (EV71) Subunit VP1.

    PubMed

    Liu, Lin; Ma, Yongping; Zhou, Huicong; Wu, Mingjun

    2016-01-01

    The nontoxic heat-labile toxin (LT) B subunit (LTB) was used as mucosal adjuvant experimentally. However, the mechanism of LTB adjuvant was still unclear. The LTB and enterovirus 71 (EV71) VP1 subunit (EVP1) were constructed in pET32 and expressed in E. coli BL21, respectively. The immunogenicity of purified EVP1 and the adjuvanticity of LTB were evaluated via intranasal immunization EVP1 plus LTB in Balb/c mice. In order to elucidate the proteome change triggered by the adjuvant of LTB, the proteomic profiles of LTB, EVP1, and LTB plus EVP1 were quantitatively analyzed by iTRAQ-LC-MS/MS (isobaric tags for relative and absolute quantitation; liquid chromatography-tandem mass spectrometry) in murine macrophage RAW264.7. The proteomic data were analyzed by bioinformatics and validated by western blot analysis. The predicted protein interactions were confirmed using LTB pull-down and the LTB processing pathway was validated by confocal microscopy. The results showed that LTB significantly boosted EVP1 specific systematic and mucosal antibodies. A total of 3666 differential proteins were identified in the three groups. Pathway enrichment of proteomic data predicted that LTB upregulated the specific and dominant MAPK (mitogen-activated protein kinase) signaling pathway and the protein processing in endoplasmic reticulum (PPER) pathway, whereas LTB or EVP1 did not significantly upregulate these two signaling pathways. Confocal microscopy and LTB pull-down assays confirmed that the LTB adjuvant was endocytosed and processed through endocytosis (ENS)-lysosomal-endoplasmic reticulum (ER) system. PMID:27618897

  1. Nanoparticulated heat-stable (STa) and heat-labile B subunit (LTB) recombinant toxin improves vaccine protection against enterotoxigenic Escherichia coli challenge in mouse.

    PubMed

    Deng, Guangcun; Zeng, Jin; Jian, Minjie; Liu, Wenmiao; Zhang, Zhong; Liu, Xiaoming; Wang, Yujiong

    2013-02-01

    Enterotoxigenic Escherichia coli (ETEC) remains a major cause of diarrheic disease in developing areas, for which there is no effective vaccine available. In this study, we genetically engineered a recombinant heat-stable enterotoxin (STa) coupled to the subunit B of heat-labile enterotoxin (LTB). This fusion protein, STa-LTB, possesses a single amino acid substitution at position 14 of STa. Our data demonstrates that the enterotoxicity of STa in STa-LTB was dramatically reduced. A gelatin nanovaccine candidate was prepared using the purified STa-LTB fusion protein characterized with an entrapment efficiency of 84.88 ± 6.37% and smooth spheres size ranges of 80-200 nm. Antigen-specific antibody responses against STa-LTB and STa in the sera and the intestinal mucus respectively were used to test the immunogenicity of the nanovaccine. This vaccine was further screened in mice by its ability to elicit neutralizing antibodies against STa and protect animals from the challenge with ETEC in mice. The STa-LTB nanoparticles delivered demonstrated a capacity to induce significantly higher and long-lasting antibody responses and increased immune protection against ETEC challenge relative to the control STa-LTB vaccine absorbed in conventional aluminum hydrate salt (p < 0.01). These results warrant the further studies of the development of a novel nanoparticulate vaccine as a broad-spectrum vaccine against ETEC infection.

  2. Evaluating the A-Subunit of the Heat-Labile Toxin (LT) As an Immunogen and a Protective Antigen Against Enterotoxigenic Escherichia coli (ETEC).

    PubMed

    Norton, Elizabeth B; Branco, Luis M; Clements, John D

    2015-01-01

    Diarrheal illness contributes to malnutrition, stunted growth, impaired cognitive development, and high morbidity rates in children worldwide. Enterotoxigenic Escherichia coli (ETEC) is a major contributor to this diarrheal disease burden. ETEC cause disease in the small intestine by means of colonization factors and by production of a heat-labile enterotoxin (LT) and/or a small non-immunogenic heat-stable enterotoxin (ST). Overall, the majority of ETEC produce both ST and LT. LT induces secretion via an enzymatically active A-subunit (LT-A) and a pentameric, cell-binding B-subunit (LT-B). The importance of anti-LT antibodies has been demonstrated in multiple clinical and epidemiological studies, and a number of potential ETEC vaccine candidates have included LT-B as an important immunogen. However, there is limited information about the potential contribution of LT-A to development of protective immunity. In the current study, we evaluate the immune response against the A-subunit of LT as well as the A-subunit's potential as a protective antigen when administered alone or in combination with the B-subunit of LT. We evaluated human sera from individuals challenged with a prototypic wild-type ETEC strain as well as sera from individuals living in an ETEC endemic area for the presence of anti-LT, anti-LT-A and anti-LT-B antibodies. In both cases, a significant number of individuals intentionally or endemically infected with ETEC developed antibodies against both LT subunits. In addition, animals immunized with the recombinant proteins developed robust antibody responses that were able to neutralize the enterotoxic and cytotoxic effects of native LT by blocking binding and entry into cells (anti-LT-B) or the intracellular enzymatic activity of the toxin (anti-LT-A). Moreover, antibodies to both LT subunits acted synergistically to neutralize the holotoxin when combined. Taken together, these data support the inclusion of both LT-A and LT-B in prospective vaccines

  3. Characterization of heat-labile toxin-subunit B from Escherichia coli by liquid chromatography-electrospray ionization-mass spectrometry and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

    PubMed

    Sospedra, I; De Simone, C; Soriano, J M; Mañes, J; Ferranti, P; Ritieni, A

    2012-11-01

    The possibilities of characterizing the heat-labile enterotoxin (LT) of enterotoxigenic Escherichia coli (ETEC) by liquid chromatography electrospray mass spectrometry (LC/ESI-MS) and matrix-assisted laser desorption with time-of-flight mass spectrometry (MALDI-TOF-MS) were investigated. The B subunit from recombinant E. coli (expression in Pichia pastoris) can be detected by LC/ESI-MS expressed in P. pastoris and the charge envelope signals can be observed; LC/ESI-MS and MALDI-TOF-MS analysis allowed the acquisition of labile toxin subunit B (LTB) molecular weight and preliminary structural characterization of LTB toxin. MALDI-TOF analysis after reduction and alkylation of the protein evidenced the presence of one disulfide bond in the structure of the protein. Confirmatory analysis was carried out by detection of most of the tryptic fragments of the B subunit by MALDI-TOF-MS, obtaining total coverage of the protein sequence. Possible biovariations in the toxin can mostly be determined by sequencing, where an increase of molecular mass in the N-terminal side of the protein was identified. This modification may be due to an O-GlcNAc-1-phosphorylation. PMID:22921353

  4. Genetic fusions of a CFA/I/II/IV MEFA (multiepitope fusion antigen) and a toxoid fusion of heat-stable toxin (STa) and heat-labile toxin (LT) of enterotoxigenic Escherichia coli (ETEC) retain broad anti-CFA and antitoxin antigenicity.

    PubMed

    Ruan, Xiaosai; Sack, David A; Zhang, Weiping

    2015-01-01

    Immunological heterogeneity has long been the major challenge in developing broadly effective vaccines to protect humans and animals against bacterial and viral infections. Enterotoxigenic Escherichia coli (ETEC) strains, the leading bacterial cause of diarrhea in humans, express at least 23 immunologically different colonization factor antigens (CFAs) and two distinct enterotoxins [heat-labile toxin (LT) and heat-stable toxin type Ib (STa or hSTa)]. ETEC strains expressing any one or two CFAs and either toxin cause diarrhea, therefore vaccines inducing broad immunity against a majority of CFAs, if not all, and both toxins are expected to be effective against ETEC. In this study, we applied the multiepitope fusion antigen (MEFA) strategy to construct ETEC antigens and examined antigens for broad anti-CFA and antitoxin immunogenicity. CFA MEFA CFA/I/II/IV [CVI 2014, 21(2):243-9], which carried epitopes of seven CFAs [CFA/I, CFA/II (CS1, CS2, CS3), CFA/IV (CS4, CS5, CS6)] expressed by the most prevalent and virulent ETEC strains, was genetically fused to LT-STa toxoid fusion monomer 3xSTaA14Q-dmLT or 3xSTaN12S-dmLT [IAI 2014, 82(5):1823-32] for CFA/I/II/IV-STaA14Q-dmLT and CFA/I/II/IV-STaN12S-dmLT MEFAs. Mice intraperitoneally immunized with either CFA/I/II/IV-STa-toxoid-dmLT MEFA developed antibodies specific to seven CFAs and both toxins, at levels equivalent or comparable to those induced from co-administration of the CFA/I/II/IV MEFA and toxoid fusion 3xSTaN12S-dmLT. Moreover, induced antibodies showed in vitro adherence inhibition activities against ETEC or E. coli strains expressing these seven CFAs and neutralization activities against both toxins. These results indicated CFA/I/II/IV-STa-toxoid-dmLT MEFA or CFA/I/II/IV MEFA combined with 3xSTaN12S-dmLT induced broadly protective anti-CFA and antitoxin immunity, and suggested their potential application in broadly effective ETEC vaccine development. This MEFA strategy may be generally used in multivalent

  5. Genetic fusions of a CFA/I/II/IV MEFA (multiepitope fusion antigen) and a toxoid fusion of heat-stable toxin (STa) and heat-labile toxin (LT) of enterotoxigenic Escherichia coli (ETEC) retain broad anti-CFA and antitoxin antigenicity.

    PubMed

    Ruan, Xiaosai; Sack, David A; Zhang, Weiping

    2015-01-01

    Immunological heterogeneity has long been the major challenge in developing broadly effective vaccines to protect humans and animals against bacterial and viral infections. Enterotoxigenic Escherichia coli (ETEC) strains, the leading bacterial cause of diarrhea in humans, express at least 23 immunologically different colonization factor antigens (CFAs) and two distinct enterotoxins [heat-labile toxin (LT) and heat-stable toxin type Ib (STa or hSTa)]. ETEC strains expressing any one or two CFAs and either toxin cause diarrhea, therefore vaccines inducing broad immunity against a majority of CFAs, if not all, and both toxins are expected to be effective against ETEC. In this study, we applied the multiepitope fusion antigen (MEFA) strategy to construct ETEC antigens and examined antigens for broad anti-CFA and antitoxin immunogenicity. CFA MEFA CFA/I/II/IV [CVI 2014, 21(2):243-9], which carried epitopes of seven CFAs [CFA/I, CFA/II (CS1, CS2, CS3), CFA/IV (CS4, CS5, CS6)] expressed by the most prevalent and virulent ETEC strains, was genetically fused to LT-STa toxoid fusion monomer 3xSTaA14Q-dmLT or 3xSTaN12S-dmLT [IAI 2014, 82(5):1823-32] for CFA/I/II/IV-STaA14Q-dmLT and CFA/I/II/IV-STaN12S-dmLT MEFAs. Mice intraperitoneally immunized with either CFA/I/II/IV-STa-toxoid-dmLT MEFA developed antibodies specific to seven CFAs and both toxins, at levels equivalent or comparable to those induced from co-administration of the CFA/I/II/IV MEFA and toxoid fusion 3xSTaN12S-dmLT. Moreover, induced antibodies showed in vitro adherence inhibition activities against ETEC or E. coli strains expressing these seven CFAs and neutralization activities against both toxins. These results indicated CFA/I/II/IV-STa-toxoid-dmLT MEFA or CFA/I/II/IV MEFA combined with 3xSTaN12S-dmLT induced broadly protective anti-CFA and antitoxin immunity, and suggested their potential application in broadly effective ETEC vaccine development. This MEFA strategy may be generally used in multivalent

  6. LT-IIb(T13I), a non-toxic type II heat-labile enterotoxin, augments the capacity of a ricin toxin subunit vaccine to evoke neutralizing antibodies and protective immunity.

    PubMed

    Greene, Christopher J; Chadwick, Chrystal M; Mandell, Lorrie M; Hu, John C; O'Hara, Joanne M; Brey, Robert N; Mantis, Nicholas J; Connell, Terry D

    2013-01-01

    Currently, there is a shortage of adjuvants that can be employed with protein subunit vaccines to enhance protection against biological threats. LT-IIb(T13I) is an engineered nontoxic derivative of LT-IIb, a member of the type II subfamily of heat labile enterotoxins expressed by Escherichia coli, that possesses potent mucosal adjuvant properties. In this study we evaluated the capacity of LT-IIb(T13I) to augment the potency of RiVax, a recombinant ricin toxin A subunit vaccine, when co-administered to mice via the intradermal (i.d.) and intranasal (i.n.) routes. We report that co-administration of RiVax with LT-IIb(T13I) by the i.d. route enhanced the levels of RiVax-specific serum IgG antibodies (Ab) and elevated the ratio of ricin-neutralizing to non-neutralizing Ab, as compared to RiVax alone. Protection against a lethal ricin challenge was also augmented by LT-IIb(T13I). While local inflammatory responses elicited by LT-IIb(T13I) were comparable to those elicited by aluminum salts (Imject®), LT-IIb(T13I) was more effective than aluminum salts at augmenting production of RiVax-specific serum IgG. Finally, i.n. administration of RiVax with LT-IIb(T13I) also increased levels of RiVax-specific serum and mucosal Ab and enhanced protection against ricin challenge. Collectively, these data highlight the potential of LT-IIb(T13I) as an effective next-generation i.d., or possibly i.n. adjuvant for enhancing the immunogenicity of subunit vaccines for biodefense.

  7. A tripartite fusion, FaeG-FedF-LT(192)A2:B, of enterotoxigenic Escherichia coli (ETEC) elicits antibodies that neutralize cholera toxin, inhibit adherence of K88 (F4) and F18 fimbriae, and protect pigs against K88ac/heat-labile toxin infection.

    PubMed

    Ruan, Xiaosai; Liu, Mei; Casey, Thomas A; Zhang, Weiping

    2011-10-01

    Enterotoxigenic Escherichia coli (ETEC) strains expressing K88 (F4) or F18 fimbriae and heat-labile (LT) and/or heat-stable (ST) toxins are the major cause of diarrhea in young pigs. Effective vaccines inducing antiadhesin (anti-K88 and anti-F18) and antitoxin (anti-LT and anti-ST) immunity would provide broad protection to young pigs against ETEC. In this study, we genetically fused nucleotides coding for peptides from K88ac major subunit FaeG, F18 minor subunit FedF, and LT toxoid (LT(192)) A2 and B subunits for a tripartite adhesin-adhesin-toxoid fusion (FaeG-FedF-LT(192)A2:B). This fusion was used for immunizations in mice and pigs to assess the induction of antiadhesin and antitoxin antibodies. In addition, protection by the elicited antiadhesin and antitoxin antibodies against a porcine ETEC strain was evaluated in a gnotobiotic piglet challenge model. The data showed that this FaeG-FedF-LT(192)A2:B fusion elicited anti-K88, anti-F18, and anti-LT antibodies in immunized mice and pigs. In addition, the anti-porcine antibodies elicited neutralized cholera toxin and inhibited adherence against both K88 and F18 fimbriae. Moreover, immunized piglets were protected when challenged with ETEC strain 30302 (K88ac/LT/STb) and did not develop clinical disease. In contrast, all control nonvaccinated piglets developed severe diarrhea and dehydration after being challenged with the same ETEC strain. This study clearly demonstrated that this FaeG-FedF-LT(192)A2:B fusion antigen elicited antibodies that neutralized LT toxin and inhibited the adherence of K88 and F18 fimbrial E. coli strains and that this fusion could serve as an antigen for vaccines against porcine ETEC diarrhea. In addition, the adhesin-toxoid fusion approach used in this study may provide important information for developing effective vaccines against human ETEC diarrhea. PMID:21813665

  8. Development and accuracy of quantitative real-time polymerase chain reaction assays for detection and quantification of enterotoxigenic Escherichia coli (ETEC) heat labile and heat stable toxin genes in travelers' diarrhea samples.

    PubMed

    Youmans, Bonnie P; Ajami, Nadim J; Jiang, Zhi-Dong; Petrosino, Joseph F; DuPont, Herbert L; Highlander, Sarah K

    2014-01-01

    Enterotoxigenic Escherichia coli (ETEC), the leading bacterial pathogen of travelers' diarrhea, is routinely detected by an established DNA hybridization protocol that is neither sensitive nor quantitative. Quantitative real-time polymerase chain reaction (qPCR) assays that detect the ETEC toxin genes eltA, sta1, and sta2 in clinical stool samples were developed and tested using donor stool inoculated with known quantities of ETEC bacteria. The sensitivity of the qPCR assays is 89%, compared with 22% for the DNA hybridization assay, and the limits of detection are 10,000-fold lower than the DNA hybridization assays performed in parallel. Ninety-three clinical stool samples, previously characterized by DNA hybridization, were tested using the new ETEC qPCR assays. Discordant toxin profiles were observed for 22 samples, notably, four samples originally typed as ETEC negative were ETEC positive. The qPCR assays are unique in their sensitivity and ability to quantify the three toxin genes in clinical stool samples.

  9. Immunological Study of the Heat-Labile Enterotoxins of Escherichia coli and Vibrio cholerae

    PubMed Central

    Gyles, Carlton L.

    1974-01-01

    Immunodiffusion experiments were conducted to associate a precipitin line with Escherichia coli heat-labile enterotoxin (LT). Wild strains of porcine and of human enteropathogenic E. coli as well as laboratory-derived enterotoxigenic variants of E. coli K-12 were used for LT antigen preparations. These were produced mainly by ultrafiltration and ammonium sulfate precipitation of broth culture supernatants. When antisera with anti-LT activity were reacted with antigen preparations from Ent+ and Ent− variants of E. coli K-12, a line “a” was given by Ent+ but not by Ent− preparations. Line “a” was removed by absorption of anti-LT serum with antigen preparation from an Ent+E. coli K-12, but was unaffected when the antigen preparation used to absorb the serum was from an Ent−E. coli K-12. A line identical to “a” was given by antigen preparations from wild strains of porcine enteropathogenic E. coli reacted with homologous or heterologous anti-LT sera. One human strain of enteropathogenic E. coli was shown to possess an antigen identical to that which gave rise to line “a.” To demonstrate this line it was necessary to use high concentrations of gammaglobulin and high concentrations of the crude antigen preparations. LT preparations reacted with anticholera toxin to give a line “c,” which showed a reaction of partial identity with line “b” produced by reaction of pure choleragenoid and anticholera toxin. Lines “a” and “c” gave reactions of identity. Images PMID:4206029

  10. Radiation-induced heat-labile sites that convert into DNA double-strand breaks

    NASA Technical Reports Server (NTRS)

    Rydberg, B.; Chatterjee, A. (Principal Investigator)

    2000-01-01

    The yield of DNA double-strand breaks (DSBs) in SV40 DNA irradiated in aqueous solution was found to increase by more than a factor of two as a result of postirradiation incubation of the DNA at 50 degrees C and pH 8.0 for 24 h. This is in agreement with data from studies performed at 37 degrees C that were published previously. Importantly, similar results were also obtained from irradiation of mammalian DNA in agarose plugs. These results suggest that heat-labile sites within locally multiply damaged sites are produced by radiation and are subsequently transformed into DSBs. Since incubation at 50 degrees C is typically employed for lysis of cells in commonly used pulsed-field gel assays for detection of DSBs in mammalian cells, the possibility that heat-labile sites are present in irradiated cells was also studied. An increase in the apparent number of DSBs as a function of lysis time at 50 degrees C was found with kinetics that was similar to that for irradiated DNA, although the magnitude of the increase was smaller. This suggests that heat-labile sites are also formed in the cell. If this is the case, a proportion of DSBs measured by the pulsed-field gel assays may occur during the lysis step and may not be present in the cell as breaks but as heat-labile sites. It is suggested that such sites consist mainly of heat-labile sugar lesions within locally multiply damaged sites. Comparing rejoining of DSBs measured with short and long lysis procedure indicates that the heat-labile sites are repaired with fast kinetics in comparison with repair of the bulk of DSBs.

  11. Role of trypsin-like cleavage at arginine 192 in the enzymatic and cytotonic activities of Escherichia coli heat-labile enterotoxin.

    PubMed Central

    Grant, C C; Messer, R J; Cieplak, W

    1994-01-01

    Previous studies of cholera toxin and Escherichia coli heat-labile enterotoxin have suggested that proteolytic cleavage plays an important role in the expression of ADP-ribosyltransferase activity and toxicity. Specifically, several studies have implicated a trypsin-like cleavage at arginine 192, which lies within an exposed region subtended by a disulfide bond in the intact A subunit, in toxicity. To investigate the role of this modification in the enzymatic and cytotonic properties of heat-labile enterotoxin, the response of purified, recombinant A subunit to tryptic activation and the effect of substituting arginine 192 with glycine on the activities of the holotoxin were examined. The recombinant A subunit of heat-labile enterotoxin exhibited significant levels of ADP-ribosyltransferase activity that were only nominally increased (approximately twofold) by prior limited trypsinolysis. The enzymatic activity also did not appear to be affected by auto-ADP-ribosylation that occurs during the high-level synthesis of the recombinant A subunit in E. coli. A mutant form of the holotoxin containing the arginine 192-to-glycine substitution exhibited levels of cytotonic activity for CHO cells that were similar to that of the untreated, wild-type holotoxin but exhibited a marked delay in the ability to increase intracellular levels of cyclic AMP in Caco-2 cells. The results indicate that trypsin-like cleavage of the A subunit of E. coli heat-labile enterotoxin at arginine 192 is not requisite to the expression of enzymatic activity by the A subunit and further reveal that this modification, although it enhances the biological and enzymatic activities of the toxin, is not absolutely required for the enterotoxin to elicit cytotonic effects. Images PMID:7927684

  12. Simultaneous Exposure to Escherichia coli Heat-Labile and Heat-Stable Enterotoxins Increases Fluid Secretion and Alters Cyclic Nucleotide and Cytokine Production by Intestinal Epithelial Cells

    PubMed Central

    Read, Lisa T.; Hahn, Rachel W.; Thompson, Carli C.; Bauer, David L.; Norton, Elizabeth B.

    2014-01-01

    Enterotoxigenic Escherichia coli (ETEC) is a significant cause of diarrheal disease and death, especially in children in developing countries. ETEC causes disease by colonizing the small intestine and producing heat-labile toxin (LT), heat-stable toxin (ST), or both LT and ST (LT+ST). The majority of ETEC strains produce both ST and LT. Despite the prevalence of LT+ST-producing organisms, few studies have examined the physiologic or immunologic consequences of simultaneous exposure to these two potent enterotoxins. In the current report, we demonstrate that when LT and ST are both present, they increase water movement into the intestinal lumen over and above the levels observed with either toxin alone. As expected, cultured intestinal epithelial cells increased their expression of intracellular cyclic GMP (cGMP) when treated with ST and their expression of intracellular cyclic AMP (cAMP) when treated with LT. When both toxins were present, cGMP levels but not cAMP levels were synergistically elevated compared with the levels of expression caused by the corresponding single-toxin treatment. Our data also demonstrate that the levels of inflammatory cytokines produced by intestinal epithelial cells in response to LT are significantly reduced in animals exposed to both enterotoxins. These findings suggest that there may be complex differences between the epithelial cell intoxication and, potentially, secretory outcomes induced by ETEC strains expressing LT+ST compared with strains that express LT or ST only. Our results also reveal a novel mechanism wherein ST production may reduce the hosts' ability to mount an effective innate or adaptive immune response to infecting organisms. PMID:25287923

  13. Heat-labile- and heat-stable-toxoid fusions (LTR₁₉₂G-STaP₁₃F) of human enterotoxigenic Escherichia coli elicit neutralizing antitoxin antibodies.

    PubMed

    Liu, Mei; Ruan, Xiaosai; Zhang, Chengxian; Lawson, Steve R; Knudsen, David E; Nataro, James P; Robertson, Donald C; Zhang, Weiping

    2011-10-01

    Enterotoxigenic Escherichia coli (ETEC) strains are a major cause of diarrheal disease in humans and animals. Adhesins and enterotoxins, including heat-labile (LT) and heat-stable (STa) toxins, are the key virulence factors. Antigenic adhesin and LT antigens have been used in developing vaccines against ETEC diarrhea. However, STa has not been included because of its poor immunogenicity and potent toxicity. Our recent study showed that porcine-type STa toxoids became immunogenic and elicited neutralizing anti-STa antibodies after being genetically fused to a full-length porcine-type LT toxoid, LT(R₁₉₂G) (W. Zhang et al., Infect. Immun. 78:316-325, 2010). In this study, we mutated human-type LT and STa genes, which are highly homologous to porcine-type toxin genes, for a full-length LT toxoid (LT(R₁₉₂)) and a full-length STa toxoid (STa(P₁₃F)) and genetically fused them to produce LT₁₉₂-STa₁₃ toxoid fusions. Mice immunized with LT₁₉₂-STa₁₃ fusion antigens developed anti-LT and anti-STa IgG (in serum and feces) and IgA antibodies (in feces). Moreover, secretory IgA antibodies from immunized mice were shown to neutralize STa and cholera toxins in T-84 cells. In addition, we fused the STa₁₃ toxoid at the N terminus and C terminus, between the A1 and A2 peptides, and between the A and B subunits of LT₁₉₂ to obtain different fusions in order to explore strategies for enhancing STa immunogenicity. This study demonstrated that human-type LT₁₉₂-STa₁₃ fusions induce neutralizing antitoxin antibodies and provided important information for developing toxoid vaccines against human ETEC diarrhea. PMID:21788385

  14. Type II Heat-Labile Enterotoxins from 50 Diverse Escherichia coli Isolates Belong Almost Exclusively to the LT-IIc Family and May Be Prophage Encoded

    PubMed Central

    Jobling, Michael G.; Holmes, Randall K.

    2012-01-01

    Some enterotoxigenic Escherichia coli (ETEC) produce a type II heat-labile enterotoxin (LT-II) that activates adenylate cyclase in susceptible cells but is not neutralized by antisera against cholera toxin or type I heat-labile enterotoxin (LT-I). LT-I variants encoded by plasmids in ETEC from humans and pigs have amino acid sequences that are ≥95% identical. In contrast, LT-II toxins are chromosomally encoded and are much more diverse. Early studies characterized LT-IIa and LT-IIb variants, but a novel LT-IIc was reported recently. Here we characterized the LT-II encoding loci from 48 additional ETEC isolates. Two encoded LT-IIa, none encoded LT-IIb, and 46 encoded highly related variants of LT-IIc. Phylogenetic analysis indicated that the predicted LT-IIc toxins encoded by these loci could be assigned to 6 subgroups. The loci corresponding to individual toxins within each subgroup had DNA sequences that were more than 99% identical. The LT-IIc subgroups appear to have arisen by multiple recombinational events between progenitor loci encoding LT-IIc1- and LT-IIc3-like variants. All loci from representative isolates encoding the LT-IIa, LT-IIb, and each subgroup of LT-IIc enterotoxins are preceded by highly-related genes that are between 80 and 93% identical to predicted phage lysozyme genes. DNA sequences immediately following the B genes differ considerably between toxin subgroups, but all are most closely related to genomic sequences found in predicted prophages. Together these data suggest that the LT-II loci are inserted into lambdoid type prophages that may or may not be infectious. These findings raise the possibility that production of LT-II enterotoxins by ETEC may be determined by phage conversion and may be activated by induction of prophage, in a manner similar to control of production of Shiga-like toxins by converting phages in isolates of enterohemmorhagic E. coli. PMID:22242186

  15. Hereditary heat-labile hexosaminidase B: its implication for recognizing Tay-Sachs genotypes.

    PubMed

    Navon, R; Nutman, J; Kopel, R; Gaber, L; Gadoth, N; Goldman, B; Nitzan, M

    1981-11-01

    Two pairs of alleles, at the two loci of hexosaminidase (HEX), were found to segregate in an Arab inbred family: the normal and the mutant Tay-Sachs (TSD) alleles of HEX A, and the normal and a mutant allele of HEX B. Since the mutant HEX B is heat labile, no reliable identification of TSD genotypes can be obtained in its presence, as long as the proportions of HEX A and B are estimated by the routinely used heat-inactivation method. The genotypes may be correctly identified in such cases by separation of the two isoenzymes on ion-exchange chromatography, estimating their individual activities, and calculating the ratio between them. Of the nine genotype combinations possible with these two pairs of alleles, five have been identified in the reported family by this procedure. PMID:6459736

  16. Heat-labile enterotoxigenic Escherichia coli and intestinal protozoa in asymptomatic travellers.

    PubMed

    Echeverria, P; Cross, J H

    1977-12-01

    Thirty-two asymptomatic travellers who had recently journeyed in the Near, Middle, and Far East and had experienced a high incidence of diarrhoeal disease were screened for heat-labile enterotoxigenic Escherichia coli (ent+ E. coli) and other bacterial and parasitic pathogens. Six percent were colonized with ent+ E. coli and while other bacterial pathogens were not found, the intestinal protozoa Giardia lamblia (13%), Entamoeba histolytica (6%), Entamoeba coli (6%), Endolimax nana (6%), and Entamoeba hartmanni (3%) were detected in the stools. Ent+ E. coli, G. lamblia and E. histolytica should be considered in the differential diagnosis of gastrointestinal disease in travellers returning from the Orient. Furthermore, these travellers may be a potential source for the introduction of ent+ E. coli into communities where such organisms are relatively rare. PMID:351820

  17. Oral immunization of mice with attenuated Salmonella enteritidis containing a recombinant plasmid which codes for production of the B subunit of heat-labile Escherichia coli enterotoxin.

    PubMed Central

    Clements, J D; Lyon, F L; Lowe, K L; Farrand, A L; el-Morshidy, S

    1986-01-01

    We used Salmonella enteritidis serotype dublin strain SL1438, a nonreverting, aromatic-dependent, histidine-requiring mutant, as a recipient for a recombinant plasmid coding for production of the nontoxic B subunit of the heat-labile Escherichia coli enterotoxin. The S. enteritidis derivative EL23 produced heat-labile enterotoxin subunit B that was indistinguishable from heat-labile enterotoxin subunit B produced by strains of E. coli or Salmonella typhi harboring the same plasmid. Mice immunized orally with strain EL23 developed progressively increasing mucosal and serum antibody responses to both heat-labile enterotoxin subunit B and to the lipopolysaccharide of the vaccine strain. The mucosal antibody response was shown to be immunoglobulin A specific and to be capable of neutralizing the biological activities of both E. coli heat-labile enterotoxin and cholera enterotoxin in vitro. Images PMID:3527989

  18. Evaluation of a ganglioside immunosorbent assay for detection of Escherichia coli heat-labile enterotoxin.

    PubMed

    Bäck, E; Svennerholm, A M; Holmgren, J; Möllby, R

    1979-12-01

    The GM1 ganglioside enzyme-linked immunosorbent assay (GM1-ELISA), an immunological method for detection of Escherichia coli heat-labile enterotoxin (LT), was quantitatively and qualitatively compared with the conventional adrenal cell test for the identification of LT-producing strains. A micromodification model of the assay was developed. Enterotoxin preparations from 120 E. coli isolates from individuals with diarrhea, which had been previously shown to be enterotoxigenic by the adrenal cell test, and from 44 control strains of E. coli were compared in parallel by the two methods. Quantitatively the covariation of the enterotoxin titers was highly significant (RS = 0.98, P less than 0.001), the GM1-ELISA being somewhat more sensitive than the adrenal cell test. The methodological error was less than 5% in both tests. Qualitatively the overall agreement for positive and negative reactions for the two methods was 89%. The GM1-ELISA is practical for routine use in the diagnosis of enterotoxigenic E. coli, especially in laboratories without facilities for cell culture.

  19. Heat-labile enterotoxin of Escherichia coli promotes intestinal colonization of Salmonella enterica.

    PubMed

    Verbrugghe, Elin; Van Parys, Alexander; Leyman, Bregje; Boyen, Filip; Arnouts, Sven; Lundberg, Urban; Ducatelle, Richard; Van den Broeck, Wim; Yekta, Maryam Atef; Cox, Eric; Haesebrouck, Freddy; Pasmans, Frank

    2015-12-01

    Enterotoxigenic Escherichia coli (ETEC) is an important cause of infantile and travellers' diarrhoea, which poses a serious health burden, especially in developing countries. In addition, ETEC bacteria are a major cause of illness and death in neonatal and recently weaned pigs. The production of a heat-labile enterotoxin (LT) promotes the colonization and pathogenicity of ETEC and may exacerbate co-infections with other enteric pathogens such as Salmonella enterica. We showed that the intraintestinal presence of LT dramatically increased the intestinal Salmonella Typhimurium load in experimentally inoculated pigs. This could not be explained by direct alteration of the invasion or survival capacity of Salmonella in enterocytes, in vitro. However, we demonstrated that LT affects the enteric mucus layer composition in a mucus-secreting goblet cell line by significantly decreasing the expression of mucin 4. The current results show that LT alters the intestinal mucus composition and aggravates a Salmonella Typhimurium infection, which may result in the exacerbation of the diarrhoeal illness. PMID:26616654

  20. Expression of functional pentameric heat-labile enterotoxin B subunit of Escherichia coli in Saccharomyces cerevisiae.

    PubMed

    Lim, Jung-Gu; Kim, Jung-Ae; Chung, Hea-Jong; Kim, Tae-Geum; Kim, Jung-Mi; Lee, Kyung-Ryul; Park, Seung-Moon; Yang, Moon-Sik; Kim, Dae-Hyuk

    2009-05-01

    Although the Escherichia coli heat-labile enterotoxin B subunit (LTB) has already been expressed in several different systems, including prokaryotic and eukaryotic organisms, studies regarding the synthesis of LTB into oligomeric structures of pentameric size in the budding yeast Saccharomyces cerevisiae have been limited. Therefore, this study used a functional signal peptide of the amylase 1A protein from rice to direct the yeast-expressed LTB towards the endoplasmic reticulum to oligomerize with the expected pentameric size. The expression and assembly of the recombinant LTB were confirmed in both the cell-free extract and culture media of the recombinant strain using a Western blot analysis. The binding of the LTB pentamers to intestinal epithelial cell membrane glycolipid receptors was further verified using a GM1-ganglioside enzyme-linked immunosorbent assay (GM1-ELISA). On the basis of the GM1-ELISA results, pentameric LTB proteins comprised approximately 0.5-2.0% of the total soluble proteins, and the maximum quantity of secreted LTB was estimated to be 3 mg/l after a 3-day cultivation period. Consequently, the synthesis of LTB monomers and their assembly into biologically active oligomers in a recombinant S. cerevisiae strain demonstrated the feasibility of using a GRAS microorganism-based adjuvant, as well as the development of carriers against mucosal disease. PMID:19494699

  1. Phospholipase C (heat-labile hemolysin) of Pseudomonas aeruginosa: purification and preliminary characterization.

    PubMed Central

    Berka, R M; Vasil, M L

    1982-01-01

    Phospholipase C (heat-labile hemolysin) was purified from Pseudomonas aeruginosa culture supernatants to near homogeneity by ammonium sulfate precipitation followed by a novel application of DEAE-Sephacel chromatography. Enzymatic activity remained associated with DEAE-Sephacel even in the presence of 1 M NaCl, but was eluted with a linear gradient of 0 to 5% tetradecyltrimethylammonium bromide. Elution from DEAE-Sephacel was also obtained with 2% lysophosphatidylcholine, and to a lesser extent with 2% phosphorylcholine, but not at all with choline. The enzyme was highly active toward phospholipids possessing substituted ammonium groups (e.g., phosphatidycholine, lysophosphatidylcholine, and sphingomyelin); however, it had little if any activity toward phospholipids lacking substituted ammonium groups (e.g., phosphatidylethanolamine, phosphatidylserine, and phosphaditylglycerol). Collectively, these data suggest that phospholipase C from P. aeruginosa exhibits high affinity for substituted ammonium groups, but requires an additional hydrophobic moiety for optimum binding. The specific activity of the purified enzyme preparation increased 1,900-fold compared with that of culture supernatants. The molecular weight of the phospholipase C was estimated to be 78,000 by both sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Sephacryl S-200 column chromatography and was 76,000 by high-performance size exclusion chromatography. The isoelectric point was 5.5. Amino acid analysis showed that phospholipase C was rich in glycine, serine, threonine, aspartyl, glutamyl, and aromatic amino acids, but was cystine free. Images PMID:6811552

  2. Secretory IgA-mediated protection against V. cholerae and heat-labile enterotoxin-producing enterotoxigenic Escherichia coli by rice-based vaccine.

    PubMed

    Tokuhara, Daisuke; Yuki, Yoshikazu; Nochi, Tomonori; Kodama, Toshio; Mejima, Mio; Kurokawa, Shiho; Takahashi, Yuko; Nanno, Masanobu; Nakanishi, Ushio; Takaiwa, Fumio; Honda, Takeshi; Kiyono, Hiroshi

    2010-05-11

    Cholera and enterotoxigenic Escherichia coli (ETEC) are among the most common causes of acute infantile gastroenteritis globally. We previously developed a rice-based vaccine that expressed cholera toxin B subunit (MucoRice-CTB) and had the advantages of being cold chain-free and providing protection against cholera toxin (CT)-induced diarrhea. To advance the development of MucoRice-CTB for human clinical application, we investigated whether the CTB-specific secretory IgA (SIgA) induced by MucoRice-CTB gives longstanding protection against diarrhea induced by Vibrio cholerae and heat-labile enterotoxin (LT)-producing ETEC (LT-ETEC) in mice. Oral immunization with MucoRice-CTB stored at room temperature for more than 3 y provided effective SIgA-mediated protection against CT- or LT-induced diarrhea, but the protection was impaired in polymeric Ig receptor-deficient mice lacking SIgA. The vaccine gave longstanding protection against CT- or LT-induced diarrhea (for > or = 6 months after primary immunization), and a single booster immunization extended the duration of protective immunity by at least 4 months. Furthermore, MucoRice-CTB vaccination prevented diarrhea in the event of V. cholerae and LT-ETEC challenges. Thus, MucoRice-CTB is an effective long-term cold chain-free oral vaccine that induces CTB-specific SIgA-mediated longstanding protection against V. cholerae- or LT-ETEC-induced diarrhea.

  3. Contents of Highly Labile Trace Elements in H4-6 Chondrite Falls Are Not Affected by Post-Accretionary Heating

    NASA Astrophysics Data System (ADS)

    Wolf, S. F.; Lipschutz, M. E.

    1999-03-01

    Contents of volatile trace elements in H4-6 chondrites were established during nebular condensation and accretion and the most thermally labile of these were unaffected by metamorphism of their parent bodies, shock heating or close solar approach.

  4. Induction of heat-labile sites in DNA of mammalian cells by the antitumor alkylating drug CC-1065

    SciTech Connect

    Zsido, T.J.; Woynarowski, J.M.; Baker, R.M.; Gawron, L.S.; Beerman, T.A. )

    1991-04-16

    CC-1065 is a very potent antitumor antibiotic capable of covalent and noncovalent binding to the minor groove of naked DNA. Upon thermal treatment, covalent adducts formed between CC-1065 and DNA generate strand break. The authors have shown that this molecular damage can be detected following CC-1065 treatment of mammalian whole cells. Using alkaline sucrose gradient analysis, They observe thermally induced breakage of ({sup 14}C)thymidine-prelabeled DNA from drug-treated African green monkey kidney BSC-1 cells. Very little damage to cellular DNA by CC-1065 can be detected without first heating the drug-treated samples. CC-1065 can also generate heat-labile sites within DNA during cell lysis and heating, subsequent to the exposure of cells to drug, suggesting that a pool of free and noncovalently bound drug is available for posttreatment adduct formation. This effect was controlled for by mixing ({sup 3}H)thymidine-labeled untreated cells with the ({sup 14}C)thymidine-labeled drug-treated samples. The lowest drug dose at which heat-labile sites were detected was 3 nM CC-1065 (3 single-stranded breaks/10{sup 6} base pairs). This concentration reduced survival of BSC-1 cells to 0.1% in cytotoxicity assays. The generation of CC-1065-induced lesions in cellular DNA is time dependent (the frequency of lesions caused by a 60 nM treatment reaching a plateau at 2 h) and is not readily reversible. The results of this study demonstrate that CC-1065 does generate heat-labile sites with the cellular DNA of intact cells and suggest that a mechanism of cytotoxic action of CC-1065 involves formation of covalent adducts to DNA.

  5. Characterization of Receptor-Mediated Signal Transduction by Escherichia coli Type IIa Heat-Labile Enterotoxin in the Polarized Human Intestinal Cell Line T84

    PubMed Central

    Wimer-Mackin, Susan; Holmes, Randall K.; Wolf, Anne A.; Lencer, Wayne I.; Jobling, Michael G.

    2001-01-01

    Escherichia coli type IIa heat-labile enterotoxin (LTIIa) binds in vitro with highest affinity to ganglioside GD1b. It also binds in vitro with lower affinity to several other oligosialogangliosides and to ganglioside GM1, the functional receptor for cholera toxin (CT). In the present study, we characterized receptor-mediated signal transduction by LTIIa in the cultured T84 cell model of human intestinal epithelium. Wild-type LTIIa bound tightly to the apical surface of polarized T84 cell monolayers and elicited a Cl− secretory response. LTIIa activity, unlike CT activity, was not blocked by the B subunit of CT. Furthermore, an LTIIa variant with a T14I substitution in its B subunit, which binds in vitro to ganglioside GM1 but not to ganglioside GD1b, was unable to bind to intact T84 cells and did not elicit a Cl− secretory response. These findings show that ganglioside GM1 on T84 cells is not a functional receptor for LTIIa. The LTIIa receptor on T84 cells was inactivated by treatment with neuraminidase. Furthermore, LTIIa binding was blocked by tetanus toxin C fragment, which binds to gangliosides GD1b and GT1b. These findings support the hypothesis that ganglioside GD1b, or possibly a glycoconjugate with a GD1b-like oligosaccharide, is the functional receptor for LTIIa on T84 cells. The LTIIa-receptor complexes from T84 cells were associated with detergent-insoluble membrane microdomains (lipid rafts), extending the correlation between toxin binding to lipid rafts and toxin function that was previously established for CT. However, the extent of association with lipid rafts and the magnitude of the Cl− secretory response in T84 cells were less for LTIIa than for CT. These properties of LTIIa and the previous finding that enterotoxin LTIIb binds to T84 cells but does not associate with lipid rafts or elicit a Cl− secretory response may explain the low pathogenicity for humans of type II enterotoxin-producing isolates of E. coli. PMID:11705889

  6. Protective Mucosal Immunity to Ocular Herpes Simplex Virus Type 1 Infection in Mice by Using Escherichia coli Heat-Labile Enterotoxin B Subunit as an Adjuvant

    PubMed Central

    Richards, C. M.; Aman, A. T.; Hirst, T. R.; Hill, T. J.; Williams, N. A.

    2001-01-01

    The potential of nontoxic recombinant B subunits of cholera toxin (rCtxB) and its close relative Escherichia coli heat-labile enterotoxin (rEtxB) to act as mucosal adjuvants for intranasal immunization with herpes simplex virus type 1 (HSV-1) glycoproteins was assessed. Doses of 10 μg of rEtxB or above with 10 μg of HSV-1 glycoproteins elicited high serum and mucosal anti-HSV-1 titers comparable with that obtained using CtxB (10 μg) with a trace (0.5 μg) of whole toxin (Ctx-CtxB). By contrast, doses of rCtxB up to 100 μg elicited only meager anti-HSV-1 responses. As for Ctx-CtxB, rEtxB resulted in a Th2-biased immune response with high immunoglobulin G1 (IgG1)/IgG2a antibody ratios and production of interleukin 4 (IL-4) and IL-10 as well as gamma interferon by proliferating T cells. The protective efficacy of the immune response induced using rEtxB as an adjuvant was assessed following ocular challenge of immunized and mock-immunized mice. Epithelial disease was observed in both groups, but the immunized mice recovered by day 6 whereas mock-immunized mice developed more severe corneal disease leading to stromal keratitis. In addition, a significant reduction in the incidence of lid disease and zosteriform spread was observed in immunized animals and there was no encephalitis compared with 95% encephalitis in mock-immunized mice. The potential of such mucosal adjuvants for use in human vaccines against pathogens such as HSV-1 is discussed. PMID:11160664

  7. Toxins

    MedlinePlus

    Toxins are substances created by plants and animals that are poisonous to humans. Toxins also include some medicines that are helpful in small doses, but poisonous in large amounts. Most toxins that cause problems ...

  8. Activation of Escherichia coli heat-labile enterotoxins by native and recombinant adenosine diphosphate-ribosylation factors, 20-kD guanine nucleotide-binding proteins.

    PubMed Central

    Lee, C M; Chang, P P; Tsai, S C; Adamik, R; Price, S R; Kunz, B C; Moss, J; Twiddy, E M; Holmes, R K

    1991-01-01

    Escherichia coli heat-labile enterotoxins (LT) are responsible in part for "traveler's diarrhea" and related diarrheal illnesses. The family of LTs comprises two serogroups termed LT-I and LT-II; each serogroup includes two or more antigenic variants. The effects of LTs result from ADP ribosylation of Gs alpha, a stimulatory component of adenylyl cyclase; the mechanism of action is identical to that of cholera toxin (CT). The ADP-ribosyltransferase activity of CT is enhanced by 20-kD guanine nucleotide-binding proteins, known as ADP-ribosylation factors or ARFs. These proteins directly activate the CTA1 catalytic unit and stimulate its ADP ribosylation of Gs alpha, other proteins, and simple guanidino compounds (e.g., agmatine). Because of the similarities between CT and LTs, we investigated the effects of purified bovine brain ARF and a recombinant form of bovine ARF synthesized in Escherichia coli on LT activity. ARF enhanced the LT-I-, LT-IIa-, and LT-IIb-catalyzed ADP ribosylation of agmatine, as well as the auto-ADP ribosylation of the toxin catalytic unit. Stimulation of ADP-ribosylagmatine formation by LTs and CT in the presence of ARF was GTP dependent and enhanced by sodium dodecyl sulfate. With agmatine as substrate, LT-IIa and LT-IIb exhibited less than 1% the activity of CT and LT-Ih. CT and LTs catalyzed ADP-ribosyl-Gs alpha formation in a reaction dependent on ARF, GTP, and dimyristoyl phosphatidylcholine/cholate. With Gs alpha as substrate, the ADP-ribosyltransferase activities of the toxins were similar, although CT and LT-Ih appeared to be slightly more active than LT-IIa and LT-IIb. Thus, LT-IIa and LT-IIb appear to differ somewhat from CT and LT-Ih in substrate specificity. Responsiveness to stimulation by ARF, GTP, and phospholipid/detergent as well as the specificity of ADP-ribosyltransferase activity are functions of LTs from serogroups LT-I and LT-II that are shared with CT. Images PMID:1902492

  9. Towards Rational Design of a Toxoid Vaccine against the Heat-Stable Toxin of Escherichia coli.

    PubMed

    Taxt, Arne M; Diaz, Yuleima; Aasland, Rein; Clements, John D; Nataro, James P; Sommerfelt, Halvor; Puntervoll, Pål

    2016-04-01

    Enterotoxigenic Escherichia coli(ETEC) is an important cause of diarrheal disease and death in children <5 years old. ETEC strains that express the heat-stable toxin (ST), with or without the heat-labile toxin, are among the four most important diarrhea-causing pathogens. This makes ST an attractive target for an ETEC vaccine. An ST vaccine should be nontoxic and elicit an immune response that neutralizes native ST without cross-reacting with the human endogenous guanylate cyclase C receptor ligands. To identify variants of ST with no or low toxicity, we screened a library of all 361 possible single-amino-acid mutant forms of ST by using the T84 cell assay. Moreover, we identified mutant variants with intact epitopes by screening for the ability to bind neutralizing anti-ST antibodies. ST mutant forms with no or low toxicity and intact epitopes are termed toxoid candidates, and the top 30 candidates all had mutations of residues A14, N12, and L9. The identification of nontoxic variants of L9 strongly suggests that it is a novel receptor-interacting residue, in addition to the previously identified N12, P13, and A14 residues. The screens also allowed us to map the epitopes of three neutralizing monoclonal antibodies, one of which cross-reacts with the human ligand uroguanylin. The common dominant epitope residue for all non-cross-reacting antibodies was Y19. Our results suggest that it should be possible to rationally design ST toxoids that elicit neutralizing immune responses against ST with minimal risk of immunological cross-reactivity.

  10. Towards Rational Design of a Toxoid Vaccine against the Heat-Stable Toxin of Escherichia coli

    PubMed Central

    Taxt, Arne M.; Diaz, Yuleima; Aasland, Rein; Clements, John D.; Nataro, James P.; Sommerfelt, Halvor

    2016-01-01

    Enterotoxigenic Escherichia coli (ETEC) is an important cause of diarrheal disease and death in children <5 years old. ETEC strains that express the heat-stable toxin (ST), with or without the heat-labile toxin, are among the four most important diarrhea-causing pathogens. This makes ST an attractive target for an ETEC vaccine. An ST vaccine should be nontoxic and elicit an immune response that neutralizes native ST without cross-reacting with the human endogenous guanylate cyclase C receptor ligands. To identify variants of ST with no or low toxicity, we screened a library of all 361 possible single-amino-acid mutant forms of ST by using the T84 cell assay. Moreover, we identified mutant variants with intact epitopes by screening for the ability to bind neutralizing anti-ST antibodies. ST mutant forms with no or low toxicity and intact epitopes are termed toxoid candidates, and the top 30 candidates all had mutations of residues A14, N12, and L9. The identification of nontoxic variants of L9 strongly suggests that it is a novel receptor-interacting residue, in addition to the previously identified N12, P13, and A14 residues. The screens also allowed us to map the epitopes of three neutralizing monoclonal antibodies, one of which cross-reacts with the human ligand uroguanylin. The common dominant epitope residue for all non-cross-reacting antibodies was Y19. Our results suggest that it should be possible to rationally design ST toxoids that elicit neutralizing immune responses against ST with minimal risk of immunological cross-reactivity. PMID:26883587

  11. Repair of radiation-induced heat-labile sites is independent of DNA-PKcs, XRCC1 or PARP

    SciTech Connect

    Stenerlöw, Bo; Karlsson, Karin H.; Radulescu, Irina; Rydberg, Bjorn; Stenerlow, Bo

    2008-04-29

    Ionizing radiation induces a variety of different DNA lesions: in addition to the most critical DNA damage, the DSB, numerous base alterations, SSBs and other modifications of the DNA double-helix are formed. When several non-DSB lesions are clustered within a short distance along DNA, or close to a DSB, they may interfere with the repair of DSBs and affect the measurement of DSB induction and repair. We have previously shown that a substantial fraction of DSBs measured by pulsed-field gel electrophoresis (PFGE) are in fact due to heat-labile sites (HLS) within clustered lesions, thus reflecting an artifact of preparation of genomic DNA at elevated temperature. To further characterize the influence of HLS on DSB induction and repair, four human cell lines (GM5758, GM7166, M059K, U-1810) with apparently normal DSB rejoining were tested for bi-phasic rejoining after gamma irradiation. When heat-released DSBs were excluded from the measurements the fraction of fast rejoining decreased to less than 50% of the total. However, neither the half-times of the fast (t{sub 1/2} = 7-8 min) or slow (t{sub 1/2} = 2.5 h) DSB rejoining were changed significantly. At t=0 the heat-released DSBs accounted for almost 40% of the DSBs, corresponding to 10 extra DSB/cell/Gy in the initial DSB yield. These heat-released DSBs were repaired within 60-90 min in all tested cells, including M059K cells treated with wortmannin or DNA-PKcs defect M059J cells. Furthermore, cells lacking XRCC1 or Poly(ADP-ribose) polymerase-1 (PARP-1) rejoined both total DSBs and heat-released DSBs similar to normal cells. In summary, the presence of heat-labile sites have a substantial impact on DSB induction yields and DSB rejoining rates measured by pulsed-field gel electrophoresis, and HLS repair is independent of DNA-PKcs, XRCC1 and PARP.

  12. Toxicity and immunogenicity of Enterotoxigenic Escherichia coli heat-labile and heat-stable toxoid fusion 3xSTa(A14Q)-LT(S63K/R192G/L211A) in a murine model.

    PubMed

    Zhang, Chengxian; Knudsen, David E; Liu, Mei; Robertson, Donald C; Zhang, Weiping

    2013-01-01

    Diarrhea is the second leading cause of death to young children. Enterotoxigenic Escherichia coli (ETEC) are the most common bacteria causing diarrhea. Adhesins and enterotoxins are the virulence determinants in ETEC diarrhea. Adhesins mediate bacterial attachment and colonization, and enterotoxins including heat-labile (LT) and heat-stable type Ib toxin (STa) disrupt fluid homeostasis in host cells that leads to fluid hyper-secretion and diarrhea. Thus, adhesins and enterotoxins have been primarily targeted in ETEC vaccine development. A recent study reported toxoid fusions with STa toxoid (STa(P13F)) fused at the N- or C-terminus, or inside the A subunit of LT(R192G) elicited neutralizing antitoxin antibodies, and suggested application of toxoid fusions in ETEC vaccine development (Liu et al., Infect. Immun. 79:4002-4009, 2011). In this study, we generated a different STa toxoid (STa(A14Q)) and a triple-mutant LT toxoid (LT(S63K/R192G/L211A), tmLT), constructed a toxoid fusion (3xSTa(A14Q)-tmLT) that carried 3 copies of STa(A14Q) for further facilitation of anti-STa immunogenicity, and assessed antigen safety and immunogenicity in a murine model to explore its potential for ETEC vaccine development. Mice immunized with this fusion antigen showed no adverse effects, and developed antitoxin antibodies particularly through the IP route. Anti-LT antibodies were detected and were shown neutralizing against CT in vitro. Anti-STa antibodies were also detected in the immunized mice, and serum from the IP immunized mice neutralized STa toxin in vitro. Data from this study indicated that toxoid fusion 3xSTa(A14Q)-tmLT is safe and can induce neutralizing antitoxin antibodies, and provided helpful information for vaccine development against ETEC diarrhea. PMID:24146989

  13. Toxicity and immunogenicity of Enterotoxigenic Escherichia coli heat-labile and heat-stable toxoid fusion 3xSTa(A14Q)-LT(S63K/R192G/L211A) in a murine model.

    PubMed

    Zhang, Chengxian; Knudsen, David E; Liu, Mei; Robertson, Donald C; Zhang, Weiping

    2013-01-01

    Diarrhea is the second leading cause of death to young children. Enterotoxigenic Escherichia coli (ETEC) are the most common bacteria causing diarrhea. Adhesins and enterotoxins are the virulence determinants in ETEC diarrhea. Adhesins mediate bacterial attachment and colonization, and enterotoxins including heat-labile (LT) and heat-stable type Ib toxin (STa) disrupt fluid homeostasis in host cells that leads to fluid hyper-secretion and diarrhea. Thus, adhesins and enterotoxins have been primarily targeted in ETEC vaccine development. A recent study reported toxoid fusions with STa toxoid (STa(P13F)) fused at the N- or C-terminus, or inside the A subunit of LT(R192G) elicited neutralizing antitoxin antibodies, and suggested application of toxoid fusions in ETEC vaccine development (Liu et al., Infect. Immun. 79:4002-4009, 2011). In this study, we generated a different STa toxoid (STa(A14Q)) and a triple-mutant LT toxoid (LT(S63K/R192G/L211A), tmLT), constructed a toxoid fusion (3xSTa(A14Q)-tmLT) that carried 3 copies of STa(A14Q) for further facilitation of anti-STa immunogenicity, and assessed antigen safety and immunogenicity in a murine model to explore its potential for ETEC vaccine development. Mice immunized with this fusion antigen showed no adverse effects, and developed antitoxin antibodies particularly through the IP route. Anti-LT antibodies were detected and were shown neutralizing against CT in vitro. Anti-STa antibodies were also detected in the immunized mice, and serum from the IP immunized mice neutralized STa toxin in vitro. Data from this study indicated that toxoid fusion 3xSTa(A14Q)-tmLT is safe and can induce neutralizing antitoxin antibodies, and provided helpful information for vaccine development against ETEC diarrhea.

  14. Protective efficacy of a Mycoplasma pneumoniae P1C DNA vaccine fused with the B subunit of Escherichia coli heat-labile enterotoxin.

    PubMed

    Zhu, Cuiming; Wang, Shiping; Hu, Shihai; Yu, Minjun; Zeng, Yanhua; You, Xiaoxing; Xiao, Jinhong; Wu, Yimou

    2012-06-01

    In the present study, we investigated the immunomodulatory responses of a DNA vaccine constructed by fusing Mycoplasma pneumoniae P1 protein carboxy terminal region (P1C) with the Escherichia coli heat-labile toxin B subunit (LTB). BALB/c mice were immunized by intranasal inoculation with control DNAs, the P1C DNA vaccine or the LTB-P1C fusion DNA vaccine. Levels of the anti-M. pneumoniae antibodies and levels of interferon-γ and IL-4 in mice were increased significantly upon inoculation of the LTB-P1C fusion DNA vaccine when compared with the inoculation with P1C DNA vaccine. The LTB-P1C fusion DNA vaccine efficiently enhanced the M. pneumoniae-specific IgA and IgG levels. The IgG2a/IgG1 ratio was significantly higher in bronchoalveolar lavages fluid and sera from mice fusion with LTB and P1C than mice receiving P1C alone. When the mice were challenged intranasally with 10(7) CFU M. pneumoniae strain (M129), the LTB-P1C fusion DNA vaccine conferred significantly better protection than P1C DNA vaccine (P < 0.05), as suggested by the results, such as less inflammation, lower histopathological score values, lower detectable number of M. pneumoniae strain, and lower mortality of challenging from 5 × 10(8) CFU M. pneumoniae. These results indicated that the LTB-P1C fusion DNA vaccine efficiently improved protective efficacy against M. pneumoniae infection and effectively attenuated development of M. pneumoniae in mice.

  15. Cure of Trypanosoma musculi infection by heat-labile activity in immune plasma.

    PubMed

    Wechsler, D S; Kongshavn, P A

    1984-06-01

    Passive transfer of plasma from a mouse cured of parasitemia to a Trypanosoma musculi-infected host rapidly eliminates parasitemia; this curative activity, presumably mediated by an immunoglobulin, is sensitive to heat treatment (56 degrees C, 30 min). In addition, pretreatment with immune plasma, even after heat treatment, prevents the development of a patent parasitemia in a naive host (protective activity).

  16. Peracetic Acid: A Practical Agent for Sterilizing Heat-Labile Polymeric Tissue-Engineering Scaffolds

    PubMed Central

    Yoganarasimha, Suyog; Trahan, William R.; Best, Al M.; Bowlin, Gary L.; Kitten, Todd O.; Moon, Peter C.

    2014-01-01

    Advanced biomaterials and sophisticated processing technologies aim at fabricating tissue-engineering scaffolds that can predictably interact within a biological environment at the cellular level. Sterilization of such scaffolds is at the core of patient safety and is an important regulatory issue that needs to be addressed before clinical translation. In addition, it is crucial that meticulously engineered micro- and nano- structures are preserved after sterilization. Conventional sterilization methods involving heat, steam, and radiation are not compatible with engineered polymeric systems because of scaffold degradation and loss of architecture. Using electrospun scaffolds made from polycaprolactone, a low melting polymer, and employing spores of Bacillus atrophaeus as biological indicators, we compared ethylene oxide, autoclaving and 80% ethanol to a known chemical sterilant, peracetic acid (PAA), for their ability to sterilize as well as their effects on scaffold properties. PAA diluted in 20% ethanol to 1000 ppm or above sterilized electrospun scaffolds in 15 min at room temperature while maintaining nano-architecture and mechanical properties. Scaffolds treated with PAA at 5000 ppm were rendered hydrophilic, with contact angles reduced to 0°. Therefore, PAA can provide economical, rapid, and effective sterilization of heat-sensitive polymeric electrospun scaffolds that are used in tissue engineering. PMID:24341350

  17. Peracetic acid: a practical agent for sterilizing heat-labile polymeric tissue-engineering scaffolds.

    PubMed

    Yoganarasimha, Suyog; Trahan, William R; Best, Al M; Bowlin, Gary L; Kitten, Todd O; Moon, Peter C; Madurantakam, Parthasarathy A

    2014-09-01

    Advanced biomaterials and sophisticated processing technologies aim at fabricating tissue-engineering scaffolds that can predictably interact within a biological environment at the cellular level. Sterilization of such scaffolds is at the core of patient safety and is an important regulatory issue that needs to be addressed before clinical translation. In addition, it is crucial that meticulously engineered micro- and nano- structures are preserved after sterilization. Conventional sterilization methods involving heat, steam, and radiation are not compatible with engineered polymeric systems because of scaffold degradation and loss of architecture. Using electrospun scaffolds made from polycaprolactone, a low melting polymer, and employing spores of Bacillus atrophaeus as biological indicators, we compared ethylene oxide, autoclaving and 80% ethanol to a known chemical sterilant, peracetic acid (PAA), for their ability to sterilize as well as their effects on scaffold properties. PAA diluted in 20% ethanol to 1000 ppm or above sterilized electrospun scaffolds in 15 min at room temperature while maintaining nano-architecture and mechanical properties. Scaffolds treated with PAA at 5000 ppm were rendered hydrophilic, with contact angles reduced to 0°. Therefore, PAA can provide economical, rapid, and effective sterilization of heat-sensitive polymeric electrospun scaffolds that are used in tissue engineering. PMID:24341350

  18. Intranuclear delivery of an antiviral peptide mediated by the B subunit of Escherichia coli heat-labile enterotoxin

    PubMed Central

    Loregian, Arianna; Papini, Emanuele; Satin, Barbara; Marsden, Howard S.; Hirst, Timothy R.; Palù, Giorgio

    1999-01-01

    We report an intracellular peptide delivery system capable of targeting specific cellular compartments. In the model system we constructed a chimeric protein consisting of the nontoxic B subunit of Escherichia coli heat-labile enterotoxin (EtxB) fused to a 27-mer peptide derived from the DNA polymerase of herpes simplex virus 1. Viral DNA synthesis takes places in the nucleus and requires the interaction with an accessory factor, UL42, encoded by the virus. The peptide, designated Pol, is able to dissociate this interaction. The chimeric protein, EtxB-Pol, retained the functional properties of both EtxB and peptide components and was shown to inhibit viral DNA polymerase activity in vitro via disruption of the polymerase-UL42 complex. When added to virally infected cells, EtxB-Pol had no effect on adenovirus replication but specifically interfered with herpes simplex virus 1 replication. Further studies showed that the antiviral peptide localized in the nucleus, whereas the EtxB component remained associated with vesicular compartments. The results indicate that the chimeric protein entered through endosomal acidic compartments and that the Pol peptide was cleaved from the chimeric protein before being translocated into the nucleus. The system we describe is suitable for delivery of peptides that specifically disrupt protein–protein interactions and may be developed to target specific cellular compartments. PMID:10220447

  19. Search for heat-labile enterotoxigenic Escherichia coli in humans, livestock, food, and water in a community in the Philippines.

    PubMed

    Echeverria, P; Verhaert, L; Basaca-Sevilla, V; Banson, T; Cross, J; Orskov, F; Orskov, I

    1978-07-01

    Environmental sources of heat-labile enterotoxigenic Escherichia coli are unknown. The feces of 1,086 inhabitants (approximately 5%) of a small town in the Philippines, 28 pigs, and 10 water buffalo were cultured for enteric bacterial pathogens. Twenty-seven persons harbored pathogenic bacteria: five individuals had enterotoxigenic E. coli, 11 Salmonella species, nine Vibrio parahaemolyticus, one Shigella boydii, and one nonagglutinable Vibrio. Enterotoxigenic E. coli were isolated from two of 28 pigs and from one of 10 water buffalo. Cultures of 26 pieces of beef, 25 pieces of pork, and 52 leafy vegetables obtained from a community market failed to grow enterotoxigenic E. coli. None of 47 samples of contaminated surface water contained this pathogen. Serotypes of human and animal strains of enterotoxigenic E. coli were different, although E. coli O78:H12 isolated from a pig has previously been incriminated in human diarrheal disease. In this limited survey of a Philippine community, enterotoxigenic E. coli were isolated from humans and livestock. The possibility that enterotoxigenic E. coli infections are zoonotic warrants further investigation.

  20. The suppressive activities of six sources of medicinal ferns known as gusuibu on heat-labile enterotoxin-induced diarrhea.

    PubMed

    Chang, Hung-Chi; Chen, Jaw-Chyun; Yang, Jiun-Long; Tsay, Hsin-Sheng; Hsiang, Chien-Yun; Ho, Tin-Yun

    2014-02-18

    Diarrheal disease is one of the most important worldwide health problems. Enterotoxigenic Escherichia coli (ETEC) is the most frequently isolated enteropathogen in diarrheal diseases. In developing countries, a very large number of people, especially children, suffer from diarrhea. To combat this problem, World Health Organization has constituted the Diarrhea Diseases Control Program which guides studies on traditional medicinal practices and preventive measures. Gusuibu, a traditional folk medicine, has been claimed to heal certain types of diarrhea. However, so far no scientific study has been carried out on the anti-diarrheal mechanism of Gusiubu. The present study was performed to examine the suppressive activities of ethanol extracts of six sources of folk medicinal ferns used as Gusuibu on heat-labile enterotoxin (LT)-induced diarrhea. Inhibitory effects of six sources were evaluated on the ETEC LT subunit B (LTB) and monosialotetrahexosylganglioside (GMI) interaction by GM1-enzyme linked immunosorbent assay and patent mouse gut assay. Our results indicated that Drynaria fortunei had no anti-diarrheal effect, while, among the remaining five folk medicinal ferns, four belonging to family Davalliaceae had significant abilities on both the blocking of LTB and GM1 interaction and the inhibition of LT-induced diarrhea. In conclusion, these findings suggested the potential application of Gusuibu as an anti-diarrheal remedy.

  1. Toxin detection after storage or cultivation of enterotoxigenic with colicinogenic Escherichia coli: a possible mechanism for toxin-negative pools.

    PubMed Central

    Murray, B E; Seriwatana, J; Echeverria, P

    1981-01-01

    Of 100 non-enterotoxigenic Escherichia coli isolated from children with diarrhea in Bangkok, Thailand, 24 were found to produce colicin(s). Of these, 87% were active against one or more enterotoxigenic E. coli isolated from the same population. Storage of nine enterotoxigenic E. coli with known inhibitory colicin-producing E. coli in different proportions caused 51 of 96 pools to become negative in the suckling mouse assay (heat-stable toxin) and 17 of 52 to become negative in the Y-1 adrenal cell assay (heat-labile toxin). Cocultivation of the same strains, without prior storage, caused 12 of 96 pools to become negative for heat-stable toxin and 1 of 52 pools to become negative for heat-labile toxin. Storage or cultivation of E. coli in pools may cause negative results in the suckling mouse and Y-1 adrenal cell assays if any of the isolates in the pool produces colicin(s). PMID:7007422

  2. Inhibition of Cronobacter sakazakii by heat labile bacteriocins produced by probiotic LAB isolated from healthy infants.

    PubMed

    Awaisheh, Saddam S; Al-Nabulsi, Anas A; Osaili, Tareq M; Ibrahim, Salam; Holley, Richard

    2013-09-01

    Cronobacter sakazakii is an opportunistic pathogen that can cause bacteremia, meningitis, and necrotizing enterocolitis, most often in neonates with case-fatality rates that may reach 80%. The antimicrobial activity of lactic acid bacteria against a wide range of foodborne pathogens is well-established in different types of food products. The objective of the current study was to investigate the antibacterial activity of Lactobacillus acidophilus and L. casei isolated from feces of healthy infants against different strains of C. sakazakii in agar and a rehydrated infant milk formula (RIMF) model. The inhibition zones of C. sakazakii around L. acidophilus or L. casei ranged from 22 to 32 mm on eMan Rogosa Sharpe (MRS) agar under aerobic conditions, while a slight reduction in antibacterial activity was noted on modified MRS (0.2% glucose) under anaerobic conditions. It was observed that pH-neutralized cell-free supernatant (CFS) of L. acidophilus or L. casei was inhibitory against tested C. sakazakii strains. The inhibition zones of neutralized CFS were lower than the antibacterial activities of live cultures. The antibacterial activity of CFS was abolished when CFS from L. acidophilus or L. casei was heated at 60 or 80 °C for either 10 min or 2 h, or treated with trypsin or pepsin. This was considered strong evidence that the inhibition was due to the production of bacteriocins by L. casei and L. acidophilus. Both the CFS and active growing cells of L. casei and L. acidophilus were able to reduce the viability of C. sakazakii in the RIMF model. The results may extend the use of natural antimicrobials instead of conventional preservation methods to improve the safety of RIMF.

  3. Both enzymatic and non-enzymatic properties of heat-labile enterotoxin are responsible for LT-enhanced adherence of enterotoxigenic Escherichia coli to porcine IPEC-J2 cells.

    PubMed

    Fekete, Peter Z; Mateo, Kristina S; Zhang, Weiping; Moxley, Rodney A; Kaushik, Radhey S; Francis, David H

    2013-06-28

    Previous studies in piglets indicate that heat labile enterotoxin (LT) expression enhances intestinal colonization by K88 adhesin-producing enterotoxigenic Escherichia coli (ETEC) as wild-type ETEC adhered to intestinal epithelium in substantially greater numbers than did non-toxigenic constructs. Enzymatic activity of the toxin was also shown to contribute to the adhesion of ETEC and non-ETEC bacteria to epithelial cells in culture. To further characterize the contribution of LT to host cell adhesion, a nontoxigenic, K88-producing E. coli was transformed with either the gene encoding for LT holotoxin, a catalytically-attenuated form of the toxin [LT(R192G)], or LTB subunits, and resultant changes in bacterial adherence to IPEC-J2 porcine intestinal epithelial cells were measured. Strains expressing LT holotoxin or mutants were able to adhere in significantly higher numbers to IPEC-J2 cells than was an isogenic, toxin-negative construct. LT+ strains were also able to significantly block binding of a wild-type LT+ ETEC strain to IPEC-J2 cells. Adherence of isogenic strains to IPEC-J2 cells was unaltered by cycloheximide treatment, suggesting that LT enhances ETEC adherence to IPEC-J2 cells independent of host cell protein synthesis. However, pretreating IPEC-J2 cells with LT promoted adherence of negatively charged latex beads (a surrogate for bacteria which carry a negative change), which adherence was inhibited by cycloheximide, suggesting LT may induce a change in epithelial cell membrane potential. Overall, these data suggest that LT may enhance ETEC adherence by promoting an association between LTB and epithelial cells, and by altering the surface charge of the host plasma membrane to promote non-specific adherence.

  4. Both enzymatic and non-enzymatic properties of heat-labile enterotoxin are responsible for LT-enhanced adherence of enterotoxigenic Escherichia coli to porcine IPEC-J2 cells.

    PubMed

    Fekete, Peter Z; Mateo, Kristina S; Zhang, Weiping; Moxley, Rodney A; Kaushik, Radhey S; Francis, David H

    2013-06-28

    Previous studies in piglets indicate that heat labile enterotoxin (LT) expression enhances intestinal colonization by K88 adhesin-producing enterotoxigenic Escherichia coli (ETEC) as wild-type ETEC adhered to intestinal epithelium in substantially greater numbers than did non-toxigenic constructs. Enzymatic activity of the toxin was also shown to contribute to the adhesion of ETEC and non-ETEC bacteria to epithelial cells in culture. To further characterize the contribution of LT to host cell adhesion, a nontoxigenic, K88-producing E. coli was transformed with either the gene encoding for LT holotoxin, a catalytically-attenuated form of the toxin [LT(R192G)], or LTB subunits, and resultant changes in bacterial adherence to IPEC-J2 porcine intestinal epithelial cells were measured. Strains expressing LT holotoxin or mutants were able to adhere in significantly higher numbers to IPEC-J2 cells than was an isogenic, toxin-negative construct. LT+ strains were also able to significantly block binding of a wild-type LT+ ETEC strain to IPEC-J2 cells. Adherence of isogenic strains to IPEC-J2 cells was unaltered by cycloheximide treatment, suggesting that LT enhances ETEC adherence to IPEC-J2 cells independent of host cell protein synthesis. However, pretreating IPEC-J2 cells with LT promoted adherence of negatively charged latex beads (a surrogate for bacteria which carry a negative change), which adherence was inhibited by cycloheximide, suggesting LT may induce a change in epithelial cell membrane potential. Overall, these data suggest that LT may enhance ETEC adherence by promoting an association between LTB and epithelial cells, and by altering the surface charge of the host plasma membrane to promote non-specific adherence. PMID:23517763

  5. Relationship between heat-labile enterotoxin secretion capacity and virulence in wild type porcine-origin enterotoxigenic Escherichia coli strains.

    PubMed

    Wijemanne, Prageeth; Xing, Jun; Berberov, Emil M; Marx, David B; Francis, David H; Moxley, Rodney A

    2015-01-01

    Heat-labile enterotoxin (LT) is an important virulence factor secreted by some strains of enterotoxigenic Escherichia coli (ETEC). The prototypic human-origin strain H10407 secretes LT via a type II secretion system (T2SS). We sought to determine the relationship between the capacity to secrete LT and virulence in porcine-origin wild type (WT) ETEC strains. Sixteen WT ETEC strains isolated from cases of severe diarrheal disease were analyzed by GM1ganglioside enzyme-linked immunosorbent assay to measure LT concentrations in culture supernatants. All strains had detectable LT in supernatants by 2 h of culture and 1 strain, which was particularly virulent in gnotobiotic piglets (3030-2), had the highest LT secretion level all porcine-origin WT strains tested (P<0.05). The level of LT secretion (concentration in supernatants at 6-h culture) explained 92% of the variation in time-to-a-moribund-condition (R2 = 0.92, P<0.0001) in gnotobiotic piglets inoculated with either strain 3030-2, or an ETEC strain of lesser virulence (2534-86), or a non-enterotoxigenic WT strain (G58-1). All 16 porcine ETEC strains were positive by PCR analysis for the T2SS genes, gspD and gspK, and bioinformatic analysis of 4 porcine-origin strains for which complete genomic sequences were available revealed a T2SS with a high degree of homology to that of H10407. Maximum Likelihood phylogenetic trees constructed using T2SS genes gspC, gspD, gspE and homologs showed that strains 2534-86 and 3030-2 clustered together in the same clade with other porcine-origin ETEC strains in the database, UMNK88 and UMN18. Protein modeling of the ATPase gene (gspE) further revealed a direct relationship between the predicted ATP-binding capacities and LT secretion levels as follows: H10407, -8.8 kcal/mol and 199 ng/ml; 3030-2, -8.6 kcal/mol and 133 ng/ml; and 2534-86, -8.5 kcal/mol and 80 ng/ml. This study demonstrated a direct relationship between predicted ATP-binding capacity of GspE and LT secretion, and

  6. Characterization of two different toxins of Wickerhamomyces anomalus (Pichia anomala) VKM Y-159.

    PubMed

    Farkas, Z; Márki-Zay, J; Kucsera, Judit; Vágvölgyi, Cs; Golubev, W I; Pfeiffer, Ilona

    2012-06-01

    Wickerhamomyces anomalus VKM Y-159 strain produces two types of toxin designated as WAKT a and WAKT b, encoded by chromosomal genes. The WAKT a toxin is heat-labile, pronase sensitive acting in pH range 3-4 affecting on several yeasts including pathogenic Candida species while the WAKT b toxin is protease- and thermo-resistant, acting in pH range 3-7 on two species, Candida alai and Candida norvegica. The rapid decrease of the number of viable cells after toxin treatment demonstrates that both toxins have cytocidic effect. PMID:22695525

  7. Treatment of PCR products with exonuclease I and heat-labile alkaline phosphatase improves the visibility of combined bisulfite restriction analysis

    SciTech Connect

    Watanabe, Kousuke; Emoto, Noriko; Sunohara, Mitsuhiro; Kawakami, Masanori; Kage, Hidenori; Nagase, Takahide; Ohishi, Nobuya; Takai, Daiya

    2010-08-27

    Research highlights: {yields} Incubating PCR products at a high temperature causes smears in gel electrophoresis. {yields} Smears interfere with the interpretation of methylation analysis using COBRA. {yields} Treatment with exonuclease I and heat-labile alkaline phosphatase eliminates smears. {yields} The elimination of smears improves the visibility of COBRA. -- Abstract: DNA methylation plays a vital role in the regulation of gene expression. Abnormal promoter hypermethylation is an important mechanism of inactivating tumor suppressor genes in human cancers. Combined bisulfite restriction analysis (COBRA) is a widely used method for identifying the DNA methylation of specific CpG sites. Here, we report that exonuclease I and heat-labile alkaline phosphatase can be used for PCR purification for COBRA, improving the visibility of gel electrophoresis after restriction digestion. This improvement is observed when restriction digestion is performed at a high temperature, such as 60 {sup o}C or 65 {sup o}C, with BstUI and TaqI, respectively. This simple method can be applied instead of DNA purification using spin columns or phenol/chloroform extraction. It can also be applied to other situations when PCR products are digested by thermophile-derived restriction enzymes, such as PCR restriction fragment length polymorphism (RFLP) analysis.

