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1

Evaluation and optimization of a latex agglutination assay for detection of cholera toxin and Escherichia coli heat-labile toxin.  

PubMed Central

The effectiveness of a latex agglutination assay kit for the detection of Escherichia coli heat-labile toxin and cholera toxin was determined for the identification of natural isolates of the corresponding enteric pathogens in Southeast Asia. By selection of the appropriate culture media, the sensitivity of the assay was improved from 90.6% (for the detection of heat-labile toxin) and 75% (for the detection of cholera toxin) to 100%, and the results were confirmed with bioassays and DNA hybridization assays for both clinical and environmental isolates.

Yam, W C; Lung, M L; Ng, M H

1992-01-01

2

Effects of exogenous agents on the action of Bordetella parapertussis heat-labile toxin on guinea pig skin.  

PubMed Central

Injection of sonic extracts of Bordetella parapertussis into the shaved backs of guinea pigs produced hemorrhagic necrosis, which previously has been attributed to the action of heat-labile toxin. As heat-labile toxin was purified from this crude mixture, its ability to induce hemorrhagic lesions decreased significantly. However, ischemic lesions were apparent after injection of the purified toxin. These lesions, while not hemorrhagic in nature, were marked by erythema surrounded by a region in which the ischemia was apparent. Exogenous agents were found to alter the nature of the skin lesion induced by heat-labile toxin. The lipid A portion of endotoxin in combination with heat-labile toxin caused hemorrhagic lesions surrounded by a ring of ischemia, whereas bovine serum albumin increased the area of erythema. While the nature of lesions induced by heat-labile toxin was affected by exogenous agents, the diameter of ischemia produced by the toxin was found to be independent of the presence of these agents and was linear with toxin dose. These results indicate that induction of hemorrhagic necrosis may not be a reliable indicator of heat-labile toxin activity. Instead, measurement of the ischemic lesion produced by heat-labile toxin may be a useful assay for the toxin. Images

Endoh, M; Nagai, M; Burns, D L; Manclark, C R; Nakase, Y

1990-01-01

3

Genetic Diversity of Heat-Labile Toxin Expressed by Enterotoxigenic Escherichia coli Strains Isolated from Humans  

Microsoft Academic Search

The natural diversity of the elt operons, encoding the heat-labile toxin LT-I (LT), carried by enterotoxigenic Escherichia coli (ETEC) strains isolated from humans was investigated. For many years, LT was supposed to be represented by a rather conserved toxin, and one derivative, produced by the reference H10407 strain, was intensively studied either as a virulence factor or as a vaccine

M. A. Lasaro; J. F. Rodrigues; C. Mathias-Santos; B. E. C. Guth; A. Balan; M. E. Sbrogio-Almeida; L. C. S. Ferreira

2008-01-01

4

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

PubMed Central

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

Spangler, B D

1992-01-01

5

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

PubMed

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. PMID:1480112

Spangler, B D

1992-12-01

6

Targeting of cholera toxin and Escherichia coli heat labile toxin in polarized epithelia: role of COOH-terminal KDEL.  

PubMed

Vibrio cholerae and Escherichia coli heat labile toxins (CT and LT) elicit a secretory response from intestinal epithelia by binding apical receptors (ganglioside GM1) and subsequently activating basolateral effectors (adenylate cyclase). We have recently proposed that signal transduction in polarized cells may require transcytosis of toxin-containing membranes (Lencer, W. I., G. Strohmeier, S. Moe, S. L. Carlson, C. T. Constable, and J. L. Madara. 1995. Proc. Natl. Acad. Sci. USA. 92:10094-10098). Targeting of CT into this pathway depends initially on binding of toxin B subunits to GM1 at the cell surface. The anatomical compartments in which subsequent steps of CT processing occur are less clearly defined. However, the enzymatically active A subunit of CT contains the ER retention signal KDEL (RDEL in LT). Thus if the KDEL motif were required for normal CT trafficking, movement of CT from the Golgi to ER would be implied. To test this idea, recombinant wild-type (wt) and mutant CT and LT were prepared. The COOH-terminal KDEL sequence in CT was replaced by seven unrelated amino acids: LEDERAS. In LT, a single point mutation replacing leucine with valine in RDEL was made. Wt and mutant toxins displayed similar enzymatic activities and binding affinities to GM1 immobilized on plastic. Biologic activity of recombinant toxins was assessed as a Cl- secretory response elicited from the polarized human epithelial cell line T84 using standard electrophysiologic techniques. Mutations in K(R)DEL of both CT and LT delayed the time course of toxin-induced Cl- secretion. At T1/2, dose dependencies for K(R)DEL-mutant toxins were increased > or = 10-fold. KDEL-mutants displayed differentially greater temperature sensitivity. In direct concordance with a slower rate of signal transduction. KDEL-mutants were trafficked to the basolateral membrane more slowly than wt CT (assessed by selective cell surface biotinylation as transcytosis of B subunit). Mutation in K(R)DEL had no effect on the rate of toxin endocytosis. These data provide evidence that CT and LT interact directly with endogenous KDEL-receptors and imply that both toxins may require retrograde movement through Golgi cisternae and ER for efficient and maximal biologic activity. PMID:7490296

Lencer, W I; Constable, C; Moe, S; Jobling, M G; Webb, H M; Ruston, S; Madara, J L; Hirst, T R; Holmes, R K

1995-11-01

7

Phase 1 Evaluation of Intranasal Virosomal Influenza Vaccine with and without Escherichia coli Heat-Labile Toxin in Adult Volunteers  

Microsoft Academic Search

Virosomal vaccines were prepared by extracting hemagglutinin (HA) and neuraminidase from influenza virus and incorporating it in the membranes of liposomes composed of phosphatidylcholine. Two intranasal spray vaccine series were prepared: one series comprised 7.5 mg of HA of each of three strains recommended by the World Health Organization and 1 m go fEscherichia coli heat-labile toxin (HLT), and the

ULRICH GLUCK; JAN-OLAF GEBBERS; REINHARD GLUCK

1999-01-01

8

Transcutaneous immunization with the heat-labile toxin (LT) of enterotoxigenic Escherichia coli (ETEC): Protective efficacy in a double-blind, placebo-controlled challenge study  

Microsoft Academic Search

BackgroundAn enterotoxigenic Escherichia coli (ETEC) vaccine could reduce diarrhea among children in developing countries and travelers to these countries. The heat-labile toxin (LT) of ETEC is immunogenic but too toxic for oral or nasal vaccines.

Robin McKenzie; A. Louis Bourgeois; Sarah A. Frech; David C. Flyer; Arlene Bloom; Kazem Kazempour; Gregory M. Glenn

2007-01-01

9

In vivo expression of the heat stable ( estA) and heat labile (e ltB) toxin genes of enterotoxigenic Escherichia coli (ETEC)  

Microsoft Academic Search

Enterotoxigenic Escherichia coli (ETEC) colonize the intestine and adhere to the epithelium by means of different host specific colonization factors (CFs). Colonizing ETEC produce one or both of two enterotoxins; the heat stable (ST) and heat labile (LT) toxins which are both able to cause diarrhoea. The regulation of virulence genes in ETEC during infection of the human intestine is

Åsa Sjöling; Firdausi Qadri; Matilda Nicklasson; Yasmin Ara Begum; Gudrun Wiklund; Ann-Mari Svennerholm

2006-01-01

10

Targeting of cholera toxin and Escherichia coli heat labile toxin in polarized epithelia: role of COOH-terminal KDEL  

Microsoft Academic Search

Vibrio cholerae and Escherichia coli heat la- bile toxins (CT and LT) elicit a secretory response from intestinal epithelia by binding apical receptors (ganglio- side GM1 ) and subsequently activating basolateral effec- tors (adenylate cyclase). We have recently proposed that signal transduction in polarized cells may require transcytosis of toxin-containing membranes (Lencer, W. I., G. Strohmeier, S. Moe, S. L.

W. I. Lencer; C. Constable; S. Moe; M. G. Jobling; H. M. Webb; S. Ruston; J. L. Madara; T. R. Hirst; R. K. Holmesll

1995-01-01

11

Interaction of cholera toxin and Escherichia coli heat-labile enterotoxin with glycoconjugates from rabbit intestinal brush border membranes: Relationship with ABH blood group determinants  

Microsoft Academic Search

The capacity of cholera toxin (CT) and type I heat-labile enterotoxin produced by Escherichia coli isolated from human intestine (LTh) to interact with glycoconjugates bearing ABH blood group determinants from rabbit intestinal brush border membranes (BBM) was studied. On the basis of the type of intestinal compounds related to the human ABH blood group antigens, rabbits were classified as AB

Luis E. Balanzino; José L. Barra; Estela M. Galváin; German A. Roth; Clara G. Monferran

1999-01-01

12

Immunogenicity of the B Monomer of Escherichia coli Heat-Labile Toxin Expressed on the Surface of Streptococcus gordonii  

PubMed Central

The B monomer of the Escherichia coli heat-labile toxin (LTB) was expressed on the surface of the human oral commensal bacterium Streptococcus gordonii. Recombinant bacteria expressing LTB were used to immunize BALB/c mice subcutaneously and intragastrically. The LTB monomer expressed on the streptococcal surface proved to be highly immunogenic, as LTB-specific immunoglobulin G (IgG) serum titers of 140,000 were induced after systemic immunization. Most significantly, these antibodies were capable of neutralizing the enterotoxin in a cell neutralization assay. Following mucosal delivery, antigen-specific IgA antibodies were found in feces and antigen-specific IgG antibodies were found in sera. Analysis of serum IgG subclasses showed a clear predominance of IgG1 when recombinant bacteria were inoculated subcutaneously, while a prevalence of IgG2a was observed upon intragastric delivery, suggesting, in this case, the recruitment of a Th1 type of immune response.

Ricci, Susanna; Medaglini, Donata; Rush, Catherine M.; Marcello, Alessandro; Peppoloni, Samuele; Manganelli, Riccardo; Palu, Giorgio; Pozzi, Gianni

2000-01-01

13

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

Microsoft Academic Search

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

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

2003-01-01

14

Characterization of heat-stable (STa) toxoids of enterotoxigenic Escherichia coli fused to double mutant heat-labile toxin peptide in inducing neutralizing Anti-STa antibodies.  

PubMed

A long-standing challenge in developing vaccines against enterotoxigenic Escherichia coli (ETEC), the most common bacteria causing diarrhea in children of developing countries and travelers to these countries, is to protect against heat-stable toxin type Ib (STa or hSTa). STa and heat-labile toxin (LT) are virulence determinants in ETEC diarrhea. LT antigens are often used in vaccine development, but STa has not been included because of its poor immunogenicity and potent toxicity. Toxic STa is not safe for vaccines, but only STa possessing toxicity is believed to be able to induce neutralizing antibodies. However, recent studies demonstrated that nontoxic STa derivatives (toxoids), after being fused to an LT protein, induced neutralizing antibodies and suggested that different STa toxoids fused to an LT protein might exhibit different STa antigenic propensity. In this study, we selected 14 STa toxoids from a mini-STa toxoid library based on toxicity reduction and reactivity to anti-native STa antibodies, and genetically fused each toxoid to a monomeric double mutant LT (dmLT) peptide for 14 STa-toxoid-dmLT toxoid fusions. These toxoid fusions were used to immunize mice and were characterized for induction of anti-STa antibody response. The results showed that different STa toxoids (in fusions) varied greatly in anti-STa antigenicity. Among them, STaN12S, STaN12T, and STaA14H were the top toxoids in inducing anti-STa antibodies. In vitro neutralization assays indicated that antibodies induced by the 3×STaN12S-dmLT fusion antigen exhibited the greatest neutralizing activity against STa toxin. These results suggested 3×STaN12S-dmLT is a preferred fusion antigen to induce an anti-STa antibody response and provided long-awaited information for effective ETEC vaccine development. PMID:24549325

Ruan, Xiaosai; Robertson, Donald C; Nataro, James P; Clements, John D; Zhang, Weiping

2014-05-01

15

Effect of Heat Stable and Heat Labile Escherichia coli Enterotoxins, Cholera Toxin and Theophylline on Unidirectional Sodium and Chloride Fluxes in the Proximal and Distal Jejunum of Weanling Swine  

PubMed Central

Acute, isolated loops of proximal and distal jejunum of weanling swine were exposed to either heat stable porcine Escherichia coli enterotoxin, heat labile porcine Escherichia coli enterotoxin, cholera toxin or theophylline. Unidirectional sodium fluxes in response to heat stable in the proximal jejunum were dependent on the length of time that the intestinal mucosae was exposed to the enterotoxin. Net water, sodium and chloride and unidirectional sodium and chloride flux measurements in the proximal jejunum in response to each agent uniformly indicated that net secretion of fluid and electrolytes was the result of increased unidirectional sodium secretion or blood-to-lumen flux and decreased unidirectional chloride absorption or lumen-to-blood flux. In addition heat stable cholera toxin and theophylline but not heat labile decreased unidirectional chloride secretion a small but significant amount in the proximal jejunum. Sodium and chloride flux measurements in the distal jejunum demonstrated that all four secretory agents could stimulate net secretion of water, sodium and chloride in that region. The response to these secretory agents as measured by sodium and chloride unidirectional flux rates was not similar to changes observed in the proximal jejunum. In the distal small intestine, whereas heat labile cholera toxin and theophylline induced similar qualitative changes in unidirectional sodium and chloride fluxes, that induced by heat stable differed.

Hamilton, D. L.; Roe, W. E.; Nielsen, N. O.

1977-01-01

16

HEAT LABILE OPSONINS TO PNEUMOCOCCUS  

PubMed Central

Heat labile opsonins (HLO) in normal rat serum to both encapsulated and unencapsulated pneumococci (a) have the same heat lability as complement (C); (b) are active at 37°C but not at 0°C; (c) are inactivated proportionately to hemolytic C by the addition of immune aggregates to the serum; (d) are adsorbed from serum nonspecifically by bacteria at 37°C but not at 0°C; (e) are Ca++- and/or Mg++-dependent in their action; and (f) are inactivated by zymosan and a purified cobra venom factor, and in the case of encapsulated pneumococci, at least, by NH4OH. Like other opsonins, HLO to pneumococci act primarily on the bacteria rather than on the phagocytes. Their combined properties indicate that they involve multiple components of the hemolytic C system. Since HLO are immunologically polyspecific, they presumably play a broad protective role in the early (preantibody) phase of acute bacterial infections.

Smith, Mary Ruth; Wood, W. Barry

1969-01-01

17

Ability of SPI2 mutant of S. typhi to effectively induce antibody responses to the mucosal antigen enterotoxigenic E. coli heat labile toxin B subunit after oral delivery to humans  

Microsoft Academic Search

We have evaluated an oral vaccine based on an Salmonella enteric serovar typhi (S. typhi) Ty2 derivative TSB7 harboring deletion mutations in ssaV (SPI-2) and aroC together with a chromosomally integrated copy of eltB encoding the B subunit of enterotoxigenic Escherichia coli heat labile toxin (LT-B) in volunteers. Two oral doses of 108 or 109CFU were administered to two groups

S. Khan; S. Chatfield; R. Stratford; J. Bedwell; M. Bentley; S. Sulsh; R. Giemza; S. Smith; E. Bongard; C. A. Cosgrove; J. Johnson; G. Dougan; G. E. Griffin; J. Makin; D. J. M. Lewis

2007-01-01

18

Non-recombinant display of the B subunit of the heat labile toxin of Escherichia coli on wild type and mutant spores of Bacillus subtilis  

PubMed Central

Background Mucosal infections are a major global health problem and it is generally accepted that mucosal vaccination strategies, able to block infection at their entry site, would be preferable with respect to other prevention approaches. However, there are still relatively few mucosal vaccines available, mainly because of the lack of efficient delivery systems and of mucosal adjuvants. Recombinant bacterial spores displaying a heterologous antigen have been shown to induce protective immune responses and, therefore, proposed as a mucosal delivery system. A non-recombinant approach has been recently developed and tested to display antigens and enzymes. Results We report that the binding subunit of the heat-labile toxin (LTB) of Escherichia coli efficiently adsorbed on the surface of Bacillus subtilis spores. When nasally administered to groups of mice, spore-adsorbed LTB was able to induce a specific immune response with the production of serum IgG, fecal sIgA and of IFN-? in spleen and mesenteric lymph nodes (MLN) of the immunized animals. Dot blotting experiments showed that the non-recombinant approach was more efficient than the recombinant system in displaying LTB and that the efficiency of display could be further increased by using mutant spores with an altered surface. In addition, immunofluorescence microscopy experiments showed that only when displayed on the spore surface by the non-recombinant approach LTB was found in its native, pentameric form. Conclusion Our results indicate that non-recombinant spores displaying LTB pentamers can be administered by the nasal route to induce a Th1-biased, specific immune response. Mutant spores with an altered coat are more efficient than wild type spores in adsorbing the antigen, allowing the use of a reduced number of spores in immunization procedures. Efficiency of display, ability to display the native form of the antigen and to induce a specific immune response propose this non-recombinant delivery system as a powerful mucosal vaccine delivery approach.

2013-01-01

19

A continuous epitope from transmissible gastroenteritis virus S protein fused to E. coli heat-labile toxin B subunit expressed by attenuated Salmonella induces serum and secretory immunity.  

PubMed

Antigenic site D from the spike protein of transmissible gastroenteritis virus (TGEV), which is a continuous epitope critical in neutralization, has been expressed as a fusion protein with E. coli heat-labile toxin B subunit (LT-B) in attenuated S. typhimurium. Synthetic peptides containing the sequence of site D induced TGEV neutralizing antibodies when inoculated subcutaneously in both rabbits and swine. A synthetic oligonucleotide encoding residues 373-398 of TGEV S protein, including antigenic site D, was cloned in frame with the 3' end of LT-B gene, into a plasmid used to transform S. typhimurium delta asd chi 3730. A collection of 6 recombinant plasmids designated pYALTB-D I-VI encoding LTB-site D fusions with a variable number of site D sequences were selected. Four of the 6 LTB-site D fusion products expressed in S. typhimurium chi 3730 formed oligomers (pentamers) that dissociated at > 70 degrees. S. typhimurium chi 3730 (pYALTB-D) V and VI expressed the oligomer forming products with higher antigenicity. Partially purified LTB-site D fusion product expressed from S. typhimurium chi 3730 (pYALTB-D) V induced anti-TGEV neutralizing antibodies in rabbits. Recombinant vaccine strain S. typhimurium delta cya delta crp delta asd chi 3987 transformed with plasmid pYALTB-D V expressed constitutively products that formed oligomers presumably containing 20 copies of site D, and showed a high stability in vitro. This recombinant strain was orally inoculated in rabbits and induced TGEV specific antibodies in both serum and intestinal secretion. PMID:8725098

Smerdou, C; Anton, I M; Plana, J; Curtiss, R; Enjuanes, L

1996-03-01

20

A Functional Antigen in a Practical Crop: LT-B Producing Maize Protects Mice against Escherichia coli Heat Labile Enterotoxin (LT) and Cholera Toxin (CT)  

Microsoft Academic Search

We have produced a functional heat labile enterotoxin (LT-) B subunit of Escherichia coli in maize. LT-B is a multimeric protein that presents an ideal model for an edible vaccine, displaying stability in the gut and inducing mucosal and systemic immune responses. Transgenic maize was engineered to synthesize the LT-B polypeptides, which assembled into oligomeric structures with affinity for GM1

Rachel Chikwamba; Joan Cunnick; Diane Hathaway; Jennifer McMurray; Hugh Mason; Kan Wang

2002-01-01

21

A functional antigen in a practical crop: LT-B producing maize protects mice against Escherichia coli heat labile enterotoxin (LT) and cholera toxin (CT)  

Microsoft Academic Search

We have produced a functional heat labile enterotoxin (LT-) B subunit of Escherichia coli in maize. LT-B is a multimeric protein that presents an ideal model for an edible vaccine, displaying stability in the gut and inducing mucosal and systemic immune responses. Transgenic maize was engineered to synthesize the LT-B polypeptides, which assembled into oligomeric structures with affinity for GM1

Rachel Chikwamba; Joan Cunnick; Diane Hathaway; Jennifer McMurray; Hugh Mason

2002-01-01

22

Ability of SPI2 mutant of S. typhi to effectively induce antibody responses to the mucosal antigen enterotoxigenic E. coli heat labile toxin B subunit after oral delivery to humans.  

PubMed

We have evaluated an oral vaccine based on an Salmonella enteric serovar typhi (S. typhi) Ty2 derivative TSB7 harboring deletion mutations in ssaV (SPI-2) and aroC together with a chromosomally integrated copy of eltB encoding the B subunit of enterotoxigenic Escherichia coli heat labile toxin (LT-B) in volunteers. Two oral doses of 10(8) or 10(9)CFU were administered to two groups of volunteers and both doses were well tolerated, with no vaccinemia, and only transient stool shedding. Immune responses to LT-B and S. typhi lipopolysaccharide were demonstrated in 67 and 97% of subjects, respectively, without evidence of anti-carrier immunity preventing boosting of LT-B responses in many cases. Further development of this salmonella-based (spi-VEC) system for oral delivery of heterologous antigens appears warranted. PMID:17412462

Khan, S; Chatfield, S; Stratford, R; Bedwell, J; Bentley, M; Sulsh, S; Giemza, R; Smith, S; Bongard, E; Cosgrove, C A; Johnson, J; Dougan, G; Griffin, G E; Makin, J; Lewis, D J M

2007-05-22

23

Safety and immunogenicity of bacterial and tobacco plant cell line derived recombinant native and mutant Escherichia coli heat-labile toxin in chickens.  

PubMed

The safety and immunogenicity of the mammalian mucosal adjuvants, Escherichia coli wild-type heat-labile holotoxin (LT) and E. coli mutant LT (LTA-K63/LTB), were examined in 1-day-old chicks and 10-day-old to 21-day-old broilers. Biologically active, E. coli recombinant wild-type LT and recombinant LTA-K63/LTB produced in a transgenic Nicotiana tabacum (NT-1) tobacco cell line (SLT102) were tested for safety and antigenicity following various routes of administration. Safety was assessed by clinical signs, body weight gain, gross organ pathology and wet organ weight, and histopathology. Antigenicity was assessed using LT-B-specific serum IgG enzyme-linked immunosorbent assay. Parenteral administration of E. coli recombinant wild-type LT did not have any discernible effect on bird health and was well tolerated at levels up to 400 µg per dose. Recombinant, SLT102-derived mutant LT derived from SLT102 cells retained in vitro ganglioside binding and was safe and antigenic following repeated mucosal administration to birds. The highest systemic LT-B-specific IgG titres were detected in birds that received three on-feed doses of SLT102-derived mutant LT. Among the various SLT102-derived mutant LT preparations tested, whole, wet cells or whole cell lysates were the most antigenic. These results demonstrate for the first time that E. coli-derived recombinant, wild-type LT holotoxin is well tolerated following multiple administrations to young birds at body weight doses previously reported to be enteropathogenic and toxic in mammalian species. Moreover, these data also demonstrate the feasibility of using recombinant wild-type and mutant LT produced in transgenic NT-1 tobacco cells as safe and potent vaccine adjuvants in poultry. PMID:22928883

Miller, Tim; Fanton, Matthew; Nickelson, Stephanie; Mason, Hugh; Webb, Steven

2012-10-01

24

Safety and Immunogenicity of a Single Oral Dose of Recombinant Double Mutant Heat-Labile Toxin Derived from Enterotoxigenic Escherichia coli  

PubMed Central

Enterotoxigenic Escherichia coli (ETEC) is a primary cause of traveler's diarrhea for which there is no licensed vaccine. This phase 1 trial determined the safety and immunogenicity of a recombinantly produced double mutant heat-labile enterotoxin (dmLT) of ETEC. It was administered as a single oral dose of dmLT in escalating doses of 5 ?g, 25 ?g, 50 ?g, and 100 ?g, followed by a 72-h inpatient observation, outpatient visits at 8, 14, and 28 days, and telephone calls at 2 and 6 months postvaccination. Safety was assessed by frequency of adverse events, and immune responses determined after immunization included dmLT-specific serum IgA and IgG, fecal IgA, antibody-secreting cells (ASC), and antibodies in lymphocyte supernatant (ALS) responses. All doses were well tolerated by the 36 healthy adults enrolled. Immune responses were limited in the 5- and 25-?g dose recipients. The 50-?g dose recipients trended toward stronger responses than the 100-?g dose recipients by serum IgA (67% versus 33%, P = 0.22), serum IgG (58% versus 33%, P = 0.41), and fecal IgA (58% versus 33%, P = 0.41). By day 14 postvaccination, there were significantly more positive responders (?4-fold increase from baseline) among the 50- versus 100-?g dose recipients for serum IgA (P = 0.036) but not serum IgG (P = 0.21). In conclusion, a single oral dose of dmLT was well tolerated and immunogenic, with immune responses plateauing at the 50-?g dose. (This clinical trial is registered at www.clinicaltrials.gov, registration number NCT01147445.)

El-Kamary, Samer S.; Cohen, Mitchell B.; Bourgeois, A. Louis; Van De Verg, Lillian; Bauers, Nicole; Reymann, Mardi; Pasetti, Marcela F.

2013-01-01

25

Bile and Unsaturated Fatty Acids Inhibit the Binding of Cholera Toxin and Escherichia coli Heat-Labile Enterotoxin to GM1 Receptor  

Microsoft Academic Search

Cholera toxin (CT) is an archetypal bacterial toxin that binds with a high affinity to the receptor ganglioside GM1 on the intestinal epithelial surface and that causes the severe watery diarrhea characteristic of the disease cholera. Blockage of the interaction of CT with the GM1 receptor is an attractive approach for therapeutic intervention. We report here that crude bile prevents

Arpita Chatterjee; Rukhsana Chowdhury

2008-01-01

26

Mutants of Escherichia coli Heat-Labile Toxin Act as Effective Mucosal Adjuvants for Nasal Delivery of an Acellular Pertussis Vaccine: Differential Effects of the Nontoxic AB Complex and Enzyme Activity on Th1 and Th2 Cells  

PubMed Central

Mucosal delivery of vaccines is dependent on the identification of safe and effective adjuvants that can enhance the immunogenicity of protein antigens administered by nasal or oral routes. In this study we demonstrate that two mutants of Escherichia coli heat-labile toxin (LT), LTK63, which lacks ADP-ribosylating activity, and LTR72, which has partial enzyme activity, act as potent mucosal adjuvants for the nasal delivery of an acellular pertussis (Pa) vaccine. Both LTK63 and LTR72 enhanced antigen-specific serum immunoglobulin G (IgG), secretory IgA, and local and systemic T-cell responses. Furthermore, using the murine respiratory challenge model for infection with Bordetella pertussis, we demonstrated that a nasally delivered diphtheria, tetanus, and acellular pertussis (DTPa) combination vaccine formulated with LTK63 as an adjuvant conferred a high level of protection, equivalent to that generated with a parenterally delivered DTPa vaccine formulated with alum. This study also provides significant new information on the roles of the binding and enzyme components of LT in the modulation of Th1 and Th2 responses. LTK63, which lacks enzyme activity, promoted T-cell responses with a mixed Th1–Th2 profile, but LTR72, which retains partial enzyme activity, and the wild-type toxin, especially at low dose, induced a more polarized Th2-type response and very high IgA and IgG antibody titers. Our findings suggest that the nontoxic AB complex has broad adjuvant activity for T-cell responses and that the ADP-ribosyltransferase activity of the A subunit also appears to modulate cytokine production, but its effect on T-cell subtypes, as well as enhancing, may be selectively suppressive.

Ryan, Elizabeth J.; McNeela, Edel; Murphy, Geraldine A.; Stewart, Helen; O'hagan, Derek; Pizza, Mariagrazia; Rappuoli, Rino; Mills, Kingston H. G.

1999-01-01

27

Structure and mucosal adjuvanticity of cholera and Escherichia coli heat-labile enterotoxins  

Microsoft Academic Search

Escherichia coli heat-labile enterotoxin and cholera toxin are potent mucosal immunogens and adjuvants in animal models. Non-toxic mutants retaining adjuvant activity are useful tools to dissect the mechanism of mucosal adjuvanticity and promising candidates for development of human vaccines and immunotherapy. Clinical trials are expected to proceed in the near future.

Rino Rappuoli; Mariagrazia Pizza; Gill Douce; Gordon Dougan

1999-01-01

28

Heat Stability and Species Range of Purified Staphylococcal ?-Toxin  

PubMed Central

Cooper, Louis Z. (New England Medical Center Hospital, Boston, Mass.), Morton A. Madoff, and Louis Weinstein. Heat stability and species range of purified staphylococcal ?-toxin. J. Bacteriol. 91:1686–1692. 1966.—Heating of high-titer purified staphylococcal ?-toxin at 60 and 80 C resulted in a double-sloped curve of inactivation of the hemolytic effect on rabbit erythrocytes. Early inactivation was less at the lower temperature, but activity persisted for a longer time at 80 C. Toxin inactivated at 60 C showed renewed activity when heated briefly at 80 C. A precipitate which formed during heating of ?-toxin at 60 or 80 C yielded hemolytic activity when resuspended and heated at 80 but not at 60 C. Supernatant fluid of heat-precipitated toxin was heat-labile and did not regain activity when heated at 80 C. The results indicate that the “paradoxical effect” of heating of staphylococcal ?-toxin is not due to a thermolabile inhibitor, but results from alteration of the toxin molecule to a heat-stable active form. Demonstration of renewed activity by 80 C heating of purified toxin requires potent toxin preparations and brief heating periods. Hemolysis of erythrocytes of several animal species by purified ?-toxin was generally similar to that produced by impure toxin. Rabbit cells were most susceptible. Human and horse erythrocytes hemolyzed to less than 0.1% of the extent of rabbit cells. Blood cells of other species were intermediate in their response to the lytic effect of ?-toxin.

Cooper, Louis Z.; Madoff, Morton A.; Weinstein, Louis

1966-01-01

29

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

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. PMID:23936344

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

30

Evaluation of the adjuvant effect of Salmonella-based Escherichia coli heat-labile toxin B subunits on the efficacy of a live Salmonella-delivered avian pathogenic Escherichia coli vaccine.  

PubMed

The present study evaluated the adjuvant effect of live attenuated salmonella organisms expressing the heat-labile toxin of Escherichia coli B subunit (LTB) on the efficacy of an avian pathogenic Escherichia coli (APEC) vaccine. The Asd(+) (aspartate semialdehyde dehydrogenase) plasmid pMMP906 containing the LTB gene was introduced into a Salmonella enterica Typhimurium strain lacking the lon, cpxR and asd genes to generate the adjuvant strain. Live recombinant Salmonella-delivered APEC vaccine candidates were used for this study. The birds were divided into three groups: group A, non-vaccinated controls; group B, immunized with vaccine candidates only; and group C, immunized with vaccine candidates and the LTB strain. The immune responses were measured and the birds were challenged at 21 days of age with a virulent APEC strain. Group C showed a significant increase in plasma IgG and intestinal IgA levels and a significantly higher lymphocyte proliferation response compared with the other groups. Upon challenge with the virulent APEC strain, group C showed effective protection whereas group B did not. We also attempted to optimize the effective dose of the adjuvant. The birds were immunized with the vaccine candidates together with 1×10? or 1×10? colony-forming units of the LTB strain and were subsequently challenged at 3 weeks of age. The 1×10? colony-forming units of the LTB strain showed a greater adjuvant effect with increased levels of serum IgG, intestinal IgA and a potent lymphocyte proliferation response, and yielded higher protection against challenge. Overall, the LTB strain increased the efficacy of the Salmonella -delivered APEC vaccine, indicating that vaccination for APEC along with the LTB strain appears to increase the efficacy for protection against colibacillosis in broiler chickens. PMID:23815619

Chaudhari, Atul A; Lee, John Hwa

2013-08-01

31

Escherichia coli Heat-Labile Enterotoxin: DNA-Directed in vitro Synthesis and Structure  

Microsoft Academic Search

Escherichia coli heat-labile enterotoxin was synthesized in a cell-free system directed by DNA of the plasmid P307. Synthesis of the toxin, assayed by the elongation induced in Chinese hamster ovary cells, was strongly stimulated by cyclic AMP and occurred at physiological levels of Mg2+ only when the polyamine spermidine was present. Activity was abolished by heat and antisera prepared against

F. Dorner; C. Hughes; G. Nahler; G. Hogenauer

1979-01-01

32

Toward the development of a stable, freeze-dried formulation of Helicobacter pylori killed whole cell vaccine adjuvanted with a novel mutant of E. coli heat-labile toxin  

PubMed Central

No vaccine exists for the prevention of infection with the ubiquitous gastric pathogen Helicobacter pylori, and drug therapy for the infection is complicated by poor patient compliance, the high cost of treatment, and ineffectiveness against drug resistant strains. A new medical advancement is required to reduce the incidence of peptic ulcer disease and stomach cancer, two conditions caused by infection with H. pylori. Clinical trials have been performed with a formalin-inactivated Helicobacter pylori Whole Cell (HWC) vaccine, given orally in combination with the mucosal adjuvant mLT(R192G), a mutant of E. coli heat-labile toxin. Following the initial dose of this vaccine, some subjects experienced gastrointestinal side effects. To reduce side effects and potentially further increase the amount of adjuvant that can safely be administered with the HWC vaccine, experiments were performed with a form of LT that carried two mutations in the A subunit, a substitution of G for R at position 192, and A for L at position 211. The double-mutant LT (dmLT) adjuvant stimulated immune responses as effectively as the single mutant LT in mice. Additionally, following a challenge infection, the dmLT-adjuvanted vaccine was as effective as single mutant LT in reducing gastric urease levels (diagnostic for H. pylori infection), and H. pylori colonization in the stomach as assessed by quantitative analysis of stomach homogenates. A lyophilized formulation of HWC was developed to improve stability and to potentially reduce reliance on cold chain maintenance. It was observed that a dmLT-adjuvanted lyophilized vaccine was equally as protective in the mouse model as the liquid formulation as assessed by gastric urease analysis and analysis of stomach homogenates for viable H. pylori. No readily detectable effect of tonicity or moisture content was observed for the lyophilized vaccine within the formulation limits evaluated. In an accelerated stability study performed at 37°C the lyophilized vaccine remained equally as protective as vaccine stored at 2–8°C. The formulation selected for clinical development consisted of 2.5×1010 formalin-inactivated cells per ml in 6.5% trehalose, 0.5% mannitol, and 10 mM citrate buffer at pH 6.8.

Summerton, Nancy A.; Welch, Richard W.; Bondoc, Laureano; Yang, Huei-Hsiung; Pleune, Brett; Ramachandran, Naryaswamy; Harris, Andrea M.; Bland, Desiree; Jackson, W. James; Park, Sukjoon; Clements, John D.; Nabors, Gary S.

2009-01-01

33

Protective Immunity and Antibody-Secreting Cell Responses Elicited by Combined Oral Attenuated Wa Human Rotavirus and Intranasal Wa 2/6-VLPs with Mutant Escherichia coli Heat-Labile Toxin in Gnotobiotic Pigs  

PubMed Central

Two combined rotavirus vaccination regimens were evaluated in a gnotobiotic pig model of rotavirus infection and disease and were compared to previously tested rotavirus vaccination regimens. The first (AttHRV/VLP2×) involved oral inoculation with one dose of attenuated (Att) Wa human rotavirus (HRV), followed by two intranasal (i.n.) doses of a rotavirus-like particle (2/6-VLPs) vaccine derived from Wa (VP6) and bovine RF (VP2) rotavirus strains. The 2/6-VLPs were coadministered with a mutant Escherichia coli heat-labile toxin, LT-R192G (mLT) adjuvant. For the second regimen (VLP2×/AttHRV), two i.n. doses of 2/6-VLPs+mLT were given, followed by one oral dose of attenuated Wa HRV. To compare the protective efficacy and immune responses induced by the combined vaccine regimens with individual rotavirus vaccine regimens, we included in the experiments the following vaccine groups: one oral dose of attenuated Wa HRV (AttHRV1× and Mock2×/AttHRV, respectively), three oral doses of attenuated Wa HRV (AttHRV3×), three i.n. doses of 2/6-VLPs plus mLT (VLP3×), three i.n. doses of purified double-layered inactivated Wa HRV plus mLT (InactHRV3×), mLT alone, and mock-inoculated pigs. The isotype, magnitude, and tissue distribution of antibody-secreting cells (ASCs) in the intestinal and systemic lymphoid tissues were evaluated using an enzyme-linked immunospot assay. The AttHRV/VLP2× regimen stimulated the highest mean numbers of intestinal immunoglobulin A (IgA) ASCs prechallenge among all vaccine groups. This regimen induced partial protection against virus shedding (58%) and diarrhea (44%) upon challenge of pigs with virulent Wa HRV. The reverse VLP2×/AttHRV regimen was less efficacious than the AttHRV/VLP2× regimen in inducing IgA ASC responses and protection against diarrhea (25% protection rate) but was more efficacious than VLP3× or InactHRV3× (no protection). In conclusion, the AttHRV/VLP2× vaccination regimen stimulated the strongest B-cell responses in the intestinal mucosal immune system at challenge and conferred a moderately high protection rate against rotavirus disease, indicating that priming of the mucosal inductive site at the portal of natural infection with a replicating vaccine, followed by boosting with a nonreplicating vaccine at a second mucosal inductive site, may be a highly effective approach to stimulate the mucosal immune system and induce protective immunity against various mucosal pathogens.