  8. Identification of a Gene within a Pathogenicity Island of Enterotoxigenic Escherichia coli H10407 Required for Maximal Secretion of the Heat-Labile Enterotoxin

    PubMed Central

    Fleckenstein, James M.; Lindler, Luther E.; Elsinghorst, Eric A.; Dale, James B.

    2000-01-01

    Studies of the pathogenesis of enterotoxigenic Escherichia coli (ETEC) have largely centered on extrachromosomal determinants of virulence, in particular the plasmid-encoded heat-labile (LT) and heat-stable enterotoxins and the colonization factor antigens. ETEC causes illnesses that range from mild diarrhea to severe cholera-like disease. These differences in disease severity are not readily accounted for by our current understanding of ETEC pathogenesis. Here we demonstrate that Tia, a putative adhesin of ETEC H10407, is encoded on a large chromosomal element of approximately 46 kb that shares multiple features with previously described E. coli pathogenicity islands. Further analysis of the region downstream from tia revealed the presence of several candidate open reading frames (ORFs) in the same transcriptional orientation as tia. The putative proteins encoded by these ORFs bear multiple motifs associated with bacterial secretion apparatuses. An in-frame deletion in one candidate gene identified here as leoA (labile enterotoxin output) resulted in marked diminution of secretion of the LT enterotoxin and lack of fluid accumulation in a rabbit ileal loop model of infection. Although previous studies have suggested that E. coli lacks the capacity to secrete LT, our studies show that maximal release of LT from the periplasm of H10407 is dependent on one or more elements encoded on a pathogenicity island. PMID:10768971

  9. Heat-labile IgG2a antibodies affect cure of Trypanosoma musculi infection in C57BL/6 mice.

    PubMed

    Wechsler, D S; Kongshavn, P A

    1986-11-01

    Immune plasma (IP) obtained from mice cured of Trypanosoma musculi infection is able to mediate trypanosome clearance both in vivo and in vitro. A protein A-derived immunoglobulin fraction of IP containing primarily IgG2a and IgG3 shares this curative activity. Additional purification of IP with the use of anti-IgG2a and anti-IgG3 coupled to Sepharose beads demonstrates that the curative activity of IP resides solely in the IgG2a fraction; IP depleted of IgG2a is no longer able to effect T. musculi removal. Furthermore, this curative IgG2a is labile to heat treatment for 30 min at 56 degrees C. Enzyme-linked immunosorbent assays show that trypanosome-specific IgG2a builds up gradually over the course of infection, and temporarily drops slightly at the time of parasite clearance.

  10. Cytokine response by human monocytes to Clostridium difficile toxin A and toxin B.

    PubMed Central

    Flegel, W A; Müller, F; Däubener, W; Fischer, H G; Hadding, U; Northoff, H

    1991-01-01

    Clostridium difficile toxins A and B isolated from strain VPI 10463 were tested for induction of cytokine release by human monocytes. Toxin B at 10(-12) M activated human monocytes as measured by release of interleukin-1 (IL-1), tumor necrosis factor (TNF), or IL-6. These effects of toxin B were heat labile (51 degrees C, 30 min). Toxin B was as effective as bacterial lipopolysaccharides in inducing IL-1 beta but less effective in inducing TNF or IL-6. Toxin B and lipopolysaccharides were synergistic in induction of IL-1 beta, TNF, and IL-6. The toxin A preparation used was 1,000-fold less active than toxin B. Apart from the difference in activity, the two toxins showed identical patterns of reaction and there was no synergism between them. A short pulse with toxin B was sufficient to trigger IL-1 release. Toxin B was also extremely toxic for monocytes. The toxicity and the induced proinflammatory monokines (IL-1 and TNF) may contribute to the pathogenic mechanisms of C. difficile infection and pseudomembranous colitis. Images PMID:1910012

  11. A pain-inducing centipede toxin targets the heat activation machinery of nociceptor TRPV1

    NASA Astrophysics Data System (ADS)

    Yang, Shilong; Yang, Fan; Wei, Ningning; Hong, Jing; Li, Bowen; Luo, Lei; Rong, Mingqiang; Yarov-Yarovoy, Vladimir; Zheng, Jie; Wang, Kewei; Lai, Ren

    2015-09-01

    The capsaicin receptor TRPV1 ion channel is a polymodal nociceptor that responds to heat with exquisite sensitivity through an unknown mechanism. Here we report the identification of a novel toxin, RhTx, from the venom of the Chinese red-headed centipede that potently activates TRPV1 to produce excruciating pain. RhTx is a 27-amino-acid small peptide that forms a compact polarized molecule with very rapid binding kinetics and high affinity for TRPV1. We show that RhTx targets the channel's heat activation machinery to cause powerful heat activation at body temperature. The RhTx-TRPV1 interaction is mediated by the toxin's highly charged C terminus, which associates tightly to the charge-rich outer pore region of the channel where it can directly interact with the pore helix and turret. These findings demonstrate that RhTx binding to the outer pore can induce TRPV1 heat activation, therefore providing crucial new structural information on the heat activation machinery.

  12. A pain-inducing centipede toxin targets the heat activation machinery of nociceptor TRPV1.

    PubMed

    Yang, Shilong; Yang, Fan; Wei, Ningning; Hong, Jing; Li, Bowen; Luo, Lei; Rong, Mingqiang; Yarov-Yarovoy, Vladimir; Zheng, Jie; Wang, KeWei; Lai, Ren

    2015-09-30

    The capsaicin receptor TRPV1 ion channel is a polymodal nociceptor that responds to heat with exquisite sensitivity through an unknown mechanism. Here we report the identification of a novel toxin, RhTx, from the venom of the Chinese red-headed centipede that potently activates TRPV1 to produce excruciating pain. RhTx is a 27-amino-acid small peptide that forms a compact polarized molecule with very rapid binding kinetics and high affinity for TRPV1. We show that RhTx targets the channel's heat activation machinery to cause powerful heat activation at body temperature. The RhTx-TRPV1 interaction is mediated by the toxin's highly charged C terminus, which associates tightly to the charge-rich outer pore region of the channel where it can directly interact with the pore helix and turret. These findings demonstrate that RhTx binding to the outer pore can induce TRPV1 heat activation, therefore providing crucial new structural information on the heat activation machinery.

  13. A pain-inducing centipede toxin targets the heat activation machinery of nociceptor TRPV1.

    PubMed

    Yang, Shilong; Yang, Fan; Wei, Ningning; Hong, Jing; Li, Bowen; Luo, Lei; Rong, Mingqiang; Yarov-Yarovoy, Vladimir; Zheng, Jie; Wang, KeWei; Lai, Ren

    2015-01-01

    The capsaicin receptor TRPV1 ion channel is a polymodal nociceptor that responds to heat with exquisite sensitivity through an unknown mechanism. Here we report the identification of a novel toxin, RhTx, from the venom of the Chinese red-headed centipede that potently activates TRPV1 to produce excruciating pain. RhTx is a 27-amino-acid small peptide that forms a compact polarized molecule with very rapid binding kinetics and high affinity for TRPV1. We show that RhTx targets the channel's heat activation machinery to cause powerful heat activation at body temperature. The RhTx-TRPV1 interaction is mediated by the toxin's highly charged C terminus, which associates tightly to the charge-rich outer pore region of the channel where it can directly interact with the pore helix and turret. These findings demonstrate that RhTx binding to the outer pore can induce TRPV1 heat activation, therefore providing crucial new structural information on the heat activation machinery. PMID:26420335

  14. A pain-inducing centipede toxin targets the heat activation machinery of nociceptor TRPV1

    PubMed Central

    Yang, Shilong; Yang, Fan; Wei, Ningning; Hong, Jing; Li, Bowen; Luo, Lei; Rong, Mingqiang; Yarov-Yarovoy, Vladimir; Zheng, Jie; Wang, KeWei; Lai, Ren

    2015-01-01

    The capsaicin receptor TRPV1 ion channel is a polymodal nociceptor that responds to heat with exquisite sensitivity through an unknown mechanism. Here we report the identification of a novel toxin, RhTx, from the venom of the Chinese red-headed centipede that potently activates TRPV1 to produce excruciating pain. RhTx is a 27-amino-acid small peptide that forms a compact polarized molecule with very rapid binding kinetics and high affinity for TRPV1. We show that RhTx targets the channel's heat activation machinery to cause powerful heat activation at body temperature. The RhTx–TRPV1 interaction is mediated by the toxin's highly charged C terminus, which associates tightly to the charge-rich outer pore region of the channel where it can directly interact with the pore helix and turret. These findings demonstrate that RhTx binding to the outer pore can induce TRPV1 heat activation, therefore providing crucial new structural information on the heat activation machinery. PMID:26420335

  15. Chemical studies of H chondrites-10: Contents of thermally labile trace elements are unaffected by late heating

    NASA Astrophysics Data System (ADS)

    Wang, Ming-Sheng; Wolf, Stephen F.; Lipschutz, Michael E.

    1999-09-01

    We have used radiochemical neutron activation analysis (RNAA) to determine 15 trace elements, including 10 moderately and highly volatile ones - Rb, Ag, Se, Cs, Te, Zn, Cd, Bi, Tl, In (in increasing volatility order) - in 6 H chondrite falls with low 3He contents. These plus prior RNAA data provide a compositional database of 92 H4-6 chondrite falls. Three suites of samples can be identified from their noble gas contents: 44 with "normal" contents, and, therefore, "normal" orbits and cosmic ray exposure histories; 8 that lost radiogenic gases, presumably by shock late in their histories; and 17 that lost cosmogenic gases by heating during close solar approach. We used the standard multivariate statistical techniques of linear discriminant analysis and logistic regression to compare contents of the 10 moderately and highly volatile trace elements, listed above, in these 3 suites. We found no significant differences. This contrasts sharply with similar comparisons involving random falls and H4-6 chondrites that landed on Earth at specific time intervals. Apparently, contents of volatile trace elements in H4-6 chondrites were established early in their histories and they are so retentively sited that loss during later heating episodes did not occur.

  16. Subacute effects of maize-expressed vaccine protein, Escherichia coli heat-labile enterotoxin subunit B (LTB), on the Springtail, Folsomia candida , and the earthworm, Eisenia fetida.

    PubMed

    Kosaki, Hirofumi; Wolt, Jeffrey D; Wang, Kan; Coats, Joel R

    2008-12-10

    The ecotoxicological effects of transgenic maize-expressed vaccine protein, Escherichia coli heat-labile enterotoxin subunit B (LTB), on two soil invertebrates were studied under laboratory settings. After being reared for 28 days on LTB-maize-treated soils, no apparent mortality of the springtail, Folsomia candida , or the earthworm, Eisenia fetida , was observed at levels well above conservatively projected estimated environmental concentrations. Therefore, it is concluded that there would be no acutely toxic effect of LTB to these species. As for the subacute effect, no significant differences of F. candida mean reproduction and E. fetida mean growth were observed between LTB-maize-treated samples and non-GM-maize-treated controls. In addition, no LTB was detected in the E. fetida whole-body extraction assay, which indicates there was no tendency for bioaccumulation. On the basis of these observations, it is predicted that any adverse effects of LTB-maize on F. candida and E. fetida would be minimal, if any.

  17. Antibodies to heat-labile Escherichia coli enterotoxins in human milk and sera. A study of Ethiopian and Swedish mothers and their children.

    PubMed

    Aust-Kettis, A; Gebre-Medhin, M; Habte, D; Khosla, N; Wadström, T

    1981-09-01

    Maternal serum and cord blood from 50 Ethiopian, 10 Costa Rican and 20 Swedish newly delivered mothers and their babies was examined for the presence of antibodies against heat labile (LT) enterotoxin from a human strain of E. coli. 96% of the Ethiopian, 80% of the Costa Rican and 30% of the Swedish mothers and infants had detectable antibody levels. The titres were significantly higher in the Ethiopian material. Furthermore, antibody titres to E. coli enterotoxin were determined in breast milk collected from Ethiopian mothers at 48 h and at 1 month after delivery. One third of these mothers had detectable levels of antibodies in samples from early lactation. Experiments performed with LT enterotoxin from another human and with LT from a porcine E. coli strain confirmed the results. Neutralization tests with cholera enterotoxin as antigen were all negative in sera and milk samples from all these groups. The material has been collected in three different geographical areas which are nonendemic for cholera. PMID:7032015

  18. Heat-labile enterotoxin-induced activation of NF-κB and MAPK pathways in intestinal epithelial cells impacts enterotoxigenic Escherichia coli (ETEC) adherence.

    PubMed

    Wang, Xiaogang; Gao, Xiaofei; Hardwidge, Philip R

    2012-08-01

    Enterotoxigenic Escherichia coli (ETEC) causes human morbidity and mortality in developing nations and is an emerging threat to food safety in developed nations. The ETEC heat-labile enterotoxin (LT) not only causes diarrheal disease by deregulating host adenylate cyclase, but also enhances ETEC adherence to intestinal epithelial cells. The mechanism governing this LT pro-adherence phenotype is unclear. Here we investigated intestinal epithelial cell signal transduction pathways activated by ETEC and quantified the relative importance of these host pathways to LT-induced ETEC adherence. We show that ETEC activates both NF-κB and mitogen-activated protein kinase signalling pathways through mechanisms that are primarily dependent upon LT. LT-induced NF-κB activation depends upon the cAMP-dependent activation of the Ras-like GTPase Rap1 but is independent of protein kinase A (PKA). By using inhibitors of these pathways, we demonstrate that inhibiting the p38 mitogen-activated protein kinase prevents LT from increasing ETEC adherence. By contrast, the LT pro-adherence phenotype appears unrelated to both LT-induced Rap1 activity and to subsequent NF-κB activation. We speculate that LT may alter host signal transduction to induce the presentation of ligands for ETEC adhesins in such a way that promotes ETEC adherence. Our findings provide insight into previously unexplored functions of LT and their relative importance to ETEC virulence. PMID:22452361

  19. Immunization with a Double-Mutant (R192G/L211A) of the Heat-Labile Enterotoxin of Escherichia coli Offers Partial Protection against Campylobacter jejuni in an Adult Mouse Intestinal Colonization Model.

    PubMed

    Albert, M John; Haridas, Shilpa; Ebenezer, Mathew; Raghupathy, Raj; Khan, Islam

    2015-01-01

    We have previously shown that antibodies to cholera toxin (CT) reacted with the major outer membrane proteins (MOMPs) from Campylobacter jejuni strains on Western blot. Further, oral immunization with CT significantly protected against challenge with C. jejuni in an adult mouse colonization model of infection. CT and the heat-labile enterotoxin (LT) of enterotoxigenic Escherichia coli are structurally and functionally related. LT and its mutants including the double-mutant LT (R192G/L211A) (dmLT), are powerful mucosal adjuvants. Unlike LT which is reactogenic, dmLT has been shown to be safe for human use. In the current study, we determined whether rabbit anti-dmLT antibodies reacted with MOMPs from C. jejuni strains and whether immunization with dmLT would afford protection against C. jejuni. On Western blot, the MOMPs from C. jejuni 48 (Penner serotype O:19), C. jejuni 75 (O:3) and C. jejuni 111 (O:1,44) were probed with rabbit antibodies to dmLT or LT-E112K (a non-toxic LT mutant), which showed a lack of reaction. Adult BALB/c mice were orally immunized with dmLT and orally challenged with C. jejuni 48 or 111. Protection from colonization with the challenge bacteria was studied by enumerating Campylobacter colonies in feces daily for 9 days. Vaccination produced robust serum and stool antibody responses to dmLT and no antibody responses to C. jejuni MOMP. Vaccinated mice showed reduced colonization and excretion of both challenge strains compared to control mice. However, the differences were not statistically significant. The protective efficacy of the dmLT vaccine varied from 9.1% to 54.5%. The lack of cross-reaction between the MOMP and dmLT suggests that protection is not mediated by cross-reacting antibodies, but may be due to activation of innate immunity. As dmLT is safe for humans, it could be incorporated into a C. jejuni vaccine to enhance its efficacy. PMID:26540197

  20. Protection of piglets against enteric colibacillosis by intranasal immunization with K88ac (F4ac) fimbriae and heat labile enterotoxin of Escherichia coli.

    PubMed

    Lin, Jun; Mateo, Kristina S; Zhao, Mojun; Erickson, Alan K; Garcia, Nuria; He, Dong; Moxley, Rodney A; Francis, David H

    2013-03-23

    Enterotoxigenic Escherichia coli (ETEC) is an important diarrheal agent of young domestic animals. Currently, there are no commercially available non-living vaccines to protect weaned pigs from the disease and no major veterinary biologics company markets a postweaning ETEC vaccine of any kind. While efforts have been made to develop a non-living postweaning ETEC vaccine for pigs, studies have been limited to the assessment of immune responses to experimental immunogens. In the present study, we describe a reproducible gnotobiotic piglet model of post-weaning ETEC diarrhea and efficacy tests in that model of subunit vaccines consisting of K88 (F4) fimbriae and/or heat labile enterotoxin (LT) delivered by the intranasal route. We also report antibody responses to the vaccine antigens. Piglets vaccinated with both antigens mounted a substantial immune response with serum and cecal antibody titers to K88 antigen significantly greater than those of controls. Serum anti-LT antibody titers were also significantly greater than those of controls. Piglets vaccinated with both antigens remained healthy following challenge with ETEC. At least some pigs vaccinated with either antigen alone, and most of the control piglets developed dehydrating diarrhea and suffered significant weight loss. The results of this study suggest that an intranasal vaccine consisting of both antigens is highly protective against a vigorous experimental challenge of pigs with K88+ ETEC, while that against either antigen alone is not. The current study provides a system whereby various ETEC antigens and/or combinations of antigens can be tested in exploring strategies for the development of vaccines for ETEC. PMID:23089483

  1. Comparative study on characterization of recombinant B subunit of E. coli heat-labile enterotoxin (rLTB) prepared from E. coli and P. patoris.

    PubMed

    Ma, Xingyuan; Yao, Bi; Zheng, Wenyun; Li, Linfeng

    2010-03-01

    Escherichia coli (E. coli) heat-labile enterotoxin B subunit (LTB) was regarded as one of the most powerful mucosal immunoadjuvants eliciting strong immunoresponse to coadministered antigens. In the research, the high-level secretory expression of functional LTB was achieved in P. pastoris through high-density fermentation in a 5-l fermentor. Meanwhile, the protein was expressed in E. coli by the way of inclusion body, although the gene was cloned from E. coli. Some positive yeast and E. coli transformants were obtained respectively by a series of screenings and identifications. Fusion proteins LTB-6x His could be secreted into the supernatant of the medium after the recombinant P. pastoris was induced by 0.5% (v/v) methanol at 30 degrees C, whereas E. coli transformants expressed target protein in inclusion body after being induced by 1 mM IPTG at 37 degrees C. The expression level increased dramatically to 250- 300 mg/l supernatant of fermentation in the former and 80-100 mg/l in the latter. The LTB-6x His were purified to 95% purity by affinity chromatography and characterized by SDS-PAGE and Western blot. Adjuvant activity of target protein was analyzed by binding ability with GM1 gangliosides. The MW of LTB-6x His expressed in P. pastoris was greater than that in E. coli, which was equal to the expected 11 kDa, possibly resulted from glycosylation by P. pastoris that would enhance the immunogenicity of co-administered antigens. These data demonstrated that P. pastoris producing heterologous LTB has significant advantages in higher expression level and in adjuvant activity compared with the homologous E. coli system. PMID:20372026

  2. Electron Acceptors Induce Secretion of Enterotoxigenic Escherichia coli Heat-Labile Enterotoxin under Anaerobic Conditions through Promotion of GspD Assembly.

    PubMed

    Lu, Xi; Fu, Enqing; Xie, Yonghong; Jin, Faguang

    2016-10-01

    Heat-labile enterotoxin (LT), the major virulence factor of enterotoxigenic Escherichia coli (ETEC), can lead to severe diarrhea and promotes ETEC adherence to intestinal epithelial cells. Most previous in vitro studies focused on ETEC pathogenesis were conducted under aerobic conditions, which do not reflect the real situation of ETEC infection because the intestine is anoxic. In this study, the expression and secretion of LT under anaerobic or microaerobic conditions were determined; LT was not efficiently secreted into the supernatant under anaerobic or microaerobic conditions unless terminal electron acceptors (trimethylamine N-oxide dihydrate [TMAO] or nitrate) were available. Furthermore, we found that the restoration effects of TMAO and nitrate on LT secretion could be inhibited by amytal or ΔtorCAD and ΔnarG E. coli strains, indicating that LT secretion under anaerobic conditions was dependent on the integrity of the respiratory chain. At the same time, electron acceptors increase the ATP level of ETEC, but this increase was not the main reason for LT secretion. Subsequently, the relationship between the integrity of the respiratory chain and the function of the type II secretion system was determined. The GspD protein, the secretin of ETEC, was assembled under anaerobic conditions and was accompanied by LT secretion when TMAO or nitrate was added. Our data also demonstrated that TMAO and nitrate could not induce the GspD assembly and LT secretion in ΔtorCAD and ΔnarG strains, respectively. Moreover, GspD assembly under anaerobic conditions was assisted by the pilot protein YghG.

  3. Electron Acceptors Induce Secretion of Enterotoxigenic Escherichia coli Heat-Labile Enterotoxin under Anaerobic Conditions through Promotion of GspD Assembly.

    PubMed

    Lu, Xi; Fu, Enqing; Xie, Yonghong; Jin, Faguang

    2016-10-01

    Heat-labile enterotoxin (LT), the major virulence factor of enterotoxigenic Escherichia coli (ETEC), can lead to severe diarrhea and promotes ETEC adherence to intestinal epithelial cells. Most previous in vitro studies focused on ETEC pathogenesis were conducted under aerobic conditions, which do not reflect the real situation of ETEC infection because the intestine is anoxic. In this study, the expression and secretion of LT under anaerobic or microaerobic conditions were determined; LT was not efficiently secreted into the supernatant under anaerobic or microaerobic conditions unless terminal electron acceptors (trimethylamine N-oxide dihydrate [TMAO] or nitrate) were available. Furthermore, we found that the restoration effects of TMAO and nitrate on LT secretion could be inhibited by amytal or ΔtorCAD and ΔnarG E. coli strains, indicating that LT secretion under anaerobic conditions was dependent on the integrity of the respiratory chain. At the same time, electron acceptors increase the ATP level of ETEC, but this increase was not the main reason for LT secretion. Subsequently, the relationship between the integrity of the respiratory chain and the function of the type II secretion system was determined. The GspD protein, the secretin of ETEC, was assembled under anaerobic conditions and was accompanied by LT secretion when TMAO or nitrate was added. Our data also demonstrated that TMAO and nitrate could not induce the GspD assembly and LT secretion in ΔtorCAD and ΔnarG strains, respectively. Moreover, GspD assembly under anaerobic conditions was assisted by the pilot protein YghG. PMID:27430271

  4. Attenuated Salmonella Gallinarum secreting an Escherichia coli heat-labile enterotoxin B subunit protein as an adjuvant for oral vaccination against fowl typhoid.

    PubMed

    Jeon, Byung Woo; Jawale, Chetan V; Kim, Seung Hwan; Lee, John Hwa

    2012-12-15

    In our previous study, we constructed a vaccine candidate (JOL916) for fowl typhoid (FT). A live adjuvant Salmonella Gallinarum (SG) strain was generated in the present study to facilitate efficacious oral vaccination with this vaccine. The Escherichia coli eltB gene secreting heat-labile enterotoxin B subunit (LTB) was cloned into an Asd(+) plasmid pJHL65. This was transformed into a Δlon ΔcpxR Δasd SG strain and the resulting strain was designated JOL1229. Secretion of LTB from JOL1229 was confirmed with an immunoblot assay. To determine the optimal dose of the strain, 50 six-week-old female chickens were divided into five groups (Groups A-E, n=10 per group) and orally inoculated with various doses of JOL1229 and JOL916. In Group B (consisting of four parts JOL916 and one part JOL1229), significant cell-mediated immune responses, plasma IgG levels and intestinal secretary IgA levels were induced after inoculation with both strains. On challenge with the wild-type strain, significant reductions in mortality were observed in the group. In addition, after inoculation the LTB strain was not recovered in feces samples, and resulted in no, or very mild, gross lesions in the liver and spleen. Both CD4(+) and CD8(+) T-cells were significantly increased in peripheral blood samples from the chickens immunized with the LTB strain. Expression of the interleukin-6 (IL-6) gene in splenocytes was induced in the chickens immunized with the LTB strain. These results suggest that oral immunization with the LTB-adjuvant strain, in particular with the four parts JOL916 and one part JOL1229 mixture, increased the immune response and provided efficient protection against FT in chickens.

  5. Salmonella enterica serovar enteritidis ghosts carrying the Escherichia coli heat-labile enterotoxin B subunit are capable of inducing enhanced protective immune responses.

    PubMed

    Jawale, Chetan V; Lee, John Hwa

    2014-06-01

    The Escherichia coli heat-labile enterotoxin B subunit (LTB) is a potent vaccine adjuvant. Salmonella enterica serovar Enteritidis ghosts carrying LTB (S. Enteritidis-LTB ghosts) were genetically constructed using a novel plasmid, pJHL187-LTB, designed for the coexpression of the LTB and E lysis proteins. S. Enteritidis-LTB ghosts were characterized using scanning electron microscopy to visualize their transmembrane tunnel structures. The expression of LTB in S. Enteritidis-LTB ghost preparations was confirmed by immunoblot and enzyme-linked immunosorbent assays. The parenteral adjuvant activity of LTB was demonstrated by immunizing chickens with either S. Enteritidis-LTB ghosts or S. Enteritidis ghosts. Chickens were intramuscularly primed at 5 weeks of age and subsequently boosted at 8 weeks of age. In total, 60 chickens were equally divided into three groups (n = 20 for each): group A, nonvaccinated control; group B, immunized with S. Enteritidis-LTB ghosts; and group C, immunized with S. Enteritidis ghosts. Compared with the nonimmunized chickens (group A), the immunized chickens (groups B and C) exhibited increased titers of plasma IgG and intestinal secretory IgA antibodies. The CD3(+) CD4(+) subpopulation of T cells was also significantly increased in both immunized groups. Among the immunized chickens, those in group B exhibited significantly increased titers of specific plasma IgG and intestinal secretory IgA (sIgA) antibodies compared with those in group C, indicating the immunomodulatory effects of the LTB adjuvant. Furthermore, both immunized groups exhibited decreased bacterial loads in their feces and internal organs. These results indicate that parenteral immunization with S. Enteritidis-LTB ghosts can stimulate superior induction of systemic and mucosal immune responses compared to immunization with S. Enteritidis ghosts alone, thus conferring efficient protection against salmonellosis. PMID:24671556

  6. Purification and characterization of Clostridium difficile toxin.

    PubMed Central

    Rolfe, R D; Finegold, S M

    1979-01-01

    Recent evidence indicates that toxigenic Clostridium difficile strains are a major cause of antimicrobial-associated ileocecitis in laboratory animals and pseudomembranous colitis in humans. C. difficile ATCC 9689 was cultivated in a synthetic medium to which 3% ultrafiltrated proteose peptone was added. Purification of the toxin from broth filtrate was accomplished through ultrafiltration (100,000 nominal-molecular-weight-limit membrane), precipitation with 75% (NH4)2SO4, and chromatographic separation using Bio-Gel A 5m followed by ion-exchange chromatography on a diethylaminoethyl-Sephadex A-25 column. The purified toxin displayed only one band on polyacrylamide gel electrophoresis, and approximately 170 pg was cytopathic for human amnion cells. The isolated toxin was neutralized by Clostridium sordelli antitoxin, heat labile (56 degrees C for 30 min), and inactivated at pH 4 and 9; it had an isoelectric point of 5.0, increased vascular permeability in rabbits, and caused ileocecitis in hamsters when injected intracecally. Treatment of the toxin with trypsin, chymotrypsin, pronase, amylase, or ethylmercurithiosalicylate caused inactivation, whereas lipase had no effect. By gel filtration, its molecular weight was estimated as 530,000. Upon reduction and denaturation, the toxin dissociated into 185,000- and 50,000-molecular-weight components, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Extensive dissociation yielded only the 50,000-molecular-weight component. The toxin appears to be protoplasmic and is released into the surrounding environment upon autolysis of the cells. Attempts to correlate specific enzymatic activity with the toxin have been unsuccessful. These studies will help delineate the role of C. difficile toxin in antimicrobial-associated colitis and diarrhea. Images PMID:478634

  7. Antigenicity and immunogenicity of fused B-subunit of heat labile toxin of Escherichia coli and colonization factor antigen I polyepitopes.

    PubMed

    Savar, Nastaran Sadat; Dashti, Amir; Darzi Eslam, Elham; Jahanian-Najafabadi, Ali; Jafari, Anis

    2014-11-01

    Linear B-cell epitopes ((93)AKEFEAAAL(101) and (66)PQLTDVLN(73)) of CfaB were genetically fused to ltb-(gly)5-cfaB(1-25). Sera of rabbits immunized with fusion proteins reacted strongly with solid-phase bound ETEC bacteria bearing CFA/I fimbriae. Sera failed to agglutinate or inhibit hemagglutination promoted by CFA/I-positive strain which may be due to solvent inaccessibility of epitope residues on intact fimbriae. PMID:25108290

  8. Real-Time TaqMan PCR Assay for the Detection of Heat-Labile and Heat-Stable Enterotoxin Genes in a Geographically Diverse Collection of Enterotoxigenic Escherichia coli Strains and Stool Specimens.

    PubMed

    Pattabiraman, Vaishnavi; Parsons, Michele B; Bopp, Cheryl A

    2016-04-01

    Enterotoxigenic Escherichia coli (ETEC) are an important cause of diarrhea in children under the age of 5 years in developing countries and are the leading bacterial agent of traveler's diarrhea in persons traveling to these countries. ETEC strains secrete heat-labile (LT) and/or heat-stable (ST) enterotoxins that induce diarrhea by causing water and electrolyte imbalance. We describe the validation of a real-time TaqMan PCR (RT-PCR) assay to detect LT, ST1a, and ST1b enterotoxin genes in E. coli strains and in stool specimens. We validated LT/ST1b duplex and ST1a single-plex RT-PCR assay using a conventional PCR assay as a gold standard with 188 ETEC strains and 42 non-ETEC strains. We validated LT/ST1b duplex and ST1a single-plex RT-PCR assay in stool specimens (n = 106) using traditional culture as the gold standard. RT- PCR assay sensitivities for LT, ST1a, and ST1b detection in strains were 100%, 100%, and 98%; specificities were 95%, 98%, and 99%, and Pearson correlation coefficient r was 0.9954 between RT-PCR assay and the gold standard. In stool specimens, RT-PCR assay sensitivities for LT, ST1a, and ST1b detection were 97%, 100%, and 97%; and specificities were 99%, 94%, and 97%. Pearson correlation coefficient r was 0.9975 between RT-PCR results in stool specimens and the gold standard. Limits of detection of LT, ST1a, and ST1b by RT-PCR assay were 0.1 to1.0 pg/μL and by conventional PCR assay were 100 to1000 pg/μL. The accuracy, rapidity and sensitivity of this RT-PCR assay is promising for ETEC detection in public health/clinical laboratories and for laboratories in need of an independent method to confirm results of other culture independent diagnostic tests.

  9. Characteristics of the labile neurotoxin associated with nervous coccidiosis.

    PubMed Central

    Isler, C M; Bellamy, J E; Wobeser, G A

    1987-01-01

    Reported are the results of preliminary attempts to characterize the molecular weight, heat sensitivity and other features of a labile neurotoxin identified in the serum of calves exhibiting neurological signs in association with coccidial enteritis. The labile neurotoxin activity is heat labile (60 degrees C for 30 min) and is lost upon exposure to acidic pH (5.5) and cysteine (1.75 g/100 mL serum). Activity can be recovered from the precipitate of a 30% wt/vol solution of (NH4)2SO4 in serum. Ultrafiltration trials suggest that labile neurotoxin activity may be linked to a molecule of over 300,000 MW. PMID:2955866

  10. [Exploring the pathogenesis and therapy of liver cancer from "damp-heat insidious pathogen" to "cancer toxin"].

    PubMed

    Wang, Shu-Jie; Wei, Ai-Ling

    2013-02-01

    From a macro-level analysis of the attributes and pathogenic features of HBV, the main pathogenic factor for chronic liver diseases including viral hepatitis, cirrhosis, and liver cancer, the concept of damp-heat insidious pathogen was obtained, according to which, in-depth discussions were undertaken. Adopting syndrome typing of Wei (defense), qi (vital energy), Ying (nutrients), and blood, the pathogens leading to different syndromes as well as new products such as pathological "sputum", "stasis" in the disease process were understood, and then, the pathological "sputum" and "stasis", as the hub, playing a role in chronic lesions of the liver collateral were explained. Finally the pathological "sputum" and "stasis" blend and form cancer toxin. Through a comprehensive understanding of the development of chronic liver diseases, it is clear that damp-heat insidious pathogen, as its initiating factor, always exists in the whole process. We summed up heat clearing, dampness resolving, and detoxification was the principle for treating chronic liver disease.

  11. Properties of dermonecrotic toxin prepared from sonic extracts Bordetella bronchiseptica.

    PubMed Central

    Kume, K; Nakai, T; Samejima, Y; Sugimoto, C

    1986-01-01

    A toxin with dermonecrotic activity (DNT) was purified from sonic extracts of Bordetella bronchiseptica L3 of pig origin at phase I by chromatographic and electrophoretic methods. The purification procedure was one developed for obtaining the Pasteurella multocida DNT from sonic extracts with some modifications. Dermonecrotizing activity of B. bronchiseptica-purified DNT was increased by 600-fold compared with that of the crude extract, and the average yield was about 3%. The toxin was homogeneous, as determined by Ouchterlony double immunodiffusion, crossed immunoelectrophoresis, and disk isoelectric focusing in polyacrylamide gels. The toxin gave a single band on polyacrylamide disk gel electrophoresis (PAGE) and sodium dodecyl sulfate-SDS PAGE. The molecular weight of the toxin was ca. 190,000 +/- 5,000, as determined by SDS-PAGE. The isoelectric point of the toxin was ca. 6.5 to 6.6. The minimal necrotizing dose of the toxin for guinea pigs was about 2 ng of protein per 0.1 ml, the 50% lethal dose per mouse was about 0.3 micrograms, and the minimal cytotoxic dose for embryonic bovine lung cells was about 2 ng/ml. The toxin was heat labile and sensitive to inactivation by trypsin, Formalin, and glutaraldehyde. The mildly trypsinized B. bronchiseptica DNT preparation dissociated into two polypeptide chains, with molecular weights of ca. 75,000 +/- 4,000 (fragment 1) and ca. 118,000 +/- 5,000 (fragment 2), after treatment with dithiothreitol-SDS or urea. Upon removal of dithiothreitol and urea from the dissociated DNT preparation, the fragments reassociated, and the DNT that was formed was indistinguishable from the native toxin. Images PMID:3699886

  12. The adjuvant effect of a non-toxic mutant of heat-labile enterotoxin of Escherichia coli for the induction of measles virus-specific CTL responses after intranasal co-immunization with a synthetic peptide.

    PubMed Central

    Partidos, C D; Pizza, M; Rappuoli, R; Steward, M W

    1996-01-01

    The intranasal route has been shown to be effective for immunization. However, immunization via this route may require the use of potent and safe adjuvant. The construction of non-toxic mutants of heat labile enterotoxin of Escherichia coli (LT), which is a potent mucosal adjuvant, is a major breakthrough for the development of mucosal vaccines. In this study we have assessed the ability of an LT mutant (LTK63) to act as an adjuvant following intranasal co-immunization with a peptide corresponding to a measles virus cytotoxic T lymphocyte (CTL) epitope. LTK63 was more effective at potentiating the in vivo induction of peptide-specific and measles virus-specific CTL responses than was administration of the peptide in saline. A concentration of 10 micrograms/dose of LTK63 was found to be the most effective in potentiating the in vivo priming of peptide-specific and measles virus-specific CTL responses. These findings highlight the potential of the non-toxic mutant of LT as a safe mucosal adjuvant for use in humans. PMID:9014810

  13. Construction of Bifidobacterium infantis as a live oral vaccine that expresses antigens of the major fimbrial subunit (CfaB) and the B subunit of heat-labile enterotoxin (LTB) from enterotoxigenic Escherichia coli.

    PubMed

    Ma, Yongping; Luo, Yaolin; Huang, Xueping; Song, Fangzhou; Liu, Geli

    2012-02-01

    We sought to develop Bifidobacterium infantis (BI) as a vehicle for the expression of heterologous antigens. Two proteins of enterotoxigenic Escherichia coli (ETEC) were expressed in BI: CfaB, a major fimbrial subunit protein, and LTB, the B subunit of heat-labile enterotoxin. The expression of CfaB and LTB in BI was verified by electrophoretic analysis. Sprague-Dawley rats were then subjected to intragastric immunization with BI-CfaB and BI-LTB systems both separately and together. ELISA was used to characterize the serum and mucosal immune responses against ETEC antigens. The immunized rats were intraperitoneally challenged with wild-type ETEC H10407 to study the immune response in vivo. The serum titres of IgG and faecal IgA antibodies in the BI-CfaB plus BI-LTB mixed vaccination group were significantly greater than those in the other two groups, which were immunized with a single vaccine (P<0.05). However, no significant difference was seen between the two groups that received a single immunization. These results suggest that expressing CfaB and LTB in BI provides a probiotic system with immunogenic properties. Furthermore, the expression of LTB in BI preserved its mucosal adjuvant effect. So this study confirms that BI can be used as a novel oral vaccine expression system for a heterologous antigen and BI-LTB can provide mucosal adjuvant properties. PMID:22053005

  14. Comparison of a live attenuated Salmonella Enteritidis vaccine candidate secreting Escherichia coli heat-labile enterotoxin B subunit with a commercial vaccine for efficacy of protection against internal egg contamination by Salmonella in hens.

    PubMed

    Nandre, Rahul M; Eo, Seong Kug; Park, Sang Youel; Lee, John Hwa

    2015-07-01

    This study compared a new live attenuated Salmonella Enteritidis vaccine candidate secreting Escherichia coli heat-labile enterotoxin B subunit (SE-LTB) with a commercial Salmonella Enteritidis (SE) vaccine for efficacy of protection against SE infection in laying hens. Chickens were divided into 3 groups of 20 each. Group A chickens were inoculated orally with phosphate-buffered saline and served as controls, group B chickens were inoculated orally with the vaccine candidate, and group C chickens were inoculated intramuscularly with a commercial vaccine, the primary inoculation in groups B and C being at 10 wk of age and the booster at 16 wk. Groups B and C showed significantly higher titers of plasma immunoglobulin G, intestinal secretory immunoglobulin A, and egg yolk immunoglobulin Y antibodies compared with the control group, and both vaccinated groups showed a significantly elevated cellular immune response. After virulent challenge, group B had significantly lower production of thin-shelled and/or malformed eggs and a significantly lower rate of SE contamination of eggs compared with the control group. Furthermore, the challenge strain was detected significantly less in all of the examined organs of group B compared with the control group. Group C had lower gross lesion scores only in the spleen and had lower bacterial counts only in the spleen, ceca, and ovary. These findings indicate that vaccination with the SE-LTB vaccine candidate can efficiently reduce internal egg and internal organ contamination by Salmonella and has advantages over the commercial vaccine.

  15. Microwave Heating Inactivates Shiga Toxin (Stx2) in Reconstituted Fat-Free Milk and Adversely Affects the Nutritional Value of Cell Culture Medium.

    PubMed

    Rasooly, Reuven; Hernlem, Bradley; He, Xiaohua; Friedman, Mendel

    2014-03-26

    Microwave exposure is a convenient and widely used method for defrosting, heating, and cooking numerous foods. Microwave cooking is also reported to kill pathogenic microorganisms that often contaminate food. In this study, we tested whether microwaves would inactivate the toxicity of Shiga toxin 2 (Stx2) added to 5% reconstituted fat-free milk administered to monkey kidney Vero cells. Heating of milk spiked with Stx2 in a microwave oven using a 10% duty cycle (cycle period of 30 s) for a total of 165 kJ energy or thermal heating (pasteurization), widely used to kill pathogenic bacteria, did not destroy the biological effect of the toxin in the Vero cells. However, conventional heating of milk to 95 °C for 5 min or at an increased microwave energy of 198 kJ reduced the Stx2 activity. Gel electrophoresis showed that exposure of the protein toxin to high-energy microwaves resulted in the degradation of its original structure. In addition, two independent assays showed that exposure of the cell culture medium to microwave energy of 198 kJ completely destroyed the nutritional value of the culture medium used to grow the Vero cells, possibly by damaging susceptible essential nutrients present in the medium. These observations suggest that microwave heating has the potential to destroy the Shiga toxin in liquid food.

  16. The influence of ligand valency on aggregation mechanisms for inhibiting bacterial toxins.

    PubMed

    Sisu, Cristina; Baron, Andrew J; Branderhorst, Hilbert M; Connell, Simon D; Weijers, Carel A G M; de Vries, Renko; Hayes, Edward D; Pukin, Aliaksei V; Gilbert, Michel; Pieters, Roland J; Zuilhof, Han; Visser, Gerben M; Turnbull, W Bruce

    2009-01-26

    Divalent and tetravalent analogues of ganglioside GM1 are potent inhibitors of cholera toxin and Escherichia coli heat-labile toxin. However, they show little increase in inherent affinity when compared to the corresponding monovalent carbohydrate ligand. Analytical ultracentrifugation and dynamic light scattering have been used to demonstrate that the multivalent inhibitors induce protein aggregation and the formation of space-filling networks. This aggregation process appears to arise when using ligands that do not match the valency of the protein receptor. While it is generally accepted that multivalency is an effective strategy for increasing the activity of inhibitors, here we show that the valency of the inhibitor also has a dramatic effect on the kinetics of aggregation and the stability of intermediate protein complexes. Structural studies employing atomic force microscopy have revealed that a divalent inhibitor induces head-to-head dimerization of the protein toxin en route to higher aggregates. PMID:19034953

  17. The Pertussis Toxin S1 Subunit Is a Thermally Unstable Protein Susceptible to Degradation by the 20S Proteasome†

    PubMed Central

    Pande, Abhay H.; Moe, David; Jamnadas, Maneesha; Tatulian, Suren A.; Teter, Ken

    2008-01-01

    Pertussis toxin (PT) is an AB-type protein toxin that consists of a catalytic A subunit (PT S1) and an oligomeric, cell-binding B subunit. It belongs to a subset of AB toxins that move from the cell surface to the endoplasmic reticulum (ER) before A chain passage into the cytosol. Toxin translocation is thought to involve A chain unfolding in the ER and the quality control mechanism of ER-associated degradation (ERAD). The absence of lysine residues in PT S1 may allow the translocated toxin to avoid ubiquitin-dependent degradation by the 26S proteasome, which is the usual fate of exported ERAD substrates. As the conformation of PT S1 appears to play an important role in toxin translocation, we used biophysical and biochemical methods to examine the structural properties of PT S1. Our in vitro studies found that the isolated PT S1 subunit is a thermally unstable protein that can be degraded in a ubiquitin-independent fashion by the core 20S proteasome. The thermal denaturation of PT S1 was inhibited by its interaction with NAD, a donor molecule used by PT S1 for the ADP-ribosylation of target G proteins. These observations support a model of intoxication in which toxin translocation, degradation, and activity are all influenced by the heat-labile nature of the isolated toxin A chain. PMID:17105192

  18. The Divergent CD8+ T Cell Adjuvant Properties of LT-IIb and LT-IIc, Two Type II Heat-Labile Enterotoxins, Are Conferred by Their Ganglioside-Binding B Subunits

    PubMed Central

    Hu, John C.; Greene, Christopher J.; King-Lyons, Natalie D.; Connell, Terry D.

    2015-01-01

    Poor immune responses elicited by vaccine antigens can be enhanced by the use of appropriate adjuvants. Type II heat-labile enterotoxins (HLT) produced by Escherichia coli are extremely potent adjuvants that augment both humoral and cellular immunity to co-administered antigens. Recent findings demonstrate that LT-IIb and LT-IIc, two type II HLT adjuvants, exhibit potent, yet distinguishable CD8+ T cell adjuvant properties. While LT-IIc elicits a robust and rapid response at one week after administration, LT-IIb engenders a more gradual and slower expansion of antigen-specific CD8+ T cells that correlates with improved immunity. The variations in immune effects elicited by the HLT adjuvants have been generally attributed to their highly divergent B subunits that mediate binding to various gangliosides on cell surfaces. Yet, HLT adjuvants with point mutations in the B subunit that significantly alter ganglioside binding retain similar adjuvant functions. Therefore, the contribution of the B subunits to adjuvanticity remains unclear. To investigate the influence of the B subunits on the enhancement of immune responses by LT-IIb and LT-IIc, chimeric HLT were engineered in which the B subunits of the two adjuvants were exchanged. Comparing the immune potentiating characteristics of both native and chimeric HLT adjuvants, it was found that not all the adjuvant characteristics of the HLT adjuvants were modulated by the respective B subunits. Specifically, the differences in the CD8+ T cell kinetics and protective responses elicited by LT-IIb and LT-IIc did indeed followed their respective B subunits. However, induction of IL-1 from macrophages and the capacity to intoxicate cells in a mouse Y1 adrenal cell bioassay did not correlate with the B subunits. Therefore, it is likely that additional factors other than the B subunits contribute to the effects elicited by the HLT adjuvants. PMID:26565800

  19. Mucosal vaccination against serogroup B meningococci: induction of bactericidal antibodies and cellular immunity following intranasal immunization with NadA of Neisseria meningitidis and mutants of Escherichia coli heat-labile enterotoxin.

    PubMed

    Bowe, Frances; Lavelle, Ed C; McNeela, Edel A; Hale, Christine; Clare, Simon; Arico, Beatrice; Giuliani, Marzia M; Rae, Aaron; Huett, Alan; Rappuoli, Rino; Dougan, Gordon; Mills, Kingston H G

    2004-07-01

    Conjugated polysaccharide vaccines protect against serogroup C meningococci. However, this approach cannot be applied to serogroup B, which is still a major cause of meningitis. We evaluated the immunogenicity of three surface-exposed proteins from serogroup B Neisseria meningitidis (App, NhhA, and NadA) identified during whole-genome sequencing. Mice were immunized intranasally with individual proteins in the presence of wild-type Escherichia coli heat-labile enterotoxin (LTwt), LTR72, a partially inactivated mutant, or LTK63, a completely nontoxic mutant, as the adjuvant. Each of the meningococcal proteins induced significant cellular responses; NhhA and NadA induced strong antibody responses, but only NadA induced bactericidal antibody when administered intranasally with mucosal adjuvants. In addition, immunoglobulin A and bactericidal antibodies were detected in the respiratory tract following intranasal delivery of NadA. Analysis of antigen-specific cytokine production by T cells from immunized mice revealed that intranasal immunization with NadA alone failed to generate detectable cellular immune responses. In contrast, LTK63, LTR72, and LTwt significantly augmented NadA-specific gamma interferon, interleukin-4 (IL-4), IL-5, and IL-10 production by spleen and lymph node cells, suggesting that both Th1 and Th2 cells were induced in vivo. The strongest cellular responses and highest bactericidal antibody titers were generated with LTR72 as the adjuvant. These findings demonstrate that the quality and magnitude of the immune responses generated by mucosal vaccines are influenced by the antigen as well as the adjuvant and suggest that nasal delivery of NadA with mucosal adjuvants has considerable potential in the development of a mucosal vaccine against serogroup B meningococci.

  20. Metal Complexes And Free Radical Toxins Produced By Pfiesteria Piscicida

    SciTech Connect

    Moeller, P.D.R.; Beauchesne, K.R.; Huncik, K.M.; Davis, W.C.; Christopher, S.J.; Riggs-Gelasco, P.; Gelasco, A.K.

    2009-06-03

    Metal-containing organic toxins produced by Pfiesteria piscicida were characterized, for the first time, by corroborating data obtained from five distinct instrumental methods: nuclear magnetic resonance spectroscopy (NMR), inductively coupled plasma mass spectrometry (ICPMS), liquid chromatography particle beam glow discharge mass spectrometry (LC/PB-GDMS), electron paramagnetic resonance spectroscopy (EPR), and X-ray absorption spectroscopy (XAS). The high toxicity of the metal-containing toxins is due to metal-mediated free radical production. This mode of activity explains the toxicity of Pfiesteria, as well as previously reported difficulty in observing the molecular target, due to the ephemeral nature of radical species. The toxins are highly labile in purified form, maintaining activity for only 2-5 days before all activity is lost. The multiple toxin congeners in active extracts are also susceptible to decomposition in the presence of white light, pH variations, and prolonged heat. These findings represent the first formal isolation and characterization of a radical forming toxic organic-ligated metal complex isolated from estuarine/marine dinoflagellates. These findings add to an increased understanding regarding the active role of metals interacting with biological systems in the estuarine environment, as well as their links and implications to human health.

  1. Metal Complexes and Free Radical Toxins Produced by Pfiesteria piscicida

    SciTech Connect

    Moeller,P.; Beauchesne, K.; Huncik, K.; Davis, W.; Christopher, S.; Riggs-Gelasco, P.; Gelasco, A.

    2007-01-01

    Metal-containing organic toxins produced by Pfiesteria piscicida were characterized, for the first time, by corroborating data obtained from five distinct instrumental methods: nuclear magnetic resonance spectroscopy (NMR), inductively coupled plasma mass spectrometry (ICP-MS), liquid chromatography particle beam glow discharge mass spectrometry (LC/PB-GDMS), electron paramagnetic resonance spectroscopy (EPR), and X-ray absorption spectroscopy (XAS). The high toxicity of the metal-containing toxins is due to metal-mediated free radical production. This mode of activity explains the toxicity of Pfiesteria, as well as previously reported difficulty in observing the molecular target, due to the ephemeral nature of radical species. The toxins are highly labile in purified form, maintaining activity for only 2-5 days before all activity is lost. The multiple toxin congeners in active extracts are also susceptible to decomposition in the presence of white light, pH variations, and prolonged heat. These findings represent the first formal isolation and characterization of a radical forming toxic organic-ligated metal complex isolated from estuarine/marine dinoflagellates. These findings add to an increased understanding regarding the active role of metals interacting with biological systems in the estuarine environment, as well as their links and implications to human health.

  2. Labile neurotoxin in serum of calves with "nervous" coccidiosis.

    PubMed Central

    Isler, C M; Bellamy, J E; Wobeser, G A

    1987-01-01

    Mouse inoculation was used to test for the presence of a toxin in the serum, cerebrospinal fluid, and intestinal contents collected from cases of bovine enteric coccidiosis, with and without neurological signs, and from control calves. Intravenous inoculation of mice with 10 mL/kg of serum from calves showing nervous signs caused effects significantly different from those caused by the inoculation of serum from calves not showing nervous signs and from control calves. The effect was particularly evident in female mice. At this dosage severe neurological signs such as loss of righting reflex, seizures and death occurred only with serum from calves with "nervous coccidiosis". The results suggest that serum from the calves with neurological signs contains a neurotoxin. This toxin appears to be highly labile. It was not present in the cerebrospinal fluid at levels comparable to those in the serum. The significance of this labile neurotoxin with respect to the pathogenesis of the neurological signs associated with bovine enteric coccidiosis is unknown. PMID:2955865

  3. Virulence profiles of enterotoxigenic, shiga toxin and enteroaggregative Escherichia coli in South African pigs.

    PubMed

    Mohlatlole, Ramadimetja Prescilla; Madoroba, Evelyn; Muchadeyi, Farai Catherine; Chimonyo, Michael; Kanengoni, Arnold Tapera; Dzomba, Edgar Farai

    2013-08-01

    Enterotoxigenic Escherichia coli (ETEC) and shiga toxin E. coli (STEC) are important causes of colibacillosis in piglets. Recently, enteroaggregative E. coli heat-stable enterotoxin 1 (EAST-1) has been implicated in pig diarrhoea. This study investigated the prevalence of enterotoxin [heat-labile toxins (LT), heat-stable toxin a (STa), heat-stable toxin b (STb)], shiga toxins (Stx1, Stx2, Stx2e), enteroaggregative heat-stable E. coli (EAST-1), associated fimbriae (F4, F5, F6, F41, F18ab, F18ac) and non-fimbrial adhesins [adhesin involved in diffuse adherence 1 (AIDA-1), attaching and effacing factor, porcine attaching- and effacing-associated factor] in South African pigs. A total of 263 E. coli strains were isolated from Landrace (n = 24), Large White (n = 126), Duroc (n = 28) and indigenous (n = 85) breeds of piglets aged between 9 and 136 days. PCR was used in the analysis. Virulent genes were detected in 40.3% of the isolates, of which 18.6, 0.4 and 17.5% were classified as ETEC, STEC and enteroaggregative E. coli (EAEC), respectively. Individual genes were found in the following proportions: STb (19.01%), LT (0.4%), STa (3.4%), St2xe (1.1%) and EAST-1 (20.2%) toxins. None of the tested fimbriae were detected in ETEC and STEC isolates. About one third of the ETEC and STEC isolates was tested negative for both fimbrial and non-fimbrial adhesins. Twenty-five pathotypes from ETEC-, EAEC- and STEC-positive strains were identified. Pathotypes EAST-1 (30.2%), STb (13.2%) and STb/AIDA-1 (10.4%) were most prevalent. The study provided insight on possible causes of colibacillosis in South African pigs. PMID:23417826

  4. Mucous Hypersecretion Induced in Isolated Mucociliated Epithelial Cells by a Factor in Heated Serum

    PubMed Central

    Bang, B. G.; Bang, F. B.

    1972-01-01

    A factor in the serum of the marine coelomate, Sipunculus nudus, induced by injecting a mixture of a marine bacterial vibrio and a solution of dried cholera toxin, will, after heating to 85 to 90 C, cause intensive continuous hypersecretion of mucus in isolated free-swimming mucociliated cells from another Sipunculus. The factor, released from coleomic cells into the serum, is heat stable to 90 C, withstands several freeze-thawings, is induced only by specific stimuli, is rapidly released into the serum, persists for different time spans depending on the stimulus, and is not present in normal heated sera. It is proposed that in nature this factor is balanced by a heat labile inhibitory factor. Cholera toxin alone is a feeble stimulus. The marine vibrio alone is a powerful stimulus to mucus secretion but lethal for the host. In combination with cholera toxin, the vibrio is nonlethal. ImagesFig 1Fig 2AFig 2B PMID:5049431

  5. Evidence for the presence of a receptor for the cytolethal distending toxin (CLDT) of Campylobacter jejuni on CHO and HeLa cell membranes and development of a receptor-based enzyme-linked immunosorbent assay for detection of CLDT.

    PubMed

    Bag, P K; Ramamurthy, T; Nair, U B

    1993-12-15

    Using ligand blotting, it was found that partially purified cytolethal distending toxin prepared from an enterotoxigenic strain of Campylobacter jejuni, bound to two peptides of molecular masses of approximately 59 kDa and 45 kDa and to a single peptide of 59 kDa in protein blots prepared from HeLa and CHO cell membranes, respectively. In contrast, labile toxin of Escherichia coli and cholera toxin bound to a single peptide of the same molecular mass (15 kDa) on protein blots prepared from both CHO and HeLa cell crude membranes resolved by gel electrophoresis. This banding pattern was identical using SDS-solubilized membrane, with or without heat treatment, but no band was obtained when reduced (treatment with 2-mercaptoethanol) samples were used for the gel electrophoresis. The differences between receptors of cytolethal distending toxin and cholera toxin/labile toxin were exploited to develop a receptor-based enzyme-linked immunosorbent assay for detection of cytolethal distending toxin which involved the consecutive addition of either solubilized CHO or HeLa membranes, antigen and antibody. This enzyme-linked immunosorbent assay consistently detected crude cytolethal distending toxin diluted up to 16-fold. The receptor-based enzyme-linked immunosorbent assay for detection of cytolethal distending toxin developed in this study is a suitable alternative assay which can be performed easily in laboratories with minimal facilities and, more importantly, the results are available within a few hours as compared to times of up to 5 days in the conventional tissue culture detection of cytolethal distending toxin.

  6. Characterization of Immunological Cross-Reactivity between Enterotoxigenic Escherichia coli Heat-Stable Toxin and Human Guanylin and Uroguanylin

    PubMed Central

    Taxt, Arne M.; Diaz, Yuleima; Bacle, Amélie; Grauffel, Cédric; Reuter, Nathalie; Aasland, Rein; Sommerfelt, Halvor

    2014-01-01

    Enterotoxigenic Escherichia coli (ETEC) expressing the heat-stable toxin (ST) (human-type [STh] and porcine-type [STp] variants) is among the five most important enteric pathogens in young children living in low- and middle-income countries. ST mediates diarrheal disease through activation of the guanylate cyclase C (GC-C) receptor and is an attractive vaccine target with the potential to confer protection against a wide range of ETEC strains. However, immunological cross-reactivity to the endogenous GC-C ligands guanylin and uroguanylin is a major concern because of the similarities to ST in amino acid sequence, structure, and function. We have investigated the presence of similar epitopes on STh, STp, guanylin, and uroguanylin by analyzing these peptides in eight distinct competitive enzyme-linked immunosorbent assays (ELISAs). A fraction (27%) of a polyclonal anti-STh antibody and an anti-STh monoclonal antibody (MAb) cross-reacted with uroguanylin, the latter with a 73-fold-lower affinity. In contrast, none of the antibodies raised against STp, one polyclonal antibody and three MAbs, cross-reacted with the endogenous peptides. Antibodies raised against guanylin and uroguanylin showed partial cross-reactivity with the ST peptides. Our results demonstrate, for the first time, that immunological cross-reactions between ST and the endogenous peptides can occur. However, the partial nature and low affinity of the observed cross-reactions suggest that the risk of adverse effects from a future ST vaccine may be low. Furthermore, our results suggest that this risk may be reduced or eliminated by basing an ST immunogen on STp or a selectively mutated variant of STh. PMID:24778111

  7. Characterization of immunological cross-reactivity between enterotoxigenic Escherichia coli heat-stable toxin and human guanylin and uroguanylin.

    PubMed

    Taxt, Arne M; Diaz, Yuleima; Bacle, Amélie; Grauffel, Cédric; Reuter, Nathalie; Aasland, Rein; Sommerfelt, Halvor; Puntervoll, Pål

    2014-07-01

    Enterotoxigenic Escherichia coli (ETEC) expressing the heat-stable toxin (ST) (human-type [STh] and porcine-type [STp] variants) is among the five most important enteric pathogens in young children living in low- and middle-income countries. ST mediates diarrheal disease through activation of the guanylate cyclase C (GC-C) receptor and is an attractive vaccine target with the potential to confer protection against a wide range of ETEC strains. However, immunological cross-reactivity to the endogenous GC-C ligands guanylin and uroguanylin is a major concern because of the similarities to ST in amino acid sequence, structure, and function. We have investigated the presence of similar epitopes on STh, STp, guanylin, and uroguanylin by analyzing these peptides in eight distinct competitive enzyme-linked immunosorbent assays (ELISAs). A fraction (27%) of a polyclonal anti-STh antibody and an anti-STh monoclonal antibody (MAb) cross-reacted with uroguanylin, the latter with a 73-fold-lower affinity. In contrast, none of the antibodies raised against STp, one polyclonal antibody and three MAbs, cross-reacted with the endogenous peptides. Antibodies raised against guanylin and uroguanylin showed partial cross-reactivity with the ST peptides. Our results demonstrate, for the first time, that immunological cross-reactions between ST and the endogenous peptides can occur. However, the partial nature and low affinity of the observed cross-reactions suggest that the risk of adverse effects from a future ST vaccine may be low. Furthermore, our results suggest that this risk may be reduced or eliminated by basing an ST immunogen on STp or a selectively mutated variant of STh. PMID:24778111

  8. Effect of temperatures on the growth, toxin production, and heat resistance of Bacillus cereus in cooked rice.

    PubMed

    Wang, Jun; Ding, Tian; Oh, Deog-Hwan

    2014-02-01

    Bacillus cereus is capable of producing enterotoxin and emetic toxin, and Bacillus foodborne illnesses occur due to the consumption of food contaminated with endospores. The objectives of this study were to investigate the growth and toxin production of B. cereus in cooked rice and to determine the effect of temperature on toxin destruction. Cooked rice inoculated with B. cereus was stored at 15, 25, 35, and 45°C or treated at 80, 90, and 100°C. The results indicated that emetic toxin was produced faster than enterotoxin (which was not detected below 15°C) at all the storage temperatures (15-45°C) during the first 72 h. Emetic toxin persisted at 100°C for 2 h, although enterotoxin was easily to be destroyed by this treatment within 15 min. In addition, B. cereus in cooked rice stored at a warm temperature for a period was not inactivated due to survival of the thermostable endospores. These data indicate that the contaminated cooked rice with B. cereus might present a potential risk to consumers. Results from this study may help enhance the safety of such food, and provide valuable and reliable information for risk assessment and management, associated with the problem of B. cereus in cooked rice.

  9. TOXINS AND ANTITOXINS OF BACILLUS DYSENTERIAE SHIGA.

    PubMed

    Olitsky, P K; Kligler, I J

    1920-01-01

    With the methods which have been described we have separated an exotoxin and an endotoxin from cultures of the Shiga dysenteric bacillus. The study of the nature and effect of the poison of this microorganism is thus simplified. The two toxins are physically and biologically distinct. The exotoxin is relatively heat-labile, arises in the early period of growth, and yields an antiexotoxic immune serum. The endotoxin, on the other hand, is heat-stable, is formed in the later period of growth, and is not neutralized by the antiexotoxic serum. The exotoxin exhibits a specific affinity for the central nervous organs in the rabbit, giving rise to a characteristic lesion-mainly, hemorrhages, necroses, and possibly a perivascular infiltration in the gray matter of the upper spinal cord and medulla. The endotoxin exerts a typical action on the intestinal tract, producing edema, hemorrhages, necroses, and ulcerations, especially in the large intestine. In dysentery in man the intestinal lesions predominate, but in severe epidemics paralysis and neuritis have been observed (Osler(17)). These facts become specially significant from the standpoint of the serum therapy of bacillary dysentery. A potent antidysenteric serum should contain antibodies against the exotoxin as well as the endotoxin. That such a serum can be produced in horses has been experimentally demonstrated.

  10. Heat treatment and the use of additives to improve the stability of paralytic shellfish poisoning toxins in shellfish tissue reference materials for internal quality control and proficiency testing.

    PubMed

    Burrell, Stephen; Clion, Valentin; Auroy, Virginie; Foley, Barry; Turner, Andrew D

    2015-06-01

    The need for homogenous reference materials stable for paralytic shellfish toxins is vital for the monitoring and quality assurance of these potent neurotoxins in shellfish. Two stabilisation techniques were investigated, heat treatment through autoclaving and the addition of preserving additives into the tissue matrix. Short and long-term stability experiments as well as homogeneity determination were conducted on materials prepared by both techniques in comparison with an untreated control using two LC-FLD methods. Both techniques improved the stability of the matrix and the PSP toxins present compared to the controls. A material was prepared using the combined techniques of heat treatment followed by spiking with additives and data is presented from this optimised reference material as used over a two year period in the Irish national monitoring program and in a development exercise as part of a proficiency testing scheme operated by QUASIMEME (Quality Assurance of Information for Marine Environmental Monitoring in Europe) since 2011. The results were indicative of the long-term stability of the material as evidenced through consistent assigned values in the case of the proficiency testing scheme and a low relative standard deviation of 10.5% for total toxicity data generated over 24 months.

  11. Pertussis toxin: the cause of the harmful effects and prolonged immunity of whooping cough. A hypothesis.

    PubMed

    Pittman, M

    1979-01-01

    The nature of the pathogenesis and of the prolonged immunity of whooping cough has not been clearly defined. The literature of Bordetella pertussis indicated that only the antigen that induces histamine sensitization, lymphocytosis, and other biological reactions in mice is the cause of the harmful effects and prolonged immunity of whooping cough. This antigen has the general characteristics of bacterial protein exotoxins that cause the harmful effects of infectious diseases such as diphtheria and tetanus. It is proposed that this antigen, which is histamine-sensitizing, lymphocyte-leukocyte-promoting, and islets-activating (HSF-LPF-IAP), be designated pertussis toxin. Agglutinogen, hemagglutinin, and heat-labile (at 56 C) and heat-stable (at 100 C) toxins are no doubt interrelated with the immunologic and/or toxic reactions of whooping cough. It appears that the first defense against the disease is the antibody that prevents adhesion of the bacteria to the cilia of the respiratory epithelium and that the second defense is the antitoxin against pertussis toxin (HSF-LPF-IAP). PMID:233166

  12. Labile sulfide and sulfite in phytochelatin complexes

    SciTech Connect

    Eannetta, N.T.; Steffens, J.C. )

    1989-04-01

    Heavy metals such as cadmium induce tomato cell cultures to synthesize the metal binding polypeptides ({gamma}-Glu-Cys){sub 3} and ({gamma}-Glu-Cys){sub 4}-Gly (phytochelatins). Tomato cells selected for growth on normally lethal concentrations of CdCl{sub 2} synthesize higher quantities of these polypeptides. Cd{sup r} cells are not cross-resistant to other heavy metals, and recent work suggests that metal detoxification by these peptides may be Cd-specific. The occurrence of labile sulfur as a component of the metal complex raises questions concerning possible functions of phytochelatins besides that of Cd binding. The presence of acid-labile sulfide ion in phytochelatin complexes has been reported by several groups. We report the additional finding that labile sulfite is also present in these complexes and in higher amounts than sulfide. Sulfide and sulfite are both released from the metal binding complex by acidification or by treatment with EDTA.

  13. Detection of the heat-stable toxin coding gene (ST-gene) in enterotoxigenic Escherichia coli: development of a colour amplified PCR detection system.

    PubMed

    Fanning, S; O'Mullane, J; O'Meara, D; Ward, A; Joyce, C; Delaney, M; Cryan, B

    1995-12-01

    Screening biological samples using the polymerase chain reaction (PCR) has obvious advantages compared with current molecular analytical methods based on gel electrophoresis and/or hybridisation, both of which are expensive and time-consuming, therefore the development of a PCR assay format that is applicable to large sample numbers and that can readily use equipment commonly found in diagnostic laboratories would be advantageous. This report describes the development of a colour amplified PCR detection system which is simple in design and could be universally applied to the detection of any DNA template. As an example, the system has been applied in the detection of the heat-stable toxin coding gene (ST-gene) from enterotoxigenic Escherichia coli (ETEC). The assay is sensitive, detecting 10 fg of a purified DNA template and 270 cfu of an ST-gene-positive ETEC strain. PMID:8555786

  14. Biosolids-amended soils: Part II. Chemical lability as a measure of contaminant bioaccessability.

    PubMed

    Schwab, A P; Lewis, K; Banks, M K

    2006-10-01

    Biosolids recycling by amending agricultural soils has increased significantly over the last few decades. The presence of contaminants in small, bioavailable quantities has generated concerns about health threats resulting from accumulation of potential toxins in the food chain. In this study, land application of biosolids was evaluated for environmental risk. Chemical lability tests for metals were used for the test soils and included analyses for water soluble, exchangeable, and metals extractable by the physiologically based extraction test. Chemical extractions detected slight increases in labile metal concentrations for many of the treated soils, particularly those receiving long-term applications of 5 years or more. Significantly higher metal concentrations were observed in the soils that had been exposed to biosolids before the U.S. Environmental Protection Agency (Washington, D.C.) 503 Rule (U.S. EPA, 2004) was implemented. PMID:17120442

  15. Effects of atrophic rhinitis induced by Pasteurella multocida toxin on heat production and activity of pigs kept under different climatic conditions.

    PubMed

    van Diemen, P M; Henken, A M; Schrama, J W; Brandsma, H A; Verstegen, M W

    1995-06-01

    Effects of moderate, artificially induced atrophic rhinitis symptoms on level and changes in heat production and activity were determined in pigs kept under different climatic conditions. Eight groups of 30 pigs each, housed in one of two climatically controlled respiration chambers, were exposed to a 2 x 2 factorial arrangement of treatments: challenged with 0 or 13 micrograms of Pasteurella multocida toxin (Pm-T)/mL, and two climatic environments (good: 25 degrees C, or adverse: 15 degrees C with draught periods). The Pm-T challenge reduced (P < .05) day averages of total (HP) and activity-related heat production (Har). The response to Pm-T treatment was similar in both climatic environments. Differences in the heat production and activity caused by the climatic treatment declined (P < .001) with time and acclimation to the environment. Analyses of HP, Har, and activity-free heat production in 12 2-h periods showed a biphasic activity rhythm. Both treatments affected (P < .05) level of HP and Har in several of the 2-h periods, but the biphasic rhythm was not altered. Day averages of Har showed a disposition to be differently affected (P < .068) by Pm-T challenge in the climatic treatments dependent on duration of exposure. This interaction effect (P < .001) seemed to originate from the periods between 1500 and 2100. Therefore, it might be wise to distinguish between overall effects (day means) on total, activity-related, and activity-free heat production and effects within a day (e.g., 2-h means). Treatment with Pm-T seemed to suppress the general well-being of pigs, reducing pigs' activity and food intake.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7673059

  16. Immunogenic properties of trivalent recombinant protein composed of B-subunits of LT, STX-2, and CT toxins.

    PubMed

    Kazemi, Rouhollah; Akhavian, Asal; Amani, Jafar; Salimian, Jafar; Motamedi, Mohammad-Javad; Mousavi, Amir; Jafari, Mahyat; Salmanian, Ali-Hatef

    2016-06-01

    Infectious diarrhoea remains an emerging problem in the world health program. Among diarrheagenic agents, Vibrio cholerae and enterotoxigenic and enterohemorrhagic Escherichia coli are critical enteropathogens. AB5 toxin produced by these bacteria, heat-labile enterotoxin (LT), cholera enterotoxin (CT), and shiga-like cytotoxin (STX) can target the immune system and are subunit vaccine candidates. A chemically-synthesized chimeric construct composed of the binding subunits of these toxins (LTB, STXB, and CTXB) was developed based on bioinformatics studies. The whole chimeric protein (rLSC) and each of the segments (rLTB, rSTXB, and rCTXB) were expressed in a prokaryotic expression system (E. coli), purified, and analysed for their immunogenic properties. The results indicate that these recombinant proteins were effectively able to present appropriate epitopes to an animal model of the immune system which could result in and increase IgG in serum and immune responses that protect against the binding activity of these toxins. The immunological assays revealed that the sera of immunized mice prevented toxins from binding to their specific receptors and neutralized their toxic effects. The proposed construct should be considered as a potent immunogen to prevent toxicity and diarrhoea. PMID:26970204

  17. Immunogenic properties of trivalent recombinant protein composed of B-subunits of LT, STX-2, and CT toxins.

    PubMed

    Kazemi, Rouhollah; Akhavian, Asal; Amani, Jafar; Salimian, Jafar; Motamedi, Mohammad-Javad; Mousavi, Amir; Jafari, Mahyat; Salmanian, Ali-Hatef

    2016-06-01

    Infectious diarrhoea remains an emerging problem in the world health program. Among diarrheagenic agents, Vibrio cholerae and enterotoxigenic and enterohemorrhagic Escherichia coli are critical enteropathogens. AB5 toxin produced by these bacteria, heat-labile enterotoxin (LT), cholera enterotoxin (CT), and shiga-like cytotoxin (STX) can target the immune system and are subunit vaccine candidates. A chemically-synthesized chimeric construct composed of the binding subunits of these toxins (LTB, STXB, and CTXB) was developed based on bioinformatics studies. The whole chimeric protein (rLSC) and each of the segments (rLTB, rSTXB, and rCTXB) were expressed in a prokaryotic expression system (E. coli), purified, and analysed for their immunogenic properties. The results indicate that these recombinant proteins were effectively able to present appropriate epitopes to an animal model of the immune system which could result in and increase IgG in serum and immune responses that protect against the binding activity of these toxins. The immunological assays revealed that the sera of immunized mice prevented toxins from binding to their specific receptors and neutralized their toxic effects. The proposed construct should be considered as a potent immunogen to prevent toxicity and diarrhoea.

  18. Attenuated Escherichia coli strains expressing the colonization factor antigen I (CFA/I) and a detoxified heat-labile enterotoxin (LThK63) enhance clearance of ETEC from the lungs of mice and protect mice from intestinal ETEC colonization and LT-induced fluid accumulation.

    PubMed

    Byrd, Wyatt; Boedeker, Edgar C

    2013-03-15

    Although enterotoxigenic Escherichia coli (ETEC) infections are important causes of infantile and traveler's diarrhea there is no licensed vaccine available for those at-risk. Our goal is to develop a safe, live attenuated ETEC vaccine. We used an attenuated E. coli strain (O157:H7, Δ-intimin, Stx1-neg, Stx2-neg) as a vector (ZCR533) to prepare two vaccine strains, one strain expressing colonization factor antigen I (ZCR533-CFA/I) and one strain expressing CFA/I and a detoxified heat-labile enterotoxin (ZCR533-CFA/I+LThK63) to deliver ETEC antigens to mucosal sites in BALB/c mice. Following intranasal and intragastric immunization with the vaccine strains, serum IgG and IgA antibodies were measured to the CFA/I antigen, however, only serum IgG antibodies were detected to the heat-labile enterotoxin. Intranasal administration of the vaccine strains induced respiratory and intestinal antibody responses to the CFA/I and LT antigens, while intragastric administration induced only intestinal antibody responses with no respiratory antibodies detected to the CFA/I and LT antigens. Mice immunized intranasally with the vaccine strains showed enhanced clearance of wild-type (wt) ETEC bacteria from the lungs. Mice immunized intranasally and intragastrically with the vaccine strains were protected from intestinal colonization following oral challenge with ETEC wt bacteria. Mice immunized intragastrically with the ZCR533-CFA/I+LThK63 vaccine strain had less fluid accumulate in their intestine following challenge with ETEC wt bacteria or with purified LT as compared to the sham mice indicating that the immunized mice were protected from LT-induced intestinal fluid accumulation. Thus, mice intragastrically immunized with the ZCR533-CFA/I+LThK63 vaccine strain were able to effectively neutralize the activity of the LT enterotoxin. However, no difference in intestinal fluid accumulation was detected in the mice immunized intranasally with the vaccine strain as compared to the sham

  19. BOTULINUM TOXIN

    PubMed Central

    Nigam, P K; Nigam, Anjana

    2010-01-01

    Botulinum toxin, one of the most poisonous biological substances known, is a neurotoxin produced by the bacterium Clostridium botulinum. C. botulinum elaborates eight antigenically distinguishable exotoxins (A, B, C1, C2, D, E, F and G). All serotypes interfere with neural transmission by blocking the release of acetylcholine, the principal neurotransmitter at the neuromuscular junction, causing muscle paralysis. The weakness induced by injection with botulinum toxin A usually lasts about three months. Botulinum toxins now play a very significant role in the management of a wide variety of medical conditions, especially strabismus and focal dystonias, hemifacial spasm, and various spastic movement disorders, headaches, hypersalivation, hyperhidrosis, and some chronic conditions that respond only partially to medical treatment. The list of possible new indications is rapidly expanding. The cosmetological applications include correction of lines, creases and wrinkling all over the face, chin, neck, and chest to dermatological applications such as hyperhidrosis. Injections with botulinum toxin are generally well tolerated and side effects are few. A precise knowledge and understanding of the functional anatomy of the mimetic muscles is absolutely necessary to correctly use botulinum toxins in clinical practice. PMID:20418969

  20. Ganglioside Structure Dictates Signal Transduction by Cholera Toxin and Association with Caveolae-like Membrane Domains in Polarized Epithelia

    PubMed Central

    Wolf, Anne A.; Jobling, Michael G.; Wimer-Mackin, Susan; Ferguson-Maltzman, Margaret; Madara, James L.; Holmes, Randall K.; Lencer, Wayne I.

    1998-01-01

    In polarized cells, signal transduction by cholera toxin (CT) requires apical endocytosis and retrograde transport into Golgi cisternae and perhaps ER (Lencer, W.I., C. Constable, S. Moe, M. Jobling, H.M. Webb, S. Ruston, J.L. Madara, T. Hirst, and R. Holmes. 1995. J. Cell Biol. 131:951–962). In this study, we tested whether CT's apical membrane receptor ganglioside GM1 acts specifically in toxin action. To do so, we used CT and the related Escherichia coli heat-labile type II enterotoxin LTIIb. CT and LTIIb distinguish between gangliosides GM1 and GD1a at the cell surface by virtue of their dissimilar receptor-binding B subunits. The enzymatically active A subunits, however, are homologous. While both toxins bound specifically to human intestinal T84 cells (Kd ≈ 5 nM), only CT elicited a cAMP-dependent Cl− secretory response. LTIIb, however, was more potent than CT in eliciting a cAMP-dependent response from mouse Y1 adrenal cells (toxic dose 10 vs. 300 pg/well). In T84 cells, CT fractionated with caveolae-like detergent-insoluble membranes, but LTIIb did not. To investigate further the relationship between the specificity of ganglioside binding and partitioning into detergent-insoluble membranes and signal transduction, CT and LTIIb chimeric toxins were prepared. Analysis of these chimeric toxins confirmed that toxin-induced signal transduction depended critically on the specificity of ganglioside structure. The mechanism(s) by which ganglioside GM1 functions in signal transduction likely depends on coupling CT with caveolae or caveolae-related membrane domains. PMID:9585411

  1. Role of vapBC toxin-antitoxin loci in the thermal stress response of Sulfolobus solfataricus.

    PubMed

    Cooper, Charlotte R; Daugherty, Amanda J; Tachdjian, Sabrina; Blum, Paul H; Kelly, Robert M

    2009-02-01

    TA (toxin-antitoxin) loci are ubiquitous in prokaryotic micro-organisms, including archaea, yet their physiological function is largely unknown. For example, preliminary reports have suggested that TA loci are microbial stress-response elements, although it was recently shown that knocking out all known chromosomally located TA loci in Escherichia coli did not have an impact on survival under certain types of stress. The hyperthermophilic crenarchaeon Sulfolobus solfataricus encodes at least 26 vapBC (where vap is virulence-associated protein) family TA loci in its genome. VapCs are PIN (PilT N-terminus) domain proteins with putative ribonuclease activity, while VapBs are proteolytically labile proteins, which purportedly function to silence VapCs when associated as a cognate pair. Global transcriptional analysis of S. solfataricus heat-shock-response dynamics (temperature shift from 80 to 90 degrees C) revealed that several vapBC genes were triggered by the thermal shift, suggesting a role in heat-shock-response. Indeed, knocking out a specific vapBC locus in S. solfataricus substantially changed the transcriptome and, in one case, rendered the crenarchaeon heat-shock-labile. These findings indicate that more work needs to be done to determine the role of VapBCs in S. solfataricus and other thermophilic archaea, especially with respect to post-transcriptional regulation.

  2. Bovine lactogenic immunity against cholera toxin-related enterotoxins and Vibrio cholerae outer membranes.

    PubMed Central

    Boesman-Finkelstein, M; Walton, N E; Finkelstein, R A

    1989-01-01

    The newly parturient cow secretes large quantities of immunoglobulin G1, a relatively protease- and heat-resistant immunoglobulin, in its colostrum and milk. This study establishes the feasibility of producing protective colostral immunoglobulins by immunizing pregnant cows with cholera toxin (CT), a CT-related enterotoxin from Escherichia coli, and Vibrio cholerae outer membranes (OMs). The OMs were prepared from bacteria grown under iron-replete or iron-deficient (to simulate the in vivo environment) conditions. Immunoglobulins were purified from the colostrum of newly parturient control and immunized cows. The bovine anti-CT and anti-H-LT (CT-related heat-labile enterotoxin produced by diarrheogenic E. coli strains of human origin) antibodies were quantitated by enzyme-linked immunosorbent assays and by neutralization of toxin activity in both Y-1 adrenal cell and infant rabbit assays. The bovine anti-OM antibodies from both high-iron-grown and low-iron-grown vibrios were assessed by bacterial agglutination and by Western blot (immunoblot) analysis of polyacrylamide gel electrophoresis of high-iron-grown and low-iron-grown OMs. To test their protective effect, immunoglobulin preparations were administered orally in infant feeding formula to 6-day-old rabbits. Anti-CT and anti-OM immunoglobulins elicited statistically significant protection against diarrhea in infant rabbits challenged intraintestinally with virulent cholera vibrios. Images PMID:2925248

  3. Enhancement of toxin- and virus-neutralizing capacity of single-domain antibody fragments by N-glycosylation.

    PubMed

    Harmsen, M M; van Solt, C B; Fijten, H P D

    2009-10-01

    Single-domain antibody fragments (VHHs) have several beneficial properties as compared to conventional antibody fragments. However, their small size complicates their toxin- and virus-neutralizing capacity. We isolated 27 VHHs binding Escherichia coli heat-labile toxin and expressed these in Saccharomyces cerevisiae. The most potent neutralizing VHH (LT109) was N-glycosylated, resulting in a large increase in molecular mass. This suggests that N-glycosylation of LT109 improves its neutralizing capacity. Indeed, deglycosylation of LT109 decreased its neutralizing capacity three- to fivefold. We also studied the effect of glycosylation of two previously isolated VHHs on their ability to neutralize foot-and-mouth disease virus. For this purpose, these VHHs that lacked potential N-glycosylation sites were genetically fused to another VHH that was known to be glycosylated. The resulting fusion proteins were also N-glycosylated. They neutralized the virus at at least fourfold-lower VHH concentrations as compared to the single, non-glycosylated VHHs and at at least 50-fold-lower VHH concentrations as compared to their deglycosylated counterparts. Thus, we have shown that N-glycosylation of VHHs contributes to toxin- and virus-neutralizing capacity.

  4. Fate and lability of silver in soils: Effect of ageing

    EPA Science Inventory

    The fate and lability of added soluble Ag in soils over time was examined by measurement of labile metal (E-value) by isotopic dilution using the 110mAg radioactive isotope and the solid-phase speciation of Ag by X-ray absorption near edge structure (XANES) spectrosco...

  5. The 2.3 {angstrom} crystal structure of cholera toxin B subunit pentamer: Choleragenoid

    SciTech Connect

    Zhang, Rong-Guang; Westbrook, M.L.; Maulik, P.R.; Reed, R.A.; Shipley, G.; Westbrook, E.M. |; Scott, D.L.; Otwinowski, Z.

    1996-02-01

    Cholera toxin, a heterohexameric AB{sub 5} enterotoxin released by Vibrio cholera, induces a profuse secretory diarrhea in susceptible hosts. Choleragenoid, the B subunit pentamer of cholera toxin, directs the enzymatic A subunit to its target by binding to GM{sub 1} gangliosides exposed on the luminal surface of intestinal epithelial cells. We have solved the crystal structure of choleragenoid at 2.3 {Angstrom} resolution by combining single isomorphous replacement with non-crystallographic symmetry averaging. The structure of the B subunits, and their pentameric arrangement, closely resembles that reported for the intact holotoxin (choleragen), the heat-labile enterotoxin from E. coli, and for a choleragenoid-GM{sub 1} pentasaccharide complex. In the absence of the A subunit the central cavity of the B pentamer is a highly solvated channel. The binding of the A subunit or the receptor pentasaccharide to choleragenoid has only a modest effect on the local stereochemistry and does not perceptibly alter the subunit interface.

  6. Development of an Immunochromatographic Test Strip for Detection of Cholera Toxin

    PubMed Central

    Yamasaki, Eiki; Sakamoto, Ryuta; Matsumoto, Takashi; Morimatsu, Fumiki; Kurazono, Takayuki; Hiroi, Toyoko; Nair, G. Balakrish; Kurazono, Hisao

    2013-01-01

    Because cholera toxin (CT) is responsible for most of the symptoms induced by Vibrio cholerae infection, detection of CT is critical for diagnosis of the disease. In this study, we constructed an immunochromatographic test strip for detection of CT (CT-IC) with polyclonal antibodies developed against purified recombinant whole CT protein. The detection limit of the CT-IC was 10 ng/mL of purified recombinant CT, and it could detect the CT in culture supernatant of all 15 toxigenic V. cholerae isolates examined, whereas no false-positive signal was detected in all 5 nontoxigenic V. cholerae isolates examined. The specificity of the CT-IC was examined with recombinant heat-labile toxin (LT), which shares high homology with CT, and it was revealed that the minimum detection limit for LT was 100 times higher than that for CT. In addition, lt gene-positive enterotoxigenic Escherichia coli (ETEC) was examined by CT-IC. The false-positive signals were observed in 3 out of 12 ETEC isolates, but these signals were considerably faint. The CT-IC did not develop false-positive signals with all 7 V. parahaemolyticus isolates. These results showed the high specificity of CT-IC and the feasible use of it for the detection and surveillance of toxigenic V. cholerae. PMID:24308002

  7. Phylogenetic Comparisons Reveal Multiple Acquisitions of the Toxin Genes by Enterotoxigenic Escherichia coli Strains of Different Evolutionary Lineages▿ †

    PubMed Central

    Turner, Sue M.; Chaudhuri, Roy R.; Jiang, Zhi-Dong; DuPont, Herbert; Gyles, Carlton; Penn, Charles W.; Pallen, Mark J.; Henderson, Ian R.

    2006-01-01

    Escherichia coli is a diverse bacterial species which is widely distributed in the environment but also exists as a commensal and pathogen of different host species. Human intestinal pathogenic E. coli causes over 160 million cases of diarrhea and an estimated 1 million deaths per year. The majority of deaths are attributable to one pathovar of E. coli, namely, enterotoxigenic E. coli. The pathogenesis of enterotoxigenic E. coli is dependent on the production of a colonization factor to promote adhesion to the intestinal epithelium and the elaboration of heat-labile or heat-stable toxins which induce a secretory diarrhea. Despite the high morbidity and mortality associated with enterotoxigenic E. coli infection, little is known of the genetic background of this global pathogen. Here we demonstrate by multilocus sequence typing that enterotoxigenic E. coli isolates are present in all phylogenetic lineages of E. coli, indicating that acquisition of the toxin genes may be sufficient to generate an enterotoxigenic E. coli strain. In addition, screening of diarrheal isolates for the presence of additional genes previously associated with the virulence of enterotoxigenic E. coli revealed that they were not abundant. These observations have significant implications for disease epidemiology and for the design of effective vaccines. PMID:17050815

  8. Wheat-germ aspartate transcarbamoylase. Purification and cold-lability.

    PubMed Central

    Grayson, J E; Yon, R J; Butterworth, P J

    1979-01-01

    1. Aspartate transcarbamoylase was purified approx. 3000-fold from wheat (Triticum vulgare) germ in 15-20% yield. The product has a specific activity of 14 mumol/min per mg of protein and is approx. 90% pure. The purification scheme includes the use of biospecific "imphilyte" chromatography as described by Yon [Biochem.J.(1977) 161, 233-237]. The enzyme was passed successively through columns of CPAD [N-(3-carboxypropionyl)aminodecyl]-Sepharose in the absence and presence respectively of the ligands UMP and L-aspartate. In the second passage the enzyme was specifically displaced away from impurities with which it co-migrated in the first passage. These two steps contributed a factor of 80 to the overall purification. 2. The enzyme is slowly inactivated on dilution at 0 degrees C and pH 7.0, the inactivation being partially reversible. A detailed investigation of the temperature- and pH-dependence of the cold-inactivation suggested that it was initiated by the perturbation of the pKa values of groups with a moderately high and positive heat of ionization, which were tentatively identified as histidine residues. These findings support a new concept of cold-lability proposed by Bock, Gilbert & Frieden [Biochem. Biophys. Res. Commun. (1975) 66, 564-569]. PMID:43131

  9. Cholera toxin-like toxin released by Salmonella species in the presence of mitomycin C.

    PubMed

    Molina, N C; Peterson, J W

    1980-10-01

    Several serotypes of Salmonella were shown to release increased amounts of a cholera toxin-like toxin during culture in vitro with mitomycin C (MTC). Filter-sterilized culture supernatants containing the toxin caused elongation of Chinese hamster ovary cells, which could be blocked by heating the supernatants at 100 degrees C for 15 min or by adding mixed gangliosides or monospecific cholera antitoxin. When MTC was not added to the Salmonella cultures, little or no toxin was detected in crude, unconcentrated culture supernatants. Optimal production of toxin was observed in the presence of 0.5 micrograms of MTC per ml in shake flask cultures of Casamino Acids-yeast extract medium, Syncase, or peptone saline at 37 degrees C. Meat infusion media (heart infusion and brain heart infusion) plus MTC resulted in poor toxin yield. Culture filtrates frequently could be diluted 1:8 and still result in elongation of Chinese hamster ovary cells. PMID:7002788

  10. Cholera toxin-like toxin released by Salmonella species in the presence of mitomycin C.

    PubMed

    Molina, N C; Peterson, J W

    1980-10-01

    Several serotypes of Salmonella were shown to release increased amounts of a cholera toxin-like toxin during culture in vitro with mitomycin C (MTC). Filter-sterilized culture supernatants containing the toxin caused elongation of Chinese hamster ovary cells, which could be blocked by heating the supernatants at 100 degrees C for 15 min or by adding mixed gangliosides or monospecific cholera antitoxin. When MTC was not added to the Salmonella cultures, little or no toxin was detected in crude, unconcentrated culture supernatants. Optimal production of toxin was observed in the presence of 0.5 micrograms of MTC per ml in shake flask cultures of Casamino Acids-yeast extract medium, Syncase, or peptone saline at 37 degrees C. Meat infusion media (heart infusion and brain heart infusion) plus MTC resulted in poor toxin yield. Culture filtrates frequently could be diluted 1:8 and still result in elongation of Chinese hamster ovary cells.

  11. Bacterial glycosyltransferase toxins.

    PubMed

    Jank, Thomas; Belyi, Yury; Aktories, Klaus

    2015-12-01

    Mono-glycosylation of host proteins is a common mechanism by which bacterial protein toxins manipulate cellular functions of eukaryotic target host cells. Prototypic for this group of glycosyltransferase toxins are Clostridium difficile toxins A and B, which modify guanine nucleotide-binding proteins of the Rho family. However, toxin-induced glycosylation is not restricted to the Clostridia. Various types of bacterial pathogens including Escherichia coli, Yersinia, Photorhabdus and Legionella species produce glycosyltransferase toxins. Recent studies discovered novel unexpected variations in host protein targets and amino acid acceptors of toxin-catalysed glycosylation. These findings open new perspectives in toxin as well as in carbohydrate research.

  12. Why is firefly oxyluciferin a notoriously labile substance?

    PubMed

    Maltsev, Oleg V; Nath, Naba K; Naumov, Panče; Hintermann, Lukas

    2014-01-13

    The chemistry of firefly bioluminescence is important for numerous applications in biochemistry and analytical chemistry. The emitter of this bioluminescent system, firefly oxyluciferin, is difficult to handle. The cause of its lability was clarified while its synthesis was reinvestigated. A side product was identified and characterized by NMR spectroscopy and X-ray crystallography. The reason for the lability of oxyluciferin is now ascribed to autodimerization of the coexisting enol and keto forms in a Mannich-type reaction.

  13. *CYANOBACTERIA AND THEIR TOXINS

    EPA Science Inventory

    Cyanobacteria, or blue-green algae, are naturally-occurring contaminants of surface waters worldwide. These photosynthesizing prokaryotes thrive in warm, shallow, nutrient-rich waters. Many produce potent toxins as secondary metabolites. Cyanobacteria toxins have been document...

  14. Botox (Botulinum Toxin)

    MedlinePlus

    ... people when there are many effective and safe cosmetic procedures that can temporarily reduce a very prominent ... form of botulinum toxin is Type A (Botox® Cosmetic, Allergan, Inc). Botulinum toxin, what we will now ...

  15. Total Dissolved Cobalt and Labile Cobalt in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Saito, M. A.; Noble, A.

    2012-12-01

    This study presents the total and labile dissolved cobalt distributions from the North Atlantic GEOTRACES Zonal Transect expeditions of the fall of 2010 and 2011. Labile cobalt was detected in much of the water column below the euphotic zone, suggesting that strong cobalt binding ligands were not present in excess of the total cobalt concentration. Near complete complexation of cobalt was observed in surface waters, and linear relationships were observed when both total and labile cobalt were compared to phosphate in surface waters, indicative of a strong biological influence on cobalt cycling. Decoupling of cobalt and macronutrients in the surface waters was observed approaching the North American coast, and a relationship between cobalt and salinity was observed, suggesting that coastal inputs may dominate the distributions of cobalt there. In deep waters, both total and labile cobalt were generally lower in concentration than at intermediate depths, which is evidence of scavenging processes removing cobalt from the water column. Elevated concentrations of labile and total cobalt were observed in samples taken within the TAG hydrothermal plume, and a reverse relationship between cobalt and oxygen was observed in the western basin OMZ.

  16. Fate and lability of silver in soils: effect of ageing.

    PubMed

    Settimio, Lara; McLaughlin, Mike J; Kirby, Jason K; Langdon, Kate A; Lombi, Enzo; Donner, Erica; Scheckel, Kirk G

    2014-08-01

    The fate and lability of added soluble Ag in soils over time was examined by measurement of labile metal (E-value) by isotopic dilution using the (110m)Ag radioactive isotope and the solid-phase speciation of Ag by X-ray absorption near edge structure (XANES) spectroscopy. After two weeks of ageing the E-values for Ag decreased by 20-90% with a further decrease of 10-40% after six months. The overall decrease in labile Ag for all soils after the 6 month ageing period was 50-100%. The ageing was more rapid and pronounced in the alkaline soils. XANES results for Ag in soils indicated that for the majority of soils the added Ag(+) was reduced to metallic Ag over time, and associations with Fe-oxohydroxides and reduced S groups in organic matter also decreased Ag lability. Strong positive correlations were found between metallic Ag and non-labile Ag and between organic carbon and Ag bonded with S species.

  17. Clostridium difficile toxin A binding to human intestinal epithelial cells.

    PubMed

    Smith, J A; Cooke, D L; Hyde, S; Borriello, S P; Long, R G

    1997-11-01

    Clostridium difficile radiolabelled toxin A ([3H]-toxin A) bound to human duodenal and colonic epithelial cells isolated from endoscopic biopsies. Binding was greater at 4 degrees C than 37 degrees C, consistent with the thermal binding characteristic of toxin A to a carbohydrate moiety. At 37 degrees C colonic cells bound significantly more [3H]-toxin A than duodenal cells. The amount of [3H]-toxin A binding varied considerably between individuals. [3H]-toxin A was displaced by unlabelled toxin A by 50% for duodenal cells and 70% for colonic cells with 94.3 nM unlabelled toxin A. Low non-displacable binding was observed in some samples at 4 degrees C and 37 degrees C, suggesting that these cells came from individuals incapable of specifically binding toxin. Pre-treating cells with alpha- or beta-galactosidases to cleave terminal alpha- and beta-galactose residues reduced [3H]-toxin A binding. There was also a reduction in [3H]-toxin A binding after heat treating cells, which is suggestive of protein binding. The reduction in binding varied between individuals. The reduction of [3H]-toxin A binding, after the removal of beta-linked galactose units, implicates these as components of the receptor and adds credence to the idea that the Lewis X, Y and I antigens may be involved in toxin A binding to human intestinal epithelial cells. However, because the Lewis antigens do not possess terminal alpha-galactose units, the reduction in binding after alpha-galactosidase treatment suggests that other receptors may be involved in toxin A binding to some human intestinal cells. These data are the first demonstration of direct toxin A binding to human intestinal epithelial cells.

  18. [Techniques of preparation and indications of labile blood products].

    PubMed

    Clément, S

    2011-04-01

    Labile blood products are obtained from samples of whole blood or aphaeresis. The techniques of preparation evolve with technological advances, which allow both an increasing automation and an intensification of the sanitary safety of the blood products. Over the last ten years, thanks to the availability of new technologies, several measures have been introduced in order to reduce the risk of transmission of pathogens and prevent the onset of transfusion-related acute lung injury (TRALI): leukoreduction, use of platelet storage solutions, inactivation of plasma and presumably of platelets in a very near future. The control of transfusion risk also depends on proper use of labile blood products. To assist the prescriber in his treatment options and to standardize practices, the French Agency for Sanitary Safety of Health Products has issued recommendations in terms of utilization of blood products that are detailed in this review of major labile blood products available.

  19. Heated Debates: Hot-Water Immersion or Ice Packs as First Aid for Cnidarian Envenomations?

    PubMed

    Wilcox, Christie L; Yanagihara, Angel A

    2016-04-01

    Cnidarian envenomations are an important public health problem, responsible for more deaths than shark attacks annually. For this reason, optimization of first-aid care is essential. According to the published literature, cnidarian venoms and toxins are heat labile at temperatures safe for human application, which supports the use of hot-water immersion of the sting area(s). However, ice packs are often recommended and used by emergency personnel. After conducting a systematic review of the evidence for the use of heat or ice in the treatment of cnidarian envenomations, we conclude that the majority of studies to date support the use of hot-water immersion for pain relief and improved health outcomes. PMID:27043628

  20. Heated Debates: Hot-Water Immersion or Ice Packs as First Aid for Cnidarian Envenomations?

    PubMed Central

    Wilcox, Christie L.; Yanagihara, Angel A.

    2016-01-01

    Cnidarian envenomations are an important public health problem, responsible for more deaths than shark attacks annually. For this reason, optimization of first-aid care is essential. According to the published literature, cnidarian venoms and toxins are heat labile at temperatures safe for human application, which supports the use of hot-water immersion of the sting area(s). However, ice packs are often recommended and used by emergency personnel. After conducting a systematic review of the evidence for the use of heat or ice in the treatment of cnidarian envenomations, we conclude that the majority of studies to date support the use of hot-water immersion for pain relief and improved health outcomes. PMID:27043628

  1. Heated Debates: Hot-Water Immersion or Ice Packs as First Aid for Cnidarian Envenomations?

    PubMed

    Wilcox, Christie L; Yanagihara, Angel A

    2016-04-01

    Cnidarian envenomations are an important public health problem, responsible for more deaths than shark attacks annually. For this reason, optimization of first-aid care is essential. According to the published literature, cnidarian venoms and toxins are heat labile at temperatures safe for human application, which supports the use of hot-water immersion of the sting area(s). However, ice packs are often recommended and used by emergency personnel. After conducting a systematic review of the evidence for the use of heat or ice in the treatment of cnidarian envenomations, we conclude that the majority of studies to date support the use of hot-water immersion for pain relief and improved health outcomes.

  2. Repeated Labilization-Reconsolidation Processes Strengthen Declarative Memory in Humans

    PubMed Central

    Forcato, Cecilia; Rodríguez, María L. C.; Pedreira, María E.

    2011-01-01

    The idea that memories are immutable after consolidation has been challenged. Several reports have shown that after the presentation of a specific reminder, reactivated old memories become labile and again susceptible to amnesic agents. Such vulnerability diminishes with the progress of time and implies a re-stabilization phase, usually referred to as reconsolidation. To date, the main findings describe the mechanisms associated with the labilization-reconsolidation process, but little is known about its functionality from a biological standpoint. Indeed, two functions have been proposed. One suggests that destabilization of the original memory after the reminder allows the integration of new information into the background of the original memory (memory updating), and the other suggests that the labilization-reconsolidation process strengthens the original memory (memory strengthening). We have previously reported the reconsolidation of human declarative memories, demonstrating memory updating in the framework of reconsolidation. Here we deal with the strengthening function attributed to the reconsolidation process. We triggered labilization-reconsolidation processes successively by repeated presentations of the proper reminder. Participants learned an association between five cue-syllables and their respective response-syllables. Twenty-four hours later, the paired-associate verbal memory was labilized by exposing the subjects to one, two or four reminders. The List-memory was evaluated on Day 3 showing that the memory was improved when at least a second reminder was presented in the time window of the first labilization-reconsolidation process prompted by the earlier reminder. However, the improvement effect was revealed on Day 3, only when at least two reminders were presented on Day2 and not as a consequence of only retrieval. Therefore, we propose central concepts for the reconsolidation process, emphasizing its biological role and the parametrical constrains

  3. Repeated labilization-reconsolidation processes strengthen declarative memory in humans.

    PubMed

    Forcato, Cecilia; Rodríguez, María L C; Pedreira, María E

    2011-01-01

    The idea that memories are immutable after consolidation has been challenged. Several reports have shown that after the presentation of a specific reminder, reactivated old memories become labile and again susceptible to amnesic agents. Such vulnerability diminishes with the progress of time and implies a re-stabilization phase, usually referred to as reconsolidation. To date, the main findings describe the mechanisms associated with the labilization-reconsolidation process, but little is known about its functionality from a biological standpoint. Indeed, two functions have been proposed. One suggests that destabilization of the original memory after the reminder allows the integration of new information into the background of the original memory (memory updating), and the other suggests that the labilization-reconsolidation process strengthens the original memory (memory strengthening). We have previously reported the reconsolidation of human declarative memories, demonstrating memory updating in the framework of reconsolidation. Here we deal with the strengthening function attributed to the reconsolidation process. We triggered labilization-reconsolidation processes successively by repeated presentations of the proper reminder. Participants learned an association between five cue-syllables and their respective response-syllables. Twenty-four hours later, the paired-associate verbal memory was labilized by exposing the subjects to one, two or four reminders. The List-memory was evaluated on Day 3 showing that the memory was improved when at least a second reminder was presented in the time window of the first labilization-reconsolidation process prompted by the earlier reminder. However, the improvement effect was revealed on Day 3, only when at least two reminders were presented on Day 2 and not as a consequence of only retrieval. Therefore, we propose central concepts for the reconsolidation process, emphasizing its biological role and the parametrical

  4. Bioterrorism: toxins as weapons.

    PubMed

    Anderson, Peter D

    2012-04-01

    The potential for biological weapons to be used in terrorism is a real possibility. Biological weapons include infectious agents and toxins. Toxins are poisons produced by living organisms. Toxins relevant to bioterrorism include ricin, botulinum, Clostridium perfrigens epsilson toxin, conotoxins, shigatoxins, saxitoxins, tetrodotoxins, mycotoxins, and nicotine. Toxins have properties of biological and chemical weapons. Unlike pathogens, toxins do not produce an infection. Ricin causes multiorgan toxicity by blocking protein synthesis. Botulinum blocks acetylcholine in the peripheral nervous system leading to muscle paralysis. Epsilon toxin damages cell membranes. Conotoxins block potassium and sodium channels in neurons. Shigatoxins inhibit protein synthesis and induce apoptosis. Saxitoxin and tetrodotoxin inhibit sodium channels in neurons. Mycotoxins include aflatoxins and trichothecenes. Aflatoxins are carcinogens. Trichothecenes inhibit protein and nucleic acid synthesis. Nicotine produces numerous nicotinic effects in the nervous system.

  5. How to Compute Labile Metal-Ligand Equilibria

    ERIC Educational Resources Information Center

    de Levie, Robert

    2007-01-01

    The different methods used for computing labile metal-ligand complexes, which are suitable for an iterative computer solution, are illustrated. The ligand function has allowed students to relegate otherwise tedious iterations to a computer, while retaining complete control over what is calculated.

  6. Neuropsychological Correlates of Emotional Lability in Children with ADHD

    ERIC Educational Resources Information Center

    Banaschewski, Tobias; Jennen-Steinmetz, Christine; Brandeis, Daniel; Buitelaar, Jan K.; Kuntsi, Jonna; Poustka, Luise; Sergeant, Joseph A.; Sonuga-Barke, Edmund J.; Frazier-Wood, Alexis C.; Albrecht, Bjorn; Chen, Wai; Uebel, Henrik; Schlotz, Wolff; van der Meere, Jaap J.; Gill, Michael; Manor, Iris; Miranda, Ana; Mulas, Fernando; Oades, Robert D.; Roeyers, Herbert; Rothenberger, Aribert; Steinhausen, Hans-Christoph; Faraone, Stephen V.; Asherson, Philip

    2012-01-01

    Background: Emotional lability (EL) is commonly seen in patients with attention-deficit/hyperactivity disorder (ADHD). The reasons for this association remain currently unknown. To address this question, we examined the relationship between ADHD and EL symptoms, and performance on a range of neuropsychological tasks to clarify whether EL symptoms…

  7. Memory expression is independent of memory labilization/reconsolidation.

    PubMed

    Barreiro, Karina A; Suárez, Luis D; Lynch, Victoria M; Molina, Víctor A; Delorenzi, Alejandro

    2013-11-01

    There is growing evidence that certain reactivation conditions restrict the onset of both the destabilization phase and the restabilization process or reconsolidation. However, it is not yet clear how changes in memory expression during the retrieval experience can influence the emergence of the labilization/reconsolidation process. To address this issue, we used the context-signal memory model of Chasmagnathus. In this paradigm a short reminder that does not include reinforcement allows us to evaluate memory labilization and reconsolidation, whereas a short but reinforced reminder restricts the onset of such a process. The current study investigated the effects of the glutamate antagonists, APV (0.6 or 1.5 μg/g) and CNQX (1 μg/g), prior to the reminder session on both behavioral expression and the reconsolidation process. Under conditions where the reminder does not initiate the labilization/reconsolidation process, APV prevented memory expression without affecting long-term memory retention. In contrast, APV induced amnesic effects in the long-term when administered before a reminder session that triggers reconsolidation. Under the present parametric conditions, the administration of CNQX prior to the reminder that allows memory to enter reconsolidation impairs this process without disrupting memory expression. Overall, the present findings suggest that memory reactivation--but not memory expression--is necessary for labilization and reconsolidation. Retrieval and memory expression therefore appear not to be interchangeable concepts.

  8. Carbohydrate binding specificities and crystal structure of the cholera toxin-like B-subunit from Citrobacter freundii.

    PubMed

    Jansson, Lena; Angström, Jonas; Lebens, Michael; Imberty, Anne; Varrot, Annabelle; Teneberg, Susann

    2010-05-01

    Enterotoxigenic Escherichia coli and Vibrio cholerae are well known causative agents of severe diarrheal diseases. Both pathogens produce AB(5) toxins, with one enzymatically active A-subunit and a pentamer of receptor-binding B-subunits. The primary receptor for both B-subunits is the GM1 ganglioside (Galbeta3GalNAcbeta4(NeuAcalpha3)Galbeta4GlcbetaCer), but the B-subunits from porcine isolates of E. coli also bind neolacto-(Galbeta4GlcNAcbeta-)terminated glycoconjugates and the B-subunits from human isolates of E. coli (hLTB) have affinity for blood group A type 2-(GalNAcalpha3(Fucalpha2)Galbeta4GlcNAcbeta-)terminated glycoconjugates. A B-subunit with 73% sequence identity to the B-subunits of cholera toxin and the heat-labile toxin of E. coli is produced by certain strains of enteropathogenic E. coli and by Citrobacter freundii. This C. freundii B-subunit (CFXB) has now been expressed in V. cholerae, and isolated in high yields. Glycosphingolipid binding studies show that CFXB binds to the GM1 ganglioside with high affinity. In addition, CFXB has high affinity for both neolacto-terminated and blood group A type 2-terminated glycoconjugates. The crystal structure of the pentameric arrangement of C. freundii B-subunits display high structural similarity with related proteins from E. coli and V. cholerae and oligosaccharide binding sites can be identified on the protein surface. Small changes in the 88-95 loop connecting the GM1 and blood group A binding sites explains the minor changes in affinity seen for these two ligands. However, the enhanced affinity of CFXB for neolacto-terminated structures can be sought in the Lys34Tyr substitution affording additional hydrogen bond interactions between the tyrosyl side chain and the GlcNAcbeta3Galb4Glcbeta1 segment of neolactotetraosylceramide via bridging water molecules.

  9. Nanoparticle-detained toxins for safe and effective vaccination

    NASA Astrophysics Data System (ADS)

    Hu, Che-Ming J.; Fang, Ronnie H.; Luk, Brian T.; Zhang, Liangfang

    2013-12-01

    Toxoid vaccines--vaccines based on inactivated bacterial toxins--are routinely used to promote antitoxin immunity for the treatment and prevention of bacterial infections. Following chemical or heat denaturation, inactivated toxins can be administered to mount toxin-specific immune responses. However, retaining faithful antigenic presentation while removing toxin virulence remains a major challenge and presents a trade-off between efficacy and safety in toxoid development. Here, we show a nanoparticle-based toxin-detainment strategy that safely delivers non-disrupted pore-forming toxins for immune processing. Using erythrocyte membrane-coated nanoparticles and staphylococcal α-haemolysin, we demonstrate effective virulence neutralization via spontaneous particle entrapment. Compared with vaccination with heat-denatured toxin, mice vaccinated with the nanoparticle-detained toxin showed superior protective immunity against toxin-mediated adverse effects. We find that the non-disruptive detoxification approach benefited the immunogenicity and efficacy of toxoid vaccines. We anticipate that this study will open new possibilities in the preparation of antitoxin vaccines against the many virulence factors that threaten public health.

  10. [Intoxication of botulinum toxin].

    PubMed

    Chudzicka, Aleksandra

    2015-09-01

    Botulinum toxin is an egzotoxin produced by Gram positive bacteria Clostridium botulinum. It is among the most potent toxins known. The 3 main clinical presentations of botulism are as follows: foodborne botulism, infant botulism and wound botulism. The main symptom of intoxication is flat muscles paralysis. The treatment is supportive care and administration of antitoxin. In prevention the correct preparing of canned food is most important. Botulinum toxin is accepted as a biological weapon.

  11. [Intoxication of botulinum toxin].

    PubMed

    Chudzicka, Aleksandra

    2015-09-01

    Botulinum toxin is an egzotoxin produced by Gram positive bacteria Clostridium botulinum. It is among the most potent toxins known. The 3 main clinical presentations of botulism are as follows: foodborne botulism, infant botulism and wound botulism. The main symptom of intoxication is flat muscles paralysis. The treatment is supportive care and administration of antitoxin. In prevention the correct preparing of canned food is most important. Botulinum toxin is accepted as a biological weapon. PMID:26449577

  12. Botulinum toxin injection - larynx

    MedlinePlus

    Injection laryngoplasty; Botox-larynx: spasmodic dysphonia-BTX; Essential voice tremor (EVT)-btx; Glottic insufficiency; Percutaneous electromyography-guided botulinum toxin treatment; Percutaneous indirect laryngoscopy- ...

  13. Heterologous Expression of Toxins from Bacterial Toxin-Antitoxin Systems in Eukaryotic Cells: Strategies and Applications.

    PubMed

    Yeo, Chew Chieng; Abu Bakar, Fauziah; Chan, Wai Ting; Espinosa, Manuel; Harikrishna, Jennifer Ann

    2016-02-01

    Toxin-antitoxin (TA) systems are found in nearly all prokaryotic genomes and usually consist of a pair of co-transcribed genes, one of which encodes a stable toxin and the other, its cognate labile antitoxin. Certain environmental and physiological cues trigger the degradation of the antitoxin, causing activation of the toxin, leading either to the death or stasis of the host cell. TA systems have a variety of functions in the bacterial cell, including acting as mediators of programmed cell death, the induction of a dormant state known as persistence and the stable maintenance of plasmids and other mobile genetic elements. Some bacterial TA systems are functional when expressed in eukaryotic cells and this has led to several innovative applications, which are the subject of this review. Here, we look at how bacterial TA systems have been utilized for the genetic manipulation of yeasts and other eukaryotes, for the containment of genetically modified organisms, and for the engineering of high expression eukaryotic cell lines. We also examine how TA systems have been adopted as an important tool in developmental biology research for the ablation of specific cells and the potential for utility of TA systems in antiviral and anticancer gene therapies. PMID:26907343

  14. Heterologous Expression of Toxins from Bacterial Toxin-Antitoxin Systems in Eukaryotic Cells: Strategies and Applications.

    PubMed

    Yeo, Chew Chieng; Abu Bakar, Fauziah; Chan, Wai Ting; Espinosa, Manuel; Harikrishna, Jennifer Ann

    2016-02-19

    Toxin-antitoxin (TA) systems are found in nearly all prokaryotic genomes and usually consist of a pair of co-transcribed genes, one of which encodes a stable toxin and the other, its cognate labile antitoxin. Certain environmental and physiological cues trigger the degradation of the antitoxin, causing activation of the toxin, leading either to the death or stasis of the host cell. TA systems have a variety of functions in the bacterial cell, including acting as mediators of programmed cell death, the induction of a dormant state known as persistence and the stable maintenance of plasmids and other mobile genetic elements. Some bacterial TA systems are functional when expressed in eukaryotic cells and this has led to several innovative applications, which are the subject of this review. Here, we look at how bacterial TA systems have been utilized for the genetic manipulation of yeasts and other eukaryotes, for the containment of genetically modified organisms, and for the engineering of high expression eukaryotic cell lines. We also examine how TA systems have been adopted as an important tool in developmental biology research for the ablation of specific cells and the potential for utility of TA systems in antiviral and anticancer gene therapies.

  15. Heterologous Expression of Toxins from Bacterial Toxin-Antitoxin Systems in Eukaryotic Cells: Strategies and Applications

    PubMed Central

    Yeo, Chew Chieng; Abu Bakar, Fauziah; Chan, Wai Ting; Espinosa, Manuel; Harikrishna, Jennifer Ann

    2016-01-01

    Toxin-antitoxin (TA) systems are found in nearly all prokaryotic genomes and usually consist of a pair of co-transcribed genes, one of which encodes a stable toxin and the other, its cognate labile antitoxin. Certain environmental and physiological cues trigger the degradation of the antitoxin, causing activation of the toxin, leading either to the death or stasis of the host cell. TA systems have a variety of functions in the bacterial cell, including acting as mediators of programmed cell death, the induction of a dormant state known as persistence and the stable maintenance of plasmids and other mobile genetic elements. Some bacterial TA systems are functional when expressed in eukaryotic cells and this has led to several innovative applications, which are the subject of this review. Here, we look at how bacterial TA systems have been utilized for the genetic manipulation of yeasts and other eukaryotes, for the containment of genetically modified organisms, and for the engineering of high expression eukaryotic cell lines. We also examine how TA systems have been adopted as an important tool in developmental biology research for the ablation of specific cells and the potential for utility of TA systems in antiviral and anticancer gene therapies. PMID:26907343

  16. Quantification of Labile Soil Mercury by Stable Isotope Dilution Techniques

    NASA Astrophysics Data System (ADS)

    Shetaya, Waleed; Huang, Jen-How; Osterwalder, Stefan; Alewell, Christine

    2016-04-01

    Mercury (Hg) is a toxic element that can cause severe health problems to humans. Mercury is emitted to the atmosphere from both natural and anthropogenic sources and can be transported over long distances before it is deposited to aquatic and terrestrial environments. Aside from accumulation in soil solid phases, Hg deposited in soils may migrate to surface- and ground-water or enter the food chain, depending on its lability. There are many operationally-defined extraction methods proposed to quantify soil labile metals. However, these methods are by definition prone to inaccuracies such as non-selectivity, underestimation or overestimation of the labile metal pool. The isotopic dilution technique (ID) is currently the most promising method for discrimination between labile and non-labile metal fractions in soil with a minimum disturbance to soil-solid phases. ID assesses the reactive metal pool in soil by defining the fraction of metal both in solid and solution phases that is isotopically-exchangeable known as the 'E-value'. The 'E-value' represents the metal fraction in a dynamic equilibrium with the solution phase and is potentially accessible to plants. This is carried out by addition of an enriched metal isotope to soil suspensions and quantifying the fraction of metal that is able to freely exchange with the added isotope by measuring the equilibrium isotopic ratio by ICP-MS. E-value (mg kg‑1) is then calculated as follows: E-Value = (Msoil/ W) (CspikeVspike/ Mspike) (Iso1IAspike ‑Iso2IAspikeRss / Iso2IAsoil Rss - Iso1IAsoil) where M is the average atomic mass of the metal in the soil or the spike, W is the mass of soil (kg), Cspike is the concentration of the metal in the spike (mg L‑1), Vspike is the volume of spike (L), IA is isotopic abundance, and Rss is the equilibrium ratio of isotopic abundances (Iso1:Iso2). Isotopic dilution has been successfully applied to determine E-values for several elements. However, to our knowledge, this method has not

  17. Quantification of Labile Soil Mercury by Stable Isotope Dilution Techniques

    NASA Astrophysics Data System (ADS)

    Shetaya, Waleed; Huang, Jen-How; Osterwalder, Stefan; Alewell, Christine

    2016-04-01

    Mercury (Hg) is a toxic element that can cause severe health problems to humans. Mercury is emitted to the atmosphere from both natural and anthropogenic sources and can be transported over long distances before it is deposited to aquatic and terrestrial environments. Aside from accumulation in soil solid phases, Hg deposited in soils may migrate to surface- and ground-water or enter the food chain, depending on its lability. There are many operationally-defined extraction methods proposed to quantify soil labile metals. However, these methods are by definition prone to inaccuracies such as non-selectivity, underestimation or overestimation of the labile metal pool. The isotopic dilution technique (ID) is currently the most promising method for discrimination between labile and non-labile metal fractions in soil with a minimum disturbance to soil-solid phases. ID assesses the reactive metal pool in soil by defining the fraction of metal both in solid and solution phases that is isotopically-exchangeable known as the 'E-value'. The 'E-value' represents the metal fraction in a dynamic equilibrium with the solution phase and is potentially accessible to plants. This is carried out by addition of an enriched metal isotope to soil suspensions and quantifying the fraction of metal that is able to freely exchange with the added isotope by measuring the equilibrium isotopic ratio by ICP-MS. E-value (mg kg-1) is then calculated as follows: E-Value = (Msoil/ W) (CspikeVspike/ Mspike) (Iso1IAspike -Iso2IAspikeRss / Iso2IAsoil Rss - Iso1IAsoil) where M is the average atomic mass of the metal in the soil or the spike, W is the mass of soil (kg), Cspike is the concentration of the metal in the spike (mg L-1), Vspike is the volume of spike (L), IA is isotopic abundance, and Rss is the equilibrium ratio of isotopic abundances (Iso1:Iso2). Isotopic dilution has been successfully applied to determine E-values for several elements. However, to our knowledge, this method has not yet

  18. Toxin-induced resistance in Bacillus anthracis lethal toxin-treated macrophages

    PubMed Central

    Salles, Isabelle I.; Tucker, Amy E.; Voth, Daniel E.; Ballard, Jimmy D.

    2003-01-01

    In the current study, we show that macrophages adaptively resist anthrax lethal toxin (LT) through a toxin-activated process termed toxin-induced resistance (TIR). TIR was triggered by pretreatment of RAW 264.7 or J774A.1 macrophages with a low dose of LT for at least 6 h, which resulted in resistance to high doses of LT for 96 h. Activation of TIR required functional toxin, because LT subunits, mutants, and heat-inactivated toxin were unable to trigger resistance. TIR macrophages were not altered in toxin receptor levels or cell cycle profiles. Treatment of TIR macrophages with high doses of LT resulted in a sustained decline in full-length mitogen-activated protein kinase kinase 2, a known target of lethal factor, and a marked reduction in diphosphorylated extracellular response kinases 1,2 for 24 h. However, despite the sustained loss of full-length mitogen-activated protein kinase kinase 2, by 48 h, TIR macrophages regained diphosphorylated extracellular response kinases 1,2, suggesting an adaptation led to recovery of this signaling pathway. TIR macrophages were also able to maintain normal levels of ubiquitinylated proteins, whereas sensitive cells show a rapid reduction in ubiquitin-modified proteins before cell death, indicating a possible alteration in proteasome activity contributed to resistance. These results provide a paradigm for toxin-cell interactions and suggest macrophages are capable of adapting to and tolerating toxic doses of LT. PMID:14519843

  19. Hot Stuff: Lability of Forest Floor DOM to Aerobic Degradation

    NASA Astrophysics Data System (ADS)

    Bourbonniere, R. A.; Creed, I. F.; Kapila, R.; Collins, J.

    2004-05-01

    The hypothesis that the lability of DOM to aerobic microbial degradation to CO2 is related to its age and character is tested in an incubation study conducted using an assemblage of soil bacteria in their natural state. Extracts (WF) of leaf and forest floor material characterized by different degrees of degradation: green leaves, fresh fallen leaves, litter (one year weathering), fibric matter, hemic matter and peat were used in this study. The working hypothesis is that these extracts represent a chronosequence of degradation and DOM extracted from them might also represent a similar lability sequence. As well aliquots of the WF extracts were processed to remove DOM fractions. Thus a fulvic acid (FA) fraction was made by precipitating and removing humic acid, and a hydrophilic fraction (HPI) by removing hydrophobics from the FA using XAD-8 resin. Incubations were carried out on all three DOM solutions from each extract to determine if there were differences in lability among the fractions. When comparing the WF solutions for CO2 production, the green leaves, litter, fibric and hemic extracts showed approximately the same CO2 yield, on an equal C basis, and the fresh fallen leaves and peat produced less. For five of the six extracts the respective WF and HPI solutions yielded nearly the same quantity of CO2 per mg C suggesting that the HPI component contributes almost all the lability. Furthermore the magnitudes of the C-normalized CO2 yield for these solutions are similar to that for glucose, which fractionates as HPI. For the same five extracts the FA solution yielded lower quantities of CO2, on an equal C basis, than WF and HPI suggesting that the hydrophobic content of the extracts may inhibit aerobic degradation. The peat extract solutions yielded a different CO2 production distribution with the HPI only slightly higher than the FA which in turn was much greater than WF. The material from which this extract was made is much older and contains significant HA

  20. Long-Term Sentinel Surveillance for Enterotoxigenic Escherichia coli and Non-O157 Shiga Toxin-Producing E. coli in Minnesota

    PubMed Central

    Medus, Carlota; Besser, John M.; Juni, Billie A.; Koziol, Bonnie; Lappi, Victoria; Smith, Kirk E.; Hedberg, Craig W.

    2016-01-01

    Background. Enterotoxigenic Escherichia coli (ETEC) and non-O157 Shiga toxin-producing E. coli (STEC) are not detected by conventional culture methods. The prevalence of ETEC infections in the United States is unknown, and recognized cases are primarily associated with foreign travel. Gaps remain in our understanding of STEC epidemiology. Methods. Two sentinel surveillance sites were enrolled: an urban health maintenance organization laboratory (Laboratory A) and a rural hospital laboratory (Laboratory B). Residual sorbitol MacConkey (SMAC) plates from stool cultures performed at Laboratory A (1996–2006) and Laboratory B (2000–2008) were collected. Colony sweeps from SMAC plates were tested for genes encoding STEC toxins stx1 and stx2 (1996–2008) and ETEC heat-labile and heat-stable toxins eltB, estA 1, 2 and 3 (2000–2008) by polymerase chain reaction (PCR)-based assays. Results. In Laboratory A, a bacterial pathogen was identified in 7.0% of 21 970 specimens. During 1996–2006, Campylobacter was the most common bacterial pathogen (2.7% of cultures), followed by Salmonella (1.2%), Shigella (1.0%), and STEC (0.9%). Among STEC (n = 196), O157 was the most common serogroup (31%). During 2000–2006, ETEC (1.9%) was the second most common bacterial pathogen after Campylobacter (2.6%). In Laboratory B, of 19 293 specimens tested, a bacterial pathogen was identified for 5.5%, including Campylobacter (2.1%), STEC (1.3%), Salmonella (1.0%), and ETEC (0.8%). Among STEC (n = 253), O157 was the leading serogroup (35%). Among ETEC cases, 61% traveled internationally. Conclusions. Enterotoxigenic E. coli and STEC infections were as common as most other enteric bacterial pathogens, and ETEC may be detected more frequently by culture-independent multiplex PCR diagnostic methods. A high proportion of ETEC cases were domestically acquired. PMID:26913288

  1. Involvement of intracellular labile zinc in suppression of DEVD-caspase activity in human neuroblastoma cells.

    PubMed

    Ho, L H; Ratnaike, R N; Zalewski, P D

    2000-02-01

    Age-related tissue Zn deficiency may contribute to neuronal and glial cell death by apoptosis in Alzheimer's dementia. To investigate this, we studied the effects of increasing or decreasing the levels of intracellular labile Zn on apoptosis of human neuroblastoma BE(2)-C cells in vitro. BE(2)-C cells were primed for 18 h with butyrate (1 mM) before addition of staurosporine (1 microM), an effector enzyme of apoptosis, for a further 3 h to induce DEVD-caspase activity. An increase in intracellular Zn using Zn ionophore pyrithione suppressed DEVD-caspase activity, while a decrease in intracellular Zn induced by Zn chelator TPEN mimicked staurosporine by activating DEVD-caspase in butyrate-primed cells. The distribution of intracellular Zn in the cells was demonstrated with the UV-excitable Zn-specific fluorophore Zinquin. Confocal images showed distinct cytoplasmic and cytoskeletal fluorescence. We propose that Zn decreases the level of apoptosis in neuronal cells exposed to toxins, possibly by stabilizing their cytoskeleton.

  2. Microwave heating inactivates Shiga Toxin (Stx2) in reconstituted fat-free Milk and adversely affects the nutritional value of cell culture medium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Microwave exposure is a convenient and widely used method for defrosting, heating, and cooking numerous foods. Microwave cooking is also reported to kill pathogenic microorganisms that often contaminate food. Microwaves act by causing polar molecules in food, such as water, to rapidly rotate, thus...

  3. Toxins from Bacteria

    PubMed Central

    Henkel, James S.; Baldwin, Michael R.; Barbieri, Joseph T.

    2010-01-01

    Bacterial toxins damage the host at the site of bacterial infection or distanced from the site of infections. Bacterial toxins can be single proteins or organized as oligomeric protein complexes and are organized with distinct AB structure-function properties. The A domain encodes a catalytic activity; ADP-ribosylation of host proteins is the earliest post-translational modification determine to be performed by bacterial toxin, and now include glucosylation and proteolysis among other s. Bacterial toxins also catalyze the non-covalent modification of host protein function or can modify host cell properties through direct protein-protein interactions. The B domain includes two functional domains: a receptor-binding domain, which defines the tropism of a toxin for a cell and a translocation domain that delivers A domain across a lipid bilayer, either on the plasma membrane or the endosome. Bacterial toxins are often characterized based upon the section mechanism that delivers the toxin out of the bacterium, termed type I–VII. This review will overview the major families of bacterial toxins and will also describe the specific structure-function properties of the botulinum neurotoxins. PMID:20358680

  4. Defense against toxin weapons

    SciTech Connect

    Franz, D.R.

    1994-01-01

    The purpose of this manual is to provide basic information on biological toxins to military leaders and health-care providers at all levels to help them make informed decisions on protecting their troops from toxins. Much of the information contained herein will also be of interest to individuals charged with countering domestic and international terrorism. We typically fear what we do not understand.

  5. Labile methyl balances for normal humans on various dietary regimens.

    PubMed

    Mudd, S H; Poole, J R

    1975-06-01

    Normal young adult male and female subjects were maintained on fixed dietary regimens which were either essentially normal or were semisynthetic and curtailed in methionine and choline intakes and virtually free of cystine. The subjects maintained stable weights and remained in positive nitrogen balance or within the zone of sulfur equilibrium. Choline intakes were calculated, and urinary excretions of creatinine, creatine, and sacrosine were measured. Creatinine excretions of male subjects on essentially normal diets outweighed the total intakes of labile methyl groups. Taking into account the excretions of additional methylated compounds, as judged from published values, it appears that methyl neogenesis must normally play a role in both males and females. When labile methyl intake is curtailed, de novo formation of methyl groups is quantitatively more significant than ingestion of preformed methyl moieties. On the normal diets used in these experiments, the average homocysteinyl moiety in males cycled between methionine and homocysteine at least 1.9 times before being converted to cystathionine. For females, the average number of cycles was at least 1.5. When labile methyl intake was curtailed, the average number of cycles rose to 3.9 for males and 3.0 for females under the conditions employed.

  6. Labile disulfide bonds are common at the leucocyte cell surface

    PubMed Central

    Metcalfe, Clive; Cresswell, Peter; Ciaccia, Laura; Thomas, Benjamin; Barclay, A. Neil

    2011-01-01

    Redox conditions change in events such as immune and platelet activation, and during viral infection, but the biochemical consequences are not well characterized. There is evidence that some disulfide bonds in membrane proteins are labile while others that are probably structurally important are not exposed at the protein surface. We have developed a proteomic/mass spectrometry method to screen for and identify non-structural, redox-labile disulfide bonds in leucocyte cell-surface proteins. These labile disulfide bonds are common, with several classes of proteins being identified and around 30 membrane proteins regularly identified under different reducing conditions including using enzymes such as thioredoxin. The proteins identified include integrins, receptors, transporters and cell–cell recognition proteins. In many cases, at least one cysteine residue was identified by mass spectrometry as being modified by the reduction process. In some cases, functional changes are predicted (e.g. in integrins and cytokine receptors) but the scale of molecular changes in membrane proteins observed suggests that widespread effects are likely on many different types of proteins including enzymes, adhesion proteins and transporters. The results imply that membrane protein activity is being modulated by a ‘redox regulator’ mechanism. PMID:22645650

  7. Fluxionality and lability in rhenium 4'-hydroxyterpyridine complexes: evidence for an associative mechanism and correlated fluxionality and lability.

    PubMed

    Fernández-Moreira, Vanesa; Thorp-Greenwood, Flora L; Arthur, Richard J; Kariuki, Benson M; Jenkins, Robert L; Coogan, Michael P

    2010-08-28

    The complexes [ReX(CO)(3)(N,N-eta(2)-4'-hydroxy-2-2',6'-2''-terpyridine)] (X = Cl,Br,I) have been synthesised and their ligand exchange reactions and fluxionality of the terpyridine unit studied. The halides are far more labile in these species than in analogous bipyridines, and it is proposed that the ligand fluxionality is involved in this reactivity. Structural studies of the family are reported along with spectroscopic studies including variable temperature NMR which is used to demonstrate a negative entropy of activation for the fluxional process. Synthesis of an analogue which is incapable of fluxional behaviour confirms the link between fluxionality and lability in these complexes.

  8. Understanding malarial toxins.

    PubMed

    Starkl Renar, Katarina; Iskra, Jernej; Križaj, Igor

    2016-09-01

    Recognized since antiquity, malaria is one of the most infamous and widespread infectious diseases in humans and, although the death rate during the last century has been diminishing, it still accounts for more than a half million deaths annually. It is caused by the Plasmodium parasite and typical symptoms include fever, shivering, headache, diaphoresis and nausea, all resulting from an excessive inflammatory response induced by malarial toxins released into the victim's bloodstream. These toxins are hemozoin and glycosylphosphatidylinositols. The former is the final product of the parasite's detoxification of haeme, a by-product of haemoglobin catabolism, while the latter anchor proteins to the Plasmodium cell surface or occur as free molecules. Currently, only two groups of antimalarial toxin drugs exist on the market, quinolines and artemisinins. As we describe, they both target biosynthesis of hemozoin. Other substances, currently in various phases of clinical trials, are directed towards biosynthesis of glycosylphosphatidylinositol, formation of hemozoin, or attenuation of the inflammatory response of the patient. Among the innovative approaches to alleviating the effects of malarial toxins, is the development of antimalarial toxin vaccines. In this review the most important lessons learned from the use of treatments directed against the action of malarial toxins in antimalarial therapy are emphasized and the most relevant and promising directions for future research in obtaining novel antimalarial agents acting on malarial toxins are discussed.

  9. Understanding malarial toxins.

    PubMed

    Starkl Renar, Katarina; Iskra, Jernej; Križaj, Igor

    2016-09-01

    Recognized since antiquity, malaria is one of the most infamous and widespread infectious diseases in humans and, although the death rate during the last century has been diminishing, it still accounts for more than a half million deaths annually. It is caused by the Plasmodium parasite and typical symptoms include fever, shivering, headache, diaphoresis and nausea, all resulting from an excessive inflammatory response induced by malarial toxins released into the victim's bloodstream. These toxins are hemozoin and glycosylphosphatidylinositols. The former is the final product of the parasite's detoxification of haeme, a by-product of haemoglobin catabolism, while the latter anchor proteins to the Plasmodium cell surface or occur as free molecules. Currently, only two groups of antimalarial toxin drugs exist on the market, quinolines and artemisinins. As we describe, they both target biosynthesis of hemozoin. Other substances, currently in various phases of clinical trials, are directed towards biosynthesis of glycosylphosphatidylinositol, formation of hemozoin, or attenuation of the inflammatory response of the patient. Among the innovative approaches to alleviating the effects of malarial toxins, is the development of antimalarial toxin vaccines. In this review the most important lessons learned from the use of treatments directed against the action of malarial toxins in antimalarial therapy are emphasized and the most relevant and promising directions for future research in obtaining novel antimalarial agents acting on malarial toxins are discussed. PMID:27353131

  10. Biochemical and molecular characterisation of cubozoan protein toxins.

    PubMed

    Brinkman, Diane L; Burnell, James N

    2009-12-15

    Class Cubozoa includes several species of box jellyfish that are harmful to humans. The venoms of box jellyfish are stored and discharged by nematocysts and contain a variety of bioactive proteins that are cytolytic, cytotoxic, inflammatory or lethal. Although cubozoan venoms generally share similar biological activities, the diverse range and severity of effects caused by different species indicate that their venoms vary in protein composition, activity and potency. To date, few individual venom proteins have been thoroughly characterised, however, accumulating evidence suggests that cubozoan jellyfish produce at least one group of homologous bioactive proteins that are labile, basic, haemolytic and similar in molecular mass (42-46 kDa). The novel box jellyfish toxins are also potentially lethal and the cause of cutaneous pain, inflammation and necrosis, similar to that observed in envenomed humans. Secondary structure analysis and remote protein homology predictions suggest that the box jellyfish toxins may act as alpha-pore-forming toxins. However, more research is required to elucidate their structures and investigate their mechanism(s) of action. The biological, biochemical and molecular characteristics of cubozoan venoms and their bioactive protein components are reviewed, with particular focus on cubozoan cytolysins and the newly emerging family of box jellyfish toxins. PMID:19232527

  11. Biochemical and molecular characterisation of cubozoan protein toxins.

    PubMed

    Brinkman, Diane L; Burnell, James N

    2009-12-15

    Class Cubozoa includes several species of box jellyfish that are harmful to humans. The venoms of box jellyfish are stored and discharged by nematocysts and contain a variety of bioactive proteins that are cytolytic, cytotoxic, inflammatory or lethal. Although cubozoan venoms generally share similar biological activities, the diverse range and severity of effects caused by different species indicate that their venoms vary in protein composition, activity and potency. To date, few individual venom proteins have been thoroughly characterised, however, accumulating evidence suggests that cubozoan jellyfish produce at least one group of homologous bioactive proteins that are labile, basic, haemolytic and similar in molecular mass (42-46 kDa). The novel box jellyfish toxins are also potentially lethal and the cause of cutaneous pain, inflammation and necrosis, similar to that observed in envenomed humans. Secondary structure analysis and remote protein homology predictions suggest that the box jellyfish toxins may act as alpha-pore-forming toxins. However, more research is required to elucidate their structures and investigate their mechanism(s) of action. The biological, biochemical and molecular characteristics of cubozoan venoms and their bioactive protein components are reviewed, with particular focus on cubozoan cytolysins and the newly emerging family of box jellyfish toxins.

  12. Heat-Stable Enterotoxin of Enterotoxigenic Escherichia coli as a Vaccine Target ▿

    PubMed Central

    Taxt, Arne; Aasland, Rein; Sommerfelt, Halvor; Nataro, James; Puntervoll, Pål

    2010-01-01

    Enterotoxigenic Escherichia coli (ETEC) is responsible for 280 million to 400 million episodes of diarrhea and about 380,000 deaths annually. Epidemiological data suggest that ETEC strains which secrete heat-stable toxin (ST), alone or in combination with heat-labile toxin (LT), induce the most severe disease among children in developing countries. This makes ST an attractive target for inclusion in an ETEC vaccine. ST is released upon colonization of the small intestine and activates the guanylate cyclase C receptor, causing profuse diarrhea. To generate a successful toxoid, ST must be made immunogenic and nontoxic. Due to its small size, ST is nonimmunogenic in its natural form but becomes immunogenic when coupled to an appropriate large-molecular-weight carrier. This has been successfully achieved with several carriers, using either chemical conjugation or recombinant fusion techniques. Coupling of ST to a carrier may reduce toxicity, but further reduction by mutagenesis is desired to obtain a safe vaccine. More than 30 ST mutants with effects on toxicity have been reported. Some of these mutants, however, have lost the ability to elicit neutralizing immune responses to the native toxin. Due to the small size of ST, separating toxicity from antigenicity is a particular challenge that must be met. Another obstacle to vaccine development is possible cross-reactivity between anti-ST antibodies and the endogenous ligands guanylin and uroguanylin, caused by structural similarity to ST. Here we review the molecular and biological properties of ST and discuss strategies for developing an ETEC vaccine that incorporates immunogenic and nontoxic derivatives of the ST toxin. PMID:20231404

  13. Direct cytotoxic action of Shiga toxin on human vascular endothelial cells.

    PubMed Central

    Obrig, T G; Del Vecchio, P J; Brown, J E; Moran, T P; Rowland, B M; Judge, T K; Rothman, S W

    1988-01-01

    To help explain a role of the Shiga toxin family in hemorrhagic colitis and hemolytic-uremic syndrome in humans, it has been hypothesized that these toxins cause direct damage to the vascular endothelium. We now report that Shiga toxin purified from Shigella dysenteriae 1 does indeed have a direct cytotoxic effect on vascular endothelial cells in cultures. Human umbilical vein endothelial cells (HUVEC) in confluent monolayers were reduced 50% by 10(-8) M Shiga toxin after a lag period of 48 to 96 h. In comparison, nonconfluent HUVEC were reduced 50% by 10(-10) M Shiga toxin within a 24-h period. These data suggest that dividing endothelial cells are more sensitive to Shiga toxin than are quiescent cells in confluent monolayers. Both confluent and nonconfluent HUVEC specifically bound 125I-Shiga toxin. However, in response to the toxin, rates of incorporation of [3H]leucine into protein were more severely reduced in nonconfluent cells than in confluent cells. Toxin inhibition of protein synthesis preceded detachment of cells from the substratum. The specific binding of 125I-Shiga toxin to human endothelial cells and the cytotoxic response were both toxin dose dependent and neutralized by anti-Shiga toxin antibody. Heat-denatured Shiga toxin was without the cytotoxic effect. In addition, the complete culture system contained less than 0.1 ng of bacterial endotoxin per ml, as measured by the Limulus amoebocyte lysate test. PMID:3044997

  14. The ζ Toxin Induces a Set of Protective Responses and Dormancy

    PubMed Central

    Tabone, Mariangela; Gonzalez-Pastor, José E.; Daugelavicius, Rimantas; Ayora, Silvia; Alonso, Juan C.

    2012-01-01

    The ζε module consists of a labile antitoxin protein, ε, which in dimer form (ε2) interferes with the action of the long-living monomeric ζ phosphotransferase toxin through protein complex formation. Toxin ζ, which inhibits cell wall biosynthesis and may be bactericide in nature, at or near physiological concentrations induces reversible cessation of Bacillus subtilis proliferation (protective dormancy) by targeting essential metabolic functions followed by propidium iodide (PI) staining in a fraction (20–30%) of the population and selects a subpopulation of cells that exhibit non-inheritable tolerance (1–5×10−5). Early after induction ζ toxin alters the expression of ∼78 genes, with the up-regulation of relA among them. RelA contributes to enforce toxin-induced dormancy. At later times, free active ζ decreases synthesis of macromolecules and releases intracellular K+. We propose that ζ toxin induces reversible protective dormancy and permeation to PI, and expression of ε2 antitoxin reverses these effects. At later times, toxin expression is followed by death of a small fraction (∼10%) of PI stained cells that exited earlier or did not enter into the dormant state. Recovery from stress leads to de novo synthesis of ε2 antitoxin, which blocks ATP binding by ζ toxin, thereby inhibiting its phosphotransferase activity. PMID:22295078

  15. Staphylococcus aureus toxins.

    PubMed

    Otto, Michael

    2014-02-01

    Staphylococcus aureus is a dangerous pathogen that causes a variety of severe diseases. The virulence of S. aureus is defined by a large repertoire of virulence factors, among which secreted toxins play a preeminent role. Many S. aureus toxins damage biological membranes, leading to cell death. In particular, S. aureus produces potent hemolysins and leukotoxins. Among the latter, some were recently identified to lyse neutrophils after ingestion, representing an especially powerful weapon against bacterial elimination by innate host defense. Furthermore, S. aureus secretes many factors that inhibit the complement cascade or prevent recognition by host defenses. Several further toxins add to this multi-faceted program of S. aureus to evade elimination in the host. This review will give an overview over S. aureus toxins focusing on recent advances in our understanding of how leukotoxins work in receptor-mediated or receptor-independent fashions.

  16. [Natural toxin poisoning].

    PubMed

    Tsunematsu, Satoshi

    2012-08-01

    Natural toxin poisoning often occurs when amateur who has no expert knowledge of food collects and cooks the wrong material. In many cases, the symptoms of natural toxin poisoning are mild and the patients recover from illness within a day. However, if the patients have respiratory or neurological symptoms after several hours of intake, the patients must go to hospital immediately. Mushroom poisoning is often reported and puffer fish poisoning is sometimes reported in Japan.

  17. Reactivation of fear memory renders consolidated amygdala synapses labile.

    PubMed

    Kim, Jeongyeon; Song, Beomjong; Hong, Ingie; Kim, Jihye; Lee, Junuk; Park, Sungmo; Eom, Jae Yong; Lee, C Justin; Lee, Sukwon; Choi, Sukwoo

    2010-07-14

    It is believed that memory reactivation transiently renders consolidated memory labile and that this labile or deconsolidated memory is reconsolidated in a protein synthesis-dependent manner. The synaptic correlate of memory deconsolidation upon reactivation, however, has not been fully characterized. Here, we show that 3,5-dihydroxyphenylglycine (DHPG), an agonist for group I metabotropic glutamate receptors (mGluRI), induces synaptic depotentiation only at thalamic input synapses onto the lateral amygdala (T-LA synapses) where synaptic potentiation is consolidated, but not at synapses where synaptic potentiation is not consolidated. Using this mGluRI-induced synaptic depotentiation (mGluRI-depotentiation) as a marker of consolidated synapses, we found that mGluRI-depotentiation correlated well with the state of memory deconsolidation and reconsolidation in a predictable manner. DHPG failed to induce mGluRI-depotentiation in slices prepared immediately after reactivation when the reactivated memory was deconsolidated. DHPG induced mGluRI-depotentiation 1 h after reactivation when the reactivated memory was reconsolidated, but it failed to do so when reconsolidation was blocked by a protein synthesis inhibitor. To test the memory-specificity of mGluRI-depotentiation, conditioned fear was acquired twice using two discriminative tones (2.8 and 20 kHz). Under this condition, mGluRI-depotentiation was fully impaired in slices prepared immediately after reactivation with both tones, whereas mGluRI-depotentiation was partially impaired immediately after reactivation with the 20 kHz tone. Consistently, microinjection of DHPG into the LA 1 h after reactivation reduced fear memory retention, whereas DHPG injection immediately after reactivation failed to do so. Our findings suggest that, upon memory reactivation, consolidated T-LA synapses enter a temporary labile state, displaying insensitivity to mGluRI-depotentiation.

  18. Do Vermont's Floodplains Constitute an Important Source of Labile Carbon?

    NASA Astrophysics Data System (ADS)

    Perdrial, J. N.; Dolan, A.; Kemsley, M.

    2014-12-01

    Floodplains are extremely heterogeneous landscapes with respect to soil and sediment composition and can present an important source of carbon (C) during floods. For example, stream bank soils and sediments are zones of active erosion and deposition of sediment associated C. Due to the presence of plants, riparian soils contain high amounts of C that is exchanged between stream waters and banks. Abandoned channels and meander wetlands that remain hydrologically connected to the main channel contain high amounts of organic matter that can be flushed into the stream during high discharge. This heterogeneity, result of floodplain geomorphology, land cover and use, can profoundly impact the amount and type of dissolved organic matter (DOM) introduced into streams. In order to assess DOM characteristics leached from heterogeneous floodplain soils, aqueous soil extracts were performed on soil samples representative of different land covers (n=20) at four depths. Extracts were analyzed for dissolved organic C and total dissolved nitrogen with a Shimadzu C analyzer. Colored dissolved organic matter characteristics was measured with the Aqualog Fluorescence Spectrometer and quantified with parallel factor analysis (PARAFAC). Preliminary data from three floodplains in Vermont (Connecticut, Missisquoi and Mad River) show a 3D variability of longitudinal, lateral, and vertical extents on water-extractable, mobile C. Dissolved organic carbon concentrations in meander swamp samples were found up to 9 times higher than in those of soils from agricultural field indicative of an important C source. Although C concentrations in adjacent fields were low, high abundance of labile C (indicated by tryptophan-like fluorescence) in water extracts from fields indicates recent biological production of C. This labile C is easily processed by microbes and transformed to the greenhouse gas CO2. These results provide important information on the contribution and lability of different floodplain

  19. Photo-lability of deep ocean dissolved black carbon

    NASA Astrophysics Data System (ADS)

    Stubbins, A.; Niggemann, J.; Dittmar, T.

    2012-05-01

    Dissolved black carbon (DBC), defined here as condensed aromatics isolated from seawater via PPL solid phase extraction and quantified as benzenepolycarboxylic acid (BPCA) oxidation products, is a significant component of the oceanic dissolved organic carbon (DOC) pool. These condensed aromatics are widely distributed in the open ocean and appear to be tens of thousands of years old. As such DBC is regarded as highly refractory. In the current study, the photo-lability of DBC, DOC and coloured dissolved organic matter (CDOM; ultraviolet-visible absorbance) were determined over the course of a 28 day irradiation of North Atlantic Deep Water under a solar simulator. During the irradiation DBC fell from 1044 ± 164 nM-C to 55 ± 15 nM-C, a 20-fold decrease in concentration. Dissolved black carbon photo-degradation was more rapid and more extensive than for bulk CDOM and DOC. The concentration of DBC correlated with CDOM absorbance and the quality of DBC indicated by the ratios of different BPCAs correlated with CDOM absorbance spectral slope, suggesting the optical properties of CDOM may provide a proxy for both DBC concentrations and quality in natural waters. Further, the photo-lability of components of the DBC pool increased with their degree of aromatic condensation. These trends indicate that a continuum of compounds of varying photo-lability exists within the marine DOC pool. In this continuum, photo-lability scales with aromatic character, specifically the degree of condensation. Scaling the rapid photo-degradation of DBC to rates of DOC photo-mineralisation for the global ocean leads to an estimated photo-chemical half-life for oceanic DBC of less than 800 years. This is more than an order of magnitude shorter than the apparent age of DBC in the ocean. Consequently, photo-degradation is posited as the primary sink for oceanic DBC and the apparent survival of DBC molecules in the oceans for millennia appears to be facilitated not by their inherent inertness but

  20. Alkali lability of bacteriophage phi W-14 DNA.

    PubMed

    Lewis, H A; Miller, R C; Stone, J C; Warren, R A

    1975-12-01

    The molecular weight of bacteriophage phi W-14 DNA, determined by velocity sedimentation in neutral sucrose gradients, was 92 +/- 6 X 10(6). The DNA showed marked fragmentation in alkaline sucrose gradients. This fragmentation was not a consequence of preexisting single-strand interruptions in the DNA, since thermal denaturation of DNA yielded intact single strands. The alpha-putrescinylthymine groups in phi W-14 DNA appeared to be labile; some, or parts of some, of these groups were cleaved from the DNA in alkali. PMID:1202241

  1. [Toxins of Clostridium perfringens as a natural and bioterroristic threats].

    PubMed

    Omernik, Andrzej; Płusa, Tadeusz

    2015-09-01

    Clostridium perfringens is absolutely anaerobic rod-shaped, sporeforming bacterium. The morbidity is connected with producing toxins. Depending on the type of toxin produced Clostridium perfringens can be divided into five serotypes:A-E. Under natural conditions, this bacterium is responsible for local outbreaks of food poisoning associated with eating contaminated food which which was improperly heat treated. Some countries with lower economic level are endemic foci of necrotizing enteritis caused by Clostridium perfringens. The bacterium is also a major cause of gas gangrene. It is a disease, associated with wound infection, with potentially fatal prognosis in the case of treatment's delays. In the absence of early radical surgery, antibiotic therapy and (if available) hyperbaric treatment leads to the spread of toxins in the body causing shock, coma and death. Due to the force of produced toxins is a pathogen that poses a substrate for the production of biological weapons. It could potentially be used to induce outbreaks of food poisoning and by missiles contamination by spore lead to increased morbidity of gas gangrene in injured soldiers. C. perfringens types B and D produce epsilon toxin considered to be the third most powerful bacterial toxin. Because of the ability to disperse the toxin as an aerosol and a lack of methods of treatment and prevention of poisoning possible factors it is a potential tool for bioterrorism It is advisable to continue research into vaccines and treatments for poisoning toxins of C. perfringens. PMID:26449576

  2. [Toxins of Clostridium perfringens as a natural and bioterroristic threats].

    PubMed

    Omernik, Andrzej; Płusa, Tadeusz

    2015-09-01

    Clostridium perfringens is absolutely anaerobic rod-shaped, sporeforming bacterium. The morbidity is connected with producing toxins. Depending on the type of toxin produced Clostridium perfringens can be divided into five serotypes:A-E. Under natural conditions, this bacterium is responsible for local outbreaks of food poisoning associated with eating contaminated food which which was improperly heat treated. Some countries with lower economic level are endemic foci of necrotizing enteritis caused by Clostridium perfringens. The bacterium is also a major cause of gas gangrene. It is a disease, associated with wound infection, with potentially fatal prognosis in the case of treatment's delays. In the absence of early radical surgery, antibiotic therapy and (if available) hyperbaric treatment leads to the spread of toxins in the body causing shock, coma and death. Due to the force of produced toxins is a pathogen that poses a substrate for the production of biological weapons. It could potentially be used to induce outbreaks of food poisoning and by missiles contamination by spore lead to increased morbidity of gas gangrene in injured soldiers. C. perfringens types B and D produce epsilon toxin considered to be the third most powerful bacterial toxin. Because of the ability to disperse the toxin as an aerosol and a lack of methods of treatment and prevention of poisoning possible factors it is a potential tool for bioterrorism It is advisable to continue research into vaccines and treatments for poisoning toxins of C. perfringens.

  3. Targeted silencing of anthrax toxin receptors protects against anthrax toxins.

    PubMed

    Arévalo, Maria T; Navarro, Ashley; Arico, Chenoa D; Li, Junwei; Alkhatib, Omar; Chen, Shan; Diaz-Arévalo, Diana; Zeng, Mingtao

    2014-05-30

    Anthrax spores can be aerosolized and dispersed as a bioweapon. Current postexposure treatments are inadequate at later stages of infection, when high levels of anthrax toxins are present. Anthrax toxins enter cells via two identified anthrax toxin receptors: tumor endothelial marker 8 (TEM8) and capillary morphogenesis protein 2 (CMG2). We hypothesized that host cells would be protected from anthrax toxins if anthrax toxin receptor expression was effectively silenced using RNA interference (RNAi) technology. Thus, anthrax toxin receptors in mouse and human macrophages were silenced using targeted siRNAs or blocked with specific antibody prior to challenge with anthrax lethal toxin. Viability assays were used to assess protection in macrophages treated with specific siRNA or antibody as compared with untreated cells. Silencing CMG2 using targeted siRNAs provided almost complete protection against anthrax lethal toxin-induced cytotoxicity and death in murine and human macrophages. The same results were obtained by prebinding cells with specific antibody prior to treatment with anthrax lethal toxin. In addition, TEM8-targeted siRNAs also offered significant protection against lethal toxin in human macrophage-like cells. Furthermore, silencing CMG2, TEM8, or both receptors in combination was also protective against MEK2 cleavage by lethal toxin or adenylyl cyclase activity by edema toxin in human kidney cells. Thus, anthrax toxin receptor-targeted RNAi has the potential to be developed as a life-saving, postexposure therapy against anthrax.

  4. An ultrahigh-resolution mass spectrometry index to estimate natural organic matter lability

    PubMed Central

    D'Andrilli, Juliana; Cooper, William T; Foreman, Christine M; Marshall, Alan G

    2015-01-01

    Rationale Determining the chemical constituents of natural organic matter (NOM) by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FTICRMS) remains the ultimate measure for probing its source material, evolution, and transport; however, lability and the fate of organic matter (OM) in the environment remain controversial. FTICRMS-derived elemental compositions are presented in this study to validate a new interpretative method to determine the extent of NOM lability from various environments. Methods FTICRMS data collected over the last decade from the same 9.4 tesla instrument using negative electrospray ionization at the National High Magnetic Field Laboratory in Tallahassee, Florida, was used to validate the application of a NOM lability index. Solid-phase extraction cartridges were used to isolate the NOM prior to FTICRMS; mass spectral peaks were calibrated internally by commonly identified NOM homologous series, and molecular formulae were determined for NOM composition and lability analysis. Results A molecular lability boundary (MLB) was developed from the FTICRMS molecular data, visualized from van Krevelen diagrams, dividing the data into more and less labile constituents. NOM constituents above the MLB at H/C ≥1.5 correspond to more labile material, whereas NOM constituents below the MLB, H/C <1.5, exhibit less labile, more recalcitrant character. Of all marine, freshwater, and glacial environments considered for this study, glacial ecosystems were calculated to contain the most labile OM. Conclusions The MLB extends our interpretation of FTICRMS NOM molecular data to include a metric of lability, and generally ranked the OM environments from most to least labile as glacial > marine > freshwater. Applying the MLB is useful not only for individual NOM FTICRMS studies, but also provides a lability threshold to compare and contrast molecular data with other FTICRMS instruments that survey NOM from around the world. Copyright © 2015

  5. Naturally Occurring Food Toxins

    PubMed Central

    Dolan, Laurie C.; Matulka, Ray A.; Burdock, George A.