Yuan, Lijuan; Iosef, Cristiana; Azevedo, Marli S. P.; Kim, Yunjeong; Qian, Yuan; Geyer, Annelise; Nguyen, Trang Van; Chang, Kyeong-Ok; Saif, Linda J.

2001-01-01

34

Detection of heat-labile enterotoxin-like activity in stools of patients with cholera and Escherichia coli diarrhea.  

PubMed Central

The Y1 adrenal cell tissue culture assay was used to detect heat-labile enterotoxin-like activity in the stools of 14 of 74 patients with diarrhea. A positive effect of the stool on the adrenal cells was heat-labile and neutralized by cholera antitoxin. Enterotoxin-like activity was detected in the stools of 10 of 30 patients with cholera and in those of 2 of 4 from whom heat-labile Escherichia coli were isolated. None of the stools from nine individuals with Vibrio parahaemolyticus, Salmonella, or Shigella infections were positive. Two of 31 individuals from whom no pathogens were isolated had detectable toxin-like activity in their stools. The Y1 adrenal cell assay provides a rapid method of diagnosing heat-labile enterotoxigenic diarrhea and could be an adjunct in epidemiological studies of gastroenteritis.

Echeverria, P; Verheart, L; Ulyanco, C V; Santiago, L T

1978-01-01

35

Detection of heat-labile enterotoxin-like activity in stools of patients with cholera and Escherichia coli diarrhea.  

PubMed

The Y1 adrenal cell tissue culture assay was used to detect heat-labile enterotoxin-like activity in the stools of 14 of 74 patients with diarrhea. A positive effect of the stool on the adrenal cells was heat-labile and neutralized by cholera antitoxin. Enterotoxin-like activity was detected in the stools of 10 of 30 patients with cholera and in those of 2 of 4 from whom heat-labile Escherichia coli were isolated. None of the stools from nine individuals with Vibrio parahaemolyticus, Salmonella, or Shigella infections were positive. Two of 31 individuals from whom no pathogens were isolated had detectable toxin-like activity in their stools. The Y1 adrenal cell assay provides a rapid method of diagnosing heat-labile enterotoxigenic diarrhea and could be an adjunct in epidemiological studies of gastroenteritis. PMID:342414

Echeverria, P; Verheart, L; Ulyanco, C V; Santiago, L T

1978-01-01

36

Transcutaneous Immunization Using Colonization Factor and Heat-Labile Enterotoxin Induces Correlates of Protective Immunity for Enterotoxigenic Escherichia coli  

Microsoft Academic Search

Enterotoxigenic Escherichia coli (ETEC) diarrheal disease is a worldwide problem that may be addressed by transcutaneous delivery of a vaccine. In several human settings, protective immunity has been associated with immune responses to E. coli colonization factors and to the heat-labile toxin that induces the diarrhea. In this set of animal studies, transcutaneous immunization (TCI) using recombinant colonization factor CS6

Jianmei Yu; Frederick Cassels; Tanya Scharton-Kersten; Scott A. Hammond; Antoinette Hartman; Evelina Angov; Blaise Corthésy; Carl Alving; Gregory Glenn; Walter Reed Army

2002-01-01

37

In Vivo Expression and Immunoadjuvancy of a Mutant of Heat-Labile Enterotoxin of Escherichia coli in Vaccine and Vector Strains of Vibrio cholerae  

Microsoft Academic Search

Vibrio cholerae secretes cholera toxin (CT) and the closely related heat-labile enterotoxin (LT) of Escherichia coli, the latter when expressed in V. cholerae. Both toxins are also potent immunoadjuvants. Mutant LT molecules that retain immunoadjuvant properties while possessing markedly diminished enterotoxic activities when expressed by E. coli have been developed. One such mutant LT molecule has the substitution of a

EDWARD T. RYAN; THOMAS I. CREAN; MANOHAR JOHN; JOAN R. BUTTERTON; JOHN D. CLEMENTS; STEPHEN B. CALDERWOOD

38

Construction and immunogenicity evaluation of an epitope-based antigen against swine influenza A virus using Escherichia coli heat-labile toxin B subunit as a carrier-adjuvant.  

PubMed

Influenza A virus causes a highly contagious respiratory disease in a variety of avian and mammalian hosts, including humans and pigs. The primary means for preventing influenza epidemics is vaccination. Epitope-based vaccine represents a new approach to achieve protective immunity. The objective of this study was to construct and evaluate the immunogenicity of an epitope-based antigen for its potential application in future influenza vaccine development. The antigen, comprised of a set of consensus influenza A virus epitopes (IAVe), was genetically linked to a subunit of the bacterial heat-labile enterotoxin (LTB) as an adjuvant. Immunogenicity of this LTB-IAVe antigen was evaluated in a pig model. Despite an inability to detect neutralizing antibodies directed toward the whole virus, humoral immunity against the IAVe was demonstrated in both serum (IgA and IgG) and mucosal secretions (IgG) of immunized pigs. Specific cellular immunity was also induced after LTB-IAVe immunization, as evidenced by up-regulating of IL-1?, IL-8, and IL-4 expression in peripheral blood mononuclear cells (PBMCs) of vaccinated pigs. In comparison to the non-immunized pigs, pigs immunized with the LTB-IAVe showed improved protection against a pathogenic H1N1 swine influenza virus challenge, with about 50% decrease of pneumonic lesions and 10-fold reduction of the viral load in lung and nasal secretion at five days post challenge. This study establishes a platform for future construction of epitope-based vaccines against influenza A virus infection. PMID:23497910

Sun, Zhi; Lawson, Steven; Langenhorst, Robert; McCormick, Kara L; Brunick, Colin; Opriessnig, Tanja; Baker, Rodney; Yoon, Kyoung-Jin; Zhang, Weiping; Huber, Victor C; Fang, Ying

2013-06-28

39

Mucosal immunization of mice using CpG DNA and\\/or mutants of the heat-labile enterotoxin of Escherichia coli as adjuvants  

Microsoft Academic Search

Cholera toxin (CT) and the Escherichia coli heat-labile enterotoxin (LT) are potent mucosal adjuvants in animals associated, at least in part, with their ability to induce cAMP. While toxicity generally precludes their use in humans, a number of different subunit or genetically detoxified mutants of CT and LT have been developed. Another type of adjuvant that has been shown to

Michael J McCluskie; Risini D Weeratna; John D Clements; Heather L Davis

2001-01-01

40

Nutritional requirements for synthesis of heat-labile enterotoxin by enterotoxigenic strains of Escherichia coli.  

PubMed

Optimal growth conditions have been established for production of heat-labile enterotoxin (LT) by both porcine and human strains of enterotoxigenic (ENT(+)) Escherichia coli. There were no unusual growth factor requirements, and some strains produced fairly high levels of LT in a basal salts medium containing 0.5% glucose if the pH was carefully controlled. Several amino acids markedly stimulated LT synthesis when added to the basal salts-glucose medium. Methionine and lysine were the most stimulatory for both human and porcine strains. Either aspartic acid or glutamic acid further enhanced LT synthesis in the presence of methionine and lysine, with aspartic acid being more stimulatory for porcine strains and glutamic acid more stimulatory for human strains. There were no apparent vitamin requirements and no unusual cations needed for toxin synthesis except that Fe(3+) was slightly stimulatory for porcine strains. The stimulation by Fe(3+) was observed only in the presence of the three amino acids, suggesting that the effect was indirect rather than on toxin synthesis. The carbon source also influenced the yield of LT. Glucose supported maximal synthesis, but other carbon sources which exhibit a high degree of catabolite repression also supported high levels of synthesis. Little or no LT was released below pH 7.0; therefore, because the pH drops during growth from 7.5 to 6.8, even in highly buffered media, it was necessary to adjust the pH to 8.0 to effect complete release of cell-associated toxin. The defined medium containing three amino acids reduced the amount of UV-absorbing material in culture supernatants about fivefold and increased LT activity for various strains from two- to fivefold over a complex Casamino Acids-yeast extract medium. Conditions found to be optimal for synthesis of LT were inhibitory for the heat-stable enterotoxin. PMID:33900

Gilligan, P H; Robertson, D C

1979-01-01

41

Effect of fractions of Ethiopian And Norwegian colostrum on rotavirus and Escherichia coli heat-labile enterotoxin.  

PubMed Central

Samples of colostrum from both Ethiopian and Norwegian women contained antirotavirus activities of immunoglobulin and non-immunoglobulin nature. No significant differences in rotavirus immunoglobulin A or in rotavirus-inhibiting activity were found between samples from the two countries. The non-immunoglobulin inhibitory activity was trypsin sensitive and heat stable (100 degrees C for 10 min). Escherichia coli heat-labile enterotoxin antibodies were measured in the colostrum samples by enzyme-linked immunosorbent assay. No E. coli enterotoxin-specific immunoglobulin A was detected, possibly due to the high background caused by the nonspecific adsorption of immunoglobulin A to the enzyme-linked immunosorbent assay plates in the absence of toxin. A total of 5 of 15 Ethiopian colostrum samples and 0 of 11 Norwegian colostrum samples neutralized the effect of E. coli heat-labile enterotoxin on YI adrenal cells. Both the Ethiopian and the Norwegian colostrum samples contained a non-immunoglobulin enterotoxin-inhibitory activity when the toxin was measured by enzyme-linked immunosorbent assay. This inhibitory activity was not trypsin sensitive, and extraction by chloroform-methanol indicated that the inhibitor was of a lipid nature.

Otnaess, A B; Orstavik, I

1981-01-01

42

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  

Microsoft Academic Search

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 mg of rEtxB or above with 10 mg of HSV-1 glycoproteins elicited high serum and mucosal anti-HSV-1 titers comparable

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

2001-01-01

43

Attenuated Shigella flexneri 2a Vaccine Strain CVD 1204 Expressing Colonization Factor Antigen I and Mutant Heat-Labile Enterotoxin of Enterotoxigenic Escherichia coli  

Microsoft Academic Search

A multivalent live oral vaccine against both Shigella spp. and enterotoxigenic Escherichia coli (ETEC) is being developed based on the hypothesis that protection can be achieved if attenuated shigellae express ETEC fimbrial colonization factors and genetically detoxified heat-labile toxin from a human ETEC isolate (LTh). Two detoxified derivatives of LTh, LThK63 and LThR72, were engineered by substitution—serine to lysine at

HILARY KOPROWSKI; MYRON M. LEVINE; RICHARD J. ANDERSON; GENEVIEVE LOSONSKY; MARIAGRAZIA PIZZA; EILEEN M. BARRY

2000-01-01

44

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

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

45

Antibody against recombinant heat labile enterotoxin B subunit (rLTB) could block LT binding to ganglioside M1 receptor  

PubMed Central

Objectives Enterotoxigenic Escherichia coli (ETEC) is one of the most common agents of diarrhea among other bacterial agents. Designing and producing vaccine against these bacteria is one of the major purposes of World Health Organization (WHO). Due to presence of diverse clones of ETEC strains in the world, the use of global vaccines for ETEC infection is controversial. B subunit of heat labile toxin (LTB) was introduced as a vaccine candidate molecule by several investigators. The expression of LTB gene isolated from a local bacterial strain and investigation of its immunological property was the objective of this study. Materials and Methods LTB gene was isolated from a local isolated ETEC, cloned and expressed using pET28a expression vector. For LTB gene expression, the three main expression parameters (IPTG concentration, time and temperature of induction) were investigated. The recombinant protein was purified (>95%) with Ni-NTA column using 6XHis-tag and used as an antigen in ELISA test. Results The immunological analyses showed production of high titer of specific antibody in immunized mice. Anti LTB Antibody could bind to whole toxin and neutralize the toxin through inhibition of its binding to the Ganglioside M1 receptor. Conclusion The recombinant LTB protein is a highly immunogenic molecule. Considering the LTB role in ETEC pathogenesis, it can be taken into account as one of the most important components of vaccines against local ETEC.

Salimian, J; Salmanian, AH; Khalesi, R; Mohseni, M; Moazzeni, SM

2010-01-01

46

Comparison of heat-labile enterotoxins from porcine and human strains of Escherichia coli.  

PubMed Central

Heat-labile enterotoxins (LTs) from porcine EWD299) and human (H74-114) enterotoxigenic strains of Escherichia coli were isolated by a single-step galactose elution procedure. Although both strains had similar amounts of LT in their whole-cell lysates, H74-114 yielded a smaller quantity of purified LT than did EWD299. Immunodiffusion studies with specific antisera revealed that although the two LTs shared major antigenic determinants each also had unique antigens. Both also had shared and unique specificities in comparison with the cholera enterotoxin (choleragen). Differences also exist in the apparent molecular weights of their B-subunit oligomers (coligenoid) as well as in the B-subunit monomers. The monomer molecular weights are 11,500 for EWD299 porcine LT and 12,700 for H74-114 human LT. The results suggest that either this isolated human LT has a tetrameric coligenoid or it moves differently in sodium dodecyl sulfate gels for other reasons. The A-subunits of both LTs were similar in size (28,000 daltons), and both LTs were activated by mild proteolytic processing. Amino acid analysis showed a threefold increase in the level of tryptophan and two- and fourfold decreases in the levels of glutamic acid and methionine, respectively, in H74-114 LT compared with EWD299 LT. These structural and antigenic differences may prove to be significant in immunoprophylaxis of the cholera-coli family of enterotoxins. Further studies to define the extent of evolutionary drift of these toxins are needed. Images

Geary, S J; Marchlewicz, B A; Finkelstein, R A

1982-01-01

47

A heat-labile necrotic activity in supernatants from cultures of Legionella pneumophila.  

PubMed

Crude, concentrated extra-cellular supernatants from Legionella pneumophila produced a soft-tissue necrosis, demonstrated by intraperitoneal or sub-cutaneous injections into infant mice. The reaction was rapid and gave a hemorrhagic tissue necrosis within minutes. Being heat-labile, this tissue reaction is different from those of a heat-stable cytotoxin and a heat-stable hemolysin previously described. PMID:7080833

Berdal, B P; Olsvik, O; Ogaard, A A

1982-04-01

48

Type II Heat-Labile Enterotoxin-Producing 'Escherichia coli' Isolated from Animals and Humans,  

National Technical Information Service (NTIS)

Vibrio cholerae enterotoxin and a group of Escherichia coli heat-labile enterotoxins (LTs) are closely related in structure and mechanisms of action (8). LTs produced by strains of E. coli from humans (LT-H) and pigs (LT-P) have common and unique antigeni...

J. Seriwatana P. Echeverria D. N. Taylor L. Rasrinaul J. E. Brown

1988-01-01

49

Rapid test for identification of heat-labile enterotoxin-producing Escherichia coli colonies.  

PubMed Central

A latex particle agglutination test is described which is suitable for the recognition of heat-labile enterotoxin-producing colonies of Escherichia coli immediately after primary culture on a variety of commonly used enteric diagnostic media. The test is simple and economical to perform, and the results are available in minutes.

Finkelstein, R A; Yang, Z

1983-01-01

50

?-Hydroxylation and oxidation of lignoceric acid in brain: The role of heat-stable and heat-labile factors  

Microsoft Academic Search

Our previous investigations disclosed that the heat-stable and heat-labile factors obtained from brain cytosol are required for a-hydroxylation and oxidation of lignoceric acid by rat brain particulate fraction. The heat-stable factor was recently found to contain glucose-6-phosphate, N-acetylaspartate, glutamate, aspartate, glutamine, inorganic phosphate and low levels of adenosine nucleotide as active components. A combination of these compounds was as effective

Hiroshi Shimeno; Anupam Wali; Yasuo Kishimoto

1984-01-01

51

Antibodies to heat-labile Escherichia coli enterotoxin in Apaches in Whiteriver, Arizona.  

PubMed

Antitoxin titers to heat-labile Escherichia coli enterotoxin were measured in Apache children hospitalized with acute diarrhea and in Apaches of different age groups without diarrhea in Whiteriver, Ariz. The study suggests that in this locale, exposure to enterotocigenic E. coli is probably widespread and occurs early in life. Antitoxin titer rises after idarrheal disease associated with enterotocigenic E. coli infection, however, were not regulary found. PMID:1107221

Sack, R B; Hirschborn, N; Woodward, W E; Sack, D A; Cash, R A

1975-12-01

52

Amino acid sequence of heat-labile enterotoxin from chicken enterotoxigenic Escherichia coli is identical to that of human strain H 10407.  

PubMed

The DNA sequence of heat-labile enterotoxin from the chicken enterotoxigenic Escherichia coli 21d strain was determined by direct dideoxy sequencing of polymerase chain reaction (PCR)-amplified DNA and was compared with those of heat-labile enterotoxins from porcine and human enterotoxigenic E. coli strains EWD 299 and H 10407. The structural genes of the A and B subunits of chicken heat-labile enterotoxin were identical to those of human heat-labile enterotoxin from the human H 10407 strain. Moreover, 67 base pairs of the upstream and 60 base pairs of the downstream region of the chicken heat-labile enterotoxin gene were also identical to that of the human heat-labile enterotoxin from strain H 10407. However, the patterns of plasmids from the 21d and H 10407 strains were different. The 21d strain had no band corresponding to the 42-MDa plasmid of the H 10407 strain encoding the heat-labile enterotoxin gene but it had a smaller plasmid. These data suggest that although the DNA sequence of chicken heat-labile enterotoxin is identical to that of human heat-labile enterotoxin, the plasmid encoding the chicken heat-labile enterotoxin gene in the chicken might be different from that encoding the human heat-labile enterotoxin gene in the H 10407 strain. PMID:8486242

Inoue, T; Tsuji, T; Koto, M; Imamura, S; Miyama, A

1993-04-01

53

Type II Heat-labile Enterotoxins: Structure, Function, and Immunomofdulatory Properties  

PubMed Central

The heat-labile enterotoxins (HLTs) of Escherichia coli and Vibrio cholerae are classified into two major types on the basis of genetic, biochemical, and immunological properties. Type I and Type II HLT have been intensively studied for their exceptionally strong adjuvant activities. Despite general structural similarities, these molecules, in intact or derivative (non-toxic) forms, display notable differences in their mode of immunomodulatory action. The molecular basis of these differences has remained largely uncharacterized until recently. This review focuses on the Type II HLTs and their immunomodulatory properties which depend largely on interactions with unique gangliosides and Toll-like receptors that are not utilized by the Type I HLTs.

Hajishengallis, George; Connell, Terry D.

2012-01-01

54

Importance of Heat-Labile Enterotoxin in Colonization of the Adult Mouse Small Intestine by Human Enterotoxigenic Escherichia coli Strains  

PubMed Central

Enterotoxigenic Escherichia coli (ETEC) infections are a significant cause of diarrheal disease and infant mortality in developing countries. Studies of ETEC pathogenesis relevant to vaccine development have been greatly hampered by the lack of a suitable small-animal model of infection with human ETEC strains. Here, we demonstrate that adult immunocompetent outbred mice can be effectively colonized with the prototypical human ETEC H10407 strain (colonization factor antigen I; heat-labile and heat-stable enterotoxin positive) and that production of heat-labile holotoxin provides a significant advantage in colonization of the small intestine in this model.

Allen, Kenneth P.; Randolph, Mildred M.; Fleckenstein, James M.

2006-01-01

55

A two-year survey of the incidence of heat-labile enterotoxin-producing Escherichia coli and other enteric pathogens in travellers returning to the Sheffield area.  

PubMed Central

A case-controlled study of the incidence of heat-labile enterotoxin-producing Escherichia coli (LT+ETEC) and other enteric pathogens in travellers returning to the Sheffield area was conducted from May 1984 to April 1986. LT+ETEC were found in 35 (5.8%) of 600 travellers to developed countries (mainly popular Mediterranean holiday resorts), 36 (11.3%) of 320 travellers to less-developed countries, and 11 (0.9%) of 1282 control patients whose illness was not associated with recent travel abroad. A seasonal peak of LT+ETEC infection was observed only in travellers to developed countries, with infections being significantly commoner in August to October. There was no significant deviation from expected age/sex distribution of LT+ETEC infection. Strains of LT+ETEC from travellers produced more toxin than strains from control patients, strains from travellers to less-developed countries producing most of all.

Chapman, P. A.; Mitchelmore, D. L.

1988-01-01

56

Molecular mechanism for the effects of E. coli heat-labile enterotoxin on mouse embryo survival.  

PubMed

Heat-labile enterotoxin (LT) can cause animal enteritis and diarrhea. However, the possible association of LT with embryo survival in pregnant animals and the mechanisms involved remain unknown. To investigate the effects of LT on embryo survival, we treated mouse early embryos in vitro and pregnant mice in vivo with recombinant LT. LT significantly decreased mouse embryo survival, and induced IFN-?, IL-2 and IL-1? production in the serum and placental tissue. LT also triggered IL-1? release from LPS-primed microphages, suggesting LT can activate inflammasomes. To determine the pathway involved in LT-induced inflammasome activation, small interfering RNAs were used to knockdown NLRP3 and ASC, the key components of NLRP3 inflammasome pathway. Ablation of NLRP3 and ASC abolished LT-induced IL-1? release, confirming the involvement of NLRP3 inflammasome. By comparing two subunits of LT, only LTA but not LTB subunit was identified to activate the NLRP3 inflammasome. PMID:24440567

Li, Wenyan; Han, Dongmei; Liang, Shuang; Zhong, Zhenyu; Li, Xiujin; Wen, Jiexia; Lin, Hongyu; Wang, Liyue; Li, Xiangyun; Zhong, Xiuhui; Zhong, Fei

2014-06-01

57

Efficacy of the Heat-Labile Enterotoxin from Escherichia Coli as an Adjuvant for a HSV-2 Inactivated Oral Vaccine.  

National Technical Information Service (NTIS)

This project examined the efficacy of the heat-labile enterotoxin from Escherichia coli (LT) as an adjuvant for an inactivated HSV-2 vaccine. Using 5-week-old BAB/c mice, three oral doses of inactivated HSV-2/LT (25 ug/25 ug) vaccine given at weekly inter...

A. J. Pinto

1996-01-01

58

An outbreak of gastroenteritis due to a heat-labile enterotoxin-producing strain of Escherichia coli.  

PubMed Central

In April 1981, an outbreak of gastroenteritis, characterized by diarrhea and abdominal cramps, occurred in 282 of approximately 3,000 personnel at a large metropolitan hospital in San Antonio, Tex. There was a significant association between illness and eating at the hospital cafeteria (P = 0.0008), but no specific food could be incriminated. Stools or rectal swabs from 54 ill individuals produced almost pure cultures of Escherichia coli. Cultures from 51 of these subjects had identical antibiotic sensitivity patterns, and 38 had the same biotype. Isolates from 45 persons were tested for production of heat-stable and heat-labile enterotoxins, using the suckling mouse and Y-1 adrenal cell assays, respectively. Of 45 isolates, 41 produced heat-labile enterotoxins, while 0 of 45 produced heat-stabile enterotoxins. Two isolates were rough, and 34 of the remaining 43 were serotype O25:H-. Two strains were O25:H+. None of the 45 strains possessed hemagglutination patterns typical of colonization factor antigens I or II. Six of seven O25:H- heat-labile enterotoxin-positive strains selected at random were piliated as seen by electron microscopy but did not agglutinate with anti-colonization factor antigens I or II antisera.

Wood, L V; Wolfe, W H; Ruiz-Palacios, G; Foshee, W S; Corman, L I; McCleskey, F; Wright, J A; DuPont, H L

1983-01-01

59

Type II heat-labile enterotoxin-producing Escherichia coli isolated from animals and humans.  

PubMed Central

Heat-labile enterotoxin (LT)-producing Escherichia coli strains, as identified by the Y1 adrenal cell assay, were examined with a DNA probe coding for type I and type II LTs. Of 236 LT-producing E. coli isolates, 60% hybridized with LT-I, 17% hybridized with LT-II, and 23% did not hybridize with either probe and no longer produced LT as determined by the Y1 adrenal cell assay. These isolates presumably lost plasmids coding for LT-I during storage. A total of 75% of LT-producing E. coli isolates (27 of 36) from cows, 64% of LT-producing E. coli isolates (7 of 11) from buffalo, 31% of LT-producing E. coli isolates (4 of 13) from beef obtained in markets, and 2% of LT-producing E. coli isolates (3 of 168) from humans contained genes coding for LT-II. Genes coding for LT-II were not found in 50 LT-I-producing and heat-stable enterotoxin-producing E. coli isolates from 11 children with diarrhea and 44 LT-nonproducing and heat-stable enterotoxin-producing E. coli isolates from 12 other children with diarrhea. A total of 9% of LT-II-producing E. coli isolates (3 of 34) from cows and buffalo hybridized with DNA probes for genes coding for verocytotoxin 2 (VT2), and 18% (6 of 34) hybridized with a DNA probe coding for enterohemorrhagic E. coli (EHEC) adhesin fimbriae. E. coli SA-53, the original isolate in which LT-II was found, contained genes coding for VT2 and EHEC adhesin fimbriae. Five VT-producing, LT-II-producing E. coli isolates that hybridized with the EHEC probe did not contain DNA sequences coding for VT1 or VT2. LT-II-producing E. coli strains were frequently isolated from cattle and buffalo but were rarely isolated from humans.

Seriwatana, J; Echeverria, P; Taylor, D N; Rasrinaul, L; Brown, J E; Peiris, J S; Clayton, C L

1988-01-01

60

Heat labile enterotoxin of E. coli: a potential adjuvant for transcutaneous cancer immunotherapy.  

PubMed

Escherichia coli heat labile enterotoxin (LT) has been shown to penetrate intact skin and to activate adaptive immunity. A nontoxic mutant, nLT, and its B subunit (LTB), have been evaluated separately for their potential use as a tool for transcutaneous delivery of antigens for cancer immunotherapy. We have shown that FITC-labeled nLT is taken up by human dendritic cells (hDC) in vitro and in mouse skin, and induces maturation and activation of hDC in vitro. hDC matured with nLT enhanced nonspecific melanoma antigen uptake and presentation to autologous CD8+ T cells. In mouse in vivo studies, nLT or LTB were applied on the skin either mixed with recombinant gp100 or genetically fused with a multiepitope polypeptide (MEP). Fused LTB-MEP induced antibody production that was dependent on LTB cell binding. We conclude that LT derivatives may be useful for the transcutaneous delivery of tumor antigens for cancer immunotherapy. PMID:16157421

Pitcovski, J; Bazak, Z; Wasserman, Elena; Elias, Orit; Levy, Adva; Peretz, Tamar; Fingerut, Elena; Frankenburg, Shoshana

2006-01-30

61

Transcutaneous immunization with heat-labile enterotoxin: development of a needle-free vaccine patch.  

PubMed

The skin is an attractive target for vaccine delivery. Adjuvants and antigens delivered into the skin can result in potent immune responses and an unmatched safety profile. The heat-labile enterotoxin (LT) from Escherichia coli, which acts both as antigen and adjuvant, has been shown to be delivered to human skin efficiently when used in a patch, resulting in strong immune responses. Iomai scientists have capitalized on these observations to develop late-stage products based on LT. This has encouraged commercial-level product development of a delivery system that is efficient, user-friendly and designed to address important medical needs. Over the past 2 years, extensive clinical testing and optimization has allowed the patch to evolve to a late-stage product. As a strategy for approval of a revolutionary vaccine-delivery system, the singular focus on optimization of LT delivery has enabled technical progress to extend patch-vaccine product development beyond LT. The field efficacy of the LT-based travelers' diarrhea vaccine has validated this approach. The discussion of transcutaneous immunization is unique, in that any consideration of the adjuvant must also include delivery, and the significant advances in a commercial patch application system are described. In this review, we integrate these concepts, update the clinical data and look to the future. PMID:17931160

Glenn, Gregory M; Flyer, David C; Ellingsworth, Larry R; Frech, Sarah A; Frerichs, David M; Seid, Robert C; Yu, Jianmei

2007-10-01

62

Role of GM1 binding in the mucosal immunogenicity and adjuvant activity of the Escherichia coli heat-labile enterotoxin and its B subunit.  

PubMed Central

Escherichia coli (E. coli) heat-labile toxin (LT) is a potent mucosal immunogen and immunoadjuvant towards co-administered antigens. LT is composed of one copy of the A subunit, which has ADP-ribosylation activity, and a homopentamer of B subunits, which has affinity for the toxin receptor, the ganglioside GM1. Both the ADP-ribosylation activity of LTA and GM1 binding of LTB have been proposed to be involved in immune stimulation. We investigated the roles of these activities in the immunogenicity of recombinant LT or LTB upon intranasal immunization of mice using LT/LTB mutants, lacking either ADP-ribosylation activity, GM1-binding affinity, or both. Likewise, the adjuvant properties of these LT/LTB variants towards influenza virus subunit antigen were investigated. With respect to the immunogenicity of LT and LTB, we found that GM1-binding activity is essential for effective induction of anti-LTB antibodies. On the other hand, an LT mutant lacking ADP-ribosylation activity retained the immunogenic properties of the native toxin, indicating that ADP ribosylation is not critically involved. Whereas adjuvanticity of LTB was found to be directly related to GM1-binding activity, adjuvanticity of LT was found to be independent of GM1-binding affinity. Moreover, a mutant lacking both GM1-binding and ADP-ribosylation activity, also retained adjuvanticity. These results demonstrate that neither ADP-ribosylation activity nor GM1 binding are essential for adjuvanticity of LT, and suggest an ADP-ribosylation-independent adjuvant effect of the A subunit. Images Figure 1

de Haan, L; Verweij, W R; Feil, I K; Holtrop, M; Hol, W G; Agsteribbe, E; Wilschut, J

1998-01-01

63

Mucosal immunogenicity and adjuvant activity of the recombinant A subunit of the Escherichia coli heat-labile enterotoxin  

PubMed Central

The Escherichia coli heat-labile enterotoxin (LT) is an exceptionally effective mucosal immunogen and mucosal immunoadjuvant towards coadministered antigens. Although, in general, the molecular basis of these properties is poorly understood, both the toxic ADP-ribosylation activity of the LTA subunit and the cellular toxin receptor, ganglioside, GM1-binding properties of the LTB-pentamer have been suggested to be involved. In recent studies we found that GM1-binding is not essential for the adjuvanticity of LT, suggesting an important role for the LTA subunit in immune stimulation. We now describe the immunomodulatory properties of recombinant LTA molecules with or without ADP-ribosylation activity, LTA(His)10 and LTA-E112K(His)10, respectively. These molecules were expressed as fusion proteins with an N-terminal His-tag to allow simple purification on nickel-chelate columns. Their immunogenic and immunoadjuvant properties were assessed upon intranasal administration to mice, and antigen-specific serum immunoglobulin-isotype and -subtype responses and mucosal secretory immunoglobulin A (IgA) responses were monitored using enzyme-linked immunosorbent assay. With respect to immunogenicity, both LTA(His)10 and LTA-E112K(His)10 failed to induce antibody responses. On the other hand, immunization with both LT and the non-toxic LT-E112K mutant not only induced brisk LTB-specific, but also LTA-specific serum and mucosal antibody responses. Therefore, we conclude that linkage of LTA to the LTB pentamer is essential for the induction of LTA-specific responses. With respect to adjuvanticity, both LTA(His)10 and LTA-E112K(His)10 were found to stimulate serum and mucosal antibody responses towards coadministered influenza subunit antigen. Remarkably, responses obtained with LTA(His)10 were comparable in both magnitude and serum immunoglobulin isotype and subtype distributions to those observed after coimmunization with LT, LT-E112K, or recombinant LTB. We conclude that LTA, by itself, can act as a potent adjuvant for intranasally administered antigens in a fashion independent of ADP-ribosylation activity and association with the LTB pentamer.

De Haan, L; Holtrop, M; Verweij, W R; Agsteribbe, E; Wilschut, J

1999-01-01

64

Methyl methanesulfonate (MMS) produces heat-labile DNA damage but no detectable in vivo DNA double-strand breaks  

PubMed Central

Homologous recombination (HR) deficient cells are sensitive to methyl methanesulfonate (MMS). HR is usually involved in the repair of DNA double-strand breaks (DSBs) in Saccharomyces cerevisiae implying that MMS somehow induces DSBs in vivo. Indeed there is evidence, based on pulsed-field gel electrophoresis (PFGE), that MMS causes DNA fragmentation. However, the mechanism through which MMS induces DSBs has not been demonstrated. Here, we show that DNA fragmentation following MMS treatment, and detected by PFGE is not the consequence of production of cellular DSBs. Instead, DSBs seen following MMS treatment are produced during sample preparation where heat-labile methylated DNA is converted into DSBs. Furthermore, we show that the repair of MMS-induced heat-labile damage requires the base excision repair protein XRCC1, and is independent of HR in both S.cerevisiae and mammalian cells. We speculate that the reason for recombination-deficient cells being sensitive to MMS is due to the role of HR in repair of MMS-induced stalled replication forks, rather than for repair of cellular DSBs or heat-labile damage.

Lundin, Cecilia; North, Matthew; Erixon, Klaus; Walters, Kevin; Jenssen, Dag; Goldman, Alastair S. H.; Helleday, Thomas

2005-01-01

65

ON THE NATURE OF THE HEAT-LABILE SUBSTANCE ("V") REQUIRED FOR THE GROWTH OF THE BACILLUS OF PFEIFFER  

PubMed Central

It has been shown in several experiments that the heat-labile, growth-promoting factor "V" found in the blood of animals does not diminish or disappear when the animals are kept on vitamine B-free diet. The titer of the "V" substance present in the blood of normal animals is undiminished in animals showing severe signs of polyneuritis even to the time of their death. The antipolyneuritic factor of vegetable food, designated as vitamine B, is found to be considerably more heat-stable than is the "V" substance concerned in promoting the growth of Pfeiffer's bacillus.

Thjotta, Th.

1924-01-01

66

ON THE NATURE OF THE HEAT-LABILE SUBSTANCE ("V") REQUIRED FOR THE GROWTH OF THE BACILLUS OF PFEIFFER.  

PubMed

It has been shown in several experiments that the heat-labile, growth-promoting factor "V" found in the blood of animals does not diminish or disappear when the animals are kept on vitamine B-free diet. The titer of the "V" substance present in the blood of normal animals is undiminished in animals showing severe signs of polyneuritis even to the time of their death. The antipolyneuritic factor of vegetable food, designated as vitamine B, is found to be considerably more heat-stable than is the "V" substance concerned in promoting the growth of Pfeiffer's bacillus. PMID:19868950

Thjötta, T

1924-10-31

67

Establishment of a heat inactivation curve for Clostridium botulinum 62A toxin in beef broth.  

PubMed Central

A procedure is described for establishing a heat inactivation curve for the toxin of Clostridium botulinum 62A in beef broth. The effect of toxin titer, pH, and the type of acid employed for pH adjustment on the heat stability of the toxin is described.