    2010-01-01

    Although many foods contain toxins as a naturally-occurring constituent or, are formed as the result of handling or processing, the incidence of adverse reactions to food is relatively low. The low incidence of adverse effects is the result of some pragmatic solutions by the US Food and Drug Administration (FDA) and other regulatory agencies through the creative use of specifications, action levels, tolerances, warning labels and prohibitions. Manufacturers have also played a role by setting limits on certain substances and developing mitigation procedures for process-induced toxins. Regardless of measures taken by regulators and food producers to protect consumers from natural food toxins, consumption of small levels of these materials is unavoidable. Although the risk for toxicity due to consumption of food toxins is fairly low, there is always the possibility of toxicity due to contamination, overconsumption, allergy or an unpredictable idiosyncratic response. The purpose of this review is to provide a toxicological and regulatory overview of some of the toxins present in some commonly consumed foods, and where possible, discuss the steps that have been taken to reduce consumer exposure, many of which are possible because of the unique process of food regulation in the United States. PMID:22069686

  6. Engineering cyclic peptide toxins.

    PubMed

    Clark, Richard J; Craik, David J

    2012-01-01

    Peptide-based toxins have attracted much attention in recent years for their exciting potential applications in drug design and development. This interest has arisen because toxins are highly potent and selectively target a range of physiologically important receptors. However, peptides suffer from a number of disadvantages, including poor in vivo stability and poor bioavailability. A number of naturally occurring cyclic peptides have been discovered in plants, animals, and bacteria that have exceptional stability and potentially ameliorate these disadvantages. The lessons learned from studies of the structures, stabilities, and biological activities of these cyclic peptides can be applied to the reengineering of toxins that are not naturally cyclic but are amenable to cyclization. In this chapter, we describe solid-phase chemical synthetic methods for the reengineering of peptide toxins to improve their suitability as therapeutic, diagnostic, or imaging agents. The focus is on small disulfide-rich peptides from the venoms of cone snails and scorpions, but the technology is potentially widely applicable to a number of other peptide-based toxins. PMID:22230565

  7. Marine and freshwater toxins.

    PubMed

    Hungerford, James M

    2006-01-01

    In a very busy and exciting year, 2005 included First Action approval of a much needed official method for paralytic shellfish toxins and multiple international toxin symposia highlighted by groundbreaking research. These are the first-year milestones and activities of the Marine and Freshwater Toxins Task Force and Analytical Community. Inaugurated in 2004 and described in detail in last year's General Referee Report (1) this international toxins group has grown to 150 members from many regions and countries. Perhaps most important they are now making important and global contributions to food safety and to providing alternatives to animal-based assays. Official Method 2005.06 was first approved in late 2004 by the Task Force and subsequently Official First Action in 2005 (2) by the Methods Committee on Natural Toxins and Food Allergens and the Official Methods Board. This nonproprietary method (3) is a precolumn oxidation, liquid chromatographic method that makes good use of fluorescence detection to provide high sensitivity detection of the saxitoxins. It has also proven to be rugged enough for regulatory use and the highest level of validation. As pointed out in the report of method principle investigator and Study Director James Lawrence, approval of 2005.06 now provides the first official alternative to the mouse bioassay after many decades of shellfish monitoring. This past year in April 2005 the group also held their first international conference, "Marine and Freshwater Toxins Analysis: Ist Joint Symposium and AOAC Task Force Meeting," in Baiona, Spain. The 4-day conference consisted of research and stakeholder presentations and symposium-integrated subgroup sessions on ciguatoxins, saxitoxin assays and liquid chromatography (LC) methods for saxitoxins and domoic acids, okadaiates and azaspiracids, and yessotoxins. Many of these subgroups were recently formed in 2005 and are working towards their goals of producing officially validated analytical methods

  8. Marine Neurotoxins: Ingestible Toxins.

    PubMed

    Stommel, Elijah W.; Watters, Michael R.

    2004-03-01

    Fish and shellfish account for a significant portion of food-borne illnesses throughout the world. In general, three classes of diseases result from seafood consumption--intoxication, allergies, and infections. In this review, the authors discuss several seafood-borne toxins, including domoic acid, which acts on the central nervous system. In addition, the authors discuss ciguatoxin-, brevetoxin-, saxitoxin-, tetrodotoxin-, and scombroid-related histamine toxicity, all of which act primarily on the peripheral nervous system. Fish has become a very popular food in the US mostly related to its potential health benefits. Fish is consumed to such a degree that fishing stocks are reportedly at an all time low from what seemed like an endless supply even 30 years ago. One of the most significant threats to human intoxication is the recreational harvest of shellfish, often times located in remote locations where the harvesters are subsistent on fishery resources and have no monitoring in place. The hazard to intoxication is not as common in purchased seafood, which is more stringently regulated, yet still is a serious problem. Most ingestible toxins are thermo-stable and therefore unaffected by cooking, freezing, or salting. Air transport of consumable products throughout the world makes it easy to obtain exotic edibles from far away countries. A seemingly unusual toxin can be more commonly encountered than previously thought and it is important to consider this when evaluating patients. Recognition and treatment of various neurologic symptoms related to seafood ingestion is paramount in today's mobile, gastronomic world. Specific treatments vary with each individual toxin and with the individual's specific reaction to the toxin. Generally, some degree of medical care is required with all ingestible toxin exposure, ranging from simple administration of medication and hydration to ventilatory and cardiovascular support.

  9. Biodegradation of the Polyketide Toxin Cercosporin

    PubMed Central

    Mitchell, Thomas K.; Chilton, William Scott; Daub, Margaret E.

    2002-01-01

    Cercosporin is a non-host-specific polyketide toxin produced by many species of plant pathogens belonging to the genus Cercospora. This red-pigmented, light-activated toxin is an important pathogenicity determinant for Cercospora species. In this study, we screened 244 bacterial isolates representing 12 different genera for the ability to degrade cercosporin. Cercosporin degradation was determined by screening for the presence of cleared zones surrounding colonies on cercosporin-containing culture medium and was confirmed by assaying the kinetics of degradation in liquid medium. Bacteria belonging to four different genera exhibited the cercosporin-degrading phenotype. The isolates with the greatest cercosporin-degrading activity belonged to Xanthomonas campestris pv. zinniae and X. campestris pv. pruni. Isolates of these pathovars removed over 90% of the cercosporin from culture medium within 48 h. Bacterial degradation of red cercosporin was accompanied by a shift in the color of the growth medium to brown and then green. The disappearance of cercosporin was accompanied by the appearance of a transient green product, designated xanosporic acid. Xanosporic acid and its more stable lactone derivative, xanosporolactone, are nontoxic to cercosporin-sensitive fungi and to plant tissue and are labile in the presence of light. Detailed spectroscopic analysis (to be reported in a separate publication) of xanosporolactone revealed that cercosporin loses one methoxyl group and gains one oxygen atom in the bacterial conversion. The resulting chromophore (4,9-dihydroxy-3-oxaperlylen-10H-10-one) has never been reported before but is biosynthetically plausible via oxygen insertion by a cytochrome P-450 enzyme. PMID:12200262

  10. [Toxins as a biological weapon].

    PubMed

    Płusa, Tadeusz

    2015-09-01

    The criteria for recognizing a chemical compound for the toxin are vague and gave it the possibility of inclusion in this group a number of biological agents. Toxins list is extensive, but the interest is focused on bacterial toxins, poisons derived from snake venoms, algae and plant proteins, and small molecules. Particular attention is focused on the so-called "sea" toxins, which include tetrodotoxin, brevetoxin and saxitoxin. This indicates the search for a new hitherto unknown potential bioterrorist threats.

  11. [Toxins as a biological weapon].

    PubMed

    Płusa, Tadeusz

    2015-09-01

    The criteria for recognizing a chemical compound for the toxin are vague and gave it the possibility of inclusion in this group a number of biological agents. Toxins list is extensive, but the interest is focused on bacterial toxins, poisons derived from snake venoms, algae and plant proteins, and small molecules. Particular attention is focused on the so-called "sea" toxins, which include tetrodotoxin, brevetoxin and saxitoxin. This indicates the search for a new hitherto unknown potential bioterrorist threats. PMID:26449572

  12. Dog paw preference shows lability and sex differences.

    PubMed

    Poyser, Fay; Caldwell, Christine; Cobb, Matthew

    2006-09-01

    Paw preferences in domestic dogs were studied using three different behavioural tests, recording frequency, duration and latency of paw use. No overall population tendency to right- or left-paw preference was seen on any of the tests, nor could a sub-population of handed dogs be detected. This failure to replicate previous reports that male dogs tend to use their left paws while females use their right was counterbalanced by a significant tendency for male dogs to use their left paw when initially presented with one test, and for the latency of left paw use to be significantly shorter than that for right paw use on these initial presentations. This significant effect disappeared with repeated presentation of the test, and was not present in females. We conclude that behavioural lateralisation appears to be a labile category in dogs, and may be related to brain hemispheric effects in responding to novel stimuli.

  13. The role of labile sulfur compounds in thermochemical sulfate reduction

    NASA Astrophysics Data System (ADS)

    Amrani, Alon; Zhang, Tongwei; Ma, Qisheng; Ellis, Geoffrey S.; Tang, Yongchun

    2008-06-01

    The reduction of sulfate to sulfide coupled with the oxidation of hydrocarbons to carbon dioxide, commonly referred to as thermochemical sulfate reduction (TSR), is an important abiotic alteration process that most commonly occurs in hot carbonate petroleum reservoirs. In the present study we focus on the role that organic labile sulfur compounds play in increasing the rate of TSR. A series of gold-tube hydrous pyrolysis experiments were conducted with n-octane and CaSO4 in the presence of reduced sulfur (e.g. H2S, S°, organic S) at temperatures of 330 and 356 °C under a constant confining pressure. The in-situ pH was buffered to 3.5 (∼6.3 at room temperature) with talc and silica. For comparison, three types of oil with different total S and labile S contents were reacted under similar conditions. The results show that the initial presence of organic or inorganic sulfur compounds increases the rate of TSR. However, organic sulfur compounds, such as 1-pentanethiol or diethyldisulfide, were significantly more effective in increasing the rate of TSR than H2S or elemental sulfur (on a mole S basis). The increase in rate is achieved at relatively low concentrations of 1-pentanethiol, less than 1 wt% of the total n-octane, which is comparable to the concentration of organic S that is common in many oils (∼0.3 wt%). We examined several potential reaction mechanisms to explain the observed reactivity of organic LSC. First, the release of H2S from the thermal degradation of thiols was discounted as an important mechanism due to the significantly greater reactivity of thiol compared to an equivalent amount of H2S. Second, we considered the generation of olefines in association with the elimination of H2S during thermal degradation of thiols because olefines are much more reactive than n-alkanes during TSR. In our experiments, olefines increased the rate of TSR, but were less effective than 1-pentanethiol and other organic LSC. Third, the thermal decomposition of

  14. The role of labile sulfur compounds in thermochemical sulfate reduction

    USGS Publications Warehouse

    Amrani, A.; Zhang, T.; Ma, Q.; Ellis, G.S.; Tang, Y.

    2008-01-01

    The reduction of sulfate to sulfide coupled with the oxidation of hydrocarbons to carbon dioxide, commonly referred to as thermochemical sulfate reduction (TSR), is an important abiotic alteration process that most commonly occurs in hot carbonate petroleum reservoirs. In the present study we focus on the role that organic labile sulfur compounds play in increasing the rate of TSR. A series of gold-tube hydrous pyrolysis experiments were conducted with n-octane and CaSO4 in the presence of reduced sulfur (e.g. H2S, S??, organic S) at temperatures of 330 and 356 ??C under a constant confining pressure. The in-situ pH was buffered to 3.5 (???6.3 at room temperature) with talc and silica. For comparison, three types of oil with different total S and labile S contents were reacted under similar conditions. The results show that the initial presence of organic or inorganic sulfur compounds increases the rate of TSR. However, organic sulfur compounds, such as 1-pentanethiol or diethyldisulfide, were significantly more effective in increasing the rate of TSR than H2S or elemental sulfur (on a mole S basis). The increase in rate is achieved at relatively low concentrations of 1-pentanethiol, less than 1 wt% of the total n-octane, which is comparable to the concentration of organic S that is common in many oils (???0.3 wt%). We examined several potential reaction mechanisms to explain the observed reactivity of organic LSC. First, the release of H2S from the thermal degradation of thiols was discounted as an important mechanism due to the significantly greater reactivity of thiol compared to an equivalent amount of H2S. Second, we considered the generation of olefines in association with the elimination of H2S during thermal degradation of thiols because olefines are much more reactive than n-alkanes during TSR. In our experiments, olefines increased the rate of TSR, but were less effective than 1-pentanethiol and other organic LSC. Third, the thermal decomposition of

  15. Lability of renal papillary tissue composition in the rat.

    PubMed Central

    Atherton, J C

    1978-01-01

    1. The acute effects of (a) a minor operative procedure using ether as the anaesthetic, and (b) the administration of 0.9% saline as a single I.V. injection in the conscious rat, on renal tissue composition were studied in hydropenic and normally hydrated rats. 2. The operative procedure and anaesthesia induced a rapid and transient decrease in papillary osmolality in both hydropenic and normally hydrated animals, the important contributing factor being a significant decrease in urea content. 3. Administration of a small volume of saline caused a rapid decrease in urea content, and an increase in water content. 4. It is concluded that papillary composition is extremely labile, large changes being produced by relatively minor experimental procedures. PMID:624997

  16. Chemical leaching methods and measurements of marine labile particulate Fe

    NASA Astrophysics Data System (ADS)

    Revels, B. N.; John, S.

    2012-12-01

    Iron (Fe) is an essential nutrient for life. Yet its low solubility and concentration in the ocean limits marine phytoplankton productivity in many regions of the world. Dissolved phase Fe (<0.4μm) has traditionally been considered the most biologically accessible form, however, the particulate phase (>0.4μm) may contain an important, labile reservoir of Fe that may also be available to phytoplankton. However, concentration data alone cannot elucidate the sources of particulate Fe to the ocean and to what extent particulate iron may support phytoplankton growth. Isotopic analysis of natural particles may help to elucidate the biogeochemical cycling of Fe, though it is important to find a leaching method which accesses bioavailable Fe. Thirty-three different chemical leaches were performed on a marine sediment reference material, MESS-3. The combinations included four different acids (25% acetic acid, 0.01M HCl, 0.5M HCl, 0.1M H2SO4 at pH2), various redox conditions (0.02M hydroxylamine hydrochloride or 0.02M H2O2), three temperatures (25°C, 60°C, 90°C), and three time points (10 minutes, 2 hours, 24 hours). Leached Fe concentrations varied from 1mg/g to 35mg/g, with longer treatment times, stronger acids, and hotter temperatures generally associated with an increase in leached Fe. δ56Fe in these leaches varied from -1.0‰ to +0.2‰. Interestingly, regardless of leaching method used, there was a very similar relationship between the amount of Fe leached from the particles and the δ56Fe of this iron. Isotopically lighter δ56Fe values were associated with smaller amounts of leached Fe whereas isotopically heavier δ56Fe values were associated with larger amounts of leached Fe. Two alternate hypotheses could explain these data. Either, the particles may contain pools of isotopically light Fe that are easily accessed early in dissolution, or isotopically light Fe may be preferentially leached from the particle due to a kinetic isotope effect during dissolution

  17. Toxin plasmids of Clostridium perfringens.

    PubMed

    Li, Jihong; Adams, Vicki; Bannam, Trudi L; Miyamoto, Kazuaki; Garcia, Jorge P; Uzal, Francisco A; Rood, Julian I; McClane, Bruce A

    2013-06-01

    In both humans and animals, Clostridium perfringens is an important cause of histotoxic infections and diseases originating in the intestines, such as enteritis and enterotoxemia. The virulence of this Gram-positive, anaerobic bacterium is heavily dependent upon its prolific toxin-producing ability. Many of the ∼16 toxins produced by C. perfringens are encoded by large plasmids that range in size from ∼45 kb to ∼140 kb. These plasmid-encoded toxins are often closely associated with mobile elements. A C. perfringens strain can carry up to three different toxin plasmids, with a single plasmid carrying up to three distinct toxin genes. Molecular Koch's postulate analyses have established the importance of several plasmid-encoded toxins when C. perfringens disease strains cause enteritis or enterotoxemias. Many toxin plasmids are closely related, suggesting a common evolutionary origin. In particular, most toxin plasmids and some antibiotic resistance plasmids of C. perfringens share an ∼35-kb region containing a Tn916-related conjugation locus named tcp (transfer of clostridial plasmids). This tcp locus can mediate highly efficient conjugative transfer of these toxin or resistance plasmids. For example, conjugative transfer of a toxin plasmid from an infecting strain to C. perfringens normal intestinal flora strains may help to amplify and prolong an infection. Therefore, the presence of toxin genes on conjugative plasmids, particularly in association with insertion sequences that may mobilize these toxin genes, likely provides C. perfringens with considerable virulence plasticity and adaptability when it causes diseases originating in the gastrointestinal tract.

  18. CYANOBACTERIA AND THEIR TOXINS.

    EPA Science Inventory

    Science Questions

    Harmful algal blooms (HAB) of cyanobacteria, also known as blue-green algae, have recently become more spatially and temporally prevalent in the US and worldwide. Cyanobacteria and their highly potent toxins are a significant hazard for human health and ...

  19. CYANOBACTERIA AND THEIR TOXINS

    EPA Science Inventory

    Science Questions

    Harmful algal blooms (HAB) of cyanobacteria, also known as blue-green algae, have recently become more spatially and temporally prevalent in the US and worldwide. Cyanobacteria and their highly potent toxins are a significant hazard for human health and ...

  20. [Protein toxins of Staphylococcus aureus].

    PubMed

    Shamsutdinov, A F; Tiurin, Iu A

    2014-01-01

    Main scientific-research studies regarding protein bacterial toxins of the most widespread bacteria that belong to Staphylococcus spp. genus and in particular the most pathogenic species for humans--Staphylococcus aureus, are analyzed. Structural and biological properties of protein toxins that have received the name of staphylococcus pyrogenic toxins (PTSAg) are presented. Data regarding genetic regulation of secretion and synthesis of these toxins and 3 main regulatory genetic systems (agr--accessory gene regulator, xpr--extracellular protein regulator, sar--staphylococcal accessory regulator) that coordinate synthesis of the most important protein toxins and enzymes for virulence of S. aureus, are presented.

  1. NH3-promoted ligand lability in eleven-vertex rhodathiaboranes.

    PubMed

    Calvo, Beatriz; Roy, Beatriz; Macías, Ramón; Artigas, Maria Jose; Lahoz, Fernando J; Oro, Luis A

    2014-12-01

    The reaction of the 11-vertex rhodathiaborane, [8,8-(PPh3)2-nido-8,7-RhSB9H10] (1), with NH3 affords inmediately the adduct, [8,8,8-(NH3)(PPh3)2-nido-8,7-RhSB9H10] (4). The NH3-Rh interaction induces the labilization of the PPh3 ligands leading to the dissociation product, [8,8-(NH3)(PPh3)-nido-8,7-RhSB9H10] (5), which can then react with another molecule of NH3 to give [8,8,8-(NH3)2(PPh3)-nido-8,7-RhSB9H10] (6). These clusters have been characterized in situ by multielement NMR spectroscopy at different temeperatures. The variable temperature behavior of the system demonstrates that the intermediates 4-6 are in equilibrium, involving ligand exchange processes. On the basis of low intensity signals present in the (1)H NMR spectra of the reaction mixture, some species are tentatively proposed to be the bis- and tris-NH3 ligated clusters, [8,8-(NH3)2-nido-8,7-RhSB9H10] (7) and [8,8,8-(NH3)3-nido-8,7-RhSB9H10] (8). After evaporation of the solvent and the excess of NH3, the system containing species 4-8 regenerates the starting reactant, 1, thus closing a stoichiometric cycle of ammonia addition and loss. After 40 h at room temperature, the reaction of 1 with NH3 gives the hydridorhodathiaborane, [8,8,8-(H)(PPh3)2-nido-8,7-RhSB9H9] (2), as a single product. The reported rhodathiaboranes show reversible H3N-promoted ligand lability, which implies weak Rh-N interactions, leading to a rare case of metal complexes that circumvent "classical" Werner chemistry.

  2. Toxins and drug discovery.

    PubMed

    Harvey, Alan L

    2014-12-15

    Components from venoms have stimulated many drug discovery projects, with some notable successes. These are briefly reviewed, from captopril to ziconotide. However, there have been many more disappointments on the road from toxin discovery to approval of a new medicine. Drug discovery and development is an inherently risky business, and the main causes of failure during development programmes are outlined in order to highlight steps that might be taken to increase the chances of success with toxin-based drug discovery. These include having a clear focus on unmet therapeutic needs, concentrating on targets that are well-validated in terms of their relevance to the disease in question, making use of phenotypic screening rather than molecular-based assays, and working with development partners with the resources required for the long and expensive development process.

  3. Evolutionarily labile responses to a signal of aggressive intent.

    PubMed Central

    Moretz, Jason A; Morris, Molly R

    2003-01-01

    Males of many swordtail species possess vertical bar pigment patterns that are used both in courtship and agonistic interactions. Expression of the bars may function as a conventional threat signal during conflicts with rival males; bars intensify at the onset of aggression and fade in the subordinate male at contest's end. We used mirror image stimulation and bar manipulations to compare the aggressive responses of the males of four swordtail species to their barred and barless images. We found that having a response to the bars is tightly linked to having genes for bars, while the nature of the response the bars evoked varied across species. Specifically, we report the first known instance where closely related species exhibited differing and contradictory responses to a signal of aggressive motivation. Demonstrating that a signal conveys the same information across species (aggressive intent) while the response to that information has changed among species suggests that the nature of the responses are more evolutionarily labile than the signal. PMID:14613614

  4. Comparison of Outcomes in Patients With Nonobstructive, Labile-Obstructive, and Chronically Obstructive Hypertrophic Cardiomyopathy.

    PubMed

    Pozios, Iraklis; Corona-Villalobos, Celia; Sorensen, Lars L; Bravo, Paco E; Canepa, Marco; Pisanello, Chiara; Pinheiro, Aurelio; Dimaano, Veronica L; Luo, Hongchang; Dardari, Zeina; Zhou, Xun; Kamel, Ihab; Zimmerman, Stefan L; Bluemke, David A; Abraham, M Roselle; Abraham, Theodore P

    2015-09-15

    Patients with nonobstructive hypertrophic cardiomyopathy (HC) are considered low risk, generally not requiring aggressive intervention. However, nonobstructive and labile-obstructive HC have been traditionally classified together, and it is unknown if these 2 subgroups have distinct risk profiles. We compared cardiovascular outcomes in 293 patients HC (96 nonobstructive, 114 labile-obstructive, and 83 obstructive) referred for exercise echocardiography and magnetic resonance imaging and followed for 3.3 ± 3.6 years. A subgroup (34 nonobstructive, 28 labile-obstructive, 21 obstructive) underwent positron emission tomography. The mean number of sudden cardiac death risk factors was similar among groups (nonobstructive: 1.4 vs labile-obstructive: 1.2 vs obstructive: 1.4 risk factors, p = 0.2). Prevalence of late gadolinium enhancement (LGE) was similar across groups but more non-obstructive patients had late gadolinium enhancement ≥20% of myocardial mass (23 [30%] vs 19 [18%] labile-obstructive and 8 [11%] obstructive, p = 0.01]. Fewer labile-obstructive patients had regional positron emission tomography perfusion abnormalities (12 [46%] vs nonobstructive 30 [81%] and obstructive 17 [85%], p = 0.003]. During follow-up, 60 events were recorded (36 ventricular tachycardia/ventricular fibrillation, including 30 defibrillator discharges, 12 heart failure worsening, and 2 deaths). Nonobstructive patients were at greater risk of VT/VF at follow-up, compared to labile obstructive (hazed ratio 0.18, 95% confidence interval 0.04 to 0.84, p = 0.03) and the risk persisted after adjusting for age, gender, syncope, family history of sudden cardiac death, abnormal blood pressure response, and septum ≥3 cm (p = 0.04). Appropriate defibrillator discharges were more frequent in nonobstructive (8 [18%]) compared to labile-obstructive (0 [0%], p = 0.02) patients. In conclusion, nonobstructive hemodynamics is associated with more pronounced fibrosis and ischemia than labile

  5. Method for detecting biological toxins

    SciTech Connect

    Ligler, F.S.; Campbell, J.R.

    1992-01-01

    Biological toxins are indirectly detected by using polymerase chain reaction to amplify unique nucleic acid sequences coding for the toxins or enzymes unique to toxin synthesis. Buffer, primers coding for the unique nucleic acid sequences and an amplifying enzyme are added to a sample suspected of containing the toxin. The mixture is then cycled thermally to exponentially amplify any of these unique nucleic acid sequences present in the sample. The amplified sequences can be detected by various means, including fluorescence. Detection of the amplified sequences is indicative of the presence of toxin in the original sample. By using more than one set of labeled primers, the method can be used to simultaneously detect several toxins in a sample.

  6. [Today's threat of ricin toxin].

    PubMed

    From, Sławomir; Płusa, Tadeusz

    2015-09-01

    Since the late 70s of the last century there were more than 700 incidents related to the use of the ricin toxin. For this reason, CDC (Center of Disease Control and Prevention) recognized toxin as a biological weapon category B. The lethal dose of ricin toxin after parenteral administration is 0.0001 mg/kg and after oral administration 0.2 mg. The first symptoms of poisoning occur within a few hours after application of toxin as a nausea, vomiting and abdominal pain. In the final stage there are observed: cardiac arrhythmia, collapse and symptoms suggestive of involvement of the central nervous system. Stage immediately preceding death is a state of coma. The ricin toxin is still the substance against which action has no optimal antidote. Developed a vaccine called RiVax is waiting for its registration. It should be pointed out that the availability of a ricin toxin makes it possible to use it for real bioterrorists.

  7. Pore formation by Cry toxins.

    PubMed

    Soberón, Mario; Pardo, Liliana; Muñóz-Garay, Carlos; Sánchez, Jorge; Gómez, Isabel; Porta, Helena; Bravo, Alejandra

    2010-01-01

    Bacillus thuringiensis (Bt) bacteria produce insecticidal Cry and Cyt proteins used in the biological control of different insect pests. In this review, we will focus on the 3d-Cry toxins that represent the biggest group of Cry proteins and also on Cyt toxins. The 3d-Cry toxins are pore-forming toxins that induce cell death by forming ionic pores into the membrane of the midgut epithelial cells in their target insect. The initial steps in the mode of action include ingestion of the protoxin, activation by midgut proteases to produce the toxin fragment and the interaction with the primary cadherin receptor. The interaction of the monomeric CrylA toxin with the cadherin receptor promotes an extra proteolytic cleavage, where helix alpha-1 of domain I is eliminated and the toxin oligomerization is induced, forming a structure of 250 kDa. The oligomeric structure binds to a secondary receptor, aminopeptidase N or alkaline phosphatase. The secondary receptor drives the toxin into detergent resistant membrane microdomains formingpores that cause osmotic shock, burst of the midgut cells and insect death. Regarding to Cyt toxins, these proteins have a synergistic effect on the toxicity of some Cry toxins. Cyt proteins are also proteolytic activated in the midgut lumen of their target, they bind to some phospholipids present in the mosquito midgut cells. The proposed mechanism of synergism between Cry and Cyt toxins is that Cyt1Aa function as a receptor for Cry toxins. The Cyt1A inserts into midgut epithelium membrane and exposes protein regions that are recognized by Cry11Aa. It was demonstrated that this interaction facilitates the oligomerization of Cry11Aa and also its pore formation activity.

  8. Toxin Plasmids of Clostridium perfringens

    PubMed Central

    Li, Jihong; Adams, Vicki; Bannam, Trudi L.; Miyamoto, Kazuaki; Garcia, Jorge P.; Uzal, Francisco A.; Rood, Julian I.

    2013-01-01

    SUMMARY In both humans and animals, Clostridium perfringens is an important cause of histotoxic infections and diseases originating in the intestines, such as enteritis and enterotoxemia. The virulence of this Gram-positive, anaerobic bacterium is heavily dependent upon its prolific toxin-producing ability. Many of the ∼16 toxins produced by C. perfringens are encoded by large plasmids that range in size from ∼45 kb to ∼140 kb. These plasmid-encoded toxins are often closely associated with mobile elements. A C. perfringens strain can carry up to three different toxin plasmids, with a single plasmid carrying up to three distinct toxin genes. Molecular Koch's postulate analyses have established the importance of several plasmid-encoded toxins when C. perfringens disease strains cause enteritis or enterotoxemias. Many toxin plasmids are closely related, suggesting a common evolutionary origin. In particular, most toxin plasmids and some antibiotic resistance plasmids of C. perfringens share an ∼35-kb region containing a Tn916-related conjugation locus named tcp (transfer of clostridial plasmids). This tcp locus can mediate highly efficient conjugative transfer of these toxin or resistance plasmids. For example, conjugative transfer of a toxin plasmid from an infecting strain to C. perfringens normal intestinal flora strains may help to amplify and prolong an infection. Therefore, the presence of toxin genes on conjugative plasmids, particularly in association with insertion sequences that may mobilize these toxin genes, likely provides C. perfringens with considerable virulence plasticity and adaptability when it causes diseases originating in the gastrointestinal tract. PMID:23699255

  9. Thermally-Labile Trace Elements in Enstatite Meteorites

    NASA Technical Reports Server (NTRS)

    Wang, M.-S.; Lipschutz, M. E.

    2000-01-01

    RNAA data for Bi, In and Tl in 30 E3-6 chondrites accord well with trends for heated Abee (EH4) suggesting that all EH and EL samples reflect open-system, post-accretionary heating, independent of siderophile content or recovery location.

  10. Diagnostic multiplex PCR for toxin genotyping of Clostridium perfringens isolates.

    PubMed

    Baums, Christoph G; Schotte, Ulrich; Amtsberg, Gunter; Goethe, Ralph

    2004-05-20

    In this study we provide a protocol for genotyping Clostridium perfringens with a new multiplex PCR. This PCR enables reliable and specific detection of the toxin genes cpa, cpb, etx, iap, cpe and cpb2 from heat lysed bacterial suspensions. The efficiency of the protocol was demonstrated by typing C. perfringens reference strains and isolates from veterinary bacteriological routine diagnostic specimens.

  11. Ratcheting up protein translocation with anthrax toxin

    PubMed Central

    Feld, Geoffrey K; Brown, Michael J; Krantz, Bryan A

    2012-01-01

    Energy-consuming nanomachines catalyze the directed movement of biopolymers in the cell. They are found both dissolved in the aqueous cytosol as well as embedded in lipid bilayers. Inquiries into the molecular mechanism of nanomachine-catalyzed biopolymer transport have revealed that these machines are equipped with molecular parts, including adjustable clamps, levers, and adaptors, which interact favorably with substrate polypeptides. Biological nanomachines that catalyze protein transport, known as translocases, often require that their substrate proteins unfold before translocation. An unstructured protein chain is likely entropically challenging to bind, push, or pull in a directional manner, especially in a way that produces an unfolding force. A number of ingenious solutions to this problem are now evident in the anthrax toxin system, a model used to study protein translocation. Here we highlight molecular ratchets and current research on anthrax toxin translocation. A picture is emerging of proton-gradient-driven anthrax toxin translocation, and its associated ratchet mechanism likely applies broadly to other systems. We suggest a cyclical thermodynamic order-to-disorder mechanism (akin to a heat-engine cycle) is central to underlying protein translocation: peptide substrates nonspecifically bind to molecular clamps, which possess adjustable affinities; polypeptide substrates compress into helical structures; these clamps undergo proton-gated switching; and the substrate subsequently expands regaining its unfolded state conformational entropy upon translocation. PMID:22374876

  12. DETERMINATION OF APPARENT QUANTUM YIELD SPECTRA FOR THE FORMATION OF BIOLOGICALLY LABILE PHOTOPRODUCTS

    EPA Science Inventory

    Quantum yield spectra for the photochemical formation of biologically labile photoproducts from dissolved organic matter (DOM) have not been available previously, although they would greatly facilitate attempts to model photoproduct formation rates across latitudinal, seasonal, a...

  13. The toxins of Cyanobacteria.

    PubMed

    Patocka, J

    2001-01-01

    Cyanobacteria, formerly called "blue-green algae", are simple, primitive photosynthetic microorganism wide occurrence in fresh, brackish and salt waters. Forty different genera of Cyanobacteria are known and many of them are producers of potent toxins responsible for a wide array of human illnesses, aquatic mammal and bird morbidity and mortality, and extensive fish kills. These cyanotoxins act as neurotoxins or hepatotoxins and are structurally and functionally diverse, and many are derived from unique biosynthetic pathways. All known cyanotoxins and their chemical and toxicological characteristics are presented in this article.

  14. Maternal emotion socialization differentially predicts third-grade children's emotion regulation and lability.

    PubMed

    Rogers, Megan L; Halberstadt, Amy G; Castro, Vanessa L; MacCormack, Jennifer K; Garrett-Peters, Patricia

    2016-03-01

    Numerous parental emotion socialization factors have been implicated as direct and indirect contributors to the development of children's emotional competence. To date, however, no study has combined parents' emotion-related beliefs, behaviors, and regulation strategies in one model to assess their cumulative-as well as unique-contributions to children's emotion regulation. We considered the 2 components that have recently been distinguished: emotion regulation and emotional lability. We predicted that mothers' beliefs about the value of and contempt for children's emotions, mothers' supportive and nonsupportive reactions to their children's emotions, as well as mothers' use of cognitive reappraisal and suppression of their own emotions would each contribute unique variance to their children's emotion regulation and lability, as assessed by children's teachers. The study sample consisted of an ethnically and socioeconomically diverse group of 165 mothers and their third-grade children. Different patterns emerged for regulation and lability: Controlling for family income, child gender, and ethnicity, only mothers' lack of suppression as a regulatory strategy predicted greater emotion regulation in children, whereas mothers' valuing of children's emotions, mothers' lack of contempt for children's emotions, mothers' use of cognitive reappraisal to reinterpret events, and mothers' lack of emotional suppression predicted less lability in children. These findings support the divergence of emotion regulation and lability as constructs and indicate that, during middle childhood, children's lability may be substantially and uniquely affected by multiple forms of parental socialization.

  15. Yeast killer plasmid mutations affecting toxin secretion and activity and toxin immunity function

    SciTech Connect

    Bussey, H.; Sacks, W.; Galley, D.; Saville, D.

    1982-04-01

    M double-stranded RNA (MdsRNA) plasmid mutants were obtained by mutagenesis and screening of a diploid killer culture partially heat cured of the plasmid, so that a high proportion of the cells could be expected to have only one M plasmid. Mutants with neutral (K/sup -/), immune (R/sup +/) or suicide (killer (K/sup +/), sensitive (R/sup -/)) phenotypes were examined. All mutants became K/sup -/ R/sup -/ sensitives on heat curing of the MdsRNA plasmid, and showed cytoplasmic inheritance by random spore analysis. In some cases, M plasmid mutations were indicated by altered mobility of the MdsRNA by agarose gel electrophoresis or by altered size of in vitro translation products from denatured dsRNA. Neutral mutants were of two types: nonsecretors of the toxin protein or secretors of an inactive toxin. Of three neutral nonsecretors examined, one (NLP-1), probably a nonsense mutation, made a smaller protoxin precursor in vitro and in vivo, and two made full-size protoxin molecules. The in vivo protoxin of 43,000 molecular weight was unstable in the wild type and kinetically showed a precursor product relationship to the processed, secreted 11,000-molecular-weight toxin. In one nonsecretor (N1), the protoxin appeared more stable in a pulse-chase experiment, and could be altered in a recognition site required for protein processing.

  16. Thermally labile components of aqueous humor potently induce osteogenic potential in adipose-derived mesenchymal stem cells.

    PubMed

    Morgan, Joshua T; Kwon, Heung Sun; Wood, Joshua A; Borjesson, Dori L; Tomarev, Stanislav I; Murphy, Christopher J; Russell, Paul

    2015-06-01

    Adipose-derived mesenchymal stem cells (ASCs) hold promise for use in cell-based therapies. Their intrinsic anti-inflammatory properties are potentially useful for treatments of inflammatory conditions such as uveitis, while their ability to differentiate along multiple cell lineages suggests use in regenerating damaged or degenerated tissue. However, how ASCs will respond to the intraocular environment is poorly studied. We have recently reported that aqueous humor (AH), the fluid that nourishes the anterior segment of the eye, potently increases alkaline phosphatase (ALP) activity of ASCs, indicating osteogenic differentiation. Here, we expand on our previous findings to better define the nature of this response. To this end, we cultured ASCs in the presence of 0, 5, 10, and 20% AH and assayed them for ALP activity. We found ALP activity correlates with increasing AH concentrations from 5 to 20%, and that longer treatments result in increased ALP activity. By using serum free media and pretreating AH with dextran-coated charcoal, we found that serum and charcoal-adsorbable AH components augment but are not required for this response. Further, by heat-treating the AH, we established that thermally labile components are required for the osteogenic response. Finally, we showed myocilin, a protein present in AH, could induce ALP activity in ASCs. However, this was to a lesser extent than untreated 5% AH, and myocilin could only partially rescue the effect after heat treatment, documenting there were additional thermally labile constituents of AH involved in the osteogenic response. Our work adds to the understanding of the induction of ALP in ASCs following exposure to AH, providing important insight in how ASCs will be influenced by the ocular environment. In conclusion, increased osteogenic potential upon exposure to AH represents a potential challenge to developing ASC cell-based therapies directed at the eye.

  17. The assay of diphtheria toxin

    PubMed Central

    Gerwing, Julia; Long, D. A.; Mussett, Marjorie V.

    1957-01-01

    A precise assay of diphtheria toxin is described, based on the linear relationship between the diameter of the skin reaction to, and logarithm of the dose of, toxin. It eliminates the need for preliminary titrations, is economical, provides information about the slope of the log-dose response lines and, therefore, of the validity of the assay, and yields limits of error of potency from the internal evidence of the assay. A study has been made of the effects of avidity, combining power, toxicity and buffering on the assay of diphtheria toxins against the International Standards for both Diphtheria Antitoxin and Schick-Test Toxin. All the toxins assayed against the standard toxin, whatever their other properties might be, gave log-dose response lines of similar slope provided that they were diluted in buffered physiological saline. The assays were therefore valid. These experiments were repeated concurrently in non-immune and in actively immunized guinea-pigs, and comparable figures for potency obtained in both groups. The result was not significantly affected by the avidity or combining power of the toxin. However, non-avid toxins gave low values in Schick units when assayed, by the Römer & Sames technique, in terms of the International Standard for Diphtheria Antitoxin. The problem of the ultimate standard and the implications of these findings are discussed. PMID:13511133

  18. Toxin-Based Therapeutic Approaches

    PubMed Central

    Shapira, Assaf; Benhar, Itai

    2010-01-01

    Protein toxins confer a defense against predation/grazing or a superior pathogenic competence upon the producing organism. Such toxins have been perfected through evolution in poisonous animals/plants and pathogenic bacteria. Over the past five decades, a lot of effort has been invested in studying their mechanism of action, the way they contribute to pathogenicity and in the development of antidotes that neutralize their action. In parallel, many research groups turned to explore the pharmaceutical potential of such toxins when they are used to efficiently impair essential cellular processes and/or damage the integrity of their target cells. The following review summarizes major advances in the field of toxin based therapeutics and offers a comprehensive description of the mode of action of each applied toxin. PMID:22069564

  19. The three-dimensional crystal structure of cholera toxin

    SciTech Connect

    Zhang, Rong-Guang; Westbrook, M.L.; Nance, S.; Spangler, B.D.; Scott, D.L.; Westbrook, E.M.

    1996-02-01

    The clinical manifestations of cholera are largely attributable to the actions of a secreted hexameric AB{sub 5} enterotoxin (choleragen). We have solved the three-dimensional structure of choleragen at 2.5 {Angstrom} resolution and compared the refined coordinates with those of choleragenoid (isolated B pentamer) and the heat-labile enterotoxin from Escherichia coli (LT). The crystalline coordinates provide a detailed view of the stereochemistry implicated in binding to GM1 gangliosides and in carrying out ADP-ribosylation. The A2 chain of choleragen, in contrast to that of LT, is a nearly continuous {alpha}-helix with an interpretable carboxyl tail.

  20. Alternaria brassicae produces a host-specific protein toxin from germinating spores on host leaves.

    PubMed

    Parada, R Y; Sakuno, E; Mori, N; Oka, K; Egusa, M; Kodama, M; Otani, H

    2008-04-01

    Spore suspensions of Alternaria brassicae, the causal agent of gray leaf spot in Brassica plants, were incubated on the leaves of cabbage (B. oleracea) and spore germination fluid (SGF) was collected after 48 h. A high molecular weight (HMW) fraction (>10 kDa) was separated from the SGF by ultrafiltration. In a detached leaf assay, the HMW fraction induced visible symptoms only on host leaves and the toxicity was lost by treatment with proteinase K or heat at 60 degrees C for 15 min, indicating the presence of host-specific protein toxin(s). A protein toxin in the HMW fraction was purified by several chromatography steps. The toxin induced water-soaked symptoms followed by chlorosis at concentrations of 0.5 to 1 microg/ml on host leaves, but not on nonhost leaves even at 50 microg/ml. The toxin also had infection-inducing activity when added to spore suspension of a nonpathogenic isolate of A. alternata, causing symptoms similar to the infection of A. brassicae only on host leaves. These results indicate that a new host-specific protein toxin named ABR-toxin is released from germinating spores of A. brassicae on host leaves. ABR-toxin migrated as a protein of 27.5 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The isoelectric point of ABR-toxin was estimated to be approximately 7.0 and 21 N-terminal amino acid residues were sequenced.

  1. Inflammatory events induced by brown spider venom and its recombinant dermonecrotic toxin: a pharmacological investigation.

    PubMed

    Paludo, Katia Sabrina; Biscaia, Stellee Marcela Petris; Chaim, Olga Meiri; Otuki, Michel Fleith; Naliwaiko, Katya; Dombrowski, Patrícia Andréia; Franco, Célia Regina Cavichiolo; Veiga, Silvio Sanches

    2009-04-01

    Accidents involving Brown spider (Loxosceles sp.) venom produce a massive inflammatory response in injured region. This venom has a complex mixture of different toxins, and the dermonecrotic toxin is the major contributor to toxic effects. The ability of Loxosceles intermedia venom and a recombinant isoform of dermonecrotic toxin to induce edema and increase in vascular permeability was investigated. These toxins were injected into hind paws and caused a marked dose and time-dependent edema and increase in vascular permeability in mice. Furthermore, the enzymatic activity of venom toxins may be primal for these effects. A mutated recombinant isoform of dermonecrotic toxin, that has only residual enzymatic activity, was not able to induce these inflammatory events. Besides the previous heating of toxins markedly reduced the paw edema and vascular permeability showing that thermolabile constituents can trigger these effects. In addition, the ability of these venom toxins to evoke inflammatory events was partially reduced in compound 48/80-pretreated animals, suggesting that mast cells may be involved in these responses. Pretreating mice with histamine (prometazine and cetirizine) and serotonin (methysergide) receptor antagonists significantly attenuated toxins induced edema and vascular permeability. Moreover, HPLC analysis of whole venom showed the presence of histamine sufficient to induce inflammatory responses. In conclusion, these inflammatory events may result from the activation of mast cells, which in turn release bioamines and may be related to intrinsic histamine content of venom.

  2. In Situ, High-Resolution Profiles of Labile Metals in Sediments of Lake Taihu.

    PubMed

    Wang, Dan; Gong, Mengdan; Li, Yangyang; Xu, Lv; Wang, Yan; Jing, Rui; Ding, Shiming; Zhang, Chaosheng

    2016-01-01

    Characterizing labile metal distribution and biogeochemical behavior in sediments is crucial for understanding their contamination characteristics in lakes, for which in situ, high-resolution data is scare. The diffusive gradient in thin films (DGT) technique was used in-situ at five sites across Lake Taihu in the Yangtze River delta in China to characterize the distribution and mobility of eight labile metals (Fe, Mn, Zn, Ni, Cu, Pb, Co and Cd) in sediments at a 3 mm spatial resolution. The results showed a great spatial heterogeneity in the distributions of redox-sensitive labile Fe, Mn and Co in sediments, while other metals had much less marked structure, except for downward decreases of labile Pb, Ni, Zn and Cu in the surface sediment layers. Similar distributions were found between labile Mn and Co and among labile Ni, Cu and Zn, reflecting a close link between their geochemical behaviors. The relative mobility, defined as the ratio of metals accumulated by DGT to the total contents in a volume of sediments with a thickness of 10 mm close to the surface of DGT probe, was the greatest for Mn and Cd, followed by Zn, Ni, Cu and Co, while Pb and Fe had the lowest mobility; this order generally agreed with that defined by the modified BCR approach. Further analyses showed that the downward increases of pH values in surface sediment layer may decrease the lability of Pb, Ni, Zn and Cu as detected by DGT, while the remobilization of redox-insensitive metals in deep sediment layer may relate to Mn cycling through sulphide coprecipitation, reflected by several corresponding minima between these metals and Mn. These in situ data provided the possibility for a deep insight into the mechanisms involved in the remobilization of metals in freshwater sediments. PMID:27608033

  3. In Situ, High-Resolution Profiles of Labile Metals in Sediments of Lake Taihu

    PubMed Central

    Wang, Dan; Gong, Mengdan; Li, Yangyang; Xu, Lv; Wang, Yan; Jing, Rui; Ding, Shiming; Zhang, Chaosheng

    2016-01-01

    Characterizing labile metal distribution and biogeochemical behavior in sediments is crucial for understanding their contamination characteristics in lakes, for which in situ, high-resolution data is scare. The diffusive gradient in thin films (DGT) technique was used in-situ at five sites across Lake Taihu in the Yangtze River delta in China to characterize the distribution and mobility of eight labile metals (Fe, Mn, Zn, Ni, Cu, Pb, Co and Cd) in sediments at a 3 mm spatial resolution. The results showed a great spatial heterogeneity in the distributions of redox-sensitive labile Fe, Mn and Co in sediments, while other metals had much less marked structure, except for downward decreases of labile Pb, Ni, Zn and Cu in the surface sediment layers. Similar distributions were found between labile Mn and Co and among labile Ni, Cu and Zn, reflecting a close link between their geochemical behaviors. The relative mobility, defined as the ratio of metals accumulated by DGT to the total contents in a volume of sediments with a thickness of 10 mm close to the surface of DGT probe, was the greatest for Mn and Cd, followed by Zn, Ni, Cu and Co, while Pb and Fe had the lowest mobility; this order generally agreed with that defined by the modified BCR approach. Further analyses showed that the downward increases of pH values in surface sediment layer may decrease the lability of Pb, Ni, Zn and Cu as detected by DGT, while the remobilization of redox-insensitive metals in deep sediment layer may relate to Mn cycling through sulphide coprecipitation, reflected by several corresponding minima between these metals and Mn. These in situ data provided the possibility for a deep insight into the mechanisms involved in the remobilization of metals in freshwater sediments. PMID:27608033

  4. Stoichiometric regulation of phytoplankton toxins.

    PubMed

    Van de Waal, Dedmer B; Smith, Val H; Declerck, Steven A J; Stam, Eva C M; Elser, James J

    2014-06-01

    Ecological Stoichiometry theory predicts that the production, elemental structure and cellular content of biomolecules should depend on the relative availability of resources and the elemental composition of their producer organism. We review the extent to which carbon- and nitrogen-rich phytoplankton toxins are regulated by nutrient limitation and cellular stoichiometry. Consistent with theory, we show that nitrogen limitation causes a reduction in the cellular quota of nitrogen-rich toxins, while phosphorus limitation causes an increase in the most nitrogen-rich paralytic shellfish poisoning toxin. In addition, we show that the cellular content of nitrogen-rich toxins increases with increasing cellular N : P ratios. Also consistent with theory, limitation by either nitrogen or phosphorus promotes the C-rich toxin cell quota or toxicity of phytoplankton cells. These observed relationships may assist in predicting and managing toxin-producing phytoplankton blooms. Such a stoichiometric regulation of toxins is likely not restricted to phytoplankton, and may well apply to carbon- and nitrogen-rich secondary metabolites produced by bacteria, fungi and plants.

  5. Botulinum toxin for pain.

    PubMed

    Casale, Roberto; Tugnoli, Valeria

    2008-01-01

    Botulinum toxin (BTX) injection is being increasingly used 'off label' in the management of chronic pain. Data support the hypothesis of a direct analgesic effect of BTX, different to that exerted on muscle. Although the pain-reducing effect of BTX is mainly due to its ability to block acetylcholine release at the synapse, other effects on the nervous system are also thought to be involved. BTX affects cholinergic transmission in both the somatic and the autonomic nervous systems. Proposed mechanisms of action of BTX for pain relief of trigger points, muscular spasms, fibromyalgia and myofascial pain include direct action on muscle and indirect effects via action at the neuromuscular junction. Invitro and invivo data have shown that BTX has specific antinociceptive activity relating to its effects on inflammation, axonal transport, ganglion inhibition, and spinal and suprasegmental level inhibition. Our review of the mechanisms of action, efficacy, administration techniques and therapeutic dosage of BTX for the management of chronic pain in a variety of conditions shows that although muscular tone and movement disorders remain the most important therapeutic applications for BTX, research suggests that BTX can also provide benefits related to effects on cholinergic control of the vascular system, autonomic function, and cholinergic control of nociceptive and antinociceptive systems. Furthermore, it appears that BTX may influence the peripheral and central nervous systems. The therapeutic potential of BTX depends mainly on the ability to deliver the toxin to the target structures, cholinergic or otherwise. Evidence suggests that BTX can be administered at standard dosages in pain disorders, where the objective is alteration of muscle tone. For conditions requiring an analgesic effect, the optimal therapeutic dosage of BTX remains to be defined. PMID:18095750

  6. Food toxin detection with atomic force microscope

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Externally introduced toxins or internal spoilage correlated pathogens and their metabolites are all potential sources of food toxins. To prevent and protect unsafe food, many food toxin detection techniques have been developed to detect various toxins for quality control. Although several routine m...

  7. Detecting and discriminating among Shiga toxins

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The virulence associated with Shiga toxin producing Escherichia coli (STEC) infections is from the Shiga toxins produced by the E. coli strain. Although Shiga toxins are associated with E. coli, the expression of the toxins is actually controlled by a temperate lambdoid phage that infects the host. ...

  8. [Shiga toxin and tetanus toxin as a potential biologic weapon].

    PubMed

    Toczyska, Izabela; Płusa, Tadeusz

    2015-09-01

    Toxins produced by the bacteria are of particular interest as potential cargo combat possible for use in a terrorist attack or war. Shiga toxin is usually produced by shiga toxigenic strains of Escherichia coli (STEC - shigatoxigenic Escherichia coli). To infection occurs mostly after eating contaminated beef. Clinical syndromes associated with Shiga toxin diarrhea, hemorrhagic colitis, hemolytic uremic syndrome (HUS - hemolytic uremic syndrome) or thrombotic thrombocytopenic purpura. Treatment is symptomatic. In HUS, in which mortality during an epidemic reaches 20%, extending the kidney injury dialysis may be necessary. Exposure to tetanus toxin produced by Clostridium tetani, resulting in the most generalized tetanus, characterized by increased muscle tension and painful contractions of individual muscle groups. In the treatment beyond symptomatic behavior (among others spasticity medications, anticonvulsants, muscle relaxants) is used tetanus antitoxin and antibiotics (metronidazole choice). A common complication is acute respiratory failure - then it is necessary to implement mechanical ventilation. PMID:26449578

  9. Bioactive toxins from stinging jellyfish.

    PubMed

    Badré, Sophie

    2014-12-01

    Jellyfish blooms occur throughout the world. Human contact with a jellyfish induces a local reaction of the skin, which can be painful and leave scaring. Systemic symptoms are also observed and contact with some species is lethal. A number of studies have evaluated the in vitro biological activity of whole jellyfish venom or of purified fractions. Hemolytic, cytotoxic, neurotoxic or enzymatic activities are commonly observed. Some toxins have been purified and characterized. A family of pore forming toxins specific to Medusozoans has been identified. There remains a need for detailed characterization of jellyfish toxins to fully understand the symptoms observed in vivo.

  10. Shiga Toxin Producing Escherichia coli.

    PubMed

    Bryan, Allen; Youngster, Ilan; McAdam, Alexander J

    2015-06-01

    Shiga toxin-producing Escherichia coli (STEC) is among the common causes of foodborne gastroenteritis. STEC is defined by the production of specific toxins, but within this pathotype there is a diverse group of organisms. This diversity has important consequences for understanding the pathogenesis of the organism, as well as for selecting the optimum strategy for diagnostic testing in the clinical laboratory. This review includes discussions of the mechanisms of pathogenesis, the range of manifestations of infection, and the several different methods of laboratory detection of Shiga toxin-producing E coli.

  11. THE PRODUCTION OF DIPHTHERIA TOXIN.

    PubMed

    Park, W H; Williams, A W

    1896-01-01

    Toxin of sufficient strength to kill a 400-gramme guinea-pig in three days and a half in a dose of 0.cubic centimetre developed in suitable bouillon, contained in ordinary Erlenmeyer flasks, within a period of twenty-four hours. In such boullon the toxin reached its greatest strength in from four to seven days (0.005 cubic centimetre killing a 500-gramme guinea-pig in three days). This period of time covered that of the greatest growth of the bacilli, as shown both by the appearance of the culture and by the number of colonies developing an agar plates. The bodies of the diphtheria bacili did not at any time contain toxin in cosiderable amounts. The type of growth of the bacili and the rapidity and extent of the production of toxin depended more on the reaction of the bouillon than upon any other single factor. The best results were obtained in bouillon which, after being neutralized to litmus, had about seven cubic centimetres of normal soda solution added to each litre. An excessive amount of either acid or alkali prevented the development of toxin. Strong toxin was produced in bouillon containing peptone ranging from one to ten per cent. The strength of toxin averaged greater in the two and four-per-cent peptone solutions than in the one-percent. When the stage of acid reaction was brief and the degree of acidity probably slight, strong toxin developed while the culture bouillon was still acid; but when the stage of acid reaction was prolonged, little if any toxin was produced until just before the fluid became alkaline. Glucose is deleterious to the growth of the diphtheria bacillus and to the production of toxin when it is present in sufficient amounts to cause by its disintegration too great a degree of acidity in the fluid culture. When the acid resulting from decomposition of glucose is neutralized by the addition of alkali the diphtheria bacilus again grows abundantly. Glucose is not present, at least as a rule, in sufficient amounts in the meat as

  12. Lincomycin-induced over-expression of mature recombinant cholera toxin B subunit and the holotoxin in Escherichia coli.

    PubMed

    Arimitsu, Hideyuki; Tsukamoto, Kentaro; Ochi, Sadayuki; Sasaki, Keiko; Kato, Michio; Taniguchi, Koki; Oguma, Keiji; Tsuji, Takao

    2009-10-01

    Cholera toxin (CT) B subunit (CTB) was overproduced using a novel expression system in Escherichia coli. An expression plasmid was constructed by inserting the gene encoding the full-length CTB and the Shine-Dalgarno (SD) sequence derived from CTB or from the heat-labile enterotoxin B subunit (LTB) of enterotoxigenic E. coli into the lacZalpha gene fragment in the pBluescript SK(+) vector. The E. coli strain MV1184 was transformed with each plasmid and then cultured in CAYE broth containing lincomycin. Recombinant CTB (rCTB) was purified from each cell extract. rCTB was overproduced in both transformants without obvious toxicity and was structurally and biologically identical to that of CT purified from Vibrio cholerae, indicating that the original SD and CTB signal sequences were also sufficient to express rCTB in E. coli. Lincomycin-induced rCTB expression was inhibited by mutating the lac promoter, suggesting that lincomycin affects the lactose operon. Based on these findings, we constructed a plasmid that contained the wild-type CT operon and successfully overproduced CT (rCT) using the same procedure for rCTB. Although rCT had an intact A subunit, the amino-terminal modifications and biological properties of the A and B subunits of rCT were identical to those of CT. These results suggest that this novel rCTB over-expression system would also be useful to generate both wild-type and mutant CT proteins that will facilitate further studies on the characteristics of CT, such as mucosal adjuvant activity. PMID:19410003

  13. Isolation of B subunit-specific monoclonal antibody clones that strongly neutralize the toxicity of Shiga toxin 2.

    PubMed

    Arimitsu, Hideyuki; Sasaki, Keiko; Iba, Yoshitaka; Kurosawa, Yoshikazu; Shimizu, Toshiyasu; Tsuji, Takao

    2015-02-01

    Shiga toxin 2 (Stx2)-specific mAb-producing hybridoma clones were generated from mice. Because mice tend to produce small amounts of B subunit (Stx2B)-specific antibodies at the polyclonal antibody level after immunization via the parenteral route, mice were immunized intranasally with Stx2 toxoids with a mutant heat-labile enterotoxin as a mucosal adjuvant; 11 different hybridoma clones were obtained in two trials. Six of them were A subunit (Stx2A)-specific whereas five were Stx2B-specific antibody-producing clones. The in vitro neutralization activity of Stx2B-specific mAbs against Stx2 was greater than that of Stx2A-specific mAbs on HeLa229 cells. Furthermore, even at low concentrations two of the Stx2B-specific mAbs (45 and 75D9) completely inhibited receptor binding and showed in vivo neutralization activity against a fivefold median lethal dose of Stx2 in mice. In western blot analysis, these Stx2B-specific neutralization antibodies did not react to three different mutant forms of Stx2, each amino acid residue of which was associated with receptor binding. Additionally, the nucleotide sequences of the VH and VL regions of clones 45 and 75D9 were determined. Our Stx2B-specific mAbs may be new candidates for the development of mouse-human chimeric Stx2-neutralizing antibodies which have fewer adverse effects than animal antibodies for enterohemorrhagic Escherichia coli infection.

  14. Soil Microbial and Enzymatic Responses to Complex and Labile Nutrient Inputs

    NASA Astrophysics Data System (ADS)

    Allison, S. D.; Vitousek, P. M.

    2003-12-01

    Microbial extracellular enzymes are essential for converting complex organic compounds into smaller molecules that are available for plant and microbial uptake. However, enzyme production represents a substantial resource cost for microbes, and microbes may be under selection to produce enzymes only when benefits exceed costs. We predicted that soil enzyme activities would be highest when complex substrates were abundant, but available nutrients were scarce (large potential benefit from enzyme production). We also predicted that rates of nutrient and carbon mineralization would correspond to observed shifts in enzyme activities. To test these predictions, we added insoluble and available carbon, nitrogen, and phosphorus substrates to soil incubations and measured enzyme activities, CO2 respiration, microbial biomass, and nutrient mineralization. Labile carbon additions increased respiration rates and microbial biomass, while labile nutrient additions were taken up by microbes but did not increase respiration rates. Labile carbon + nitrogen additions increased acid phosphatase activity, while labile nitrogen additions suppressed aminopeptidase activity. Insoluble nutrients caused major increases in enzyme and microbial activities only when added in combination with complementary labile nutrients (e.g. insoluble carbon + available nitrogen and phosphorus). These results indicate that microbes respond to soil nutrient status by changing patterns of extracellular enzyme production. Such changes can allow microbes to access nutrients in complex molecules, but may be limited by the availability of resources to build enzymes.

  15. Hard Exercise, Affect Lability, and Personality Among Individuals with Bulimia Nervosa

    PubMed Central

    Brownstone, Lisa M.; Fitzsimmons-Craft, Ellen E.; Wonderlich, Stephen A.; Joiner, Thomas E.; Le Grange, Daniel; Mitchell, James E.; Crow, Scott J.; Peterson, Carol B.; Crosby, Ross D.; Klein, Marjorie H.; Bardone-Cone, Anna M.

    2013-01-01

    The current study explores the personality traits of compulsivity (e.g., sense of orderliness and duty to perform tasks completely) and restricted expression (e.g., emotion expression difficulties) as potential moderators of the relation between affect lability and frequency of hard exercise episodes in a sample of individuals with bulimic pathology. Participants were 204 adult females recruited in five Midwestern cities who met criteria for threshold or subthreshold bulimia nervosa (BN). Compulsivity was found to significantly moderate the relation between affect lability and number of hard exercise episodes over the past 28 days, such that among those with high compulsivity, level of affect lability was associated with the number of hard exercise episodes; whereas, among those with low compulsivity, affect lability was not associated with the number of hard exercise episodes. The same pattern of findings emerged for restricted expression; however, this finding approached, but did not reach statistical significance. As such, it appears that affect lability is differentially related to hard exercise among individuals with BN depending upon the level of compulsivity and, to a more limited extent, restricted expression. These results suggest that, for individuals with BN with either compulsivity or restricted expression, focusing treatment on increasing flexibility and/or verbal expression of emotions may help them in the context of intense, fluctuating affect. PMID:24183126

  16. Effects of carbon substrate lability on carbon mineralization dynamics of tropical peat

    NASA Astrophysics Data System (ADS)

    Jauhiainen, Jyrki; Silvennoinen, Hanna; Könönen, Mari; Limin, Suwido; Vasander, Harri

    2016-04-01

    Extensive draining at tropical ombrotrophic peatlands in Southeast Asia has made them global 'hot spots' for greenhouse gas emissions. Management practises and fires have led to changed substrate status, which affects microbial processes. Here, we present the first data on how management practises affect carbon (C) mineralization processes at these soils. We compared the carbon mineralization potentials of pristine forest soils to those of drained fire affected soils at various depths, with and without additional labile substrates (glucose, glutamate and NO3-N) and in oxic and anoxic conditions by dedicated ex situ experiments. Carbon mineralization (CO2 and CH4 production) rates were higher in the pristine site peat, which contains more labile carbon due to higher input via vegetation. Production rates decreased with depth together with decreasing availability of labile carbon. Consequently, the increase in production rates after labile substrate addition was relatively modest from pristine site as compared to the managed site and from the top layers as compared to deeper layers. Methanogenesis had little importance in total carbon mineralization. Adding labile C and N enhanced heterotrophic CO2 production more than the sole addition of N. Surprisingly, oxygen availability was not an ultimate requirement for substantial CO2 production rates, but anoxic respiration yielded comparable rates, especially at the pristine soils. Flooding of these sites will therefore reduce, but not completely cease, peat carbon loss. Reintroduced substantial vegetation and fertilization in degraded peatlands can enrich recalcitrant peat with simple C and N compounds and thus increase microbiological activity.

  17. Analyzing a bioterror attack on the food supply: The case of botulinum toxin in milk

    PubMed Central

    Wein, Lawrence M.; Liu, Yifan

    2005-01-01

    We developed a mathematical model of a cows-to-consumers supply chain associated with a single milk-processing facility that is the victim of a deliberate release of botulinum toxin. Because centralized storage and processing lead to substantial dilution of the toxin, a minimum amount of toxin is required for the release to do damage. Irreducible uncertainties regarding the dose–response curve prevent us from quantifying the minimum effective release. However, if terrorists can obtain enough toxin, and this may well be possible, then rapid distribution and consumption result in several hundred thousand poisoned individuals if detection from early symptomatics is not timely. Timely and specific in-process testing has the potential to eliminate the threat of this scenario at a cost of <1 cent per gallon and should be pursued aggressively. Investigation of improving the toxin inactivation rate of heat pasteurization without sacrificing taste or nutrition is warranted. PMID:15985558

  18. Botulinum toxin in clinical practice

    PubMed Central

    Jankovic, J

    2004-01-01

    Botulinum toxin, the most potent biological toxin, has become a powerful therapeutic tool for a growing number of clinical applications. This review draws attention to new findings about the mechanism of action of botulinum toxin and briefly reviews some of its most frequent uses, focusing on evidence based data. Double blind, placebo controlled studies, as well as open label clinical trials, provide evidence that, when appropriate targets and doses are selected, botulinum toxin temporarily ameliorates disorders associated with excessive muscle contraction or autonomic dysfunction. When injected not more often than every three months, the risk of blocking antibodies is slight. Long term experience with this agent suggests that it is an effective and safe treatment not only for approved indications but also for an increasing number of off-label indications. PMID:15201348

  19. Development of pH-sensitive self-nanoemulsifying drug delivery systems for acid-labile lipophilic drugs.

    PubMed

    Zhao, Tianjing; Maniglio, Devid; Chen, Jie; Chen, Bin; Migliaresi, Claudio

    2016-03-01

    Oral administration is the most convenient way of all the drug delivery routes. Orally administered bioactive compounds must resist the harsh acidic fluids or enzyme digestion in stomach, to reach their absorbed destination in small intestine. This is the case for silibinin, a drug used to protect liver cells against toxins that has also been demonstrated in vitro to possess anti-cancer effects. However, as many other drugs, silibinin can degrade in the stomach due to the action of the gastric fluid. The use of pH-sensitive self-nanoemulsifying drug delivery systems (pH-SNEDDS) could overcome the drawback due to degradation of the drug in the stomach while enhancing its solubility and dissolution rate. In this paper we have investigated pH-sensitive self-nanoemulsifying formulations containing silibinin as model drug. Pseudo-ternary phase diagrams have been constructed in order to identify the self-emulsification regions under different pH. Solubility of silibinin in selected formulations has been assessed and stability of the pure drug and of the silibinin loaded pH-SNEDDS formulations in simulated gastric fluid had been compared. Droplet size of the optimized pH-SNEDDS has been correlated to pH, volume of dilution medium and silibinin loading amount. TEM (transmission electron microscopy) studies have shown that emulsion droplets had spherical shape and narrow size distribution. In vitro drug release studies of the optimal pH-SNEDDS indicated substantial increase of the drug release and release rate in comparison to pure silibinin and to the commercial silibinin tablet. The results indicated that pH-SNEDDS have potential to improve the biopharmaceutics properties of acid-labile lipophilic drugs.

  20. Comparison of metal lability in air-dried and fresh dewatered drinking water treatment residuals.

    PubMed

    Wang, Changhui; Pei, Yuansheng; Zhao, Yaqian

    2015-01-01

    In this work, the labilities of Al, As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Sr, V and Zn in air-dried (for 60 days) and fresh dewatered WTRs were compared using the Toxicity Characteristic Leaching Procedure (TCLP), fractionation, in vitro digestion and a plant enrichment test. The results showed that the air-dried and fresh dewatered WTRs had different properties, e.g., organic matter composition and available nutrients. The air-dried and fresh dewatered WTRs were non-haf zardous according to the TCLP assessment method used in the United States; however, the metals in the two types of WTRs had different lability. Compared with the metals in the fresh dewatered WTRs, those in the air-dried WTRs tended to be in more stable fractions and also exhibited lower bioaccessibility and bioavailability. Therefore, air-drying can decrease the metal lability and thereby reduce the potential metal pollution risk of WTRs.

  1. [Today's threat of ricin toxin].

    PubMed

    From, Sławomir; Płusa, Tadeusz

    2015-09-01

    Since the late 70s of the last century there were more than 700 incidents related to the use of the ricin toxin. For this reason, CDC (Center of Disease Control and Prevention) recognized toxin as a biological weapon category B. The lethal dose of ricin toxin after parenteral administration is 0.0001 mg/kg and after oral administration 0.2 mg. The first symptoms of poisoning occur within a few hours after application of toxin as a nausea, vomiting and abdominal pain. In the final stage there are observed: cardiac arrhythmia, collapse and symptoms suggestive of involvement of the central nervous system. Stage immediately preceding death is a state of coma. The ricin toxin is still the substance against which action has no optimal antidote. Developed a vaccine called RiVax is waiting for its registration. It should be pointed out that the availability of a ricin toxin makes it possible to use it for real bioterrorists. PMID:26449579

  2. Biotic and abiotic controls on diurnal fluctuations in labile soil phosphorus of a wet tropical forest.

    PubMed

    Vandecar, Karen L; Lawrence, Deborah; Wood, Tana; Oberbauer, Steven F; Das, Rishiraj; Tully, Katherine; Schwendenmann, Luitgard

    2009-09-01

    The productivity of many tropical wet forests is generally limited by bioavailable phosphorus (P). Microbial activity is a key regulator of P availability in that it determines both the supply of P through organic matter decomposition and the depletion of bioavailable P through microbial uptake. Both microbial uptake and mineralization occur rapidly, and their net effect on P availability varies with soil moisture, temperature, and soil organic matter quantity and quality. Exploring the mechanisms driving P availability at fine temporal scales can provide insight into the coupling of carbon, water, and nutrient cycles, and ultimately, the response of tropical forests to climate change. Despite the recognized importance of P cycling to the dynamics of wet tropical forests and their potential sensitivity to short-term fluctuations in bioavailable P, the diurnal pattern of P remains poorly understood. This study quantifies diurnal fluctuations in labile soil P and evaluates the importance of biotic and abiotic factors in driving these patterns. To this end, measurements of labile P were made every other hour in a Costa Rican wet tropical forest oxisol. Spatial and temporal variation in Bray-extractable P were investigated in relation to ecosystem carbon flux, soil CO2 efflux, soil moisture, soil temperature, solar radiation, and sap-flow velocity. Spatially averaged bi-hourly (every two hours) labile P ranged from 0.88 to 2.48 microg/g across days. The amplitude in labile P throughout the day was 0.61-0.82 microg/g (41-54% of mean P concentrations) and was characterized by a bimodal pattern with a decrease at midday. Labile P increased with soil CO2 efflux and soil temperature and declined with increasing sap flow and solar radiation. Together, soil CO2 efflux, soil temperature, and sap flow explained 86% of variation in labile P.

  3. Influence of yogurt fermentation and refrigerated storage on the stability of protein toxin contaminants.

    PubMed

    Jackson, Lauren S; Triplett, Odbert A; Tolleson, William H

    2015-06-01

    Dairy products sold in a ready-to-eat form present the risk that adulterants persisting through manufacturing, storage, and distribution would reach consumers. Pathogenic microbes, including shigatoxigenic strains of Escherichia coli and the toxins they produce, are common food safety hazards associated with dairy products. Ricin and abrin are plant-derived ribosome-inactivating protein toxins related to the shiga-like toxins produced by E. coli. Limited information exists on the effects of manufacturing processes on the stabilities of these heat-resistant ribosome-inactivating proteins in the presence of foods. The goal of this study was to determine how typical yogurt manufacturing and storage processes influence ribosome-inactivating protein toxins. Ricin and abrin were added to skim or whole milk and batch pasteurized. Complete inactivation of both toxins was observed after 30 minutes at 85 °C. If the toxins were added after pasteurization, the levels of ricin and abrin in yogurt and their cytotoxic activities did not change significantly during fermentation or refrigerated storage for 4 weeks. The activities of ricin and abrin were inhibited by skim milk, nonfat yogurt, whole milk, and whole milk yogurt. The results showed minimal effects of the toxins on yogurt pH and %titratable acidity but inhibitory effects of yogurt on toxin activity. PMID:25772284

  4. Influence of yogurt fermentation and refrigerated storage on the stability of protein toxin contaminants.

    PubMed

    Jackson, Lauren S; Triplett, Odbert A; Tolleson, William H

    2015-06-01

    Dairy products sold in a ready-to-eat form present the risk that adulterants persisting through manufacturing, storage, and distribution would reach consumers. Pathogenic microbes, including shigatoxigenic strains of Escherichia coli and the toxins they produce, are common food safety hazards associated with dairy products. Ricin and abrin are plant-derived ribosome-inactivating protein toxins related to the shiga-like toxins produced by E. coli. Limited information exists on the effects of manufacturing processes on the stabilities of these heat-resistant ribosome-inactivating proteins in the presence of foods. The goal of this study was to determine how typical yogurt manufacturing and storage processes influence ribosome-inactivating protein toxins. Ricin and abrin were added to skim or whole milk and batch pasteurized. Complete inactivation of both toxins was observed after 30 minutes at 85 °C. If the toxins were added after pasteurization, the levels of ricin and abrin in yogurt and their cytotoxic activities did not change significantly during fermentation or refrigerated storage for 4 weeks. The activities of ricin and abrin were inhibited by skim milk, nonfat yogurt, whole milk, and whole milk yogurt. The results showed minimal effects of the toxins on yogurt pH and %titratable acidity but inhibitory effects of yogurt on toxin activity.

  5. Antibody-based biological toxin detection

    SciTech Connect

    Menking, D.E.; Goode, M.T.

    1995-12-01

    Fiber optic evanescent fluorosensors are under investigation in our laboratory for the study of drug-receptor interactions for detection of threat agents and antibody-antigen interactions for detection of biological toxins. In a direct competition assay, antibodies against Cholera toxin, Staphylococcus Enterotoxin B or ricin were noncovalently immobilized on quartz fibers and probed with fluorescein isothiocyanate (FITC) - labeled toxins. In the indirect competition assay, Cholera toxin or Botulinum toxoid A was immobilized onto the fiber, followed by incubation in an antiserum or partially purified anti-toxin IgG. These were then probed with FITC-anti-IgG antibodies. Unlabeled toxins competed with labeled toxins or anti-toxin IgG in a dose dependent manner and the detection of the toxins was in the nanomolar range.

  6. Induction of apoptosis by Shiga toxins

    PubMed Central

    Tesh, Vernon L

    2010-01-01

    Shiga toxins comprise a family of structurally and functionally related protein toxins expressed by Shigella dysenteriae serotype 1 and multiple serotypes of Escherichia coli. While the capacity of Shiga toxins to inhibit protein synthesis by catalytic inactivation of eukaryotic ribosomes has been well described, it is also apparent that Shiga toxins trigger apoptosis in many cell types. This review presents evidence that Shiga toxins induce apoptosis of epithelial, endothelial, leukocytic, lymphoid and neuronal cells. Apoptotic signaling pathways activated by the toxins are reviewed with an emphasis on signaling mechanisms that are shared among different cell types. Data suggesting that Shiga toxins induce apoptosis through the endoplasmic reticulum stress response and clinical evidence demonstrating apoptosis in humans infected with Shiga toxin-producing bacteria are briefly discussed. The potential for use of Shiga toxins to induce apoptosis in cancer cells is briefly reviewed. PMID:20210553

  7. Nemertean toxin genes revealed through transcriptome sequencing.

    PubMed

    Whelan, Nathan V; Kocot, Kevin M; Santos, Scott R; Halanych, Kenneth M

    2014-11-27

    Nemerteans are one of few animal groups that have evolved the ability to utilize toxins for both defense and subduing prey, but little is known about specific nemertean toxins. In particular, no study has identified specific toxin genes even though peptide toxins are known from some nemertean species. Information about toxin genes is needed to better understand evolution of toxins across animals and possibly provide novel targets for pharmaceutical and industrial applications. We sequenced and annotated transcriptomes of two free-living and one commensal nemertean and annotated an additional six publicly available nemertean transcriptomes to identify putative toxin genes. Approximately 63-74% of predicted open reading frames in each transcriptome were annotated with gene names, and all species had similar percentages of transcripts annotated with each higher-level GO term. Every nemertean analyzed possessed genes with high sequence similarities to known animal toxins including those from stonefish, cephalopods, and sea anemones. One toxin-like gene found in all nemerteans analyzed had high sequence similarity to Plancitoxin-1, a DNase II hepatotoxin that may function well at low pH, which suggests that the acidic body walls of some nemerteans could work to enhance the efficacy of protein toxins. The highest number of toxin-like genes found in any one species was seven and the lowest was three. The diversity of toxin-like nemertean genes found here is greater than previously documented, and these animals are likely an ideal system for exploring toxin evolution and industrial applications of toxins.

  8. Non-labile silver species in biosolids remain stable throughout 50 years of weathering and ageing.

    EPA Science Inventory

    Increasing commercial use of nanosilver has focussed attention on the fate of silver (Ag) in the wastewater release pathway. This paper reports the speciation and lability of Ag in archived, stockpiled, and contemporary biosolids from the UK, USA and Australia, and indicates that...

  9. Measurement of labile copper in wine by medium exchange stripping potentiometry utilising screen printed carbon electrodes.

    PubMed

    Clark, Andrew C; Kontoudakis, Nikolaos; Barril, Celia; Schmidtke, Leigh M; Scollary, Geoffrey R

    2016-07-01

    The presence of copper in wine is known to impact the reductive, oxidative and colloidal stability of wine, and techniques enabling measurement of different forms of copper in wine are of particular interest in understanding these spoilage processes. Electrochemical stripping techniques developed to date require significant pretreatment of wine, potentially disturbing the copper binding equilibria. A thin mercury film on a screen printed carbon electrode was utilised in a flow system for the direct analysis of labile copper in red and white wine by constant current stripping potentiometry with medium exchange. Under the optimised conditions, including an enrichment time of 500s and constant current of 1.0μA, the response range was linear from 0.015 to 0.200mg/L. The analysis of 52 red and white wines showed that this technique generally provided lower labile copper concentrations than reported for batch measurement by related techniques. Studies in a model system and in finished wines showed that the copper sulfide was not measured as labile copper, and that loss of hydrogen sulfide via volatilisation induced an increase in labile copper within the model wine system.