Losikoff, M E

1978-01-01

68

Marine neurotoxins: Envenomations and contact toxins  

Microsoft Academic Search

Opinion statement  Familiarity with the appearance and habitat of venomous sea creatures, the location of their stinging apparatus, and surveillance\\u000a of population concentrations within recreational waters are essential in avoiding envenomations. Compared with the thermo-stable\\u000a low molecular weighted ingestible seafood toxins, venomous toxins are often large molecular weight proteins and many are heat\\u000a labile, which provides opportunity for therapeutic intervention. Heat

Michael R. Watters; Elijah W. Stommel

2004-01-01

69

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

PubMed

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. PMID:1902492

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

1991-05-01

70

Ginger and its bioactive component inhibit enterotoxigenic Escherichia coli heat-labile enterotoxin-induced diarrhea in mice.  

PubMed

Ginger is one of the most commonly used fresh herbs and spices. Enterotoxigenic Escherichia coli heat-labile enterotoxin (LT)-induced diarrhea is the leading cause of infant death in developing countries. In this study, we demonstrated that ginger significantly blocked the binding of LT to cell-surface receptor G M1, resulting in the inhibition of fluid accumulation in the closed ileal loops of mice. Biological-activity-guided searching for active components showed that zingerone (vanillylacetone) was the likely active constituent responsible for the antidiarrheal efficacy of ginger. Further analysis of chemically synthesized zingerone derivatives revealed that compound 31 (2-[(4-methoxybenzyl)oxy]benzoic acid) significantly suppressed LT-induced diarrhea in mice via an excellent surface complementarity with the B subunits of LT. In conclusion, our findings provide evidence that ginger and its derivatives may be effective herbal supplements for the clinical treatment of enterotoxigenic Escherichia coli diarrhea. PMID:17880155

Chen, Jaw-Chyun; Huang, Li-Jiau; Wu, Shih-Lu; Kuo, Sheng-Chu; Ho, Tin-Yun; Hsiang, Chien-Yun

2007-10-17

71

LT-IIc, a new member of the type II heat-labile enterotoxin family encoded by an Escherichia coli strain obtained from a nonmammalian host.  

PubMed

Two families of bacterial heat-labile enterotoxins (HLTs) have been described: the type I HLTs are comprised of cholera toxin (CT) of Vibrio cholerae, LT-I of Escherichia coli, and several related HLTs; the type II HLTs are comprised of LT-IIa and LT-IIb. Herein, we report LT-IIc, a new type II HLT encoded from an enterotoxigenic E. coli (ETEC) strain isolated from an avian host. Using a mouse Y1 adrenal cell bioassay, LT-IIc was shown to be less cytotoxic than CT, LT-IIa, or LT-IIb. Cytotoxicity of LT-IIc was partially neutralized by antisera recognizing LT-IIa or LT-IIb but not by anti-CT antiserum. Genes encoding putative A polypeptide and B polypeptides of LT-IIc were arranged in an operon which was flanked by potential prophage sequences. Analysis of the nucleotide and predicted amino acid sequences demonstrated that the A polypeptide of LT-IIc has moderate homology to the A polypeptides of CT and LT-I and high homology to the A polypeptides of LT-IIa and LT-IIb. The B polypeptide of LT-IIc exhibited no significant homology to the B polypeptides of CT and LT-I and only moderate homology to the B polypeptides of LT-IIa and LT-IIb. The binding pattern of LT-IIc for gangliosides was distinctive from that of either LT-IIa or LT-IIb. The data suggest that other types of the type II HLT subfamily are circulating in the environment and that host specificity of type II HLT is likely governed by changes in the B polypeptide which mediate binding to receptors. PMID:20713622

Nawar, Hesham F; King-Lyons, Natalie D; Hu, John C; Pasek, Raymond C; Connell, Terry D

2010-11-01

72

LT-IIc, a New Member of the Type II Heat-Labile Enterotoxin Family Encoded by an Escherichia coli Strain Obtained from a Nonmammalian Host ?  

PubMed Central

Two families of bacterial heat-labile enterotoxins (HLTs) have been described: the type I HLTs are comprised of cholera toxin (CT) of Vibrio cholerae, LT-I of Escherichia coli, and several related HLTs; the type II HLTs are comprised of LT-IIa and LT-IIb. Herein, we report LT-IIc, a new type II HLT encoded from an enterotoxigenic E. coli (ETEC) strain isolated from an avian host. Using a mouse Y1 adrenal cell bioassay, LT-IIc was shown to be less cytotoxic than CT, LT-IIa, or LT-IIb. Cytotoxicity of LT-IIc was partially neutralized by antisera recognizing LT-IIa or LT-IIb but not by anti-CT antiserum. Genes encoding putative A polypeptide and B polypeptides of LT-IIc were arranged in an operon which was flanked by potential prophage sequences. Analysis of the nucleotide and predicted amino acid sequences demonstrated that the A polypeptide of LT-IIc has moderate homology to the A polypeptides of CT and LT-I and high homology to the A polypeptides of LT-IIa and LT-IIb. The B polypeptide of LT-IIc exhibited no significant homology to the B polypeptides of CT and LT-I and only moderate homology to the B polypeptides of LT-IIa and LT-IIb. The binding pattern of LT-IIc for gangliosides was distinctive from that of either LT-IIa or LT-IIb. The data suggest that other types of the type II HLT subfamily are circulating in the environment and that host specificity of type II HLT is likely governed by changes in the B polypeptide which mediate binding to receptors.

Nawar, Hesham F.; King-Lyons, Natalie D.; Hu, John C.; Pasek, Raymond C.; Connell, Terry D.

2010-01-01

73

In Vivo Expression and Immunoadjuvancy of a Mutant of Heat-Labile Enterotoxin of Escherichia coli in Vaccine and Vector Strains of Vibrio cholerae  

PubMed Central

Vibrio cholerae secretes cholera toxin (CT) and the closely related heat-labile enterotoxin (LT) of Escherichia coli, the latter when expressed in V. cholerae. Both toxins are also potent immunoadjuvants. Mutant LT molecules that retain immunoadjuvant properties while possessing markedly diminished enterotoxic activities when expressed by E. coli have been developed. One such mutant LT molecule has the substitution of a glycine residue for arginine-192 [LT(R192G)]. Live attenuated strains of V. cholerae that have been used both as V. cholerae vaccines and as vectors for inducing mucosal and systemic immune responses directed against expressed heterologous antigens have been developed. In order to ascertain whether LT(R192G) can act as an immunoadjuvant when expressed in vivo by V. cholerae, we introduced a plasmid (pCS95) expressing this molecule into three vaccine strains of V. cholerae, Peru2, ETR3, and JRB14; the latter two strains contain genes encoding different heterologous antigens in the chromosome of the vaccine vectors. We found that LT(R192G) was expressed from pCS95 in vitro by both E. coli and V. cholerae strains but that LT(R192G) was detectable in the supernatant fraction of V. cholerae cultures only. In order to assess potential immunoadjuvanticity, groups of germfree mice were inoculated with the three V. cholerae vaccine strains alone and compared to groups inoculated with the V. cholerae vaccine strains supplemented with purified CT as an oral immunoadjuvant or V. cholerae vaccine strains expressing LT(R192G) from pCS95. We found that mice continued to pass stool containing V. cholerae strains with pCS95 for at least 4 days after oral inoculation, the last day evaluated. We found that inoculation with V. cholerae vaccine strains containing pCS95 resulted in anti-LT(R192G) immune responses, confirming in vivo expression. We were unable to detect immune responses directed against the heterologous antigens expressed at low levels in any group of animals, including animals that received purified CT as an immunoadjuvant. We were, however, able to measure increased vibriocidal immune responses against vaccine strains in animals that received V. cholerae vaccine strains expressing LT(R192G) from pCS95 compared to the responses in animals that received V. cholerae vaccine strains alone. These results demonstrate that mutant LT molecules can be expressed in vivo by attenuated vaccine strains of V. cholerae and that such expression can result in an immunoadjuvant effect.

Ryan, Edward T.; Crean, Thomas I.; John, Manohar; Butterton, Joan R.; Clements, John D.; Calderwood, Stephen B.

1999-01-01

74

In vivo expression and immunoadjuvancy of a mutant of heat-labile enterotoxin of Escherichia coli in vaccine and vector strains of Vibrio cholerae.  

PubMed

Vibrio cholerae secretes cholera toxin (CT) and the closely related heat-labile enterotoxin (LT) of Escherichia coli, the latter when expressed in V. cholerae. Both toxins are also potent immunoadjuvants. Mutant LT molecules that retain immunoadjuvant properties while possessing markedly diminished enterotoxic activities when expressed by E. coli have been developed. One such mutant LT molecule has the substitution of a glycine residue for arginine-192 [LT(R192G)]. Live attenuated strains of V. cholerae that have been used both as V. cholerae vaccines and as vectors for inducing mucosal and systemic immune responses directed against expressed heterologous antigens have been developed. In order to ascertain whether LT(R192G) can act as an immunoadjuvant when expressed in vivo by V. cholerae, we introduced a plasmid (pCS95) expressing this molecule into three vaccine strains of V. cholerae, Peru2, ETR3, and JRB14; the latter two strains contain genes encoding different heterologous antigens in the chromosome of the vaccine vectors. We found that LT(R192G) was expressed from pCS95 in vitro by both E. coli and V. cholerae strains but that LT(R192G) was detectable in the supernatant fraction of V. cholerae cultures only. In order to assess potential immunoadjuvanticity, groups of germfree mice were inoculated with the three V. cholerae vaccine strains alone and compared to groups inoculated with the V. cholerae vaccine strains supplemented with purified CT as an oral immunoadjuvant or V. cholerae vaccine strains expressing LT(R192G) from pCS95. We found that mice continued to pass stool containing V. cholerae strains with pCS95 for at least 4 days after oral inoculation, the last day evaluated. We found that inoculation with V. cholerae vaccine strains containing pCS95 resulted in anti-LT(R192G) immune responses, confirming in vivo expression. We were unable to detect immune responses directed against the heterologous antigens expressed at low levels in any group of animals, including animals that received purified CT as an immunoadjuvant. We were, however, able to measure increased vibriocidal immune responses against vaccine strains in animals that received V. cholerae vaccine strains expressing LT(R192G) from pCS95 compared to the responses in animals that received V. cholerae vaccine strains alone. These results demonstrate that mutant LT molecules can be expressed in vivo by attenuated vaccine strains of V. cholerae and that such expression can result in an immunoadjuvant effect. PMID:10085006

Ryan, E T; Crean, T I; John, M; Butterton, J R; Clements, J D; Calderwood, S B

1999-04-01

75

Nasal Delivery of Antigen with the B Subunit of Escherichia coli Heat-Labile Enterotoxin Augments Antigen-Specific T-Cell Clonal Expansion and Differentiation  

Microsoft Academic Search

Escherichia coli heat-labile enterotoxin has unique immunogenic and adjuvant properties when administered mucosally to mice. These properties have revealed the potential for its use in the development of mucosal vaccines, an area of increasing interest. However, the inherent toxicity mediated by the A subunit precludes its widespread use. This problem has led to attempts to dissociate toxicity from adjuvant function

Maria Apostolaki; Neil A. Williams

2004-01-01

76

The presence of heat-labile factors interfering with binding analysis of fibrinogen with ferritin in horse plasma  

PubMed Central

Background Horse fibrinogen has been identified as a plasma specific ferritin-binding protein. There are two ways in the binding of ferritin-binding protein with ferritin: one is direct binding and the other is indirect binding which is heme-mediated. The aim of this study was to analyze the binding between horse fibrinogen and ferritin. Findings Although fibrinogen in horse plasma did not show the binding to ferritin coated on the plate wells, after following heat-treatment (60°C, 30 min) of horse plasma, plasma fibrinogen as well as purified horse fibrinogen bound to plates coated with horse spleen ferritin, but not with its apoferritin which lost heme as well as iron after the treatment of reducing reagent. Binding of purified or plasma fibrinogen to ferritin was inhibited by hemin and Sn-protoporphyrin IX (Sn-PPIX), but not by PPIX or Zn-PPIX. Conclusions Heat-treatment of horse plasma enabled plasma fibrinogen to bind to plate well coated with holo-ferritin. From the binding analysis of fibrinogen and ferritin, it is suggested that horse fibrinogen recognized iron or tin in complexed with the heme- or the hemin-ring, and also suggest that some fibrinogens circulate in the form of a complex with ferritin and/or heat-labile factors which inhibit the binding of fibrinogen with ferritin.

2013-01-01

77

EXPERIMENTAL SALMONELLOSIS. IV. LIPID CONTENT OF TOXIN L OBTAINED FROM SALMONELLA ENTERITIDIS.  

PubMed

Kawakami, Masaya (Gunma University, Maebashi, Japan), and Susumu Mitsuhashi. Experimental salmonellosis. IV. Lipid content of toxin L obtained from Salmonella enteritidis. J. Bacteriol. 89:193-197. 1965.-An improved method is described for the chromatographic purification of toxin L from virulent Salmonella enteritidis. Toxin L is heat-labile, and its toxicity is reduced by trypsin and by phospholipase A treatment. Chemical studies of chromatographically and ultracentrifugally homogeneous toxin preparations show that toxin L is a phosphorus-containing protein. The infrared-absorption spectrum of a petroleum ether extract of toxin L hydrolysate indicates that this material possesses a lipid component. PMID:14255662

KAWAKAMI, M; MITSUHASHI, S

1965-01-01

78

Preparation of biocompatible heat-labile enterotoxin subunit B-bovine serum albumin nanoparticles for improving tumor-targeted drug delivery via heat-labile enterotoxin subunit B mediation.  

PubMed

Heat-labile enterotoxin subunit B (LTB) is a non-catalytic protein from a pentameric subunit of Escherichia coli. Based on its function of binding specifically to ganglioside GM1 on the surface of cells, a novel nanoparticle (NP) composed of a mixture of bovine serum albumin (BSA) and LTB was designed for targeted delivery of 5-fluorouracil to tumor cells. BSA-LTB NPs were characterized by determination of their particle size, polydispersity, morphology, drug encapsulation efficiency, and drug release behavior in vitro. The internalization of fluorescein isothiocyanate-labeled BSA-LTB NPs into cells was observed using fluorescent imaging. Results showed that BSA-LTB NPs presented a narrow size distribution with an average hydrodynamic diameter of approximately 254±19 nm and a mean zeta potential of approximately -19.95±0.94 mV. In addition, approximately 80.1% of drug was encapsulated in NPs and released in the biphasic pattern. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that BSA-LTB NPs exhibited higher cytotoxic activity than non-targeted NPs (BSA NPs) in SMMC-7721 cells. Fluorescent imaging results proved that, compared with BSA NPs, BSA-LTB NPs could greatly enhance cellular uptake. Hence, the results indicate that BSA-LTB NPs could be a potential nanocarrier to improve targeted delivery of 5-fluorouracil to tumor cells via mediation of LTB. PMID:24851048

Zhao, Liang; Su, Rongjian; Cui, Wenyu; Shi, Yijie; Liu, Liwei; Su, Chang

2014-01-01

79

Preparation of biocompatible heat-labile enterotoxin subunit B-bovine serum albumin nanoparticles for improving tumor-targeted drug delivery via heat-labile enterotoxin subunit B mediation  

PubMed Central

Heat-labile enterotoxin subunit B (LTB) is a non-catalytic protein from a pentameric subunit of Escherichia coli. Based on its function of binding specifically to ganglioside GM1 on the surface of cells, a novel nanoparticle (NP) composed of a mixture of bovine serum albumin (BSA) and LTB was designed for targeted delivery of 5-fluorouracil to tumor cells. BSA-LTB NPs were characterized by determination of their particle size, polydispersity, morphology, drug encapsulation efficiency, and drug release behavior in vitro. The internalization of fluorescein isothiocyanate-labeled BSA-LTB NPs into cells was observed using fluorescent imaging. Results showed that BSA-LTB NPs presented a narrow size distribution with an average hydrodynamic diameter of approximately 254±19 nm and a mean zeta potential of approximately ?19.95±0.94 mV. In addition, approximately 80.1% of drug was encapsulated in NPs and released in the biphasic pattern. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that BSA-LTB NPs exhibited higher cytotoxic activity than non-targeted NPs (BSA NPs) in SMMC-7721 cells. Fluorescent imaging results proved that, compared with BSA NPs, BSA-LTB NPs could greatly enhance cellular uptake. Hence, the results indicate that BSA-LTB NPs could be a potential nanocarrier to improve targeted delivery of 5-fluorouracil to tumor cells via mediation of LTB.

Zhao, Liang; Su, Rongjian; Cui, Wenyu; Shi, Yijie; Liu, Liwei; Su, Chang

2014-01-01

80

Tissue culture and expression of Escherichia coli heat-labile enterotoxin B subunit in transgenic Peperomia pellucida.  

PubMed

The B subunit of Escherichia coli heat-labile enterotoxin (LTB), a non-toxic molecule with potent biological properties, is a powerful mucosal and parenteral adjuvant that induces a strong immune response against co-administered or coupled antigens. We synthesized a gene encoding the LTB adapted to the optimized coding sequences in plants and fused to the endoplasmic reticulum retention signal SEKDEL to enhance its expression level and protein assembly in plants. The synthetic LTB gene was located into a plant expression vector under the control of CaMV 35S promoter and was introduced into Peperomia pellucida by biolistic transformation method. The integration of synthetic LTB gene into genomic DNA of transgenic plants was confirmed by genomic DNA PCR amplification method. The assembly of plant-produced LTB was detected by western blot analysis. The amount of LTB protein produced in transgenic P. pellucida leaves was approximately 0.75% of the total soluble plant protein. Enzyme-linked immunosorbent assay indicated that plant-synthesized LTB protein bound specifically to GM1-ganglioside, which is receptor for LTB on the cell surface, suggesting that the LTB subunits formed biological active pentamers. PMID:20176109

Loc, Nguyen Hoang; Bach, Nguyen Hoang; Kim, Tae-Geum; Yang, Moon-Sik

2010-07-01

81

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

PubMed

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. PMID:355577

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

1978-07-01

82

Common somatic O and heat-labile serotypes among Campylobacter strains from sporadic infections in the United States.  

PubMed Central

Somatic O (formerly heat-stable) and heat-labile (HL) serotyping methods are commonly used to type Campylobacter jejuni and Campylobacter coli isolates. Although both systems are effective, the labor and time required for each have limited their application. These systems can be simplified by reducing the number of antisera used. To find an appropriate panel of antisera, we determined the distribution of common serotypes in the United States among a representative sample of 298 Campylobacter isolates. The strains, obtained between July 1989 and June 1990 from persons with sporadic cases of diarrhea, were collected from 19 randomly chosen counties in all geographic (census) regions of the United States. All strains were serotyped by the O and HL systems. By phenotypic methods, 288 C. jejuni, 9 hippurate-negative C. jejuni/C. coli, and 1 Campylobacter lari were identified. Of 57 O antisera, 24 typed 252 (84.6%) strains. Of the 55 HL antisera, 23 serotyped 253 (84.9%) strains. All strains were typeable in the unabsorbed O antisera. In the absorbed HL antisera, four strains were nontypeable and 14 were rough and untypeable. In each geographic region, 9 or more O and HL serotypes were found. Serotypes O:1, O:4, and O:13,16,43,50 and HL 1 were identified in all regions. The combination of both schemes gave greater discrimination than either system alone, but the maintenance of both requires a large resource investment. A serotyping scheme incorporating the 24 most prevalent O and 23 most prevalent HL serotypes could be useful for outbreak support and for surveillance. In the near future, we anticipate using a molecular subtyping method in combination with limited serotyping to distinguish Campylobacter strains.

Patton, C M; Nicholson, M A; Ostroff, S M; Ries, A A; Wachsmuth, I K; Tauxe, R V

1993-01-01

83

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

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

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

2013-06-28

84

Mucosal administration of the B subunit of E. coli heat-labile enterotoxin promotes the development of Foxp3-expressing regulatory T cells  

Microsoft Academic Search

Understanding the processes by which certain mucosal pathogens and their products induce regulatory T cells (Tregs) is important in determining mechanisms of pathogenicity and may point toward their use in treating immunological disorders. Accordingly, we have studied the events that follow mucosal administration of the B subunit of E. coli heat-labile enterotoxin (EtxB). EtxB modulates the response to co-administered antigens

D S Donaldson; K K Tong; N A Williams

2011-01-01

85

Efficient extracellular production of recombinant Escherichia coli heat-labile enterotoxin B subunit by using the expression\\/secretion system of Bacillus brevis and its mucosal immunoadjuvanticity  

Microsoft Academic Search

A gene encoding the mature Escherichia coli heat-labile enterotoxin B subunit (LTB) was introduced in a vector pNU212 and expressed at high levels in Bacillus brevis HPD31. The maximum amount of recombinant LTB (rLTB) secreted into the modified 5PY medium containing erythromycin was about 350 mg l?1 when cultivated at 30°C for 8 days. The rLTB purified directly from the culture

Satoshi Kozuka; Yoko Yasuda; Masanori Isaka; Nobutake Masaki; Tooru Taniguchi; Keiko Matano; Akihiko Moriyama; Kunio Ohkuma; Norihisa Goto; Shigezo Udaka; Kunio Tochikubo

2000-01-01

86

Human ubiquitin-activating enzyme (E1): Compensation for heat-labile mouse E1 and its gene localization on the X chromosome  

Microsoft Academic Search

The authors have constructed interspecific somatic cell hybrids between a temperature-sensitive (ts) mutant cell line of mouse FM3A cells, ts85, that has a heat-labile ubiquitin-activating enzyme (E1) and a human diploid fibroblast cell line, IMR-90. A hybrid clone that could grow stably at a nonpermissive temperature (39C) was obtained. Segregation of the hybrid cells at a permissive temperature (33C) gave

Mami Kudo; Takemi Enomoto; M. Uf; Kaoru Sugasawa; Fumio Hanaoka; Takaaki Hori

1991-01-01

87

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

PubMed

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

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

2012-06-01

88

Analysis of the role of flagella in the heat-labile Lior serotyping scheme of thermophilic Campylobacters by mutant allele exchange.  

PubMed Central

Flagellin mutations originally constructed in Campylobacter coli VC167 (serotype LIO8) by a gene replacement mutagenesis technique (P. Guerry, S. M. Logan, S. Thornton, and T. J. Trust, J. Bacteriol. 172:1853-1860, 1990) were moved from the original host into Campylobacter strains of a number of other Lior serogroups by a natural transformation procedure. This is the first report of the use of this transformation method to transfer a mutated locus among Campylobacter strains. Flagellin mutants were constructed in a number of heat-labile LIO serotypes and were serotyped and analyzed by immunoelectron microscopy with LIO typing antisera. In six cases, isogenic nonflagellated mutants were able to be serotyped in the same serogroup as their parent, and immunogold electron microscopy confirmed that antibodies in the typing antisera bound to components on the surface of both parent and mutant cells. However, in only one case, a strain belonging to serogroup LIO4, was a nonflagellated mutant untypeable, and immunogold electron microscopy showed that antibodies bound to the flagella filament of the parent but not to the cell surface. Furthermore, after introduction and expression as a flagellar filament of a LIO8 flagellin gene in this mutant, the strain could not be serotyped. These results indicate that a nonflagellar antigen is often the serodeterminant in the heat-labile Lior serotyping scheme. Images

Alm, R A; Guerry, P; Power, M E; Lior, H; Trust, T J

1991-01-01

89

Mucosal Immunization with Helicobacter, CpG DNA, and Cholera Toxin Is Protective  

Microsoft Academic Search

The mucosal delivery of antigens requires an effective adjuvant to induce mucosal immunity. Current mucosal adjuvants include cholera toxin (CT) and Escherichia coli heat-labile toxin. Unmethylated CpG immunostimulatory oligodeoxynucleotides (ODNs) have been proposed as novel mucosal adjuvants. In this study, mice were immunized with sonicated Helicobacter felis with CT and\\/or CpG ODN adjuvants. All groups receiving either adjuvant singly or

Weiwen Jiang; Henry J. Baker; Bruce F. Smith

2003-01-01

90

Seroepidemiology of heat-labile enterotoxigenic Escherichia coli and Norwalk virus infections in Panamanians, Canal Zone residents, Apache Indians, and United States Peace Corps volunteers.  

PubMed

Serum antibody titrations against the heat-labile enterotoxin (LT) of Escherichia coli were carried out on Panamanians, U.S. citizens resident in the Panama Canal Zone, Apache Indians living on the reservation in Whiteriver, Arizona, and Peace Corps volunteers before they traveled overseas. Antibody titers to Norwalk virus were also carried out on serum from Panamanian and Canal Zone residents. A high prevalence of low-titer LT antibodies was found in infants and adults from Panama, the Canal Zone, and Whiteriver. Panamanian children aged 1 to 5 years had the highest LT antibody titers. Peace Corps volunteers had a low prevalence and titer of LT antibodies. Prevalence and titer of antibodies to Norwalk virus were generally higher in Panamanians compared with Canal Zone residents of the same age. In the populations we studied, various modes of transmission and mechanisms of immunity likely explain the differences which we observed in antibody prevalence and titer to these two enteric pathogens. PMID:6290396

Ryder, R W; Greenberg, H; Singh, N; Oro, G; de Guardia, A; Sack, R B; Kapikian, A Z

1982-09-01

91

Mutants of the Escherichia coli heat-labile enterotoxin with reduced ADP-ribosylation activity or no activity retain the immunogenic properties of the native holotoxin.  

PubMed Central

The Escherichia coli heat-labile enterotoxin (LT) is a potent inducer of mucosal immune responses. In a previous study (L. DeHaan, W. R. Verweij, M. Holtrop, E. Agsteribbe, and J. Wilschut, Vaccine 14:620-626, 1996), we have shown that efficient induction of an LTB-specific mucosal immune response by LT requires the presence of the LTA chain, suggesting a possible role of the enzymatic activity of LTA in the induction of these responses. In the present study, we generated LT mutants with altered ADP-ribosylation activities and evaluated their immunogenicity upon intranasal administration to mice. The results demonstrate that the mucosal immunogenicity of LT is not dependent on its ADP-ribosylation activity.

de Haan, L; Verweij, W R; Feil, I K; Lijnema, T H; Hol, W G; Agsteribbe, E; Wilschut, J

1996-01-01

92

Human ubiquitin-activating enzyme (E1): Compensation for heat-labile mouse E1 and its gene localization on the X chromosome  

SciTech Connect

The authors have constructed interspecific somatic cell hybrids between a temperature-sensitive (ts) mutant cell line of mouse FM3A cells, ts85, that has a heat-labile ubiquitin-activating enzyme (E1) and a human diploid fibroblast cell line, IMR-90. A hybrid clone that could grow stably at a nonpermissive temperature (39C) was obtained. Segregation of the hybrid cells at a permissive temperature (33C) gave rise to temperature-sensitive clones. The electrophoresis of extracted histones and karyotype analysis of the segregants revealed a close correlation of the ability to grow at 39C, the presence of uH2A (ubiquitin-H2A semihistone) at 39C, and the presence of the human X chromosome. The sodium dodecyl sulfate-polyacrylamide gel electrophoretic pattern of affinity-purified E1 showed that this hybrid clone contained both human and mouse type E1. Thus they conclude that the functional gene for human E1 is located on the X chromosome.

Kudo, Mami; Enomoto, Takemi; Uf, M. (Univ. of Tokyo (Japan)); Sugasawa, Kaoru; Hanaoka, Fumio (RIKEN Inst., Saitama (Japan)); Hori, Takaaki (National Inst. of Radiological Sciences, Chiba (Japan))

1991-01-01

93

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

SciTech Connect

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.

Wang, M.-S.; Wolf, S. F.; Lipschutz, M. E.; Chemical Engineering; Purdue Univ.

1999-09-01

94

Analysis of Heat-Labile Sites Generated by Reactions of Depleted Uranium and Ascorbate in Plasmid DNA  

PubMed Central

The goal of this study was to characterize how depleted uranium (DU) causes DNA damage. Procedures were developed to assess the ability of organic and inorganic DNA adducts to convert to single strand breaks (SSB) in pBR322 plasmid DNA in the presence of heat or piperidine. DNA adducts formed by methyl methanesulfonate (MMS), cis-platin (cis-Pt), and chromic chloride were compared to those formed by reaction of uranyl acetate (UA) and ascorbate (Asc). Uranyl ion in the presence of Asc produced U-DNA adducts that converted to SSB upon heating. Piperidine, which acted on DNA methylated by MMS to convert methyl-DNA adducts to SSB, served in the opposite fashion with U-DNA adducts by decreasing SSB. The observation that piperidine also decreased the gel shift for metal-DNA adducts formed by monofunctional cis-Pt and chromic chloride was interpreted to suggest that piperidine served to remove U-DNA adducts. Radical scavengers did not affect formation of U-induced SSB, suggesting that SSB arose from the presence of U-DNA adducts and not from free radicals. A model is proposed to predict how U-DNA adducts may serve as initial lesions that convert to SSB or AP sites. Results suggest that DU can act as a chemical genotoxin that does not require radiation for its mode of action. Characterizing the DNA lesions formed by DU is necessary to assess the relative importance of different DNA lesions in the formation of DU-induced mutations. Understanding mechanisms of formation of DU-induced mutations may contribute to identification of biomarkers of DU exposures in humans.

Wilson, Janice; Young, Ashley; Civitello, Edgar R.

2013-01-01

95

Effects of nitric oxide in 5-hydroxytryptamine-, cholera toxin-, enterotoxigenic Escherichia coli- and Salmonella Typhimurium-induced secretion in the porcine small intestine  

Microsoft Academic Search

The effects of nitric oxide (NO) in the secretory response to the endogenous secretagogue 5-hydroxytryptamine (5-HT), the enterotoxins heat-labile enterotoxigenic Escherichia coli (ETEC) toxin (LT) and cholera toxin (CT), and various cultures of ETEC and Salmonella serotype Typhimurium in the porcine small intestine (Sus scrofa) were investigated. In anaesthetized pigs, jejunal tied-off loops were instilled with 5-HT, LT, CT, various

Marie Louise Grøndahl; Martin Andreas Unmack; Helga Berglind Ragnarsdóttir; Mark Berner Hansen; John Elmerdahl Olsen; Erik Skadhauge

2005-01-01

96

Decreased Heat-Labile Opsonic Activity and Complement Levels Associated with Evidence of C3 Breakdown Products in Infected Pleural Effusions  

PubMed Central

Heat-labile opsonic activity was measured simultaneously in serum and pleural fluid of patients with transudates, infectious exudates (with positive or negative bacterial culture) and neoplastic exudates, using two different complement-dependent phagocytic tests: the killing of Staphylococcus aureus Wood 46 variant strain (K50 opsonic titers) and the assessment of ingestion rate of endotoxin-coated paraffin particles (Oil Red 0 uptake test). K50 opsonic titers were lower in culture-positive pleural effusions as compared to culture-negative (P < 0.002) or neoplastic effusions (P < 0.002). These results were corroborated by the Oil Red 0 uptake test. The data obtained with the two assays showed a significant correlation (P < 0.001). The hemolytic activity of complement (CH50) as well as the levels of C3 breakdown product, C3d, were measured in the same sera and pleural fluid samples and in an additional group of patients with pleural effusions of the same etiology. Effusions with positive cultures showed lower CH50 values (P < 0.01) and higher C3d values (P < 0.05) when compared to culture-negative pleural fluids. Finally, evidence for immune complexes in pleural effusions and sera was looked for by determination of Clq binding activity. Levels were higher in culture-positive effusions when compared to culture-negative fluids (P = 0.005). K50 opsonic titers showed a positive correlation with CH50 values (P < 0.001) for all fluids tested. Similarly Clq binding activity correlated with C3d levels in effusions of infectious origin (P = 0.05). Recovery experiments using the various bacterial species isolated from culture-positive pleural effusions showed evidence of complement inactivation upon incubation with pooled sera at concentrations of 107-108 microorganisms/ml. These results indicate that one important reason for bacterial persistence in empyema may be decreased opsonization secondary to local consumption of complement. Images

Lew, Pablo D.; Zubler, Rudolf; Vaudaux, Pierre; Farquet, Jean J.; Waldvogel, Francis A.; Lambert, Paul-Henri

1979-01-01

97

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

PubMed

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

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

2013-03-23

98

Development and testing of a nonradioactive DNA oligonucleotide probe that is specific for Vibrio cholerae cholera toxin.  

PubMed Central

An alkaline phosphatase-labeled oligonucleotide DNA probe (CTAP) that was specific for the cholera toxin gene (ctxA) was identified. All cholera toxin-producing strains of Vibrio cholerae, regardless of serotype, hybridized with the CTAP probe, while nontoxigenic strains from either environmental sources or from deletion or substitution mutations did not hybridize. Unlike the whole-gene probes for either ctxA or for the heat-labile toxin or Escherichia coli (eltA), this 23-base sequence did not hybridize with E. coli or with vibrios other than V. cholerae that produce related toxins. By using CTAP to identify colonies grown on nonselective medium, V. cholerae was enumerated at concentrations of 10(3) to 10(7)/g from stool samples of volunteers who had ingested V. cholerae O1 strain 569B. CTAP provides a specific and sensitive tool for diagnosis and environmental monitoring of cholera toxin-producing V. cholerae. Images

Wright, A C; Guo, Y; Johnson, J A; Nataro, J P; Morris, J G

1992-01-01

99

Characteristics of the labile neurotoxin associated with nervous coccidiosis.  

PubMed Central

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.

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

1987-01-01

100

Detection of virulence factors in culturable Escherichia coli isolates from water samples by DNA probes and recovery of toxin-bearing strains in minimal o-nitrophenol-beta-D-galactopyranoside-4-methylumbelliferyl-beta-D-g luc uronide media.  

PubMed Central

A total of 449 Escherichia coli isolates in treated and raw water sources were submitted to DNA-DNA hybridization using seven different DNA probes to detect homology to sequences that code for Shiga-like toxins I and II; heat-stabile and heat-labile toxins, adherence factors EAF and eae, and the fimbrial antigen of entero-hemorrhagic E. coli. Fifty-nine (13%) of the isolates demonstrated homology with one or more specific DNA probes. More than 50% of the isolates in treated water were not recovered in MMO-4-methylumbelliferyl-beta-D-glucuronide media designed for detection of this indicator. Images

Martins, M T; Rivera, I G; Clark, D L; Olson, B H

1992-01-01

101

Increased proteolysis of diphtheria toxin by human monocytes after heat shock: a subsidiary role for heat-shock protein 70 in antigen processing.  

PubMed

The expression of heat-shock proteins (hsp) increases after exposure to various stresses including elevated temperatures, oxidative injury, infection and inflammation. As molecular chaperones, hsp have been shown to participate in antigen processing and presentation, in part through increasing the stability and expression of major histocompatibility complex molecules. Heat shock selectively increases human T-cell responses to processed antigen, but does not affect T-cell proliferation induced by non-processed antigens. Here, we have analysed the mechanisms by which stress such as heat shock, and the ensuing hsp over-expression affect the processing of diphtheria toxin (DT) in peripheral blood monocytes. We found that heat shock increased DT proteolysis in endosomes and lysosomes while the activities of the cathepsins B and D, classically involved in DT proteolysis, were decreased. These effects correlated with the heat-shock-mediated increase in hsp 70 expression observed in endosomes and lysosomes. Actinomycin D or blocking anti-hsp 70 antibodies abolished the heat-shock-mediated increase in DT proteolysis. These data indicate that the increased expression of hsp 70 constitutes a subsidiary mechanism that facilitates antigen proteolysis in stressed cells. Confirming these data, presentation by formaldehyde-fixed cells of DT proteolysates that were obtained with endosomes and lysosomes from heat-shocked peripheral blood monocytes showed higher stimulation of T cells than those generated with endosomes and lysosomes from control peripheral blood monocytes. PMID:17116171

Polla, Barbara S; Gabert, Françoise; Peyrusse, Brigitte M-N; Jacquier-Sarlin, Muriel R

2007-02-01

102

Increased proteolysis of diphtheria toxin by human monocytes after heat shock: a subsidiary role for heat-shock protein 70 in antigen processing  

PubMed Central

The expression of heat-shock proteins (hsp) increases after exposure to various stresses including elevated temperatures, oxidative injury, infection and inflammation. As molecular chaperones, hsp have been shown to participate in antigen processing and presentation, in part through increasing the stability and expression of major histocompatibility complex molecules. Heat shock selectively increases human T-cell responses to processed antigen, but does not affect T-cell proliferation induced by non-processed antigens. Here, we have analysed the mechanisms by which stress such as heat shock, and the ensuing hsp over-expression affect the processing of diphtheria toxin (DT) in peripheral blood monocytes. We found that heat shock increased DT proteolysis in endosomes and lysosomes while the activities of the cathepsins B and D, classically involved in DT proteolysis, were decreased. These effects correlated with the heat-shock-mediated increase in hsp 70 expression observed in endosomes and lysosomes. Actinomycin D or blocking anti-hsp 70 antibodies abolished the heat-shock-mediated increase in DT proteolysis. These data indicate that the increased expression of hsp 70 constitutes a subsidiary mechanism that facilitates antigen proteolysis in stressed cells. Confirming these data, presentation by formaldehyde-fixed cells of DT proteolysates that were obtained with endosomes and lysosomes from heat-shocked peripheral blood monocytes showed higher stimulation of T cells than those generated with endosomes and lysosomes from control peripheral blood monocytes.

Polla, Barbara S; Gabert, Francoise; Peyrusse, Brigitte M-N; Jacquier-Sarlin, Muriel R

2007-01-01

103

Escherichia coli Heat-Stable Toxin b Impairs Intestinal Epithelial Barrier Function by Altering Tight Junction Proteins  

PubMed Central

Escherichia coli heat-stable toxin b (STb) causes diarrhea in animals. STb binds to sulfatide, its receptor, and is then internalized. In the cytoplasm, through a cascade of events, STb triggers the opening of ion channels, allowing ion secretion and water loss and leading to diarrhea. Tight junctions (TJs) are well known for controlling paracellular traffic of ions and water by forming a physical intercellular barrier in epithelial cells, and some bacterial toxins are known to affect adversely TJs. The present study aimed at determining the effect of STb on TJs. T84 cells were treated for 24 h with purified STb and a nontoxic STb mutant (D30V). Transepithelial resistance (TER), paracellular flux marker, and confocal microscopy were used to analyze the effect of STb on TJs. Purified STb caused a significant reduction of TER parallel to an increase in paracellular permeability compared to the results seen in untreated cells or mutant D30V. The increased paracellular permeability was associated with a marked alteration of F-actin stress fibers. F-actin filament dissolution and condensation were accompanied by redistribution and/or fragmentation of ZO-1, claudin-1, and occludin. These changes were also observed following treatment of T84 cells with an 8-amino-acid peptide found in the STb sequence corresponding to a consensus sequence of Vibrio cholerae Zot toxin. These effects were not observed with a scrambled peptide or mutant D30V. Our findings indicate that STb induces epithelial barrier dysfunction through changes in TJ proteins that could contribute to diarrhea.

Ngendahayo Mukiza, Clement

2013-01-01

104

Evaluation of the immunogenicity of a transgenic tobacco plant expressing the recombinant fusion protein of GP5 of porcine reproductive and respiratory syndrome virus and B subunit of Escherichia coli heat-labile enterotoxin in pigs.  

PubMed

Escherichia coli heat-labile enterotoxin B subunit (LTB) can be used as an adjuvant for co-administered antigens. Our previous study showed that the expression of neutralizing epitope GP5 of porcine reproductive and respiratory syndrome virus (PRRSV) in transgenic tobacco plant (GP5-T) could induce PRRSV-specific immune responses in pigs. A transgenic tobacco plant co-expressing LTB and PRRSV GP5 as a fusion protein (LTB-GP5-T) was further constructed and its immunogenicity was evaluated. Pigs were given orally three consecutive doses of equal concentration of recombinant GP5 protein expressed in leaves of LTB-GP5-T or GP5-T at a 2-week interval and challenged with PRRSV at 7 weeks post-initial immunization. Pigs receiving LTB-GP5-T or GP5-T developed PRRSV-specific antibody- and cell-mediated immunity and showed significantly lower viremia and tissue viral load and milder lung lesions than wild type tobacco plant (W-T). The LTB-GP5-T-treated group had relatively higher immune responses than the GP5-T-treated group, although the differences were not statistically significant. PMID:21277027

Chia, Min-Yuan; Hsiao, Shih-Hsuan; Chan, Hui-Ting; Do, Yi-Yin; Huang, Pung-Ling; Chang, Hui-Wen; Tsai, Yi-Chieh; Lin, Chun-Ming; Pang, Victor Fei; Jeng, Chian-Ren

2011-04-15

105

Randomized Clinical Trial Assessing the Safety and Immunogenicity of Oral Microencapsulated Enterotoxigenic Escherichia coli Surface Antigen 6 with or without Heat-Labile Enterotoxin with Mutation R192G?  

PubMed Central

An oral, microencapsulated anti-colonization factor 6 antigen (meCS6) vaccine, with or without heat-labile enterotoxin with mutation R192G (LTR192G) (mucosal adjuvant), against enterotoxigenic Escherichia coli (ETEC) was evaluated for regimen and adjuvant effects on safety and immunogenicity. Sixty subjects were enrolled into a three-dose, 2-week interval or four-dose, 2-day interval regimen. Each regimen was randomized into two equal groups of meCS6 alone (1 mg) or meCS6 with adjuvant (2 ?g of LTR192G). The vaccine was well tolerated and no serious adverse events were reported. Serologic response to CS6 was low in all regimens (0 to 27%). CS6-immunogloublin A (IgA) antibody-secreting cell (ASC) responses ranged from 36 to 86%, with the highest level in the three-dose adjuvanted regimen; however, the magnitude was low. As expected, serologic and ASC LT responses were limited to adjuvanted regimens, with the exception of fecal IgA, which appeared to be nonspecific to LT administration. Further modifications to the delivery strategy and CS6 and adjuvant dose optimization will be needed before conducting further clinical trials with this epidemiologically important class of ETEC.

Lapa, Joyce A.; Sincock, Stephanie A.; Ananthakrishnan, Madhumita; Porter, Chad K.; Cassels, Frederick J.; Brinkley, Carl; Hall, Eric R.; van Hamont, John; Gramling, Joseph D.; Carpenter, Colleen M.; Baqar, S.; Tribble, David R.

2008-01-01

106

Purification and characterization of salmolysin, an extracellular hemolytic toxin from Aeromonas salmonicida.  

PubMed Central

An extracellular hemolytic toxin of Aeromonas salmonicida, termed salmolysin, was purified 945-fold by ammonium sulfate precipitation, anion-exchange chromatography on DEAE-cellulose, and gel filtration chromatography on Sephadex G-100 and Sepharose 2B. Salmolysin appeared homogeneous upon cellulose acetate membrane electrophoresis and immunodiffusion analysis. The molecular weight of the toxin was estimated to be approximately 200,000 by the sedimentation equilibrium method. The UV absorption spectrum showed a maximum at 275 nm and a minimum at 262 nm. The isoelectric point was found to be at pI 5.4. Carbohydrate and protein analyses and other biochemical data indicated that salmolysin is a glycoprotein, containing approximately 62% carbohydrates. The toxin is a heat-labile substance and is stable at a neutral pH value. Ferrous ion inhibited the activity, whereas metal-chelating agents did not affect the activity. Sulfhydryl reagents did not inhibit the toxin, whereas reducing agents, such as L-cysteine and reduced glutathione, inhibited the toxin to a certain extent. Salmolysin was inactivated by a nonionic detergent but was stimulated by an anionic detergent, sodium deoxycholate, at a low concentration. The toxin was also inactivated by subtilisin and trypsin but was not inhibited by papain and pepsin. Salmolysin, with a remarkable hemolytic activity against salmonid erythrocytes, was lethal to rainbow trout when it was injected intramuscularly. Images

Nomura, S; Fujino, M; Yamakawa, M; Kawahara, E

1988-01-01

107

Metal Complexes and Free Radical Toxins Produced by Pfiesteria piscicida  

SciTech Connect

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.

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

2007-01-01

108

Metal Complexes And Free Radical Toxins Produced By Pfiesteria Piscicida  

SciTech Connect

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.

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

109

[Necrotizing enteritis in suckling pigs (Clostridium perfringens type C enterotoxemia). II. Toxin formation, heat and drug resistance of Clostridium perfringens strains isolated from suckling pigs and broilers with necrotizing enteritis].  

PubMed

Nineteen Clostridium perfringens Type C strains and ten foreign control strains of subtypes C1, C3, and C4 were tested for their toxin formation and spore resistance to heat. The 19 Type C strains had been isolated from unweaned piglets in the context of necrotising enteritis outbreaks in the GDR. The Clostridium perfringens Type C strains formed beta-toxin, but they failed to form epsilon-toxin or gamma-toxin, alpha-toxin was successfully recorded from 15 of the 19 strains tested from unweaned piglets. The minor-lethal toxin fractions were also tested, with delta-toxin being recorded from all strains, non-alpha-delta-theta-toxin from six, theta-toxin from five, and K-toxin from one. Tests for delta-toxin, lambda-toxin, and mu-toxin were negative. The Clostridium perfringens Type C strains isolated in the GDR from unweaned piglets with necrotising enteritis were, basically, identical with those described in Denmark by von Hogh (1967) with regard to toxin formation. Clostridium perfringens strains cultured in broilers with necrotising enteritis were characterised by regular toxin production in the context of alpha, theta, delta as well as non-alpha-delta-theta. They failed to form beta, epsilon, gamma and lambda, while mu-toxin was formed by them quite irregularly. They, consequently, are Type A strains. Resistance to chloramphenicol and/or oxytetracycline was exhibited by 78.5 per cent of 237 tested Clostridium perfringens strains which had been isolated from unweaned piglets and broilers with necrotosing enteritis. Multiple resistance was recorded from 33.9 per cent. All strains were susceptible to penicillin, nitrofurantoin, and erythromycin. PMID:219797

Köhler, B

1978-01-01

110

Chimeric toxins  

US Patent & Trademark Office Database

A chimeric toxin is disclosed. In a preferred embodiment, the chimeric toxin comprises a botulinal neurotoxin heavy chain and non-clostridial toxin chain. A method of creating a chimeric toxin is also disclosed. The chimeric toxin will have utility for pharmacological treatment of neurological disorders.

2003-04-08

111

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

PubMed

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

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

2013-08-01

112

Construction of a recombinant-attenuated Salmonella Enteritidis strain secreting Escherichia coli heat-labile enterotoxin B subunit protein and its immunogenicity and protection efficacy against salmonellosis in chickens.  

PubMed

A live attenuated Salmonella Enteritidis (SE) strain secreting Escherichia coli heat-labile enterotoxin B subunit (LTB) protein was constructed as a new vaccine candidate. The comparative effect of this vaccine candidate was evaluated with a previously reported SE vaccine, JOL919. An asd+, p15A ori plasmid containing eltB-encoding LTB was introduced into a ?lon?cpxR?asd SE strain, and designated as JOL1364. In a single immunization experiment, group A chickens were orally inoculated with phosphate-buffered saline as a control, group B chickens were orally immunized with JOL919, and group C chickens were orally immunized with JOL1364. The immunized groups B and C showed significantly higher systemic, mucosal and cellular immune responses as compared to those of the control group. In addition, the immunized group C showed significantly higher mucosal and cellular immune responses as compared to those of the immunized group B at the 1st week post-immunization. In the examination of protection efficacy, the immunized groups B and C showed lower gross lesion scores in the liver and spleen, and lower bacterial counts of SE challenge strain in the liver, spleen, and caeca as compared to those of the control group. The number of SE-positive birds was significantly lower in the immunized group C as compared to that of the control group at the 14th day post-challenge. In addition, the number of birds carrying the challenge strain in the caeca was significantly lower in the immunized group C than those in the immunized group B and control group at the 7th and 14th day post-challenge. These results indicate that immunization with the JOL1364 vaccine candidate can induce higher mucosal and cellular immune responses than those of the JOL919 for efficient protection against salmonellosis. PMID:24176491

Nandre, Rahul M; Lee, John Hwa

2014-01-01

113

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

PubMed Central

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.

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

1987-01-01

114

Enteroaggregative Escherichia coli Heat-Stable Enterotoxin 1 Represents Another Subfamily of E. coli Heat-Stable Toxin  

Microsoft Academic Search

Enteroaggregative Escherichia coli (EAggEC) are associated with persistent diarrhea in young children. Some of these organisms produce a low-molecular-weight, heat-stable, plasmid-encoded enterotoxin that has been named EAggEC heat-stable enterotoxin 1 (EAST1). We have cloned a 4.4-kb DNA fragment from the virulence plasmid of prototype EAggEC strain 17-2, which expresses enterotoxic activity as measured by electrogenic response in Ussing chambers mounted

Stephen J. Savarino; Alessio Fasano; John Watson; Brian M. Martin; Myron M. Levine; Stefano Guandalini; Patricia Guerry

1993-01-01

115

Labile and non-labile desorption rate constants for 33 PCB congeners from lake sediment suspensions  

Microsoft Academic Search

Lake sediments contaminated with polychlorinated biphenyls (PCBs) were purged using a gas stripping technique to estimate desorption rate constants. Desorption profiles and modeling of the data clearly show a two-step release of PCBs from sediment suspensions that can be described as a labile (fast) release followed by a non-labile (slow) release. Data are summarized by labile and non-labile rate constants

F. M. Dunnivant; J. T. Coates; A. W. Elzerman

2005-01-01

116

Dermonecrotic toxin and tracheal cytotoxin, putative virulence factors of Bordetella avium.  

PubMed Central

We examined Bordetella avium for virulence factors common to Bordetella pertussis, including pertussis toxin, filamentous hemagglutinin, adenylate cyclase, dermonecrotic toxin, and tracheal cytotoxin. B. avium produced a dermonecrotic toxin and a tracheal cytotoxin. The dermonecrotic toxin of B. avium is a 155,000-molecular-weight, heat-labile protein which was lethal for mice, guinea pigs, young chickens, and turkey poults and produced dermonecrosis when injected intradermally into guinea pigs, chickens, and turkey poults. High-pressure liquid chromatography of B. avium culture supernatant fluid revealed the presence of a tracheal cytotoxin chemically identical to that produced by B. pertussis. B. avium isolates were negative for B. pertussis-like filamentous hemagglutinin and pertussis toxin when assayed with antibody against B. pertussis filamentous hemagglutinin and pertussis toxin. Furthermore, B. avium failed to induce the clustered CHO cell morphology characteristic of pertussis toxin. Adenylate cyclase assays indicated that B. avium does not produce an extracytoplasmic adenylate cyclase, even after passage through embryonated turkey eggs. Since production of virulence proteins by B. pertussis is regulated by growth in media containing nicotinamide or MgSO4 or by growth at reduced temperatures, we determined the effect of these supplements and growth conditions on production of dermonecrotic toxin by B. avium. Production of dermonecrotic toxin in B. avium was not altered by growth in media containing 100 microM FeSO4 or 500 micrograms of nicotinamide per ml or by growth at 25 or 42 degrees C, but production was significantly decreased by growth in media containing 20 mM MgSO4 and slightly reduced by growth in media containing 500 micrograms of nicotinic acid per ml. These studies revealed that B. avium is similar to B. pertussis in that both species produce a dermonecrotic toxin and a tracheal cytotoxin and production of dermonecrotic toxin is regulated by nicotinamide and MgSO4. The presence of dermonecrotic toxin and tracheal cytotoxin in all Bordetella species indicates that these products may be important virulence factors in bordetellosis. Images

Gentry-Weeks, C R; Cookson, B T; Goldman, W E; Rimler, R B; Porter, S B; Curtiss, R

1988-01-01

117

Detection of proteinous toxins using the BioThreat Alert system, part 3: effects of heat pretreatment and interfering substances  

Microsoft Academic Search

We previously reported that the Guardian Bio-Threat Alert (BTA) system could detect (detection limit: about 0.1 ?g\\/ml) staphylococcal\\u000a enterotoxin B (SEB), botulinum toxins (BTX) A and B, and ricin, with no interference by white-powdered materials or colored\\u000a matrices. In this study, the capability of the BTA system was further assessed. With 10 min of preheating at 60°C, all toxins\\u000a could

Yasuhiro Sano; Shigeharu Yamashiro; Asuka Komano; Hisashi Maruko; Hiroshi Sekiguchi; Yasuo Takayama; Ryoji Sekioka; Kouichiro Tsuge; Isaac Ohsawa; Mieko Kanamori-Kataoka; Yasuo Seto; Akiyoshi Satoh

2007-01-01

118

Production of cholera toxin-like toxin by Vibrio mimicus and non-O1 Vibrio cholerae: batch culture conditions for optimum yields and isolation of hypertoxigenic lincomycin-resistant mutants.  

PubMed Central

Vibrio mimicus 61892, isolated in 1977 from a case of watery diarrhea in Bangladesh, produces an enterotoxin which possesses activity in Y-1 mouse adrenal cells and in rabbit ileal loops which is identical to the prototype cholera toxin (CT) produced by Vibrio cholerae 569B. The neutralization of the adrenal cell activity of 61892 toxin and 569B CT by homologous and heterologous antisera generates parallel titration curves which show complete neutralization in all cases. Paired titrations in the ganglioside GM1 enzyme-linked immunosorbent assay (using either CT or Escherichia coli heat-labile toxin antitoxin) of both toxins indicates that 61892 toxin is antigenically indistinguishable from 569B CT. The specific activity of the two toxins in the rabbit ileal loop is virtually identical. Batch culture production of CT-like toxin and CT by isolates of V. mimicus and different biotypes of V. cholerae was found to be highest in shake flask cultures of Casamino Acids-yeast extract broth grown at 27 degrees C with vigorous aeration. Incorporation of lincomycin into the growth medium at a concentration of 50 micrograms/ml increased yields from wild-type strains. Dramatically higher yields were obtained when a spontaneous resistance mutant of strain 61892 was grown in the presence of 200 to 300 micrograms of lincomycin per ml. Under these conditions, yields of CT-like toxin were increased by 300- to 500-fold, and the highest yields reached more than 100 micrograms/ml after 44 h of culture. This is substantially higher than that reported in the literature for CT production by any strain of V. cholerae, including hypertoxigenic strain 569B.

Spira, W M; Fedorka-Cray, P J

1983-01-01

119

Arginine-Specific Mono ADP-Ribosylation In Vitro of Antimicrobial Peptides by ADP-Ribosylating Toxins  

PubMed Central

Among the several toxins used by pathogenic bacteria to target eukaryotic host cells, proteins that exert ADP-ribosylation activity represent a large and studied family of dangerous and potentially lethal toxins. These proteins alter cell physiology catalyzing the transfer of the ADP-ribose unit from NAD to cellular proteins involved in key metabolic pathways. In the present study, we tested the capability of four of these toxins, to ADP-ribosylate ?- and ?- defensins. Cholera toxin (CT) from Vibrio cholerae and heat labile enterotoxin (LT) from Escherichia coli both modified the human ?-defensin (HNP-1) and ?- defensin-1 (HBD1), as efficiently as the mammalian mono-ADP-ribosyltransferase-1. Pseudomonas aeruginosa exoenzyme S was inactive on both HNP-1 and HBD1. Neisseria meningitidis NarE poorly recognized HNP-1 as a substrate but it was completely inactive on HBD1. On the other hand, HNP-1 strongly influenced NarE inhibiting its transferase activity while enhancing auto-ADP-ribosylation. We conclude that only some arginine-specific ADP-ribosylating toxins recognize defensins as substrates in vitro. Modifications that alter the biological activities of antimicrobial peptides may be relevant for the innate immune response. In particular, ADP-ribosylation of antimicrobial peptides may represent a novel escape mechanism adopted by pathogens to facilitate colonization of host tissues.

Castagnini, Marta; Picchianti, Monica; Talluri, Eleonora; Biagini, Massimiliano; Del Vecchio, Mariangela; Di Procolo, Paolo; Norais, Nathalie; Nardi-Dei, Vincenzo; Balducci, Enrico

2012-01-01

120

Pertussis toxin  

SciTech Connect

This book contains 13 selections. Some of the titles are: Genetic and Functional Studies of Pertussis Toxin Substrates; Effect of Pertussis Toxin on the Hormonal Responsiveness of Different Tissues; Extracellular Adenylate Cyclase of Bordetella pertussis; and GTP-Regulatory Proteins are Introcellular Messagers: A Model for Hormone Action.

Sekura, R.D.; Moss, J.; Vaughan, M.

1985-01-01

121

Labile sulfide and sulfite in phytochelatin complexes  

SciTech Connect

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.

Eannetta, N.T.; Steffens, J.C. (Cornell Univ., Ithaca, NY (USA))

1989-04-01

122

Botulinum toxin.  

PubMed

Botulinum toxin is regarded as the most lethal substance known. It is estimated that the human LD50 for inhalation botulism is 1 to 3 nanograms of toxin/kilogram body mass. Although only three cases of inhalational botulism have been described, an understanding of the pathophysiology of food-borne outbreaks, wound botulism, and infant botulism, and their therapies, enables the medical community to plan treatment in the event of an aerosol release of botulinum toxin. Antitoxin, vaccine, and F(ab')2 immune fragment therapies are discussed as adjuncts to supportive therapy. PMID:16168317

Horowitz, B Zane

2005-10-01

123

Protection against Shiga toxin-producing Escherichia coli infection by transcutaneous immunization with Shiga toxin subunit B.  

PubMed

Enterohemorrhagic Escherichia coli (EHEC) strains are important human food-borne pathogens. EHEC strains elaborate potent Shiga toxins (Stx1, and/or Stx2) implicated in the development of hemorrhagic colitis (HC) or hemolytic-uremic syndrome (HUS). In this report, we evaluated the immunogenicity and protective efficacy of Stx1 subunit B (StxB1) administered by transcutaneous immunization (TCI). Three groups of Dutch Belted rabbits received patches containing StxB1, StxB1 in combination with Escherichia coli heat-labile enterotoxin (LT), or LT alone. An additional group of naïve rabbits served as controls. The protective efficacy following TCI with StxB1 was assessed by challenging rabbits with a virulent Stx1-producing strain, RDEC-H19A, capable of inducing HC and HUS in rabbits. Antibodies specific to StxB1 from serum and bile samples were determined by enzyme-linked immunosorbent assay and toxin neutralization test. Rabbits immunized with StxB1 demonstrated improved weight gain and reduced Stx-induced histopathology. Rabbits receiving StxB or StxB1/LT showed a significant increase in serum immunoglobulin G titers specific to StxB1 as well as toxin neutralization titers. These data demonstrated that the StxB delivered by TCI could induce significant systemic immune responses. Thus, Stx subunit B vaccine delivered by a patch for a high-risk population may be a practical approach to prevent (and/or reduce) Stx-induced pathology. PMID:18003816

Zhu, C; Yu, J; Yang, Z; Davis, K; Rios, H; Wang, B; Glenn, G; Boedeker, E C

2008-02-01

124

A new form of Niemann-Pick disease characterised by temperature-labile sphingomyelinase.  

PubMed Central

A new type (F) of Niemann-Pick disease characterised by childhood onset of splenomegaly, lack of neurological involvement, and diminished sphingomyelinase activity is described. The clinical presentation and heat-labile sphingomyelinase activity of this type F Niemann-Pick disease distinguishes it from other types of Niemann-Pick disease.

Schneider, E L; Pentchev, P G; Hibbert, S R; Sawitsky, A; Brady, R O

1978-01-01

125

Neuromodulators (Botulinum Toxin Therapy)  

MedlinePLUS

... at the corners of the eyes. What is botulinum toxin? Botulinum toxin is a purified toxin and, when ... needed for expression and important functions like eating. Botulinum toxin therapy Treatment involves injection of very small amounts ...

126

BOTULINUM TOXIN  

PubMed Central

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.

Nigam, P K; Nigam, Anjana

2010-01-01

127

Clostridial toxins  

PubMed Central

The current global outbreak of Clostridium difficile infection exemplifies the major public health threat posed by clostridial glucosylating toxins. In the western world, C. difficile infection is one of the most prolific causes of bacterial-induced diarrhea and potentially fatal colitis. Two pathogenic enterotoxins, TcdA and TcdB, cause the disease. Vancomycin and metronidazole remain readily available treatment options for C. difficile infection, but neither is fully effective as is evident by high clinical relapse and fatality rates. Thus, there is an urgent need to find an alternative therapy that preferentially targets the toxins and not the drug-resistant pathogen. Recently, we addressed these critical issues in a Nature Medicine letter, describing a novel host defense mechanism for subverting toxin virulence that we translated into prototypic allosteric therapy for C. difficile infection. In this addendum article, we provide a continued perspective of this antitoxin mechanism and consider the broader implications of therapeutic allostery in combating gut microbial pathogenesis.

Oezguen, Numan; Power, Trevor D.; Urvil, Petri; Feng, Hanping; Pothoulakis, Charalabos; Stamler, Jonathan S.; Braun, Werner; Savidge, Tor C.

2012-01-01

128

Isolation of a labile homoleptic diazenium cation.  

PubMed

Following our interest in nitrogen chemistry, we now describe the synthesis, structure, and bonding of labile disilylated diazene, its GaCl3 adduct, and the intriguing trisilylated diazenium ion [(Me3 Si)2 N?N-SiMe3 ](+), a dark blue and highly labile (Tdecomp >-30?°C) homoleptic cation of the type [R3 N2 ](+). Although direct silylation of Me3 Si-N=N-SiMe3 failed, the [(Me3 Si)2 N=N-SiMe3](+) ion was generated in a straightforward two-electron oxidation reaction from mercury(II) dihydrazide and Ag[GaCl4]. Moreover, previous structure data of Me3 Si-N?N-SiMe3 were revised on the basis of new data. PMID:24532131

Baumann, Wolfgang; Michalik, Dirk; Reiß, Fabian; Schulz, Axel; Villinger, Alexander

2014-03-17

129

The labile nature of consolidation theory.  

PubMed

'Consolidation' has been used to describe distinct but related processes. In considering the implications of our recent findings on the lability of reactivated fear memories, we view consolidation and reconsolidation in terms of molecular events taking place within neurons as opposed to interactions between brain regions. Our findings open up a new dimension in the study of memory consolidation. We argue that consolidation is not a one-time event, but instead is reiterated with subsequent activation of the memories. PMID:11257912

Nader, K; Schafe, G E; LeDoux, J E

2000-12-01

130

Enteroaggregative Escherichia coli Heat-Stable Enterotoxin 1 Represents Another Subfamily of E. coli Heat-Stable Toxin. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

Enteroaggregative Escherichia coli (EAggEC) are associated with persistent diarrhea in young children. Some of these organisms produce a low-molecular-weight, heat-stable, plasmid-encoded enterotoxin that has been named EAggEC heat-stable enterotoxin 1 (E...

S. J. Savarino A. Fasano J. Watson B. M. Martin M. M. Levine

1993-01-01

131

Protein function: Chaperonin turned insect toxin  

Microsoft Academic Search

Antlions are larvae of the Myrmeleontidae family that live on other insects by sucking out the body fluid from their prey, after first paralysing it with a toxin produced by salivary bacteria. Here we show that the paralysing toxin produced by bacterial endosymbionts in the saliva of Myrmeleon bore larvae is a homologue of GroEL, a protective heat-shock protein known

Naofumi Yoshida; Kenji Oeda; Eijiro Watanabe; Toshiyuki Mikami; Yoshikazu Fukita; Keiichiro Nishimura; Koichiro Komai; Kazuhiko Matsuda

2001-01-01

132

Prevalence of Vibrio cholerae with heat-stable enterotoxin (NAG-ST) and cholera toxin genes; restriction fragment length polymorphisms of NAG-ST genes among V. cholerae O serogroups from a major shrimp production area in Thailand  

Microsoft Academic Search

Summary. A total of 148 Vibrio cholerae isolates from a major shrimp production area in Southern Thailand were examined by colony hybridisation for genes encoding heat-stable enterotoxin (NAG-ST) and cholera toxin (CT). Only non-01 I\\/. cholerae strains were found to harbour NAG-ST (14 of 146) whereas no strains hybridised with the CT probe. NAG-ST- positive V. cholerue non-01 strains were

A. Dalsgaard; O. Serichantalergs; T. Shimada; O. Sethabutr; P. Echeverria

1995-01-01

133

Lability criteria in diffusive gradients in thin films.  

PubMed

The penetration of metal complexes into the resin layer of DGT (diffusive gradients in thin films) devices greatly influences the measured metal accumulation, unless the complexes are either totally inert or perfectly labile. Lability criteria to predict the contribution of complexes in DGT measurements are reported. The key role of the resin thickness is highlighted. For complexes that are partially labile to the DGT measurement, their dissociation inside the resin domain is the main source of metal accumulation. This phenomenon explains the practical independence of the lability degree of a complex in a DGT device with respect to the ligand concentration. Transient DGT regimes, reflecting the times required to replenish the gel and resin domains up to the steady-state profile of the complex, are also examined. Low lability complexes (lability degree between 0.1 and 0.2) exhibit the longest transient regimes and therefore require longer deployment times to ensure accurate DGT measurements. PMID:22404162

Puy, Jaume; Uribe, Ramiro; Mongin, Sandrine; Galceran, Josep; Cecília, Joan; Levy, Jacqueline; Zhang, Hao; Davison, William

2012-06-28

134

Development of an Immunochromatographic Test Strip for Detection of Cholera Toxin  

PubMed Central

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.

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

2013-01-01

135

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

SciTech Connect

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.

Zhang, Rong-Guang; Westbrook, M.L. [Argonne National Lab., IL (United States); Maulik, P.R.; Reed, R.A.; Shipley, G. [Boston Univ., MA (United States). School of Medicine; Westbrook, E.M. [Argonne National Lab., IL (United States)]|[Northwestern Univ., Evanston, IL (United States); Scott, D.L.; Otwinowski, Z. [Yale Univ., New Haven, CT (United States)

1996-02-01

136

Development of an immunochromatographic test strip for detection of cholera toxin.  

PubMed

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

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

2013-01-01

137

Action of gravireceptors: lability hypothesis and model  

NASA Astrophysics Data System (ADS)

The plagiogravitropic growth stage usually occurring after gravitropic stimulation can be explained if 1) the liminal angle is interpreted as the angle to which the gravitropic response system tends to react after displacement and 2) the liminal angle is assumed to be labile, tending to equalise itself with the actual apex angle from the gravity vector. The process of equalisation may be interpreted as adaptation of gravity-receptors to exposure angle. Based on these assumptions, and adaptational model of the gravitropic response was proposed. It is in agreement with experimental data and describes adequately the plagiogravitropic growth stage occurring after gravitropic stimulation. It is supposed that such a mechanism acts in cooperation with others for initiation and maintenance of plagiogravitropic growth.

Sto?kus, A.

138

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...

139

The emotional lability questionnaire: a new measure of emotional lability in amyotrophic lateral sclerosis.  

PubMed

In an ALS Clinic, use of the Pathological Laughter and Crying Scale of Robinson et al. [Robinson RG, Parikh RM, Lipsey JR, Starkstein SE, Price TR. Pathological laughter and crying following stroke: validation of a measurement scale and double-blind treatment study. American Journal of Psychiatry 1993;150(2):286-293] revealed several problems: reliance on self-rating, insufficient period of assessment, inadequate exploration of 'appropriateness of emotion', lack of an item for abnormal smiling, amusement rather than happiness being the cause of laughter in ALS, and a frequency-based rating system. The necessary modifications produced a new Emotional Lability Questionnaire (ELQ) that was tested in 43 ALS patients and 43 healthy controls. The self-rated version of the ELQ was administered as a structured interview to each participant, and the independent-relationship between subscales of the ELQ for both versions, thus confirming its internal validity. Greater emotional lability appeared associated with pseudobulbar symptoms. The question why 14 patients rated themselves as severely labile in the crying domain alone and four in the laughter domain alone, required further study. PMID:10540003

Newsom-Davis, I C; Abrahams, S; Goldstein, L H; Leigh, P N

1999-10-31

140

Practical use of labile protein as an index of hair.  

PubMed

Because of small fluctuations, it is difficult to evaluate hair damage caused by bleaching using previously utilized hair damage indexes. Application of commercial bleaching products elevates partially extractable labile hair protein amounts in the range of 0.4-1.2 mg/g of hair. Within this range, the level of labile protein fluctuates greatly, depending on the extent of bleaching. In the current study, it was found that the effects of alkaline constituents and various peptides contained in bleaching lotions on hair damage could be evaluated by measuring labile protein amounts without employing harsher bleaching conditions. PMID:15645111

Inoue, Takafumi; Kizawa, Kenji; Ito, Mayumi; Shinkai, Masakazu; Iwamoto, Yoshimichi

2004-01-01

141

[Indications and utilization of labile blood products].  

PubMed

FUNDAMENTAL PRINCIPLES: Rigorous prescription of labile blood products is a fundamental step in assuring safe transfusion. The clinician must avoid all unnecessary transfusions and choose the most adapted blood product to meet the patient's clinical requirements. TRANSFUSION THERAPY: The patient's immunological situation, past history, prognosis, and potential need for future transfusions must be taken into account in a global approach aimed at determining which transfusion product is most adapted for each individual patient. PACKED RED CELLS: Packed red cells should be prescribed after evaluating the risk of tissue hypoxia in light of the patient's clinical situation. Restrictions on transfusion should be particularly drastic if the anemic state could respond to specific treatment (vitamin B12, iron, folic acid, erythropoietin). PLATELETS: There has been considerable development in platelet transfusion over the last few years, particularly in onco-hematology. Nevertheless, very few clinical studies are available for determining which cases require curative transfusion (solely in case of blood loss) and which situations require preventive transfusion (standard versus apheresis products). The platelet threshold indicating transfusion remains a subject of wide debate. FROZEN FRESH PLASMA: In France, regulatory indications for frozen fresh plasma were established by a ministerial decree and concern situations where a plasma fraction substitution product (medically derived blood product) cannot be prescribed. WHITE BLOOD CELL: The transfusion of this type of product should be reserved for clinical situations determined on a consensus basis between clinicians and hemobiologists. PMID:10442067

Lapierre, V; Hervé, P

142

Production of Acid Labile Alpha Interferon by AIDS Patients.  

National Technical Information Service (NTIS)

Acid Labile interferon (ALA-IFN) and IFN-omega (class II) share common antigenic determinants and similar biological activities, suggesting that they are related if not identical molecules. These results were further confirmed by the identification of IFN...

S. A. Serrate C. Dieffenbach

1989-01-01

143

40 CFR 725.421 - Introduced genetic material.  

Code of Federal Regulations, 2010 CFR

...Bacillus cereus Enterotoxin (diarrheagenic toxin, mouse lethal factor) Bordetella pertussis Adenylate cyclase (Heat-labile factor); Pertussigen (pertussis toxin, islet activating factor, histamine sensitizing factor, lymphocytosis...

2009-07-01

144

40 CFR 725.421 - Introduced genetic material.  

Code of Federal Regulations, 2013 CFR

...Bacillus cereus Enterotoxin (diarrheagenic toxin, mouse lethal factor) Bordetella pertussis Adenylate cyclase (Heat-labile factor); Pertussigen (pertussis toxin, islet activating factor, histamine sensitizing factor, lymphocytosis...

2013-07-01

145

40 CFR 725.421 - Introduced genetic material.  

Code of Federal Regulations, 2010 CFR

...Bacillus cereus Enterotoxin (diarrheagenic toxin, mouse lethal factor) Bordetella pertussis Adenylate cyclase (Heat-labile factor); Pertussigen (pertussis toxin, islet activating factor, histamine sensitizing factor, lymphocytosis...

2010-07-01

146

Detection of toxins produced by vibrio fluvialis.  

PubMed Central

The results of studies with cell-free extracts and culture supernatant fluids of Vibrio fluvialis (a recently recognized, potential enteric pathogen for humans) grown in the absence and presence of lincomycin indicated that the bacterium could produce (i) a factor which causes CHO cell elongation (CEF) similar to that elicited by V. cholerae enterotoxin and by the heat-labile enterotoxin of Escherichia coli, (ii) cytolysin(s) active against erythrocytes, (iii) nonhemolytic, CHO cell-killing factor(s), and (iv) protease(s) active against azocasein. The CEF was heat labile and ammonium sulfate precipitable, and it had an isoelectric point (estimated by sucrose density gradient electrofocusing) and molecular weight (estimated by gel filtration) of about 5.1 and 135,000, respectively. Images

Lockwood, D E; Kreger, A S; Richardson, S H

1982-01-01

147

Why is firefly oxyluciferin a notoriously labile substance?  