  10. Occurrence and abundance of carbohydrates and amino compounds in sequentially extracted labile soil organic matter fractions.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study aimed to investigate the content of carbohydrates and amino compounds in three labile fraction of soil organic matter (SOM). Soil samples were collected from two agricultural fields in southern Italy and the light fraction (LF), the 500–53-µm particulate organic matter (POM) and the mobil...

  11. Non-labile silver species in biosolids remain stable throughout 50 years of weathering and ageing.

    PubMed

    Donner, E; Scheckel, K; Sekine, R; Popelka-Filcoff, R S; Bennett, J W; Brunetti, G; Naidu, R; McGrath, S P; Lombi, E

    2015-10-01

    Increasing commercial use of nanosilver has focussed attention on the fate of silver (Ag) in the wastewater release pathway. This paper reports the speciation and lability of Ag in archived, stockpiled, and contemporary biosolids from the UK, USA and Australia, and indicates that biosolids Ag concentrations have decreased significantly over recent decades. XANES revealed the importance of reduced-sulfur binding environments for Ag speciation in materials ranging from freshly produced sludge to biosolids weathered under ambient environmental conditions for more than 50 years. Isotopic dilution with (110 m)Ag showed that Ag was predominantly non-labile in both fresh and aged biosolids (13.7% mean lability), with E-values ranging from 0.3 to 60 mg/kg and 5 mM CaNO3 extractable Ag from 1.2 to 609 μg/kg (0.002-3.4% of the total Ag). This study indicates that at the time of soil application, biosolids Ag will be predominantly Ag-sulfides and characterised by low isotopic lability.

  12. Labile compounds in plant litter reduce the sensitivity of decomposition to warming and altered precipitation.

    PubMed

    Suseela, Vidya; Tharayil, Nishanth; Xing, Baoshan; Dukes, Jeffrey S

    2013-10-01

    Together, climate and litter quality strongly regulate decomposition rates. Although these two factors and their interaction have been studied across species in continent-scale experiments, few researchers have studied how labile and recalcitrant compounds interact to influence decomposition, or the climate sensitivity of decomposition, within a litter type. Over a period of 3 yr, we studied the effects of warming and altered precipitation on mass loss and compound-specific decomposition using two litter types that possessed similar heteropolymer chemistry, but different proportions of labile and recalcitrant compounds. Climate treatments immediately affected the mass loss of the more recalcitrant litter, but affected the more labile litter only after 2 yr. After 3 yr, although both litter types had lost similar amounts of mass, warming (c. 4°C) and supplemental precipitation (150% of ambient) together accelerated the degradation of alkyl-carbon and lignin only in the more recalcitrant litter, highlighting the role of initial litter quality in determining whether the chemistry of litter residues converges or diverges under different climates. Our finding that labile compounds in litter reduce the climate sensitivity of mass loss and the decomposition of recalcitrant matrix is novel. Our results highlight the potential for litter quality to regulate the effect of climatic changes on the sequestration of litter-derived carbon. PMID:23822593

  13. Glaciers as a source of ancient and labile organic matter to the marine environment.

    PubMed

    Hood, Eran; Fellman, Jason; Spencer, Robert G M; Hernes, Peter J; Edwards, Rick; D'Amore, David; Scott, Durelle

    2009-12-24

    Riverine organic matter supports of the order of one-fifth of estuarine metabolism. Coastal ecosystems are therefore sensitive to alteration of both the quantity and lability of terrigenous dissolved organic matter (DOM) delivered by rivers. The lability of DOM is thought to vary with age, with younger, relatively unaltered organic matter being more easily metabolized by aquatic heterotrophs than older, heavily modified material. This view is developed exclusively from work in watersheds where terrestrial plant and soil sources dominate streamwater DOM. Here we characterize streamwater DOM from 11 coastal watersheds on the Gulf of Alaska that vary widely in glacier coverage (0-64 per cent). In contrast to non-glacial rivers, we find that the bioavailability of DOM to marine microorganisms is significantly correlated with increasing (14)C age. Moreover, the most heavily glaciated watersheds are the source of the oldest ( approximately 4 kyr (14)C age) and most labile (66 per cent bioavailable) DOM. These glacial watersheds have extreme runoff rates, in part because they are subject to some of the highest rates of glacier volume loss on Earth. We estimate the cumulative flux of dissolved organic carbon derived from glaciers contributing runoff to the Gulf of Alaska at 0.13 +/- 0.01 Tg yr(-1) (1 Tg = 10(12) g), of which approximately 0.10 Tg is highly labile. This indicates that glacial runoff is a quantitatively important source of labile reduced carbon to marine ecosystems. Moreover, because glaciers and ice sheets represent the second largest reservoir of water in the global hydrologic system, our findings indicate that climatically driven changes in glacier volume could alter the age, quantity and reactivity of DOM entering coastal oceans.

  14. Fast labile carbon turnover obscures sensitivity of heterotrophic respiration from soil to temperature: A model analysis

    NASA Astrophysics Data System (ADS)

    Gu, Lianhong; Post, Wilfred M.; King, Anthony W.

    2004-03-01

    Labile carbon, although often a small fraction of soil organic carbon (SOC), significantly affects heterotrophic respiration at short timescales because of its rapid decomposition. However, in the current literature, most soil respiration measurements are interpreted without simultaneous information on labile carbon pool dynamics. Sensitivity of soil respiration to temperature is routinely derived directly from field observations, and such relationships have been used to extrapolate effects of global change (e.g., warming) on carbon emission from SOC. Here we use a multipool SOC model to demonstrate the impacts of seasonal fluctuations of labile carbon pools on interpretation of soil respiration measurements. We find that labile carbon pool sizes vary widely in response to seasonal changes in representative plant material inputs and temperature even though the model is operating at equilibrium in terms of annual means. Convolution of the dynamics of fast turnover carbon pools and temporal progression in temperature lead to misrepresentation and misinterpretation of the heterotrophic respiration-temperature relationships estimated from bulk soil CO2 exchanges. Temperature sensitivity is overestimated when the variations of labile carbon pools and temperature are in phase and underestimated when they are out of phase. Furthermore, with normally used observation time windows (weeks to a year), temperature sensitivity is more likely to be underestimated. A distortion of temperature sensitivity (Q10) from 2 (actual, sensitive dependence on temperature) to nearly 1 (false, no dependence on temperature) is shown. Applying estimated temperature sensitivity parameter back into the model considerably overestimates soil carbon storage at equilibrium. Our findings indicate that caution must be taken when soil respiration-temperature relationships are evaluated based on bulk soil observations and when sensitivity of soil respiration to temperature estimated directly under field

  15. Deletions in the repeating sequences of the toxin A gene of toxin A-negative, toxin B-positive Clostridium difficile strains.

    PubMed

    Kato, H; Kato, N; Katow, S; Maegawa, T; Nakamura, S; Lyerly, D M

    1999-06-15

    The repeating sequences of the toxin A gene from toxin A-negative, toxin B-positive (toxin A-, toxin B+) strains of Clostridium difficile which were isolated in geographically separated facilities in Japan and Indonesia were determined. All six strains tested had identical repeating sequences with two deletions (1548 and 273 nucleotides in size) in the toxin A gene. A PCR method was designed to detect the deletions and the deletions were confirmed in all 50 toxin A-, toxin B+ strains examined by this method. Western immunoblot analysis revealed that polyclonal antiserum against native toxin A did not react with the concentrated culture filtrates of the toxin A-, toxin B+ strains. These results may suggest that toxin A-, toxin B+ strains have deletions of the two thirds of the repeating regions of the toxin A gene, which encodes the epitopes fully responsible for the reaction with the polyclonal antiserum.

  16. Sodium Channel Inhibiting Marine Toxins

    NASA Astrophysics Data System (ADS)

    Llewellyn, Lyndon E.

    Saxitoxin (STX), tetrodotoxin (TTX) and their many chemical relatives are part of our daily lives. From killing people who eat seafood containing these toxins, to being valuable research tools unveiling the invisible structures of their pharmacological receptor, their global impact is beyond measure. The pharmacological receptor for these toxins is the voltage-gated sodium channel which transports Na ions between the exterior to the interior of cells. The two structurally divergent families of STX and TTX analogues bind at the same location on these Na channels to stop the flow of ions. This can affect nerves, muscles and biological senses of most animals. It is through these and other toxins that we have developed much of our fundamental understanding of the Na channel and its part in generating action potentials in excitable cells.

  17. Toxin yet not toxic: Botulinum toxin in dentistry.

    PubMed

    Archana, M S

    2016-04-01

    Paracelsus contrasted poisons from nonpoisons, stating that "All things are poisons, and there is nothing that is harmless; the dose alone decides that something is a poison". Living organisms, such as plants, animals, and microorganisms, constitute a huge source of pharmaceutically useful medicines and toxins. Depending on their source, toxins can be categorized as phytotoxins, mycotoxins, or zootoxins, which include venoms and bacterial toxins. Any toxin can be harmful or beneficial. Within the last 100 years, the perception of botulinum neurotoxin (BTX) has evolved from that of a poison to a versatile clinical agent with various uses. BTX plays a key role in the management of many orofacial and dental disorders. Its indications are rapidly expanding, with ongoing trials for further applications. However, despite its clinical use, what BTX specifically does in each condition is still not clear. The main aim of this review is to describe some of the unclear aspects of this potentially useful agent, with a focus on the current research in dentistry. PMID:27486290

  18. The tool of microbial genomics research for interpreting the lability of permafrost carbon and potential greenhouse gas feedbacks at different scales of resolution.

    NASA Astrophysics Data System (ADS)

    Waldrop, M. P.; Machelprang, R.; Hultman, J.; Wickland, K. P.

    2012-12-01

    One quarter of the earth's terrestrial surface is underlain by permafrost, or perennially frozen soils. Permafrost soils contain approximately 25% to 50% of the total global soil carbon pool nearly double the atmospheric carbon (C) reservoir. Decomposition of this C by microorganisms may produce globally significant quantities of both carbon dioxide and methane. These processes provide a positive feedback between climate change and the altered biogeochemistry of northern ecosystems. The fate of carbon residing in thawing permafrost soils depends on a number of physical factors including the thermal properties of soils (which affect heat flow rates), its disturbance regime (controlling changes in physical properties), and hydrologic regime (where soil-water interactions can rapidly thaw permafrost). Yet the mechanism of soil organic matter decomposition and greenhouse gas production operates primarily through the microbial loop: growth, carbon and nutrient mineralization, electron transfer, and enzyme production. We tested whether molecular analysis of microbial communities can be utilized as an indicator of permafrost C lability and potential greenhouse gas production from permafrost soils across multiple temporal and spatial scales. For short term studies of lability we compared rates of C turnover in soil incubations to chemical indices of soil lability, soil enzymes, and the abundance of soil microbial populations. Permafrost soils for the incubation ranged from frozen peatlands to dry uplands and Pleistocene Yedoma. For analysis at the annual to decadal scale, we utilized a permafrost thaw gradient at the Bonanza Creek LTER near Fairbanks Alaska. At this gradient, a Black Spruce forest underlain by permafrost thawed to form a thermokarst bog <50 years ago. Over the short term (months), the lability of permafrost C is reflected in the chemistry of dissolved constituents of permafrost, and it is also reflected in the change in abundance of total soil bacteria

  19. Risk assessment of shellfish toxins.

    PubMed

    Munday, Rex; Reeve, John

    2013-11-01

    Complex secondary metabolites, some of which are highly toxic to mammals, are produced by many marine organisms. Some of these organisms are important food sources for marine animals and, when ingested, the toxins that they produce may be absorbed and stored in the tissues of the predators, which then become toxic to animals higher up the food chain. This is a particular problem with shellfish, and many cases of poisoning are reported in shellfish consumers each year. At present, there is no practicable means of preventing uptake of the toxins by shellfish or of removing them after harvesting. Assessment of the risk posed by such toxins is therefore required in order to determine levels that are unlikely to cause adverse effects in humans and to permit the establishment of regulatory limits in shellfish for human consumption. In the present review, the basic principles of risk assessment are described, and the progress made toward robust risk assessment of seafood toxins is discussed. While good progress has been made, it is clear that further toxicological studies are required before this goal is fully achieved. PMID:24226039

  20. Polymer antidotes for toxin sequestration.

    PubMed

    Weisman, Adam; Chou, Beverly; O'Brien, Jeffrey; Shea, Kenneth J

    2015-08-01

    Toxins delivered by envenomation, secreted by microorganisms, or unintentionally ingested can pose an immediate threat to life. Rapid intervention coupled with the appropriate antidote is required to mitigate the threat. Many antidotes are biological products and their cost, methods of production, potential for eliciting immunogenic responses, the time needed to generate them, and stability issues contribute to their limited availability and effectiveness. These factors exacerbate a world-wide challenge for providing treatment. In this review we evaluate a number of polymer constructs that may serve as alternative antidotes. The range of toxins investigated includes those from sources such as plants, animals and bacteria. The development of polymeric heavy metal sequestrants for use as antidotes to heavy metal poisoning faces similar challenges, thus recent findings in this area have also been included. Two general strategies have emerged for the development of polymeric antidotes. In one, the polymer acts as a scaffold for the presentation of ligands with a known affinity for the toxin. A second strategy is to generate polymers with an intrinsic affinity, and in some cases selectivity, to a range of toxins. Importantly, in vivo efficacy has been demonstrated for each of these strategies, which suggests that these approaches hold promise as an alternative to biological or small molecule based treatments.

  1. Risk Assessment of Shellfish Toxins

    PubMed Central

    Munday, Rex; Reeve, John

    2013-01-01

    Complex secondary metabolites, some of which are highly toxic to mammals, are produced by many marine organisms. Some of these organisms are important food sources for marine animals and, when ingested, the toxins that they produce may be absorbed and stored in the tissues of the predators, which then become toxic to animals higher up the food chain. This is a particular problem with shellfish, and many cases of poisoning are reported in shellfish consumers each year. At present, there is no practicable means of preventing uptake of the toxins by shellfish or of removing them after harvesting. Assessment of the risk posed by such toxins is therefore required in order to determine levels that are unlikely to cause adverse effects in humans and to permit the establishment of regulatory limits in shellfish for human consumption. In the present review, the basic principles of risk assessment are described, and the progress made toward robust risk assessment of seafood toxins is discussed. While good progress has been made, it is clear that further toxicological studies are required before this goal is fully achieved. PMID:24226039

  2. MCEARD - CYANOBACTERIA AND THEIR TOXINS

    EPA Science Inventory

    Harmful algal blooms (HAB) of cyanobacteria, also known as blue-green algae, have recently become more spatially and temporally prevalent in the US and worldwide. Waterborne cyanobacteria and their highly potent toxins are a significant hazard for human health and the ecosystem....

  3. Novel receptors for bacterial protein toxins.

    PubMed

    Schmidt, Gudula; Papatheodorou, Panagiotis; Aktories, Klaus

    2015-02-01

    While bacterial effectors are often directly introduced into eukaryotic target cells by various types of injection machines, toxins enter the cytosol of host cells from endosomal compartments or after retrograde transport via Golgi from the ER. A first crucial step of toxin-host interaction is receptor binding. Using optimized protocols and new methods novel toxin receptors have been identified, including metalloprotease ADAM 10 for Staphylococcus aureus α-toxin, laminin receptor Lu/BCAM for Escherichia coli cytotoxic necrotizing factor CNF1, lipolysis stimulated lipoprotein receptor (LSR) for Clostridium difficile transferase CDT and low-density lipoprotein receptor-related protein (LRP) 1 for Clostridium perfringens TpeL toxin.

  4. Inactivation of allergens and toxins.

    PubMed

    Morandini, Piero

    2010-11-30

    Plants are replete with thousands of proteins and small molecules, many of which are species-specific, poisonous or dangerous. Over time humans have learned to avoid dangerous plants or inactivate many toxic components in food plants, but there is still room for ameliorating food crops (and plants in general) in terms of their allergens and toxins content, especially in their edible parts. Inactivation at the genetic rather than physical or chemical level has many advantages and classical genetic approaches have resulted in significant reduction of toxin content. The capacity, offered by genetic engineering, of turning off (inactivating) specific genes has opened up the possibility of altering the plant content in a far more precise manner than previously available. Different levels of intervention (genes coding for toxins/allergens or for enzymes, transporters or regulators involved in their metabolism) are possible and there are several tools for inactivating genes, both direct (using chemical and physical mutagens, insertion of transposons and other genetic elements) and indirect (antisense RNA, RNA interference, microRNA, eventually leading to gene silencing). Each level/strategy has specific advantages and disadvantages (speed, costs, selectivity, stability, reversibility, frequency of desired genotype and regulatory regime). Paradigmatic examples from classical and transgenic approaches are discussed to emphasize the need to revise the present regulatory process. Reducing the content of natural toxins is a trade-off process: the lesser the content of natural toxins, the higher the susceptibility of a plant to pests and therefore the stronger the need to protect plants. As a consequence, more specific pesticides like Bt are needed to substitute for general pesticides.

  5. Toxins as Weapons: A Historical Review.

    PubMed

    Pita, R; Romero, A

    2014-07-01

    This review article summarizes the use of toxins as weapons dating from the First World War until today, when there is a high concern of possible terrorist attacks with weapons of mass destruction. All through modern history, military programs and terrorist groups have favored toxins because of their high toxicity. However, difficulties of extraction or synthesis, as well as effective dissemination to cause a large number of casualties, have been the most important drawbacks. Special emphasis is focused on ricin and botulinum toxin, the most important toxins that have attracted the attention of military programs and terrorist groups. Other toxins like trichothecenes, saxitoxin, and Staphylococcal enterotoxin B (SEB) are also discussed. A short section about anthrax is also included: Although Bacillus anthracis is considered a biological weapon rather than a toxin weapon, it produces a toxin that is finally responsible for the anthrax disease. PMID:26227025

  6. Binding of cholera toxin by various tissues.

    PubMed

    Gascoyne, N; Van Heyningen, W E

    1975-09-01

    Under certain conditions, it is possible to confirm the observation by Peterson (1974) that the cholera toxin-binding capacities of tissues from brain and colon mucosa, and from liver and small intestine mucosa, are comparable. Binding of toxin by all tissues except brain is very variable, but is roughtly proportional to their content of the toxin-binding ganglioside galactosyl-N-acetylgalactosaminyl (sialosyl) lactosyl ceramide. It appears that some toxin-binding sites of the mucosa of the small intestin and colon may be masked. It has also been confirmed that there may be some solubilization of toxin-binding material from brain on standing a few days at 4 C, but this is comparatively slight. Some disadvantages of measuring toxin binding by adding small amounts of radioactive toxin to compartively large amounts of tissue are discussed.

  7. Toxins as Weapons: A Historical Review.

    PubMed

    Pita, R; Romero, A

    2014-07-01

    This review article summarizes the use of toxins as weapons dating from the First World War until today, when there is a high concern of possible terrorist attacks with weapons of mass destruction. All through modern history, military programs and terrorist groups have favored toxins because of their high toxicity. However, difficulties of extraction or synthesis, as well as effective dissemination to cause a large number of casualties, have been the most important drawbacks. Special emphasis is focused on ricin and botulinum toxin, the most important toxins that have attracted the attention of military programs and terrorist groups. Other toxins like trichothecenes, saxitoxin, and Staphylococcal enterotoxin B (SEB) are also discussed. A short section about anthrax is also included: Although Bacillus anthracis is considered a biological weapon rather than a toxin weapon, it produces a toxin that is finally responsible for the anthrax disease.

  8. Flocculated meltwater particles control Arctic land-sea fluxes of labile iron.

    PubMed

    Markussen, Thor Nygaard; Elberling, Bo; Winter, Christian; Andersen, Thorbjørn Joest

    2016-01-01

    Glacial meltwater systems supply the Arctic coastal ocean with large volumes of sediment and potentially bioavailable forms of iron, nitrogen and carbon. The particulate fraction of this supply is significant but estuarine losses have been thought to limit the iron supply from land. Here, our results reveal how flocculation (particle aggregation) involving labile iron may increase horizontal transport rather than enhance deposition close to the source. This is shown by combining field observations in Disko Fjord, West Greenland, and laboratory experiments. Our data show how labile iron affects floc sizes, shapes and densities and consequently yields low settling velocities and extended sediment plumes. We highlight the importance of understanding the flocculation mechanisms when examining fluxes of meltwater transported iron in polar regions today and in the future, and we underline the influence of terrestrial hotspots on the nutrient and solute cycles in Arctic coastal waters. PMID:27050673

  9. Flocculated meltwater particles control Arctic land-sea fluxes of labile iron

    PubMed Central

    Markussen, Thor Nygaard; Elberling, Bo; Winter, Christian; Andersen, Thorbjørn Joest

    2016-01-01

    Glacial meltwater systems supply the Arctic coastal ocean with large volumes of sediment and potentially bioavailable forms of iron, nitrogen and carbon. The particulate fraction of this supply is significant but estuarine losses have been thought to limit the iron supply from land. Here, our results reveal how flocculation (particle aggregation) involving labile iron may increase horizontal transport rather than enhance deposition close to the source. This is shown by combining field observations in Disko Fjord, West Greenland, and laboratory experiments. Our data show how labile iron affects floc sizes, shapes and densities and consequently yields low settling velocities and extended sediment plumes. We highlight the importance of understanding the flocculation mechanisms when examining fluxes of meltwater transported iron in polar regions today and in the future, and we underline the influence of terrestrial hotspots on the nutrient and solute cycles in Arctic coastal waters. PMID:27050673

  10. Effect of hydrogen sulfide on phosphorus lability in lake sediments amended with drinking water treatment residuals.

    PubMed

    Wang, Changhui; Liu, Juanfeng; Pei, Yuansheng

    2013-05-01

    The use of drinking water treatment residuals (WTRs) to immobilize P in sediments is a novel approach for lake restoration. However, the lability of P in WTRs-amended sediments may vary with many factors, e.g., hydrogen sulfide content. Earlier works in our laboratory have demonstrated that WTRs are effective sorbents for hydrogen sulfide in water. Thus, we hypothesized that the lability of P in WTRs-amended sediments would not be increased by hydrogen sulfide. The results of this work suggested that this hypothesis was tenable. Compared to the raw sediments, the amended sediments had significantly lower P desorption potential in the presence of hydrogen sulfide at different times, pH and concentrations. Moreover, the amended sediments were also better able to adsorb hydrogen sulfide. In the amended sediments, the P, which was easily desorbed due to the effect of hydrogen sulfide, was transformed into the Fe/Al bound P.

  11. Lability of potentially toxic elements in soils affected by smelting activities.

    PubMed

    Popescu, I; Biasioli, M; Ajmone-Marsan, F; Stănescu, R

    2013-01-01

    Determination of total concentration of potentially toxic elements (PTEs) in soil is not a reliable tool for evaluating potential exposure risk for humans. PTE lability (EDTA, SBET and solution extraction) and chemical speciation (BCR sequential extraction) were investigated for Pb, Cd, Cu, and Zn, as well as how these could be affected by flooding in soils polluted by smelting activities. The flooding experiment was performed in pots from which soil solution was extracted at different time intervals using Rhizon Moisture Samplers. After experiments, the soil was again subjected to the previous extractions (EDTA, SBET, and BCR) in order to reveal the changes which occurred during anoxia. From the results we can conclude that PTE lability is very high and flooding caused the increase in their mobility up to 100% (for bioaccessible Pb). The experiment demonstrated that temporary reducing conditions can increase the risk of contaminants passing to other environmental compartments and the food chain.

  12. Lability of potentially toxic elements in soils affected by smelting activities.

    PubMed

    Popescu, I; Biasioli, M; Ajmone-Marsan, F; Stănescu, R

    2013-01-01

    Determination of total concentration of potentially toxic elements (PTEs) in soil is not a reliable tool for evaluating potential exposure risk for humans. PTE lability (EDTA, SBET and solution extraction) and chemical speciation (BCR sequential extraction) were investigated for Pb, Cd, Cu, and Zn, as well as how these could be affected by flooding in soils polluted by smelting activities. The flooding experiment was performed in pots from which soil solution was extracted at different time intervals using Rhizon Moisture Samplers. After experiments, the soil was again subjected to the previous extractions (EDTA, SBET, and BCR) in order to reveal the changes which occurred during anoxia. From the results we can conclude that PTE lability is very high and flooding caused the increase in their mobility up to 100% (for bioaccessible Pb). The experiment demonstrated that temporary reducing conditions can increase the risk of contaminants passing to other environmental compartments and the food chain. PMID:23127724

  13. Flocculated meltwater particles control Arctic land-sea fluxes of labile iron

    NASA Astrophysics Data System (ADS)

    Markussen, Thor Nygaard; Elberling, Bo; Winter, Christian; Andersen, Thorbjørn Joest

    2016-04-01

    Glacial meltwater systems supply the Arctic coastal ocean with large volumes of sediment and potentially bioavailable forms of iron, nitrogen and carbon. The particulate fraction of this supply is significant but estuarine losses have been thought to limit the iron supply from land. Here, our results reveal how flocculation (particle aggregation) involving labile iron may increase horizontal transport rather than enhance deposition close to the source. This is shown by combining field observations in Disko Fjord, West Greenland, and laboratory experiments. Our data show how labile iron affects floc sizes, shapes and densities and consequently yields low settling velocities and extended sediment plumes. We highlight the importance of understanding the flocculation mechanisms when examining fluxes of meltwater transported iron in polar regions today and in the future, and we underline the influence of terrestrial hotspots on the nutrient and solute cycles in Arctic coastal waters.

  14. Relationship between the lability of sediment-bound Cd and its bioaccumulation in edible oyster.

    PubMed

    Chakraborty, Parthasarathi; Ramteke, Darwin; Chakraborty, Sucharita; Chennuri, Kartheek; Bardhan, Pratirupa

    2015-11-15

    A linkage between Cd speciation in sediments and its bioaccumulation in edible oyster (Crassostrea sp.) from a tropical estuarine system was established. Bioaccumulation of Cd in edible oyster increased with the increasing lability and dissociation rate constants of Cd-sediment complexes in the bottom sediments. Total Cd concentration in sediment was not a good indicator of Cd-bioavailability. Increasing trace metal competition in sediments increased lability and bioavailability of Cd in the tropical estuarine sediment. Low thermodynamic stability and high bioavailability of Cd in the estuarine sediment were responsible for high bioaccumulation of Cd in edible oysters (3.2-12.2mgkg(-1)) even though the total concentration of Cd in the bottom sediment was low (0.17-0.49mgkg(-1)).

  15. Glycosylation efficiencies on different solid supports using a hydrogenolysis-labile linker

    PubMed Central

    Collot, Mayeul; Eller, Steffen; Weishaupt, Markus

    2013-01-01

    Summary Automated oligosaccharide assembly requires suitable linkers to connect the first monosaccharide to a solid support. A new hydrogenolysis-labile linker that is stable under both acidic and basic conditions was designed, synthesized and coupled to different resins. Glycosylation and cleavage efficiencies on these functionalized solid supports were investigated, and restrictions for the choice of solid support for oligosaccharide synthesis were found. PMID:23400514

  16. Protein degradation by ubiquitin–proteasome system in formation and labilization of contextual conditioning memory

    PubMed Central

    Sol Fustiñana, María; de la Fuente, Verónica; Federman, Noel; Freudenthal, Ramiro

    2014-01-01

    The ubiquitin–proteasome system (UPS) of protein degradation has been evaluated in different forms of neural plasticity and memory. The role of UPS in such processes is controversial. Several results support the idea that the activation of this system in memory consolidation is necessary to overcome negative constrains for plasticity. In this case, the inhibition of the UPS during consolidation impairs memory. Similar results were reported for memory reconsolidation. However, in other cases, the inhibition of UPS had no effect on memory consolidation and reconsolidation but impedes the amnesic action of protein synthesis inhibition after retrieval. The last finding suggests a specific action of the UPS inhibitor on memory labilization. However, another interpretation is possible in terms of the synthesis/degradation balance of positive and negative elements in neural plasticity, as was found in the case of long-term potentiation. To evaluate these alternative interpretations, other reconsolidation-interfering drugs than translation inhibitors should be tested. Here we analyzed initially the UPS inhibitor effect in contextual conditioning in crabs. We found that UPS inhibition during consolidation impaired long-term memory. In contrast, UPS inhibition did not affect memory reconsolidation after contextual retrieval but, in fact, impeded memory labilization, blocking the action of drugs that does not affect directly the protein synthesis. To extend these finding to vertebrates, we performed similar experiments in contextual fear memory in mice. We found that the UPS inhibitor in hippocampus affected memory consolidation and blocked memory labilization after retrieval. These findings exclude alternative interpretations to the requirement of UPS in memory labilization and give evidence of this mechanism in both vertebrates and invertebrates. PMID:25135196

  17. Labile and stabilised fractions of soil organic carbon in some intensively cultivated alluvial soils.

    PubMed

    Verma, B C; Datta, S P; Rattan, R K; Singh, A K

    2013-11-01

    The present investigation was undertaken in view of the limited information on the relative proportion of labile and stabilized fractions of soil organic carbon (SOC) in intensively cultivated lands, particularly under tropics. The specific objectives were i) to study the comparative recovery of SOC by different methods of labile carbon estimation under intensively cultivated lands and ii) to evaluate the impact of agricultural practices on carbon management index. For this purpose, in all, 105 surface soil samples were collected from intensively cultivated tube well and sewage irrigated agricultural lands. These samples were analysed for total as well as labile pools of SOC. Results indicated that Walkley and Black, KMnO4-oxidizable and microbial biomass carbon constituted the total SOC to the extent of 10.2 to 47.4, 1.66 to 23.2 and 0.30 to 5.49%, respectively with the corresponding mean values of 26.2, 9.16 and 2.15%. Lability of SOC was considerably higher in sewage irrigated soils than tube well irrigated soils under intensive cropping. Under soybean-wheat, the higher values of carbon management index (CMI) (279 and 286) were associated with the treatments where entire amount of nitrogen was supplied through FYM. Similar results were obtained under rice-wheat, whereas in case of maize-wheat the highest value of CMI was recorded under treatment receiving NPK through chemical fertilizer along with green manure. There was also a significant improvement in CMI under integrated (chemical fertilizer + organics) and chemical fertilizer-treated plots. The values of CMI ranged from 220 to 272 under cultivated lands receiving irrigation through sewage and industrial effluents. PMID:24555339

  18. Bis(haloBODIPYs) with Labile Helicity: Valuable Simple Organic Molecules That Enable Circularly Polarized Luminescence.

    PubMed

    Ray, César; Sánchez-Carnerero, Esther M; Moreno, Florencio; Maroto, Beatriz L; Agarrabeitia, Antonia R; Ortiz, María J; López-Arbeloa, Íñigo; Bañuelos, Jorge; Cohovi, Komlan D; Lunkley, Jamie L; Muller, Gilles; de la Moya, Santiago

    2016-06-20

    Simple organic molecules (SOM) based on bis(haloBODIPY) are shown to enable circularly polarized luminescence (CPL), giving rise to a new structural design for technologically valuable CPL-SOMs. The established design comprises together synthetic accessibility, labile helicity, possibility of reversing the handedness of the circularly polarized emission, and reactive functional groups, making it unique and attractive as advantageous platform for the development of smart CPL-SOMs.

  19. Protein degradation by ubiquitin-proteasome system in formation and labilization of contextual conditioning memory.

    PubMed

    Sol Fustiñana, María; de la Fuente, Verónica; Federman, Noel; Freudenthal, Ramiro; Romano, Arturo

    2014-09-01

    The ubiquitin-proteasome system (UPS) of protein degradation has been evaluated in different forms of neural plasticity and memory. The role of UPS in such processes is controversial. Several results support the idea that the activation of this system in memory consolidation is necessary to overcome negative constrains for plasticity. In this case, the inhibition of the UPS during consolidation impairs memory. Similar results were reported for memory reconsolidation. However, in other cases, the inhibition of UPS had no effect on memory consolidation and reconsolidation but impedes the amnesic action of protein synthesis inhibition after retrieval. The last finding suggests a specific action of the UPS inhibitor on memory labilization. However, another interpretation is possible in terms of the synthesis/degradation balance of positive and negative elements in neural plasticity, as was found in the case of long-term potentiation. To evaluate these alternative interpretations, other reconsolidation-interfering drugs than translation inhibitors should be tested. Here we analyzed initially the UPS inhibitor effect in contextual conditioning in crabs. We found that UPS inhibition during consolidation impaired long-term memory. In contrast, UPS inhibition did not affect memory reconsolidation after contextual retrieval but, in fact, impeded memory labilization, blocking the action of drugs that does not affect directly the protein synthesis. To extend these finding to vertebrates, we performed similar experiments in contextual fear memory in mice. We found that the UPS inhibitor in hippocampus affected memory consolidation and blocked memory labilization after retrieval. These findings exclude alternative interpretations to the requirement of UPS in memory labilization and give evidence of this mechanism in both vertebrates and invertebrates.

  20. Nemertean Toxin Genes Revealed through Transcriptome Sequencing

    PubMed Central

    Whelan, Nathan V.; Kocot, Kevin M.; Santos, Scott R.; Halanych, Kenneth M.

    2014-01-01

    Nemerteans are one of few animal groups that have evolved the ability to utilize toxins for both defense and subduing prey, but little is known about specific nemertean toxins. In particular, no study has identified specific toxin genes even though peptide toxins are known from some nemertean species. Information about toxin genes is needed to better understand evolution of toxins across animals and possibly provide novel targets for pharmaceutical and industrial applications. We sequenced and annotated transcriptomes of two free-living and one commensal nemertean and annotated an additional six publicly available nemertean transcriptomes to identify putative toxin genes. Approximately 63–74% of predicted open reading frames in each transcriptome were annotated with gene names, and all species had similar percentages of transcripts annotated with each higher-level GO term. Every nemertean analyzed possessed genes with high sequence similarities to known animal toxins including those from stonefish, cephalopods, and sea anemones. One toxin-like gene found in all nemerteans analyzed had high sequence similarity to Plancitoxin-1, a DNase II hepatotoxin that may function well at low pH, which suggests that the acidic body walls of some nemerteans could work to enhance the efficacy of protein toxins. The highest number of toxin-like genes found in any one species was seven and the lowest was three. The diversity of toxin-like nemertean genes found here is greater than previously documented, and these animals are likely an ideal system for exploring toxin evolution and industrial applications of toxins. PMID:25432940

  1. Consolidated and labile odor memory are separately encoded within the Drosophila brain.

    PubMed

    Scheunemann, Lisa; Jost, Eva; Richlitzki, Antje; Day, Jonathan P; Sebastian, Sujith; Thum, Andreas S; Efetova, Marina; Davies, Shireen-A; Schwärzel, Martin

    2012-11-28

    Memories are classified as consolidated (stable) or labile according to whether they withstand amnestic treatment, or not. In contrast to the general prevalence of this classification, its neuronal and molecular basis is poorly understood. Here, we focused on consolidated and labile memories induced after a single cycle training in the Drosophila aversive olfactory conditioning paradigm and we used mutants to define the impact of cAMP signals. At the biochemical level we report that cAMP signals misrelated in either rutabaga (rut) or dunce (dnc) mutants separate between consolidated anesthesia-resistant memory (ARM) and labile anesthesia-sensitive memory (ASM). Those functionally distinct cAMP signals act within different neuronal populations: while rut-dependent cAMP signals act within Kenyon cells (KCs) of the mushroom bodies to support ASM, dnc-sensitive cAMP signals support ARM within antennal lobe local neurons (LNs) and KCs. Collectively, different key positions along the olfactory circuitry seem to get modified during storage of ARM or ASM independently. A precise separation between those functionally distinct cAMP signals seems mandatory to allocate how they support appropriate memories.

  2. Effects of chemical amendments on the lability and speciation of metals in anaerobically digested biosolids.

    PubMed

    Donner, Erica; Brunetti, Gianluca; Zarcinas, Bernie; Harris, Paul; Tavakkoli, Ehsan; Naidu, Ravi; Lombi, Enzo

    2013-10-01

    The interaction of inorganic contaminants present in biosolids with iron, aluminum, and manganese oxy/hydroxides has been advocated as a key mechanism limiting their bioavailability. In this study, we investigated whether this is indeed the case, and further, whether it can be exploited to produce optimized biosolids products through the addition of chemical additives during sewage sludge processing. Experiments were conducted to investigate whether the addition of iron- and aluminum-based amendments (at 5 different rates) during the anaerobic digestion phase of wastewater treatment can effectively change the speciation or lability of contaminant metals (copper, zinc and cadmium) in biosolids destined for use in agriculture. The performance of the bioreactors was monitored throughout and the speciation and lability were determined in both fresh and 3-month aged biosolids using X-ray absorption spectroscopy (Cu, Zn) and isotopic dilution ((65)Cu, (65)Zn, (109)Cd). The tested amendments (FeCl3, Al2(SO4)3, and Al-rich water treatment residual) did not cause significant changes in metal speciation and were of limited use for reducing the lability of contaminant metals in good quality biosolids (suitable for use in agriculture), suggesting that high affinity binding sites were already in excess in these materials. However, the use of chemical amendments may offer advantages in terms of treatment process optimization and may also be beneficial when biosolids are used for contaminated site remediation. PMID:23981056

  3. Substrate lability and plant activity controls greenhouse gas release from Neotropical peatland

    NASA Astrophysics Data System (ADS)

    Sjogersten, Sofie; Hoyos, Jorge; Lomax, Barry; Turner, Ben; Wright, Emma

    2014-05-01

    Almost one third of global CO2 emissions resulting from land use change and substantial CH4 emissions originate from tropical peatlands. However, our understanding of the controls of CO2 and CH4 release from tropical peatlands are limited. The aim of this study was to investigate the role of peat lability and the activity of the vegetation on gas release using a combination of field and laboratory experiments. We demonstrated that peat lability constrained CH4 production to the surface peat under anaerobic conditions. The presence of plants shifted the C balance from a C source to a C sink with respect to CO2 while the activity of the root system strongly influenced CH4 emissions through its impact on soil O2 inputs. Both field and laboratory data suggest a coupling between the photosynthetic activity of the vegetation and the release of both CO2 and CH4 following the circadian rhythm of the dominant plant functional types. Forest clearance for agriculture resulted in elevated CH4 release, which we attribute in part to the cessation of root O2 inputs to the peat. We conclude that high emissions of CO2 and CH4 from forested tropical peatlands are likely driven by labile C inputs from the vegetation but that root O2 release may limit CH4 emissions.

  4. Evolution of phenotypic plasticity and environmental tolerance of a labile quantitative character in a fluctuating environment.

    PubMed

    Lande, R

    2014-05-01

    Quantitative genetic models of evolution of phenotypic plasticity are used to derive environmental tolerance curves for a population in a changing environment, providing a theoretical foundation for integrating physiological and community ecology with evolutionary genetics of plasticity and norms of reaction. Plasticity is modelled for a labile quantitative character undergoing continuous reversible development and selection in a fluctuating environment. If there is no cost of plasticity, a labile character evolves expected plasticity equalling the slope of the optimal phenotype as a function of the environment. This contrasts with previous theory for plasticity influenced by the environment at a critical stage of early development determining a constant adult phenotype on which selection acts, for which the expected plasticity is reduced by the environmental predictability over the discrete time lag between development and selection. With a cost of plasticity in a labile character, the expected plasticity depends on the cost and on the environmental variance and predictability averaged over the continuous developmental time lag. Environmental tolerance curves derived from this model confirm traditional assumptions in physiological ecology and provide new insights. Tolerance curve width increases with larger environmental variance, but can only evolve within a limited range. The strength of the trade-off between tolerance curve height and width depends on the cost of plasticity. Asymmetric tolerance curves caused by male sterility at high temperature are illustrated. A simple condition is given for a large transient increase in plasticity and tolerance curve width following a sudden change in average environment.

  5. Labile soil carbon inputs mediate the soil microbial community composition and plant residue decomposition rates

    SciTech Connect

    De Graaff, Marie-Anne; Classen, Aimee T; Castro Gonzalez, Hector F; Schadt, Christopher Warren

    2010-01-01

    Root carbon (C) inputs may regulate decomposition rates in soil, and in this study we ask: how do labile C inputs regulate decomposition of plant residues, and soil microbial communities? In a 14 d laboratory incubation, we added C compounds often found in root exudates in seven different concentrations (0, 0.7, 1.4, 3.6, 7.2, 14.4 and 21.7 mg C g{sup -1} soil) to soils amended with and without {sup 13}C-labeled plant residue. We measured CO{sub 2} respiration and shifts in relative fungal and bacterial rRNA gene copy numbers using quantitative polymerase chain reaction (qPCR). Increased labile C input enhanced total C respiration, but only addition of C at low concentrations (0.7 mg C g{sup -1}) stimulated plant residue decomposition (+2%). Intermediate concentrations (1.4, 3.6 mg C g{sup -1}) had no impact on plant residue decomposition, while greater concentrations of C (> 7.2 mg C g{sup -1}) reduced decomposition (-50%). Concurrently, high exudate concentrations (> 3.6 mg C g{sup -1}) increased fungal and bacterial gene copy numbers, whereas low exudate concentrations (< 3.6 mg C g{sup -1}) increased metabolic activity rather than gene copy numbers. These results underscore that labile soil C inputs can regulate decomposition of more recalcitrant soil C by controlling the activity and relative abundance of fungi and bacteria.

  6. YoeB toxin is activated during thermal stress

    PubMed Central

    Janssen, Brian D; Garza-Sánchez, Fernando; Hayes, Christopher S

    2015-01-01

    Type II toxin-antitoxin (TA) modules are thought to mediate stress-responses by temporarily suppressing protein synthesis while cells redirect transcription to adapt to environmental change. Here, we show that YoeB, a ribosome-dependent mRNase toxin, is activated in Escherichia coli cells grown at elevated temperatures. YoeB activation is dependent on Lon protease, suggesting that thermal stress promotes increased degradation of the YefM antitoxin. Though YefM is efficiently degraded in response to Lon overproduction, we find that Lon antigen levels do not increase during heat shock, indicating that another mechanism accounts for temperature-induced YefM proteolysis. These observations suggest that YefM/YoeB functions in adaptation to temperature stress. However, this response is distinct from previously described models of TA function. First, YoeB mRNase activity is maintained over several hours of culture at 42°C, indicating that thermal activation is not transient. Moreover, heat-activated YoeB does not induce growth arrest nor does it suppress global protein synthesis. In fact, E. coli cells proliferate more rapidly at elevated temperatures and instantaneously accelerate their growth rate in response to acute heat shock. We propose that heat-activated YoeB may serve a quality control function, facilitating the recycling of stalled translation complexes through ribosome rescue pathways. PMID:26147890

  7. Molecular insights into the microbial formation of marine dissolved organic matter: recalcitrant or labile?

    NASA Astrophysics Data System (ADS)

    Koch, B. P.; Kattner, G.; Witt, M.; Passow, U.

    2014-08-01

    The degradation of marine dissolved organic matter (DOM) is an important control variable in the global carbon cycle. For our understanding of the kinetics of organic matter cycling in the ocean, it is crucial to achieve a mechanistic and molecular understanding of its transformation processes. A long-term microbial experiment was performed to follow the production of non-labile DOM by marine bacteria. Two different glucose concentrations and dissolved algal exudates were used as substrates. We monitored the bacterial abundance, concentrations of dissolved and particulate organic carbon (DOC, POC), nutrients, amino acids and transparent exopolymer particles (TEP) for 2 years. The molecular characterization of extracted DOM was performed by ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) after 70 days and after ∼2 years of incubation. Although glucose quickly degraded, a non-labile DOC background (5-9% of the initial DOC) was generated in the glucose incubations. Only 20% of the organic carbon from the algal exudate degraded within the 2 years of incubation. The degradation rates for the non-labile DOC background in the different treatments varied between 1 and 11 μmol DOC L-1 year-1. Transparent exopolymer particles, which are released by microorganisms, were produced during glucose degradation but decreased back to half of the maximum concentration within less than 3 weeks (degradation rate: 25 μg xanthan gum equivalents L-1 d-1) and were below detection in all treatments after 2 years. Additional glucose was added after 2 years to test whether labile substrate can promote the degradation of background DOC (co-metabolism; priming effect). A priming effect was not observed but the glucose addition led to a slight increase of background DOC. The molecular analysis demonstrated that DOM generated during glucose degradation differed appreciably from DOM transformed during the degradation of the algal exudates. Our

  8. Assessing the Selectivity of Extractant Solutions for Recovering Labile Arsenic Associated with Iron (Hydr)oxides and Sulfides in Sediments

    EPA Science Inventory

    Sequential extractions can provide analytical constraints on the identification of mineral phases that control arsenic speciation in sediments. Model solids were used in this study to evaluate different solutions designed to extract arsenic from relatively labile solid phases. ...

  9. Why do we study animal toxins?

    PubMed Central

    ZHANG, Yun

    2015-01-01

    Venom (toxins) is an important trait evolved along the evolutionary tree of animals. Our knowledges on venoms, such as their origins and loss, the biological relevance and the coevolutionary patterns with other organisms are greatly helpful in understanding many fundamental biological questions, i.e., the environmental adaptation and survival competition, the evolution shaped development and balance of venoms, and the sophisticated correlations among venom, immunity, body power, intelligence, their genetic basis, inherent association, as well as the cost-benefit and trade-offs of biological economy. Lethal animal envenomation can be found worldwide. However, from foe to friend, toxin studies have led lots of important discoveries and exciting avenues in deciphering and fighting human diseases, including the works awarded the Nobel Prize and lots of key clinic therapeutics. According to our survey, so far, only less than 0.1% of the toxins of the venomous animals in China have been explored. We emphasize on the similarities shared by venom and immune systems, as well as the studies of toxin knowledge-based physiological toxin-like proteins/peptides (TLPs). We propose the natural pairing hypothesis. Evolution links toxins with humans. Our mission is to find out the right natural pairings and interactions of our body elements with toxins, and with endogenous toxin-like molecules. Although, in nature, toxins may endanger human lives, but from a philosophical point of view, knowing them well is an effective way to better understand ourselves. So, this is why we study toxins. PMID:26228472

  10. Why do we study animal toxins?

    PubMed

    Zhang, Yun

    2015-07-18

    Venom (toxins) is an important trait evolved along the evolutionary tree of animals. Our knowledges on venoms, such as their origins and loss, the biological relevance and the coevolutionary patterns with other organisms are greatly helpful in understanding many fundamental biological questions, i.e., the environmental adaptation and survival competition, the evolution shaped development and balance of venoms, and the sophisticated correlations among venom, immunity, body power, intelligence, their genetic basis, inherent association, as well as the cost-benefit and trade-offs of biological economy. Lethal animal envenomation can be found worldwide. However, from foe to friend, toxin studies have led lots of important discoveries and exciting avenues in deciphering and fighting human diseases, including the works awarded the Nobel Prize and lots of key clinic therapeutics. According to our survey, so far, only less than 0.1% of the toxins of the venomous animals in China have been explored. We emphasize on the similarities shared by venom and immune systems, as well as the studies of toxin knowledge-based physiological toxin-like proteins/peptides (TLPs). We propose the natural pairing hypothesis. Evolution links toxins with humans. Our mission is to find out the right natural pairings and interactions of our body elements with toxins, and with endogenous toxin-like molecules. Although, in nature, toxins may endanger human lives, but from a philosophical point of view, knowing them well is an effective way to better understand ourselves. So, this is why we study toxins.

  11. Botulinum Toxin in Pediatric Neurology

    PubMed Central

    Abdallah, Enas Abdallah Ali

    2015-01-01

    Botulinum neurotoxins are natural molecules produced by anaerobic spore-forming bacteria called Clostradium boltulinum. The toxin has a peculiar mechanism of action by preventing the release of acetylcholine from the presynaptic membrane. Consequently, it has been used in the treatment of various neurological conditions related to muscle hyperactivity and/or spasticity. Also, it has an impact on the autonomic nervous system by acting on smooth muscle, leading to its use in the management of pain syndromes. The use of botulinum toxin in children separate from adults has received very little attention in the literature. This review presents the current data on the use of botulinum neurotoxin to treat various neurological disorders in children. PMID:27335961

  12. The toxin and antidote puzzle

    PubMed Central

    2011-01-01

    Insects carry out essential ecological functions, such as pollination, but also cause extensive damage to agricultural crops and transmit human diseases such as malaria and dengue fever. Advances in insect transgenesis are making it increasingly feasible to engineer genes conferring desirable phenotypes, and gene drive systems are required to spread these genes into wild populations. Medea provides one solution, being able to spread into a population from very low initial frequencies through the action of a maternally-expressed toxin linked to a zygotically-expressed antidote. Several other toxin-antidote combinations are imaginable that distort the offspring ratio in favor of a desired transgene, or drive the population towards an all-male crash. We explore two such systems—Semele, which is capable of spreading a desired transgene into an isolated population in a confined manner; and Merea, which is capable of inducing a local population crash when located on the Z chromosome of a Lepidopteron pest. PMID:21876382

  13. Reduced contribution of thermally-labile sugar lesions to DNA double-strand break formation after exposure to neutrons.

    PubMed

    Singh, Satyendra K; Wu, Wenqi; Stuschke, Martin; Bockisch, Andreas; Iliakis, George

    2012-12-01

    In cells exposed to ionizing radiation, double-strand breaks (DSBs) form within clustered damage sites from lesions disrupting the DNA sugar-phosphate backbone. It is commonly assumed that DSBs form promptly and are immediately detected and processed by the cellular DNA damage response apparatus. However, DSBs also form by delayed chemical conversion of thermally-labile sugar lesions (TLSL) to breaks. We recently reported that conversion of thermally-labile sugar lesions to breaks occurs in cells maintained at physiological temperatures. Here, we investigate the influence of radiation quality on the formation of thermally-labile sugar lesions dependent DSBs. We show that, although the yields of total DSBs are very similar after exposure to neutrons and X rays, the yields of thermally-labile sugar lesions dependent DSBs from neutrons are decreased in comparison to that from X rays. Thus, the yields of prompt DSBs for neutrons are greater than for X rays. Notably, after neutron irradiation the decreased yield of thermally-labile sugar lesion dependent DSBs is strongly cell line dependent, likely reflecting subtle differences in DNA organization. We propose that the higher ionization density of neutrons generates with higher probability prompt DSBs within ionization clusters and renders the ensuing chemical evolution of thermally-labile sugar lesions inconsequential to DNA integrity. Modification of thermally-labile sugar lesion evolution may define novel radiation protection strategies aiming at decreasing DSB formation by chemically preserving thermally-labile sugar lesions until other DSB contributing lesions within the clustered damage site are removed by non-DSB repair pathways. PMID:23088767

  14. Reduced contribution of thermally-labile sugar lesions to DNA double-strand break formation after exposure to neutrons.

    PubMed

    Singh, Satyendra K; Wu, Wenqi; Stuschke, Martin; Bockisch, Andreas; Iliakis, George

    2012-12-01

    In cells exposed to ionizing radiation, double-strand breaks (DSBs) form within clustered damage sites from lesions disrupting the DNA sugar-phosphate backbone. It is commonly assumed that DSBs form promptly and are immediately detected and processed by the cellular DNA damage response apparatus. However, DSBs also form by delayed chemical conversion of thermally-labile sugar lesions (TLSL) to breaks. We recently reported that conversion of thermally-labile sugar lesions to breaks occurs in cells maintained at physiological temperatures. Here, we investigate the influence of radiation quality on the formation of thermally-labile sugar lesions dependent DSBs. We show that, although the yields of total DSBs are very similar after exposure to neutrons and X rays, the yields of thermally-labile sugar lesions dependent DSBs from neutrons are decreased in comparison to that from X rays. Thus, the yields of prompt DSBs for neutrons are greater than for X rays. Notably, after neutron irradiation the decreased yield of thermally-labile sugar lesion dependent DSBs is strongly cell line dependent, likely reflecting subtle differences in DNA organization. We propose that the higher ionization density of neutrons generates with higher probability prompt DSBs within ionization clusters and renders the ensuing chemical evolution of thermally-labile sugar lesions inconsequential to DNA integrity. Modification of thermally-labile sugar lesion evolution may define novel radiation protection strategies aiming at decreasing DSB formation by chemically preserving thermally-labile sugar lesions until other DSB contributing lesions within the clustered damage site are removed by non-DSB repair pathways.

  15. The Stable and Radio- Carbon Isotopic Content of Labile and Refractory Carbon in Atmospheric Particulate Matter

    NASA Astrophysics Data System (ADS)

    McNichol, A. P.; Rosenheim, B. E.; Gerlach, D. S.; Hayes, J. M.

    2006-12-01

    Studies of the isotopic content of atmospheric particulate matter are hampered by difficulties in chemically defining the pools of carbon and analytically isolating the different pools. We are conducting studies on reference materials and atmospheric aerosol samples to develop a method to measure stable and radio- carbon isotopes on the labile and refractory carbon. We are using a flow-through combustion system that allows us to combust, collect and measure the isotopic content of the gases produced at all stages of heating/oxidizing. We compare our results to those measured using a chemothermal oxidation method (CTO) (Gustafsson et al., 2001). In this method, refractory carbon is defined as the material remaining after pre- combusting a sample at 375°C in the presence of oxygen for 24 hours. The reference materials are diesel soot, apple leaves and a hybrid of the two (DiesApple), all from NIST. These provide carbon with two well-defined fractions -- the soot provides refractory carbon that is radiocarbon dead and the apple leaves provide organic carbon that is radiocarbon modern. Radiocarbon results from DiesApple indicate that the "refractory" carbon defined by the CTO method is actually a mixture of old and modern carbon that contains over 25% modern carbon. This suggests that charred material formed from the apples leaves during the pre-combustion step is contributing to the fraction we identify as refractory carbon. We are studying this by analyzing the individual materials and the mixture using our flow-through system. First results with this system indicate that the refractory fraction trapped from the DiesApple contains much less modern carbon than the CTO method, less than 7%. We will present detailed concentration and isotopic results of the generation of carbon dioxide during programmed combustion of each of the reference materials. We studied the radiocarbon content of both the total carbon (TC) and refractory carbon in the fine particulate matter (PM

  16. Novel Class of Spider Toxin

    PubMed Central

    Vassilevski, Alexander A.; Fedorova, Irina M.; Maleeva, Ekaterina E.; Korolkova, Yuliya V.; Efimova, Svetlana S.; Samsonova, Olga V.; Schagina, Ludmila V.; Feofanov, Alexei V.; Magazanik, Lev G.; Grishin, Eugene V.

    2010-01-01

    Venom of the yellow sac spider Cheiracanthium punctorium (Miturgidae) was found unique in terms of molecular composition. Its principal toxic component CpTx 1 (15.1 kDa) was purified, and its full amino acid sequence (134 residues) was established by protein chemistry and mass spectrometry techniques. CpTx 1 represents a novel class of spider toxin with modular architecture. It consists of two different yet homologous domains (modules) each containing a putative inhibitor cystine knot motif, characteristic of the widespread single domain spider neurotoxins. Venom gland cDNA sequencing provided precursor protein (prepropeptide) structures of three CpTx 1 isoforms (a–c) that differ by single residue substitutions. The toxin possesses potent insecticidal (paralytic and lethal), cytotoxic, and membrane-damaging activities. In both fly and frog neuromuscular preparations, it causes stable and irreversible depolarization of muscle fibers leading to contracture. This effect appears to be receptor-independent and is inhibited by high concentrations of divalent cations. CpTx 1 lyses cell membranes, as visualized by confocal microscopy, and destabilizes artificial membranes in a manner reminiscent of other membrane-active peptides by causing numerous defects of variable conductance and leading to bilayer rupture. The newly discovered class of modular polypeptides enhances our knowledge of the toxin universe. PMID:20657014

  17. Emetic toxin-producing strains of Bacillus cereus show distinct characteristics within the Bacillus cereus group.

    PubMed

    Carlin, Frédéric; Fricker, Martina; Pielaat, Annemarie; Heisterkamp, Simon; Shaheen, Ranad; Salonen, Mirja Salkinoja; Svensson, Birgitta; Nguyen-the, Christophe; Ehling-Schulz, Monika

    2006-05-25

    One hundred representative strains of Bacillus cereus were selected from a total collection of 372 B. cereus strains using two typing methods (RAPD and FT-IR) to investigate if emetic toxin-producing hazardous B. cereus strains possess characteristic growth and heat resistance profiles. The strains were classified into three groups: emetic toxin (cereulide)-producing strains (n=17), strains connected to diarrheal foodborne outbreaks (n=40) and food-environment strains (n=43), these latter not producing the emetic toxin. Our study revealed a shift in growth limits towards higher temperatures for the emetic strains, regardless of their origin. None of the emetic toxin-producing strains were able to grow below 10 degrees Celsius. In contrast, 11% (9 food-environment strains) out of the 83 non-emetic toxin-producing strains were able to grow at 4 degrees Celsius and 49% at 7 degrees Celsius (28 diarrheal and 13 food-environment strains). non-emetic toxin-producing strains. All emetic toxin-producing strains were able to grow at 48 degrees Celsius, but only 39% (16 diarrheal and 16 food-environment strains) of the non-emetic toxin-producing strains grew at this temperature. Spores from the emetic toxin-producing strains showed, on average, a higher heat resistance at 90 degrees Celsius and a lower germination, particularly at 7 degrees Celsius, than spores from the other strains. No difference between the three groups in their growth kinetics at 24 degrees Celsius, 37 degrees Celsius, and pH 5.0, 7.0, and 8.0 was observed. Our survey shows that emetic toxin-producing strains of B. cereus have distinct characteristics, which could have important implication for the risk assessment of the emetic type of B. cereus caused food poisoning. For instance, emetic strains still represent a special risk in heat-processed foods or preheated foods that are kept warm (in restaurants and cafeterias), but should not pose a risk in refrigerated foods. PMID:16503068

  18. Bacterial protein toxins in human cancers.

    PubMed

    Rosadi, Francesca; Fiorentini, Carla; Fabbri, Alessia

    2016-02-01

    Many bacteria causing persistent infections produce toxins whose mechanisms of action indicate that they could have a role in carcinogenesis. Some toxins, like CDT and colibactin, directly attack the genome by damaging DNA whereas others, as for example CNF1, CagA and BFT, impinge on key eukaryotic processes, such as cellular signalling and cell death. These bacterial toxins, together with other less known toxins, mimic carcinogens and tumour promoters. The aim of this review is to fulfil an up-to-date analysis of toxins with carcinogenic potential that have been already correlated to human cancers. Bacterial toxins-induced carcinogenesis represents an emerging aspect in bacteriology, and its significance is increasingly recognized.

  19. Bt Toxin Modification for Enhanced Efficacy

    PubMed Central

    Deist, Benjamin R.; Rausch, Michael A.; Fernandez-Luna, Maria Teresa; Adang, Michael J.; Bonning, Bryony C.

    2014-01-01

    Insect-specific toxins derived from Bacillus thuringiensis (Bt) provide a valuable resource for pest suppression. Here we review the different strategies that have been employed to enhance toxicity against specific target species including those that have evolved resistance to Bt, or to modify the host range of Bt crystal (Cry) and cytolytic (Cyt) toxins. These strategies include toxin truncation, modification of protease cleavage sites, domain swapping, site-directed mutagenesis, peptide addition, and phage display screens for mutated toxins with enhanced activity. Toxin optimization provides a useful approach to extend the utility of these proteins for suppression of pests that exhibit low susceptibility to native Bt toxins, and to overcome field resistance. PMID:25340556

  20. Modeling of toxin-antibody interaction and toxin transport toward the endoplasmic reticulum.

    PubMed

    Skakauskas, Vladas; Katauskis, Pranas

    2016-01-01

    A model for toxin-antibody interaction and toxin trafficking towards the endoplasmic-reticulum is presented. Antibody and toxin (ricin) initially are delivered outside the cell. The model involves: the pinocytotic (cellular drinking) and receptor-mediated toxin internalization modes from the extracellular into the intracellular domain, its exocytotic excretion from the cytosol back to the extracellular medium, the intact toxin retrograde transport to the endoplasmic reticulum, the anterograde toxin movement outward from the cell across the plasma membrane, the lysosomal toxin degradation, and the toxin clearance (removal from the system) flux. The model consists of a set of coupled PDEs. Using an averaging procedure, the model is reduced to a system of coupled ODEs. Both PDEs and ODEs systems are solved numerically. Numerical results are illustrated by figures and discussed.

  1. Characterization of Shiga Toxin Subtypes and Virulence Genes in Porcine Shiga Toxin-Producing Escherichia coli.

    PubMed

    Baranzoni, Gian Marco; Fratamico, Pina M; Gangiredla, Jayanthi; Patel, Isha; Bagi, Lori K; Delannoy, Sabine; Fach, Patrick; Boccia, Federica; Anastasio, Aniello; Pepe, Tiziana

    2016-01-01

    Similar to ruminants, swine have been shown to be a reservoir for Shiga toxin-producing Escherichia coli (STEC), and pork products have been linked with outbreaks associated with STEC O157 and O111:H-. STEC strains, isolated in a previous study from fecal samples of late-finisher pigs, belonged to a total of 56 serotypes, including O15:H27, O91:H14, and other serogroups previously associated with human illness. The isolates were tested by polymerase chain reaction (PCR) and a high-throughput real-time PCR system to determine the Shiga toxin (Stx) subtype and virulence-associated and putative virulence-associated genes they carried. Select STEC strains were further analyzed using a Minimal Signature E. coli Array Strip. As expected, stx 2e (81%) was the most common Stx variant, followed by stx 1a (14%), stx 2d (3%), and stx 1c (1%). The STEC serogroups that carried stx 2d were O15:H27, O159:H16 and O159:H-. Similar to stx 2a and stx 2c, the stx 2d variant is associated with development of hemorrhagic colitis and hemolytic uremic syndrome, and reports on the presence of this variant in STEC strains isolated from swine are lacking. Moreover, the genes encoding heat stable toxin (estIa) and enteroaggregative E. coli heat stable enterotoxin-1 (astA) were commonly found in 50 and 44% of isolates, respectively. The hemolysin genes, hlyA and ehxA, were both detected in 7% of the swine STEC strains. Although the eae gene was not found, other genes involved in host cell adhesion, including lpfAO113 and paa were detected in more than 50% of swine STEC strains, and a number of strains also carried iha, lpfAO26, lpfAO157, fedA, orfA, and orfB. The present work provides new insights on the distribution of virulence factors among swine STEC strains and shows that swine may carry Stx1a-, Stx2e-, or Stx2d-producing E. coli with virulence gene profiles associated with human infections. PMID:27148249

  2. Characterization of Shiga toxin subtypes and virulence genes in porcine Shiga toxin-producing Escherichia coli

    DOE PAGES

    Baranzoni, Gian Marco; Fratamico, Pina M.; Gangiredla, Jayanthi; Patel, Isha; Bagi, Lori K.; Delannoy, Sabine; Fach, Patrick; Boccia, Federica; Anastasio, Aniello; Pepe, Tiziana

    2016-04-21

    Similar to ruminants, swine have been shown to be a reservoir for Shiga toxin-producing Escherichia coli (STEC), and pork products have been linked with outbreaks associated with STEC O157 and O111:H-. STEC strains, isolated in a previous study from fecal samples of late-finisher pigs, belonged to a total of 56 serotypes, including O15:H27, O91:H14, and other serogroups previously associated with human illness. The isolates were tested by polymerase chain reaction (PCR) and a high-throughput real-time PCR system to determine the Shiga toxin (Stx) subtype and virulence-associated and putative virulence-associated genes they carried. Select STEC strains were further analyzed using amore » Minimal Signature E. coli Array Strip. As expected, stx2e (81%) was the most common Stx variant, followed by stx1a (14%), stx2d (3%), and stx1c (1%). The STEC serogroups that carried stx2d were O15:H27, O159:H16 and O159:H-. Similar to stx2a and stx2c, the stx2d variant is associated with development of hemorrhagic colitis and hemolytic uremic syndrome, and reports on the presence of this variant in STEC strains isolated from swine are lacking. Moreover, the genes encoding heat stable toxin (estIa) and enteroaggregative E. coli heat stable enterotoxin-1 (astA) were commonly found in 50 and 44% of isolates, respectively. The hemolysin genes, hlyA and ehxA, were both detected in 7% of the swine STEC strains. Although the eae gene was not found, other genes involved in host cell adhesion, including lpfAO113 and paa were detected in more than 50% of swine STEC strains, and a number of strains also carried iha, lpfAO26, lpfAO157, fedA, orfA, and orfB. Furthermore, the present work provides new insights on the distribution of virulence factors among swine STEC strains and shows that swine may carry Stx1a-, Stx2e-, or Stx2d-producing E. coli with virulence gene profiles associated with human infections.« less

  3. Characterization of Shiga Toxin Subtypes and Virulence Genes in Porcine Shiga Toxin-Producing Escherichia coli

    PubMed Central

    Baranzoni, Gian Marco; Fratamico, Pina M.; Gangiredla, Jayanthi; Patel, Isha; Bagi, Lori K.; Delannoy, Sabine; Fach, Patrick; Boccia, Federica; Anastasio, Aniello; Pepe, Tiziana

    2016-01-01

    Similar to ruminants, swine have been shown to be a reservoir for Shiga toxin-producing Escherichia coli (STEC), and pork products have been linked with outbreaks associated with STEC O157 and O111:H-. STEC strains, isolated in a previous study from fecal samples of late-finisher pigs, belonged to a total of 56 serotypes, including O15:H27, O91:H14, and other serogroups previously associated with human illness. The isolates were tested by polymerase chain reaction (PCR) and a high-throughput real-time PCR system to determine the Shiga toxin (Stx) subtype and virulence-associated and putative virulence-associated genes they carried. Select STEC strains were further analyzed using a Minimal Signature E. coli Array Strip. As expected, stx2e (81%) was the most common Stx variant, followed by stx1a (14%), stx2d (3%), and stx1c (1%). The STEC serogroups that carried stx2d were O15:H27, O159:H16 and O159:H-. Similar to stx2a and stx2c, the stx2d variant is associated with development of hemorrhagic colitis and hemolytic uremic syndrome, and reports on the presence of this variant in STEC strains isolated from swine are lacking. Moreover, the genes encoding heat stable toxin (estIa) and enteroaggregative E. coli heat stable enterotoxin-1 (astA) were commonly found in 50 and 44% of isolates, respectively. The hemolysin genes, hlyA and ehxA, were both detected in 7% of the swine STEC strains. Although the eae gene was not found, other genes involved in host cell adhesion, including lpfAO113 and paa were detected in more than 50% of swine STEC strains, and a number of strains also carried iha, lpfAO26, lpfAO157, fedA, orfA, and orfB. The present work provides new insights on the distribution of virulence factors among swine STEC strains and shows that swine may carry Stx1a-, Stx2e-, or Stx2d-producing E. coli with virulence gene profiles associated with human infections. PMID:27148249

  4. Rho-modifying bacterial protein toxins.

    PubMed

    Aktories, Klaus

    2015-12-01

    Rho proteins are targets of numerous bacterial protein toxins, which manipulate the GTP-binding proteins by covalent modifications, including ADP ribosylation, glycosylation, adenylylation, proteolytic cleavage and deamidation. Bacterial toxins are important virulence factors but are also potent and efficient pharmacological tools to study the physiological functions of their eukaryotic targets. Recent studies indicate that amazing variations exist in the molecular mechanisms by which toxins attack Rho proteins, which are discussed here.

  5. Geldanamycin Enhances Retrograde Transport of Shiga Toxin in HEp-2 Cells

    PubMed Central

    Simm, Roger; Torgersen, Maria Lyngaas; Sandvig, Kirsten

    2015-01-01

    The heat shock protein 90 (Hsp90) inhibitor geldanamycin (GA) has been shown to alter endosomal sorting, diverting cargo destined for the recycling pathway into the lysosomal pathway. Here we investigated whether GA also affects the sorting of cargo into the retrograde pathway from endosomes to the Golgi apparatus. As a model cargo we used the bacterial toxin Shiga toxin, which exploits the retrograde pathway as an entry route to the cytosol. Indeed, GA treatment of HEp-2 cells strongly increased the Shiga toxin transport to the Golgi apparatus. The enhanced Golgi transport was not due to increased endocytic uptake of the toxin or perturbed recycling, suggesting that GA selectively enhances endosomal sorting into the retrograde pathway. Moreover, GA activated p38 and both inhibitors of p38 or its substrate MK2 partially counteracted the GA-induced increase in Shiga toxin transport. Thus, our data suggest that GA-induced p38 and MK2 activation participate in the increased Shiga toxin transport to the Golgi apparatus. PMID:26017782

  6. Application of botulinum toxin in pain management.

    PubMed

    Sim, Woo Seog

    2011-03-01

    Botulinum toxin has been used for the treatment of many clinical disorders by producing temporary skeletal muscle relaxation. In pain management, botulinum toxin has demonstrated an analgesic effect by reducing muscular hyperactivity, but recent studies suggest this neurotoxin could have direct analgesic mechanisms different from its neuromuscular actions. At the moment, botulinum toxin is widely investigated and used in many painful diseases such as myofascial syndrome, headaches, arthritis, and neuropathic pain. Further studies are needed to understand the exact analgesic mechanisms, efficacy and complications of botulinum toxin in chronic pain disorders.

  7. Adaptive evolution of animal toxin multigene families.

    PubMed

    Kordis, D; Gubensek, F

    2000-12-30

    Animal toxins comprise a diverse array of proteins that have a variety of biochemical and pharmacological functions. A large number of animal toxins are encoded by multigene families. From studies of several toxin multigene families at the gene level the picture is emerging that most have been functionally diversified by gene duplication and adaptive evolution. The number of pharmacological activities in most toxin multigene families results from their adaptive evolution. The molecular evolution of animal toxins has been analysed in some multigene families, at both the intraspecies and interspecies levels. In most toxin multigene families, the rate of non-synonymous to synonymous substitutions (dN/dS) is higher than one. Thus natural selection has acted to diversify coding sequences and consequently the toxin functions. The selection pressure for the rapid adaptive evolution of animal toxins is the need for quick immobilization of the prey in classical predator and prey interactions. Currently available evidence for adaptive evolution in animal toxin multigene families will be considered in this review.

  8. [Cervical dystonia treatment with botulin toxin].

    PubMed

    Cervical Dystonia Treatment With Botulin Toxin, Kazimierz

    2016-08-01

    Cervical dystonia is the most common form of dystonia in adult age. It is characterized by involuntary muscle contractions that cause abnormal movements and positioning of the head and neck. Symptoms of it are often associated with pain. This distinguishes this form from other dystonia. The drug of choice is botulinum toxin. It effectively reduces both pain and abnormal excessive muscle activity. In some cases, particularly where there is not obtained the full recovery after treatment botulinum toxin we used drugs for systemic effect. To increase the effectiveness and reduce the side effects of botulinum toxin more commonly we used administration of toxin under the EMG and ultrasound control. PMID:27591450

  9. [Cervical dystonia treatment with botulin toxin].

    PubMed

    Cervical Dystonia Treatment With Botulin Toxin, Kazimierz

    2016-07-01

    Cervical dystonia is the most common form of dystonia in adult age. It is characterized by involuntary muscle contractions that cause abnormal movements and positioning of the head and neck. Symptoms of it are often associated with pain. This distinguishes this form from other dystonia. The drug of choice is botulinum toxin. It effectively reduces both pain and abnormal excessive muscle activity. In some cases, particularly where there is not obtained the full recovery after treatment botulinum toxin we used drugs for systemic effect. To increase the effectiveness and reduce the side effects of botulinum toxin more commonly we used administration of toxin under the EMG and ultrasound control. PMID:27590655

  10. Labile Low-Molecular-Mass Metal Complexes in Mitochondria: Trials and Tribulations of a Burgeoning Field.

    PubMed

    Lindahl, Paul A; Moore, Michael J

    2016-08-01

    Iron, copper, zinc, manganese, cobalt, and molybdenum play important roles in mitochondrial biochemistry, serving to help catalyze reactions in numerous metalloenzymes. These metals are also found in labile "pools" within mitochondria. Although the composition and cellular function of these pools are largely unknown, they are thought to be comprised of nonproteinaceous low-molecular-mass (LMM) metal complexes. Many problems must be solved before these pools can be fully defined, especially problems stemming from the lability of such complexes. This lability arises from inherently weak coordinate bonds between ligands and metals. This is an advantage for catalysis and trafficking, but it makes characterization difficult. The most popular strategy for investigating such pools is to detect them using chelator probes with fluorescent properties that change upon metal coordination. Characterization is limited because of the inevitable destruction of the complexes during their detection. Moreover, probes likely react with more than one type of metal complex, confusing analyses. An alternative approach is to use liquid chromatography (LC) coupled with inductively coupled plasma mass spectrometry (ICP-MS). With help from a previous lab member, the authors recently developed an LC-ICP-MS approach to analyze LMM extracts from yeast and mammalian mitochondria. They detected several metal complexes, including Fe580, Fe1100, Fe1500, Cu5000, Zn1200, Zn1500, Mn1100, Mn2000, Co1200, Co1500, and Mo780 (numbers refer to approximate masses in daltons). Many of these may be used to metalate apo-metalloproteins as they fold inside the organelle. The LC-based approach also has challenges, e.g., in distinguishing artifactual metal complexes from endogenous ones, due to the fact that cells must be disrupted to form extracts before they are passed through chromatography columns prior to analysis. Ultimately, both approaches will be needed to characterize these intriguing complexes and to

  11. Interactions between recalcitrant and labile organic carbon in streams - Can stream biofilms mediate a priming effect?

    NASA Astrophysics Data System (ADS)

    Bengtsson, M. M.; Wagner, K.; Herberg, E. R.; Burns, N. R.; Wanek, W.; Battin, T. J.

    2012-04-01

    Inland waters - such as streams, rivers and lakes - are increasingly recognized as important components in the global carbon cycle. Dissolved organic carbon (DOC) in these systems is diverse in structure, origin and reactivity, and a fraction of it is regarded as recalcitrant to microbial degradation. In soils, degradation of recalcitrant carbon is often controlled by the availability of labile carbon sources. This is linked to the priming effect (PE). Mounting evidence suggests that PE is also important in aquatic ecosystems but there are so far very few studies addressing this topic. Biofilms are vital components of aquatic ecosystems. In stream biofilms, heterotrophic bacteria and algae coexist in close proximity, exposing the bacteria to both recalcitrant DOC of terrestrial origin and labile organic carbon from the algae. We hypothesize that this makes stream biofilms hotspots for PE. We used plug-flow bioreactors inoculated with natural stream biofilm bacterial communities to test the potential of a priming effect in aquatic ecosystems. The bioreactors were amended with an isotope-labeled plant extract serving as a model of recalcitrant DOC in streams. Labile carbon sources, in the form of glucose and an algal extract were added to induce PE. Nitrate and phosphate were also added to assess the role of these inorganic nutrients on carbon uptake. Microbial uptake of the different carbon sources was monitored by measuring the concentrations and isotopic ratios of respired CO2, biomass and DOC. Our results suggest that the priming effect plays a role in stream carbon cycling and that it is potentially an important process in other aquatic ecosystems.

  12. Total and Labile Phosphorus Concentrations as Influenced by Riparian Buffer Soil Properties.

    PubMed

    Young, Eric O; Ross, Donald S

    2016-01-01

    Riparian buffers can act as a phosphorus (P) source under active stream bank erosion. Using soil and landscape variables (soil series, drainage class, organic matter, and pH) to index P concentrations could improve P loss risk tools for buffers. The objectives of this study were (i) to determine if soil properties could predict total and labile P concentrations within a 10-ha riparian buffer and (ii) to quantify the degree of spatial dependence of P and related properties. Soil samples were taken in 15-cm increments to a depth of 60 cm using a grid ( = 71) from an established riparian buffer along the Rock River in Vermont. Total soil P (TP), plant-available P determined by Modified Morgan extraction (MM-P), pH, soil organic matter (SOM), soil texture, and select cations were measured. We found that TP (152-1536 mg P kg) and MM-P (0.4-14.6 mg kg) ranged widely, with distinct differences between soil series. Mean TP and MM-P were greater in alluvial and glaciolacustrine soils compared with glacial till. Across all samples, MM-P was weakly related to soil properties; however, total labile P (orthophosphate + organic P measured by ICP) and unreactive labile P (ICP-P - colorimetric-P) could both be predicted by SOM ( = 0.59 and 0.73, respectively). Strong spatial dependence was found for P and related properties as revealed by geospatial analyses. Results show that P availability in the buffer was strongly related to soil genesis and support site-specific approaches for P loss risk evaluation in buffers.

  13. Core-Shell Hydrogel Particles Harvest, Concentrate and Preserve Labile Low Abundance Biomarkers

    PubMed Central

    Longo, Caterina; Patanarut, Alexis; George, Tony; Bishop, Barney; Zhou, Weidong; Fredolini, Claudia; Ross, Mark M.; Espina, Virginia; Pellacani, Giovanni; Petricoin, Emanuel F.; Liotta, Lance A.; Luchini, Alessandra

    2009-01-01

    Background The blood proteome is thought to represent a rich source of biomarkers for early stage disease detection. Nevertheless, three major challenges have hindered biomarker discovery: a) candidate biomarkers exist at extremely low concentrations in blood; b) high abundance resident proteins such as albumin mask the rare biomarkers; c) biomarkers are rapidly degraded by endogenous and exogenous proteinases. Methodology and Principal Findings Hydrogel nanoparticles created with a N-isopropylacrylamide based core (365 nm)-shell (167 nm) and functionalized with a charged based bait (acrylic acid) were studied as a technology for addressing all these biomarker discovery problems, in one step, in solution. These harvesting core-shell nanoparticles are designed to simultaneously conduct size exclusion and affinity chromatography in solution. Platelet derived growth factor (PDGF), a clinically relevant, highly labile, and very low abundance biomarker, was chosen as a model. PDGF, spiked in human serum, was completely sequestered from its carrier protein albumin, concentrated, and fully preserved, within minutes by the particles. Particle sequestered PDGF was fully protected from exogenously added tryptic degradation. When the nanoparticles were added to a 1 mL dilute solution of PDGF at non detectable levels (less than 20 picograms per mL) the concentration of the PDGF released from the polymeric matrix of the particles increased within the detection range of ELISA and mass spectrometry. Beyond PDGF, the sequestration and protection from degradation for a series of additional very low abundance and very labile cytokines were verified. Conclusions and Significance We envision the application of harvesting core-shell nanoparticles to whole blood for concentration and immediate preservation of low abundance and labile analytes at the time of venipuncture. PMID:19274087

  14. Enantiomeric Excesses of Acid Labile Amino Acid Precursors of the Murchison Meteorite

    NASA Technical Reports Server (NTRS)

    Pizzarello, Sandra

    1998-01-01

    Amino acids present in carbonaceous chondrite are extracted in water in part as free compounds and in approximately equal part as acid labile precursors. On the assumption that they would be free of contamination, the precursors of two Murchison amino acids that have terrestrial occurrence, alanine and glutamic acid, have been targeted for analysis of their enantiomeric ratios. Pyroglutamic acid, the precursor of glutamic acid, was found with an L-enantiomeric excess comparable to that of the free acid, while alanine's precursor, N-acetyl alanine, appears approximately racemic. Also alpha-imino propioacetic acid, a proposed end product of alanine synthesis in the meteorite, was analyzed and found racemic.

  15. Labile Compounds in Plant Litter Reduce the Sensitivity of Decomposition to Warming and Altered Precipitation

    NASA Astrophysics Data System (ADS)

    Suseela, V.; Tharayil, N.; Xing, B.; Dukes, J. S.

    2013-12-01

    Together, climate and litter quality strongly regulate decomposition rates. While these two factors and their interaction have been studied across species in continent-scale experiments, few researchers have studied how labile and recalcitrant compounds interact to influence decomposition, or the climate sensitivity of decomposition, within a litter type. Over a period of three years, we studied the effects climate change on mass loss and compound-specific decomposition using two litter types that differed in the relative proportions of labile and recalcitrant compounds, but that had heteropolymers with similar molecular structure. We examined how warming and altered precipitation affected the decomposition of two types of Polygonum cuspidatum (Japanese knotweed) litter (stem litter that was either newly senesced or one year old), at the Boston-Area Climate Experiment (BACE), in Massachusetts, USA. We placed litter bags in an old-field ecosystem exposed to four levels of warming (up to 4oC) and three levels of precipitation (ambient, drought (-50%) and wet (+50%) treatments. The compound-specific degradation of litter was assessed using Diffuse Reflectance Infrared Fourier Transform Spectroscopy and 13C Nuclear Magnetic Resonance Spectroscopy. Climate treatments immediately affected mass loss of the more recalcitrant litter, but affected the more labile litter only after two years. After three years, although both litter types had lost similar amounts of mass, warming (~4oC) and supplemental precipitation (150% of ambient) together accelerated degradation of alkyl-carbon and lignin only in the more recalcitrant litter, highlighting the role of initial litter quality in determining whether the chemistry of litter residues converges or diverges under different climates. The results from this study indicate that the effect of climate on litter decomposition depends on the quality of litter; litter with a greater initial proportion of labile compounds was less

  16. Organic chemistry of basal ice - presence of labile, low molecular weight compounds available for microbial metabolism

    NASA Astrophysics Data System (ADS)

    Lis, Grzegorz P.; Wadham, Jemma L.; Lawson, Emily; Stibal, Marek; Telling, Jon

    2010-05-01

    Recent studies show that subglacial environments previously thought to be devoid of life contain a host of active microbial organisms. Presence of liquid water due to overburden pressure, the release of nutrients from chemical erosion of bedrock, and the potential carbon sources in overridden sediments facilitate life in this extreme environment. However, little is still known of concentrations and diversity of labile organic compounds essential for sustaining microbial metabolism in subglacial environments. Three subglacial ecosystems that considerably differ in range and amount of available organic compounds were selected for this study 1-Engabreen, northern Norway, overlying high-grade metamorphic rocks with low organic carbon content; 2-Finsterwalderbreen, Svalbard, overriding ancient black shales with a relatively high carbon content yet recalcitrant to microbiological consumption; and 3-Russell Glacier in western Greenland with recently overridden quaternary organic rich paleosols. Basal and pressure ridge ice samples were collected and subsequently analysed for low molecular weight organic compounds, with the emphasis on volatile fatty acids, carbohydrates and amino acids. The highest concentration of labile organic compounds in Greenland basal ice suggest that recently overridden paleosols have the greatest potential for sustaining microbial populations present within and underneath basal ice. The high concentration of "ancient" organic carbon in basal ice from Finsterwalderbreen, Svalbard, doesn't correlate with the presence of labile organic compounds. This indicates the inability of microbes to digest recalcitrant kerogen carbon in cold temperatures. In all three investigated environments, concentrations of labile organic compounds are elevated in basal ice with a high debris content. Until recently, most models of the global carbon cycle tend to neglect the pool of subglacial organic carbon as little is known about the range and concentrations of

  17. Dissolved organic carbon lability increases with water residence time in the alluvial aquifer of a river floodplain ecosystem

    NASA Astrophysics Data System (ADS)

    Helton, Ashley M.; Wright, Meredith S.; Bernhardt, Emily S.; Poole, Geoffrey C.; Cory, Rose M.; Stanford, Jack A.

    2015-04-01

    We assessed spatial and temporal patterns of dissolved organic carbon (DOC) lability and composition throughout the alluvial aquifer of the 16 km2 Nyack Floodplain in northwest Montana, USA. Water influx to the aquifer derives almost exclusively from the Middle Fork of the Flathead River, and water residence times within the aquifer range from days to months. Across seasons and channel discharge conditions, we measured DOC concentration, lability, and optical properties of aquifer water sampled from 12 wells, both near and ~3 m below the water table. Concentrations of DOC were typically low (542 ± 22.7 µg L-1; mean ± se), and the percentage of labile DOC averaged 18 ± 12% during 3 day laboratory assays. Parallel factor analysis of fluorescence excitation-emission matrices revealed two humic-like and two amino acid-like fluorescence groups. Total DOC, humic-like components, and specific UV absorbance decreased with water residence time, consistent with sorption to aquifer sediments. However, labile DOC (both concentration and fraction) increased with water residence time, suggesting a concurrent influx or production of labile DOC. Thus, although the carbon-poor, oxygen-rich aquifer is a net sink for DOC, recalcitrant DOC appears to be replaced with more labile DOC along aquifer flow paths. Our observation of DOC production in long flow paths contrasts with studies of hyporheic DOC consumption along short (centimeters to meters) flow paths and highlights the importance of understanding the role of labile organic matter production and/or influx in alluvial aquifer carbon cycling.

  18. Biologic response to environmental toxins

    SciTech Connect

    Lerner, S.

    1983-12-01

    Biological response to environmental toxins results from the sum of natural, environmental, avocational, inapparent, and occupational exposures. These external exposures result in acceptable or unacceptable levels of absorption or internal exposure based on anticipated biological effects. There is no level of exposure which is in and of itself synonymous with intoxication. Biological effects may be classified as physiologic or pathologic, adaptive or nonadaptive, respectively. In each instance, the response may be acceptable or unacceptable. Intoxication requires the demonstration of a significant impairment of health. One may have an unacceptable pathologic response and still not have intoxication. Professional judgment is required.

  19. Designing Inhibitors of Anthrax Toxin

    PubMed Central

    Nestorovich, Ekaterina M.; Bezrukov, Sergey M.

    2014-01-01

    Introduction Present-day rational drug design approaches are based on exploiting unique features of the target biomolecules, small- or macromolecule drug candidates, and physical forces that govern their interactions. The 2013 Nobel Prize in chemistry awarded “for the development of multiscale models for complex chemical systems” once again demonstrated the importance of the tailored drug discovery that reduces the role of the trial and error approach to a minimum. The “rational drug design” term is rather comprehensive as it includes all contemporary methods of drug discovery where serendipity and screening are substituted by the information-guided search for new and existing compounds. Successful implementation of these innovative drug discovery approaches is inevitably preceded by learning the physics, chemistry, and physiology of functioning of biological structures under normal and pathological conditions. Areas covered This article provides an overview of the recent rational drug design approaches to discover inhibitors of anthrax toxin. Some of the examples include small-molecule and peptide-based post-exposure therapeutic agents as well as several polyvalent compounds. The review also directs the reader to the vast literature on the recognized advances and future possibilities in the field. Expert opinion Existing options to combat anthrax toxin lethality are limited. With the only anthrax toxin inhibiting therapy (PA-targeting with a monoclonal antibody, raxibacumab) approved to treat inhalational anthrax, in our view, the situation is still insecure. The FDA’s animal rule for drug approval, which clears compounds without validated efficacy studies on humans, creates a high level of uncertainty, especially when a well-characterized animal model does not exist. Besides, unlike PA, which is known to be unstable, LF remains active in cells and in animal tissues for days. Therefore, the effectiveness of the post-exposure treatment of the individuals

  20. Tremorgenic toxin from Penicillium veruculosum.

    PubMed

    Cole, R J; Kirksey, J W; Moore, J H; Blankenship, B R; Diener, U L; Davis, N D

    1972-08-01

    A new mycotoxin that produces severe tremors and acute toxicity when administered orally or intraperitoneally (ip) to mice and 1-day-old cockerels was obtained from a strain of Penicillium verruculosum Peyronel isolated from peanuts. The ip 50% lethal dose (LD(50)) of this tremorgen was 2.4 mg/kg in mice and 15.2 mg/kg in chickens. Orally administered LD(50) values for the toxin were 126.7 mg/kg in mice and 365.5 mg/kg in chickens. The trivial name "verruculogen" is proposed for this tremorgenic mycotoxin. Physical and chemical characteristics of the mycotoxin are described. PMID:4341967

  1. Tremorgenic Toxin from Penicillium verruculosum

    PubMed Central

    Cole, R. J.; Kirksey, J. W.; Moore, J. H.; Blankenship, B. R.; Diener, U. L.; Davis, N. D.

    1972-01-01

    A new mycotoxin that produces severe tremors and acute toxicity when administered orally or intraperitoneally (ip) to mice and 1-day-old cockerels was obtained from a strain of Penicillium verruculosum Peyronel isolated from peanuts. The ip 50% lethal dose (LD50) of this tremorgen was 2.4 mg/kg in mice and 15.2 mg/kg in chickens. Orally administered LD50 values for the toxin were 126.7 mg/kg in mice and 365.5 mg/kg in chickens. The trivial name „verruculogen” is proposed for this tremorgenic mycotoxin. Physical and chemical characteristics of the mycotoxin are described. PMID:4341967

  2. Synthesis and biology of cyclic imine toxins, an emerging class of potent, globally distributed marine toxins.

    PubMed

    Stivala, Craig E; Benoit, Evelyne; Aráoz, Rómulo; Servent, Denis; Novikov, Alexei; Molgó, Jordi; Zakarian, Armen

    2015-03-01

    From a small group of exotic compounds isolated only two decades ago, Cyclic Imine (CI) toxins have become a major class of marine toxins with global distribution. Their distinct chemical structure, biological mechanism of action, and intricate chemistry ensures that CI toxins will continue to be the subject of fascinating fundamental studies in the broad fields of chemistry, chemical biology, and toxicology. The worldwide occurrence of potent CI toxins in marine environments, their accumulation in shellfish, and chemical stability are important considerations in assessing risk factors for human health. This review article aims to provide an account of chemistry, biology, and toxicology of CI toxins from their discovery to the present day.

  3. Multifunctional-autoprocessing repeats-in-toxin (MARTX) Toxins of Vibrios.

    PubMed

    Satchell, Karla J F

    2015-06-01

    Multifunctional-autoprocessing repeats-in-toxin (MARTX) toxins are a heterogeneous group of toxins found in a number of Vibrio species and other Gram-negative bacteria. The toxins are composed of conserved repeat regions and an autoprocessing protease domain that together function as a delivery platform for transfer of cytotoxic and cytopathic domains into target eukaryotic cell cytosol. Within the cells, the effectors can alter biological processes such as signaling or cytoskeletal structure, presumably to the benefit of the bacterium. Ten effector domains are found in the various Vibrio MARTX toxins, although any one toxin carries only two to five effector domains. The specific toxin variant expressed by a species can be modified by homologous recombination to acquire or lose effector domains, such that different strains within the same species can express distinct variants of the toxins. This review examines the conserved structural elements of the MARTX toxins and details the different toxin arrangements carried by Vibrio species and strains. The catalytic function of domains and how the toxins are linked to pathogenesis of human and animals is described.

  4. Multifunctional-autoprocessing repeats-in-toxin (MARTX) Toxins of Vibrios.

    PubMed

    Satchell, Karla J F

    2015-06-01

    Multifunctional-autoprocessing repeats-in-toxin (MARTX) toxins are a heterogeneous group of toxins found in a number of Vibrio species and other Gram-negative bacteria. The toxins are composed of conserved repeat regions and an autoprocessing protease domain that together function as a delivery platform for transfer of cytotoxic and cytopathic domains into target eukaryotic cell cytosol. Within the cells, the effectors can alter biological processes such as signaling or cytoskeletal structure, presumably to the benefit of the bacterium. Ten effector domains are found in the various Vibrio MARTX toxins, although any one toxin carries only two to five effector domains. The specific toxin variant expressed by a species can be modified by homologous recombination to acquire or lose effector domains, such that different strains within the same species can express distinct variants of the toxins. This review examines the conserved structural elements of the MARTX toxins and details the different toxin arrangements carried by Vibrio species and strains. The catalytic function of domains and how the toxins are linked to pathogenesis of human and animals is described. PMID:26185092

  5. Multifunctional-autoprocessing repeats-in-toxin (MARTX) Toxins of Vibrios

    PubMed Central

    Satchell, Karla J. F.

    2015-01-01

    Multifunctional-autoprocessing repeats-in-toxin (MARTX) toxins are a heterogeneous group of toxins found in a number of Vibrio species and other Gram-negative bacteria. The toxins are composed of conserved repeat regions and an autoprocessing protease domain that together function as a delivery platform for transfer of cytotoxic and cytopathic domains into target eukaryotic cell cytosol. Within the cells, the effectors can alter biological processes such as signaling or cytoskeletal structure, presumably to the benefit of the bacterium. Ten effector domains are found in the various Vibrio MARTX toxins, although any one toxin carries only two to five effector domains. The specific toxin variant expressed by a species can be modified by homologous recombination to acquire or lose effector domains, such that different strains within the same species can express distinct variants of the toxins. This review examines the conserved structural elements of the MARTX toxins and details the different toxin arrangements carried by Vibrio species and strains. The catalytic function of domains and how the toxins are linked to pathogenesis of human and animals is described. PMID:26185092

  6. Target-Driven Evolution of Scorpion Toxins

    PubMed Central

    Zhang, Shangfei; Gao, Bin; Zhu, Shunyi

    2015-01-01

    It is long known that peptide neurotoxins derived from a diversity of venomous animals evolve by positive selection following gene duplication, yet a force that drives their adaptive evolution remains a mystery. By using maximum-likelihood models of codon substitution, we analyzed molecular adaptation in scorpion sodium channel toxins from a specific species and found ten positively selected sites, six of which are located at the core-domain of scorpion α-toxins, a region known to interact with two adjacent loops in the voltage-sensor domain (DIV) of sodium channels, as validated by our newly constructed computational model of toxin-channel complex. Despite the lack of positive selection signals in these two loops, they accumulated extensive sequence variations by relaxed purifying selection in prey and predators of scorpions. The evolutionary variability in the toxin-bound regions of sodium channels indicates that accelerated substitutions in the multigene family of scorpion toxins is a consequence of dealing with the target diversity. This work presents an example of atypical co-evolution between animal toxins and their molecular targets, in which toxins suffered from more prominent selective pressure from the channels of their competitors. Our discovery helps explain the evolutionary rationality of gene duplication of toxins in a specific venomous species. PMID:26444071

  7. Target-Driven Evolution of Scorpion Toxins.

    PubMed

    Zhang, Shangfei; Gao, Bin; Zhu, Shunyi

    2015-10-07

    It is long known that peptide neurotoxins derived from a diversity of venomous animals evolve by positive selection following gene duplication, yet a force that drives their adaptive evolution remains a mystery. By using maximum-likelihood models of codon substitution, we analyzed molecular adaptation in scorpion sodium channel toxins from a specific species and found ten positively selected sites, six of which are located at the core-domain of scorpion α-toxins, a region known to interact with two adjacent loops in the voltage-sensor domain (DIV) of sodium channels, as validated by our newly constructed computational model of toxin-channel complex. Despite the lack of positive selection signals in these two loops, they accumulated extensive sequence variations by relaxed purifying selection in prey and predators of scorpions. The evolutionary variability in the toxin-bound regions of sodium channels indicates that accelerated substitutions in the multigene family of scorpion toxins is a consequence of dealing with the target diversity. This work presents an example of atypical co-evolution between animal toxins and their molecular targets, in which toxins suffered from more prominent selective pressure from the channels of their competitors. Our discovery helps explain the evolutionary rationality of gene duplication of toxins in a specific venomous species.

  8. MARTX toxins as effector delivery platforms.

    PubMed

    Gavin, Hannah E; Satchell, Karla J F

    2015-12-01

    Bacteria frequently manipulate their host environment via delivery of microbial 'effector' proteins to the cytosol of eukaryotic cells. In the case of the multifunctional autoprocessing repeats-in-toxins (MARTX) toxin, this phenomenon is accomplished by a single, >3500 amino acid polypeptide that carries information for secretion, translocation, autoprocessing and effector activity. MARTX toxins are secreted from bacteria by dedicated Type I secretion systems. The released MARTX toxins form pores in target eukaryotic cell membranes for the delivery of up to five cytopathic effectors, each of which disrupts a key cellular process. Targeted cellular processes include modulation or modification of small GTPases, manipulation of host cell signaling and disruption of cytoskeletal integrity. More recently, MARTX toxins have been shown to be capable of heterologous protein translocation. Found across multiple bacterial species and genera--frequently in pathogens lacking Type 3 or Type 4 secretion systems--MARTX toxins in multiple cases function as virulence factors. Innovative research at the intersection of toxin biology and bacterial genetics continues to elucidate the intricacies of the toxin as well as the cytotoxic mechanisms of its diverse effector collection.

  9. Plant insecticidal toxins in ecological networks.

    PubMed

    Ibanez, Sébastien; Gallet, Christiane; Després, Laurence

    2012-04-01

    Plant secondary metabolites play a key role in plant-insect interactions, whether constitutive or induced, C- or N-based. Anti-herbivore defences against insects can act as repellents, deterrents, growth inhibitors or cause direct mortality. In turn, insects have evolved a variety of strategies to act against plant toxins, e.g., avoidance, excretion, sequestration and degradation of the toxin, eventually leading to a co-evolutionary arms race between insects and plants and to co-diversification. Anti-herbivore defences also negatively impact mutualistic partners, possibly leading to an ecological cost of toxin production. However, in other cases toxins can also be used by plants involved in mutualistic interactions to exclude inadequate partners and to modify the cost/benefit ratio of mutualism to their advantage. When considering the whole community, toxins have an effect at many trophic levels. Aposematic insects sequester toxins to defend themselves against predators. Depending on the ecological context, toxins can either increase insects' vulnerability to parasitoids and entomopathogens or protect them, eventually leading to self-medication. We conclude that studying the community-level impacts of plant toxins can provide new insights into the synthesis between community and evolutionary ecology.

  10. [Axillary hyperhidrosis, botulinium A toxin treatment: Review].

    PubMed

    Clerico, C; Fernandez, J; Camuzard, O; Chignon-Sicard, B; Ihrai, T

    2016-02-01

    Injection of type A botulinum toxin in the armpits is a temporary treatment for axillary hyperhidrosis. This technique described in 1996 by Bushara et al., is known to be efficient and safe. The purpose of this article was to review the data concerning the treatment of axillary hyperhidrosis with botulinum toxin type A, and discuss the other treatment modalities for this socially disabling entity.

  11. The Ins and Outs of Anthrax Toxin

    PubMed Central

    Friebe, Sarah; van der Goot, F. Gisou; Bürgi, Jérôme

    2016-01-01

    Anthrax is a severe, although rather rare, infectious disease that is caused by the Gram-positive, spore-forming bacterium Bacillus anthracis. The infectious form is the spore and the major virulence factors of the bacterium are its poly-γ-D-glutamic acid capsule and the tripartite anthrax toxin. The discovery of the anthrax toxin receptors in the early 2000s has allowed in-depth studies on the mechanisms of anthrax toxin cellular entry and translocation from the endocytic compartment to the cytoplasm. The toxin generally hijacks the endocytic pathway of CMG2 and TEM8, the two anthrax toxin receptors, in order to reach the endosomes. From there, the pore-forming subunit of the toxin inserts into endosomal membranes and enables translocation of the two catalytic subunits. Insertion of the pore-forming unit preferentially occurs in intraluminal vesicles rather than the limiting membrane of the endosome, leading to the translocation of the enzymatic subunits in the lumen of these vesicles. This has important consequences that will be discussed. Ultimately, the toxins reach the cytosol where they act on their respective targets. Target modification has severe consequences on cell behavior, in particular on cells of the immune system, allowing the spread of the bacterium, in severe cases leading to host death. Here we will review the literature on anthrax disease with a focus on the structure of the toxin, how it enters cells and its immunological effects. PMID:26978402

  12. Botulinum Toxin and Gastrointestinal Tract Disorders

    PubMed Central

    Weiser, Kirsten; Kennedy, Abigail

    2008-01-01

    The history of botulinum toxin is fascinating. First recognized as the cause of botulism nearly 200 years ago, it was originally feared as a deadly poison. Over the last 30 years, however, botulinum toxin has been transformed into a readily available medication used to treat a variety of medical disorders. Interest in the use of botulinum toxin has been particularly strong for patients with spastic smooth muscle disorders of the gastrointestinal tract. Patients with achalasia, diffuse esophageal spasm, gastroparesis, sphincter of Oddi dysfunction, and anal fissures have all been treated with botulinum toxin injections, often with impressive results. However, not all patients respond to botulinum toxin therapy, and large randomized controlled trials are lacking for many conditions commonly treated with botulinum toxin. This paper reviews the history, microbiology, and pharmacology of botulinum toxin, discusses its mechanism of action, and then presents recent evidence from the literature regarding the use of botulinum toxin for the treatment of a variety of gastrointestinal tract disorders. PMID:21960915

  13. [T-2 toxin: occurrence and detection].

    PubMed

    Dohnal, V; Jezková, A; Kuca, K; Jun, D

    2007-07-01

    The paper is focused on the occurrence and methods for the detection of T-2 toxin, one of the most toxic trichothecene Fusarium mycotoxin. Due to its physical-chemical properties and high toxicity, T-2 toxin is classified as a potential biological warfare agent. PMID:17969315

  14. Formation and Control of Cyanobacterial Toxins

    EPA Science Inventory

    This presentation will cover the formation of harmful algal blooms and the control of their toxins. Data will be presented from current ORD projects on the treatment of cyanobacterial toxins through drinking water treatment facilities. The results will demonstrate that current c...

  15. Stool Test: C. Difficile Toxin (For Parents)

    MedlinePlus

    ... Things to Know About Zika & Pregnancy Stool Test: C. Difficile Toxin KidsHealth > For Parents > Stool Test: C. Difficile Toxin Print A A A Text Size ... Questions en español Muestra de materia fecal: toxina C. difficile What It Is A stool (feces) sample ...

  16. Plant Insecticidal Toxins in Ecological Networks

    PubMed Central

    Ibanez, Sébastien; Gallet, Christiane; Després, Laurence

    2012-01-01

    Plant secondary metabolites play a key role in plant-insect interactions, whether constitutive or induced, C- or N-based. Anti-herbivore defences against insects can act as repellents, deterrents, growth inhibitors or cause direct mortality. In turn, insects have evolved a variety of strategies to act against plant toxins, e.g., avoidance, excretion, sequestration and degradation of the toxin, eventually leading to a co-evolutionary arms race between insects and plants and to co-diversification. Anti-herbivore defences also negatively impact mutualistic partners, possibly leading to an ecological cost of toxin production. However, in other cases toxins can also be used by plants involved in mutualistic interactions to exclude inadequate partners and to modify the cost/benefit ratio of mutualism to their advantage. When considering the whole community, toxins have an effect at many trophic levels. Aposematic insects sequester toxins to defend themselves against predators. Depending on the ecological context, toxins can either increase insects’ vulnerability to parasitoids and entomopathogens or protect them, eventually leading to self-medication. We conclude that studying the community-level impacts of plant toxins can provide new insights into the synthesis between community and evolutionary ecology. PMID:22606374

  17. Novel diffusive gradients in thin films technique to assess labile sulfate in soil.

    PubMed

    Hanousek, Ondrej; Mason, Sean; Santner, Jakob; Chowdhury, Md Mobaroqul Ahsan; Berger, Torsten W; Prohaska, Thomas

    2016-09-01

    A novel diffusive gradients in thin films (DGT) technique for sampling labile soil sulfate was developed, based on a strong basic anion exchange resin (Amberlite IRA-400) for sulfate immobilization on the binding gel. For reducing the sulfate background on the resin gels, photopolymerization was applied instead of ammonium persulfate-induced polymerization. Agarose cross-linked polyacrylamide (APA) hydrogels were used as diffusive layer. The sulfate diffusion coefficient in APA gel was determined as 9.83 × 10(-6) ± 0.35 × 10(-6) cm(2) s(-1) at 25 °C. The accumulated sulfate was eluted in 1 mol L(-1) HNO3 with a recovery of 90.9 ± 1.6 %. The developed method was tested against two standard extraction methods for soil sulfate measurement. The obtained low correlation coefficients indicate that DGT and conventional soil test methods assess differential soil sulfate pools, rendering DGT a potentially important tool for measuring labile soil sulfate.

  18. Effects of lability of metal complex on free ion measurement using DMT.

    PubMed

    Weng, Liping; Van Riemsdijk, Willem H; Temminghoff, Erwin J M

    2010-04-01

    Very low concentrations of free metal ion in natural samples can be measured using the Donnan membrane technique (DMT) based on ion transport kinetics. In this paper, the possible effects of slow dissociation of metal complexes on the interpretation of kinetic DMT are investigated both theoretically and experimentally. The expressions of the lability parameter, Lgrangian , were derived for DMT. Analysis of new experimental studies using synthetic solution containing NTA as the ligand and Cu(2+) ions shows that when the ionic strength is low (labile species measured using other dynamic sensors (DGT, GIME) in several freshwaters, it is concluded that in most waters ion transport in DMT is controlled by diffusion in the membrane. Only in very soft waters (<0.7 mM Ca+Mg), the dissociation rate of natural metal complex may influence ion transport in DMT. In this case, neglecting this effect may lead to an underestimation of the free metal ion concentration measured.

  19. Novel diffusive gradients in thin films technique to assess labile sulfate in soil.

    PubMed

    Hanousek, Ondrej; Mason, Sean; Santner, Jakob; Chowdhury, Md Mobaroqul Ahsan; Berger, Torsten W; Prohaska, Thomas

    2016-09-01

    A novel diffusive gradients in thin films (DGT) technique for sampling labile soil sulfate was developed, based on a strong basic anion exchange resin (Amberlite IRA-400) for sulfate immobilization on the binding gel. For reducing the sulfate background on the resin gels, photopolymerization was applied instead of ammonium persulfate-induced polymerization. Agarose cross-linked polyacrylamide (APA) hydrogels were used as diffusive layer. The sulfate diffusion coefficient in APA gel was determined as 9.83 × 10(-6) ± 0.35 × 10(-6) cm(2) s(-1) at 25 °C. The accumulated sulfate was eluted in 1 mol L(-1) HNO3 with a recovery of 90.9 ± 1.6 %. The developed method was tested against two standard extraction methods for soil sulfate measurement. The obtained low correlation coefficients indicate that DGT and conventional soil test methods assess differential soil sulfate pools, rendering DGT a potentially important tool for measuring labile soil sulfate. PMID:27491301

  20. Windows of embryonic sexual lability in two lizard species with environmental sex determination.

    PubMed

    Shine, Richard; Warner, Daniel A; Radder, Rajkumar

    2007-07-01

    Temperature-dependent sex determination (TSD) occurs in all major reptile lineages, but the selective forces and physiological mechanisms that link sex to incubation temperature may differ among and within those groups. Different models for TSD evolution make different predictions about when offspring sex will respond to environmental cues. Although TSD has evolved in several lizard lineages, there is less detailed information on these taxa than in turtles and crocodilians with TSD. We incubated eggs of an agamid lizard (Amphibolurus muricatus) and a scincid lizard (Bassiana duperreyi), two species with TSD. Rather than manipulate incubation temperature to identify periods of sexual lability (as in most previous studies of this topic), we topically applied the aromatase inhibitor fadrozole to eggs at a variety of times through the incubation period. Fadrozole application sex-reversed the resultant hatchlings if applied from the time of oviposition until at least 60% of the way through incubation. In all of the TSD lizard species studied so far, offspring sex is determined either while the eggs are held inside the mother's body or soon after oviposition, providing substantial maternal control over incubation temperatures at this critical period. Hence, the hypothesis that TSD evolves because it enables offspring sex to be matched to conditions that are unpredictable at the time of laying is less likely to apply to squamates than to turtles, sphenodontians, and (especially) crocodiles, in which the period of sexual lability is delayed until long after oviposition.

  1. Rhizosphere Environment and Labile Phosphorus Release from Organic Waste-Amended Soils.

    NASA Astrophysics Data System (ADS)

    Dao, Thanh H.

    2015-04-01

    Crop residues and biofertilizers are primary sources of nutrients for organic crop production. However, soils treated with large amounts of nutrient-enriched manure have elevated phosphorus (P) levels in regions of intensive animal agriculture. Surpluses occurred in these amended soils, resulting in large pools of exchangeable inorganic P (Pi) and enzyme-labile organic P (Po) that averaging 30.9 and 68.2 mg kg-1, respectively. Organic acids produced during crop residue decomposition can promote the complexation of counter-ions and decouple and release unbound Pi from metal and alkali metal phosphates. Animal manure and cover crop residues also contain large amounts of soluble organic matter, and likely generate similar ligands. However, a high degree of heterogeneity in P spatial distribution in such amended fields, arising from variances in substrate physical forms ranging from slurries to dried solids, composition, and diverse application methods and equipment. Distinct clusters of Pi and Po were observed, where accumulation of the latter forms was associated with high soil microbial biomass C and reduced phosphomonoesterases' activity. Accurate estimates of plant requirements and lability of soil P pools, and real-time plant and soil P sensing systems are critical considerations to optimally manage manure-derived nutrients in crop production systems. An in situ X-ray fluorescence-based approach to sensing canopy and soil XRFS-P was developed to improve the yield-soil P relationship for optimal nutrient recommendations in addition to allowing in-the-field verification of foliar P status.

  2. [Effects of land use change on soil labile organic carbon in Central Jiangxi of China].

    PubMed

    Du, Man-Yi; Fan, Shao-Hui; Liu, Guang-Lu; Qi, Liang-Hua; Guo, Bao-Hu; Tang, Xiao-Lu; Xiao, Fu-Ming

    2013-10-01

    Selecting the 15-year abandoned land (AL) and three forest lands [Phyllostachys edulis plantation (PE), Schima superba secondary forest (SS), and Cunninghamia Lanceolata plantation (CL)] in Anfu County of Jiangxi Province as test objects, this paper studied the effects of land use change on the soil organic carbon (SOC) pool and soil labile organic carbon (SLOC) contents. The soil organic carbon (SOC), microbial biomass carbon (MBC), hot- water extractable carbon (HWC), and readily oxidizable carbon (ROC) contents in the test lands were all in the order of PE>CL>SS>AL. As compared with those in AL, the SOC content, soil carbon stock, and soil labile organic carbon (SLOC) contents in the three forest lands all decreased with increasing soil depth, and had an obvious accumulation in surface soil. The proportions of different kinds of SLOC to soil total organic carbon differed markedly, among which, ROC had the highest proportion, while MBC had the smallest one. There existed significant relationships between SOC, MBC, HWC, and ROC. The MBC, HWC, and ROC contained higher content of active carbon, and were more sensitive to the land use change, being able to be used as the indicators for evaluating the soil quality and fertility in central Jiangxi Province. PMID:24483085

  3. [Effects of land use change on soil labile organic carbon in Central Jiangxi of China].

    PubMed

    Du, Man-Yi; Fan, Shao-Hui; Liu, Guang-Lu; Qi, Liang-Hua; Guo, Bao-Hu; Tang, Xiao-Lu; Xiao, Fu-Ming

    2013-10-01

    Selecting the 15-year abandoned land (AL) and three forest lands [Phyllostachys edulis plantation (PE), Schima superba secondary forest (SS), and Cunninghamia Lanceolata plantation (CL)] in Anfu County of Jiangxi Province as test objects, this paper studied the effects of land use change on the soil organic carbon (SOC) pool and soil labile organic carbon (SLOC) contents. The soil organic carbon (SOC), microbial biomass carbon (MBC), hot- water extractable carbon (HWC), and readily oxidizable carbon (ROC) contents in the test lands were all in the order of PE>CL>SS>AL. As compared with those in AL, the SOC content, soil carbon stock, and soil labile organic carbon (SLOC) contents in the three forest lands all decreased with increasing soil depth, and had an obvious accumulation in surface soil. The proportions of different kinds of SLOC to soil total organic carbon differed markedly, among which, ROC had the highest proportion, while MBC had the smallest one. There existed significant relationships between SOC, MBC, HWC, and ROC. The MBC, HWC, and ROC contained higher content of active carbon, and were more sensitive to the land use change, being able to be used as the indicators for evaluating the soil quality and fertility in central Jiangxi Province.

  4. [Effects of stand structure regulation on soil labile organic carbon in Pinus elliottii plantation].

    PubMed

    Tan, Gui-Xia; Liu, Yuan-Qiu; Li, Lian-Lian; Liu, Wu; Zan, Yu-Ting; Huo, Bing-Nan; He, Mu-Jiao

    2014-05-01

    Taking 21-year-old Pinus elliottii pure plantation as the control, effects of enrichment planting with broadleaf trees (Liquidambar fornosana) after thinning the conifer trees (P. elliottii) on soil labile organic carbon of different plantations, including 3-year-old, 6-year-old, 9-year-old P. elliottii and 21-year-old P. elliottii-L. fornosana mixed plantations, were investigated. The results showed that the contents of soil dissolved organic carbon (DOC), readily oxidizable organic carbon (ROC), and microbial biomass carbon (MBC) significantly increased in the 6-year-old and 9-year-old plantations compared with those in the 21-year-old P. elliottii pure plantation. Soil labile organic carbon contents in the 21-year-old P. elliottii-L. fornosana mixed plantation increased significantly than those in 3-year-old, 6-year-old, 9-year-old stands, and the DOC, ROC and MBC contents increased by 113.1%, 53.3% and 54.6%, respectively, compared with those in the 21-year-old P. elliottii pure plantation. The results suggested that replanting with broadleaf trees are an effective measure to improve the soil ecological function in pure P. elliottii plantation.

  5. Total spontaneous resolution of chiral covalent networks from stereochemically labile metal complexes.

    PubMed

    Johansson, Anna; Håkansson, Mikael; Jagner, Susan

    2005-09-01

    Stereochemically labile copper and zinc complexes with the N,N'-dimethylethylenediamine ligand (dmeda) have been shown to be promising precursors for the total spontaneous resolution of chiral covalent networks. (N,N')-[Cu(NO3)2(dmeda)]infinity crystallises as a conglomerate and yields either enantiopure (R,R)-1 or enantiopure (S,S)-1. A mixed-valence copper(I/II) complex, [{Cu(II)Br2(dmeda)}3(Cu(I)Br)2]infinity (2), which crystallises as a pair of interpenetrating chiral (10,3)-a nets, is formed from CuBr, CuBr2 and dmeda. One net contains ligands with solely (R,R) configuration and exhibits helices with (P) configuration while the other has solely (S,S)-dmeda ligands and gives rise to a net in which the helices have (M) configuration. The whole crystalline arrangement is racemic, because the interpenetrating chiral nets are of opposite handedness. With zinc chloride (R,S)-[ZnCl(dmeda)2]2[ZnCl4] (3) is obtained, which is a network structure, although not chiral. Total spontaneous resolution of stereochemically labile metal complexes formed from achiral or racemic building blocks is suggested as a viable route for the preparation of covalent chiral networks. Once the absolute structure of the compound has been determined by X-ray crystallography, a quantitative determination of the enantiomeric excess of the bulk product can be undertaken by means of solid-state CD spectroscopy.

  6. Heterotrophic activity and biodegradation of labile and refractory compounds by groundwater and stream microbial populations.

    PubMed Central

    Ladd, T I; Ventullo, R M; Wallis, P M; Costerton, J W

    1982-01-01

    The bacteriology and heterotrophic activity of a stream and of nearby groundwater in Marmot Basin, Alberta, Canada, were studied. Acridine orange direct counts indicated that bacterial populations in the groundwater were greater than in the stream. Bacteria that were isolated from the groundwater were similar to species associated with soils. Utilization of labile dissolved organic material as measured by the heterotrophic potential technique with glutamic acid, phenylalanine, and glycolic acid as substrates was generally greater in the groundwater. In addition, specific activity indices for the populations suggested greater metabolic activity per bacterium in the groundwater. 14C-labeled lignocellulose, preferentially labeled in the lignin fraction by feeding Picea engelmannii [14C]phenylalanine, was mineralized by microorganisms in both the groundwater and the stream, but no more than 4% of the added radioactivity was lost as 14CO2 within 960 h. Up to 20% of [3'-14C]cinnamic acid was mineralized by microorganisms in both environments within 500 h. Both microbial populations appear to influence the levels of labile and recalcitrant dissolved organic material in mountain streams. PMID:7125651

  7. Novel diffusive gradients in thin films technique to assess labile sulfate in soil

    PubMed Central

    Ahsan Chowdhury, Md Mobaroqul; Berger, Torsten W.; Prohaska, Thomas

    2016-01-01

    A novel diffusive gradients in thin films (DGT) technique for sampling labile soil sulfate was developed, based on a strong basic anion exchange resin (Amberlite IRA-400) for sulfate immobilization on the binding gel. For reducing the sulfate background on the resin gels, photopolymerization was applied instead of ammonium persulfate-induced polymerization. Agarose cross-linked polyacrylamide (APA) hydrogels were used as diffusive layer. The sulfate diffusion coefficient in APA gel was determined as 9.83 × 10−6 ± 0.35 × 10-6 cm2 s−1 at 25 °C. The accumulated sulfate was eluted in 1 mol L−1 HNO3 with a recovery of 90.9 ± 1.6 %. The developed method was tested against two standard extraction methods for soil sulfate measurement. The obtained low correlation coefficients indicate that DGT and conventional soil test methods assess differential soil sulfate pools, rendering DGT a potentially important tool for measuring labile soil sulfate. PMID:27491301

  8. Constraints on Transport and Emplacement Mechanisms of Labile Fractions in Lunar Cold Traps

    NASA Technical Reports Server (NTRS)

    Rickman, D.; Gertsch, L.

    2014-01-01

    Sustaining the scientific exploration of the Solar System will require a significant proportion of the necessary fuels and propellants, as well as other bulk commodities, to be produced from local raw materials [1]. The viability of mineral production depends on the ability to locate and characterize mineable deposits of the necessary feedstocks. This requires, among other things, a workable understanding of the mechanisms by which such deposits form, which is the subject of Economic Geology. Multiple deposition scenarios are possible for labile materials on the Moon. This paper suggests labile fractions moved diffusely through space; deposits may grow richer with depth until low porosity rock; lateral transport is likely to have occurred with the regolith, at least for short distances; crystalline ice may not exist; the constituent phases could be extremely complex. At present we can constrain the sources only mildly; once on the Moon, the transport mechanisms inherently mix and therefore obscure the origins. However, the importance of expanding our understanding of ore-forming processes on the Moon behooves us to make the attempt. Thus begins a time of new inquiry for Economic Geology.

  9. Brown spider dermonecrotic toxin directly induces nephrotoxicity

    SciTech Connect

    Chaim, Olga Meiri; Sade, Youssef Bacila; Bertoni da Silveira, Rafael; Toma, Leny; Kalapothakis, Evanguedes; Chavez-Olortegui, Carlos; Mangili, Oldemir Carlos; Gremski, Waldemiro; Dietrich, Carl Peter von; Nader, Helena B.; Sanches Veiga, Silvio . E-mail: veigass@ufpr.br

    2006-02-15

    Brown spider (Loxosceles genus) venom can induce dermonecrotic lesions at the bite site and systemic manifestations including fever, vomiting, convulsions, disseminated intravascular coagulation, hemolytic anemia and acute renal failure. The venom is composed of a mixture of proteins with several molecules biochemically and biologically well characterized. The mechanism by which the venom induces renal damage is unknown. By using mice exposed to Loxosceles intermedia recombinant dermonecrotic toxin (LiRecDT), we showed direct induction of renal injuries. Microscopic analysis of renal biopsies from dermonecrotic toxin-treated mice showed histological alterations including glomerular edema and tubular necrosis. Hyalinization of tubules with deposition of proteinaceous material in the tubule lumen, tubule epithelial cell vacuoles, tubular edema and epithelial cell lysis was also observed. Leukocytic infiltration was neither observed in the glomerulus nor the tubules. Renal vessels showed no sign of inflammatory response. Additionally, biochemical analyses showed such toxin-induced changes in renal function as urine alkalinization, hematuria and azotemia with elevation of blood urea nitrogen levels. Immunofluorescence with dermonecrotic toxin antibodies and confocal microscopy analysis showed deposition and direct binding of this toxin to renal intrinsic structures. By immunoblotting with a hyperimmune dermonecrotic toxin antiserum on renal lysates from toxin-treated mice, we detected a positive signal at the region of 33-35 kDa, which strengthens the idea that renal failure is directly induced by dermonecrotic toxin. Immunofluorescence reaction with dermonecrotic toxin antibodies revealed deposition and binding of this toxin directly in MDCK epithelial cells in culture. Similarly, dermonecrotic toxin treatment caused morphological alterations of MDCK cells including cytoplasmic vacuoles, blebs, evoked impaired spreading and detached cells from each other and from

  10. Renal response to environmental toxins.

    PubMed

    Finn, W F

    1977-10-01

    Several characteristics of normal renal function increase the risk to the kidney of damage by environmental toxins. Due to the magnitude of renal blood flow the total amount of noxious substance delivered may be disproportionately high. Furthermore, the capacity to concentrate substances within the kidney by processes of filtration, reabsorption and secretion has the potential to increase the toxicity of agents which would otherwise not lead to tissue injury. Unfortunately, there are few tests of renal function which are able to detect early functional abnormalities and which, at the same time, are suited for screening purposes by virtue of their simplicity, cost and safety. Furthermore, interpretation of the tests is complicated by adaptive changes in renal function which occur with aging and in response to other disease processes. Environmental agents produce a wide spectrum of renal dysfunction. Acute renal damage follows exposure to glycols, organic solvents, heavy metals, diagnostic and therapeutic agents and a variety of miscellaneous substances. Chronic renal disease may take the form of isolated tubular defects as seen with cadmium, interstitial nephritis due to the ingestion of lead, or vascular damage induced by external radiation. Some forms of glomerulonephritis may also be related to environmental toxins as are certain tumors of the urinary tract. In a somewhat different fashion, patients whose renal function is limited by the presence of pre-existing disease may manifest toxicity from substances ordinarily excreted in the urine. Particular problems exist with the patients on dialysis, as they are at considerable risk to alterations in the environment.

  11. Botulinum toxin in poststroke spasticity.

    PubMed

    Ozcakir, Suheda; Sivrioglu, Koncuy

    2007-06-01

    Poststroke hemiparesis, together with abnormal muscle tone, is a major cause of morbidity and disability. Although most hemiparetic patients are able to reach different ambulatory levels with rehabilitation efforts, upper and lower limb spasticity can impede activities of daily living, personal hygiene, ambulation and, in some cases, functional improvement. The goals of spasticity management include increasing mobility and range of motion, attaining better hygiene, improving splint wear and other functional activities. Conservative measures, such as positioning, stretching and exercise are essential in spasticity management, but alone often are inadequate to effectively control it. Oral antispastic medications often provide limited effects with short duration and frequent unwanted systemic side effects, such as weakness, sedation and dry mouth. Therefore, neuromuscular blockade by local injections have become the first choice for the treatment of focal spasticity, particularly in stroke patients. Botulinum toxin (BTX), being one of the most potent biological toxins, acts by blocking neuromuscular transmission via inhibiting acetylcholine release. Currently, focal spasticity is being treated successfully with BTX via injecting in the spastic muscles. Two antigenically distinct serotypes of BTX are available on the market as type A and B. Clinical studies of BTX used for spastic hemiplegic patients are reviewed in this article in two major categories, upper and lower limb applications. This review addresses efficacy in terms of outcome measures, such as muscle tone reduction and functional outcome, as well as safety issues. Application modifications of dose, dilutions, site of injections and combination therapies with BTX injections are also discussed. PMID:17607049

  12. Crystallization of isoelectrically homogeneous cholera toxin

    SciTech Connect

    Spangler, B.D.; Westbrook, E.M. )

    1989-02-07

    Past difficulty in growing good crystals of cholera toxin has prevented the study of the crystal structure of this important protein. The authors have determined that failure of cholera toxin to crystallize well has been due to its heterogeneity. They have now succeeded in overcoming the problem by isolating a single isoelectric variant of this oligomeric protein (one A subunit and five B subunits). Cholera toxin purified by their procedure readily forms large single crystals. The crystal form has been described previously. They have recorded data from native crystals of cholera toxin to 3.0-{angstrom} resolution with our electronic area detectors. With these data, they have found the orientation of a 5-fold symmetry axis within these crystals, perpendicular to the screw dyad of the crystal. They are now determining the crystal structure of cholera toxin by a combination of multiple heavy-atom isomorphous replacement and density modification techniques, making use of rotational 5-fold averaging of the B subunits.

  13. Metal contents of phytoplankton and labile particulate material in the North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Twining, Benjamin S.; Rauschenberg, Sara; Morton, Peter L.; Vogt, Stefan

    2015-09-01

    Phytoplankton contribute significantly to global C cycling and serve as the base of ocean food webs. Phytoplankton require trace metals for growth and also mediate the vertical distributions of many metals in the ocean. We collected bulk particulate material and individual phytoplankton cells from the upper water column (<150 m) of the North Atlantic Ocean as part of the US GEOTRACES North Atlantic Zonal Transect cruise (GEOTRACES GA03). Particulate material was first leached to extract biogenic and potentially-bioavailable elements, and the remaining refractory material was digested in strong acids. The cruise track spanned several ocean biomes and geochemical regions. Particulate concentrations of metals associated primarily with lithogenic phases (Fe, Al, Ti) were elevated in surface waters nearest North America, Africa and Europe, and elements associated primarily with biogenic material (P, Cd, Zn, Ni) were also found at higher concentrations near the coasts. However metal/P ratios of labile particulate material were also elevated in the middle of the transect for Fe, Ni, Co, Cu, and V. P-normalized cellular metal quotas measured with synchrotron X-ray fluorescence (SXRF) were generally comparable to ratios in bulk labile particles but did not show mid-basin increases. Manganese and Fe ratios and cell quotas were higher in the western part of the section, nearest North America, and both elements were more enriched in bulk particles, relative to P, than in cells, suggesting the presence of labile oxyhydroxide particulate phases. Cellular Fe quotas thus did not increase in step with aeolian dust inputs, which are highest near Africa; these data suggest that the dust inputs have low bioavailability. Copper and Ni cell quotas were notably higher nearest the continental margins. Overall mean cellular metal quotas were similar to those measured in the Pacific and Southern Oceans except for Fe, which was approximately 3-fold higher in North Atlantic cells. Cellular Fe

  14. Cu lability and bioavailability in an urban stream during baseflow versus stormflow

    NASA Astrophysics Data System (ADS)

    Vadas, T.; Luan, H.

    2012-12-01

    Urban streams are dynamic systems with many anthropogenic inputs and stressors. Existing contaminant inputs are regulated through total maximum daily loads. Techniques for assessing that load are based on a combination of acute and chronic water quality criteria, biotic ligand models, and physical, chemical and biological assessments. In addition, the apportionment of reduction in load to different sources is based on total mass and not, for example, on bioavailable fraction. Our understanding of the impact of different metal inputs to stream impairment is limited. Free metal ions are understood to play a role in direct cellular uptake, but metal speciation (e.g. free metal, labile metals, or size fractionated) is relevant to more complex stream food webs. As part of an ongoing study, this work examines dissolved and particulate Cu concentrations in the Hockanum River, Vernon, CT situated in a developed watershed. Stream samples were taken during baseflow as well as stormflow upstream and downstream of wastewater treatment plant and stormwater runoff inputs. In addition, diffusive gradient in thin-film (DGT) devices which measure labile metal concentrations and cultured periphyton were used to examine bioavailable fractions. Total and filtered Cu concentrations ranged from about 1.3 to 10.7 μg/L, and 0.9 to 5.1 μg/L, respectively. Cu concentrations always increased downstream of the wastewater treatment plant by about 1.1-2 times, and effluent accounted for about 30% of baseflow. Generally, small increases (<10%) in concentration were observed in metals directly downstream of stormwater inlets, likely due to low volumes of runoff contributed from stormwater outfalls during these sampling periods. However, Cu concentrations were elevated (about 2-5 times higher) at all sites downstream from the wastewater treatment plant downstream sampling point, suggesting contributions from sediment resuspension. DGT measured concentrations represented 30 to 70% of dissolved Cu

  15. Evaluation of insulin-like growth factor acid-labile subunit as a potential biomarker of effect for deoxynivalenol-induced proinflammatory cytokine expression.

    PubMed

    Flannery, Brenna M; Amuzie, Chidozie J; Pestka, James J

    2013-02-01

    Consumption of the trichothecene deoxynivalenol (DON) suppresses growth in experimental animals - an adverse effect that was used to establish the tolerable daily intake for this toxin. DON ingestion has been recently found to suppress plasma insulin-like growth factor acid-labile subunit (IGFALS), a protein essential for growth. Studies were conducted to explore the feasibility of using plasma IGFALS as a biomarker of effect for DON. In the first study, weanling mice were fed 0, 1, 2.5, 5 and 10 ppm DON and weight and plasma IGFALS determined at intervals over 9 wk. Reduced body weight gains were detectable beginning at wk 5 in the 10 ppm dose and wk 7 at the 5 ppm dose. Plasma IGFALS was significantly depressed at wk 5 in the 5 and 10 ppm groups at wk 9 in the 10 ppm group. Depressed IGFALS significantly correlated with reduced body weight at wk 5 and 9. Benchmark dose modeling revealed the BMDL and BMD for plasma IGFALS reduction were 1.1 and 3.0 ppm DON and for weight reduction were 2.1 and 4.5 ppm DON. In the second study, it was demonstrated that mice fed 15 ppm DON diet had significantly less plasma IGFALS than mice fed identical amounts of control diet. Thus DON's influence on IGFALS likely reflects the combined effects of reduced food intake as well as its physiological action involving suppressors of cytokine signaling. Taken together, these findings suggest that plasma IGFALS might be a useful biomarker for DON's adverse effects on growth.

  16. Evaluation of Insulin-Like Growth Factor Acid-Labile Subunit as a Potential Biomarker of Effect for Deoxynivalenol-Induced Proinflammatory Cytokine Expression

    PubMed Central

    Flannery, Brenna M.; Amuzie, Chidozie J.; Pestka, James J.

    2013-01-01

    Consumption of the trichothecene deoxynivalenol (DON) suppresses growth in experimental animals - an adverse effect that was used to establish the tolerable daily intake for this toxin. DON ingestion has been recently found to suppress plasma insulin-like growth factor acid-labile subunit (IGFALS), a protein essential for growth. Studies were conducted to explore the feasibility of using plasma IGFALS as a biomarker of effect for DON. In the first study, weanling mice were fed 0, 1, 2.5, 5 and 10 ppm DON and weight and plasma IGFALS determined at intervals over 9 wk. Reduced body weight gains were detectable beginning at wk 5 in the 10 ppm dose and wk 7 at the 5 ppm dose. Plasma IGFALS was significantly depressed at wk 5 in the 5 and 10 ppm groups at wk 9 in the 10 ppm group. Depressed IGFALS significantly correlated with reduced body weight at wk 5 and 9. Benchmark dose modeling revealed the BMDL and BMD for plasma IGFALS reduction were 1.1 and 3.0 ppm DON and for weight reduction were 2.1 and 4.5 ppm DON. In the second study, it was demonstrated that mice fed 15 ppm DON diet had significantly less plasma IGFALS than mice fed identical amounts of control diet. Thus DON’s influence on IGFALS likely reflects the combined effects of reduced food intake as well as its physiological action involving suppressors of cytokine signaling. Taken together, these findings suggest that plasma IGFALS might be a useful biomarker for DON’s adverse effects on growth. PMID:23298694

  17. Development and Lability in the Parent-Child Relationship During Adolescence: Associations With Pubertal Timing and Tempo

    PubMed Central

    Marceau, Kristine; Ram, Nilam; Susman, Elizabeth

    2014-01-01

    Adolescents' and parents' reactions to pubertal development are hypothesized to contribute to changes in family dynamics. Using 7-year longitudinal data from the NICHD-SECCYD (488 boys, 475 girls) we examined relations between pubertal development (timing, tempo) and trajectories (developmental change and year-to-year lability) of parent-child conflict and closeness from age 8.5 to 15.5 years. Changes were mostly characterized by year-to-year fluctuations – lability. Parent-child conflict increased and closeness decreased some with age. Pubertal timing and tempo were more consistently associated with lability in parent-child relationships than with long-term trends, although faster tempo was associated with steeper decreases in parent-child closeness. Findings provide a platform for examining how puberty contributes to both long-term and transient changes in adolescents' relationships and adjustment. PMID:26321856

  18. Labile trace elements in basaltic achondrites: Can they distinguish between meteorites from the Moon, Mars, and V-type asteroids?

    NASA Astrophysics Data System (ADS)

    Wolf, Stephen F.; Wang, Ming-Sheng; Lipschutz, Michael E.

    2009-06-01

    We report data for 14 mainly labile trace elements (Ag, Au, Bi, Cd, Cs, Ga, In, Rb, Sb, Se, Te, Tl, U, and Zn) in eight whole-rock lunar meteorites (Asuka [A-] 881757, Dar al Gani [DaG] 262, Elephant Moraine [EET] 87521, Queen Alexandra Range [QUE] 93069, QUE 94269, QUE 94281, Yamato [Y-] 793169, and Y-981031), and Martian meteorite (DaG 476) and incorporate these into a comparative study of basaltic meteorites from the Moon, Mars, and V-type asteroids. Multivariate cluster analysis of data for these elements in 14 lunar, 13 Martian, and 34 howardite, eucrite, and diogenite (HED) meteorites demonstrate that materials from these three parents are distinguishable using these markers of late, low-temperature episodes. This distinguishability is essentially as complete as that based on markers of high-temperature igneous processes. Concentrations of these elements in 14 lunar meteorites are essentially lognormally distributed and generally more homogeneous than in Martian and HED meteorites. Mean siderophile and labile element concentrations in the 14 lunar meteorites indicate the presence of a CI-equivalent micrometeorite admixture of 2.6% When only feldspathic samples are considered, our data show a slightly higher value of 3.4% consistent with an increasing micrometeorite content in regolith samples of higher maturity. Concentrations of labile elements in the 8 feldspathic samples hint at the presence of a fractionated highly labile element component, possibly volcanic in origin, at a level comparable to the micrometeorite component. Apparently, the process(es) that contributed to establishing lunar meteorite siderophile and labile trace element contents occurred in a system open to highly labile element transport.

  19. In situ high-resolution evaluation of labile arsenic and mercury in sediment of a large shallow lake.

    PubMed

    Wang, Chao; Yao, Yu; Wang, Peifang; Hou, Jun; Qian, Jin; Yuan, Ye; Fan, Xiulei

    2016-01-15

    The precise evaluation of arsenic (As) and mercury (Hg) bioavailability in sediment is crucial to controlling As and Hg contamination, but traditional ex situ measurements hamper comprehensive analysis of labile As and Hg in sediment. In this study, we characterized in situ labile As and Hg in sediment of Lake Hongze using the zirconium (Zr) oxide diffusive gradients in thin films (DGT) technique and 3-mercaptopropyl functionalized silica gel DGT, respectively. The concentrations of DGT-labile As and Hg in the sediment profiles were found to exhibit considerable variation, ranging from 0.15 to 4.15 μg L(-1) for As and from 0.04 to 1.35 μg L(-1) for Hg. As and Hg flux values, calculated based on the concentration gradients measured from the DGT profiles for both the overlying water and sediment close to the sediment-water interface, were used to determine the contamination status of As and Hg. Flux values of As and Hg were between -0.066 and 0.067 ng cm(-2)d(-1) and between -0.0187 and 0.0181 ng cm(-2)d(-1), respectively. The GNU's Not Unix R (GNU R) programming language was used to identify outliers of As and Hg at various depths at the sampling sites. The results indicate that the sites with the most outliers were all located in the regions that were seriously affected by contaminants from the Huai River. The DGT-labile As and Hg concentrations in the 0-30 mm layer were found to be significantly correlated with concentrations of labile As and Hg, total dissolved As and Hg, and total As and Hg in the overlying water, as indicated by ex situ measurements. Results show that DGT is a reliable and high-resolution technique that can be used for in situ monitoring of the labile fractions of As and Hg in sediment in fresh water bodies. PMID:26398454

  20. In situ high-resolution evaluation of labile arsenic and mercury in sediment of a large shallow lake.

    PubMed

    Wang, Chao; Yao, Yu; Wang, Peifang; Hou, Jun; Qian, Jin; Yuan, Ye; Fan, Xiulei

    2016-01-15

    The precise evaluation of arsenic (As) and mercury (Hg) bioavailability in sediment is crucial to controlling As and Hg contamination, but traditional ex situ measurements hamper comprehensive analysis of labile As and Hg in sediment. In this study, we characterized in situ labile As and Hg in sediment of Lake Hongze using the zirconium (Zr) oxide diffusive gradients in thin films (DGT) technique and 3-mercaptopropyl functionalized silica gel DGT, respectively. The concentrations of DGT-labile As and Hg in the sediment profiles were found to exhibit considerable variation, ranging from 0.15 to 4.15 μg L(-1) for As and from 0.04 to 1.35 μg L(-1) for Hg. As and Hg flux values, calculated based on the concentration gradients measured from the DGT profiles for both the overlying water and sediment close to the sediment-water interface, were used to determine the contamination status of As and Hg. Flux values of As and Hg were between -0.066 and 0.067 ng cm(-2)d(-1) and between -0.0187 and 0.0181 ng cm(-2)d(-1), respectively. The GNU's Not Unix R (GNU R) programming language was used to identify outliers of As and Hg at various depths at the sampling sites. The results indicate that the sites with the most outliers were all located in the regions that were seriously affected by contaminants from the Huai River. The DGT-labile As and Hg concentrations in the 0-30 mm layer were found to be significantly correlated with concentrations of labile As and Hg, total dissolved As and Hg, and total As and Hg in the overlying water, as indicated by ex situ measurements. Results show that DGT is a reliable and high-resolution technique that can be used for in situ monitoring of the labile fractions of As and Hg in sediment in fresh water bodies.

  1. Cyanobacterial toxins: risk management for health protection.

    PubMed

    Codd, Geoffrey A; Morrison, Louise F; Metcalf, James S

    2005-03-15

    This paper reviews the occurrence and properties of cyanobacterial toxins, with reference to the recognition and management of the human health risks which they may present. Mass populations of toxin-producing cyanobacteria in natural and controlled waterbodies include blooms and scums of planktonic species, and mats and biofilms of benthic species. Toxic cyanobacterial populations have been reported in freshwaters in over 45 countries, and in numerous brackish, coastal, and marine environments. The principal toxigenic genera are listed. Known sources of the families of cyanobacterial toxins (hepato-, neuro-, and cytotoxins, irritants, and gastrointestinal toxins) are briefly discussed. Key procedures in the risk management of cyanobacterial toxins and cells are reviewed, including derivations (where sufficient data are available) of tolerable daily intakes (TDIs) and guideline values (GVs) with reference to the toxins in drinking water, and guideline levels for toxigenic cyanobacteria in bathing waters. Uncertainties and some gaps in knowledge are also discussed, including the importance of exposure media (animal and plant foods), in addition to potable and recreational waters. Finally, we present an outline of steps to develop and implement risk management strategies for cyanobacterial cells and toxins in waterbodies, with recent applications and the integration of Hazard Assessment Critical Control Point (HACCP) principles. PMID:15737680

  2. Cyanobacterial toxins: risk management for health protection

    SciTech Connect

    Codd, Geoffrey A.; Morrison, Louise F.; Metcalf, James S

    2005-03-15

    This paper reviews the occurrence and properties of cyanobacterial toxins, with reference to the recognition and management of the human health risks which they may present. Mass populations of toxin-producing cyanobacteria in natural and controlled waterbodies include blooms and scums of planktonic species, and mats and biofilms of benthic species. Toxic cyanobacterial populations have been reported in freshwaters in over 45 countries, and in numerous brackish, coastal, and marine environments. The principal toxigenic genera are listed. Known sources of the families of cyanobacterial toxins (hepato-, neuro-, and cytotoxins, irritants, and gastrointestinal toxins) are briefly discussed. Key procedures in the risk management of cyanobacterial toxins and cells are reviewed, including derivations (where sufficient data are available) of tolerable daily intakes (TDIs) and guideline values (GVs) with reference to the toxins in drinking water, and guideline levels for toxigenic cyanobacteria in bathing waters. Uncertainties and some gaps in knowledge are also discussed, including the importance of exposure media (animal and plant foods), in addition to potable and recreational waters. Finally, we present an outline of steps to develop and implement risk management strategies for cyanobacterial cells and toxins in waterbodies, with recent applications and the integration of Hazard Assessment Critical Control Point (HACCP) principles.

  3. Significance of Isotopically Labile Organic Hydrogen in Thermal Maturation of Organic Matter

    SciTech Connect

    Arndt Schimmelmann; Maria Mastalerz

    2010-03-30

    Isotopically labile organic hydrogen in fossil fuels occupies chemical positions that participate in isotopic exchange and in chemical reactions during thermal maturation from kerogen to bitumen, oil and gas. Carbon-bound organic hydrogen is isotopically far less exchangeable than hydrogen bound to nitrogen, oxygen, or sulfur. We explore why organic hydrogen isotope ratios express a relationship with organic nitrogen isotope ratios in kerogen at low to moderate maturity. We develop and apply new techniques to utilize organic D/H ratios in organic matter fractions and on a molecular level as tools for exploration for fossil fuels and for paleoenvironmental research. The scope of our samples includes naturally and artificially matured substrates, such as coal, shale, oil and gas.

  4. Clostridium perfringens type A-E toxin plasmids.

    PubMed

    Freedman, John C; Theoret, James R; Wisniewski, Jessica A; Uzal, Francisco A; Rood, Julian I; McClane, Bruce A

    2015-05-01

    Clostridium perfringens relies upon plasmid-encoded toxin genes to cause intestinal infections. These toxin genes are associated with insertion sequences that may facilitate their mobilization and transfer, giving rise to new toxin plasmids with common backbones. Most toxin plasmids carry a transfer of clostridial plasmids locus mediating conjugation, which likely explains the presence of similar toxin plasmids in otherwise unrelated C. perfringens strains. The association of many toxin genes with insertion sequences and conjugative plasmids provides virulence flexibility when causing intestinal infections. However, incompatibility issues apparently limit the number of toxin plasmids maintained by a single cell.

  5. Inhibition of Shiga toxin 2 (Stx2) in apple juices and its resistance to pasteurization.

    PubMed

    Rasooly, Reuven; Do, Paula M; Levin, Carol E; Friedman, Mendel

    2010-06-01

    In the present study, we evaluated Shiga toxin (Stx2) activity in apple juices by measuring a decrease in dehydrogenase activity of Vero cells with the microculture tetrazolium (MTT) assay. Freshly prepared juice from Red Delicious apples and Golden Delicious apples inhibited the biological activity of the bacterial toxin Stx2 produced by E. coli O157:H7 strains. Studies with immunomagnetic beads bearing specific antibodies against the toxin revealed that Stx2 activity was restored when removed from the apple juice. SDS gel electrophoresis revealed no difference (P < 0.05) in the densities or molecular weights between Stx2 in either PBS or apple juices. These results suggest that Stx2 may be reversibly bound to small molecular weight constituents in the juice. The Stx2 toxin was not inactivated on exposure to heat programs (63 degrees C for 30 min, 72 degrees C for 15 s, 89 degrees C for 1 s) commonly used to pasteurize apple juice, but lost all activity when exposed to 100 degrees C for 5 min. The results suggest that pasteurization of apple juice used to inactivate E. coli O157:H7 has no effect on Stx2, and that food-compatible and safe antitoxin compounds can be used to inhibit the biological activity of the Shiga toxin.

  6. Effect of temperature on the decomposition rate of labile and stable organic matter in an agrochernozem

    NASA Astrophysics Data System (ADS)

    Larionova, A. A.; Kvitkina, A. K.; Yevdokimov, I. V.; Bykhovets, S. S.; Stulin, A. F.

    2014-05-01

    An hypothesis about the different temperature dependences of the decomposition of the labile and stable organic carbon pools has been tested using an agrochernozem sampled from an experimental plot of 42-year-old continuous corn in Voronezh oblast. The partitioning of the CO2 loss during the decomposition of the labile and stable soil organic matter (SOM) at 2, 12, and 22°C in a long-term incubation experiment was performed using the method of 13C natural abundance by C3-C4 transition. On the basis of the determined decomposition constants, the SOM pools have been arranged in an order according to their increasing stability: plant residues < new (C4) SOM < old (C3) SOM. The tested hypothesis has been found valid only for a limited temperature interval. The temperature coefficient Q 10 increases in the stability order from 1.2 to 4.3 in the interval of 12-22°C. At low temperatures (2-12°C), the values of Q 10 insignificantly vary among the SOM pools and lie in the range of 2.2-2.8. Along with the decomposition constants of the SOM, the new-to-old carbon ratio in the CO2 efflux from the soil and the magnitude of the negative priming effect for the old SOM caused by the input of new organic matter depend on the temperature. In the soil under continuous corn fertilized with NPK, the increased decomposition of C3 SOM is observed compared to the unfertilized control; the temperature dependences of the SOM decomposition are similar in both agrochernozem treatments.

  7. Labile and recalcitrant organic matter utilization by river biofilm under increasing water temperature.

    PubMed

    Ylla, Irene; Romaní, Anna M; Sabater, Sergi

    2012-10-01

    Microbial biofilms in rivers contribute to the decomposition of the available organic matter which typically shows changes in composition and bioavailability due to their origin, seasonality, and watershed characteristics. In the context of global warming, enhanced biofilm organic matter decomposition would be expected but this effect could be specific when either a labile or a recalcitrant organic matter source would be available. A laboratory experiment was performed to mimic the effect of the predicted increase in river water temperature (+4 °C above an ambient temperature) on the microbial biofilm under differential organic matter sources. The biofilm microbial community responded to higher water temperature by increasing bacterial cell number, respiratory activity (electron transport system) and microbial extracellular enzymes (extracellular enzyme activity). At higher temperature, the phenol oxidase enzyme explained a large fraction of respiratory activity variation suggesting an enhanced microbial use of degradation products from humic substances. The decomposition of hemicellulose (β-xylosidase activity) seemed to be also favored by warmer conditions. However, at ambient temperature, the enzymes highly responsible for respiration activity variation were β-glucosidase and leu-aminopeptidase, suggesting an enhanced microbial use of polysaccharides and peptides degradation products. The addition of labile dissolved organic carbon (DOC; dipeptide plus cellobiose) caused a further augmentation of heterotrophic biomass and respiratory activity. The changes in the fluorescence index and the ratio Abs(250)/total DOC indicated that higher temperature accelerated the rates of DOC degradation. The experiment showed that the more bioavailable organic matter was rapidly cycled irrespective of higher temperature while degradation of recalcitrant substances was enhanced by warming. Thus, pulses of carbon at higher water temperature might have consequences for DOC

  8. Oxidative stress and labile plasmatic iron in anemic patients following blood therapy

    PubMed Central

    Fernandes, Marília Sabo; Rissi, Tatiana Tamborena; Zuravski, Luisa; Mezzomo, Juliana; Vargas, Carmen Regla; Folmer, Vanderlei; Soares, Félix Alexandre Antunes; Manfredini, Vanusa; Ahmed, Mushtaq; Puntel, Robson Luiz

    2014-01-01

    AIM: To determine the plasmatic iron content and evaluate the oxidative stress (OS) markers in subjects receiving blood therapy. METHODS: Thirty-nine individuals with unspecified anemia receiving blood transfusions and 15 healthy subjects were included in the study. Anemic subjects were divided into three subgrouP: (1) those that received up to five blood transfusions (n = 14); (2) those that received from five to ten transfusions (n = 11); and (3) those that received more than ten transfusions (n = 14). Blood samples were collected by venous arm puncture and stored in tubes containing heparin. The plasma and cells were separated by centrifugation and subsequently used for analyses. Statistical analyses were performed using Kruskal-Wallis analysis of variance followed by Dunn’s multiple comparison tests when appropriate. RESULTS: The eletrophoretic hemoglobin profiles of the subjects included in this study indicated that no patients presented with hemoglobinopathy. Labile plasmatic iron, ferritin, protein carbonyl, thiobarbituric acid-reactive substances (TBARS) and dichlorofluorescein diacetate oxidation were significantly higher (P < 0.05), whereas total thiol levels were significantly lower (P < 0.05) in transfused subjects compared to controls. Additionally, the activity of catalase, superoxide dismutase and glutathione peroxidase were significantly lower in the transfused subjects (P < 0.05). Antioxidant enzyme activities and total thiol levels were positively correlated (P < 0.05), and negatively correlated with the levels of protein carbonyl and TBARS (P < 0.05). In contrast, protein carbonyl and TBARS were positively correlated (P < 0.05). Altogether, these data confirm the involvement of OS in patients following therapy with repeated blood transfusions. CONCLUSION: Our data reveal that changes in OS markers are correlated with levels of labile plasmatic iron and ferritin and the number of transfusions. PMID:25254188

  9. Labile and recalcitrant organic matter utilization by river biofilm under increasing water temperature.

    PubMed

    Ylla, Irene; Romaní, Anna M; Sabater, Sergi

    2012-10-01

    Microbial biofilms in rivers contribute to the decomposition of the available organic matter which typically shows changes in composition and bioavailability due to their origin, seasonality, and watershed characteristics. In the context of global warming, enhanced biofilm organic matter decomposition would be expected but this effect could be specific when either a labile or a recalcitrant organic matter source would be available. A laboratory experiment was performed to mimic the effect of the predicted increase in river water temperature (+4 °C above an ambient temperature) on the microbial biofilm under differential organic matter sources. The biofilm microbial community responded to higher water temperature by increasing bacterial cell number, respiratory activity (electron transport system) and microbial extracellular enzymes (extracellular enzyme activity). At higher temperature, the phenol oxidase enzyme explained a large fraction of respiratory activity variation suggesting an enhanced microbial use of degradation products from humic substances. The decomposition of hemicellulose (β-xylosidase activity) seemed to be also favored by warmer conditions. However, at ambient temperature, the enzymes highly responsible for respiration activity variation were β-glucosidase and leu-aminopeptidase, suggesting an enhanced microbial use of polysaccharides and peptides degradation products. The addition of labile dissolved organic carbon (DOC; dipeptide plus cellobiose) caused a further augmentation of heterotrophic biomass and respiratory activity. The changes in the fluorescence index and the ratio Abs(250)/total DOC indicated that higher temperature accelerated the rates of DOC degradation. The experiment showed that the more bioavailable organic matter was rapidly cycled irrespective of higher temperature while degradation of recalcitrant substances was enhanced by warming. Thus, pulses of carbon at higher water temperature might have consequences for DOC

  10. Temporal Changes in Photochemically Labile DOM and Implications for Carbon Budgets in Peatland Aquatic Systems

    NASA Astrophysics Data System (ADS)

    Pickard, A.

    2015-12-01

    Aquatic systems in peatland catchments are subject to high loading of dissolved organic matter (DOM) from surrounding terrestrial environments. However the significance of photochemical transformation of DOM in peatland carbon budgets remains poorly constrained. In this study UV irradiation experiments were conducted on water samples collected over one year from two contrasting systems in Scotland: a stream draining a peatland with high levels of DOM and a reservoir draining a peat catchment with low levels of DOM. Further samples were collected from the high DOM system during two storm events. After experimental exposure, optical and chemical analyses were employed to determine photochemical lability of the DOM pool. At both sites irradiation-induced decreases in dissolved organic carbon (DOC) as a percentage of the total carbon pool were greatest in winter, suggesting that DOM was depleted in photo-reactive molecules in summer. Seasonal variability in DOC was high at the stream site and was positively correlated with CO₂ and CO photoproduction (r2 = 0.81 and 0.83, respectively; p<0.05). Lignin phenol analyses indicate considerable contribution of peat to the DOM pool at the stream site, particularly during summer. Whilst DOC concentrations did not vary greatly during storm events, UV-Vis absorbance indicators did, signifying changing DOM source material from activation of different hydrological pathways. The most photo-reactive DOM occurred 5-10 hours after peak discharge, suggesting that storms replenish photochemically labile DOM in headwater streams. Conservative estimates using data from this study suggest that up to 7% of the DOM pool of peatland streams can be lost (primarily as CO₂ and CO) upon exposure to 8 hours of environmentally representative UV irradiation. Further investigation in field campaigns under natural UV exposure are underway to assess the importance of photodegradation of DOM as a loss pathway of carbon based gases from aquatic systems.

  11. Poly(ortho ester amides): Acid-labile Temperature-responsive Copolymers for Potential Biomedical Applications

    PubMed Central

    Tang, Rupei; Palumbo, R. Noelle; Ji, Weihang; Wang, Chun

    2009-01-01

    A new, convenient pathway is developed to synthesize highly hydrolytically labile poly(ortho ester amide) (POEA) copolymers that overcomes some of the major weaknesses of the traditional methods of synthesizing poly(ortho esters) and their derivatives. A diamine monomer containing a built-in, stabilized ortho ester group was synthesized and was used for polycondensation with diacid esters, giving rise to a series of POEA copolymers with unique stimuli-responsive properties. The POEA undergoes temperature-responsive, reversible sol-gel phase transition in water. Phase diagrams of the POEA/H2O mixture reveal the concentration-dependent existence of different phases, including hydrogel and opaque or clear solution. Such behavior may be attributed to the temperature-dependent hydrogen-bonding involving the amide groups in the POEA backbone and hydrophobic interactions between POEA chains, and it is tunable by selecting diacid monomers with different chemical structures. The kinetics of POEA mass loss in physiological aqueous buffers and release of a model macromolecular drug, fluorescently labeled dextran, are nearly zero-order, suggesting predominantly surface-restricted polymer erosion. The rates of polymer erosion and drug release are much faster at pH 5.0 than pH 7.4. No cytotoxicity was found for the polymer extracts and the polymer degradation products at concentrations as high as 1 mg/ml. The normal morphology of fibroblasts cultured directly in contact with POEA films was not altered. These novel acid-labile temperature-responsive POEA copolymers may be potentially useful for a wide range of biomedical applications such as minimal invasive delivery of controlled-release drug formulations that respond to biological temperature and acidic-pH environments in cells and tissues. PMID:19281150

  12. Molecular insights into the microbial formation of marine dissolved organic matter: recalcitrant or labile?

    NASA Astrophysics Data System (ADS)

    Koch, B. P.; Kattner, G.; Witt, M.; Passow, U.