PubMed

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. PMID:24282138

Maltsev, Oleg V; Nath, Naba K; Naumov, Pan?e; Hintermann, Lukas

2014-01-13

148

*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...

149

The response of gross nitrogen mineralization to labile carbon inputs  

NASA Astrophysics Data System (ADS)

Input of labile carbon sources to forest soils commonly result in priming, i.e. an increase in the microbial decomposition of soil organic matter. Efforts aimed at quantifying the extent of priming have, to date, largely focused on soil organic matter decomposition manifested as soil respiration. Less is known about how gross nitrogen mineralization responds to input of labile carbon. It is often assumed that increased priming results in decreased soil carbon stocks. However, microbial mineralization of organic nitrogen into plant available forms is a major factor limiting primary production in forests. If increased decomposition of soil organic matter in response to labile carbon is accompanied by a concurrent increased nitrogen mineralization, this could result in elevated primary production and higher rates of plant derived organic matter input to soils. Therefore, in order to fully understand the effect of priming on net ecosystem exchange and soil carbon stocks, it is vital to consider if increased decomposition of soil organic matter caused by priming also results in increased nitrogen mineralization. Here I present the results from a series of experiments aimed at determining if, and to which extent, gross nitrogen mineralization is stimulated by input of labile carbon. The results suggest that it is by no means uncommon to find an increase in gross N mineralization rates in response to labile carbon inputs. The magnitude of the increase seems dependent on the nitrogen status of the soil, as well as the concentration and rate of labile carbon inputs. However, continuous input of labile carbon sources that also contains nitrogen, e.g. amino acids, seems to inhibit rather than increase the mineralization of organic nitrogen. These findings suggest that there is a potential for a positive feedback between priming and primary production that needs to be considered in order to fully understand the influence of priming on net ecosystem exchange and soil carbon stocks.

Bengtson, Per

2014-05-01

150

Bioterrorism: toxins as weapons.  

PubMed

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. PMID:22523138

Anderson, Peter D

2012-04-01

151

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

PubMed

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. PMID:24836503

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

2014-08-01

152

A Labile Pool of IQGAP1 Disassembles Endothelial Adherens Junctions  

PubMed Central

Adhesion molecules are known to play an important role in endothelial activation and angiogenesis. Here we determined the functional role of IQGAP1 in the regulation of endothelial adherens junctions. VE-cadherin is found to be associated with actin filaments and thus stable, but IQGAP1 at intercellular junctions is not bound to actin filaments and thus labile. Expression of GFP labeled VE-?-catenin is shown to increase the electrical resistance across HUVEC monolayers and diminishes endogenous labile IQGAP1 at the intercellular junctions. Knockdown of endogenous IQGAP1 enhances intercellular adhesion in HUVECs by increasing the association of VE-cadherin with P120 and ?-catenin. IQGAP1 knockdown also decreases the interaction of N-cadherin with P120 and ?-catenin. Together, these results suggest that a labile pool of IQGAP1 at intercellular junctions disassembles adherens junctions and thus impairs endothelial cell-cell adhesion.

Yuan, Zhiguo; Zhang, Wentao; Tan, Wen

2013-01-01

153

Labile trace elements in carbonaceous chondrites - A survey  

NASA Technical Reports Server (NTRS)

Data are presented on 14 trace elements, including Co, Au, Ga, Rb, Sb, Ag, Se, Cs, Te, Zn, Cd, Bi, Tl, and In (nearly all of which are moderately or highly labile in meteorites), obtained by radiochemical neutron activation analyses of 42 C2-C6 chondrites, all but three from Antarctica. The data indicate that carbonaceous chondrites of petrographic types 2-6 define compositional continua. It is suggested that carbonaceous C2-C6 chondrites may reflect a mixture of material that formed at low temperatures and that contained cosmic levels of highly labile elements, with material that was devoid of them.

Xiao, Xiaoyue; Lipschutz, Michael E.

1992-01-01

154

Nanoparticle-detained toxins for safe and effective vaccination  

NASA Astrophysics Data System (ADS)

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 ?-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.

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

2013-12-01

155

Nanoparticle-detained toxins for safe and effective vaccination  

PubMed Central

Toxoid vaccines—vaccines based on inactivated bacterial toxins— are routinely used to promote antitoxin immunity for the treatment and prevention of bacterial infections1–4. 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 ?-haemolysin, we demonstrate effective virulence neutralization via spontaneous particle entrapment. As compared to vaccination with heat-denatured toxin, mice vaccinated with the nanoparticle-detained toxin showed superior protective immunity against toxin adverse effects. We find that the non-disruptive detoxification approach benefited the immunogenicity and efficacy of toxoid vaccines. We anticipate the reported study to open new possibilities in the preparation of antitoxin vaccines against the many virulence factors that threaten public health.

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

2013-01-01

156

Cloning and sequencing of the genes encoding Escherichia coli cytolethal distending toxin.  

PubMed Central

Escherichia coli strains expressing cytolethal distending toxin (CDT) cause elongation of CHO cells at 24 h, followed by progressive cellular distention and death for up to 120 h. Similar distention and cytotoxicity are seen in HeLa, HEp-2, and, to a lesser extent, Vero cells. The initial elongation in CHO cells is indistinguishable from that caused by E. coli heat-labile toxin (LT). In contrast to those from LT strains, supernatants from these strains have no effect on Y-1 adrenal cells. TnphoA was introduced into CDT-positive E. coli E6468/62 (O86:H34), isolated from a child with diarrhea, and 13 CDT-negative transconjugants were identified. DNA probes constructed from DNA flanking the TnphoA insertion sites of CDT-negative mutants were used to identify a CDT-positive clone from an E6468/62 genomic library with a 5.5-kb insert. Exonuclease deletions were created and assayed in CHO cells. In this manner, a 2.3-kb CDT-active region was defined, and the nucleotide sequence was determined. Sequence analysis identified three open reading frames (ORFs), designated cdtA, cdtB, and cdtC. These contain 711, 819, and 570 bp, respectively, and encode polypeptides with predicted molecular masses of 25.5, 29.8, and 20.3 kDa, respectively. Each ORF has a putative signal sequence, and there are 4-bp overlaps between cdtA and cdtB and between cdtB and cdtC. The nucleotide and predicted amino acid sequences have no significant homology with those of any previously reported genes or proteins. By in vitro transcription-translation and an anti-alkaline phosphatase immunoblot, native proteins and/or fusion proteins corresponding to each ORF were identified. Images

Scott, D A; Kaper, J B

1994-01-01

157

Toxin-antitoxin systems  

PubMed Central

Toxin–antitoxin (TA) systems are small genetic elements composed of a toxin gene and its cognate antitoxin. The toxins of all known TA systems are proteins while the antitoxins are either proteins or non-coding RNAs. Based on the molecular nature of the antitoxin and its mode of interaction with the toxin the TA modules are currently grouped into five classes. In general, the toxin is more stable than the antitoxin but the latter is expressed to a higher level. If supply of the antitoxin stops, for instance under special growth conditions or by plasmid loss in case of plasmid encoded TA systems, the antitoxin is rapidly degraded and can no longer counteract the toxin. Consequently, the toxin becomes activated and can act on its cellular targets. Typically, TA toxins act on crucial cellular processes including translation, replication, cytoskeleton formation, membrane integrity, and cell wall biosynthesis. TA systems and their components are also versatile tools for a multitude of purposes in basic research and biotechnology. Currently, TA systems are frequently used for selection in cloning and for single protein expression in living bacterial cells. Since several TA toxins exhibit activity in yeast and mammalian cells they may be useful for applications in eukaryotic systems. TA modules are also considered as promising targets for the development of antibacterial drugs and their potential to combat viral infection may aid in controlling infectious diseases.

Unterholzner, Simon J; Poppenberger, Brigitte; Rozhon, Wilfried

2013-01-01

158

[Botulinum toxins for pain].  

PubMed

We review the evidence of botulinum toxins in the treatment of pain. Main indications of botulinum toxin treatment, dystonia and spasticity, involve pain. Increasing evidence suggests direct analgesic effects of botulinum. Botulinum inhibits release of pain mediators (substance P, CGRP, excitatory amino acids, ATP, noradrenaline). Clinical trials have consistently shown analgesic effect of botulinum toxin in post-stroke shoulder pain, bladder dysfunction, chronic migraine, neuropathic pain, bruxism and lateral epicondylitis. Other pain conditions have been studied with yet uncertain results. It seems that the number of patients who would benefit from botulinum toxin treatment will increase considerably in the future. PMID:22238920

Soinila, Seppo; Haanpää, Maija

2011-01-01

159

Leukocidal toxins of staphylococci.  

PubMed

Leukocidal toxins (synergohymenotropic toxin) are cytotoxins produced by staphylococci (S. aureus and S. intermedius) and consist of two separate components. The toxic effect depends on the synergistic action of two proteins. One of them belongs to class F (e.g. LukF-PV, LukF-R, LukF-I, LukM, HlgB) and the other, to class S (e.g. LukS-PV, LukS-R, LukS-I, HlgA, HlgC). Best known are the toxins produced by S. aureus: gamma-haemolysins, HlgA/HlgB and HlgC/HlgB and leukocidin Panton-Valentine, LukS-PV/LukF-PV (Luk-PV, PVL). Very few data are available concerning the relationship between the production of these toxins and the pathology of staphylococcal infections, because little is known about local and general effects of these leukocidal products in vivo. Frequent isolations of staphylococcal strains producing leukocidal toxins from necrotic skin lesions and furuncles suggest a role of these toxins in the virulence of staphylococci, at least in cutaneous infections. Recent data on mechanisms of cytotoxic effects of staphylococcal leukocidal toxins in vitro as well as effects of leukocidal toxins in vitro are discussed. Cell membranes appear to be a primary target for triggering the lysis of phagocytic cells caused by staphylococcal leukocidal toxins. PMID:10360319

Szmigielski, S; Prévost, G; Monteil, H; Colin, D A; Jeljaszewicz, J

1999-04-01

160

Neuropsychological Correlates of Emotional Lability in Children with ADHD  

ERIC Educational Resources Information Center

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…

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

161

How to Compute Labile Metal-Ligand Equilibria  

ERIC Educational Resources Information Center

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.

de Levie, Robert

2007-01-01

162

Contribution of partially labile complexes to the DGT metal flux.  

PubMed

Penetration of complexes into the resin layer can dramatically increase the contribution of complexes to the metal flux measured with a DGT (diffusive gradients in thin films) sensor, but equations to describe this phenomenon were not available. Here, simple approximate analytical expressions for the metal flux, the lability degree and the concentration profiles in a DGT experiment are reported. Together with the thickness of the reaction layer in the gel domain, the effective penetration distance into the resin layer that would be necessary for full dissociation of the complex (?(ML)) plays a key role in determining the metal flux. An increase in the resin-layer thickness (r) effectively increases the metal flux and the lability degree until r ? 3?(ML). For the usual DGT configuration, where the thickness of the gel layer exceeds that of the resin layer, the complex is labile if r > (D(ML)/k(d))½, where D(ML) is the diffusion coefficient of the metal complex and k(d) its dissociation rate constant. A general procedure for estimating the lability of any complex in a standard DGT configuration is provided. PMID:21608530

Uribe, Ramiro; Mongin, Sandrine; Puy, Jaume; Cecília, Joan; Galceran, Josep; Zhang, Hao; Davison, William

2011-06-15

163

Endogenous generation of hydralazine from labile hydralazine hydrazones.  

PubMed

The hypothesis that the pharmacologically active hydralazine hydrazones (HH) are endogenously hydrolyzed to parent hydralazine (H) was tested in a series of in vitro and in vivo systems. The stable hydrazones H alpha-ketoglutaric acid hydrazone and H pyruvic acid hydrazone did not hydrolyze to H in vitro (buffer or plasma), were inactive in vivo and did not generate urinary metabolites of parent H. By contrast, the labile HH, H acetaldehyde hydrazone and acetone hydrazone (HAH) generated H in vitro. H acetaldehyde hydrazone produced in vitro effects that were equipotent to the H concentration measured in the dose solutions. When administered to conscious rats and rabbits, the labile hydrazones reduced blood pressure. This effect was more gradual in onset than that of H. The hypotensive effects of HH were significantly greater than predicted by the amount of H contained in the dose solutions. Metabolic studies were conducted with the labile HH, HAH. After administration of HAH to rabbits, the proportional excretion of the urinary H metabolite, H pyruric acid hydrazone, was equal to that observed after the administration of H. We conclude that HH are inactive, except when hydrolyzed to H. The hydrolysis of certain HH, including HAH and H acetaldehyde hydrazone, in vivo may be nearly complete. Differences in the pharmacodynamic properties between labile HH and H may be related to the time course of generation of H, sequestration of hydrolysis in physiologically inactive sites or other unrecognized mechanisms. PMID:7086698

Clementi, W A; McNay, J L; Talseth, T; Haegele, K D; Ludden, T M; Musgrave, G E

1982-07-01

164

Comparative immunogenicities of Vi polysaccharide-protein conjugates composed of cholera toxin or its B subunit as a carrier bound to high- or lower-molecular-weight Vi.  

PubMed Central

The effect of molecular weight or size of the components on the immunogenicity of polysaccharide-protein conjugates prepared with the native Vi capsular polysaccharide (Vi) (approximately 3 x 10(3) kilodaltons) or lower-molecular-weight Vi (Vis; approximately 46 kilodaltons) abound to cholera toxin (CT) or to its B subunit (CTB) was studied. In mice, Vi-CT, Vi-CTB, and Vis-CTB elicited higher Vi antibody levels than the Vi alone (P less than 0.0001). Vi-CT and Vi-CTB were more immunogenic than Vis-CTB (P less than 0.01). CT or Vi-CT elicited higher levels of CT antibodies, as measured by enzyme-linked immunosorbent assay, than did CTB or Vi-CTB. In rhesus monkeys, the Vi conjugates elicited higher Vi antibody levels than the Vi alone (P less than 0.01). Vi-CTB elicited higher levels of Vi antibody after each injection than did Vis-CTB. Similar levels of CT antibodies, as measured by enzyme-linked immunosorbent assay, were elicited by all three conjugates. In contrast, Vi-CT elicited higher levels of neutralizing antibodies than Vi-CTB or Vis-CTB when either CT or the related heat-labile toxin of Escherichia coli was used as the antigen. These results indicate that the holotoxin and the native Vi provide the most immunogenic components for conjugates designed to induce both Vi and CT antibodies.

Szu, S C; Li, X R; Schneerson, R; Vickers, J H; Bryla, D; Robbins, J B

1989-01-01

165

Affective lability in patients with bipolar disorders is associated with high levels of childhood trauma.  

PubMed

This study aimed to investigate associations between a history of childhood trauma and levels of affective lability in bipolar patients compared to controls. Forty-two patients and 14 controls were assessed using the Affective Lability Scale (ALS) and the Childhood Trauma Questionnaire (CTQ). Affective Lability Score was significantly associated with scores on the Childhood Trauma Questionnaire. A multivariate regression model indicated a relationship between childhood trauma scores and differences in affective lability between patients and controls. PMID:24803185

Aas, Monica; Aminoff, Sofie R; Vik Lagerberg, Trine; Etain, Bruno; Agartz, Ingrid; Andreassen, Ole A; Melle, Ingrid

2014-08-15

166

Hot Stuff: Lability of Forest Floor DOM to Aerobic Degradation  

NASA Astrophysics Data System (ADS)

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, suggesting that the hydrophobics in peat do not inhibit aerobic degradation, but the humic acid does. These preliminary results suggest that lability to aerobic degradation of DOM extracted from forest floor organic matter differs somewhat with age but more with DOM character. These results indicate that the humic and hydrophobic fractions of DOM are more refractory to aerobic microbial activity, degrading more slowly than hydrophilic DOM. As well preliminary results suggest that refractory DOM may have an inhibitory effect on the degradation rate of the labile DOM.

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

2004-05-01

167

Effects of alpha and theta toxins from Clostridium perfringens on human polymorphonuclear leukocytes.  

PubMed

Two toxins, alpha (phospholipase C) and theta (oxygen-labile hemolysin), were purified from Clostridium perfringens type A and assayed for toxic effects on human polymorphonuclear leukocytes (PMNLs). Crude preparations containing both toxins totally inhibited chemotaxis and chemiluminescence responses of PMNLs and reduced PMNL viability. Purified alpha toxin did not alter PMNL viability, chemotactic responsiveness, or morphology but did enhance opsonized zymosan-induced PMNL chemiluminescence over a wide range of toxin concentrations. theta Toxin, at 12.5 hemolytic units (HU) per 10(5) PMNLs, reduced cell viability and induced marked PMNL morphological changes. Concentrations of theta toxin between 4 and 32 HU per 10(5) PMNLs inhibited PMNL chemiluminescence in a dose-dependent manner, whereas a lower concentration enhanced the PMNL chemiluminescent response to opsonized zymosan. Effects on chemotaxis were also dose dependent. Increased PMNL random migration was observed at a concentration of theta toxin of 0.06 HU per 2.5 X 10(5) PMNLs (P less than .05), whereas concentrations of greater than 0.08 HU per 2.5 X 10(5) PMNLs reduced both directed and random migration (P less than .05). PMID:2885383

Stevens, D L; Mitten, J; Henry, C

1987-08-01

168

The Ustilago maydis killer toxins  

Microsoft Academic Search

Killer toxins are small proteins secreted by a number of fungi that are lethal to susceptible cells (generally fungi of the same or related species). They bear some similarity to other families of protein toxins, which are ubiquitous in nature. The three known Ustilago maydis killer toxins typify, in many respects, the class of killer toxins. Two of them appear

Jeremy Bruenn

169

The epidemiology of travelers' diarrhea in Incirlik, Turkey: a region with a predominance of heat-stabile toxin producing enterotoxigenic Escherichia coli.  

PubMed

This study evaluated travelers' diarrhea among US military personnel on short-term deployment to Incirlik Air Base, Turkey, from June through September 2002. Upon reporting for care for travelers' diarrhea, subjects were enrolled into the study and completed a series of questionnaires and provided stool specimens for pathogen identification and antimicrobial susceptibility testing. Fifty-three percent of the 202 participating subjects had a pathogen isolated from their stool. Enterotoxigenic Escherichia coli (ETEC) was the predominant pathogen (41%), followed by Campylobacter spp. (12%). The most common ETEC phenotype recovered was stable toxin (ST) CS6 (47% of all ETEC). Most (91.1%) of the cases presented with water diarrhea regardless of isolated pathogen. However, there were some differences in nongastrointestinal symptoms among subjects with Campylobacter spp. All illnesses were well managed with antibiotics with or without loperamide with a median time to the last unformed stool of 9 h (interquartile range, 1-32 h). We found no food or environmental factors associated with a differential risk of infection with a specific pathogen. Travelers' diarrhea among a US military population in and around Incirlik, Turkey, can commonly be attributed to ETEC and Campylobacter spp. The high proportion of ST-only-producing CS6 ETEC in this region highlights the pathogen's worldwide diversity. Future studies of travelers' diarrhea in this population should adapt more novel microbiologic techniques such as polymerase chain reaction and enhanced culture methods to increase the likelihood of identifying pathogenic E. coli. PMID:19903582

Porter, Chad K; Riddle, Mark S; Tribble, David R; Putnam, Shannon D; Rockabrand, David M; Frenck, Robert W; Rozmajzl, Patrick; Kilbane, Edward; Fox, Ann; Ruck, Richard; Lim, Matthew; Johnston, James; Murphy, Emmett; Sanders, John W

2010-03-01

170

Anthrax toxin characterization.  

PubMed

The anthrax toxin comprises three proteins. When they work together, they can kill humans, especially after spores of the bacteria have been inhaled. One anthrax protein, called protective antigen (PA), chaperones the two other toxins into human or animal cells and shields them from the body's immune system. The second, lethal factor (LF), destroys the white blood cells that hosts send in defence. The third toxin molecule, edema factor (EF), hijacks the signaling system in the body. This disrupts the energy balance of cells and leads to them accumulating fluid and complete destroy of cells. PMID:12143109

Patocka, Jirí; Splino, Miroslav

2002-01-01

171

Evolutionary Lability of Integration in Cambrian Ptychoparioid Trilobites  

Microsoft Academic Search

Phenotypic integration can influence evolutionary rate and direction by channeling variation into few dimensions. The extent\\u000a to which that channeling serves as a constraint over macroevolutionary timescales is determined in part by the evolutionary\\u000a lability of phenotypic integration. Evolutionary change in patterns of pleiotropy, potentially reducing that constraint, is\\u000a thought to be more readily achieved when pleiotropy is structured by

Mark WebsterMiriam; Miriam L. Zelditch

2011-01-01

172

Labile complexes facilitate cadmium uptake by Caco-2 cells.  

PubMed

The Free Ion Activity Model (FIAM) predicts that metal uptake in biota is related to the free ion activity in the external solution and that metal complexes do not contribute. However, studies with plants have shown that labile metal complexes enhance metal bioavailability when the uptake is rate-limited by transport of the free ion in solution to the uptake site. Here, the role of labile complexes of Cd on metal bioavailability was assessed using Caco-2 cells, the cell model for intestinal absorption. At low Cd(2+) concentration (1 nM), the CdCl(n)(2-n) complexes contributed to the uptake almost to the same extent as the free ion. At large Cd(2+) concentration (10 ?M), the contribution of the complexes was much smaller. At constant Cd(2+) concentration, Cd intake in the cells from solutions containing synthetic ligands such as EDTA increased as the dissociation rate of the cadmium complexes increased, and correlated well with the Cd diffusion flux in solution measured with the Diffusive Gradient in Thin Films technique (DGT). The Cd intake fluxes in the cells were well predicted assuming that the specific uptake is limited by diffusion of the free Cd(2+) ion to the cell surface. Our results underline that speciation of Cd has a major effect on its uptake by intestinal cells, but the availability is not simply related to the free ion concentration. Labile complexes of Cd enhance metal bioavailability in these cells, likely by alleviating diffusive limitations. PMID:22503671

Verheyen, L; Degryse, F; Niewold, T; Smolders, E

2012-06-01

173

Labile disulfide bonds are common at the leucocyte cell surface  

PubMed Central

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.

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

2011-01-01

174

Transport of protein toxins into cells: pathways used by ricin, cholera toxin and Shiga toxin  

Microsoft Academic Search

Ricin, cholera, and Shiga toxin belong to a family of protein toxins that enter the cytosol to exert their action. Since all three toxins are routed from the cell surface through the Golgi apparatus and to the endoplasmic reticulum (ER) before translocation to the cytosol, the toxins are used to study different endocytic pathways as well as the retrograde transport

Kirsten Sandvig; Bo van Deurs

2002-01-01

175

Effects of Atrophic Rhinitis Induced by Pasteurella rnultocida Toxin on Heat Production and Activity of Pigs Kept Under Different Climatic Conditions  

Microsoft Academic Search

Effects of moderate, artificially in- duced atrophic rhinitis symptoms on level and changes in heat production and activity were deter- mined 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 treat- ments: challenged with 0 or 13

P. M. van Diemen; A. M. Henken; J. W. Schrama; H. A. Brandsma; M. W. A. Verstegent

2010-01-01

176

Koilocytes are enriched for alkaline-labile sites  

PubMed Central

This study investigated possible variations in the chromatin structure of koilocytes resulting from human papillomavirus (HPV) infection. Alkaline-labile sites (ALS) were detected with the DNA breakage detection–fluorescence in situ hybridization (DBD-FISH) technique using a whole human genome DNA probe obtained from individuals without koilocytosis. The variable levels of ALS present were measured quantitatively using image analysis after whole-genome DNA hybridization. A significant increase in the number of ALS was observed in koilocytes compared with normal cells. We demonstrated that the presence of ALS could be an indicator of chromatin change in koilocytes caused by HPV infection.

Cortes-Gutierrez, E.I.; Davila-Rodriguez, M.I.; Fernandez, J.L.; Lopez-Fernandez, C.; Gosalvez, J.

2010-01-01

177

Ciguatera Toxin Information Website  

NSDL National Science Digital Library

This website provides information about the marine toxin disease Ciguatera, which is caused by the consumption of fish that have accumulated ciguatoxin in their tissues. The toxin is produced by a microscopic dinoflagellate (Gambierdiscus toxicus) that lives on the surfaces of macroalgae in coral reef ecosystems. The dinoflagellates are inadvertently consumed by herbivorous fish during grazing and the toxins bioaccumulate in the food chain, attaining highest levels in carnivores. The site includes an introduction to ciguatera, information about the symptoms with links to reported cases and medical treatments, non-medical solutions, an education section, list of retailers, news releases, related links, and more. The site is published by ToxiTech, suppliers of Cigua-CheckÃ, which is a commercially available test kit for screening fish for ciguatoxin prior to consumption.

Toxitech; Oceanit

178

Acid-Labile Polyvinylamine Micro- and Nanogel Capsules  

PubMed Central

Hollow nanoparticles represent an emerging area of development for the encapsulation of active ingredients. Expanding the capabilities of these nanomaterials will require continued efforts to infill properties such as size control, biodegradability, and environmental responsiveness. Acid-labile poly(N-vinylformamide) (PNVF) nanocapsules were synthesized by free radical polymerization of N-vinylformamide on the surface of silica nanoparticles. Polymerization in the presence of a novel crosslinker that contains an acid-labile ketal facilitated stable etching of silica nanoparticle templates using sodium hydroxide and recovery of degradable PNVF nanocapsules. The formamido side group of PNVF was then hydrolyzed by extended exposure to sodium hydroxide to produce polyvinylamine (PVAm) micro- and nanocapsules. Both capsule types demonstrated an increasing dissolution rate as pH decreased. In addition, PVAm nanocapsules exhibited swelling in proportion to the relative charge density of the PVAm network (a function of the degree of formamide hydrolysis and pH), presumably due to the repulsion of positively charged amino groups within the elastic shell network. The synthetic approaches reported provide methods to endow nanocapsules with key attributes such as size control, pH sensitive degradation, swelling in response to pH, and amine functionality.

Shi, Lianjun; Berkland, Cory

2008-01-01

179

Killer toxin of Hanseniaspora uvarum  

Microsoft Academic Search

The yeast Hanseniaspora uvarum liberates a killer toxin lethal to sensitive strains of the species Saccharomyces cerevisiae. Secretion of this killer toxin was inhibited by tunicamycin, an inhibitor of N-glycosylation, although the mature killer protein did not show any detectable carbohydrate structures. Culture supernatants of the killer strain were concentrated by ultrafiltration and the extracellular killer toxin was precipitated with

F. Radler; M. J. Schmitt; Brigitte Meyer

1990-01-01

180

Toxin plasmids of Clostridium perfringens.  

PubMed

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

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

2013-06-01

181

Toxin Plasmids of Clostridium perfringens  

PubMed Central

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.

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

2013-01-01

182

Identification of Toxin A-Negative, Toxin B-Positive Clostridium difficile by PCR  

Microsoft Academic Search

Toxigenic strains of Clostridium difficile have been reported to produce both toxins A and B nearly always, and nontoxigenic strains have been reported to produce neither of these toxins. Recent studies indicate that it is not always true. We established a PCR assay to differentiate toxin A-negative, toxin B-positive (toxin A2, toxin B1) strains from both toxin-positive (toxin A1, toxin

HARU KATO; NAOKI KATO; KUNITOMO WATANABE; NAOICHI IWAI; HARUHI NAKAMURA; TOSHINOBU YAMAMOTO; KANZO SUZUKI; SHIN-MOO KIM; YUNSOP CHONG; EDDY BAGUS WASITO

1998-01-01

183

Immunological Interrelationships of Coliform Heat-Labile and Heat-Stable Enterotoxins.  

National Technical Information Service (NTIS)

The goal of these studies is the development of an immunization program to prevent acute diarrheal disease due to intestinal contamination of enterotoxigeneic strains of Escherichia coli. We have demonstrated (a) that the holotoxin is the most immunogenic...

F. A. Klipstein

1981-01-01

184

Immunological Interrelationships of Coliform Heat-Labile and Heat-Stable Enterotoxins.  

National Technical Information Service (NTIS)

Investigations conducted during the four period (1977 to 1981) of support by the USAMRDC have accomplished the following. (1) The enterotoxigenicity of certain coliform species which contaminate the small bowel in different diarrheal disorders has been es...

F. A. Klipstein

1981-01-01

185

[Advances in botulinum toxin applications].  

PubMed

Botulinum toxin type A is one of the seven serotype /A-G/ produced by the anerobic bacterium Clostridium botulinum. It is one of the most potent toxins available. Botulinum toxin binds to the motor nerve end-plate and prevents acetylcholin release, causing presynaptic neuromuscular blockade. The toxin is being increasingly used in the treatment of several form of disorders characterized by excessive or inappropriate muscle contraction, including stroke, cerebral palsy, multiple sclerosis. Botulinum toxin type A has brought a new approach to the effective treatment of dystonias. It has demonstrated additional analgesic effect. Among recently describes applications are the treatment of tics, tremors, hyperhydrosis, myoclonus, etc. PMID:10598494

Zaleski, P

1999-09-01

186

Uremia Toxin Assay.  

National Technical Information Service (NTIS)

The purpose of the research was to find assay systems which could be used in attempts to isolate the supposed toxins of uremia. A total of 14 enzyme assay systems were tested against fractions of plasma, dialysate, and urine from both uremic subjects unde...

C. E. Cook

1970-01-01

187

Diffusion of Botulinum Toxins  

PubMed Central

Background It is generally agreed that diffusion of botulinum toxin occurs, but the extent of the spread and its clinical importance are disputed. Many factors have been suggested to play a role but which have the most clinical relevance is a subject of much discussion. Methods This review discusses the variables affecting diffusion, including protein composition and molecular size as well as injection factors (e.g., volume, dose, injection method). It also discusses data on diffusion from comparative studies in animal models and human clinical trials that illustrate differences between the available botulinum toxin products (onabotulinumtoxinA, abobotulinumtoxinA, incobotulinumtoxinA, and rimabotulinumtoxinB). Results Neither molecular weight nor the presence of complexing proteins appears to affect diffusion; however, injection volume, concentration, and dose all play roles and are modifiable. Both animal and human studies show that botulinum toxin products are not interchangeable, and that some products are associated with greater diffusion and higher rates of diffusion-related adverse events than others. Discussion Each of the botulinum toxins is a unique pharmacologic entity. A working knowledge of the different serotypes is essential to avoid unwanted diffusion-related adverse events. In addition, clinicians should be aware that the factors influencing diffusion may range from properties intrinsic to the drug to accurate muscle selection as well as dilution, volume, and dose injected.

Brodsky, Matthew A.; Swope, David M.; Grimes, David

2012-01-01

188

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 ...

189

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 ...

190

[Cytolethal distending toxins].  

PubMed

Cytolethal distending toxins (CDT) are intracellularly acting proteins which interfere with the eukaryotic cell cycle. They are produced by Gram-negative bacteria with affinity to mucocutaneous surfaces and could play a role in the pathogenesis of various mammalian diseases. The functional toxin is composed of three proteins: CdtB entering the nucleus and by its nuclease activity inducing nuclear fragmentation and chromatin disintegration, CdtA, and CdtC, the two latter being responsible for toxin attachment to the surface of the target cell. Cytotoxic effect of CDT leads to the cell cycle arrest before the cell enters mitosis and to further changes (cell distension and death, apoptosis) depending on the cell type. Thus, CDT may function as a virulence factor in pathogenic bacteria that produce it and thus may contribute to the initiation of certain diseases. Most important are inflammatory bowel diseases caused by intestinal bacteria, periodontitis with Aggregatibacter actinomycetemcomitans as the aetiologic agent and ulcus molle where Haemophilus ducreyi is the causative agent. Keywords: cytolethal distending toxin - CDT - virulence factor - Gram-negative bacteria. PMID:25025680

Curová, K; Kme?ová, M; Siegfried, L

2014-01-01

191

The role of labile sulfur compounds in thermochemical sulfate reduction  

NASA Astrophysics Data System (ADS)

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 CaSO 4 in the presence of reduced sulfur (e.g. H 2S, 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 H 2S 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 H 2S 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 H 2S. Second, we considered the generation of olefines in association with the elimination of H 2S 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 organic LSC creates free-radicals that in turn might initiate a radical chain-reaction that creates more reactive species. Experiments involving radical initiators, such as diethyldisulfide and benzyldisulfide, did not show an increase in reactivity compared to 1-pentanethiol. Therefore, we conclude that none of these can sufficiently explain our observations of the initial stages of TSR; they may, however, be important in the later stages. In order to gain greater insight into the potential mechanism for the observed reactivity of these organic sulfur compounds during TSR, we applied density functional theory-based molecular modeling techniques to our system. The results of these calculations indicate that 1-pentanethiol or its thermal degradation products may directly react with sulfate and reduce the activation energy required to rupture the first S-O bond through the formation of a sulfate ester. This study demonstrates the importance of labile sulfur compounds in reducing the onset timing and temperature of TSR. It is therefore essential that labile sulfur concentrations are taken into consideration when trying to make accurate predictions of TSR kinetics and the potential for H 2S accumulation in petroleum reservoirs.

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

2008-06-01

192

The role of labile sulfur compounds in thermochemical sulfate reduction  

USGS Publications Warehouse

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 organic LSC creates free-radicals that in turn might initiate a radical chain-reaction that creates more reactive species. Experiments involving radical initiators, such as diethyldisulfide and benzyldisulfide, did not show an increase in reactivity compared to 1-pentanethiol. Therefore, we conclude that none of these can sufficiently explain our observations of the initial stages of TSR; they may, however, be important in the later stages. In order to gain greater insight into the potential mechanism for the observed reactivity of these organic sulfur compounds during TSR, we applied density functional theory-based molecular modeling techniques to our system. The results of these calculations indicate that 1-pentanethiol or its thermal degradation products may directly react with sulfate and reduce the activation energy required to rupture the first S-O bond through the formation of a sulfate ester. This study demonstrates the importance of labile sulfur compounds in reducing the onset timing and temperature of TSR. It is therefore essential that labile sulfur concentrations are taken into consideration when trying to make accurate predictions of TSR kinetics and the potential for H2S accumulation in petroleum reservoirs. ?? 2008.

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

2008-01-01

193

Chemical leaching methods and measurements of marine labile particulate Fe  

NASA Astrophysics Data System (ADS)

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 (<0.4?m) has traditionally been considered the most biologically accessible form, however, the particulate phase (>0.4?m) 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. ?56Fe 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 ?56Fe of this iron. Isotopically lighter ?56Fe values were associated with smaller amounts of leached Fe whereas isotopically heavier ?56Fe 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. To explore the first hypothesis, we modeled dissolution of Fe from particles assuming two separate pools, labile and refractory. The model produces a good fit to the data assuming 3mg/g of a labile Fe pool with ?56Fe = -0.9‰ and a refractory Fe pool with ?56Fe = +0.1‰. If the second hypothesis is true, and there is a kinetic isotope effect during dissolution, the similar relationship between amount of Fe leached and ?56Fe for both organic and mineral acids suggests that Fe is leached from particles via proton-promoted dissolution. Several of these leaching techniques will be employed on sediment trap material from the Cariaco Basin to further investigate the relationship between ?56Fe and the labile, bioavailable fraction of iron particles. A leach or series of leaches will be chosen to provide the most useful information about the bioavailability of iron from particles, and they will be applied to filtered particle samples from portions of the US GEOTRACES A10 (North Atlantic) transect. ?56Fe values from particulate material in these regions will provide a better understanding of the sources of particulate iron to the ocean, and may help to trace how particulate iron is involved in global biogeochemical cycles.

Revels, B. N.; John, S.

2012-12-01

194

A downscaled practical measure of mood lability as a screening tool for bipolar II  

Microsoft Academic Search

Background: Current data indicate a strong association between Cyclothymic temperament (and its more ultradian counterpart of mood lability) and Bipolar II (BPII). Administration of elaborate measures of temperament are cumbersome in routine practice. Accordingly, the aim of the present analyses was to test if a practical measure of mood lability was unique to BPII, in comparison with major depressive disorder

Franco Benazzi; Hagop S. Akiskal

2005-01-01

195

The Renal Tubular Handling of Aldosterone and Its Acid-Labile Conjugate.  