    2014-02-01

    The degradation of marine dissolved organic matter (DOM) is an important control variable in the global carbon cycle and dependent on the DOM composition. For our understanding of the kinetics of organic matter cycling in the ocean, it is therefore crucial to achieve a mechanistic and molecular understanding of its transformation processes. A long-term microbial experiment was performed to follow the production of non-labile DOM by marine bacteria. Two different glucose concentrations and dissolved algal exudates were used as substrates. We monitored the bacterial abundance, concentrations of dissolved and particulate organic carbon (DOC, POC), nutrients, amino acids, and transparent exopolymer particles (TEP) for two years. Ultrahigh resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS) allowed the molecular characterization of extracted DOM after 70 days and after ∼2 years of incubation. Although glucose was quickly degraded, a DOC background was generated in glucose incubations. Only 20% of the organic carbon from algal exudate was degraded within the 2 years of incubation. TEP, which are released by micro-organisms, were produced during glucose degradation but decreased within less than three weeks back to half of the maximum concentration and were below detection in all treatments after 2 years. The molecular analysis demonstrated that DOM generated during glucose degradation differed appreciably from DOM produced during the degradation of the algal exudates. Our results led to several conclusions: (i) Higher substrate levels result in a higher level of non-labile DOC which is an important prerequisite for carbon sequestration in the ocean; (ii) TEP are generated by bacteria but are also degraded rapidly, thus limiting their potential contribution to carbon sequestration; (iii) The molecular signatures of DOM derived from algal exudates or glucose after 70 days of incubation differed strongly from refractory DOM. After 2 years

  13. Enzyme-linked immunosorbent assay for Clostridium difficile toxin A.

    PubMed Central

    Lyerly, D M; Sullivan, N M; Wilkins, T D

    1983-01-01

    Antibodies against Clostridium difficile toxin A were purified by affinity chromatography from antiserum prepared against crude C. difficile toxin preparations. The affinity-purified antibody preparation was free of detectable amounts of antibodies to other C. difficile antigens, as demonstrated by crossed immunoelectrophoresis, and specifically neutralized the cytotoxicity of toxin A. An indirect enzyme-linked immunosorbent assay (ELISA) was subsequently developed using the antibody preparation for the specific detection of toxin A. The ELISA, which could detect 1 ng (5 ng/ml) of toxin A, was used to quantitate the toxin in the culture supernatant fluids of strains of C. difficile. The ELISA values for toxin A closely correlated with the toxin A and B cytotoxic titers of the supernatant fluids. In addition, toxin A was detected by ELISA in human fecal specimens from persons with antibiotic-associated colitis, demonstrating that this toxin is produced during C. difficile colitis. Images PMID:6338036

  14. Investigating the role of solanapyrone toxins in Ascochyta blight using toxin-deficient mutants of Asochyta rabiei

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ascochyta rabiei, the causal agent of Ascochyta blight of chickpea, produces solanapyrone toxins (solanapyrone A, B and C). However, very little is known about the genetics of toxin production and the role of the toxins in pathogenesis. Generating mutants deficient in the toxin biosynthesis would p...

  15. Mega assemblages of oligomeric aerolysin-like toxins stabilized by toxin-associating membrane proteins.

    PubMed

    Shimada, Hiroyasu; Kitada, Sakae

    2011-01-01

    Most β pore-forming toxins need to be oligomerized via receptors in order to form membrane pores. Though oligomerizing toxins frequently form SDS-resistant oligomers, it was questionable whether SDS-resistant oligomers reflected native functional toxin complexes. In order to elucidate the essence of the cytocidal assemblages, oligomers of aerolysin-like toxins, aerolysin, parasporin-2 and epsilon toxin, were examined with or without SDS. On Blue Native PAGE, each toxin, which had been solubilized from target cells with mild detergent, was a much larger complex (nearly 1 MDa) than the typical SDS-resistant oligomers (∼200 kDa). Size exclusion chromatography confirmed the huge toxin complexes. While a portion of the huge complexes were sensitive to proteases, SDS-resistant oligomers resist the proteolysis. Presumably the core toxin complexes remained intact while the cellular proteins were degraded. Moreover, intermediate complexes, which included no SDS-resistant oligomers, could be detected at lower temperatures. This study provides evidence for huge functional complexes of β pore-forming toxins and emphasizes their potential variance in composition.

  16. Toxic shock syndrome toxin-1, not α-toxin, mediated Bundaberg fatalities.

    PubMed

    Mueller, Elizabeth A; Merriman, Joseph A; Schlievert, Patrick M

    2015-12-01

    The 1928 Bundaberg disaster is one of the greatest vaccine tragedies in history. Of 21 children immunized with a diphtheria toxin-antitoxin preparation contaminated with Staphylococcus aureus, 18 developed life-threatening disease and 12 died within 48  h. Historically, the deaths have been attributed to α-toxin, a secreted cytotoxin produced by most S. aureus strains, yet the ability of the Bundaberg contaminant microbe to produce the toxin has never been verified. For the first time, the ability of the original strain to produce α-toxin and other virulence factors is investigated. The study investigates the genetic and regulatory loci mediating α-toxin expression by PCR and assesses production of the cytotoxin in vitro using an erythrocyte haemolysis assay. This analysis is extended to other secreted virulence factors produced by the strain, and their sufficiency to cause lethality in New Zealand white rabbits is determined. Although the strain possesses a wild-type allele for α-toxin, it must have a defective regulatory system, which is responsible for the strain's minimal α-toxin production. The strain encodes and produces staphylococcal superantigens, including toxic shock syndrome toxin-1 (TSST-1), which is sufficient to cause lethality in patients. The findings cast doubt on the belief that α-toxin is the major virulence factor responsible for the Bundaberg fatalities and point to the superantigen TSST-1 as the cause of the disaster.

  17. The Interactions of Human Neutrophils with Shiga Toxins and Related Plant Toxins: Danger or Safety?

    PubMed Central

    Brigotti, Maurizio

    2012-01-01

    Shiga toxins and ricin are well characterized similar toxins belonging to quite different biological kingdoms. Plant and bacteria have evolved the ability to produce these powerful toxins in parallel, while humans have evolved a defense system that recognizes molecular patterns common to foreign molecules through specific receptors expressed on the surface of the main actors of innate immunity, namely monocytes and neutrophils. The interactions between these toxins and neutrophils have been widely described and have stimulated intense debate. This paper is aimed at reviewing the topic, focusing particularly on implications for the pathogenesis and diagnosis of hemolytic uremic syndrome. PMID:22741061

  18. Shiga toxin-producing Escherichia coli.

    PubMed

    Smith, James L; Fratamico, Pina M; Gunther, Nereus W

    2014-01-01

    In the United States, it is estimated that non-O157 Shiga toxin-producing Escherichia coli (STEC) cause more illnesses than STEC O157:H7, and the majority of cases of non-O157 STEC infections are due to serogroups O26, O45, O103, O111, O121, and O145, referred to as the top six non-O157 STEC. The diseases caused by non-O157 STEC are generally milder than those induced by O157 STEC; nonetheless, non-O157 STEC strains have also been associated with serious illnesses such as hemorrhagic colitis and hemolytic uremic syndrome, as well as death. Ruminants, particularly cattle, are reservoirs for both O157 and non-O157 STEC, which are transmitted to humans by person-to-person or animal contact and by ingestion of food or water contaminated with animal feces. Improved strategies to control STEC colonization and shedding in cattle and contamination of meat and produce are needed. In general, non-O157 STEC respond to stresses such as acid, heat, and other stresses induced during food preparation similar to O157 STEC. Similar to O157:H7, the top six non-O157 STEC are classified as adulterants in beef by the USDA Food Safety and Inspection Service, and regulatory testing for these pathogens began in June 2012. Due to the genetic and phenotypic variability of non-O157 STEC strains, the development of accurate and reliable methods for detection and isolation of these pathogens has been challenging. Since the non-O157 STEC are responsible for a large portion of STEC-related illnesses, more extensive studies on their physiology, genetics, pathogenicity, and evolution are needed in order to develop more effective control strategies.

  19. How Parkinsonian Toxins Dysregulate the Autophagy Machinery

    PubMed Central

    Dagda, Ruben K.; Das Banerjee, Tania; Janda, Elzbieta

    2013-01-01

    Since their discovery, Parkinsonian toxins (6-hydroxydopamine, MPP+, paraquat, and rotenone) have been widely employed as in vivo and in vitro chemical models of Parkinson’s disease (PD). Alterations in mitochondrial homeostasis, protein quality control pathways, and more recently, autophagy/mitophagy have been implicated in neurotoxin models of PD. Here, we highlight the molecular mechanisms by which different PD toxins dysregulate autophagy/mitophagy and how alterations of these pathways play beneficial or detrimental roles in dopamine neurons. The convergent and divergent effects of PD toxins on mitochondrial function and autophagy/mitophagy are also discussed in this review. Furthermore, we propose new diagnostic tools and discuss how pharmacological modulators of autophagy/mitophagy can be developed as disease-modifying treatments for PD. Finally, we discuss the critical need to identify endogenous and synthetic forms of PD toxins and develop efficient health preventive programs to mitigate the risk of developing PD. PMID:24217228

  20. Bacterial Toxins as Pathogen Weapons Against Phagocytes

    PubMed Central

    do Vale, Ana; Cabanes, Didier; Sousa, Sandra

    2016-01-01

    Bacterial toxins are virulence factors that manipulate host cell functions and take over the control of vital processes of living organisms to favor microbial infection. Some toxins directly target innate immune cells, thereby annihilating a major branch of the host immune response. In this review we will focus on bacterial toxins that act from the extracellular milieu and hinder the function of macrophages and neutrophils. In particular, we will concentrate on toxins from Gram-positive and Gram-negative bacteria that manipulate cell signaling or induce cell death by either imposing direct damage to the host cells cytoplasmic membrane or enzymatically modifying key eukaryotic targets. Outcomes regarding pathogen dissemination, host damage and disease progression will be discussed. PMID:26870008

  1. [Treatment of wrinkles with botulinum toxin].

    PubMed

    Lanzl, I; Merté, R-L

    2007-09-01

    The use of botulinum toxin A for the treatment of wrinkles is increasing. Botulinum toxin A inhibits exocytosis of acetylcholine from 3 to 12 months, depending on the target tissue. Low-dose botulinum toxin A is used to smooth hyperkinetic facial lines. This is especially successful in the upper facial parts, since the target muscles (procerus, corrugator supracilii, frontalis, orbicularis oculi) all directly overlie the osseous structures of the face. This is not the case for the lower facial parts, and more side effects are encountered when treating, for example, wrinkles around the mouth. Contraindications to the use of botulinum toxin A are diseases affecting neuromuscular signal transduction, allergic reactions to components of the solution, therapy with aminoglycosides or acetylsalicylic acid prior to treatment, infections in the planned treatment area, and pregnancy and lactation. Alternative and complementary treatments include erbium-YAG or CO2 laser, as well as augmentation and surgical plastic procedures. PMID:17823803

  2. INVESTIGATOIN OF CYANOBACTERIA TOXINS IN WATER

    EPA Science Inventory

    Introduction:

    Approximately 80 alkaloid and cyclic peptide toxins produced by various freshwater and marine cyanobacteria (blue-green algae) have been identified and their structures determined. The U. S. Environmental Protection Agency has identified two neurotoxin alkalo...

  3. Bacterial Toxins as Pathogen Weapons Against Phagocytes.

    PubMed

    do Vale, Ana; Cabanes, Didier; Sousa, Sandra

    2016-01-01

    Bacterial toxins are virulence factors that manipulate host cell functions and take over the control of vital processes of living organisms to favor microbial infection. Some toxins directly target innate immune cells, thereby annihilating a major branch of the host immune response. In this review we will focus on bacterial toxins that act from the extracellular milieu and hinder the function of macrophages and neutrophils. In particular, we will concentrate on toxins from Gram-positive and Gram-negative bacteria that manipulate cell signaling or induce cell death by either imposing direct damage to the host cells cytoplasmic membrane or enzymatically modifying key eukaryotic targets. Outcomes regarding pathogen dissemination, host damage and disease progression will be discussed.

  4. Clostridium difficile and C. difficile Toxin Testing

    MedlinePlus

    ... C diff antigen; GDH Formal name: Clostridium difficile Culture; C. difficile Toxin, A and B; C. difficile Cytotoxin Assay; Glutamate Dehydrogenase Test Related tests: Stool Culture ; O&P At a Glance Test Sample The ...

  5. Nanoanalysis of the arthropod neuro-toxins

    PubMed Central

    Nakajima, Terumi

    2006-01-01

    Many kinds of venomous principles modulate physiological responses of mammalian signal transduction systems, on which they act selectively as enhancers, inhibitors or some other kind of effectors. These toxins become useful tools for physiological research. We have employed and characterized paralyzing toxins from the venom of spiders, insects and scorpions with a limited supply. We have developed rapid and sensitive mass spectrometric technology and applied for the identification of these toxins. Venom profiles are screened by MALDI-TOF fingerprinting analysis prior to purification of venomous components, then marked target toxins of small molecular mass (1000–5000) are characterized directly by means of mass spectrometric techniques such as Frit-FAB MS/MS, CID/PSD-TOF MS, Capil.-HPLC/Q-TOF MS/MS etc. PMID:25792792

  6. Bacterial Toxins as Pathogen Weapons Against Phagocytes.

    PubMed

    do Vale, Ana; Cabanes, Didier; Sousa, Sandra

    2016-01-01

    Bacterial toxins are virulence factors that manipulate host cell functions and take over the control of vital processes of living organisms to favor microbial infection. Some toxins directly target innate immune cells, thereby annihilating a major branch of the host immune response. In this review we will focus on bacterial toxins that act from the extracellular milieu and hinder the function of macrophages and neutrophils. In particular, we will concentrate on toxins from Gram-positive and Gram-negative bacteria that manipulate cell signaling or induce cell death by either imposing direct damage to the host cells cytoplasmic membrane or enzymatically modifying key eukaryotic targets. Outcomes regarding pathogen dissemination, host damage and disease progression will be discussed. PMID:26870008

  7. [Botulinum toxin in disabling dermatological diseases].

    PubMed

    Messikh, R; Atallah, L; Aubin, F; Humbert, P

    2009-05-01

    Botulinum toxin could represent nowadays a new treatment modality especially for cutaneous conditions in course of which conventional treatments remain unsuccessful. Besides palmar and plantar hyperhidrosis, botulinum toxin has demonstrated efficacy in different conditions associated with hyperhidrosis, such as dyshidrosis, multiple eccrine hidrocystomas, hidradenitis suppurativa, Frey syndrome, but also in different conditions worsened by hyperhidrosis such as Hailey-Hailey disease, Darier disease, inversed psoriasis, aquagenic palmoplantar keratoderma, pachyonychia congenital. Moreover, different cutaneous conditions associated with sensitive disorders and/or neurological involvements could benefit from botulinum toxin, for example anal fissures, leg ulcers, lichen simplex, notalgia paresthetica, vestibulitis. Endly, a case of cutis laxa was described where the patient was improved by cutaneous injections of botulinum toxin. PMID:19576479

  8. Tillage and rotational effects on exchangeable and enzyme-labile phosphorus forms in conventional and organic cropping systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The transformations of crop residues and bio-fertilizers used as primary sources of nutrients for organic grain and forage production are influenced by soil management practices. The effects of management of the near-surface zone on labile phosphorus (P) forms were studied in soil under three organ...

  9. Plant-Soil Relationships of Bromus tectorum L.: Interactions among Labile Carbon Additions, Soil Invasion Status, and Fertilizer.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Invasion of western North America by the annual exotic grass Bromus tectorum L. (cheatgrass) has been an ecological disaster. High soil bioavailability of nitrogen is a contributing factor in the invasive potential of B. tectorum. Application of labile carbon sources to the soil can immobilize soil ...

  10. On the Labile Memory Buffer in the Attentional Blink: Masking the T2 Representation by Onset Transients Mediates the AB

    ERIC Educational Resources Information Center

    Jannati, Ali; Spalek, Thomas M.; Di Lollo, Vincent

    2011-01-01

    Report of a second target (T2) is impaired when presented within 500 ms of the first (T1). This attentional blink (AB) is known to cause a delay in T2 processing during which T2 must be stored in a labile memory buffer. We explored the buffer's characteristics using different types of masks after T2. These characteristics were inferred by…

  11. Thermal Analysis of Labile Trace Elements in CM and CV Carbonaceous Chondrites Using Inductively Coupled Plasma-Mass Spectrometry

    NASA Technical Reports Server (NTRS)

    Lauretta, D. S.; Klaue, B.; Blum, J. D.; Buseck, P. R.

    2001-01-01

    We developed a technique to measure the thermal release profiles of a suite of labile elements (Zn, As, Se, Cd, In, Sn, Sb, Te, Pt, Hg, Au, Tl, Pb, Bi). Conclusions are reached about the behavior of each element during parent-body alteration. Additional information is contained in the original extended abstract.

  12. A Longitudinal Study of Emotion Regulation, Emotion Lability-Negativity, and Internalizing Symptomatology in Maltreated and Nonmaltreated Children

    ERIC Educational Resources Information Center

    Kim-Spoon, Jungmeen; Cicchetti, Dante; Rogosch, Fred A.

    2013-01-01

    The longitudinal contributions of emotion regulation and emotion lability-negativity to internalizing symptomatology were examined in a low-income sample (171 maltreated and 151 nonmaltreated children, from age 7 to 10 years). Latent difference score models indicated that for both maltreated and nonmaltreated children, emotion regulation was a…

  13. An anaerobic incubation study of metal lability in drinking water treatment residue with implications for practical reuse.

    PubMed

    Wang, Changhui; Yuan, Nannan; Pei, Yuansheng

    2014-06-15

    Drinking water treatment residue (WTR) is an inevitable by-product generated during the treatment of drinking water with coagulating agents. The beneficial reuse of WTR as an amendment for environmental remediation has attracted growing interest. In this work, we investigated the lability of Al, As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Sr, V and Zn in Fe/Al hydroxide-comprised WTR based on a 180-day anaerobic incubation test using fractionation, in vitro digestion and a toxicity characteristic leaching procedure. The results indicated that most metals in the WTR were stable during anaerobic incubation and that the WTR before and after incubation could be considered non-hazardous in terms of leachable metal contents according to US EPA Method 1311. However, the lability of certain metals in the WTR after incubation increased substantially, especially Mn, which may be due to the reduction effect. Therefore, although there is no evidence presented to restrict the use of WTR in the field, the lability of metals (especially Mn) in WTR requires further assessment prior to field application. In addition, fractionation (e.g., BCR) is recommended for use to determine the potential lability of metals under various conditions.

  14. In situ measurements of labile Al and Mn in acid mine drainage using diffusive gradients in thin films.

    PubMed

    Søndergaard, Jens

    2007-08-15

    The technique of diffusive gradients in thin films (DGT) can be used for in situ measurements of labile metal species in water, but the application for this method on acid mine drainage (AMD) is complicated due to reduced sampler adsorption of metals at low pH. This study evaluates the use of DGT on labile Al and Mn in AMD (pH 3.1-4.2). DGT measurements were performed both in standard solutions in the laboratory and in situ in the field. Laboratory results show that DGT can be used in water with pH as low as 3.0 for Al and 4.0 for Mn without correcting for reduced adsorption. Below pH 4.0, the adsorption of Mn showed a linearly decrease with pH to approximately 55% at pH 3.0. Taking this correction into account revealed that 84-100% of the total dissolved Al and Mn measured in the field was DGT-labile. Measurements using DGT agreed well with predictions using the speciation program WHAM VI. This study shows that the use of DGT can be extended below the previously reported pH working range for Al, and for Mn using a simple linear correction with respect to pH, and demonstrates that the technique can be applied for monitoring time-integrated labile metal concentrations at AMD sites. PMID:17620010

  15. Emotional Lability in Children and Adolescents with Attention Deficit/Hyperactivity Disorder (ADHD): Clinical Correlates and Familial Prevalence

    ERIC Educational Resources Information Center

    Sobanski, Esther; Banaschewski, Tobias; Asherson, Philip; Buitelaar, Jan; Chen, Wai; Franke, Barbara; Holtmann, Martin; Krumm, Bertram; Sergeant, Joseph; Sonuga-Barke, Edmund; Stringaris, Argyris; Taylor, Eric; Anney, Richard; Ebstein, Richard P.; Gill, Michael; Miranda, Ana; Mulas, Fernando; Oades, Robert D.; Roeyers, Herbert; Rothenberger, Aribert; Steinhausen, Hans-Christoph; Faraone, Stephen V.

    2010-01-01

    Background: The goal of this study was to investigate the occurrence, severity and clinical correlates of emotional lability (EL) in children with attention deficit/hyperactivity disorder (ADHD), and to examine factors contributing to EL and familiality of EL in youth with ADHD. Methods: One thousand, one hundred and eighty-six children with ADHD…

  16. Detection of antibodies against botulinum toxins.

    PubMed

    Sesardic, Dorothea; Jones, Russell G A; Leung, Tong; Alsop, Toni; Tierney, Robert

    2004-03-01

    After immunisation with botulinum vaccine, antibodies to multiple epitopes are produced. Only some of these will have the capacity to neutralise the toxin activity. In fact, the ability of toxoid vaccine to induce toxin neutralising antibodies has provided the basis for the use of therapeutic antitoxins and immunoglobulins for the prophylaxis and treatment of diseases caused by bacterial toxins. Increasing indications for the chronic use of botulinum toxin for therapy have inevitably resulted in concern for patients becoming unresponsive because of the presence of circulating toxin-specific antibodies. Highly sensitive and relevant assays to detect only clinically relevant toxin neutralising antibodies are essential. Although immunoassays often provide the sensitivity, their relevance and specificity is often questioned. The mouse protection LD(50) bioassay is considered most relevant but can often only detect 10 mIU/ml of antitoxin. This sensitivity, although sufficient for confirming protective immunity, is inadequate for patients undergoing toxin therapy. An intramuscular paralysis assay improves the sensitivity to ca. 1 mIU/ml, and a mouse ex vivo diaphragm assay, with sensitivity of < 0.5 mIU/ml, is the most sensitive functional assay to date for this purpose. Alternative approaches for the detection of antibodies to botulinum toxin have included in vitro endopeptidase activity neutralisation. Unlike any other functional assay, this approach is not reliant on serotype-specific antibodies for specificity. Most recent promising developments are focused on cellular assays utilising primary rat embryonic cord cells or more conveniently in vitro differentiated established cell lines such as human neuroblastoma cells.

  17. Toxicological Perspective on Climate Change: Aquatic Toxins.

    PubMed

    Botana, Luis M

    2016-04-18

    In recent years, our group and several others have been describing the presence of new, not previously reported, toxins of high toxicity in vectors that may reach the human food chain. These include tetrodotoxin in gastropods in the South of Europe, ciguatoxin in fish in the South of Spain, palytoxin in mussels in the Mediterranean Sea, pinnatoxin all over Europe, and okadaic acid in the south of the U.S. There seem to be new marine toxins appearing in areas that are heavy producers of seafood, and this is a cause of concern as most of these new toxins are not included in current legislation and monitoring programs. Along with the new toxins, new chemical analogues are being reported. The same phenomenom is being recorded in freshwater toxins, such as the wide appearance of cylindrospermopsin and the large worldwide increase of microcystin. The problem that this phenomenon, which may be linked to climate warming, poses for toxicologists is very important not only because there is a lack of chronic studies and an incomplete comprehension of the mechanism driving the production of these toxins but also because the lack of a legal framework for them allows many of these toxins to reach the market. In some cases, it is very difficult to control these toxins because there are not enough standards available, they are not always certified, and there is an insufficient understanding of the toxic equivalency factors of the different analogues in each group. All of these factors have been revealed and grouped through the massive increase in the use of LC-MS as a monitoring tool, legally demanded, creating more toxicological problems. PMID:26958981

  18. ADP-ribosylation by cholera toxin: functional analysis of a cellular system that stimulates the enzymic activity of cholera toxin fragment A/sub 1/

    SciTech Connect

    Gill, D.M.; Coburn, J.

    1987-10-06

    The authors have clarified relationships between cholera toxin, cholera toxin substrates, a membrane protein S that is required for toxin activity, and a soluble protein CF that is needed for the function of S. The toxin has little intrinsic ability to catalyze ADP-ribosylations unless it encounters the active form of the S protein, which is S liganded to GTP or to a GTP analogue. In the presence of CF, S x GTP forms readily, though reversibly, but a more permanent active species, S-guanosine 5'-O-(3-thiotriphosphate) (S x GTP..gamma..S), forms over a period of 10-15 min at 37/sup 0/C. Both guanosine 5'-O-(2-thiodiphosphate) and GTP block this quasi-permanent activation. Some S x GTP..gamma..S forms in membranes that are exposed to CF alone and then to GTP..gamma..S, with a wash in between, and it is possible that CF facilitates a G nucleotide exchange. S x GTP..gamma..S dissolved by nonionic detergents persists in solution and can be used to support the ADP-ribosylation of nucleotide-free substrates. In this circumstance, added guanyl nucleotides have no further effect. This active form of S is unstable, especially when heated, but the thermal inactivation above 45/sup 0/C is decreased by GTP..gamma..S. Active S is required equally for the ADP-ribosylation of all of cholera toxin's protein substrates, regardless of whether they bind GTP or not. They suggest that active S interacts directly with the enzymic A/sub 1/ fragments of cholera toxin and not with any toxin substrate. The activation and activity of S are independent of the state, or even the presence, of adenylate cyclase and seem to be involved with the cyclase system only via cholera toxin. S is apparently not related by function to certain other GTP binding proteins, including p21/sup ras/, and appears to be a new GTP binding protein whose physiologic role remains to be identified.

  19. Sea Anemone Toxins Affecting Potassium Channels

    NASA Astrophysics Data System (ADS)

    Diochot, Sylvie; Lazdunski, Michel

    The great diversity of K+ channels and their wide distribution in many tissues are associated with important functions in cardiac and neuronal excitability that are now better understood thanks to the discovery of animal toxins. During the past few decades, sea anemones have provided a variety of toxins acting on voltage-sensitive sodium and, more recently, potassium channels. Currently there are three major structural groups of sea anemone K+ channel (SAK) toxins that have been characterized. Radioligand binding and electrophysiological experiments revealed that each group contains peptides displaying selective activities for different subfamilies of K+ channels. Short (35-37 amino acids) peptides in the group I display pore blocking effects on Kv1 channels. Molecular interactions of SAK-I toxins, important for activity and binding on Kv1 channels, implicate a spot of three conserved amino acid residues (Ser, Lys, Tyr) surrounded by other less conserved residues. Long (58-59 amino acids) SAK-II peptides display both enzymatic and K+ channel inhibitory activities. Medium size (42-43 amino acid) SAK-III peptides are gating modifiers which interact either with cardiac HERG or Kv3 channels by altering their voltage-dependent properties. SAK-III toxins bind to the S3C region in the outer vestibule of Kv channels. Sea anemones have proven to be a rich source of pharmacological tools, and some of the SAK toxins are now useful drugs for the diagnosis and treatment of autoimmune diseases.

  20. Toxin-Antitoxin Systems of Staphylococcus aureus.

    PubMed

    Schuster, Christopher F; Bertram, Ralph

    2016-05-05

    Toxin-antitoxin (TA) systems are small genetic elements found in the majority of prokaryotes. They encode toxin proteins that interfere with vital cellular functions and are counteracted by antitoxins. Dependent on the chemical nature of the antitoxins (protein or RNA) and how they control the activity of the toxin, TA systems are currently divided into six different types. Genes comprising the TA types I, II and III have been identified in Staphylococcus aureus. MazF, the toxin of the mazEF locus is a sequence-specific RNase that cleaves a number of transcripts, including those encoding pathogenicity factors. Two yefM-yoeB paralogs represent two independent, but auto-regulated TA systems that give rise to ribosome-dependent RNases. In addition, omega/epsilon/zeta constitutes a tripartite TA system that supposedly plays a role in the stabilization of resistance factors. The SprA1/SprA1AS and SprF1/SprG1 systems are post-transcriptionally regulated by RNA antitoxins and encode small membrane damaging proteins. TA systems controlled by interaction between toxin protein and antitoxin RNA have been identified in S. aureus in silico, but not yet experimentally proven. A closer inspection of possible links between TA systems and S. aureus pathophysiology will reveal, if these genetic loci may represent druggable targets. The modification of a staphylococcal TA toxin to a cyclopeptide antibiotic highlights the potential of TA systems as rather untapped sources of drug discovery.

  1. Toxin-Antitoxin Systems of Staphylococcus aureus

    PubMed Central

    Schuster, Christopher F.; Bertram, Ralph

    2016-01-01

    Toxin-antitoxin (TA) systems are small genetic elements found in the majority of prokaryotes. They encode toxin proteins that interfere with vital cellular functions and are counteracted by antitoxins. Dependent on the chemical nature of the antitoxins (protein or RNA) and how they control the activity of the toxin, TA systems are currently divided into six different types. Genes comprising the TA types I, II and III have been identified in Staphylococcus aureus. MazF, the toxin of the mazEF locus is a sequence-specific RNase that cleaves a number of transcripts, including those encoding pathogenicity factors. Two yefM-yoeB paralogs represent two independent, but auto-regulated TA systems that give rise to ribosome-dependent RNases. In addition, omega/epsilon/zeta constitutes a tripartite TA system that supposedly plays a role in the stabilization of resistance factors. The SprA1/SprA1AS and SprF1/SprG1 systems are post-transcriptionally regulated by RNA antitoxins and encode small membrane damaging proteins. TA systems controlled by interaction between toxin protein and antitoxin RNA have been identified in S. aureus in silico, but not yet experimentally proven. A closer inspection of possible links between TA systems and S. aureus pathophysiology will reveal, if these genetic loci may represent druggable targets. The modification of a staphylococcal TA toxin to a cyclopeptide antibiotic highlights the potential of TA systems as rather untapped sources of drug discovery. PMID:27164142

  2. Tetra- versus Pentavalent Inhibitors of Cholera Toxin**

    PubMed Central

    Fu, Ou; Pukin, Aliaksei V; van Ufford, H C Quarles; Branson, Thomas R; Thies-Weesie, Dominique M E; Turnbull, W Bruce; Visser, Gerben M; Pieters, Roland J

    2015-01-01

    The five B-subunits (CTB5) of the Vibrio cholerae (cholera) toxin can bind to the intestinal cell surface so the entire AB5 toxin can enter the cell. Simultaneous binding can occur on more than one of the monosialotetrahexosylganglioside (GM1) units present on the cell surface. Such simultaneous binding arising from the toxins multivalency is believed to enhance its affinity. Thus, blocking the initial attachment of the toxin to the cell surface using inhibitors with GM1 subunits has the potential to stop the disease. Previously we showed that tetravalent GM1 molecules were sub-nanomolar inhibitors of CTB5. In this study, we synthesized a pentavalent version and compared the binding and potency of penta- and tetravalent cholera toxin inhibitors, based on the same scaffold, for the first time. The pentavalent geometry did not yield major benefits over the tetravalent species, but it was still a strong inhibitor, and no major steric clashes occurred when binding the toxin. Thus, systems which can adopt more geometries, such as those described here, can be equally potent, and this may possibly be due to their ability to form higher-order structures or simply due to more statistical options for binding. PMID:26478842

  3. Development and fabrication of heat-sterilizable inhalation therapy equipment

    NASA Technical Reports Server (NTRS)

    Irons, A. S.

    1974-01-01

    The development of a completely heat sterilizable intermittent positive pressure breathing (IPPB) ventilator in an effort to reduce the number of hospital acquired infections is reported. After appropriate changes in materials and design were made, six prototype units were fabricated and were successfully field tested in local hospitals. Most components of the modified ventilators are compatible with existing machines. In all but a few instances, such as installation of bacteria-retentive filters and a modified venturi, the change over from non-heat-sterilizable to sterilizable units was accomplished by replacement of heat labile materials with heat stable materials.

  4. Inhibition of maize histone deacetylases by HC toxin, the host-selective toxin of Cochliobolus carbonum.

    PubMed Central

    Brosch, G; Ransom, R; Lechner, T; Walton, J D; Loidl, P

    1995-01-01

    HC toxin, the host-selective toxin of the maize pathogen Cochliobolus carbonum, inhibited maize histone deacetylase (HD) at 2 microM. Chlamydocin, a related cyclic tetrapeptide, also inhibited HD activity. The toxins did not affect histone acetyltransferases. After partial purification of histone deacetylases HD1-A, HD1-B, and HD2 from germinating maize embryos, we demonstrated that the different enzymes were similarly inhibited by the toxins. Inhibitory activities were reversibly eliminated by treating toxins with 2-mercaptoethanol, presumably by modifying the carbonyl group of the epoxide-containing amino acid Aeo (2-amino-9,10-epoxy-8-oxodecanoic acid). Kinetic studies revealed that inhibition of HD was of the uncompetitive type and reversible. HC toxin, in which the epoxide group had been hydrolyzed, completely lost its inhibitory activity; when the carbonyl group of Aeo had been reduced to the corresponding alcohol, the modified toxin was less active than native toxin. In vivo treatment of embryos with HC toxin caused the accumulation of highly acetylated histone H4 subspecies and elevated acetate incorporation into H4 in susceptible-genotype embryos but not in the resistant genotype. HDs from chicken and the myxomycete Physarum polycephalum were also inhibited, indicating that the host selectivity of HC toxin is not determined by its inhibitory effect on HD. Consistent with these results, we propose a model in which HC toxin promotes the establishment of pathogenic compatibility between C. carbonum and maize by interfering with reversible histone acetylation, which is implicated in the control of fundamental cellular processes, such as chromatin structure, cell cycle progression, and gene expression. PMID:8535144

  5. Rapid decomposition of labile soil organic matter inputs obscures sensitivity of heterotrophic respiration to temperature: A model analysis.

    NASA Astrophysics Data System (ADS)

    Post, W. M.; Gu, L.; King, A. W.

    2003-12-01

    Labile carbon, although often a small fraction of soil organic matter (SOM), significantly affects heterotrophic respiration at short time scales because of its rapid decomposition. However, in the current literature, most soil respiration measurements are interpreted without simultaneous information on labile carbon pool dynamics. Sensitivity of soil respiration to temperature is routinely derived directly from field observations and such relationships have been used to extrapolate effects of global change (e.g. warming) on the carbon emission from SOM. Here we used a multi-pool SOM model to demonstrate the impacts of seasonal fluctuations in labile carbon pools. Labile carbon pool sizes varied widely in response to seasonal changes in representative plant material inputs and temperature even though the model was operating at an equilibrium state (in terms of annual means). Convolution of the dynamics of fast turnover carbon pools and temporal progression in temperature led to misrepresentation and misinterpretation of the heterotrophic respiration - temperature relationships estimated from bulk soil CO2 exchanges. Temperature sensitivity was overestimated when the variations of labile carbon pools and temperature were in phase and underestimated when they were out of phase. Furthermore, with normally used observation time windows (weeks to a year), temperature sensitivity was more likely to be underestimated. A distortion of temperature sensitivity (Q10) from 2 (actual, sensitive dependence on temperature) to nearly 1 (false, no dependence on temperature) was shown. Our analysis indicates that cautions must be taken when soil respiration - temperature relationships are evaluated based on bulk soil observations and that sensitivity of soil respiration to temperature estimated directly under field conditions should not be used to predict future carbon cycle climate feedbacks.

  6. Multivariate Statistical Analysis of Labile Trace Elements in H Chondrites: Evidence for Meteoroid Streams

    NASA Astrophysics Data System (ADS)

    Wolf, S. F.; Lipschutz, M. E.

    1992-07-01

    Differences have been observed between meteorite populations with vastly different terrestrial ages, i.e. Antarctic and non-Antarctic meteorite populations (Koeberl and Cassidy, 1991 and references therein). Comparisons of labile trace element contents (Wolf and Lipschutz, 1992) and induced TL parameters (Benoit and Sears, 1992) in samples from Victoria Land and Queen Maud Land, populations which also differ in mean terrestrial age (Nishiizumi et al, 1989), show significant differences consistent with different average thermal histories. These differences are consistent with the proposition that the flux of meteoritic material to Earth varied temporally. Variations in the flux of meteoritic material over time scales of 10^5 10^6 y require the existence of undispersed streams of meteoroids of asteroidal origin which were initially disputed by Wetherill ( 1986) but have since been observed (Olsson-Steele, 1988; Oberst, 1989; Halliday et al. 1990). Orbital evidence for meteoroid and asteroid streams has been independently obtained by others, particularly Halliday et al.(1990) and Drummond (1991). A group of H chondrites of various petrographic types and diverse CRE ages that yielded 16 falls from 1855 until 1895 in the month of May has been proposed to be two co-orbital meteoroid streams with a common source (R. T. Dodd, personal communication). Compositional evidence of a preterrestrial association of the proposed stream members, if it exists, might be observed in the most sensitive indicators of genetic thermal history, the labile trace elements. We report RNAA data for the concentrations of 14 trace elements, mostly labile ones, (Ag, Au, Bi, Cd, Cs, Co, Ga, In, Rb, Sb, Se, Te, Tl, and Zn) in H4-6 ordinary chondrites. Variance of elemental concentrations within a subpopulation, the members of a proposed co-orbital meteorite stream for example, could be expected to be smaller than the variance for the entire population. We utilize multivariate linear regression and

  7. A biomimetic nanosponge that absorbs pore-forming toxins

    NASA Astrophysics Data System (ADS)

    Hu, Che-Ming J.; Fang, Ronnie H.; Copp, Jonathan; Luk, Brian T.; Zhang, Liangfang

    2013-05-01

    Detoxification treatments such as toxin-targeted anti-virulence therapy offer ways to cleanse the body of virulence factors that are caused by bacterial infections, venomous injuries and biological weaponry. Because existing detoxification platforms such as antisera, monoclonal antibodies, small-molecule inhibitors and molecularly imprinted polymers act by targeting the molecular structures of toxins, customized treatments are required for different diseases. Here, we show a biomimetic toxin nanosponge that functions as a toxin decoy in vivo. The nanosponge, which consists of a polymeric nanoparticle core surrounded by red blood cell membranes, absorbs membrane-damaging toxins and diverts them away from their cellular targets. In a mouse model, the nanosponges markedly reduce the toxicity of staphylococcal alpha-haemolysin (α-toxin) and thus improve the survival rate of toxin-challenged mice. This biologically inspired toxin nanosponge presents a detoxification treatment that can potentially treat a variety of injuries and diseases caused by pore-forming toxins.

  8. A biomimetic nanosponge that absorbs pore-forming toxins.

    PubMed

    Hu, Che-Ming J; Fang, Ronnie H; Copp, Jonathan; Luk, Brian T; Zhang, Liangfang

    2013-05-01

    Detoxification treatments such as toxin-targeted anti-virulence therapy offer ways to cleanse the body of virulence factors that are caused by bacterial infections, venomous injuries and biological weaponry. Because existing detoxification platforms such as antisera, monoclonal antibodies, small-molecule inhibitors and molecularly imprinted polymers act by targeting the molecular structures of toxins, customized treatments are required for different diseases. Here, we show a biomimetic toxin nanosponge that functions as a toxin decoy in vivo. The nanosponge, which consists of a polymeric nanoparticle core surrounded by red blood cell membranes, absorbs membrane-damaging toxins and diverts them away from their cellular targets. In a mouse model, the nanosponges markedly reduce the toxicity of staphylococcal alpha-haemolysin (α-toxin) and thus improve the survival rate of toxin-challenged mice. This biologically inspired toxin nanosponge presents a detoxification treatment that can potentially treat a variety of injuries and diseases caused by pore-forming toxins.

  9. Mechanism of Gene Regulation by a Staphylococcus aureus Toxin

    PubMed Central

    Joo, Hwang-Soo; Chatterjee, Som S.; Villaruz, Amer E.; Dickey, Seth W.; Tan, Vee Y.; Chen, Yan; Sturdevant, Daniel E.; Ricklefs, Stacy M.

    2016-01-01

    ABSTRACT The virulence of many bacterial pathogens, including the important human pathogen Staphylococcus aureus, depends on the secretion of frequently large amounts of toxins. Toxin production involves the need for the bacteria to make physiological adjustments for energy conservation. While toxins are primarily targets of gene regulation, such changes may be accomplished by regulatory functions of the toxins themselves. However, mechanisms by which toxins regulate gene expression have remained poorly understood. We show here that the staphylococcal phenol-soluble modulin (PSM) toxins have gene regulatory functions that, in particular, include inducing expression of their own transport system by direct interference with a GntR-type repressor protein. This capacity was most pronounced in PSMs with low cytolytic capacity, demonstrating functional specification among closely related members of that toxin family during evolution. Our study presents a molecular mechanism of gene regulation by a bacterial toxin that adapts bacterial physiology to enhanced toxin production. PMID:27795396

  10. Red tide (Ptychodiscus brevis) toxin aerosols: a review.

    PubMed

    Pierce, R H

    1986-01-01

    Advances in knowledge concerning red tide toxin aerosols (airborne) of the Florida red tide organism, Ptychodiscus brevis, have not kept pace with information about waterborne toxins. This review provides a summary of current knowledge regarding the characterization, effect and production of red tide toxin aerosols. Insight into the chemical characterization and toxic effects of aerosolized toxins is provided from investigations of toxins extracted from natural blooms, as well as from laboratory cultures, of P. brevis. This information is used in conjunction with the few studies that have been performed on toxin aerosols to consider toxic effects. The production of aerosolized toxins is considered through studies of jet drop aerosol formation from bursting bubbles. Existing information suggests that aerosolized red tide toxins may be the same chemicals as those extracted from laboratory cultures, with one of the toxins having a greater respiratory effect than others.

  11. Clostridium perfringens Delta-Toxin Induces Rapid Cell Necrosis.

    PubMed

    Seike, Soshi; Miyamoto, Kazuaki; Kobayashi, Keiko; Takehara, Masaya; Nagahama, Masahiro

    2016-01-01

    Clostridium perfringens delta-toxin is a β-pore-forming toxin and a putative pathogenic agent of C. perfringens types B and C. However, the mechanism of cytotoxicity of delta-toxin remains unclear. Here, we investigated the mechanisms of cell death induced by delta-toxin in five cell lines (A549, A431, MDCK, Vero, and Caco-2). All cell lines were susceptible to delta-toxin. The toxin caused rapid ATP depletion and swelling of the cells. Delta-toxin bound and formed oligomers predominantly in plasma membrane lipid rafts. Destruction of the lipid rafts with methyl β-cyclodextrin inhibited delta-toxin-induced cytotoxicity and ATP depletion. Delta-toxin caused the release of carboxyfluorescein from sphingomyelin-cholesterol liposomes and formed oligomers; toxin binding to the liposomes declined with decreasing cholesterol content in the liposomes. Flow cytometric assays with annexin V and propidium iodide revealed that delta-toxin treatment induced an elevation in the population of annexin V-negative and propidium iodide-positive cells. Delta-toxin did not cause the fragmentation of DNA or caspase-3 activation. Furthermore, delta-toxin caused damage to mitochondrial membrane permeability and cytochrome c release. In the present study, we demonstrate that delta-toxin produces cytotoxic activity through necrosis.

  12. Clostridium perfringens Delta-Toxin Induces Rapid Cell Necrosis

    PubMed Central

    Seike, Soshi; Miyamoto, Kazuaki; Kobayashi, Keiko; Takehara, Masaya; Nagahama, Masahiro

    2016-01-01

    Clostridium perfringens delta-toxin is a β-pore-forming toxin and a putative pathogenic agent of C. perfringens types B and C. However, the mechanism of cytotoxicity of delta-toxin remains unclear. Here, we investigated the mechanisms of cell death induced by delta-toxin in five cell lines (A549, A431, MDCK, Vero, and Caco-2). All cell lines were susceptible to delta-toxin. The toxin caused rapid ATP depletion and swelling of the cells. Delta-toxin bound and formed oligomers predominantly in plasma membrane lipid rafts. Destruction of the lipid rafts with methyl β-cyclodextrin inhibited delta-toxin-induced cytotoxicity and ATP depletion. Delta-toxin caused the release of carboxyfluorescein from sphingomyelin-cholesterol liposomes and formed oligomers; toxin binding to the liposomes declined with decreasing cholesterol content in the liposomes. Flow cytometric assays with annexin V and propidium iodide revealed that delta-toxin treatment induced an elevation in the population of annexin V-negative and propidium iodide-positive cells. Delta-toxin did not cause the fragmentation of DNA or caspase-3 activation. Furthermore, delta-toxin caused damage to mitochondrial membrane permeability and cytochrome c release. In the present study, we demonstrate that delta-toxin produces cytotoxic activity through necrosis. PMID:26807591

  13. Clostridium perfringens Delta-Toxin Induces Rapid Cell Necrosis.

    PubMed

    Seike, Soshi; Miyamoto, Kazuaki; Kobayashi, Keiko; Takehara, Masaya; Nagahama, Masahiro

    2016-01-01

    Clostridium perfringens delta-toxin is a β-pore-forming toxin and a putative pathogenic agent of C. perfringens types B and C. However, the mechanism of cytotoxicity of delta-toxin remains unclear. Here, we investigated the mechanisms of cell death induced by delta-toxin in five cell lines (A549, A431, MDCK, Vero, and Caco-2). All cell lines were susceptible to delta-toxin. The toxin caused rapid ATP depletion and swelling of the cells. Delta-toxin bound and formed oligomers predominantly in plasma membrane lipid rafts. Destruction of the lipid rafts with methyl β-cyclodextrin inhibited delta-toxin-induced cytotoxicity and ATP depletion. Delta-toxin caused the release of carboxyfluorescein from sphingomyelin-cholesterol liposomes and formed oligomers; toxin binding to the liposomes declined with decreasing cholesterol content in the liposomes. Flow cytometric assays with annexin V and propidium iodide revealed that delta-toxin treatment induced an elevation in the population of annexin V-negative and propidium iodide-positive cells. Delta-toxin did not cause the fragmentation of DNA or caspase-3 activation. Furthermore, delta-toxin caused damage to mitochondrial membrane permeability and cytochrome c release. In the present study, we demonstrate that delta-toxin produces cytotoxic activity through necrosis. PMID:26807591

  14. Toxin from skin of frogs of the genus Atelopus: differentiation from Dendrobatid toxins.

    PubMed

    Fuhrman, F A; Fuhrman, G J; Mosher, H S

    1969-09-26

    A potent, dialyzable toxin (atelopidtoxin) occurs in the skin of frogs of the genus Atelopus. A concentrate of atelopidtoxin from Atelopus zeteki has an LD(50) in mice of 16 micrograms per kilogram. It differs from batrachotoxin, tetrodotoxin, and saxitoxin, the only known nonprotein substances of greater toxicity, as well as from all toxins previously isolated from amphibia. PMID:5807965

  15. Preservation of labile organic matter in soils of drained thaw lakes in Northern Alaska

    NASA Astrophysics Data System (ADS)

    Mueller, Carsten W.; Rethemeyer, Janet; Kao-Kniffin, Jenny; Löppmann, Sebastian; Hinkel, Kenneth; Bockheim, James

    2014-05-01

    A large number of studies predict changing organic matter (OM) dynamics in arctic soils due to global warming. In contrast to rather slowly altering bulk soil properties, single soil organic matter (SOM) fractions can provide a more detailed picture of the dynamics of differently preserved SOM pools in climate sensitive arctic regions. By the study of the chemical composition of such distinctive SOM fractions using nuclear magnetic resonance spectroscopy (NMR) together with radiocarbon analyses it is possible to evaluate the stability of the major OM pools. Approximately 50-75% of Alaska's Arctic Coastal Plain is covered with thaw lakes and drained thaw lakes that follow a 5,000 yr cycle of development (between creation and final drainage), thus forming a natural soil chronosequence. The drained thaw lakes offer the possibility to study SOM dynamics affected by permafrost processes over millennial timescales. In April 2010 we sampled 16 soil cores (including the active and permanent layer) reaching from young drained lakes (0-50 years since drainage) to ancient drained lakes (3000-5500 years since drainage). Air dried soil samples from soil horizons of the active and permanent layer were subjected to density fractionation in order to differentiate particulate OM and mineral associated OM. The chemical composition of the SOM fractions was analyzed by 13C CPMAS NMR spectroscopy. For a soil core of a young and an ancient drained thaw lake basin we also analyzed the 14C content. For the studied soils we can show that up to over 25 kg OC per square meter are stored mostly as labile, easily degradable organic matter rich in carbohydrates. In contrast only 10 kg OC per square meter were sequestered as presumably more stable mineral associated OC dominated by aliphatic compounds. Comparable to soils of temperate regions, we found small POM (< 20 µm) occluded in aggregated soil structures which differed in the chemical composition from larger organic particles. This was

  16. Fluxes of phytopigments and labile organic matter to the deep ocean in the NE Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Fabiano, M.; Pusceddu, A.; Dell'Anno, A.; Armeni, M.; Vanucci, S.; Lampitt, R. S.; Wolff, G. A.; Danovaro, R.

    Downward fluxes of labile organic matter (phytopigments, proteins and carbohydrates) were measured between September 1996 and August 1998 at three depths 1000 m, 3000 m and 4700 m (c. 100 mab) over the Porcupine Abyssal Plain (PAP, NE Atlantic), to provide detailed information on the biochemical characteristics of organic inputs to the deep sea. Temporal changes in the carbohydrate and protein fluxes were compared to carbohydrate and protein contents of the surficial sediment on the seabed beneath the traps at 4850 m depth. Fluxes of carbohydrate, protein and phytopigments (chlorophylls-a and -b, and phaeophytins-a and -b) displayed strong seasonal variations, but limited interannual variability between the two years of measurement. Fluxes of labile organic matter were characterised by strong pulses which occurred in spring and early summer, suggesting that the deep PAP area experiences relatively predictable patterns of vertical fluxes. No major quantitative differences in organic matter fluxes were observed between traps at different depths, but highest carbohydrate fluxes (time-weighted mean 2.4 mg m -2 d -1) were observed at 4700 m, whereas highest protein fluxes were observed at 1000 m (time-weighted mean 2.1 mg m -2 d -1). Carbohydrate, protein and phytopigment fluxes were correlated significantly, suggesting that settling material was associated with primary organic matter (i.e., phytodetritus) inputs from the photic layer. The contributions of chlorophyll-a and -b, and of phaeophytin-a and -b did not change significantly with increasing depth. Nor did the ratio of total phaeopigments to total chlorophylls did change greatly with depth (0.3-0.4 at both 3000 m and 4700 m depth) suggesting that degradation rates in the sinking particles were low. Protein and carbohydrate concentrations in the sediments at 4850 m depth (collected during 6 cruises between 1996 and 1998) and vertical fluxes at 3000 m depth followed inverse temporal patterns; peak concentrations

  17. Shiga Toxin (Stx) Classification, Structure, and Function.

    PubMed

    Melton-Celsa, Angela R

    2014-08-01

    Shiga toxin (Stx) is one of the most potent bacterial toxins known. Stx is found in Shigella dysenteriae 1 and in some serogroups of Escherichia coli (called Stx1 in E. coli). In addition to or instead of Stx1, some E. coli strains produce a second type of Stx, Stx2, that has the same mode of action as Stx/Stx1 but is antigenically distinct. Because subtypes of each toxin have been identified, the prototype toxin for each group is now designated Stx1a or Stx2a. The Stxs consist of two major subunits, an A subunit that joins noncovalently to a pentamer of five identical B subunits. The A subunit of the toxin injures the eukaryotic ribosome and halts protein synthesis in target cells. The function of the B pentamer is to bind to the cellular receptor, globotriaosylceramide, Gb3, found primarily on endothelial cells. The Stxs traffic in a retrograde manner within the cell, such that the A subunit of the toxin reaches the cytosol only after the toxin moves from the endosome to the Golgi and then to the endoplasmic reticulum. In humans infected with Stx-producing E. coli, the most serious manifestation of the disease, hemolytic-uremic syndrome, is more often associated with strains that produce Stx2a rather than Stx1a, and that relative toxicity is replicated in mice and baboons. Stx1a and Stx2a also exhibit differences in cytotoxicity to various cell types, bind dissimilarly to receptor analogs or mimics, induce differential chemokine responses, and have several distinctive structural characteristics.

  18. Structural insights into the mechanism of activation of the TRPV1 channel by a membrane-bound tarantula toxin.

    PubMed

    Bae, Chanhyung; Anselmi, Claudio; Kalia, Jeet; Jara-Oseguera, Andres; Schwieters, Charles D; Krepkiy, Dmitriy; Won Lee, Chul; Kim, Eun-Hee; Kim, Jae Il; Faraldo-Gómez, José D; Swartz, Kenton J

    2016-01-01

    Venom toxins are invaluable tools for exploring the structure and mechanisms of ion channels. Here, we solve the structure of double-knot toxin (DkTx), a tarantula toxin that activates the heat-activated TRPV1 channel. We also provide improved structures of TRPV1 with and without the toxin bound, and investigate the interactions of DkTx with the channel and membranes. We find that DkTx binds to the outer edge of the external pore of TRPV1 in a counterclockwise configuration, using a limited protein-protein interface and inserting hydrophobic residues into the bilayer. We also show that DkTx partitions naturally into membranes, with the two lobes exhibiting opposing energetics for membrane partitioning and channel activation. Finally, we find that the toxin disrupts a cluster of hydrophobic residues behind the selectivity filter that are critical for channel activation. Collectively, our findings reveal a novel mode of toxin-channel recognition that has important implications for the mechanism of thermosensation. PMID:26880553

  19. Structural insights into the mechanism of activation of the TRPV1 channel by a membrane-bound tarantula toxin

    PubMed Central

    Bae, Chanhyung; Anselmi, Claudio; Kalia, Jeet; Jara-Oseguera, Andres; Schwieters, Charles D; Krepkiy, Dmitriy; Won Lee, Chul; Kim, Eun-Hee; Kim, Jae Il; Faraldo-Gómez, José D; Swartz, Kenton J

    2016-01-01

    Venom toxins are invaluable tools for exploring the structure and mechanisms of ion channels. Here, we solve the structure of double-knot toxin (DkTx), a tarantula toxin that activates the heat-activated TRPV1 channel. We also provide improved structures of TRPV1 with and without the toxin bound, and investigate the interactions of DkTx with the channel and membranes. We find that DkTx binds to the outer edge of the external pore of TRPV1 in a counterclockwise configuration, using a limited protein-protein interface and inserting hydrophobic residues into the bilayer. We also show that DkTx partitions naturally into membranes, with the two lobes exhibiting opposing energetics for membrane partitioning and channel activation. Finally, we find that the toxin disrupts a cluster of hydrophobic residues behind the selectivity filter that are critical for channel activation. Collectively, our findings reveal a novel mode of toxin-channel recognition that has important implications for the mechanism of thermosensation. DOI: http://dx.doi.org/10.7554/eLife.11273.001 PMID:26880553

  20. Use of scanning calorimetry and microrespiration to determine effects of Bt toxin doses on Pandemis leafroller (Lepidoptera: Tortricidae) metabolism

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Differential scanning calorimetry and microrespiration were used to determine the effects of the biopesticide, Bt toxin, on the metabolism of infected Pandemis leafroller, Pandemis purusana (Kearfott). The metabolic heat rate, CO2 evolution, O2 consumption of 2nd and 3rd instars following a 2 h expo...

  1. Detection of the pufferfish toxin tetrodotoxin in European bivalves, England, 2013 to 2014.

    PubMed

    Turner, A D; Powell, A; Schofield, A; Lees, D N; Baker-Austin, C

    2015-01-15

    We report the first detection of tetrodotoxins (TTX) in European bivalve shellfish. We demonstrate that TTX is present within the temperate waters of the United Kingdom, along the English Channel, and can accumulate in filter-feeding molluscs. The toxin is heat-stable and thus it cannot be eliminated during cooking. While quantified concentrations were low in comparison to published minimum lethal doses for humans, the results demonstrate that the risk to shellfish consumers should not be discarded.

  2. Persistent Associative Plasticity at an Identified Synapse Underlying Classical Conditioning Becomes Labile with Short-Term Homosynaptic Activation

    PubMed Central

    Schacher, Samuel

    2015-01-01

    Synapses express different forms of plasticity that contribute to different forms of memory, and both memory and plasticity can become labile after reactivation. We previously reported that a persistent form of nonassociative long-term facilitation (PNA-LTF) of the sensorimotor synapses in Aplysia californica, a cellular analog of long-term sensitization, became labile with short-term heterosynaptic reactivation and reversed when the reactivation was followed by incubation with the protein synthesis inhibitor rapamycin. Here we examined the reciprocal impact of different forms of short-term plasticity (reactivations) on a persistent form of associative long-term facilitation (PA-LTF), a cellular analog of classical conditioning, which was expressed at Aplysia sensorimotor synapses when a tetanic stimulation of the sensory neurons was paired with a brief application of serotonin on 2 consecutive days. The expression of short-term homosynaptic plasticity [post-tetanic potentiation or homosynaptic depression (HSD)], or short-term heterosynaptic plasticity [serotonin-induced facilitation or neuropeptide Phe-Met-Arg-Phe-NH2 (FMRFa)-induced depression], at synapses expressing PA-LTF did not affect the maintenance of PA-LTF. The kinetics of HSD was attenuated at synapses expressing PA-LTF, which required activation of protein kinase C (PKC). Both PA-LTF and the attenuated kinetics of HSD were reversed by either a transient blockade of PKC activity or a homosynaptic, but not heterosynaptic, reactivation when paired with rapamycin. These results indicate that two different forms of persistent synaptic plasticity, PA-LTF and PNA-LTF, expressed at the same synapse become labile when reactivated by different stimuli. SIGNIFICANCE STATEMENT Activity-dependent changes in neural circuits mediate long-term memories. Some forms of long-term memories become labile and can be reversed with specific types of reactivations, but the mechanism is complex. At the cellular level

  3. Dissolved organic carbon lability and stable isotope shifts during microbial decomposition in a tropical river system

    NASA Astrophysics Data System (ADS)

    Geeraert, N.; Omengo, F. O.; Govers, G.; Bouillon, S.

    2016-01-01

    A significant amount of carbon is transported to the ocean as dissolved organic carbon (DOC) in rivers. During transport, it can be transformed through microbial consumption and photochemical oxidation. In dark incubation experiments with water from the Tana River, Kenya, we examined the consumption of DOC through microbial decomposition and the associated change in its carbon stable isotope composition (δ13C). In 15 of the 18 incubations, DOC concentrations decreased significantly by 10 to 60 %, with most of the decomposition taking place within the first 24-48 h. After 8 days, the remaining DOC was up to 3 ‰ more depleted in 13C compared with the initial pool, and the change in δ13C correlated strongly with the fraction of DOC remaining. We hypothesize that the shift in δ13C is consistent with greater microbial lability of DOC originating from herbaceous C4 vegetation than DOC derived from woody C3 vegetation in the semi-arid lower Tana. The results complement earlier findings that the stable isotope concentration of riverine DOC does not necessarily reflect the proportion of C3 and C4-derived DOC in the catchment: besides spatial distribution patterns of different vegetation types, processing within the river can further influence the δ13C of riverine OC.

  4. An improved high pressure freezing and freeze substitution method to preserve the labile vaccinia virus nucleocapsid.

    PubMed

    Jesus, Desyree Murta; Moussatche, Nissin; Condit, Richard C

    2016-07-01

    In recent years, high pressure freezing and freeze substitution have been widely used for electron microscopy to reveal viral and cellular structures that are difficult to preserve. Vaccinia virus, a member of the Poxviridae family, presents one of the most complex viral structures. The classical view of vaccinia virus structure consists of an envelope surrounding a biconcave core, with a lateral body in each concavity of the core. This classical view was challenged by Peters and Muller (1963), who demonstrated the presence of a folded tubular structure inside the virus core and stated the difficulty in visualizing this structure, possibly because it is labile and cannot be preserved by conventional sample preparation. Therefore, this tubular structure, now called the nucleocapsid, has been mostly neglected over the years. Earlier studies were able to preserve the nucleocapsid, but with low efficiency. In this study, we report the protocol (and troubleshooting) that resulted in preservation of the highest numbers of nucleocapsids in several independent preparations. Using this protocol, we were able to demonstrate an interdependence between the formation of the virus core wall and the nucleocapsid, leading to the hypothesis that an interaction exists between the major protein constituents of these compartments, A3 (core wall) and L4 (nucleocapsid). Our results show that high pressure freezing and freeze substitution can be used in more in-depth studies concerning the nucleocapsid structure and function.

  5. Labile male morphology and intraspecific male polymorphism in the Philotrypesis fig wasps.

    PubMed

    Jousselin, Emmanuelle; van Noort, Simon; Greeff, Jaco M

    2004-12-01

    We investigate the evolution of male morphology in the fig wasps belonging to the genus Philotrypesis (Chalcidoidea, Sycorectinae). We first reconstruct the phylogenetic relationships of Philotrypesis associated with African figs using nuclear and mitochondrial DNA. We then determine male morphotypes in the species included in our phylogeny and show that intraspecific polymorphism is common. Most species present two types of males and some species have up to three types. These morphotypes are believed to represent alternative mating tactics: some males show morphological adaptations to fighting, others are winged dispersers and others are small sneakers. Mapping out these variations onto our phylogeny reveals that the combination of morphs changes randomly along the branches of the tree. Both parsimony and likelihood approaches indicate that there has been at least one transition from dimorphism to trimorphism, several gains and losses of the small morph and two independent acquisitions of the winged morph. Using maximum likelihood analyses of character evolution, we estimate transition rates for each morph and show that the evolution of each type of morph are not correlated and that forward and backward transition rates are not significantly different. Our results altogether suggest that male morphology is evolutionary labile, it responds quickly to selection imposed by the mating environment. This study, also suggests that seemingly complex phenotypes, such as winged males, can evolve several times and can even be recreated after having been lost.

  6. Stabilized liquid membrane device (SLMD) for the passive, integrative sampling of labile metals in water

    USGS Publications Warehouse

    Brumbaugh, W.G.; Petty, J.D.; Huckins, J.N.; Manahan, S.E.

    2002-01-01

    A stabilized liquid membrane device (SLMD) is described for potential use as an in situ, passive, integrative sampler for cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) in natural waters. The SLMD (patent pending) consists of a 2.5-cm-wide by 15-cm-long strip of low-density polyethylene (LDPE) layflat tubing containing 1 mL of an equal mixture (v/v) of oleic acid (cis-9-octadecenoic acid) and EMO-8Q (7-[4-ethyl-1-methyloctyl]-8-quinolinol). The reagent mixture continuously diffuses to the exterior surface of the LDPE membrane, and provides for sequestration of several divalent metals for up to several weeks. Depending on sampler configuration, concentration factors of several thousand can be realized for these metal ions after just a few days. In addition to in situ deployment, the SLMD may be useful for laboratory determination of labile metal species in grab samples. Methods for minimizing the effects of water flow on the sampling rate are currently under investigation.

  7. Facile synthesis of acid-labile polymers with pendent ortho esters.

    PubMed

    Cheng, Jing; Ji, Ran; Gao, Shi-Juan; Du, Fu-Sheng; Li, Zi-Chen

    2012-01-01

    This work presents a facile approach for preparation of acid-labile and biocompatible polymers with pendent cyclic ortho esters, which is based on the efficient and mild reactions between cyclic ketene acetal (CKA) and hydroxyl groups. Three CKAs, 2-ethylidene-1,3-dioxane (EDO), 2-ethylidene-1,3-dioxolane (EDL), and 2-ethylidene-4- methyl-1,3-dioxolane (EMD) were prepared from the corresponding cyclic vinyl acetals by catalytic isomerization of the double bond. The reaction of CKAs with different alcohols and diols was examined using trace of p-toluenesulfonic acid as a catalyst. For the monohydroxyl alcohols, cyclic ortho esters were formed by simple addition of the hydroxyl group toward CKAs with ethanol showing a much greater reactivity than iso-propanol. When 1,2- or 1,3-diols were used to react with the CKAs, we observed the isomerized cyclic ortho esters besides the simple addition products. Biocompatible polyols, that is, poly(2-hydroxyethyl acrylate) (PHEA) and poly(vinyl alcohol) (PVA) were then modified with CKAs, and the degree of substitution of the pendent ortho esters can be easily tuned by changing feed ratio. Both the small molecule ortho esters and the CKA-modified polymers demonstrate the pH-dependent hydrolysis profiles, which depend also on the chemical structure of the ortho esters as well as the polymer hydrophobicity. PMID:22176024

  8. Uncaria tomentosa (Willd. ex. Roem. & Schult.) DC. and Eucalyptus globulus Labill. interactions when administered with diazepam.

    PubMed

    Quílez, A M; Saenz, M T; García, M D

    2012-03-01

    The safety of natural drugs is defined by their side effects and toxicity as well as any interactions that may occur if taken together with other drugs. In particular, it is essential to identify synergies, antagonisms and other types of interference with other drugs so that the correct choice can be made from the range of phytomedicines available. The aim of this work was to investigate changes in the pharmacological effect of diazepam (2 mg/kg) on the CNS when administered together with a medicinal plant: Eucalyptus globulus Labill. (eucalyptus 6 mg/kg and 3.25 mg/kg) or Uncaria tomentosa (Willd. ex Roem. & Schult). DC. (cat's claw, 7.14 mg/kg and 3.54 mg/kg). Various different psychopharmacological effects were evaluated through assessing exploratory behavior, muscle relaxation and spontaneous motor activity. Both phytodrugs interacted with the benzodiazepine. Eucalyptus had an inhibitory effect at both doses and could be useful at the highest dose in cases where the desired effect of the depressant is moderate anxiolytic activity without marked muscle relaxation. Cat's claw, at both doses, enhanced the action of diazepam on spontaneous motor activity and, at the lowest dose, exploratory ability. These herbal drugs could be useful for their antiinflammatory activity in musculoskeletal pathologies treated with benzodiazepines.

  9. Labile phases and the ocean's strontium cycle: A method of sediment trap sampling for acantharians

    NASA Astrophysics Data System (ADS)

    Bernstein, Renate E.; Betzer, Peter R.

    Acantharians are abundant marine planktonic protists and are the only marine organisms that use strontium as a major structural component. These organisms incorporate Sr in the form of celestite (SrSO4) into their skeletons and cysts [Odum, 1951]. Because the ocean is undersaturated with respect to SrSO4 [North, 1974], settling skeletons of dead acantharians and acantharian cysts are readily dissolved. After an initial burst of activity following their discovery in the mid-nineteenth century [Haeckel, 1887; Popofsky, 1909; Schewiakoff, 1926], the study of acantharians lagged during the mid-twentieth century. In part, this hiatus was related to the fact that acantharians are not preserved in the sedimentary record. Another contributing factor was the evolution in sampling and preservation techniques that mitigated against the preservation of these labile phases [Beers and Stewart, 1970; Michaels, 1988]. On the other hand, their susceptibility to dissolution implicates them as important mediators of the ocean's Sr budget [Bernstein et al., 1987]. Our short-term and relatively shallow sediment trap deployments, lack of preservatives, and rapid sample processing permitted the collection of the often elusive acantharian specimens.

  10. Assessing the labile arsenic pool in contaminated paddy soils by isotopic dilution techniques and simple extractions.

    PubMed

    Stroud, Jacqueline L; Khan, M Asaduzzman; Norton, Gareth J; Islam, M Rafiqul; Dasgupta, Tapash; Zhu, Yong-Guan; Price, Adam H; Meharg, Andrew A; McGrath, Steve P; Zhao, Fang-Jie

    2011-05-15

    Arsenic (As) contamination of paddy soils threatens rice cultivation and the health of populations relying on rice as a staple crop. In the present study, isotopic dilution techniques were used to determine the chemically labile (E value) and phytoavailable (L value) pools of As in a range of paddy soils from Bangladesh, India, and China and two arable soils from the UK varying in the degree and sources of As contamination. The E value accounted for 6.2-21.4% of the total As, suggesting that a large proportion of soil As is chemically nonlabile. L values measured with rice grown under anaerobic conditions were generally larger than those under aerobic conditions, indicating increased potentially phytoavailable pool of As in flooded soils. In an incubation study, As was mobilized into soil pore water mainly as arsenite under flooded conditions, with Bangladeshi soils contaminated by irrigation of groundwater showing a greater potential of As mobilization than other soils. Arsenic mobilization was best predicted by phosphate-extractable As in the soils. PMID:21504212

  11. Energy evaluation of forest residues originated from Eucalyptus globulus Labill in Galicia.

    PubMed

    Núñez-Regueira, L; Proupín-Castiñeiras, J; Rodríguez-Añón, J A

    2002-03-01

    The possibility of retrieving the energy contained in forest residues originating from wood exploitation in Galicia (Spain) is evaluated. This study was made on Eucalyptus globulus Labill occupying a forest surface of 240000 ha. This species plays an important role in the economical development of Galicia, as it is the main forest species for production of pulp. Sampling was made over 1999 in seven different zones, three main stations plus four selected for comparison, situated in Galicia. The residues originating from cutting were sorted into three different groups and their calorific values were measured by static bomb calorimetry. These calorific values, close to 7200 kJ kg(-1), make possible the use of this residual biomass as an energy source. Calorific values were measured by static bomb calorimeter in an oxygen atmosphere. Flammability was determined using a standard epiradiator. Simultaneously, some other parameters, elementary chemical composition, heavy metal contents, moisture, density, ash percentage after combustion in the bomb, and main bioclimatic characteristics, were also determined. PMID:11848377

  12. Development and bioorthogonal activation of palladium-labile prodrugs of gemcitabine.

    PubMed

    Weiss, Jason T; Dawson, John C; Fraser, Craig; Rybski, Witold; Torres-Sánchez, Carmen; Bradley, Mark; Patton, E Elizabeth; Carragher, Neil O; Unciti-Broceta, Asier

    2014-06-26

    Bioorthogonal chemistry has become one of the main driving forces in current chemical biology, inspiring the search for novel biocompatible chemospecific reactions for the past decade. Alongside the well-established labeling strategies that originated the bioorthogonal paradigm, we have recently proposed the use of heterogeneous palladium chemistry and bioorthogonal Pd(0)-labile prodrugs to develop spatially targeted therapies. Herein, we report the generation of biologically inert precursors of cytotoxic gemcitabine by introducing Pd(0)-cleavable groups in positions that are mechanistically relevant for gemcitabine's pharmacological activity. Cell viability studies in pancreatic cancer cells showed that carbamate functionalization of the 4-amino group of gemcitabine significantly reduced (>23-fold) the prodrugs' cytotoxicity. The N-propargyloxycarbonyl (N-Poc) promoiety displayed the highest sensitivity to heterogeneous palladium catalysis under biocompatible conditions, with a reaction half-life of less than 6 h. Zebrafish studies with allyl, propargyl, and benzyl carbamate-protected rhodamines confirmed N-Poc as the most suitable masking group for implementing in vivo bioorthogonal organometallic chemistry. PMID:24867590

  13. Interaction between environmental factors affects the accumulation of root proteins in hydroponically grown Eucalyptus globulus (Labill.).

    PubMed

    Bedon, Frank; Majada, Juan; Feito, Isabel; Chaumeil, Philippe; Dupuy, Jean-William; Lomenech, Anne-Marie; Barre, Aurélien; Gion, Jean-Marc; Plomion, Christophe

    2011-01-01

    Eucalyptus globulus (Labill.) is used for pulp and paper production worldwide. In this report we studied changes in protein expression in one osmotically stressed elite clone widely used in industrial plantations in Spain. High molecular weight polyethylene glycol (PEG) was used as an osmoticum in the growing medium. Roots of rooted cuttings were sampled after 3 and 36 h of treatment. Water potential and abscissic acid content were measured in shoot and root apices to characterize the physiological states of the plants. Total soluble proteins from roots were extracted and separated using two-dimensional gel electrophoresis (2-DE). Gels were stained with Coomassie brillant blue for quantitative analysis of protein accumulation. From a total of 406 reproducible spots, 34 were found to be differentially expressed depending on treatment (osmotic versus control condition) and/or stress duration (3 h versus 36 h), and were further characterized by tandem mass spectrometry. Several proteins were reliably identified including adenosine kinase, actin, stress-related proteins as well as proteins associated to cellular processes, among which some residents of the endoplasmic reticulum. This study constitutes the first investigation of the root proteome in this important forest tree genus. PMID:20974537

  14. Nitric oxide is necessary for labilization of a consolidated context memory during reconsolidation in terrestrial snails.

    PubMed

    Balaban, Pavel M; Roshchin, Matvey; Timoshenko, Alia K; Gainutdinov, Khalil L; Bogodvid, Tatiana K; Muranova, Lyudmila N; Zuzina, Alena B; Korshunova, Tatiana A

    2014-09-01

    Nitric oxide (NO) is known to be involved in associative memory formation. We investigated the influence of blocking NO function on the reconsolidation of context memory in terrestrial snails (Helix lucorum L.). After a 10 day session of electric shocks in one context only, context memory in snails was observed in test sessions as the significant difference of amplitudes of withdrawal responses to tactile stimuli in two different contexts. After a 1 day rest, a session of 'reminding' was performed, preceded by injection in different groups of the snails with either vehicle or combination of the protein synthesis blocker anisomycin (ANI) with one of the following drugs: the NO scavenger carboxy-PTIO, the NO-synthase inhibitors N-omega-nitro-L-arginin, nitroindazole and NG-nitro-L-arginine methyl ester hydrochloride, or the NO donor S-nitroso-N-acetyl-DL-penicillamine. Testing the context memory at different time intervals after the reminder under ANI injection showed that the context memory was impaired at 24 h and later, whereas the reminder under combined injection of ANI and each of the NO-synthase inhibitors used or the NO scavenger showed no impairment of long-term context memory. Injection of the NO donor S-nitroso-N-acetyl-DL-penicillamine with or without reminder had no effect on context memory. The results obtained demonstrated that NO is necessary for labilization of a consolidated context memory.

  15. An intermetallic Au24Ag20 superatom nanocluster stabilized by labile ligands.

    PubMed

    Wang, Yu; Su, Haifeng; Xu, Chaofa; Li, Gang; Gell, Lars; Lin, Shuichao; Tang, Zichao; Häkkinen, Hannu; Zheng, Nanfeng

    2015-04-01

    An intermetallic nanocluster containing 44 metal atoms, Au24Ag20(2-SPy)4(PhC≡C)20Cl2, was successfully synthesized and structurally characterized by single-crystal analysis and density funtional theory computations. The 44 metal atoms in the cluster are arranged as a concentric three-shell Au12@Ag20@Au12 Keplerate structure having a high symmetry. For the first time, the co-presence of three different types of anionic ligands (i.e., phenylalkynyl, 2-pyridylthiolate, and chloride) was revealed on the surface of metal nanoclusters. Similar to thiolates, alkynyls bind linearly to surface Au atoms using their σ-bonds, leading to the formation of two types of surface staple units (PhC≡C-Au-L, L = PhC≡C(-) or 2-pyridylthiolate) on the cluster. The co-presence of three different surface ligands allows the site-specific surface and functional modification of the cluster. The lability of PhC≡C(-) ligands on the cluster was demonstrated, making it possible to keep the metal core intact while removing partial surface capping. Moreover, it was found that ligand exchange on the cluster occurs easily to offer various derivatives with the same metal core but different surface functionality and thus different solubility. PMID:25803406

  16. A novel nanoparticulate system for sustained delivery of acid-labile lansoprazole.

    PubMed

    Alai, Milind Sadashiv; Lin, Wen Jen

    2013-11-01

    In the present study, an effort was made to develop the Eudragit RS100 based nanoparticulate system for sustained delivery of an acid-labile drug, lansoprazole (LPZ). LPZ-loaded Eudragit RS100 nanoparticles (ERSNPs) were prepared by oil-in-water emulsion-solvent evaporation method. The effects of various formulation variables such as polymer concentration, drug amount and solvent composition on physicochemical performance of nanoparticles and in vitro drug release were investigated. All nanoparticles were spherical with particle size 198.9 ± 8.6-376.9 ± 5.6 nm and zeta potential +35.1 ± 1.7 to +40.2 ± 0.8 mV. The yield of nanoparticles was unaffected by change of these three variables. However, the drug loading and encapsulation efficiency were affected by polymer concentration and drug amount. On the other hand, the particle size of nanoparticles was significantly affected by polymer concentration and internal phase composition due to influence of droplet size during emulsification process. All nanoparticles prolonged drug release for 24h which was dominated by a combination of drug diffusion and polymer chain relaxation. The fastest and the slowest release rates were observed in C2-1002-10/0 and C8-4001-10/0, respectively, based on the release rate constant (k). Thus, the developed nanoparticles possessed a potential as a nano-carrier to sustain drug delivery for treatment of acid related disorders.