National Technical Information Service (NTIS)

Stop-flow studies using infusions of aldosterone-3H or its 3H acid-labile conjugate were done on five rhesus monkeys. The aldosterone-3H urine-to-plasma (U/P) ratio decreased in the same distal urine samples as sodium. The 3H acid-labile conjugate U/P-to-...

M. T. Scurry L. Shear K. G. Barry

1967-01-01

196

Mzm1 Influences a Labile Pool of Mitochondrial Zinc Important for Respiratory Function*  

PubMed Central

Zinc is essential for function of mitochondria as a cofactor for several matrix zinc metalloproteins. We demonstrate that a labile cationic zinc component of low molecular mass exists in the yeast mitochondrial matrix. This zinc pool is homeostatically regulated in response to the cellular zinc status. This pool of zinc is functionally important because matrix targeting of a cytosolic zinc-binding protein reduces the level of labile zinc and interferes with mitochondrial respiratory function. We identified a series of proteins that modulate the matrix zinc pool, one of which is a novel conserved mitochondrial protein designated Mzm1. Mutant mzm1? cells have reduced total and labile mitochondrial zinc, and these cells are hypersensitive to perturbations of the labile pool. In addition, mzm1? cells have a destabilized cytochrome c reductase (Complex III) without any effects on Complexes IV or V. Thus, we have established that a link exists between Complex III integrity and the labile mitochondrial zinc pool.

Atkinson, Aaron; Khalimonchuk, Oleh; Smith, Pamela; Sabic, Hana; Eide, David; Winge, Dennis R.

2010-01-01

197

Shiga toxin-associated hemolytic uremic syndrome: interleukin-1 beta enhancement of Shiga toxin cytotoxicity toward human vascular endothelial cells in vitro.  

PubMed Central

Development of hemolytic uremic syndrome (HUS) after infection by Shigella dysenteriae 1 or enterohemorrhagic Escherichia coli has been associated with the production of Shiga toxins (verotoxins). The putative target of Shiga toxins in HUS is the renal microvascular endothelium. This report shows that preincubation of human umbilical vein endothelial cells (HUVEC) with interleukin-1 beta (IL-1 beta) enhances the cytotoxic potency of Shiga toxin toward HUVEC. A preincubation of HUVEC with IL-1 beta is required for sensitization of HUVEC to Shiga toxin. Sensitization of HUVEC to Shiga toxin is IL-1 beta dose dependent. Development of the IL-1 beta response is time dependent, beginning within 2 h of IL-1 beta preincubation and increasing over the next 24 h. That these responses were due to IL-1 beta was demonstrated by heat inactivation of IL-1 beta, by neutralization of IL-1 beta by specific antibody, and by the ability of an IL-1 beta receptor antagonist to inhibit the effect of IL-1 beta. Shiga toxin-related inhibition of HUVEC protein synthesis preceded loss of cell viability. IL-1 beta incubation with HUVEC induced the receptor for Shiga toxin, globotriaosylceramide. Lipopolysaccharide included during IL-1 beta preincubation with HUVEC increased sensitivity to Shiga toxin in an additive manner. We conclude that IL-1 beta may induce Shiga toxin sensitivity in endothelial cells and contribute to the development of HUS.

Kaye, S A; Louise, C B; Boyd, B; Lingwood, C A; Obrig, T G

1993-01-01

198

Expression of the cholera toxin B subunit (CT-B) in maize seeds and a combined mucosal treatment against cholera and traveler's diarrhea.  

PubMed

The non-toxic B subunit (CT-B) of cholera toxin from Vibrio cholerae is a strong immunogen and amplifies the immune reaction to conjugated antigens. In this work, a synthetic gene encoding for CT-B was expressed under control of a ?-zein promoter in maize seeds. Levels of CT-B in maize plants were determined via ganglioside dependent ELISA. The highest expression level recorded in T(1) generation seeds was 0.0014% of total aqueous soluble protein (TASP). Expression level of the same event in the T(2) generation was significantly increased to 0.0197% of TASP. Immunogenicity of maize derived CT-B was evaluated in mice with an oral immunization trial. Anti-CTB IgG and anti-CTB IgA were detected in the sera and fecal samples of the orally immunized mice, respectively. The mice were protected against holotoxin challenge with CT. An additional group of mice was administrated with an equal amount (5 ?g per dose each) of mixed maize-derived CT-B and LT-B (B subunit of E. coli heat labile toxin). In the sera and fecal samples obtained from this group, the specific antibody levels were enhanced compared to either the same or a higher amount of CT-B alone. These results suggest that a synergistic action may be achieved using a CT-B and LT-B mixture that can lead to a more efficacious combined vaccine to target diarrhea induced by both cholera and enterotoxigenic strains of Escherichia coli. PMID:21938449

Karaman, S; Cunnick, J; Wang, K

2012-03-01

199

Lability of trace metals in submerged soils: a column study  

NASA Astrophysics Data System (ADS)

The reduction of Fe (III) and Mn (IV) and the decomposition of organic matter exert a great influence on the biogeochemical cycles of many trace metals and nutrients in the environment. In the particular case of intermittently submerged soils, metals associated with Fe and Mn oxides become readily available due to the reductive dissolution of Fe and Mn oxides. The effects of oxido-reductive conditions on the release of Cu and Zn from heavy metal contaminated soils and the changes in their chemical speciation were studied. Column experiments were performed, using Rhizon soil moisture samplers inserted at different heights to monitor the mobility and transport of metals in the submerged soil samples. Cu was released in solution immediately, in the first red-ox cycle, either due to the solubilization of Fe and Mn oxides, or to the oxidation of organic matter with which Cu is commonly complexed, or both. During the following reductive half-cycles, the amount of Cu extracted from the soil solution decreased. However, the concentration of Cu in the solution leached from the column, which was percolated in aerobic conditions, increased. Since in the successive red-ox cycles the Eh decreases faster and to lower values, it is possible that Cu might have been removed from pore water by sulfide precipitation during the anaerobic half-cycle and released during the aerobic half-cycle, due to the oxidation of sulfides to sulfates. The release of Zn was similar to the dissolution of Fe and Mn oxyhydroxydes, and the amount extracted by Rhizon and by leaching increased during the four red-ox cycles. The chemical fractionation of the soils was also studied and the results showed that the alternate oxidative-reductive conditions cause, in general, an increase in the lability of trace metals. While Zn speciation suffers little change, Cu showed a much higher exchangeable fraction in the submerged soils, as compared to the initial, not submerged ones. The results of this study indicate that intermittent submergence of contaminated soils not only causes the release of trace metals previously bound to Fe and Mn oxides and to organic matter, but also leads to an increase in their lability, rending them more readily available to be released into the environment.

Nimirciag, Ramona; Ajmone-Marsan, Franco

2013-04-01

200

Evolutionarily labile responses to a signal of aggressive intent.  

PubMed Central

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.

Moretz, Jason A; Morris, Molly R

2003-01-01

201

Continuous flow analysis of labile iron in ice-cores.  

PubMed

The important active and passive role of mineral dust aerosol in the climate and the global carbon cycle over the last glacial/interglacial cycles has been recognized. However, little data on the most important aeolian dust-derived biological micronutrient, iron (Fe), has so far been available from ice-cores from Greenland or Antarctica. Furthermore, Fe deposition reconstructions derived from the palaeoproxies particulate dust and calcium differ significantly from the Fe flux data available. The ability to measure high temporal resolution Fe data in polar ice-cores is crucial for the study of the timing and magnitude of relationships between geochemical events and biological responses in the open ocean. This work adapts an existing flow injection analysis (FIA) methodology for low-level trace Fe determinations with an existing glaciochemical analysis system, continuous flow analysis (CFA) of ice-cores. Fe-induced oxidation of N,N'-dimethyl-p-pheylenediamine (DPD) is used to quantify the biologically more important and easily leachable Fe fraction released in a controlled digestion step at pH ~1.0. The developed method was successfully applied to the determination of labile Fe in ice-core samples collected from the Antarctic Byrd ice-core and the Greenland Ice-Core Project (GRIP) ice-core. PMID:23594184

Hiscock, William T; Fischer, Hubertus; Bigler, Matthias; Gfeller, Gideon; Leuenberger, Daiana; Mini, Olivia

2013-05-01

202

Anticariogenic and phytochemical evaluation of Eucalyptus globules Labill.  

PubMed Central

In the present study, in vitro anticariogenic potential of ethyl acetate, hexane and methanol and aqueous extracts of plant leaves of Eucalyptus globules Labill. were evaluated by using four cariogenic bacteria, Lactobacillus acidophilus, Lactobacillus casei, Staphylococcus aureus and Streptococcus mutans. Agar well diffusion method and minimum inhibitory concentration (MIC) were used for this purpose. The ethyl acetate extracted fraction of plant leaves showed good inhibitory effects against all selected bacteria. In Eucalyptus globules, hexane and ethyl acetate extracts found highly effective against, Lactobacillus acidophilus with MIC value of 0.031 and 0.062 mg/mL, respectively. Qualitative phytochemical investigation of above extracts showed the presence of alkaloids, phenolic compounds, steroids, cardiac glycosides and terpenes. Based on the MIC value and bioautography, ethyl acetate of plant leaf was selected for further study. Further investigation on the structure elucidation of the bioactive compound using IR, GC-MS and NMR techniques revealed the presence of alpha-farnesene, a sesquiterpene. Eucalyptus globules plant leaf extracts have great potential as anticariogenic agents that may be useful in the treatment of oral disease.

Ishnava, Kalpesh B.; Chauhan, Jenabhai B.; Barad, Mahesh B.

2012-01-01

203

Structural Lability of Barley Stripe Mosaic Virus Virions  

PubMed Central

Virions of Barley stripe mosaic virus (BSMV) were neglected for more than thirty years after their basic properties were determined. In this paper, the physicochemical characteristics of BSMV virions and virion-derived viral capsid protein (CP) were analyzed, namely, the absorption and intrinsic fluorescence spectra, circular dichroism spectra, differential scanning calorimetry curves, and size distributions by dynamic laser light scattering. The structural properties of BSMV virions proved to be intermediate between those of Tobacco mosaic virus (TMV), a well-characterized virus with rigid rod-shaped virions, and flexuous filamentous plant viruses. The BSMV virions were found to be considerably more labile than expected from their rod-like morphology and a distant sequence relation of the BSMV and TMV CPs. The circular dichroism spectra of BSMV CP subunits incorporated into the virions, but not subunits of free CP, demonstrated a significant proportion of beta-structure elements, which were proposed to be localized mostly in the protein regions exposed on the virion outer surface. These beta-structure elements likely formed during virion assembly can comprise the N- and C-terminal protein regions unstructured in the non-virion CP and can mediate inter-subunit interactions. Based on computer-assisted structure modeling, a model for BSMV CP subunit structural fold compliant with the available experimental data was proposed.

Semenyuk, Pavel I.; Abashkin, Dmitry A.; Kalinina, Natalya O.; Arutyunyan, Alexsandr M.; Solovyev, Andrey G.; Dobrov, Eugeny N.

2013-01-01

204

Anticariogenic and phytochemical evaluation of Eucalyptus globules Labill.  

PubMed

In the present study, in vitro anticariogenic potential of ethyl acetate, hexane and methanol and aqueous extracts of plant leaves of Eucalyptus globules Labill. were evaluated by using four cariogenic bacteria, Lactobacillus acidophilus, Lactobacillus casei, Staphylococcus aureus and Streptococcus mutans. Agar well diffusion method and minimum inhibitory concentration (MIC) were used for this purpose. The ethyl acetate extracted fraction of plant leaves showed good inhibitory effects against all selected bacteria. In Eucalyptus globules, hexane and ethyl acetate extracts found highly effective against, Lactobacillus acidophilus with MIC value of 0.031 and 0.062 mg/mL, respectively. Qualitative phytochemical investigation of above extracts showed the presence of alkaloids, phenolic compounds, steroids, cardiac glycosides and terpenes. Based on the MIC value and bioautography, ethyl acetate of plant leaf was selected for further study. Further investigation on the structure elucidation of the bioactive compound using IR, GC-MS and NMR techniques revealed the presence of alpha-farnesene, a sesquiterpene. Eucalyptus globules plant leaf extracts have great potential as anticariogenic agents that may be useful in the treatment of oral disease. PMID:23961222

Ishnava, Kalpesh B; Chauhan, Jenabhai B; Barad, Mahesh B

2013-01-01

205

Capturing Labile Sulfenamide and Sulfinamide Serum Albumin Adducts of Carcinogenic Arylamines by Chemical Oxidation  

PubMed Central

Aromatic amines and heterocyclic aromatic amines (HAAs) are a class of structurally related carcinogens that are formed during the combustion of tobacco or during the high temperature cooking of meats. These procarcinogens undergo metabolic activation by N-oxidation of the exocyclic amine group to produce N-hydroxylated metabolites, which are critical intermediates implicated in toxicity and DNA damage. The arylhydroxylamines and their oxidized arylnitroso derivatives can also react with cysteine (Cys) residues of glutathione or proteins to form, respectively, sulfenamide and sulfinamide adducts. However, sulfur-nitrogen linked adducted proteins are often difficult to detect because they are unstable and undergo hydrolysis during proteolytic digestion. Synthetic N-oxidized intermediates of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a carcinogenic HAA produced in cooked meats, and 4-aminobiphenyl, a carcinogenic aromatic amine present in tobacco smoke were reacted with human serum albumin (SA) and formed labile sulfenamide or sulfinamide adducts at the Cys34 residue. Oxidation of the carcinogen-modified SA with m-chloroperoxybenzoic acid (m-CPBA) produced the arylsulfonamide adducts, which were stable to heat and the chemical reduction conditions employed to denature SA. The sulfonamide adducts of PhIP and 4-ABP were identified, by liquid chromatography/mass spectrometry, in proteolytic digests of denatured SA. Thus, selective oxidation of arylamine-modified SA produces stable arylsulfonamide-SA adducts, which may serve as biomarkers of these tobacco and dietary carcinogens.

Peng, Lijuan; Turesky, Robert J.

2013-01-01

206

Bacterial insecticidal toxins.  

PubMed

Over the years it has been important for humans to control the populations of harmful insects and insecticides have been used for this purpose in agricultural and horticultural sectors. Synthetic insecticides, owing to their various side effects, have been widely replaced by biological insecticides. In this review we attempt to describe three bacterial species that are known to produce insecticidal toxins of tremendous biotechnological, agricultural, and economic importance. Bacillus thuringiensis (BT) accounts for 90% of the bioinsecticide market and it produces insecticidal toxins referred to as delta endotoxins. The other two bacteria belong to the genera Photorhabdus and Xenorhabdus, which are symbiotically associated with entomopathogenic nematodes of the families Heterorhabditidae and Steinernematidae respectively. Whereas, Xenorhabdus and Photorhabdus exist in a mutualistic association with the entomopathogenic nematodes, BT act alone. BT formulations are widely used in the field against insects; however, over the years there has been a gradual development of insect resistance against BT toxins. No resistance against Xenorhabdus or Photorhabdus has been reported to date. More recently BT transgenic crops have been prepared; however, there are growing concerns about the safety of these genetically modified crops. Nematodal formulations are also used in the field to curb harmful insect populations. Resistance development to entomopathogenic nematodes is unlikely due to the physical macroscopic nature of infection. Xenorhabdus and Photorhabdus transgenes have not yet been prepared; but are predicted to be available in the near future. In this review we start with an overview of the synthetic insecticides and then discuss Bacillus thuringiensis, Xenorhabdus nematophilus, and Photorhabdus luminescens in greater detail. PMID:15116762

Chattopadhyay, Abanti; Bhatnagar, N B; Bhatnagar, Rakesh

2004-01-01

207

The toxins of Cyanobacteria.  

PubMed

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. PMID:11488138

Patocka, J

2001-01-01

208

Lymphocyte receptors for pertussis toxin  

SciTech Connect

We have investigated human T-lymphocyte receptors for pertussis toxin by affinity isolation and photoaffinity labeling procedures. T lymphocytes were obtained from peripheral human blood, surface iodinated, and solubilized in Triton X-100. The iodinated mixture was then passed through pertussis toxin-agarose, and the fractions were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Autoradiography of the fixed, dried gels revealed several bands in the pertussis toxin-bound fraction that were not observed in fractions obtained from histone or fetuin-agarose. Further investigations employed a photoaffinity labeling reagent, sulfosuccinimidyl 2-(p-azido-salicylamido)-1,3'-dithiopropionate, to identify pertussis toxin receptors in freshly isolated peripheral blood monocytic cells, T lymphocytes, and Jurkat cells. In all three cell systems, the pertussis toxin affinity probe specifically labeled a single protein species with an apparent molecular weight of 70,000 that was not observed when the procedure was performed in the presence of excess unmodified pertussis toxin. A protein comparable in molecular weight to the one detected by the photoaffinity labeling technique was also observed among the species that bound to pertussis toxin-agarose. The results suggest that pertussis toxin may bind to a 70,000-Da receptor in human T lymphocytes.

Clark, C.G.; Armstrong, G.D. (Univ. of Alberta, Edmonton (Canada))

1990-12-01

209

Botulinum toxin: Bioweapon & magic drug  

PubMed Central

Botulinum neurotoxins, causative agents of botulism in humans, are produced by Clostridium botulinum, an anaerobic spore-former Gram positive bacillus. Botulinum neurotoxin poses a major bioweapon threat because of its extreme potency and lethality; its ease of production, transport, and misuse; and the need for prolonged intensive care among affected persons. A single gram of crystalline toxin, evenly dispersed and inhaled, can kill more than one million people. The basis of the phenomenal potency of botulinum toxin is enzymatic; the toxin is a zinc proteinase that cleaves neuronal vesicle associated proteins responsible for acetylcholine release into the neuromuscular junction. As a military or terrorist weapon, botulinum toxin could be disseminated via aerosol or by contamination of water or food supplies, causing widespread casualties. A fascinating aspect of botulinum toxin research in recent years has been development of the most potent toxin into a molecule of significant therapeutic utility. It is the first biological toxin which is licensed for treatment of human diseases. In the late 1980s, Canada approved use of the toxin to treat strabismus, in 2001 in the removal of facial wrinkles and in 2002, the FDA in the United States followed suit. The present review focuses on both warfare potential and medical uses of botulinum neurotoxin.

Dhaked, Ram Kumar; Singh, Manglesh Kumar; Singh, Padma; Gupta, Pallavi

2010-01-01

210

TOXINS FROM CYANOBACTERIA IN WATER  

EPA Science Inventory

This project is part of a larger U. S. Environmental Protection Agency (EPA) effort, which includes the Office of Water, to investigate algal toxins in surface water supplies and drinking water. Toxins produced by cyanobacteria (blue-green algae) are among the most potent known ...

211

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

SciTech Connect

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.

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

1982-04-01

212

Toxin production by Campylobacter spp.  

PubMed Central

Of all the virulence factors that were proposed for Campylobacter jejuni and related species to cause disease in humans, the discovery of toxin production was the most promising but led to a rather confusing and even disappointing stream of data. The discussion of whether proteinaceous exotoxins are relevant in disease remains open. One important reason for this lack of consensus is the anecdotal nature of the literature reports. To provide a basis for an unbiased opinion, this review compiles all described exotoxins, compares their reported properties, and provides a summary of animal model studies and clinical data. The toxins are divided into enterotoxins and cytotoxins and are sorted according to their biochemical properties. Since many Campylobacter toxins have been compared with toxins of other species, some key examples of the latter are also discussed. Future directions of toxin research that appear promising are defined.

Wassenaar, T M

1997-01-01

213

Toxin-induced hepatic injury.  

PubMed

Toxins such as pharmaceuticals, herbals, foods, and supplements may lead to hepatic damage. This damage may range from nonspecific symptoms in the setting of liver test abnormalities to acute hepatic failure. The majority of severe cases of toxin-induced hepatic injury are caused by acetaminophen and ethanol. The most important step in the patient evaluation is to gather an extensive history that includes toxin exposure and exclude common causes of liver dysfunction. Patients whose hepatic dysfunction progresses to acute liver failure may benefit from transfer to a transplant service for further management. Currently, the mainstay in management for most exposures is discontinuing the offending agent. This manuscript will review the incidence, pathophysiology, diagnosis and management of the different forms of toxin-induced hepatic injury and exam in-depth the most common hepatic toxins. PMID:24275171

Lopez, Annette M; Hendrickson, Robert G

2014-02-01

214

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...

215

Phosphorus Loading from the Redwood River Basin: Fractionation of Labile and Refractory Components.  

National Technical Information Service (NTIS)

The purpose of this demonstration effort was to quantify loading of labile and refractory phosphorus fractions from the agriculturally dominated Redwood River Basin, which drains into the Minnesota River. This information will be important for future cali...

W. F. James J. W. Barko H. L. Eakin

2001-01-01

216

Stereochemical lability of azatitanacyclopropanes: dynamic kinetic resolution in reductive cross-coupling reactions with allylic alcohols.  

PubMed

Azatitanacyclopropanes (titanaziridines) are shown to be stereochemically labile under reaction conditions for reductive cross-coupling. This fundamental property has been employed to realize highly selective asymmetric coupling reactions with allylic alcohols that proceed by dynamic kinetic resolution. PMID:23963189

Yang, Dexi; Micalizio, Glenn C

2013-10-01

217

Binding of ATP by pertussis toxin and isolated toxin subunits  

SciTech Connect

The binding of ATP to pertussis toxin and its components, the A subunit and B oligomer, was investigated. Whereas, radiolabeled ATP bound to the B oligomer and pertussis toxin, no binding to the A subunit was observed. The binding of ({sup 3}H)ATP to pertussis toxin and the B oligomer was inhibited by nucleotides. The relative effectiveness of the nucleotides was shown to be ATP > GTP > CTP > TTP for pertussis toxin and ATP > GTP > TTP > CTP for the B oligomer. Phosphate ions inhibited the binding of ({sup 3}H)ATP to pertussis toxin in a competitive manner; however, the presence of phosphate ions was essential for binding of ATP to the B oligomer. The toxin substrate, NAD, did not affect the binding of ({sup 3}H)ATP to pertussis toxin, although the glycoprotein fetuin significantly decreased binding. These results suggest that the binding site for ATP is located on the B oligomer and is distinct from the enzymatically active site but may be located near the eukaryotic receptor binding site.

Hausman, S.Z.; Manclark, C.R.; Burns, D.L. (Center for Biologics Evaluation and Research, Bethesda, MD (USA))

1990-07-03

218

The labile brain. I. Neuronal transients and nonlinear coupling.  

PubMed Central

In this, the first of three papers, the nature of, and motivation for, neuronal transients is described in relation to characterizing brain dynamics. This paper deals with some basic aspects of neuronal dynamics, interactions, coupling and implicit neuronal codes. The second paper develops neuronal transients and nonlinear coupling in the context of dynamic instability and complexity, and suggests that instability or lability is necessary for adaptive self-organization. The final paper addresses the role of neuronal transients through information theory and the emergence of spatio-temporal receptive fields and functional specialization. By considering the brain as an ensemble of connected dynamic systems one can show that a sufficient description of neuronal dynamics comprises neuronal activity at a particular time and its recent history This history constitutes a neuronal transient. As such, transients represent a fundamental metric of neuronal interactions and, implicitly, a code employed in the functional integration of brain systems. The nature of transients, expressed conjointly in distinct neuronal populations, reflects the underlying coupling among populations. This coupling may be synchronous (and possibly oscillatory) or asynchronous. A critical distinction between synchronous and asynchronous coupling is that the former is essentially linear and the latter is nonlinear. The nonlinear nature of asynchronous coupling enables the rich, context-sensitive interactions that characterize real brain dynamics, suggesting that it plays a role in functional integration that may be as important as synchronous interactions. The distinction between linear and nonlinear coupling has fundamental implications for the analysis and characterization of neuronal interactions, most of which are predicated on linear (synchronous) coupling (e.g. cross-correlograms and coherence). Using neuromagnetic data it is shown that nonlinear (asynchronous) coupling is, in fact, more abundant and can be more significant than synchronous coupling.

Friston, K J

2000-01-01

219

Neuropsychological correlates of emotional lability in children with ADHD  

PubMed Central

Background Emotional lability (EL) is commonly seen in patients with Attention Deficit/Hyperactivity Disorder (ADHD). The reasons for this association are 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 are predicted by particular cognitive and/or motivational dysfunctions and whether these associations are mediated by the presence of ADHD symptoms. Methods A large multi-site sample of 424 carefully diagnosed ADHD cases and 564 unaffected siblings and controls aged 6 to 18 years performed a broad neuropsychological test battery, including a Go/No-Go Task, a warned 4-choice Reaction Time task, the Maudsley Index of Childhood Delay Aversion, and Digit span backwards. Neuropsychological variables were aggregated as indices of processing speed, response variability, executive functions, choice impulsivity and the influence of energetic and/or motivational factors. EL and ADHD symptoms were regressed on each neuropsychological variable in separate analyses controlling for age, gender and IQ, and, in subsequent regression analyses, for ADHD and EL symptoms respectively. Results Neuropsychological variables significantly predicted ADHD and EL symptoms with moderate to low regression coefficients. However, the association between neuropsychological parameters on EL disappeared entirely when the effect of ADHD symptoms was taken into account, revealing that the association between the neuropsychological performance measures and EL is completely mediated statistically by variations in ADHD symptoms. Conversely, neuropsychological effects on ADHD symptoms remained after EL symptom severity was taken into account. Conclusions The neuropsychological parameters examined here predict ADHD more strongly than EL. They cannot explain EL symptoms beyond what is already accounted for by ADHD symptom severity. The association between EL and ADHD cannot be explained by these cognitive or motivational deficits. Alternative mechanisms, including overlapping genetic influences (pleiotropic effects), and/or alternative neuropsychological processes need to be considered.

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

220

Cholesteryl de-esterifying enzyme from Staphylococcus aureus: separation from alpha toxin, purification, and some properties.  

PubMed Central

A cholesteryl de-esterifying enzyme found in partially purified preparations of alpha toxin produced by the Wood 46 strain on Staphylococcus aureus has been separated from other staphylococcal proteins and from alpha toxin by isoelectric focusing and gel filtration. Preparations of alpha toxin from Bi-Gel P-60 columns and of the cholesteryl esterase from Bio-Gel P-200 columns showed a high degree of purity, as determined by analytical ultracentrifugation, gel diffusion, immunoelectrophoresis, and polyacrylamide gel electrophoresis. The molecular weight of the cholesteryl esterase determined by polyacrylamide gel electrophoresis in sodium dodecyl sulfate was 25,500 and on Bio-Gel P-300 columns it was 175,000, indicating an associating system. The density of the enzyme was lower than expected for simple proteins (about 1.19 g/ml). Chloroform-methanol extracts showed the presence of a neutral lipid that did not contain cholesterol. This material, possibly a glycolipid, might play a role in the stabilization of the enzymatically active protomer. The isoelectric point of the esterase was 9.1. Cholesteryl esterase was labile and lost its activity easily. It could bind reversibly to agarose-containing gels. After elution, it was enzymatically inactive, with an isoelectric point of less than 6.2. The W46M mutant of the Wood 46 strain, which does not produce alpha toxin, also does not produce cholesteryl esterase. Images

Harvie, N R

1977-01-01

221

Regulation of the vapBC-1 Toxin-Antitoxin Locus in Nontypeable Haemophilus influenzae  

PubMed Central

Nontypeable Haemophilus influenzae (NTHi) are human-adapted commensal bacteria that can cause a number of chronic mucosal infections, including otitis media and bronchitis. One way for these organisms to survive antibiotic therapy and cause recurrent disease is to stop replicating, as most antimicrobials target essential biosynthetic pathways. Toxin-antitoxin (TA) gene pairs have been shown to facilitate entry into a reversible bacteriostatic state. Characteristically, these operons encode a protein toxin and an antitoxin that associate following translation to form a nontoxic complex, which then binds to and regulates the cognate TA promoter. Under stressful conditions, the labile antitoxin is degraded and the complex disintegrates, freeing the stable toxin to facilitate growth arrest. How these events affected the regulation of the TA locus, as well as how the transcription of the operon was subsequently returned to its normal state upon resumption of growth, was not fully understood. Here we show that expression of the NTHi vapBC-1 TA locus is repressed by a complex of VapB-1 and VapC-1 under conditions favorable for growth, and activated by the global transactivator Factor for Inversion Stimulation (Fis) upon nutrient upshift from stationary phase. Further, we demonstrate for the first time that the VapC-1 toxin alone can bind to its cognate TA locus control region and that the presence of VapB-1 directs the binding of the VapBC-1 complex in the transcriptional regulation of vapBC-1.

Cline, Susan D.; Saleem, Sehresh; Daines, Dayle A.

2012-01-01

222

Ethylenediaminetetraacetic acid (disodium salt)-labile bovine immunoglobulin M Fc binding to Brucella abortus: a cause of nonspecific agglutination.  

PubMed

It was demonstrated by a radioimmunoassay procedure that Brucella abortus agglutinins from noninfected cattle sera, absorbed to B. abortus antigen and eluted with ethylenediaminetetraacetic acid (EDTA), was immunoglobulin M that bound to that bacterium by its Fc portion. The EDTA-eluted immunoglobulin M agglutinated intact B. abortus cells but not erythrocytes treated with B. abortus lipopolysaccharide. The specificity of the EDTA-eluted immunoglobulin was for B. abortus, although a small titer to Yersinia enterocolitica serotype O:9 was observed. In contrast, immunoglobulin M purified from the serum of a cow injected 7 days previously with heat-killed B. abortus bound to the antigen by its Fab portion, was not labile to EDTA treatment, cross-reacted extensively with Y. enterocolitica serotype O:9, and agglutinated various other bacterial antigens and normal erythrocytes. PMID:6790568

Nielsen, K; Stilwell, K; Stemshorn, B; Duncan, R

1981-07-01

223

Ethylenediaminetetraacetic acid (disodium salt)-labile bovine immunoglobulin M Fc binding to Brucella abortus: a cause of nonspecific agglutination.  

PubMed Central

It was demonstrated by a radioimmunoassay procedure that Brucella abortus agglutinins from noninfected cattle sera, absorbed to B. abortus antigen and eluted with ethylenediaminetetraacetic acid (EDTA), was immunoglobulin M that bound to that bacterium by its Fc portion. The EDTA-eluted immunoglobulin M agglutinated intact B. abortus cells but not erythrocytes treated with B. abortus lipopolysaccharide. The specificity of the EDTA-eluted immunoglobulin was for B. abortus, although a small titer to Yersinia enterocolitica serotype O:9 was observed. In contrast, immunoglobulin M purified from the serum of a cow injected 7 days previously with heat-killed B. abortus bound to the antigen by its Fab portion, was not labile to EDTA treatment, cross-reacted extensively with Y. enterocolitica serotype O:9, and agglutinated various other bacterial antigens and normal erythrocytes. Images

Nielsen, K; Stilwell, K; Stemshorn, B; Duncan, R

1981-01-01

224

Translocation-Specific Conformation of Adenylate Cyclase Toxin from Bordetella pertussis Inhibits Toxin-Mediated Hemolysis  

Microsoft Academic Search

Bordetella pertussis adenylate cyclase (AC) toxin belongs to the RTX family of toxins but is the only member with a known catalytic domain. The principal pathophysiologic function of AC toxin appears to be rapid production of intracellular cyclic AMP (cAMP) by insertion of its catalytic domain into target cells (referred to as intoxication). Relative to other RTX toxins, AC toxin

MARY C. GRAY; SANG-JIN LEE; LLOYD S. GRAY; FRANCA R. ZARETZKY; ANGELA S. OTERO; GABOR SZABO; ERIK L. HEWLETT

2001-01-01

225

The three-dimensional crystal structure of cholera toxin  

SciTech Connect

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.

Zhang, Rong-Guang; Westbrook, M.L.; Nance, S.; Spangler, B.D. [Argonne National Lab., IL (United States); Scott, D.L. [Yale Univ., New Haven, CT (United States). Dept. of Molecular Biophysics and Biochemistry; Westbrook, E.M. [Northwestern Univ., Evanston, IL (United States)

1996-02-01

226

Multiple Properties of Cl. Botulinum Toxin.  

National Technical Information Service (NTIS)

Testing Cl. botulinum toxin type A at various times after its preparation it was found that the toxin was not always toxic to the same degree for albino mice and guinea pigs. With the aging of toxin, the toxin's titer decreased to a greater extent for mic...

I. N. Morgunov S. M. Minervin

1966-01-01

227

Stoichiometric regulation of phytoplankton toxins.  

PubMed

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. PMID:24712512

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

2014-06-01

228

Effectiveness of botulinum toxin A in treatment of refractory erythromelalgia.  

PubMed

Erythromelalgia is characterized by intense burning pain, erythema, and heat in affected areas after precipitating factors such as warm temperature or stress. It is refractory to treatment in some situations. We describe a woman with adenosquamous cell carcinoma of the lung and medically refractory erythromelalgia. The symptoms of erythromelalgia presented as refractory to any medical treatment. Due to the unresponsive nature of her condition, botulinum toxin type A (onabotulinumtoxin A) was injected over both of her cheeks, periodically for six cycles. Her symptoms responded dramatically to subcutaneous and intradermal injection of botulinum toxin type A. Repetitive injection demonstrated consistent and reproducible responses, and the efficacy was maintained for approximately 1 month. No adverse effects or complications were noted. Botulinum toxin type A might be safe and effective as an alternative treatment for refractory erythromelalgia, but further large-scale studies are required. PMID:23683264

Lin, Kuan-Hsiang; Wang, Shuu-Jiun; Fuh, Jong-Ling; Chen, Shih-Pin

2013-05-01

229

Conformational variations amongst scorpion toxins.  

PubMed

Circular dichroism spectra were obtained for ten scorpion neurotoxins (representing five species of scorpion) in order to provide an understanding of their relative conformations in solution. Despite a high degree of amino acid sequence homology, the toxins clearly differ from each other in terms of CD-detectable structure. When superimposed, the CD spectra suggest that the toxins form a series of related conformational variants. Since the resemblances amongst the individual CD spectra can be correlated to degrees of sequence resemblance and pharmacological specificity, conformational balance could be an important factor in both toxin evolution and target recognition. PMID:3942749

Dufton, M J; Drake, A F; Rochat, H

1986-01-17

230

Chemical toxins that cause seizures.  

PubMed

Seizurogenic chemicals include a variety of toxic agents, including chemical warfare agents, toxic industrial chemicals, and natural toxins. Chemical weapons such as sarin and VX, and pesticides such as parathion and carbaryl cause hyperstimulation of cholinergic receptors and an increase in excitatory neurotransmission. Glutamatergic hyperstimulation can occur after exposure to excitatory amino acid toxins such as the marine toxin domoic acid. Other pesticides such as lindane and strychnine do not affect excitatory neurotransmission directly, but rather, they block the inhibitory regulation of neurotransmission by antagonism of inhibitory GABA and glycine synapses. In this paper, chemicals that cause seizures by a variety of molecular mechanisms and pathways are discussed. PMID:23085523

Jett, David A

2012-12-01

231

[Botulinum toxin in dermatology].  

PubMed

Treatment with botulinum toxin (BTX) type A has become increasingly important in various clinical areas in dermatology. Particularly popular is the therapy with BTX for hyperkinetic lines associated with muscles of facial expression in aesthetic dermatology, which is the most frequent wrinkle treatment undertaken worldwide. Therapy with BTX also ranks high in curative dermatology. Injections with BTX are the most effective nonoperative therapy for hyperhidrosis. Common indications for the treatment of hyperkinetic lines with BTX are presented in this publication. Therapy of glabellar lines, which has received regulatory approval, is presented in detail. In the second part, treatment of focal hyperhidrosis with emphasis on axillary hyperhidrosis is addressed. In the hand of the experienced practitioner, treatment with BTX in a suitable area of indication is a very safe and effective procedure that leads to remarkable treatment results, associated with a very high patient satisfaction. PMID:24549483

Philipp-Dormston, W G

2014-02-01

232

A Bivalent Tarantula Toxin Activates the Capsaicin Receptor, TRPV1, by Targeting the Outer Pore Domain  

PubMed Central

SUMMARY Toxins have evolved to target regions of membrane ion channels that underlie ligand binding, gating, or ion permeation, and have thus served as invaluable tools for probing channel structure and function. Here we describe a peptide toxin from the Earth Tiger tarantula that selectively and irreversibly activates the capsaicin- and heat-sensitive channel, TRPV1. This high avidity interaction derives from a unique tandem repeat structure of the toxin that endows it with an antibody-like bivalency, illustrating a new paradigm in toxin structure and evolution. The ‘double-knot’ toxin traps TRPV1 in the open state by interacting with residues in the presumptive pore-forming region of the channel, highlighting the importance of conformational changes in the outer pore region of TRP channels during activation.

Bohlen, Christopher J.; Priel, Avi; Zhou, Sharleen; King, David; Siemens, Jan; Julius, David

2010-01-01

233

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

PubMed Central

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.

Wein, Lawrence M.; Liu, Yifan

2005-01-01

234

Cholera Toxin Mechanism of Action  

NSDL National Science Digital Library

This single image file shows the steps of action of cholera toxin, beginning at protein synthesis in the bacteria and proceeding through all of the major known steps of interaction with the host cell.

American Society For Microbiology;

2002-08-29

235

Yeast Killer Toxins Technology Transfer  

Microsoft Academic Search

\\u000a Among the different competitive mechanisms which microorganisms can use to multiply and survive in natural communities, the\\u000a production of antimicrobial toxins represents a common, efficient and specific ecological way to eliminate competitor strains\\/species\\u000a from the same habitat. By killing or severely reducing the fitness of sensitive strains, toxin-producing microorganisms which\\u000a are self-immune can be selected and so dominate in specific

Walter Magliani; Stefania Conti; Laura Giovati; Luciano Polonelli

236

The effect of the castor bean toxin, ricin, on rat IgE and IgG responses.  

PubMed Central

IgE responses are closely regulated in non-atopic humans and low IgE responder animals. After an initial period of IgE production following antigen exposure, IgE synthesis appears to be actively suppressed. Inhalation of the dust of castor beans induces persistent IgE responses in atopic and non-atopic humans alike. This phenomenon was investigated in animals. Hooded Lister rats were immunized intraperitoneally with different preparations of castor bean. These had been heated for different lengths of time, 60 and 15 mins, to inactivate the toxin ricin. Immunization with as much as 100 micrograms of the extract heated for 60 min failed to produce an IgE response, while injection of 100 micrograms of the extract heated for 15 min produced a marked IgE response to castor bean proteins. Thus the component of castor bean extract which induces the IgE response appears to be heat labile. The IgE potentiating component in castor bean was found to enhance IgE responses to other antigens such as ovalbumin and when 0.8 microgram of an unheated castor bean extract was administered together with an optimal dose of ovalbumin, there was a substantial increase in ovalbumin-specific IgE but not IgG in all animals. In addition, total serum IgE but not IgG increased up to 20-fold. The effect of castor bean was more sustainable than that of an established IgE-specific adjuvant, Bordetella pertussis, and was able to boost an IgE response that had diminished and maintain an ongoing IgE response when re-administered at weekly intervals. In addition, it was possible to reproduce the IgE potentiating effects with purified castor bean ricin at 25 ng/rat. The way that it produces this effect is not known but it is possible that ricin blocks the normal IgE suppressive mechanisms that regulate IgE responses.

Thorpe, S C; Murdoch, R D; Kemeny, D M

1989-01-01

237

Differential priming of soil carbon driven by soil depth and root impacts on carbon lability  

NASA Astrophysics Data System (ADS)

An increase in root-derived labile soil carbon (C) inputs (e.g. exudates) can stimulate decomposition of more recalcitrant soil organic carbon (SOC) by priming microbial activity, which can lead to a net loss of soil C storage. This priming effect can be small or large and negative or positive, but the mechanisms by which root-C controls the magnitude and direction of SOC decomposition remain poorly understood. With this study we evaluated how small versus large differences in labile soil C availability affect microbial processing of simulated root exudate inputs and decomposition of SOC. We conducted a laboratory incubation experiment (60 days) with soils collected from under six switchgrass (Panicum virgatum) cultivars to a depth of 60 cm. Differences in specific root length among cultivars were expected to result in small differences in labile soil C availability, whereas differences associated with soil depth were expected to result in large differences in labile soil C availability. Soil cores were divided into 0-10 cm, 20-30 cm and 40-60 cm depth increments, and soils of all cultivars (no roots) across all three depths were incubated with addition of either: (1) water (60% water holding capacity), or (2) labile C provided as a 13C-labeled synthetic root exudate cocktail. We measured CO2 respiration throughout the experiment. The switchgrass was grown for three years in soils that formerly supported C3 pasture grasses, and the natural difference in 13C signature between C3 and C4 plants enabled quantification of differences in the lability of root-derived C among cultivars. Moreover the 13C labeled synthetic root-exudate cocktail amendment to soils allowed us to assess impacts of exudates-C addition on priming in soil derived from the different cultivars and from different depths. Our experiment led to three main results: (1) different cultivars of switchgrass regulate labile C availability across the soil profile differently; (2) small differences in labile C among the soils derived from different cultivars did not significantly mediate the impact of exudates-C additions on priming; (3) but, large differences in labile soil C contents among depths led to differences in priming effects, where greater priming effects were observed for shallow relative to deep soils across all days of the experiment. These results suggest that increased root-derived C inputs will have marginal impacts on decomposition of more stable SOC at depth and that their impact on priming will be similar in soils with small differences in available soil C.

De Graaff, M.; Jastrow, J. D.; Gilette, S.; Johns, A.; Wullschleger, S. D.

2012-12-01

238

Susceptibility of Skeletal Muscle to Coxsackie A2 Virus Infection: Effects of Botulinum Toxin and Denervation  

NASA Astrophysics Data System (ADS)

Coxsackie A viruses can infect denervated but not innervated mature skeletal muscles. The role of synaptic transmission in preventing susceptibility to Coxsackievirus infection was studied by surgically denervating leg muscles of mice or injecting the muscles with botulinum toxin to block quantal release of acetylcholine. Control muscles were injected with heat-inactivated toxin. Subsequent injection of Coxsackie A2 virus resulted in extensive virus replication and tissue destruction in the denervated and botulinum toxin-treated muscles, while the control muscles showed only minimal changes. This suggests that the susceptibility of skeletal muscle to Coxsackievirus infection is regulated by synaptic transmission.

Andrew, Clifford G.; Drachman, Daniel B.; Pestronk, Alan; Narayan, Opendra

1984-02-01

239

Bioreducible and acid-labile poly(amido amine)s for efficient gene delivery  

PubMed Central

Intracellular processes, including endosomal escape and intracellular release, are efficiency-determining steps in achieving successful gene delivery. It has been found that the presence of acid-labile units in polymers can facilitate endosomal escape and that the presence of reducible units in polymers can lead to intracellular release. In this study, poly(amido amine)s with both bioreducible and acid-labile properties were synthesized to improve gene delivery compared with single-responsive carriers. Transfection and cytotoxicity were evaluated in three cell lines. The complexes of DNA with dual-responsive polymers showed higher gene transfection efficiency than single-responsive polymers and polyethylenimine. At the same time, these polymers were tens of times less cytotoxic than polyethylenimine. Therefore, a polymer that is both reducible and acid-labile is a promising material for efficient and biocompatible gene delivery.

Yu, Zhi-Qiang; Yan, Jun-Jie; You, Ye-Zi; Zhou, Qing-Hui

2012-01-01

240

The Interactive Effects of Affect Lability, Negative Urgency, and Sensation Seeking on Young Adult Problematic Drinking  

PubMed Central

Prior studies have suggested that affect lability might reduce the risk for problematic drinking among sensation seekers by compensating for their deficiencies in emotional reactivity and among individuals high on negative urgency by disrupting stable negative emotions. Due to the high prevalence of college drinking, this study examined whether affect lability interacted with sensation seeking and negative urgency to influence college student problematic drinking. 414 college drinkers (mean age: 20, 77% female, and 74% Caucasian) from a US Midwestern University completed self-administered questionnaires online. Consistent with our hypotheses, our results indicated that the effects of sensation seeking and negative urgency on problematic drinking weakened at higher levels of affect lability. These findings emphasize the importance of considering specific emotional contexts in understanding how negative urgency and sensation seeking create risk for problematic drinking among college students. These findings might also help us better understand how to reduce problematic drinking among sensation seekers and individuals high on negative urgency.

Karyadi, Kenny; Coskunpinar, Ayca; Dir, Allyson L.; Cyders, Melissa A.

2013-01-01

241

The polychaete worm Nereis diversicolor increases mercury lability and methylation in intertidal mudflats.  

PubMed

The polychaete worm Nereis diversicolor engineers its environment by creating oxygenated burrows in anoxic intertidal sediments. The authors carried out a laboratory microcosm experiment to test the impact of polychaete burrowing and feeding activity on the lability and methylation of mercury in sediments from the Bay of Fundy, Canada. The concentration of labile inorganic mercury and methylmercury in burrow walls was elevated compared to worm-free sediments. Mucus secretions and organic detritus in worm burrows increased labile mercury concentrations. Worms decreased sulfide concentrations, which increased Hg bioavailability to sulfate-reducing bacteria and increased methylmercury concentrations in burrow linings. Because the walls of polychaete burrows have a greater interaction with organisms, and the overlying water, the concentrations of mercury and methylmercury they contain is more toxicologically relevant to the base of a coastal food web than bulk samples. The authors recommend that researchers examining Hg in marine environments account for sediment dwelling invertebrate activity to more fully assess mercury bioavailability. PMID:23633443

Sizmur, Tom; Canário, João; Edmonds, Samuel; Godfrey, Adam; O'Driscoll, Nelson J

2013-08-01

242

Botulinum Toxin Injections: A Treatment for Muscle Spasms  

MedlinePLUS

... A Treatment for Muscle Spasms What is botulinum toxin? Botulinum toxin is a protein that helps stop muscle ... won't have any harmful effects from the toxin. Botulinum toxin has been used safely for a number ...

243

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

PubMed

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. PMID:19769132

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

2009-09-01

244

Seasonal changes and biochemical composition of the labile organic matter flux in the Cretan Sea  

NASA Astrophysics Data System (ADS)

Downward fluxes of labile organic matter (lipids, proteins and carbohydrates) at 200 (trap A) and 1515 m depth (trap B), measured during a 12 months sediment trap experiment, are presented, together with estimates of the bacterial and cyanobacterial biomasses associated to the particles. The biochemical composition of the settling particles was determined in order to provide qualitative and quantitative information on the flux of readily available organic carbon supplying the deep-sea benthic communities of the Cretan Sea. Total mass flux and labile carbon fluxes were characterised by a clear seasonality. Higher labile organic fluxes were reported in trap B, indicating the presence of resuspended particles coming from lateral inputs. Particulate carbohydrates were the major component of the flux of labile compounds (on annual average about 66% of the total labile organic flux) followed by lipids (20%) and proteins (13%). The biopolymeric carbon flux was very low (on annual average 0.9 and 1.2 gC m -2 y -1, at trap A and B). Labile carbon accounted for most of the OC flux (on annual average 84% and 74% in trap A and B respectively). In trap A, highest carbohydrate and protein fluxes in April and September, corresponded to high faecal pellet fluxes. The qualitative composition of the organic fluxes indicated a strong protein depletion in trap B and a decrease of the bioavailability of the settling particles as a result of a higher degree of dilution with inorganic material. Quantity and quality of the food supply to the benthos displayed different temporal patterns. Bacterial biomass in the sediment traps (on average 122 and 229 ?gC m -2 d -1 in trap A and B, respectively) was significantly correlated to the flux of labile organic carbon, and particularly to the protein and carbohydrate fluxes. Cyanobacterial flux (on average, 1.1 and 0.4 ?gC m -2 d -1, in trap A and B, respectively) was significantly correlated with total mass and protein fluxes only in trap A. Bacterial carbon flux, equivalent to 84.2 and 156 mgC m -2 y -1, accounted for 5-6.5% of the labile carbon flux (in trap A and B respectively) and for 22-41% protein pool of the settling particles. These results suggest that in the Cretan Sea, bacteria attached to the settling particles represent a potential food source of primary importance for deep-sea benthic communities.

Danovaro, Roberto; Della Croce, Norberto; Dell'Anno, Antonio; Mauro Fabiano; Marrale, Daniela; Martorano, Daniela

2000-08-01

245

Mechanism of Action of Tetanus Toxin.  

National Technical Information Service (NTIS)

We have previously reported that tetanus toxin (TT) increased ATP-dependent Calcium (++) uptake by human neutrophil lysosomes, and we hypothesized that the toxin activates the Ca(++) ATPase present in these organelles. However, we have been unable to show...

M. S. Klempner

1989-01-01

246

DETECTION OF BACTERIAL TOXINS WITH MONOSACCHARIDE ARRAYS  

PubMed Central

A large number of bacterial toxins, viruses and bacteria target carbohydrate derivatives on the cell surface to attach to and gain entry into the cell. We report here the use of a monosaccharide-based array to detect protein toxins. The array-based technique provides the capability to perform simultaneous multianalyte analyses. Arrays of N-acetyl galactosamine (GalNAc) and N-acetylneuraminic acid (Neu5Ac) derivatives were immobilized on the surface of a planar waveguide and were used as receptors for protein toxins. These arrays were probed with fluorescently labeled bacterial cells and protein toxins. While Salmonella typhimurium, Listeria monocytogenes, Escherichia coli and staphylococcal enterotoxin B (SEB) did not bind to either of the monosaccharides, both cholera toxin and tetanus toxin bound to GalNAc and Neu5Ac. The results show that the binding of the toxins to the carbohydrates is density dependent and semi-selective. Both toxins were detectable at 100 ng/ml.

Ngundi, Miriam M.; Taitt, Chris R.; McMurry, Scott A.; Kahne, Daniel; Ligler, Frances S.

2006-01-01

247

[Blepharospasm: treatment with botulinum toxin].  

PubMed

Blepharospasm is form of focal dystonia characterized by involuntary and repetitive contractions involving the orbicular oculi muscle. Fourteen patients with blepharospasm were submitted to botulinum toxin type A injections. Of these 14 cases, 6 were male and 8 female. The mean age was 58 years (range: 33 to 76 years) with illness duration ranging from 1 to 25 years (average: 7.3 years). All patients have been treated with conventional therapies with poor results, but presented a good response to botulinum toxin type A. The average latent period was 3 days (range: 0 to 10); maximum effect of treatment was observed after 16 days. The mean duration of maximum response was 90 days. The main side effects of botulinum toxin injections were ptosis and lagophtalmos. PMID:9239894

Barbosa, E R; Silva, H C; Haddad, M S; Bittar, M S

1996-01-01

248

Importance of Toxin A, Toxin B, and CDT in Virulence of an Epidemic Clostridium difficile Strain  

PubMed Central

Clostridium difficile infection is the main cause of healthcare-acquired diarrhea in the developed world. In addition to the main virulence factors toxin A and B, epidemic, PCR Ribotype 027 strains, such as R20291, produce a third toxin, CDT. To develop effective medical countermeasures, it is important to understand the importance of each toxin. Accordingly, we created all possible combinations of isogenic toxin mutants of R20291 and assessed their virulence. We demonstrated that either toxin A or toxin B alone can cause fulminant disease in the hamster infection model and present tantalizing data that C. difficile toxin may also contribute to virulence.

Kuehne, Sarah A.; Collery, Mark M.; Kelly, Michelle L.; Cartman, Stephen T.; Cockayne, Alan; Minton, Nigel P.

2014-01-01

249

Purification of tritium-labeled cholera toxin.  

PubMed Central

Cholera toxin was labeled with tritium by the Wilzbach technique, and highly purified radiolabeled toxin was obtained by Sephadex column chromatography and disc gel electrophoresis. 3H-labeled cholera toxin retained its biological activity and chemical stability and had a specific activity of 405.9 muCi/mumol. The methods utilized in extraction and purification of 3H-labeled toxin may be advantageous for preparation of other biologically active radiolabeled proteins. Images

Banwell, J G; Hanke, D W; Diedrich, D

1978-01-01

250

A Molecular Target for Viral Killer Toxin  

Microsoft Academic Search

Killer strains of S. cerevisiae harbor double-stranded RNA viruses and secrete protein toxins that kill virus-free cells. The K1 killer toxin acts on sensitive yeast cells to perturb potassium homeostasis and cause cell death. Here, the toxin is shown to activate the plasma membrane potassium channel of S. cerevisiae, TOK1. Genetic deletion of TOK1 confers toxin resistance; overexpression increases susceptibility.

Aamir Ahmed; Federico Sesti; Nitza Ilan; Theodore M Shih; Stephen L Sturley; Steve A. N Goldstein

1999-01-01

251

Pseudomembranous colitis: Presence of clostridial toxin.  

PubMed

A toxin was found in the faeces of nine out of nine patients with pseudomembranous colitis and two out of two with antibiotic-associated non-specific colitis. The toxin was neutralised by Clostridium sordellii antitoxin but not by a commercial mixture of C. welchii, oedematiens, and septicum antitoxins. The in-vitro and in-vivo properties of pseudomembranous-colitis toxin closely resemble those of the toxin of C. sordellii. PMID:74727

Larson, H E; Price, A B

252

Botulinum toxin treatment in spasmodic torticollis  

Microsoft Academic Search

Botulinum toxin A was administered to 19 patients in a double-blind placebo controlled trial. Toxin was more effective than placebo for improving both head position and pain which was measured by an objective rating scale and videofilm assessments. Following the controlled trial, treatment with botulinum toxin was continued in an open fashion. A total of 60 patients with torticollis received

J D Blackie; A J Lees

1990-01-01

253

Protein toxins: intracellular trafficking for targeted therapy  

Microsoft Academic Search

The immunotoxin approach is based on the use of tumor-targeting ligands or antibodies that are linked to the catalytic (toxic) moieties of bacterial or plant protein toxins. In this review, we first discuss the current state of clinical development of immunotoxin approaches describing the results obtained with the two toxins most frequently used: diphtheria and Pseudomonas toxin-derived proteins. In the

L Johannes; D Decaudin

2005-01-01

254

Staphylococcal toxins and sudden infant death syndrome  

Microsoft Academic Search

AIMS: To investigate the hypothesis that commonly occurring bacterial toxins cause sudden infant death syndrome (SIDS) by (1), determining in which tissues bacterial toxins are concentrated after intravenous injection in rats; and (2), seeing if the same tissues contain detectable toxins in cases of SIDS. METHODS: The tissue distribution of intravenously injected staphylococcal enterotoxin A (SEA), enterotoxin B (SEB), enterotoxin

J E Malam; G F Carrick; D R Telford; J A Morris

1992-01-01

255

Role of bacterial toxins, bile acids, and free fatty acids in colonic water malabsorption in tropical sprue  

Microsoft Academic Search

Colonic perfusion studies in 10 southern Indian patients with tropical sprue and nine matched healthy adults revealed a defect of water and sodium absorption from the colon in sprue. Heat-labile and heat-stable enterotoxin production was not detected in coliforms cultured from the feces of any of the 19 subjects. The 24-hr fecal bile acid output was increased in patients with

B. S. Ramakrishna; V. I. Mathan

1987-01-01

256

The lability of an intermediate of the ribulose bisphosphate carboxylase reaction.  

PubMed

Interruption of the catalytic cycle of ribulose-bisphosphate carboxylase by acid denaturation liberated an intermediate with a labile phosphate ester. Addition of fresh, buffered carboxylase enzyme to the acidified carboxylase reaction after 5 s inhibited phosphate release from the intermediate. Therefore, the species with a labile phosphate ester was stable for 5 s in acid and was apparently a substrate for the enzymatic reaction, since the labile intermediate was converted to a stable form by the protein. After acid denaturation, the carboxylated intermediate could be stabilized by reduction after 5 s in acid, but after 1 h no carboxylated intermediate remained. The stoichiometries of phosphate released to enzyme active sites and the carboxylated intermediate trapped to enzyme active sites were approximately 0.04. It was concluded that the labile phosphate species is probably the carboxylated intermediate rather than the enediol(ate) intermediate. The carboxylase and oxygenase reactions were probed for intermediates by the ability of the enzymatic reaction to reduce hexacyanoferrate(III), dichlorophenolindophenol, or nitroblue tetrazolium. Reduction of these reagents and hexacyanoferrate(III)-dependent paracatalytic inactivation were not observed. The copper chelate of lysine, a superoxide dismutase active species, did not selectively inhibit ribulose-bisphosphate oxygenase. PMID:6625602

Mulligan, R M; Tolbert, N E

1983-09-01

257

Labile proteins accumulated in damaged hair upon permanent waving and bleaching treatments  

Microsoft Academic Search

We previously found that certain hair proteins were soluble by means of a partial extraction method. In this study, we demonstrate that the amount of soluble proteins internally formed in permed and bleached hair, labile proteins, is a useful index for hair damage assessment. Compared to tensile property changes, this index rose in widely dynamic ranges as the time of

TAKAFUMI INOUE; MAYUMI ITO; KENJI KIZAWA

258

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

PubMed

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

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

2013-10-01

259

In situ measurements of labile Cu, Cd and Mn in river waters using DGT  

Microsoft Academic Search

The technique of diffusive gradients in thin-films (DGT) has been trialed in two river systems for in situ trace metal speciation measurements. This paper presents results for cadmium, copper and manganese concentrations in fresh and estuarine waters and demonstrates for the first time the effectiveness of using DGT to measure labile metal concentrations in such waters. This work has shown

Susan Denney; John Sherwood; James Leyden

1999-01-01

260

[Effects of straw application and earthworm inoculation on soil labile organic carbon].  

PubMed

A six-year field plot experiment of rice-wheat rotation was conducted to study the effects of straw application and earthworm inoculation on cropland soil organic carbon and labile organic carbon. Five treatments were installed, i.e., CK, straw mulch (M), straw mulch plus earthworm inoculation (ME), incorporated straw with soil (I), and incorporated straw with soil plus earthworm inoculation (IE). The results showed that soil organic carbon content increased significantly after six years straw application, and treatment I was more efficient than treatment M. Earthworm inoculation under straw application had no significant effects on soil organic carbon content. Straw application, whether straw mulch or incorporated straw with soil, increased the content of soil labile organic carbon, and incorporated straw with soil was more beneficial to the increase of the contents of hot water-extractable carbon, potentially mineralizable carbon, acid-extractable carbon, readily oxidizable carbon, particulate organic carbon, and light fraction organic carbon. There was a little relationship between the quantitative variations of soil dissoluble organic carbon and microbial biomass carbon and the patterns of straw application. Among the treatments, the activity of soil organic carbon was decreased in the order of IF > I > M > ME > CK. Straw application pattern was the main factor affecting soil organic carbon and labile organic carbon, while earthworm inoculation was not universally significanfly effective to all kinds of soil labile organic carbon. PMID:17615878

Yu, Jian-Guang; Li, Hui Xin; Chen, Xiao-Yun; Hu, Feng

2007-04-01

261

Analysis of the genetic stability of Eucalyptus globulus Labill. somatic embryos by flow cytometry  

Microsoft Academic Search

Flow cytometry was used to measure the nuclear DNA content of Eucalyptus globulus Labill. somatic and zygotic embryos and leaves in order to determine if somatic embryogenesis induces DNA content and ploidy changes in this species. Mature zygotic embryos derived from open-pollination orchard families were collected from a location in the centre of Portugal. One group was kept for nuclear

G. Pinto; J. Loureiro; T. Lopes; C. Santos

2004-01-01

262

Rapid, Labile, and Protein Synthesis Independent Short-Term Memory in Conditioned Taste Aversion  

Microsoft Academic Search

Short-term memory is a rapid, labile, and protein-synthesis-independent phase of memory. The existence of short-term memory in conditioned taste aversion (CTA) learning has not been demonstrated formally. To determine the earliest time at which a CTA is expressed, we measured intraoral intake of sucrose at 15 min, 1 hr, 6

Thomas A. Houpt; RoseAnn Berlin

263

Alpine grassland soils contain large proportion of labile carbon but indicate long turnover times  

Microsoft Academic Search

Alpine soils are expected to contain large amounts of labile carbon (C) which may become a further source of atmospheric carbon dioxide (CO2) as a result of global warming. However, there is little data available on these soils, and understanding of the influence of environmental factors on soil organic matter (SOM) turnover is limited. We extracted 30 cm deep cores

K. Budge; J. Leifeld; E. Hiltbrunner; J. Fuhrer

2011-01-01

264

Effects of wetland recovery on soil labile carbon and nitrogen in the Sanjiang Plain.  

PubMed

Soil management significantly affects the soil labile organic factors. Understanding carbon and nitrogen dynamics is extremely helpful in conducting research on active carbon and nitrogen components for different kinds of soil management. In this paper, we examined the changes in microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), dissolved organic carbon (DOC), and dissolved organic nitrogen (DON) to assess the effect and mechanisms of land types, organic input, soil respiration, microbial species, and vegetation recovery under Deyeuxia angustifolia freshwater marshes (DAMs) and recovered freshwater marsh (RFM) in the Sanjiang Plain, Northeast China. Identifying the relationship among the dynamics of labile carbon, nitrogen, and soil qualification mechanism using different land management practices is therefore important. Cultivation and land use affect intensely the DOC, DON, MBC, and MBN in the soil. After DAM soil tillage, the DOC, DON, MBC, and MBN at the surface of the agricultural soil layer declined significantly. In contrast, their recovery was significant in the RFM surface soil. A long time was needed for the concentration of cultivated soil total organic carbon and total nitrogen to be restored to the wetland level. The labile carbon and nitrogen fractions can reach a level similar to that of the wetland within a short time. Typical wetland ecosystem signs, such as vegetation, microbes, and animals, can be recovered by soil labile carbon and nitrogen fraction restoration. In this paper, the D. angustifolia biomass attained natural wetland level after 8 years, indicating that wetland soil labile fractions can support wetland eco-function in a short period of time (4 to 8 years) for reconstructed wetland under suitable environmental conditions. PMID:23151838

Huang, Jingyu; Song, Changchun; Nkrumah, Philip Nti

2013-07-01

265

Inputs of total and labile trace metals from wastewater treatment plants effluents to the Seine River  

NASA Astrophysics Data System (ADS)

The Seine river basin has long been impacted by metal inputs from the Paris area, but the water quality has been gradually improving for the last 20 years. Among all metal pollution sources (surface runoff, industries), urban wastewater discharge has been shown to significantly contribute, during low-flow periods, to metal fluxes of the River Seine. This paper assesses the current wastewater contribution to metal inputs in the Seine river basin, based on sampling of nine wastewater treatment plants (WWTPs). Seven metals were targeted (Al, Cd, Cr, Cu, Fe, Ni and Pb) during dry weather periods. Since total and dissolved concentrations alone are not relevant enough for an ecological risk assessment, labile metals (free + weekly complexed) were also measured by means of DGT (diffusive gradient in thin film technique). Results show that WWTPs greatly reduce total metal concentrations but reduce labile metal concentrations only slightly. Estimations made for direct total metal inputs in the River Seine via treated effluent discharge confirm the decrease observed for the 1994-1995 period. Labile metals released by WWTP were also considered by comparing fluxes in the effluent discharge of two different WWTPs to those flowing in the receiving river. Fluxes discharged by the largest plant were similar to those measured in the river during low-flow periods whereas they were negligible for the smaller one. Nevertheless, labile metal concentrations in both discharges were similar and the wastewater discharge’s contribution to labile fluxes in receiving waters seems to depend mostly on the relative significance of the discharge flow compared to the receiving water flow.

Buzier, Rémy; Tusseau-Vuillemin, Marie-Hélène; Keirsbulck, Marion; Mouchel, Jean-Marie

266

Primary production contributes to non-labile organic matter generation in the estuarine and coastal zone  

NASA Astrophysics Data System (ADS)

Oceanic generation of refractory organic matter is an important pathway for safe and long time scale safe carbon sequestration. Since refractory/non-labile organic matter generation is highly related with microorganism, estuaries and coastal zones with high primary production should be important regions for such generation process. We investigated the particulate organic matter in the estuarine and adjacent coastal zone of the Changjiang (Yangtze River). Peptidoglycan estimated on the basis of D-form of amino acids enantiomers showed a large variation in the estuary but generally lower than the lower reaches (XLJ). Peptidoglycan quickly decreased from the river to the sea, when DI increased from negative to < 0.5. The decrease can be due to dilution by fresh organic matter and seawater. But when DI > 0.5, the peptidoglycan concentration began to positively relate with organic matter freshness and normalized peptidoglycan was comparable to or even higher than that in terrestrial organic matter. This indicates that estuarine and coastal zones make a significant contribution to non-labile organic matter production. Further analysis suggests that heterotrophic bacteria and Synechococcus are notable contributors. For large river's estuary and adjacent coastal zone, terrestrial inputs promote high in situ production. The generated fresh organic matter in the estuary further promotes heterotrophic bacteria. Since the generation of non-labile organic matter process is both contributed by autotrophic and heterotrophic microorganisms, primary production is indirectly generating refractory/non-labile organic matter. And the refractory/non labile organic matter production occurs routinely during every productive season. On another aspect, considering the shallow water depth (usually < 100 m) and high sedimentation rate (e.g., 0-5 cm/year for the Changjiang Estuary), the organic matter can be buried in sediment much more easily than it is in the open ocean.

Zhu, Z.; Zhang, J.; Wu, Y.

2013-12-01

267

Botulinum toxin in migraine prophylaxis  

Microsoft Academic Search

Migraine is a chronic headache disorder manifesting in attacks lasting 4–72 hours. Characteristics of headache are unilateral location, pulsating quality, moderate or severe intensity, aggravation by routine physical activity, and association with nausea, photophobia and phonophobia. The migraine aura is a complex of neurological symptoms, which occurs just before or at the onset of migraine headache. Botulinum toxin A represents

Hartmut Göbel

2004-01-01

268

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....

269

A bivalent tarantula toxin activates the capsaicin receptor, TRPV1, by targeting the outer pore domain.  

PubMed

Toxins have evolved to target regions of membrane ion channels that underlie ligand binding, gating, or ion permeation, and have thus served as invaluable tools for probing channel structure and function. Here, we describe a peptide toxin from the Earth Tiger tarantula that selectively and irreversibly activates the capsaicin- and heat-sensitive channel, TRPV1. This high-avidity interaction derives from a unique tandem repeat structure of the toxin that endows it with an antibody-like bivalency. The "double-knot" toxin traps TRPV1 in the open state by interacting with residues in the presumptive pore-forming region of the channel, highlighting the importance of conformational changes in the outer pore region of TRP channels during activation. PMID:20510930

Bohlen, Christopher J; Priel, Avi; Zhou, Sharleen; King, David; Siemens, Jan; Julius, David

2010-05-28

270

Antibody-based bacterial toxin detection  

NASA Astrophysics Data System (ADS)

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 one step assay, antibodies against Cholera toxin or Staphylococcus Enterotoxin B were noncovalently immobilized on quartz fibers and probed with fluorescein-isothiocyanate (FITC)-labeled toxins. In the two-step assay, Cholera toxin or Botulinum toxoid A was immobilized onto the fiber, followed by incubation in an antiserum or partially purified antitoxin IgG. These were then probed with FITC-anti-IgG antibodies. Unlabeled toxins competed with labeled toxins or antitoxin IgG in a dose-dependent manner and the detection of the toxins was in the nanomolar range.

Menking, Darrell E.; Heitz, Jonathon M.; Anis, Nabil A.; Thompson, Roy G.

1994-03-01

271

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)

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, which use DOC for growth and energy. At the decadal scale, permafrost thaw will result in wholesale change in plant community composition and ecosystem function, thus relying on an entirely different interpretation of shifts in microbial community composition to gain insight into greenhouse gas production. At Bonanza Creek, there are large differences in microbial community composition between intact permafrost and thermokarst bog soils. Metagenomic and metatransciptome analysis of microbial communities reveal that changes in community composition and representative functional genes reflect the dominant greenhouse gas producing processes occurring in those environments. Results indicated that the relative abundance of microbial functional groups based upon functional genes (e.g. methanogens, nitrate reducers, sulfate reducers) mirror the geochemistry of the system and pathways of potential greenhouse gas production. These data help to understand linkages between the level of detail undertaken within -omics research and the temporal scale of biogeochemical processes under examination.

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

2012-12-01

272

Evaluation of the extraction efficiency of thermally labile bioactive compounds in Gastrodia elata Blume by pressurized hot water extraction and microwave-assisted extraction.  

PubMed

Our earlier work showed that the stability of the bioactive compounds gastrodin (GA) and vanillyl alcohol (VA) in Gastrodia elata Blume behaved differently with varying compositions of water-ethanol using pressurized liquid extraction (PLE) at room temperature. To have a better understanding of the extraction process of these thermally labile compounds under elevated temperature conditions, pressurized hot water extraction (PHWE) and microwave-assisted extraction (MAE) methods were proposed. PHWE and MAE showed that GA and VA could be extracted using pure water under optimized conditions of temperature and extraction time. The extraction efficiency of GA and VA by the proposed methods was found to be higher or comparable to heating under reflux using water. The marker compounds present in the plant extracts were determined by RP-HPLC. The optimized conditions were found to be different for the two proposed methods on extraction of GA and VA. The method precision (RSD, n=6) was found to vary from 0.92% to 3.36% for the two proposed methods on different days. Hence, PHWE and MAE methods were shown to be feasible alternatives for the extraction of thermally labile marker compounds present in medicinal plants. PMID:18206897

Teo, Chin Chye; Tan, Swee Ngin; Yong, Jean Wan Hong; Hew, Choy Sin; Ong, Eng Shi

2008-02-22

273

Pathways followed by ricin and Shiga toxin into cells  

Microsoft Academic Search

The plant toxin ricin and the bacterial toxin Shiga toxin belong to a group of protein toxins that inhibit protein synthesis in cells enzymatically after entry into the cytosol. Ricin and Shiga toxin, which both have an enzymatically active moiety that inactivates ribosomes and a moiety that binds to cell surface receptors, enter the cytosol after binding to the cell

Kirsten Sandvig; Stine Grimmer; Silje Ugland Lauvrak; Maria Lyngaas Torgersen; Grethe Skretting; Bo van Deurs; Tore Iversen

2002-01-01

274

Decrease of labile Zn and Cd in the rhizosphere of hyperaccumulating Thlaspi caerulescens with time.  

PubMed

By using a rhizobox micro-suction cup technique we studied in-situ mobilization and complexation of Zn and Cd in the rhizosphere of non-hyperaccumulating Thlaspi perfoliatum and two different Thlaspi caerulescens ecotypes, one of them hyperaccumulating Zn, the other Zn and Cd. The dynamic fraction (free metal ions and small labile complexes) of Zn and Cd decreased with time in the rhizosphere solution of the respective hyperaccumulating T. caerulescens ecotypes, and at the end of the experiment, it was significantly smaller than in the other treatments. Furthermore, the rhizosphere solutions of the T. caerulescens ecotypes exhibited a higher UV absorptivity than the solution of the T. perfoliatum rhizosphere and the plant-free soil. Based on our findings we suggest that mobile and labile metal-dissolved soil organic matter complexes play a key role in the rapid replenishment of available metal pools in the rhizosphere of hyperaccumulating T. caerulescens ecotypes, postulated earlier. PMID:19913965

Dessureault-Rompré, Jacynthe; Luster, Jörg; Schulin, Rainer; Tercier-Waeber, Mary-Lou; Nowack, Bernd

2010-05-01

275

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

PubMed

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

Popescu, I; Biasioli, M; Ajmone-Marsan, F; St?nescu, R

2013-01-01

276

The toxin and antidote puzzle  

PubMed Central

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.