  17. Lability of GABAA receptor function in human partial epilepsy: possible relationship to hypometabolism.

    PubMed

    Pumain, René; Ahmed, Mounia Sid; Kurcewicz, Irène; Trottier, Suzanne; Louvel, Jacques; Turak, Baris; Devaux, Bertrand; Laschet, Jacques

    2008-11-01

    The function of the gamma-aminobutyric acid type A receptor (GABA(A)R) is maintained by endogenous phosphorylation. We have shown that the corresponding kinase is the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH), using the locally produced glycolytic ATP. In addition, using cerebral tissue obtained during curative surgery for epilepsy, we showed that both the endogenous phosphorylation and the GABA(A)R function are significantly reduced in the "epileptogenic" cerebral cortex when compared to "control" tissue. This dysfunction likely contributes to seizure generation and/or transition from the interictal to the ictal state. Glucose utilization is decreased in the epileptogenic cortex of patients with partial epilepsy in the interictal state, but the relationship to the disorder remains unclear. We propose that this hypometabolism is related to the deficiency in the endogenous phosphorylation of GABA(A)R and the resulting greater lability of GABAergic inhibition. Several lines of evidences indeed suggest that GABAergic inhibition is costly in terms of metabolic consumption. The deficiency of this glycolysis-dependent mechanism may thus link epileptogenicity to glucose hypometabolism. The antiepileptic effect of ketogenic diets may be mediated by the subsequent rise in the NADH/NAD(+) index, which favors GABA(A)R endogenous phosphorylation and should contribute to restoration of GABAergic inhibition in the epileptogenic zone.

  18. Acid-Labile Subunit Deficiency and Growth Failure: Description of Two Novel Cases

    PubMed Central

    David, A; Rose, S.J.; Miraki-Moud, F.; Metherell, L.A.; Savage, M.O.; Clark, A.J.L.; Camacho-Hübner, C.

    2010-01-01

    Background/Aims Mutations in the acid-labile subunit (ALS) gene (IGFALS) have been associated with circulating insulin-like growth factor I (IGF-I) deficiency and short stature. Whether severe pubertal delay is also part of the phenotype remains controversial due to the small number of cases reported. We report 2 children with a history of growth failure due to novel IGFALS mutations. Methods The growth hormone receptor gene (GHR) and IGFALS were analyzed by direct sequencing. Ternary complex formation was studied by size exclusion chromatography. Results Two boys of 13.3 and 10.6 years, with pubertal stages 2 and 1, had mild short stature (−3.2 and −2.8 SDS, respectively) and a biochemical profile suggestive of growth hormone resistance. No defects were identified in the GHR. Patient 1 was homozygous for the IGFALS missense mutation P73L. Patient 2 was a compound heterozygote for the missense mutation L134Q and a novel GGC to AG substitution at position 546–548 (546–548delGGCinsAG). The latter causes a frameshift and the appearance of a premature stop codon. Size exclusion chromatography showed no peaks corresponding to ternary and binary complexes in either patient. Conclusion Screening of the IGFALS is important in children with short stature associated with low serum IGF-I, IGFBP-3 and ALS. PMID:20389102

  19. Membrane Transport Behavior and the Lability of Chloride on Polyphosphazenes Bearing Bulky Substituents

    SciTech Connect

    Frederick F. Stewart; John R. Klaehn; Christopher J. Orme

    2007-08-01

    Polyphosphazenes are an intriguing class of inorganic polymers where much of their functionality is derived from pendant groups attached to phosphorus. The backbone of the polymer consists of alternating phosphorus and nitrogen atoms where the bonding is conventionally drawn as alternating double and single bonds. Orbital nodes are located at each phosphorus atom resulting in electron delocalization between phosphorus atoms, but not through them. Thus, the polymer backbone has a high degree of flexibility where halogens or other leaving groups can be effectively displaced with nucleophiles. In this paper, the first known example of a polyphosphazene with large quantities of non-labile chloride substituents induced by neighboring group steric effects will be discussed. This example is the result of the substitution of poly[bis-chlorophosphazene] with the sodium salt of 3,5-di-tert-butylphenol where only 60% of the chlorines were displaced. This contrasts with the 100% substitution observed with other phenols (phenol, 4-tert-butylphenol, 3-methylphenol, etc.).

  20. Assessing the labile arsenic pool in contaminated paddy soils by isotopic dilution techniques and simple extractions.

    PubMed

    Stroud, Jacqueline L; Khan, M Asaduzzman; Norton, Gareth J; Islam, M Rafiqul; Dasgupta, Tapash; Zhu, Yong-Guan; Price, Adam H; Meharg, Andrew A; McGrath, Steve P; Zhao, Fang-Jie

    2011-05-15

    Arsenic (As) contamination of paddy soils threatens rice cultivation and the health of populations relying on rice as a staple crop. In the present study, isotopic dilution techniques were used to determine the chemically labile (E value) and phytoavailable (L value) pools of As in a range of paddy soils from Bangladesh, India, and China and two arable soils from the UK varying in the degree and sources of As contamination. The E value accounted for 6.2-21.4% of the total As, suggesting that a large proportion of soil As is chemically nonlabile. L values measured with rice grown under anaerobic conditions were generally larger than those under aerobic conditions, indicating increased potentially phytoavailable pool of As in flooded soils. In an incubation study, As was mobilized into soil pore water mainly as arsenite under flooded conditions, with Bangladeshi soils contaminated by irrigation of groundwater showing a greater potential of As mobilization than other soils. Arsenic mobilization was best predicted by phosphate-extractable As in the soils.

  1. Chemical reactivity of labile sulfur of iron-sulfur proteins. The reaction of triphenyl phosphine.

    PubMed

    Manabe, T; Goda, K; Kimura, T

    1976-04-23

    The reaction of triphenyl phosphine to iron-sulfur proteins from adrenal cortex mitochondria, spinach chloroplasts, and Clostridium pasteurianum was investigated. As ethanol concentrations in the reaction mixture increased, the rate of the reaction decreased. In the simultaneous presence of 1 M KC1 and 5 M urea, the reaction rate reached at maximum. Under these conditions the initial rates of the decolorization reaction by the phosphine were found to be 8.7, 0.88, and 1.8 nmol of ferredoxin per min at 25 degrees C for adrenal, spinach, and clostridial ferredoxins, respectively. The kinetic curves for the reaction of the phosphine sulfide formation, the loss of labile sulfur, and the deterioriation of visible absorption showed a similar pattern with a comparable rate. During this reaction, the complete reduction of ferric ions present in ferredoxin was observed with a fast rate under either aerobic or anaerobic conditions. These results suggest that the iron atoms in ferredoxin are first reduced by the intramolecular reductants in the presence of triphenyl phosphine with the concomitant formation of S2-2, which then reacts with triphenyl phosphine resulting in the formation of triphenyl phosphine sulfide.

  2. Isolation and evolution of labile sulfur allotropes via kinetic encapsulation in interactive porous networks

    PubMed Central

    Kitagawa, Hakuba; Ohtsu, Hiroyoshi; Cruz-Cabeza, Aurora J.; Kawano, Masaki

    2016-01-01

    The isolation and characterization of small sulfur allotropes have long remained unachievable because of their extreme lability. This study reports the first direct observation of disulfur (S2) with X-ray crystallography. Sulfur gas was kinetically trapped and frozen into the pores of two Cu-based porous coordination networks containing interactive iodide sites. Stabilization of S2 was achieved either through physisorption or chemisorption on iodide anions. One of the networks displayed shape selectivity for linear molecules only, therefore S2 was trapped and remained stable within the material at room temperature and higher. In the second network, however, the S2 molecules reacted further to produce bent-S3 species as the temperature was increased. Following the thermal evolution of the S2 species in this network using X-ray diffraction and Raman spectroscopy unveiled the generation of a new reaction intermediate never observed before, the cyclo-tri­sulfur dication (cyclo-S3 2+). It is envisaged that kinetic guest trapping in interactive crystalline porous networks will be a promising method to investigate transient chemical species. PMID:27437110

  3. Interaction between environmental factors affects the accumulation of root proteins in hydroponically grown Eucalyptus globulus (Labill.).

    PubMed

    Bedon, Frank; Majada, Juan; Feito, Isabel; Chaumeil, Philippe; Dupuy, Jean-William; Lomenech, Anne-Marie; Barre, Aurélien; Gion, Jean-Marc; Plomion, Christophe

    2011-01-01

    Eucalyptus globulus (Labill.) is used for pulp and paper production worldwide. In this report we studied changes in protein expression in one osmotically stressed elite clone widely used in industrial plantations in Spain. High molecular weight polyethylene glycol (PEG) was used as an osmoticum in the growing medium. Roots of rooted cuttings were sampled after 3 and 36 h of treatment. Water potential and abscissic acid content were measured in shoot and root apices to characterize the physiological states of the plants. Total soluble proteins from roots were extracted and separated using two-dimensional gel electrophoresis (2-DE). Gels were stained with Coomassie brillant blue for quantitative analysis of protein accumulation. From a total of 406 reproducible spots, 34 were found to be differentially expressed depending on treatment (osmotic versus control condition) and/or stress duration (3 h versus 36 h), and were further characterized by tandem mass spectrometry. Several proteins were reliably identified including adenosine kinase, actin, stress-related proteins as well as proteins associated to cellular processes, among which some residents of the endoplasmic reticulum. This study constitutes the first investigation of the root proteome in this important forest tree genus.

  4. Effect of pH on Metal Lability in Drinking Water Treatment Residuals.

    PubMed

    Wang, Changhui; Yuan, Nannan; Pei, Yuansheng

    2014-01-01

    Drinking water treatment residuals (WTRs), by-products generated during treatment of drinking water, can be reused as environmental amendments to remediate contamination. However, this beneficial reuse may be hampered by the potential release of toxic contaminants (e.g., metals) in the WTRs. In present study, batch tests and then fractionation, in vitro digestion, and the toxicity characteristic leaching procedure were used to investigate the release and extractability of metals in the Fe/Al hydroxides comprised WTRs under differing pH. The results demonstrated that significant release from WTRs for Ba, Be, Ca, Cd, Co, Cr, Fe, Mg, Mn, Pb, Sr, and Zn occurred under low pH (acid condition); for As, Mo, and V under high pH (alkaline condition); and for Al, Cu, and Ni under both conditions. In comparison, most metals in the WTRs were more easily released under low pH, but the release was stable at a relatively low level between pH 6 and 9, especially under alkaline conditions. Further analysis indicated that the chemical extractability and bioaccessibility of many metals was found to increase in the WTRs after being leached, even though the leached WTRs could still be considered nonhazardous. These results demonstrated that pH had a substantial effect on the lability of metals in WTRs. Overall, caution should be used when considering pH conditions during WTRs reuse to avoid potential metal pollution.

  5. An intermetallic Au24Ag20 superatom nanocluster stabilized by labile ligands.

    PubMed

    Wang, Yu; Su, Haifeng; Xu, Chaofa; Li, Gang; Gell, Lars; Lin, Shuichao; Tang, Zichao; Häkkinen, Hannu; Zheng, Nanfeng

    2015-04-01

    An intermetallic nanocluster containing 44 metal atoms, Au24Ag20(2-SPy)4(PhC≡C)20Cl2, was successfully synthesized and structurally characterized by single-crystal analysis and density funtional theory computations. The 44 metal atoms in the cluster are arranged as a concentric three-shell Au12@Ag20@Au12 Keplerate structure having a high symmetry. For the first time, the co-presence of three different types of anionic ligands (i.e., phenylalkynyl, 2-pyridylthiolate, and chloride) was revealed on the surface of metal nanoclusters. Similar to thiolates, alkynyls bind linearly to surface Au atoms using their σ-bonds, leading to the formation of two types of surface staple units (PhC≡C-Au-L, L = PhC≡C(-) or 2-pyridylthiolate) on the cluster. The co-presence of three different surface ligands allows the site-specific surface and functional modification of the cluster. The lability of PhC≡C(-) ligands on the cluster was demonstrated, making it possible to keep the metal core intact while removing partial surface capping. Moreover, it was found that ligand exchange on the cluster occurs easily to offer various derivatives with the same metal core but different surface functionality and thus different solubility.

  6. Determination of labile copper, cobalt, and chromium in textile mill wastewater

    SciTech Connect

    Crain, J.S.; Essling, A.M.; Kiely, J.T.

    1997-01-01

    Copper, chromium, and cobalt species present in filtered wastewater effluent were separated by cation exchange and reverse phase chromatography. Three sample fractions were obtained: one containing metal cations (i.e., trivalent Cr, divalent Cu, and divalent Co), one containing organic species (including metallized dyes), and one containing other unretained species. The metal content of each fraction was determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The sum of the corrected data was compared to the metal content of a filtered effluent aliquot digested totally with fuming sulfuric acid. Other aliquots of the filtered effluent were spiked with the metals of interest and digested to confirm chemical yield and accuracy. Method detection limits were consistently below 20 {mu}g L{sup -1} for Cu, 30 {mu}g L{sup -1} for Co, and 10 {mu}g L{sup -1} for Cr. Spike recoveries for undifferentiated Cu and Cr were statistically indistinguishable from unity; although Co spike recoveries were slightly low ({approximately}95%), its chemical yield was 98%. Copper retention on the sodium sulfonate cation exchange resin was closely correlated with the [EDTA]/[Cu] ratio, suggesting that metals retained upon the cation exchange column were assignable to labile metal species; however, mass balances for all three elements, though reasonable ({approximately}90%), were significantly different from unity. Mechanical factors may have contributed to the material loss, but other data suggest that some metal species reacted irreversibly with the reverse phase column. 3 refs., 2 figs., 4 tabs.

  7. Sample storage-induced changes in the quantity and quality of soil labile organic carbon

    PubMed Central

    Sun, Shou-Qin; Cai, Hui-Ying; Chang, Scott X.; Bhatti, Jagtar S.

    2015-01-01

    Effects of sample storage methods on the quantity and quality of labile soil organic carbon are not fully understood even though their effects on basic soil properties have been extensively studied. We studied the effects of air-drying and frozen storage on cold and hot water soluble organic carbon (WSOC). Cold- and hot-WSOC in air-dried and frozen-stored soils were linearly correlated with those in fresh soils, indicating that storage proportionally altered the extractability of soil organic carbon. Air-drying but not frozen storage increased the concentrations of cold-WSOC and carbohydrate in cold-WSOC, while both increased polyphenol concentrations. In contrast, only polyphenol concentration in hot-WSOC was increased by air-drying and frozen storage, suggesting that hot-WSOC was less affected by sample storage. The biodegradability of cold- but not hot-WSOC was increased by air-drying, while both air-drying and frozen storage increased humification index and changed specific UV absorbance of both cold- and hot-WSOC, indicating shifts in the quality of soil WSOC. Our results suggest that storage methods affect the quantity and quality of WSOC but not comparisons between samples, frozen storage is better than air-drying if samples have to be stored, and storage should be avoided whenever possible when studying the quantity and quality of both cold- and hot-WSOC. PMID:26617054

  8. Thermodynamic N-donor trans influence in labile pseudo-octahedral zinc complexes: a delusion?

    PubMed

    Aboshyan-Sorgho, Lilit; Lathion, Timothée; Guénée, Laure; Besnard, Céline; Piguet, Claude

    2014-12-15

    While the forces responsible for the chelate effect are well-established in coordination chemistry, the origin and implementation of the related thermodynamic trans influence remains debatable. This work illustrates a simple approach for quantifying this effect in labile pseudo-octahedral [Zn(Lk)3](2+) complexes lacking stereochemical preferences (Lk = L1–L4 are unsymmetrical didentate α,α′-diimine ligands). In line with statistics, the triply degenerated meridional isomers mer-[Zn(Lk)3](2+) are stabilized by 0.8 ≤ ΔGexch(mer→fac) ≤ 4.2 kJ/mol over their nondegenerated facial analogues fac-[Zn(Lk)3](2+) and therefore display no apparent trans influence at room temperature. However, the dissection of the free energy terms into opposite enthalpic (favoring the facial isomers) and entropic (favoring the meridional isomers) contributions reveals a trans influence assigned to solvation processes occurring in polar solvents. Altogether, the thermodynamic trans influence operating in [Zn(α,α′-diimine)3](2+) complexes is 1–2 orders of magnitude smaller than the chelate effect. A weak templating effect provided by a noncovalent lanthanide tripod is thus large enough to produce the wanted facial isomer at room temperature. PMID:25407515

  9. Sample storage-induced changes in the quantity and quality of soil labile organic carbon

    NASA Astrophysics Data System (ADS)

    Sun, Shou-Qin; Cai, Hui-Ying; Chang, Scott X.; Bhatti, Jagtar S.

    2015-11-01

    Effects of sample storage methods on the quantity and quality of labile soil organic carbon are not fully understood even though their effects on basic soil properties have been extensively studied. We studied the effects of air-drying and frozen storage on cold and hot water soluble organic carbon (WSOC). Cold- and hot-WSOC in air-dried and frozen-stored soils were linearly correlated with those in fresh soils, indicating that storage proportionally altered the extractability of soil organic carbon. Air-drying but not frozen storage increased the concentrations of cold-WSOC and carbohydrate in cold-WSOC, while both increased polyphenol concentrations. In contrast, only polyphenol concentration in hot-WSOC was increased by air-drying and frozen storage, suggesting that hot-WSOC was less affected by sample storage. The biodegradability of cold- but not hot-WSOC was increased by air-drying, while both air-drying and frozen storage increased humification index and changed specific UV absorbance of both cold- and hot-WSOC, indicating shifts in the quality of soil WSOC. Our results suggest that storage methods affect the quantity and quality of WSOC but not comparisons between samples, frozen storage is better than air-drying if samples have to be stored, and storage should be avoided whenever possible when studying the quantity and quality of both cold- and hot-WSOC.

  10. DGT measurement in low flow conditions: diffusive boundary layer and lability considerations.

    PubMed

    Uher, Emmanuelle; Tusseau-Vuillemin, Marie-Hélène; Gourlay-France, Catherine

    2013-07-01

    Recent papers have alerted the scientific community that a diffusive boundary layer (DBL) forming in front of diffusive gradients in thin film (DGT) devices when they are immersed in water might have a significant impact on the results and have suggested a method to assess the DBL. This paper aims at evaluating to what extent the DBL impacts the results of metal measurement in water by DGT and providing new information on the dissociation kinetics of metal complexes in wastewater by using DBL calculation. A careful study of the influence of the water velocity on the measurement with DGTs equipped with restricted gels is presented. Deployments took place in the laboratory with a range of stirring speeds (0-400 rpm) and in a canal receiving treated wastewater with increasing controlled water velocity (0.07-3 cm s(-1)). Even under extreme low flow conditions, the error made in using the equation that does not take into account that the DBL was lower than the analytical error. Nevertheless, the DBL is the seat of dissociation of complexes and increases the lability window beyond the steric constraints of the hydrogel. The capacity of restricted gels to only sample inorganic species under these conditions is questioned. This study also is an opportunity to provide information on metal-ligand interactions in wastewater by creating the kinetic signature of the wastewater. Unlike previous studies which used different types of water, Pb was the more limited metal and interacted strongly with the ligands. PMID:23722876

  11. Array biosensor for detection of toxins

    NASA Technical Reports Server (NTRS)

    Ligler, Frances S.; Taitt, Chris Rowe; Shriver-Lake, Lisa C.; Sapsford, Kim E.; Shubin, Yura; Golden, Joel P.

    2003-01-01

    The array biosensor is capable of detecting multiple targets rapidly and simultaneously on the surface of a single waveguide. Sandwich and competitive fluoroimmunoassays have been developed to detect high and low molecular weight toxins, respectively, in complex samples. Recognition molecules (usually antibodies) were first immobilized in specific locations on the waveguide and the resultant patterned array was used to interrogate up to 12 different samples for the presence of multiple different analytes. Upon binding of a fluorescent analyte or fluorescent immunocomplex, the pattern of fluorescent spots was detected using a CCD camera. Automated image analysis was used to determine a mean fluorescence value for each assay spot and to subtract the local background signal. The location of the spot and its mean fluorescence value were used to determine the toxin identity and concentration. Toxins were measured in clinical fluids, environmental samples and foods, with minimal sample preparation. Results are shown for rapid analyses of staphylococcal enterotoxin B, ricin, cholera toxin, botulinum toxoids, trinitrotoluene, and the mycotoxin fumonisin. Toxins were detected at levels as low as 0.5 ng mL(-1).

  12. Crystal structure of Clostridium difficile toxin A.

    PubMed

    Chumbler, Nicole M; Rutherford, Stacey A; Zhang, Zhifen; Farrow, Melissa A; Lisher, John P; Farquhar, Erik; Giedroc, David P; Spiller, Benjamin W; Melnyk, Roman A; Lacy, D Borden

    2016-01-01

    Clostridium difficile infection is the leading cause of hospital-acquired diarrhoea and pseudomembranous colitis. Disease is mediated by the actions of two toxins, TcdA and TcdB, which cause the diarrhoea, as well as inflammation and necrosis within the colon(1,2). The toxins are large (308 and 270 kDa, respectively), homologous (47% amino acid identity) glucosyltransferases that target small GTPases within the host(3,4). The multidomain toxins enter cells by receptor-mediated endocytosis and, upon exposure to the low pH of the endosome, insert into and deliver two enzymatic domains across the membrane. Eukaryotic inositol-hexakisphosphate (InsP6) binds an autoprocessing domain to activate a proteolysis event that releases the N-terminal glucosyltransferase domain into the cytosol. Here, we report the crystal structure of a 1,832-amino-acid fragment of TcdA (TcdA1832), which reveals a requirement for zinc in the mechanism of toxin autoprocessing and an extended delivery domain that serves as a scaffold for the hydrophobic α-helices involved in pH-dependent pore formation. A surface loop of the delivery domain whose sequence is strictly conserved among all large clostridial toxins is shown to be functionally important, and is highlighted for future efforts in the development of vaccines and novel therapeutics. PMID:27571750

  13. Interaction of diphtheria toxin with phosphorylated molecules.

    PubMed Central

    Proia, R L; Hart, D A; Eidels, L

    1979-01-01

    The binding of diphtheria toxin to 125I-labeled cell surface glycoproteins from hamster thymocytes was shown to be inhibited by nucleotides. The relative effectiveness of the nucleotides (at 5 mM) was found to be thymidine triphosphate greater than adenosine triphosphate greater than guanosine triphosphate greater than uridine triphosphate greater than cytidine triphosphate. When adenine-containing compounds were used, the relative effectiveness was determined to be adenosine tetraphosphate greater than adenosine triphosphate greater than adenosine diphosphate greater than adenosine monophosphate. In addition, tetrapolyphosphate, tripolyphosphate, inositol hexaphosphate (phytic acid), and the highly phosphorylated proteins casein and phosvitin were also shown to be potent inhibitors of the binding of diphtheria toxin to 125I-labeled cell surface glycoproteins. Diphtheria toxin was shown to bind directly to 125I-casein; this binding was also inhibited by the highly phosphorylated compounds and was decreased by pretreatment of the 125I-casein with alkaline phosphatase. These results suggest that diphtheria toxin binds to regions of high phosphate density and raise the possibility that the site on the cell surface glycoproteins to which diphtheria toxin binds might be polyanionic in nature. PMID:528059

  14. Crystal structure of Clostridium difficile toxin A

    PubMed Central

    Chumbler, Nicole M.; Rutherford, Stacey A.; Zhang, Zhifen; Farrow, Melissa A.; Lisher, John P.; Farquhar, Erik; Giedroc, David P.; Spiller, Benjamin W.; Melnyk, Roman A.; Lacy, D. Borden

    2016-01-01

    Clostridium difficile infection is the leading cause of hospital-acquired diarrhoea and pseudomembranous colitis. Disease is mediated by the actions of two toxins, TcdA and TcdB, which cause the diarrhoea, as well as inflammation and necrosis within the colon1,2. The toxins are large (308 and 270 kDa, respectively), homologous (47% amino acid identity) glucosyltransferases that target small GTPases within the host3,4. The multidomain toxins enter cells by receptor-mediated endocytosis and, upon exposure to the low pH of the endosome, insert into and deliver two enzymatic domains across the membrane. Eukaryotic inositol-hexakisphosphate (InsP6) binds an autoprocessing domain to activate a proteolysis event that releases the N-terminal glucosyltransferase domain into the cytosol. Here, we report the crystal structure of a 1,832-amino-acid fragment of TcdA (TcdA1832), which reveals a requirement for zinc in the mechanism of toxin autoprocessing and an extended delivery domain that serves as a scaffold for the hydrophobic α-helices involved in pH-dependent pore formation. A surface loop of the delivery domain whose sequence is strictly conserved among all large clostridial toxins is shown to be functionally important, and is highlighted for future efforts in the development of vaccines and novel therapeutics. PMID:27571750

  15. Binding of NAD+ to pertussis toxin.

    PubMed

    Lobban, M D; Irons, L I; van Heyningen, S

    1991-06-24

    The equilibrium dissociation constant of NAD+ and pertussis toxin was determined by equilibrium dialysis and by the quenching of the protein's intrinsic fluorescence on titration with NAD+. A binding constant, Kd, of 24 +/- 2 microM at 30 degrees C was obtained from equilibrium dialysis, consistent with the previously determined value for the Michaelis constant, Km, of 30 +/- 5 microM for NAD+ (when the toxin is catalysing the ADP-ribosylation of water and of dithiothreitol). The intrinsic fluorescence of pertussis toxin was quenched by up to 60% on titration with NAD+, and after correction for dilution and inner filter effects, a Kd value of 27 microM at 30 degrees C was obtained, agreeing well with that found by equilibrium dialysis. The binding constants were measured at a number of temperatures using both techniques, and from this the enthalpy of binding of NAD+ to toxin was determined to be 30 kJ.mol-1, a typical value for a protein-ligand interaction. There is one binding site for NAD+ per toxin molecule. PMID:1648404

  16. Determination of labile inorganic and organic species of Al and Cu in river waters using the diffusive gradients in thin films technique.

    PubMed

    Tonello, Paulo Sergio; Goveia, Danielle; Rosa, André Henrique; Fraceto, Leonardo Fernandes; Menegário, Amauri Antonio

    2011-03-01

    The diffusive gradients in thin films (DGT) technique, using a diffusive gel or a restrictive gel, was evaluated for the determination of labile inorganic and organic species of Al and Cu in model synthetic solutions and river water samples. Experiments were performed both in situ and in the laboratory. In the solutions containing Al ions, the major labile fraction consisted of inorganic species. The organic complex fractions were mainly kinetically inert. For the model Cu solutions, the most labile fraction consisted of inorganic species; however, significant amounts of labile organic complexes of Cu were also present. A comparison was made between the results obtained using restrictive gel DGT and tangential flow ultrafiltration (TF-UF). The Cu fraction determined by restrictive gel DGT (corresponding to the "free" ions plus the labile fraction of small molecular size complexes) was larger than that determined by TF-UF (corresponding to all small molecular size ions), suggesting that the techniques exhibited different porosities for discrimination of inorganic species. For the river water samples analyzed in the laboratory, less than 45% of the analytes were present in labile forms, with most being organic species. For the in situ measurements, the labile inorganic and organic fractions were larger than those obtained in the laboratory analyses. These differences could have been due to errors incurred during sample collection and storage. All results were consistent with those found using two different methods, namely, solid-phase extraction and the DGT technique employing the apparent diffusion coefficient.

  17. A truncated diphtheria toxin based recombinant porcine CTLA-4 fusion toxin.

    PubMed

    Peraino, Jaclyn Stromp; Schenk, Marian; Zhang, Huiping; Li, Guoying; Hermanrud, Christina E; Neville, David M; Sachs, David H; Huang, Christene A; Duran-Struuck, Raimon; Wang, Zhirui

    2013-05-31

    Targeted cell therapies are possible through the generation of recombinant fusion proteins that combine a toxin, such as diphtheria toxin (DT), with an antibody or other molecule that confers specificity. Upon binding of the fusion protein to the cell of interest, the diphtheria toxin is internalized which results in protein synthesis inhibition and subsequent cell death. We have recently expressed and purified the recombinant soluble porcine CTLA-4 both with and without N-glycosylation in yeast Pichia pastoris for in vivo use in our preclinical swine model. The glycosylated and non-N-glycosylated versions of this recombinant protein each bind to a porcine CD80 expressing B-cell lymphoma line (LCL13271) with equal affinity (K(D)=13 nM). In this study we have linked each of the glycosylated and non-N-glycosylated soluble porcine CTLA-4 proteins to the truncated diphtheria toxin DT390 through genetic engineering yielding three versions of the porcine CTLA-4 fusion toxins: 1) monovalent glycosylated soluble porcine CTLA-4 fusion toxin; 2) monovalent non-N-glycosylated soluble porcine CTLA-4 fusion toxin and 3) bivalent non-N-glycosylated soluble porcine CTLA-4 fusion toxin. Protein synthesis inhibition analysis demonstrated that while all three fusion toxins are capable of inhibiting protein synthesis in vitro, the non-N-glycosylated porcine CTLA-4 isoforms function most efficiently. Binding analysis using flow cytometry of the porcine CTLA-4 fusion toxins to LCL13271 cells also demonstrated that the non-N-glycosylated porcine CTLA-4 isoforms bind to these cells with higher affinity compared to the glycosylated fusion toxin. The monovalent non-N-glycosylated porcine CTLA-4 fusion toxin was tested in vivo. NSG (NOD/SCID IL-2 receptor γ(-)/(-)) mice were injected with porcine CD80(+) LCL13271 tumor cells. All animals succumbed to tumors and those treated with the monovalent non-N-glycosylated porcine CTLA-4 fusion toxin survived longer based on a symptomatic scoring

  18. Genetic characteristics of toxigenic Clostridia and toxin gene evolution.

    PubMed

    Popoff, Michel R; Bouvet, Philippe

    2013-12-01

    Clostridia comprise a heterogenous group of environmental bacteria containing 15 pathogenic species, which produce the most potent toxins. The origin of toxins is still enigmatic. It is hypothesized that toxins exhibiting an enzymatic activity have derived from hydrolytic enzymes, which are abundantly secreted by these bacteria, and that pore-forming toxins have evolved from an ancestor transmembrane protein. The presence of related toxin genes in distinct Clostridium species and the variability of some toxin genes support horizontal toxin gene transfer and subsequent independent evolution from strain to strain. Clostridium perfringens toxin genes involved in myonecrosis, mainly alpha toxin and perfringolysin genes, are chromosomally located, whereas toxin genes responsible for intestinal and food borne diseases are localized on plasmids except the enterotoxin gene which can be located either on the chromosome or plasmids. The distribution of these plasmids containing one or several toxin genes accounts for the diverse C. perfringens toxinotypes. Clostridium difficile strains show a high genetic variability. But in contrast to C. perfringens, toxin genes are clustered in pathogenicity locus located on chromosome. The presence of related toxin genes in distinct clostridial species like Clostridium sordellii, Clostridium novyi, and C. perfringens supports interspecies mobilization of this locus. The multiple C. difficile toxinotypes based on toxin gene variants possibly reflect strain adaptation to the intestinal environment. Botulinum toxin genes also show a high level of genetic variation. They have a diverse genetic localization including chromosome, plasmid or phage, and are spread in various Clostridium species (Clostridium botulinum groups, Clostridium argentinense, Clostridium butyricum, Clostridium baratii). Exchange of toxin genes not only include transfers between Clostridium species but also between Clostridium and other bacterial species as well as

  19. Acid-labile sulfides in shallow marine bottom sediments: A review of the impact on ecosystems in the Azov Sea, the NE Black Sea shelf and NW Adriatic lagoons

    NASA Astrophysics Data System (ADS)

    Sorokin, Yu. I.; Zakuskina, O. Yu

    2012-02-01

    Acid-labile sulfides (LS) increase in bottom sediments at sites in the Azov Sea, at the NE Black Sea shelf and in the coastal lagoons of NW Adriatic Sea experiencing direct impacts of anthropogenic pollution. Fresh anthropogenic organic matter stimulates the bacterial sulfate reduction and here the rate of the LS production overcomes their loss during the oxidation and pyritization. This results in the expansion of reduced sediment layer up to the bottom surface. The LS concentration in the reduced sediments varies between 300 and 2000 mg S l -1 of wet silt depending on the size of pollution loading and on the rate of sedimentation. In the oxidized sediments away from the direct pollution impact, the LS concentration did not exceed 100-150 mg S l -1. Being a strong cytochrome toxin, the LS adversely affect the coastal ecosystems. The concentrations over 600 mg S l -1 result in quasi total benthic mortality whereas >300-400 mg S l -1 depletes the benthic faunal abundance and taxonomic diversity. Accumulation of the LS in sediments also induces nocturnal hypoxia and stimulates domination of toxic cyanobacteria in the pelagic phytocenoses.

  20. Heat pipe array heat exchanger

    DOEpatents

    Reimann, Robert C.

    1987-08-25

    A heat pipe arrangement for exchanging heat between two different temperature fluids. The heat pipe arrangement is in a ounterflow relationship to increase the efficiency of the coupling of the heat from a heat source to a heat sink.

  1. Methods for the detection of marine toxins

    SciTech Connect

    Wekell, M.M.; Manger, R.M.; Hadley, S.W.; Hungerford, J.M.

    1995-12-01

    Toxic materials have been dumped into the seas from waste streams and other pollutant sources such as runoff, etc. For protection of public health, it is essential that rapid, reliable and simple methods exist to detect marine toxins in seafoods. In addition, it is necessary to develop methods requiring a minimum of test material. Pure standards for many of the marine toxins are scarce. Reduced sample requirements extend the utility of detection methods in research and forensic applications as well. In the past, there was much reliance on the animal bioassay; however, this dependence hopefully will be reduced as newer instrumental techniques (chromatographic, mass spectrometric, electrophoretic), biochemical (immunochemical, receptor site assay), and cell bioassay methods are developed with a higher degree of precision and specificity. It is beneficial that a multiplicity of methods be available to detect marine toxins in seafoods. Each method has unique advantages and disadvantages.

  2. Toxin-Deficient Mutants from a Toxin-Sensitive Transformant of Cochliobolus Heterostrophus

    PubMed Central

    Yang, G.; Turgeon, B. G.; Yoder, O. C.

    1994-01-01

    Tox1 is the only genetic element identified which controls production of T-toxin, a linear polyketide involved in the virulence of Cochliobolus heterostrophus to its host plant, corn. Previous attempts to induce toxin-deficient (Tox(-)) mutants, using conventional mutagenesis and screening procedures, have been unsuccessful. As a strategy to enrich for Tox(-) mutants, we constructed a Tox1(+) strain that carried the corn T-urf13 gene (which confers T-toxin sensitivity) fused to a fungal mitochondrial signal sequence; the fusion was under control of the inducible Aspergillus nidulans pelA promoter which, in both A. nidulans and C. heterostrophus, is repressed by glucose and induced by polygalacturonic acid (PGA). We expected that a transformant carrying this construction would be sensitive to its own toxin when the T-urf13 gene was expressed. Indeed, the strain grew normally on medium containing glucose but was inhibited on medium containing PGA. Conidia of this strain were treated with ethylmethanesulfonate and plated on PGA medium. Among 362 survivors, 9 were defective in T-toxin production. Authenticity of each mutant was established by the presence of the transformation vector, proper mating type, and a restiction fragment length polymorphism tightly linked to the Tox1(+) locus. Progeny of each mutant crossed to a Tox1(+) tester segregated 1:1 (for wild type toxin production vs. no or reduced toxin production), indicating a single gene mutation in each case. Progeny of each mutant crossed to a Tox1(-) tester segregated 1 : 1 (for no toxin production vs. no or reduced toxin production) indicating that each mutation mapped at the Tox1 locus. Availability of Tox(-) mutants will permit mapping in the Tox1 region without interference from a known Tox1 linked translocation breakpoint. PMID:8088521

  3. Retrograde trafficking of AB₅ toxins: mechanisms to therapeutics.

    PubMed

    Mukhopadhyay, Somshuvra; Linstedt, Adam D

    2013-10-01

    Bacterial AB5 toxins are a clinically relevant class of exotoxins that include several well-known members such as Shiga, cholera, and pertussis toxins. Infections with toxin-producing bacteria cause devastating human diseases that affect millions of individuals each year and have no definitive medical treatment. The molecular targets of AB5 toxins reside in the cytosol of infected cells, and the toxins reach the cytosol by trafficking through the retrograde membrane transport pathway that avoids degradative late endosomes and lysosomes. Focusing on Shiga toxin as the archetype member, we review recent advances in understanding the molecular mechanisms involved in the retrograde trafficking of AB5 toxins and highlight how these basic science advances are leading to the development of a promising new therapeutic approach based on inhibiting toxin transport.

  4. Modulation of TRP ion channels by venomous toxins.

    PubMed

    Siemens, Jan; Hanack, Christina

    2014-01-01

    Venoms are evolutionarily fine-tuned mixtures of small molecules, peptides, and proteins-referred to as toxins-that have evolved to specifically modulate and interfere with the function of diverse molecular targets within the envenomated animal. Many of the identified toxin targets are membrane receptors and ion channels. Due to their high specificity, toxins have emerged as an invaluable tool set for the molecular characterization of ion channels, and a selected group of toxins even have been developed into therapeutics. More recently, TRP ion channels have been included as targets for venomous toxins. In particular, a number of apparently unrelated peptide toxins target the capsaicin receptor TRPV1 to produce inflammatory pain. These toxins have turned out to be invaluable for structural and functional characterizations of the capsaicin receptor. If toxins will serve similar roles for other TRP ion channels, only future will tell.

  5. CAUSE OF IMMEDIATE DEATH BY LARGE DOSES OF BOTULINUS TOXIN.

    PubMed

    Bronfenbrenner, J J; Schlesinger, M J; Orr, P F

    1924-06-30

    Parenteral introduction of amounts of the culture filtrate of Bacillus botulinus greatly in excess of the minimum lethal dose has been observed to cause the practically immediate death of mice. This result is due to the presence in the filtrates of a chemical poison possessing properties distinct from those of the contained botulinus toxin which itself acts only after a well defined period of incubation. This chemical poison is not neutralized by botulinus antitoxin; it is effective only when large amounts of the culture filtrate are given; it is thermostable, not being destroyed when heated in the autoclave in a sealed tube, though when it is heated in an open container its toxicity diminishes with a coincidental volatilization of basic material. The volatile substance can be identified as ammonia. Death resulting from the injection of comparatively large amounts of ammonium salts (0.1 gm.) is easily distinguished from that due to botulism, both through the character of the symptoms and the absence of an incubation period. However, when the amount of toxic salts injected is smaller (0.01 gm.), the symptoms of poisoning are not so characteristic and death may be delayed long enough to suggest a period of incubation similar to that observed in botulism (Table IV). This circumstance is of importance in connection with the examination of partly decomposed food products in which the presence of botulinus toxin is suspected. As a rule such suspected material is injected in massive doses (0.5 to 1 cc.) in mice. It is conceivable that such spoiled foods may be contaminated with common putrefactive bacteria yielding ammonia during their growth and thus may cause death of the test animals. If in such tests mice passively protected by the preliminary injection of an excess of antitoxin be used in addition to normal animals, the chances of an error in the interpretation of the results will be materially reduced, though not ruled out. Unfortunately for such a procedure

  6. Functional RelBE-Family Toxin-Antitoxin Pairs Affect Biofilm Maturation and Intestine Colonization in Vibrio cholerae

    PubMed Central

    Hay, Amanda J.; Zhong, Zengtao; Zhu, Jun; Kan, Biao

    2015-01-01

    Toxin–antitoxin (TA) systems are small genetic elements that typically encode a stable toxin and its labile antitoxin. These cognate pairs are abundant in prokaryotes and have been shown to regulate various cellular functions. Vibrio cholerae, a human pathogen that is the causative agent of cholera, harbors at least thirteen TA loci. While functional HigBA, ParDE have been shown to stabilize plasmids and Phd/Doc to mediate cell death in V. cholerae, the function of seven RelBE-family TA systems is not understood. In this study we investigated the function of the RelBE TA systems in V. cholerae physiology and found that six of the seven relBE loci encoded functional toxins in E. coli. Deletion analyses of each relBE locus indicate that RelBE systems are involved in biofilm formation and reactive oxygen species (ROS) resistance. Interestingly, all seven relBE loci are induced under the standard virulence induction conditions and two of the relBE mutants displayed a colonization defect, which was not due to an effect on virulence gene expression. Although further studies are needed to characterize the mechanism of action, our study reveals that RelBE systems are important for V. cholerae physiology. PMID:26275048

  7. Marine Toxins Targeting Ion Channels

    PubMed Central

    Arias, Hugo R.

    2006-01-01

    This introductory minireview points out the importance of ion channels for cell communication. The basic concepts on the structure and function of ion channels triggered by membrane voltage changes, the so-called voltage-gated ion channels (VGICs), as well as those activated by neurotransmitters, the so-called ligand-gated ion channel (LGICs), are introduced. Among the most important VGIC superfamiles, we can name the voltage-gated Na+ (NaV), Ca2+ (CaV), and K+ (KV) channels. Among the most important LGIC super families, we can include the Cys-loop or nicotinicoid, the glutamate-activated (GluR), and the ATP-activated (P2XnR) receptor superfamilies. Ion channels are transmembrane proteins that allow the passage of different ions in a specific or unspecific manner. For instance, the activation of NaV, CaV, or KV channels opens a pore that is specific for Na+, Ca2+, or K+, respectively. On the other hand, the activation of certain LGICs such as nicotinic acetylcholine receptors, GluRs, and P2XnRs allows the passage of cations (e.g., Na+, K+, and/or Ca2+), whereas the activation of other LGICs such as type A γ-butyric acid and glycine receptors allows the passage of anions (e.g., Cl− and/or HCO3−). In this regard, the activation of NaV and CaV as well as ligand-gated cation channels produce membrane depolarization, which finally leads to stimulatory effects in the cell, whereas the activation of KV as well as ligand-gated anion channels induce membrane hyperpolarization that finally leads to inhibitory effects in the cell. The importance of these ion channel superfamilies is emphasized by considering their physiological functions throughout the body as well as their pathophysiological implicance in several neuronal diseases. In this regard, natural molecules, and especially marine toxins, can be potentially used as modulators (e.g., inhibitors or prolongers) of ion channel functions to treat or to alleviate a specific ion channel-linked disease (e

  8. Dual, differential isotope labeling shows the preferential movement of labile plant constituents into mineral-bonded soil organic matter.

    PubMed

    Haddix, Michelle L; Paul, Eldor A; Cotrufo, M Francesca

    2016-06-01

    The formation and stabilization of soil organic matter (SOM) are major concerns in the context of global change for carbon sequestration and soil health. It is presently believed that lignin is not selectively preserved in soil and that chemically labile compounds bonding to minerals comprise a large fraction of the SOM. Labile plant inputs have been suggested to be the main precursor of the mineral-bonded SOM. Litter decomposition and SOM formation are expected to have temperature sensitivity varying with the lability of plant inputs. We tested this framework using dual (13) C and (15) N differentially labeled plant material to distinguish the metabolic and structural components within a single plant material. Big Bluestem (Andropogon gerardii) seedlings were grown in an enriched (13) C and (15) N environment and then prior to harvest, removed from the enriched environment and allowed to incorporate natural abundance (13) C-CO2 and (15) N fertilizer into the metabolic plant components. This enabled us to achieve a greater than one atom % difference in (13) C between the metabolic and structural components within the plant litter. This differentially labeled litter was incubated in soil at 15 and 35 °C, for 386 days with CO2 measured throughout the incubation. After 14, 28, 147, and 386 days of incubation, the soil was subsequently fractionated. There was no difference in temperature sensitivity of the metabolic and structural components with regard to how much was respired or in the amount of litter biomass stabilized. Only the metabolic litter component was found in the sand, silt, or clay fraction while the structural component was exclusively found in the light fraction. These results support the stabilization framework that labile plant components are the main precursor of mineral-associated organic matter. PMID:27142168

  9. Natural Toxins for Use in Pest Management

    PubMed Central

    Duke, Stephen O.; Cantrell, Charles L.; Meepagala, Kumudini M.; Wedge, David E.; Tabanca, Nurhayat; Schrader, Kevin K.

    2010-01-01

    Natural toxins are a source of new chemical classes of pesticides, as well as environmentally and toxicologically safer molecules than many of the currently used pesticides. Furthermore, they often have molecular target sites that are not exploited by currently marketed pesticides. There are highly successful products based on natural compounds in the major pesticide classes. These include the herbicide glufosinate (synthetic phosphinothricin), the spinosad insecticides, and the strobilurin fungicides. These and other examples of currently marketed natural product-based pesticides, as well as natural toxins that show promise as pesticides from our own research are discussed. PMID:22069667

  10. Streptococcal toxins: role in pathogenesis and disease.

    PubMed

    Barnett, Timothy C; Cole, Jason N; Rivera-Hernandez, Tania; Henningham, Anna; Paton, James C; Nizet, Victor; Walker, Mark J

    2015-12-01

    Group A Streptococcus (Streptococcus pyogenes), group B Streptococcus (Streptococcus agalactiae) and Streptococcus pneumoniae (pneumococcus) are host-adapted bacterial pathogens among the leading infectious causes of human morbidity and mortality. These microbes and related members of the genus Streptococcus produce an array of toxins that act against human cells or tissues, resulting in impaired immune responses and subversion of host physiological processes to benefit the invading microorganism. This toxin repertoire includes haemolysins, proteases, superantigens and other agents that ultimately enhance colonization and survival within the host and promote dissemination of the pathogen.

  11. Inhibiting bacterial toxins by channel blockage.

    PubMed

    Bezrukov, Sergey M; Nestorovich, Ekaterina M

    2016-03-01

    Emergent rational drug design techniques explore individual properties of target biomolecules, small and macromolecule drug candidates, and the physical forces governing their interactions. In this minireview, we focus on the single-molecule biophysical studies of channel-forming bacterial toxins that suggest new approaches for their inhibition. We discuss several examples of blockage of bacterial pore-forming and AB-type toxins by the tailor-made compounds. In the concluding remarks, the most effective rationally designed pore-blocking antitoxins are compared with the small-molecule inhibitors of ion-selective channels of neurophysiology.

  12. Regulation of Toxin Production in Clostridium perfringens

    PubMed Central

    Ohtani, Kaori; Shimizu, Tohru

    2016-01-01

    The Gram-positive anaerobic bacterium Clostridium perfringens is widely distributed in nature, especially in soil and the gastrointestinal tracts of humans and animals. C. perfringens causes gas gangrene and food poisoning, and it produces extracellular enzymes and toxins that are thought to act synergistically and contribute to its pathogenesis. A complicated regulatory network of toxin genes has been reported that includes a two-component system for regulatory RNA and cell-cell communication. It is necessary to clarify the global regulatory system of these genes in order to understand and treat the virulence of C. perfringens. We summarize the existing knowledge about the regulatory mechanisms here. PMID:27399773

  13. Impact of CDT Toxin on Human Diseases

    PubMed Central

    Faïs, Tiphanie; Delmas, Julien; Serres, Arnaud; Bonnet, Richard; Dalmasso, Guillaume

    2016-01-01

    Cytolethal distending toxin (CDT) is found in Gram-negative bacteria, especially in certain Proteobacteria such as the Pasteurellaceae family, including Haemophilus ducreyi and Aggregatibacter (Actinobacillus) actinomycetemcomitans, in the Enterobacteriaceae family and the Campylobacterales order, including the Campylobacter and Helicobacter species. In vitro and in vivo studies have clearly shown that this toxin has a strong effect on cellular physiology (inflammation, immune response modulation, tissue damage). Some works even suggest a potential involvement of CDT in cancers. In this review, we will discuss these different aspects. PMID:27429000

  14. CD44 Binding to Hyaluronic Acid Is Redox Regulated by a Labile Disulfide Bond in the Hyaluronic Acid Binding Site

    PubMed Central

    Kellett-Clarke, Helena; Stegmann, Monika; Barclay, A. Neil; Metcalfe, Clive

    2015-01-01

    CD44 is the primary leukocyte cell surface receptor for hyaluronic acid (HA), a component of the extracellular matrix. Enzymatic post translational cleavage of labile disulfide bonds is a mechanism by which proteins are structurally regulated by imparting an allosteric change and altering activity. We have identified one such disulfide bond in CD44 formed by Cys77 and Cys97 that stabilises the HA binding groove. This bond is labile on the surface of leukocytes treated with chemical and enzymatic reducing agents. Analysis of CD44 crystal structures reveal the disulfide bond to be solvent accessible and in the–LH hook configuration characteristic of labile disulfide bonds. Kinetic trapping and binding experiments on CD44-Fc chimeric proteins show the bond is preferentially reduced over the other disulfide bonds in CD44 and reduction inhibits the CD44-HA interaction. Furthermore cells transfected with CD44 no longer adhere to HA coated surfaces after pre-treatment with reducing agents. The implications of CD44 redox regulation are discussed in the context of immune function, disease and therapeutic strategies. PMID:26379032

  15. Hourly Fluctuations in Labile Soil Phosphorus in Response to Climate Variability in a Wet Tropical Forest, La Selva, Costa Rica

    NASA Astrophysics Data System (ADS)

    Vandecar, K. L.; Lawrence, D. C.; Das, R.; Clark, D. A.; Oberbauer, S. F.; Schwendenmann, L.

    2007-05-01

    Tropical rain forests are one of the most productive ecosystems in the world and play a significant role in the global carbon budget. Changes in phosphorus cycling dynamics as a result of on-going climate change have the potential to limit productivity in this ecosystem. Our objective was to determine hourly patterns in labile soil phosphorus throughout the day and explore possible mechanisms driving these patterns. We conducted an in situ experiment on soils from a wet tropical forest at La Selva Biological Station located in N.E. Costa Rica. A variety of climatic and biotic variables including temperature, precipitation, PAR, soil temperature, soil moisture and soil respiration were measured in order to determine their effect on labile phosphorus. Our results indicate that labile phosphorus does vary significantly throughout the day in response to a combination of climatic variables. An understanding of the mechanisms driving phosphorus availability at fine temporal scales can provide a valuable indicator of long term trends in phosphorus cycling dynamics.

  16. High-throughput production of two disulphide-bridge toxins.

    PubMed

    Upert, Grégory; Mourier, Gilles; Pastor, Alexandra; Verdenaud, Marion; Alili, Doria; Servent, Denis; Gilles, Nicolas

    2014-08-01

    A quick and efficient production method compatible with high-throughput screening was developed using 36 toxins belonging to four different families of two disulphide-bridge toxins. Final toxins were characterized using HPLC co-elution, CD and pharmacological studies.

  17. Military Importance of Natural Toxins and Their Analogs.

    PubMed

    Pitschmann, Vladimír; Hon, Zdeněk

    2016-04-28

    Toxin weapon research, development, production and the ban on its uses is an integral part of international law, with particular attention paid to the protection against these weapons. In spite of this, hazards associated with toxins cannot be completely excluded. Some of these hazards are also pointed out in the present review. The article deals with the characteristics and properties of natural toxins and synthetic analogs potentially constituting the basis of toxin weapons. It briefly describes the history of military research and the use of toxins from distant history up to the present age. With respect to effective disarmament conventions, it mentions certain contemporary concepts of possible toxin applications for military purposes and the protection of public order (suppression of riots); it also briefly refers to the question of terrorism. In addition, it deals with certain traditional as well as modern technologies of the research, synthesis, and use of toxins, which can affect the continuing development of toxin weapons. These are, for example, cases of new toxins from natural sources, their chemical synthesis, production of synthetic analogs, the possibility of using methods of genetic engineering and modern biotechnologies or the possible applications of nanotechnology and certain pharmaceutical methods for the effective transfer of toxins into the organism. The authors evaluate the military importance of toxins based on their comparison with traditional chemical warfare agents. They appeal to the ethics of the scientific work as a principal condition for the prevention of toxin abuse in wars, military conflicts, as well as in non-military attacks.

  18. EFFECTS OF MARINE ALGAL TOXINS ON THERMOREGULATION IN MICE.

    EPA Science Inventory

    Hypothermia is often seen in mice and rats exposed acutely to marine algal toxins, but the mechanism of action of these toxins on thermoregulation is not well understood. Our laboratory has assessed the thermoregulatory mechanisms of two marine algal toxins, maitotoxin and brevet...

  19. Anthrax toxin-induced rupture of artificial lipid bilayer membranes

    NASA Astrophysics Data System (ADS)

    Nablo, Brian J.; Panchal, Rekha G.; Bavari, Sina; Nguyen, Tam L.; Gussio, Rick; Ribot, Wil; Friedlander, Art; Chabot, Donald; Reiner, Joseph E.; Robertson, Joseph W. F.; Balijepalli, Arvind; Halverson, Kelly M.; Kasianowicz, John J.

    2013-08-01

    We demonstrate experimentally that anthrax toxin complexes rupture artificial lipid bilayer membranes when isolated from the blood of infected animals. When the solution pH is temporally acidified to mimic that process in endosomes, recombinant anthrax toxin forms an irreversibly bound complex, which also destabilizes membranes. The results suggest an alternative mechanism for the translocation of anthrax toxin into the cytoplasm.

  20. Heating with waste heat

    SciTech Connect

    Beabout, R.W.

    1986-09-02

    Most of the power consumed in the gaseous diffusion process is converted into heat of compression, which is removed from the process gas and rejected into the atmosphere by recirculating cooling water over cooling towers. The water being handled through the X-333 and X-330 Process Buildings can be heated to 140 to 150/sup 0/F for heating use. The Gas Centrifuge Enrichment Plant is provided with a recirculating heating water (RHW) system which uses X-330 water and wasted heat. The RHW flow is diagrammed. (DLC)

  1. Labile sleep promotes awareness of abstract knowledge in a serial reaction time task

    PubMed Central

    Kirov, Roumen; Kolev, Vasil; Verleger, Rolf; Yordanova, Juliana

    2015-01-01

    Sleep has been identified as a critical brain state enhancing the probability of gaining insight into covert task regularities. Both non-rapid eye movement (NREM) and rapid eye movement (REM) sleep have been implicated with offline re-activation and reorganization of memories supporting explicit knowledge generation. According to two-stage models of sleep function, offline processing of information during sleep is sequential requiring multiple cycles of NREM and REM sleep stages. However, the role of overnight dynamic sleep macrostructure for insightfulness has not been studied so far. In the present study, we test the hypothesis that the frequency of interactions between NREM and REM sleep stages might be critical for awareness after sleep. For that aim, the rate of sleep stage transitions was evaluated in 53 participants who learned implicitly a serial reaction time task (SRTT) in which a determined sequence was inserted. The amount of explicit knowledge about the sequence was established by verbal recall after a night of sleep following SRTT learning. Polysomnography was recorded in this night and in a control night before and was analyzed to compare the rate of sleep-stage transitions between participants who did or did not gain awareness of task regularity after sleep. Indeed, individual ability of explicit knowledge generation was strongly associated with increased rate of transitions between NREM and REM sleep stages and between light sleep stages and slow wave sleep. However, the rate of NREM–REM transitions specifically predicted the amount of explicit knowledge after sleep in a trait-dependent way. These results demonstrate that enhanced lability of sleep goes along with individual ability of knowledge awareness. Observations suggest that facilitated dynamic interactions between sleep stages, particularly between NREM and REM sleep stages play a role for offline processing which promotes rule extraction and awareness. PMID:26441730

  2. Profiling of structurally labile oxylipins in plants by in situ derivatization with pentafluorobenzyl hydroxylamine.

    PubMed

    Schulze, Birgit; Lauchli, Ryan; Sonwa, Mesmin Mekem; Schmidt, Annika; Boland, Wilhelm

    2006-01-15

    A GC-MS-based method for the simultaneous quantification of common oxylipins along with labile and highly reactive compounds based on in situ derivatization with pentafluorobenzyl hydroxylamine to the corresponding O-2,3,4,5,6-pentafluorobenzyl oximes (PFB oximes) is presented. The approach covers oxo derivatives such as jasmonic acid (JA), 12-oxophytodienoic acid (OPDA), certain phytoprostanes, unsaturated oxo-acids, oxo-hydroxy acids, and aldehyde fragments from the polar head of fatty acids. In the positive electron impact-MS mode, the PFB oximes display characteristic fragment ions that greatly facilitate the identification of oxylipins in complex matrices. In addition, the fluorinated derivatives allow a highly selective and low-background analysis by negative chemical ionization. Besides showing the general value of the method for the identification of a broad range of oxylipins (18 examples), we also demonstrate sensitivity, linearity, and reproducibility for the quantification of JA, OPDA, 11-oxo-9-undecenoic acid, and 13-oxo-9,11-tridecadienoic acid. The efficiency of the method is demonstrated by differential profiling of these four oxylipins in lima bean leaves after mechanical wounding and feeding by the herbivore Spodoptera littoralis. Caterpillar feeding induced several oxylipins, whereas after wounding only the level of JA increased. The rapid in situ derivatization prevents the isomerization of cis-JA to trans-JA. The resting level of JA in lima beans showed an isomer ratio of 80:20 for trans/cis-JA. After wounding, de novo synthesis of JA alters the ratio to 20:80 in favor of the cis isomer.

  3. Kinetics characterization of c-Src binding to lipid membranes: Switching from labile to persistent binding.

    PubMed

    Le Roux, Anabel-Lise; Busquets, Maria Antònia; Sagués, Francesc; Pons, Miquel

    2016-02-01

    Cell signaling by the c-Src proto-oncogen requires the attachment of the protein to the inner side of the plasma membrane through the myristoylated N-terminal region, known as the SH4 domain. Additional binding regions of lower affinity are located in the neighbor intrinsically disordered Unique domain and the structured SH3 domain. Here we present a surface plasmon resonance study of the binding of a myristoylated protein including the SH4, Unique and SH3 domains of c-Src to immobilized liposomes. Two distinct binding processes were observed: a fast and a slow one. The second process lead to a persistently bound form (PB) with a slower binding and a much slower dissociation rate than the first one. The association and dissociation of the PB form could be detected using an anti-SH4 antibody. The kinetic analysis revealed that binding of the PB form follows a second order rate law suggesting that it involves the formation of c-Src dimers on the membrane surface. A kinetically equivalent PB form is observed in a myristoylated peptide containing only the SH4 domain but not in a construct including the three domains but with a 12-carbon lauroyl substituent instead of the 14-carbon myristoyl group. The PB form is observed with neutral lipids but its population increases when the immobilized liposomes contain negatively charged lipids. We suggest that the PB form may represent the active signaling form of c-Src while the labile form provides the capacity for fast 2D search of the target signaling site on the membrane surface. PMID:26638178

  4. Controls on the composition and lability of dissolved organic matter in Siberia's Kolyma River basin

    NASA Astrophysics Data System (ADS)

    Mann, P. J.; Davydova, A.; Zimov, N.; Spencer, R. G. M.; Davydov, S.; Bulygina, E.; Zimov, S.; Holmes, R. M.

    2012-03-01

    High-latitude northern rivers export globally significant quantities of dissolved organic carbon (DOC) to the Arctic Ocean. Climate change, and its associated impacts on hydrology and potential mobilization of ancient organic matter from permafrost, is likely to modify the flux, composition, and thus biogeochemical cycling and fate of exported DOC in the Arctic. This study examined DOC concentration and the composition of dissolved organic matter (DOM) across the hydrograph in Siberia's Kolyma River, with a particular focus on the spring freshet period when the majority of the annual DOC load is exported. The composition of DOM within the Kolyma basin was characterized using absorbance-derived measurements (absorbance coefficienta330, specific UV absorbance (SUVA254), and spectral slope ratio SR) and fluorescence spectroscopy (fluorescence index and excitation-emission matrices (EEMs)), including parallel factor analyses of EEMs. Increased surface runoff during the spring freshet led to DOM optical properties indicative of terrestrial soil inputs with high humic-like fluorescence, SUVA254, and low SRand fluorescence index (FI). Under-ice waters, in contrast, displayed opposing trends in optical properties representing less aromatic, lower molecular weight DOM. We demonstrate that substantial losses of DOC can occur via biological (˜30% over 28 days) and photochemical pathways (>29% over 14 days), particularly in samples collected during the spring freshet. The emerging view is therefore that of a more dynamic and labile carbon pool than previously thought, where DOM composition plays a fundamental role in controlling the fate and removal of DOC at a pan-Arctic scale.

  5. [Effects of understory removal on soil labile organic carbon pool in a Cinnamomum camphora plantation].

    PubMed

    Wu, Ya-Cong; Li, Zheng-Cai; Cheng, Cai-Fang; Liu, Rong-Jie; Wang, Bin; Geri, Le-Tu

    2013-12-01

    Taking a 48-year-old Cinnamomum camphora plantation in the eastern area of our subtropics as test object, this paper studied the labile organic carbon contents and their ratios to the total organic carbon (TOC) in 0-60 cm soil layer under effects of understory removal (UR). As compared with no understory removal (CK), the soil TOC and easily-oxidized carbon (EOC) contents under UR decreased, with a decrement of 4.8% - 34.1% and 27.1% - 36.2%, respectively, and the TOC and EOC contents had a significant difference in 0-10 cm and 0-20 cm layers, respectively. The water-soluble organic carbon (WSOC) (except in 0-10 cm and 10-20 cm layers) and light fraction organic matter (LFOM) under UR increaesd, but the difference was not significant. The ratio of soil WSOC to soil TOC in UR stand was higher than that in CK stand, while the ratio of soil EOC to soil TOC showed an opposite trend. In the two stands, soil WSOC, EOC, and LFOM had significant or extremely significant correlations with soil TOC, and the correlation coefficients of soil EOC and LFOM with soil TOC were higher in UR stand than in CK, but the correlation coefficient between soil WSOC and TOC was in opposite. The soil EOC, LFOM, and TOC in the two stands were significantly or extremely significantly correlated with soil nutrients, but the soil WSOC in UR stand had no significant correlations with soil hydrolyzable N, available P, exchangeable Ca, and exchangeable Mg.

  6. Kinetics characterization of c-Src binding to lipid membranes: Switching from labile to persistent binding.

    PubMed

    Le Roux, Anabel-Lise; Busquets, Maria Antònia; Sagués, Francesc; Pons, Miquel

    2016-02-01

    Cell signaling by the c-Src proto-oncogen requires the attachment of the protein to the inner side of the plasma membrane through the myristoylated N-terminal region, known as the SH4 domain. Additional binding regions of lower affinity are located in the neighbor intrinsically disordered Unique domain and the structured SH3 domain. Here we present a surface plasmon resonance study of the binding of a myristoylated protein including the SH4, Unique and SH3 domains of c-Src to immobilized liposomes. Two distinct binding processes were observed: a fast and a slow one. The second process lead to a persistently bound form (PB) with a slower binding and a much slower dissociation rate than the first one. The association and dissociation of the PB form could be detected using an anti-SH4 antibody. The kinetic analysis revealed that binding of the PB form follows a second order rate law suggesting that it involves the formation of c-Src dimers on the membrane surface. A kinetically equivalent PB form is observed in a myristoylated peptide containing only the SH4 domain but not in a construct including the three domains but with a 12-carbon lauroyl substituent instead of the 14-carbon myristoyl group. The PB form is observed with neutral lipids but its population increases when the immobilized liposomes contain negatively charged lipids. We suggest that the PB form may represent the active signaling form of c-Src while the labile form provides the capacity for fast 2D search of the target signaling site on the membrane surface.

  7. Conformational Switching and Nanoscale Assembly of Human Prion Protein into Polymorphic Amyloids via Structurally Labile Oligomers.

    PubMed

    Dalal, Vijit; Arya, Shruti; Bhattacharya, Mily; Mukhopadhyay, Samrat

    2015-12-29

    Conformational switching of the prion protein (PrP) from an α-helical normal cellular form (PrP(C)) to an aggregation-prone and self-propagating β-rich scrapie form (PrP(Sc)) underlies the molecular basis of pathogenesis in prion diseases. Anionic lipids play a critical role in the misfolding and conformational conversion of the membrane-anchored PrP into the amyloidogenic pathological form. In this work, we have used a diverse array of techniques to interrogate the early intermediates during amyloid formation from recombinant human PrP in the presence of a membrane mimetic anionic detergent such as sodium dodecyl sulfate. We have been able to detect and characterize two distinct types of interconvertible oligomers. Our results demonstrate that highly ordered large β-oligomers represent benign off-pathway intermediates that lack the ability to mature into amyloid fibrils. On the contrary, structurally labile small oligomers are capable of switching to an ordered amyloid-state that exhibits profound toxicity to mammalian cells. Our fluorescence resonance energy transfer measurements revealed that the partially disordered PrP serves as precursors to small amyloid-competent oligomers. These on-pathway oligomers are eventually sequestered into higher order supramolecular assemblies that conformationally mature into polymorphic amyloids possessing varied nanoscale morphology as evident by the atomic force microscopy imaging. The nanoscale diversity of fibril architecture is attributed to the heterogeneous ensemble of early obligatory oligomers and offers a plausible explanation for the existence of multiple prion strains in vivo. PMID:26645611

  8. Effect of Fusarium toxins, T2-toxin and diacetoxyscirpenol on murine T-independent immune responses.

    PubMed Central

    Rosenstein, Y; Kretschmer, R R; Lafarge-Frayssinet, C

    1981-01-01

    Trichothecenes mycotoxins, T2-toxin and diacetoxyscirpenol were investigated for their effect upon T-independent murine immune responses. Both anti-polyvinylpyrrolidone and anti-dinitrophenylficoll responses were enhanced by chronic administration of these toxins. Spleen cells from T2-toxin-treated animals revealed significantly less Thy 1.2+ cells than controls. Spleen cells from Fusarium crude extract-treated animals had a depressed response to phytohaemagglutinin (PHA) as compared with controls. Normal recipients given spleen cells from T2-toxin-treated mice were shown to generate approximately 50% less plaque-forming cells against sheep red blood cells than controls. It is suggested that these effects occur as a result of altered T suppressor-cell function. PMID:6976308

  9. Interaction of cultured mammalian cells with [125I] diphtheria toxin.

    PubMed Central

    Bonventre, P F; Saelinger, C B; Ivins, B; Woscinski, C; Amorini, M

    1975-01-01

    The characteristics of cell adsorption and pinocytotic uptake of diphtheria toxin by several mammalian cell types were studied. Purified toxin iodinated by a solid-state lactoperoxidase method provided preparations of high specific activity and unaltered biological activity. Dephtheria toxin-sensitive HEp-2 cells and guinea pig macrophage cultures were compared with resistant mouse L-929 cells. At 37 C the resistant cells in monolayer adsorbed and internalized [125I] toxin to a greater extent than did the HEp-2 cell cultures; no significant differences were observed at 5 C. Ammonium chloride protection levels did not alter uptake of toxin by either L-929 OR HEp-2 cells. Biological activity of the iodinated toxin, however, was negated provided the presence of ammonium chloride was maintained. The ammonium salt appears to maintain toxin in a state amenable to antitoxin neutralization. Guinea pig macrophages internalized iodinated toxin to a level 10 times greater than the established cell lines. In spite of the increased uptake of toxin by the endocytic cells, ammonium chloride prevented expression of toxicity. In an artificial system, toxin adsorbed to polystyrene latex spheres and internalized by guinea pig macrophages during phagocytosis did express biological activity. Ammonium chloride afforded some but not total protection against toxin present in the phagocytic vacuoles. The data suggest that two mechanisms of toxin uptake by susceptible cells may be operative. Toxin taken into the cell by a pinocytotic process probably is not ordinarily of physiological significance since it is usually degraded by lysosomal enzymes before it can reach cytoplasmic constituents on which it acts. When large quantities of toxin are pinocytized, toxicity may be expressed before enzymatic degradation is complete. A more specific uptake involving direct passage of the toxin through the plasma membrane may be the mechanism leading to cell death in the majority of instances. PMID

  10. [Impact of Land Utilization Pattern on Distributing Characters of Labile Organic Carbon in Soil Aggregates in Jinyun Mountain].

    PubMed

    Li, Rui; Jiang, Chang-sheng; Hao, Qing-ju

    2015-09-01

    Four land utilization patterns were selected for this study in Jinyun mountain, including subtropical evergreen broad-leaved forest (abbreviation: forest), sloping farmland, orchard and abandoned land. Soil samples were taken every 10 cm in the depth of 60 cm soil and proportions of large macroaggregates (> 2 mm), small macroaggregates (0. 25-2 mm), microaggregates (0. 053 - 0. 25 mm) and silt + clay (<0. 053 mm) were obtained by wet sieving method to measure the content of organic carbon and labile organic carbon in each aggregate fraction and analyze impacts of land uses on organic carbon and labile organic carbon of soil aggregates. LOC content of four soil aggregates were significantly reduced with the increase of soil depth; in layers of 0-60 cm soil depth, our results showed that LOC contents of forest and abandoned land were higher than orchard and sloping farmland. Reserves of labile organic carbon were estimated by the same soil quality, it revealed that forest (3. 68 Mg.hm-2) > abandoned land (1. 73 Mg.hm-2) > orchard (1. 43 Mg.hm-2) >sloping farmland (0.54 Mg.hm-2) in large macroaggregates, abandoned land (7.77, 5. 01 Mg.hm-2) > forest (4. 96, 2.71 Mg.hm-2) > orchard (3. 33, 21. 10 Mg.hm-2) > sloping farmland (1. 68, 1. 35 Mg.hm-2) in small macroaggregates and microaggregates, and abandoned land(4. 32 Mg.hm-2) > orchard(4. 00 Mg.hm-2) > forest(3. 22 Mg.hm-2) > sloping farmland (2.37 Mg.hm-2) in silt + clay, forest and abandoned land were higher than orchard and sloping farmland in other three soil aggregates except silt + clay. It was observed that the level of organic carbon and labile organic carbon were decreased when bringing forest under cultivation to orchard or farmland, and augments on organic carbon and labile organic carbon were found after exchanging farmland to abandoned land. The most reverses of forest and abandoned land emerged in small macroaggregates, orchard and sloping farmland were in microaggregates. That was, during the

  11. [Impact of Land Utilization Pattern on Distributing Characters of Labile Organic Carbon in Soil Aggregates in Jinyun Mountain].

    PubMed

    Li, Rui; Jiang, Chang-sheng; Hao, Qing-ju

    2015-09-01

    Four land utilization patterns were selected for this study in Jinyun mountain, including subtropical evergreen broad-leaved forest (abbreviation: forest), sloping farmland, orchard and abandoned land. Soil samples were taken every 10 cm in the depth of 60 cm soil and proportions of large macroaggregates (> 2 mm), small macroaggregates (0. 25-2 mm), microaggregates (0. 053 - 0. 25 mm) and silt + clay (<0. 053 mm) were obtained by wet sieving method to measure the content of organic carbon and labile organic carbon in each aggregate fraction and analyze impacts of land uses on organic carbon and labile organic carbon of soil aggregates. LOC content of four soil aggregates were significantly reduced with the increase of soil depth; in layers of 0-60 cm soil depth, our results showed that LOC contents of forest and abandoned land were higher than orchard and sloping farmland. Reserves of labile organic carbon were estimated by the same soil quality, it revealed that forest (3. 68 Mg.hm-2) > abandoned land (1. 73 Mg.hm-2) > orchard (1. 43 Mg.hm-2) >sloping farmland (0.54 Mg.hm-2) in large macroaggregates, abandoned land (7.77, 5. 01 Mg.hm-2) > forest (4. 96, 2.71 Mg.hm-2) > orchard (3. 33, 21. 10 Mg.hm-2) > sloping farmland (1. 68, 1. 35 Mg.hm-2) in small macroaggregates and microaggregates, and abandoned land(4. 32 Mg.hm-2) > orchard(4. 00 Mg.hm-2) > forest(3. 22 Mg.hm-2) > sloping farmland (2.37 Mg.hm-2) in silt + clay, forest and abandoned land were higher than orchard and sloping farmland in other three soil aggregates except silt + clay. It was observed that the level of organic carbon and labile organic carbon were decreased when bringing forest under cultivation to orchard or farmland, and augments on organic carbon and labile organic carbon were found after exchanging farmland to abandoned land. The most reverses of forest and abandoned land emerged in small macroaggregates, orchard and sloping farmland were in microaggregates. That was, during the

  12. Functional and Structural Insights of a Staphylococcus aureus Apoptotic-like Membrane Peptide from a Toxin-Antitoxin Module*

    PubMed Central

    Sayed, Nour; Nonin-Lecomte, Sylvie; Réty, Stéphane; Felden, Brice

    2012-01-01

    We report a functional type I toxin-antitoxin (TA) module expressed by a human pathogen, Staphylococcus aureus. TA systems consist of stable toxins and labile antitoxins encoded within small genetic modules widespread in eubacteria and archaea. TA genes provide stress adaptation and protection against DNA loss or invasion. The genes encoding the SprA1 toxic peptide (PepA1) and the SprA1AS RNA antitoxin are within a pathogenicity island on opposite strands and possess a 3′ overlap. To prevent peptide toxicity during S. aureus growth, PepA1 expression from stable (half-life > 3 h) SprA1 is repressed by elevated amounts of unstable (half-life = ∼10 mn) SprA1AS. In vivo, PepA1 localizes at the bacterial membrane and triggers S. aureus death. Based on NMR and CD data, its solution structure was solved and is a long bent, interrupted helix. Molecular dynamics simulations indicate that PepA1 compaction and helical content fluctuate in accordance with its cytoplasm or membrane location. When inserted into the S. aureus membrane, the PepA1 conformation switches to a ∼7-nm-long continuous helix, presumably forming pores to alter membrane integrity. PepA1 expression is induced upon acidic and oxidative stresses by reducing SprA1AS levels. As an altruistic behavior during infection, some cells may induce the expression of that toxin that would facilitate departure from the host immune cells for spreading. PMID:23129767

  13. Botulinum Toxin in Neurogenic Detrusor Overactivity

    PubMed Central

    Ferreira, Rúiter Silva; Rassi, Mauricio Carneiro

    2012-01-01

    Purpose To evaluate the effects of botulinum toxin on urodynamic parameters and quality of life in patients with neurogenic detrusor overactivity. Methods Thirty four adult patients with spinal cord injury and detrusor overactivity were selected. The patients received 300 units of botulinum toxin type A. The endpoints evaluated with the episodes of urinary incontinence and measured the maximum cystometric capacity, maximum amplitude of detrusor pressure and bladder compliance at the beginning and end of the study (24 weeks) and evaluated the quality of life by applying the Qualiveen questionnaire. Results A significant decrease in the episodes of urinary incontinence was observed. All urodynamic parameters presented a significant improvement. The same was observed in the quality of life index and the specific impact of urinary problems scores from the Qualiveen questionnaire. Six patients did not complete the study, two due to incomplete follow-up, and four violated protocol and were excluded from the analyses. No systemic adverse events of botulinum toxin type A were reported. Conclusions A botulinum toxin type A showed a significantly improved response in urodynamics parameters and specific and general quality of life. PMID:23094220

  14. (-)-Botryodiplodin, A Unique Ribose Analog Toxin

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many toxins owe their mechanisms of action to being structural analogs of essential metabolites, messengers or structural components. Examples range from tubo-curare to penicillin. Ribose plays a unique role in the metabolism of living organisms, whether prokaryotes or eukaryotes. It and its deri...

  15. Toxins and antimicrobial peptides: interactions with membranes

    NASA Astrophysics Data System (ADS)

    Schlamadinger, Diana E.; Gable, Jonathan E.; Kim, Judy E.

    2009-08-01

    The innate immunity to pathogenic invasion of organisms in the plant and animal kingdoms relies upon cationic antimicrobial peptides (AMPs) as the first line of defense. In addition to these natural peptide antibiotics, similar cationic peptides, such as the bee venom toxin melittin, act as nonspecific toxins. Molecular details of AMP and peptide toxin action are not known, but the universal function of these peptides to disrupt cell membranes of pathogenic bacteria (AMPs) or a diverse set of eukaryotes and prokaryotes (melittin) is widely accepted. Here, we have utilized spectroscopic techniques to elucidate peptide-membrane interactions of alpha-helical human and mouse AMPs of the cathelicidin family as well as the peptide toxin melittin. The activity of these natural peptides and their engineered analogs was studied on eukaryotic and prokaryotic membrane mimics consisting of <200-nm bilayer vesicles composed of anionic and neutral lipids as well as cholesterol. Vesicle disruption, or peptide potency, was monitored with a sensitive fluorescence leakage assay. Detailed molecular information on peptidemembrane interactions and peptide structure was further gained through vibrational spectroscopy combined with circular dichroism. Finally, steady-state fluorescence experiments yielded insight into the local environment of native or engineered tryptophan residues in melittin and human cathelicidin embedded in bilayer vesicles. Collectively, our results provide clues to the functional structures of the engineered and toxic peptides and may impact the design of synthetic antibiotic peptides that can be used against the growing number of antibiotic-resistant pathogens.

  16. Botulinum toxin (botox) chemodenervation for facial rejuvenation.

    PubMed

    Carruthers, J; Carruthers, A

    2001-05-01

    A positive attitude toward life at any age is now seen to be consistent with inclusion in all societal activities. A mere increase in years is no longer enough reason for "ageism." Botulinum Toxin (Botox) aesthetic treatments, because of their outstanding effectiveness and safety, can continue to play a positive role in the rebuttal of "ageism." PMID:11457686

  17. Treatment of hyperhidrosis with botulinum toxin.

    PubMed

    Cohen, Joel L