2011-01-01

277

Labile and Refractory Forms of Phosphorus in Runoff of the Redwood River Basin, Minnesota  

Microsoft Academic Search

Fractionation procedures and phosphorus (P) adsorption-desorption assays were used to delineate labile forms (i.e., subject to transformations which make them available for uptake by biota) and refractory forms (subject to permanent burial) of P in the runoff of the Redwood River basin, an agriculturally-dominated tributary of the Minnesota River. Over several storm periods monitored in 1999, 75% of the P

William F. James; John W. Barko; Harry L. Eakin

2002-01-01

278

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

PubMed

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

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

2013-11-01

279

The short-term cover crops increase soil labile organic carbon in southeastern Australia  

Microsoft Academic Search

Little information is available about the effects of cover crops on soil labile organic carbon (C), especially in Australia.\\u000a In this study, two cover crop species, i.e., wheat and Saia oat, were broadcast-seeded in May 2009 and then crop biomass was\\u000a crimp-rolled onto the soil surface at anthesis in October 2009 in southeastern Australia. Soil and crop residue samples were

Xiaoqi Zhou; Chengrong Chen; Shunbao Lu; Yichao Rui; Hanwen Wu; Zhihong Xu

280

Pharmacokinetics of hydralazine and its acid-labile hydrazone metabolites in relation to acetylator phenotype  

Microsoft Academic Search

The pharmacokinetics of hydralazine (H) and its acid-labile hydrazone metabolites were compared in rapid and slow acetylators. Following a 20-mg intravenous infusion, the elimination half-life (t1\\/2ß) and the apparent volume of distribution of H did not differ between the two groups. Plasma clearance estimates approached hepatic blood flow. When a single 100-mg dose of H was given-orally, the area under

Danny D. Shen; James P. Hosler; Richard L. Schroder; Daniel L. Azarnoff

1980-01-01

281

Pseudopolarographic determination of stability constants of labile zinc complexes in fresh water  

Microsoft Academic Search

The formation and distribution of labile zinc species in fresh water were investigated by using a pseudopolarographic approach. Pseudopolarograms were obtained by plotting the anodic stripping voltammetric peak current versus the deposition potential for a series of solutions containing 100 ?g\\/l Zn(II) and increasing amounts of ligand, at the pH of a typical river water sample. Stoichiometry and stability constants

M. Vega; R. Pardo; M. M. Herguedas; E. Barrado; Y. Castrillejo

1995-01-01

282

Toxin-Antitoxin Genes of the Gram-Positive Pathogen Streptococcus pneumoniae: So Few and Yet So Many  

PubMed Central

Summary: Pneumococcal infections cause up to 2 million deaths annually and raise a large economic burden and thus constitute an important threat to mankind. Because of the increase in the antibiotic resistance of Streptococcus pneumoniae clinical isolates, there is an urgent need to find new antimicrobial approaches to triumph over pneumococcal infections. Toxin-antitoxin (TA) systems (TAS), which are present in most living bacteria but not in eukaryotes, have been proposed as an effective strategy to combat bacterial infections. Type II TAS comprise a stable toxin and a labile antitoxin that form an innocuous TA complex under normal conditions. Under stress conditions, TA synthesis will be triggered, resulting in the degradation of the labile antitoxin and the release of the toxin protein, which would poison the host cells. The three functional chromosomal TAS from S. pneumoniae that have been studied as well as their molecular characteristics are discussed in detail in this review. Furthermore, a meticulous bioinformatics search has been performed for 48 pneumococcal genomes that are found in public databases, and more putative TAS, homologous to well-characterized ones, have been revealed. Strikingly, several unusual putative TAS, in terms of components and genetic organizations previously not envisaged, have been discovered and are further discussed. Previously, we reported a novel finding in which a unique pneumococcal DNA signature, the BOX element, affected the regulation of the pneumococcal yefM-yoeB TAS. This BOX element has also been found in some of the other pneumococcal TAS. In this review, we also discuss possible relationships between some of the pneumococcal TAS with pathogenicity, competence, biofilm formation, persistence, and an interesting phenomenon called bistability.

Chan, Wai Ting; Moreno-Cordoba, Inma

2012-01-01

283

Novel Class of Spider Toxin  

PubMed Central

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.

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

284

Neutralising antibodies against ricin toxin.  

PubMed

The Centers for Disease Control and Prevention have listed the potential bioweapon ricin as a Category B Agent. Ricin is a so-called A/B toxin produced by plants and is one of the deadliest molecules known. It is easy to prepare and no curative treatment is available. An immunotherapeutic approach could be of interest to attenuate or neutralise the effects of the toxin. We sought to characterise neutralising monoclonal antibodies against ricin and to develop an effective therapy. For this purpose, mouse monoclonal antibodies (mAbs) were produced against the two chains of ricin toxin (RTA and RTB). Seven mAbs were selected for their capacity to neutralise the cytotoxic effects of ricin in vitro. Three of these, two anti-RTB (RB34 and RB37) and one anti-RTA (RA36), when used in combination improved neutralising capacity in vitro with an IC(50) of 31 ng/ml. Passive administration of association of these three mixed mAbs (4.7 µg) protected mice from intranasal challenges with ricin (5 LD(50)). Among those three antibodies, anti-RTB antibodies protected mice more efficiently than the anti-RTA antibody. The combination of the three antibodies protected mice up to 7.5 hours after ricin challenge. The strong in vivo neutralising capacity of this three mAbs combination makes it potentially useful for immunotherapeutic purposes in the case of ricin poisoning or possibly for prevention. PMID:21633505

Prigent, Julie; Panigai, Laetitia; Lamourette, Patricia; Sauvaire, Didier; Devilliers, Karine; Plaisance, Marc; Volland, Hervé; Créminon, Christophe; Simon, Stéphanie

2011-01-01

285

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

286

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

PubMed

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

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

2013-10-01

287

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

SciTech Connect

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.

De Graaff, Marie-Anne [ORNL; Classen, Aimee T [University of Tennessee, Knoxville (UTK); Castro Gonzalez, Hector F [ORNL; Schadt, Christopher Warren [ORNL

2010-01-01

288

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

PubMed

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. PMID:24724972

Lande, R

2014-05-01

289

Diphtheria toxin, diphtheria-related fusion protein toxins, and the molecular mechanism of their action against eukaryotic cells  

Microsoft Academic Search

Diphtheria toxin remains one of the most successfully studied of the bacterial protein toxins. A detailed understanding of the structure function relationships of the toxin and the role of each domain in the intoxication process is well understood. This understanding has led to the development of diphtheria toxin-related fusion protein toxins which are targeted toward specific cell surface receptors. The

Ryan Ratts; John R. Murphy

290

Comparison of the killer toxin of several yeasts and the purification of a toxin of type K 2  

Microsoft Academic Search

A total of 13 killer toxin producing strains belonging to the genera Saccharomyces, Candida and Pichia were tested against each other and against a sensitive yeast strain. Based on the activity of the toxins 4 different toxins of Saccharomyces cerevisiae, 2 different toxins of Pichia and one toxin of Candida were recognized. The culture filtrate of Pichia and Candida showed

P. Pfeiffer; F. Radler

1984-01-01

291

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. ...

292

The pyrogenic effect of scarlet fever toxin  

Microsoft Academic Search

Scarlet fever toxin was found to liberate leukocytic pyrogen from granulocytesin vitro. In comparative experiments withSalmonella paratyphi B endotoxin and scarlet fever toxin it was tested whether leukocytes from rabbits tolerant to one of these toxins are able\\u000a to synthetize and liberate endogenous pyrogen. Leukocytes from rabbits tolerant to endotoxin liberated leukoeytic pyrogen\\u000a following challenge with endotoxin or with scarlet

V. SCHUI-I; V?ra H?íbalová

1966-01-01

293

Application of botulinum toxin in pain management.  

PubMed

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. PMID:21390172

Sim, Woo Seog

2011-03-01

294

Application of Botulinum Toxin in Pain Management  

PubMed Central

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.

2011-01-01

295

Lability of metal ion-fulvic acid complexes as probed by FIA and DGT: a comparative study  

Microsoft Academic Search

Two kinetic-based analytical techniques with very different time constants (flow injection analysis, FIA and diffusive gradients in thin films, DGT) have been compared in a study of metal ion lability in the systems Al3+–FA and Cu2+–FA (fulvic acid, FA). Flow injection analysis used an in-line micro-column of chelating ion exchanger to capture the labile metal fraction during the short contact

Alison J Downard; Jared Panther; Young-Chool Kim; Kipton J Powell

2003-01-01

296

Using climatological transects to understand the relationship between soil C lability-temperature sensitivity  

NASA Astrophysics Data System (ADS)

The question of how temperature sensitivity of soil organic matter (OM) decomposition varies with its lability is likely to be a main determinant of whether soils act as a sink or source for atmospheric CO2 under the climate of the future. This question is unaddressed in leading climate-carbon models, masking a potentially large source of uncertainty with substantial implications for changes in soil carbon stocks. Kinetic theory suggests that biochemically complex OM substrates that normally resist decomposition should be more sensitive to temperature than labile substrates that decompose quickly. If decomposition of resistant soil OM is more sensitive to temperature than is labile soil OM, then warmer sites should be depleted of resistant soil OM relative to cooler sites and measures of soil quality should be greater at warmer sites. This should be true regardless of differences in OM input amounts or quality for comparison of compounds within a decay cascade (e.g., whole soil C:N ratio or lignin:lignitic aldehydes:lignitic acids) for sites at steady state (i.e., sites with a long-term history under a given land use regime). Some anecdotal data on tropical soil fertility support this prediction as do data from incubations of soils from across the Great Plains and Canadian forests, though shorter-term data from temperate forest soil incubations do not. Soil C:N data newly synthesized to test this prediction are consistent with the expectation that whole soil and silt-associated C:N ratios will increase with site mean annual temperature and that the MAT-C:N relationship for clay-associated soil OM will be weaker or non-existent. Data collected along a climosequence arrayed across the Great Plains show that soils at warmer sites are enriched in labile lignin decay products and depleted in resistant products, which are more biochemically resistant to decomposition than lignin itself. All of these results support the prediction of kinetic theory - that the temperature sensitivity of decomposition of resistant soil OM is greater than that of labile soil OM.

Conant, R.

2009-04-01

297

42 CFR 73.3 - HHS select agents and toxins.  

Code of Federal Regulations, 2010 CFR

...select agents and toxins: Abrin Botulinum neurotoxins ...0.5 mg of Botulinum neurotoxins...perfringens epsilon toxin; 100 mg of...select agent or toxin to CDC or APHIS...The seizure of Botulinum...

2011-10-01

298

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

NASA Astrophysics Data System (ADS)

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 (PM2.5) collected on quartz fiber filters as part of the Southeastern Aerosol Research and Characterization (SEARCH) program. The five samples were collected at two sites (Birmingham, AL and Atlanta, GA) with very different sources of atmospheric particulate matter. In all instances, the refractory carbon contained significantly less radiocarbon than the TC suggesting, not unexpectedly, a source of particulate carbon from the combustion of fossil material. We will present results from the analysis of the same filters in the flow-through system. The implication of our results for the use of radiocarbon in the quantitative apportionment of atmospheric particulate matter sources will be discussed. Gustafsson O., T. Bucheli, Z. Kukulska, M. Andersson, C. Largeau, J-N. Rouzaud, C. Reddy and T. Eglinton (2001) Evaluation of a protocol for the quantification of black carbon in sediments. GBD 15, 881-890.

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

2006-12-01

299

Regulation of the Escherichia coli HipBA Toxin-Antitoxin System by Proteolysis  

PubMed Central

Bacterial populations produce antibiotic-tolerant persister cells. A number of recent studies point to the involvement of toxin/antitoxin (TA) modules in persister formation. hipBA is a type II TA module that codes for the HipB antitoxin and the HipA toxin. HipA is an EF-Tu kinase, which causes protein synthesis inhibition and dormancy upon phosphorylation of its substrate. Antitoxins are labile proteins that are degraded by one of the cytosolic ATP-dependent proteases. We followed the rate of HipB degradation in different protease deficient strains and found that HipB was stabilized in a lon- background. These findings were confirmed in an in vitro degradation assay, showing that Lon is the main protease responsible for HipB proteolysis. Moreover, we demonstrated that degradation of HipB is dependent on the presence of an unstructured carboxy-terminal stretch of HipB that encompasses the last 16 amino acid residues. Further, substitution of the conserved carboxy-terminal tryptophan of HipB to alanine or even the complete removal of this 16 residue fragment did not alter the affinity of HipB for hipBA operator DNA or for HipA indicating that the major role of this region of HipB is to control HipB degradation and hence HipA-mediated persistence.

Hansen, Sonja; Vulic, Marin; Min, Jungki; Yen, Tien-Jui; Schumacher, Maria A.; Brennan, Richard G.; Lewis, Kim

2012-01-01

300

Initial studies of the structural signal for extracellular transport of cholera toxin and other proteins recognized by Vibrio cholerae.  

PubMed

The specificity of the pathway used by Vibrio cholerae for extracellular transport of cholera toxin (CT) and other proteins was examined in several different ways. First, V. cholerae was tested for the ability to secrete the B polypeptides of the type II heat-labile enterotoxins of Escherichia coli. Genes encoding the B polypeptide of LT-IIb in pBluescriptKS- phagemids were introduced into V. cholerae by electroporation. Culture supernatants and periplasmic extracts were collected from cultures of the V. cholerae transformants, and the enterotoxin B subunits were measured by an enzyme-linked immunosorbent assay. Results confirmed that the B polypeptides of both LT-IIa and LT-IIb were secreted by V. cholerae with efficiencies comparable to that measured for secretion of CT. Second, the plasmid clones were introduced into strain M14, an epsE mutant of V. cholerae. M14 failed to transport the B polypeptides of LT-IIa and LT-IIb to the extracellular medium, demonstrating that secretion of type II enterotoxins by V. cholerae proceeds by the same pathway used for extracellular transport of CT. These data suggest that an extracellular transport signal recognized by the secretory machinery of V. cholerae is present in LT-IIa and LT-IIb. Furthermore, since the B polypeptide of CT has little, if any, primary amino acid sequence homology with the B polypeptide of LT-IIa or LT-IIb, the transport signal is likely to be a conformation-dependent motif. Third, a mutant of the B subunit of CT (CT-B) with lysine substituted for glutamate at amino acid position 11 was shown to be secreted poorly by V. cholerae, although it exhibited immunoreactivity and ganglioside GM1-binding activity comparable to that of wild-type CT-B. These findings suggest that Glu-11 may be within or near the extracellular transport motif of CT-B. Finally, the genetic lesion in the epsE allele of V. cholerae M14 was determined by nucleotide sequence analysis. PMID:7558324

Connell, T D; Metzger, D J; Wang, M; Jobling, M G; Holmes, R K

1995-10-01

301

Comparison of the relative toxicities of Shiga-like toxins type I and type II for mice.  

PubMed Central

In earlier studies using a streptomycin-treated mouse model of infection caused by enterohemorrhagic Escherichia coli (EHEC), animals fed Shiga-like toxin type II (SLT-II)-producing strains developed acute renal cortical necrosis and died, while mice fed Shiga-like toxin type I (SLT-I)-producing clones did not die (E. A. Wadolkowski, L. M. Sung, J. A. Burris, J. E. Samuel, and A. D. O'Brien, Infect. Immun. 58:3959-3965, 1990). To examine the bases for the differences we noted between the two toxins in the murine infection model, we injected mice with purified toxins and carried out histopathological examinations. Despite the genetic and structural similarities between the two toxins, SLT-II had a 50% lethal dose (LD50) which was approximately 400 times lower than that of SLT-I when injected intravenously or intraperitoneally into mice. Histopathologic examination of toxin-injected mice revealed that detectable damage was limited to renal cortical tubule epithelial cells. Passive administration of anti-SLT-II antibodies protected mice from SLT-II-mediated kidney damage and death. Immunofluorescence staining of normal murine kidney sections incubated with purified SLT-I or SLT-II demonstrated that both toxins bound to cortical tubule and medullary duct epithelial cells. Compared with SLT-I, SLT-II was more heat and pH stable, suggesting that SLT-II is a relatively more stable macromolecule. Although both toxins bound to globotriaosylceramide, SLT-I bound with a higher affinity in a solid-phase binding assay. Differences in enzymatic activity between the two toxins were not detected. These data suggest that structural/functional differences between the two toxins, possibly involving holotoxin stability and/or receptor affinity, may contribute to the differential LD50s in mice. Images

Tesh, V L; Burris, J A; Owens, J W; Gordon, V M; Wadolkowski, E A; O'Brien, A D; Samuel, J E

1993-01-01

302

Botulinum toxin: The Midas touch  

PubMed Central

Botulinum Toxin (BT) is a natural molecule produced during growth and autolysis of bacterium called Clostridium botulinum. Use of BT for cosmetic purposes has gained popularity over past two decades, and recently, other therapeutic uses of BT has been extensively studied. BT is considered as a minimally invasive agent that can be used in the treatment of various orofacial disorders and improving the quality of life in such patients. The objective of this article is to review the nature, mechanism of action of BT, and its application in various head and neck diseases.

Shilpa, P. S.; Kaul, Rachna; Sultana, Nishat; Bhat, Suraksha

2014-01-01

303

Plant Insecticidal Toxins in Ecological Networks  

PubMed Central

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.

Ibanez, Sebastien; Gallet, Christiane; Despres, Laurence

2012-01-01

304

Brown spider dermonecrotic toxin directly induces nephrotoxicity  

SciTech Connect

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 culture substratum. In addition, dermonecrotic toxin treatment of MDCK cells changed their viability evaluated by XTT and Neutral-Red Uptake methodologies. The present results point to brown spider dermonecrotic toxin cytotoxicity upon renal structures in vivo and renal cells in vitro and provide experimental evidence that this brown spider toxin is directly involved in nephrotoxicity evoked during Loxosceles spider venom accidents.

Chaim, Olga Meiri [Department of Cell Biology, Federal University of Parana, Jardim das Americas, 81531-990, Curitiba, Parana (Brazil); Sade, Youssef Bacila [Department of Cell Biology, Federal University of Parana, Jardim das Americas, 81531-990, Curitiba, Parana (Brazil); Bertoni da Silveira, Rafael [Department of Biochemistry, Federal University of Sao Paulo, Sao Paulo (Brazil); Toma, Leny [Department of Biochemistry, Federal University of Sao Paulo, Sao Paulo (Brazil); Kalapothakis, Evanguedes [Department of Pharmacology, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais (Brazil); Chavez-Olortegui, Carlos [Department of Biochemistry and Immunology, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais (Brazil); Mangili, Oldemir Carlos [Department of Physiology, Federal University of Parana, Curitiba, Parana (Brazil); Gremski, Waldemiro [Department of Cell Biology, Federal University of Parana, Jardim das Americas, 81531-990, Curitiba, Parana (Brazil); Catholic University of Parana, Health and Biological Sciences Institute, Curitiba, Parana (Brazil); Dietrich, Carl Peter von [Department of Biochemistry, Federal University of Sao Paulo, Sao Paulo (Brazil); Nader, Helena B. [Department of Biochemistry, Federal University of Sao Paulo, Sao Paulo (Brazil); Sanches Veiga, Silvio [Department of Cell Biology, Federal University of Parana, Jardim das Americas, 81531-990, Curitiba, Parana (Brazil)]. E-mail: veigass@ufpr.br

2006-02-15

305

The Enterotoxicity of Clostridium difficile Toxins  

PubMed Central

The major virulence factors of Clostridium difficile infection (CDI) are two large exotoxins A (TcdA) and B (TcdB). However, our understanding of the specific roles of these toxins in CDI is still evolving. It is now accepted that both toxins are enterotoxic and proinflammatory in the human intestine. Both purified TcdA and TcdB are capable of inducing the pathophysiology of CDI, although most studies have focused on TcdA. C. difficile toxins exert a wide array of biological activities by acting directly on intestinal epithelial cells. Alternatively, the toxins may target immune cells and neurons once the intestinal epithelial barrier is disrupted. The toxins may also act indirectly by stimulating cells to produce chemokines, proinflammatory cytokines, neuropeptides and other neuroimmune signals. This review considers the mechanisms of TcdA- and TcdB-induced enterotoxicity, and recent developments in this field.

Sun, Xingmin; Savidge, Tor; Feng, Hanping

2010-01-01

306

Evaluation of synergism among Bacillus thuringiensis toxins.  

PubMed Central

A simple test for synergism among toxins is described and applied to previously reported data on independent and joint toxicities of insecticidal proteins from Bacillus thuringiensis. The analysis shows synergism between a 27-kDa (CytA) toxin and 130- or 65-kDa (CryIV) toxins from B. thuringiensis subsp. israelensis against Aedes aegypti larvae. No positive synergism between 130- and 65-kDa toxins or among three CryIA toxins tested against seven species of Lepidoptera occurred. Comparisons with the original interpretations of these data show one case in which synergism occurred but was reported previously as absent and two cases that were not synergistic but were reported previously as suggestive of synergism. These results show that lack of an appropriate test for synergism can produce misleading conclusions. The methods described here can be used to test for synergistic effects of any poisons.

Tabashnik, B E

1992-01-01

307

Crystallization of isoelectrically homogeneous cholera toxin  

SciTech Connect

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.

Spangler, B.D.; Westbrook, E.M. (Argonne National Laboratory, IL (USA))

1989-02-07

308

Immunotoxins: The Role of the Toxin  

PubMed Central

Immunotoxins are antibody-toxin bifunctional molecules that rely on intracellular toxin action to kill target cells. Target specificity is determined via the binding attributes of the chosen antibody. Mostly, but not exclusively, immunotoxins are purpose-built to kill cancer cells as part of novel treatment approaches. Other applications for immunotoxins include immune regulation and the treatment of viral or parasitic diseases. Here we discuss the utility of protein toxins, of both bacterial and plant origin, joined to antibodies for targeting cancer cells. Finally, while clinical goals are focused on the development of novel cancer treatments, much has been learned about toxin action and intracellular pathways. Thus toxins are considered both medicines for treating human disease and probes of cellular function.

Antignani, Antonella; FitzGerald, David

2013-01-01

309

Stealth and mimicry by deadly bacterial toxins.  

PubMed

Diphtheria toxin and exotoxin A are well-characterized members of the ADP-ribosyltransferase toxin family that function as virulence factors in the pathogenic bacteria Corynebacterium diphtheriae and Pseudomonas aeruginosa. Recent high-resolution structural data of the Michaelis (enzyme-substrate) complex of the P. aeruginosa toxin with an NAD(+) analog and eukaryotic elongation factor 2 (eEF2) have provided insights into the mechanism of inactivation of protein synthesis caused by these protein factors. In addition, rigorous steady-state and stopped-flow kinetic analyses of the toxin-catalyzed reaction, in combination with inhibitor studies, have resulted in a quantum leap in our understanding of the mechanistic details of this deadly enzyme mechanism. It is now apparent that these toxins use stealth and molecular mimicry in unleashing their toxic strategy in the infected host eukaryotic cell. PMID:16406634

Yates, Susan P; Jørgensen, René; Andersen, Gregers R; Merrill, A Rod

2006-02-01

310

Spontaneous oscillatory contractions in aortas of rats with arterial pressure lability caused by sinoaortic denervation.  

PubMed

1. The spontaneous variation of blood pressure is defined as arterial pressure lability. Sinoaortic denervation (SAD) is characterized by arterial pressure lability without sustained hypertension. 2. The phenomenon of spontaneous oscillatory contractions (SOCs) occurs more frequently in the vascular beds of hypertensive animals. In large arteries, such as the aorta, SOCs occur only occasionally or they can be initiated by application of chemical stimuli. 3. In the present study, we investigated whether the arterial pressure lability evoked by SAD could be related to the emergence of SOCs in the aorta of rats submitted to SAD compared with sham-operated rats (SO). Three days after surgery (SAD or SO), aortic rings were placed in an organ chamber and the incidence (percentage of rats presenting SOCs), frequency (number of SOCs in 10 min) and amplitude (mN) of SOCs were measured. The participation of external Ca(2+) and K(+) channels in the maintenance of SOCs was also verified. 4. The incidence and frequency of SOCs were higher in endothelium-denuded aortas from SAD rats (82% and 38 +/- 4 SOCs/10 min, respectively) than in aortas from SO rats (40% and 14 +/- 2 SOCs/10 min, respectively). In aortas from SAD rats, verapamil (0.2 micromol/L), pinacidil (0.3 micromol/L) and tetraethylammonium (TEA; 5 mmol/L) totally inhibited SOCs, whereas increasing the CaCl(2) concentration to 2.0 and 2.5 mmol/L increased the frequency of SOCs. Interestingly, increasing the concentration of CaCl(2) to 3.5 mmol/L inhibited these contractions in aortas from SAD rats. 5. These results show that although SAD rats did not become hypertensive, their aortas were capable of initiating SOCs without the application of any chemical stimuli. The SOCs seem to be dependent on Ca(2+) influx sensitive to verapamil and also involve K(+) channels sensitive to pinacidil and TEA. PMID:17600545

Rocha, Matheus L; Bendhack, Lusiane M

2007-08-01

311

DNA double-strand breaks and alkali-labile bonds produced by bleomycin.  

PubMed Central

Both in linear T2 DNA, analyyzed by velocity sedimentation, and in supercoiled Col EL DNA, analyzed by gel electrophoresis, the number of double-strand breaks produced by bleomycin was directly propotional to the number of single-strand breaks and was far greater than the number expected from random coincidence of single-strand breaks, suggesting that the bleomycin-induced double-strand breaks occur as an independent event. In Col EL DNA, at least twice as many single-strand breaks were found under alkaline assay conditions as were found under neutral conditions, showing the production of alkaline-labile bonds by bleomycin.

Povirk, L F; Wubter, W; Kohnlein, W; Hutchinson, F

1977-01-01

312

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

NASA Technical Reports Server (NTRS)

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.

Pizzarello, Sandra

1998-01-01

313

Stable and labile components of humus in soddy-podzolic soils  

NASA Astrophysics Data System (ADS)

A mathematical model was proposed to characterize the seasonal dynamics of the humus composition in loamy soddy-podzolic soils. The results of determining the composition of the organic matter during two successive seasons revealed the presence of labile and stable components in almost all the groups and fractions of the humic substances. The seasonal changes in the content of the humic substances, the exchangeable Ca, and the pH value at the equilibrium state of the soil were found to be identical during the successive years.

Drichko, V. F.; Bakina, L. G.; Orlova, N. E.

2013-01-01

314

Clostridium perfringens Delta Toxin Is Sequence Related to Beta Toxin, NetB, and Staphylococcus Pore-Forming Toxins, but Shows Functional Differences  

PubMed Central

Clostridium perfringens produces numerous toxins, which are responsible for severe diseases in man and animals. Delta toxin is one of the three hemolysins released by a number of C. perfringens type C and possibly type B strains. Delta toxin was characterized to be cytotoxic for cells expressing the ganglioside GM2 in their membrane. Here we report the genetic characterization of Delta toxin and its pore forming activity in lipid bilayers. Delta toxin consists of 318 amino acids, its 28 N-terminal amino acids corresponding to a signal peptide. The secreted Delta toxin (290 amino acids; 32619 Da) is a basic protein (pI 9.1) which shows a significant homology with C. perfringens Beta toxin (43% identity), with C. perfringens NetB (40% identity) and, to a lesser extent, with Staphylococcus aureus alpha toxin and leukotoxins. Recombinant Delta toxin showed a preference for binding to GM2, in contrast to Beta toxin, which did not bind to gangliosides. It is hemolytic for sheep red blood cells and cytotoxic for HeLa cells. In artificial diphytanoyl phosphatidylcholine membranes, Delta and Beta toxin formed channels. Conductance of the channels formed by Delta toxin, with a value of about 100 pS to more than 1 nS in 1 M KCl and a membrane potential of 20 mV, was higher than those formed by Beta toxin and their distribution was broader. The results of zero-current membrane potential measurements and single channel experiments suggest that Delta toxin forms slightly anion-selective channels, whereas the Beta toxin channels showed a preference for cations under the same conditions. C. perfringens Delta toxin shows a significant sequence homolgy with C. perfringens Beta and NetB toxins, as well as with S. aureus alpha hemolysin and leukotoxins, but exhibits different channel properties in lipid bilayers. In contrast to Beta toxin, Delta toxin recognizes GM2 as receptor and forms anion-selective channels.

Manich, Maria; Knapp, Oliver; Gibert, Maryse; Maier, Elke; Jolivet-Reynaud, Colette; Geny, Blandine; Benz, Roland; Popoff, Michel R.

2008-01-01

315

Toxins  

MedlinePLUS

... Acute poisoning. In: Goldman L, Schafer AI, eds. Cecil Medicine . 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011: ... and others. In: Goldman L, Schafer AI, eds. Cecil Medicine . 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011: ...

316

Relationship between the lability of sediment-bound metals (Cd, Cu, Zn) and their bioaccumulation in benthic invertebrates  

NASA Astrophysics Data System (ADS)

The present study has investigated metal contamination at nine sites (10 sampling stations) from the English Channel to the Mediterranean Sea, including low level and highly contaminated sediments. Both total and labile concentrations of metals were determined in superficial sediments. The influence of different pHs was tested and metal lability at pHs encountered in the gut of invertebrates (the ragworm Nereis diversicolor, the blue mussel Mytilus edulis, the Japanese oyster Crassostrea gigas) was compared with the distribution of metals in various operationally defined geochemical fractions. Cd showed the highest lability and Cu the lowest, whereas Zn lability was intermediate. Metal concentrations were determined in bivalves at six sites and in worms at three sites. Cd in living organisms and labile Cd in sediments increased in proportion over the gradient of contamination. This relationship did not always hold for Cu and Zn and these exceptions are discussed. Even if sediments are not the only source of metal contamination in marine invertebrates, the procedure proposed here to assess metal bioavailability by remobilising sediment-bound metals at physiological pHs, seems a significant improvement of the existing methodologies of risk assessment.

Amiard, J.-C.; Geffard, A.; Amiard-Triquet, C.; Crouzet, C.

2007-04-01

317

The effect of age on the accumulation of labile triosephosphate isomerase and thymidine incorporation in pokeweed mitogen stimulated human lymphocytes.  

PubMed

Peripheral lymphocytes from young persons were found to increase the content of labile triosephosphate isomerase (TPI) following pokeweed mitogen stimulation in vitro. The labile form appears to have the same thermal inactivation pattern as a tetradeamidated form of the enzyme previously shown to accumulate in fibroblasts and lymphoblasts. Human lymphocytes from an elderly sample were also subjected to mitogen stimulation under identical conditions. There was a greater accumulation of labile TPI during lymphoblast transformation in the aged sample. Cellular studies revealed that the absolute level of tritiated thymidine incorporated into DNA was significantly decreased with age in both resting and stimulated lymphocytes, but the blastogenic index showed no significant age-dependent changes. The ratio of the accumulation of labile enzyme during mitogen stimulation to the cellular blastogenic index was increased with age. The accumulation of labile forms of this enzyme may relate to the impairment of the energy-supplying glycolytic pathway that occurs in elderly human lymphocytes subjected to mitogenic stress. PMID:6736575

Tollefsbol, T O; Cohen, H J

1984-07-01

318

Evaluation of Insulin-Like Growth Factor Acid-Labile Subunit as a Potential Biomarker of Effect for Deoxynivalenol-Induced Proinflammatory Cytokine Expression  

PubMed Central

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.

Flannery, Brenna M.; Amuzie, Chidozie J.; Pestka, James J.

2013-01-01

319

Delayed haemolytic activity by the freshwater puffer Tetraodon sp. toxin  

Microsoft Academic Search

In order to elucidate the toxin composition of the freshwater puffer in Bangladesh, about 230 specimens of Tetraodon sp. were collected from 1997 to 1999 and extracted. After partitioning the toxins between an aqueous layer and a 1-butanol layer, the toxin in the aqueous layer was characterized as paralytic shellfish poison (PSP) (data not shown), while the toxin in the

S Taniyama; Y Mahmud; M. B Tanu; T Takatani; O Arakawa; T Noguchi

2001-01-01

320

Interplay between toxin transport and flotillin localization.  

PubMed

The flotillin proteins are localized in lipid domains at the plasma membrane as well as in intracellular compartments. In the present study, we examined the importance of flotillin-1 and flotillin-2 for the uptake and transport of the bacterial Shiga toxin (Stx) and the plant toxin ricin and we investigated whether toxin binding and uptake were associated with flotillin relocalization. We observed a toxin-induced redistribution of the flotillins, which seemed to be regulated in a p38-dependent manner. Our experiments provide no evidence for a changed endocytic uptake of Stx or ricin in cells silenced for flotillin-1 or -2. However, the Golgi-dependent sulfation of both toxins was significantly reduced in flotillin knockdown cells. Interestingly, when the transport of ricin to the ER was investigated, we obtained an increased mannosylation of ricin in flotillin-1 and flotillin-2 knockdown cells. The toxicity of both toxins was twofold increased in flotillin-depleted cells. Since BFA (Brefeldin A) inhibits the toxicity even in flotillin knockdown cells, the retrograde toxin transport is apparently still Golgi-dependent. Thus, flotillin proteins regulate and facilitate the retrograde transport of Stx and ricin. PMID:20107503

Pust, Sascha; Dyve, Anne Berit; Torgersen, Maria L; van Deurs, Bo; Sandvig, Kirsten

2010-01-01

321

[The pathogenesis features of ulcerative colitis and the pathogenetic theory of "toxin impairing intestine collateral"].  

PubMed

Ulcerative colitis (UC), a kind of chronic nonspecific intestinal inflammation with unknown etiology, is very difficult to cure. It recurs often and even is accompanied with parenteral lesion. It has been rated as one of contemporary refractory diseases by World Health Organization. The author combines the pathological mechanisms of UC with the poison-evil theory and the collateral disease theory, and puts forward that "toxin impairing intestine collateral" pathogenesis theory. We believe that longer accumulation of damp-heat stasis toxin that damages the intestine collateral is the key cause for recurrence and relapses of UC. We explained its theory foundation in terms of pathogenesis of UC from Chinese medicine and modern medicine. The "toxin impairing intestine collateral" theory might perfect the syndrome typing system for UC, and provide a new way of thinking for treating UC. PMID:23713262

Wang, Xin-yue; Yan, Xin

2013-03-01

322

A food-poisoning incident caused by Clostridium botulinum toxin A in Japan.  

PubMed Central

Food poisoning caused by Clostridium botulinum toxin A occurred in Japan. Eleven (31%) of 36 patients from 14 different areas died of botulism. Most of the patients had eaten commercial fried lotus-rhizome solid mustard without heating. The food, which implicated one of the special local products used for gifts in Kumamoto, was found to have been produced by a manufacturer in Kumamoto prefecture. In Fukuoka prefecture, two of three patients died on days 4 and 8 after eating the food; they had typical symptoms of botulism. A total of 42 packages of the food bought as gifts was collected from different districts in Fukuoka prefecture for examination for both organism and toxin. Thirteen of these (31%) were contaminated with the organism, and in 11 (26%) a small amount of toxin A had been produced.

Otofuji, T.; Tokiwa, H.; Takahashi, K.

1987-01-01

323

Elevated labile Cu is associated with oxidative pathology in Alzheimer disease.  

PubMed

Oxidative stress is implicated in Alzheimer disease (AD) pathogenesis, for which evidence indicates that radical species are generated by the redox-active biometal Cu. The contribution of labile Cu to the oxidative stress observed in AD has not been evaluated. The Cu content of postmortem cortical tissue from nondemented elderly controls and AD cases was measured using inductively coupled plasma mass spectroscopy, and the proportion of labile Cu was assessed using the Cu-phenanthroline assay. Further, the capacity of the tissue to stabilize Cu(2+) was evaluated using immobilized metal-affinity chromatography, and the level of tissue oxidative damage was determined by the presence of thiobarbituric acid-reactive compounds. We identified elevated levels of exchangeable Cu(2+), which were correlated with tissue oxidative damage; additionally, we noted an increased capacity of AD cortical tissue samples to bind Cu(2+). This deranged Cu homeostasis reflects the homeostatic breakdown of Cu observed in AD and supports biometal metabolism as a therapeutic target. PMID:22080049

James, Simon A; Volitakis, Irene; Adlard, Paul A; Duce, James A; Masters, Colin L; Cherny, Robert A; Bush, Ashley I

2012-01-15

324

Protective Effects of Dimethyl Sulfoxide on Labile Protein Interactions during Electrospray Ionization.  

PubMed

Electrospray ionization mass spectrometry is a valuable tool to probe noncovalent interactions. However, the integrity of the interactions in the gas-phase is heavily influenced by the ionization process. Investigating oligomerization and ligand binding of transthyretin (TTR) and the chaperone domain from prosurfactant protein C, we found that dimethyl sulfoxide (DMSO) can improve the stability of the noncovalent interactions during the electrospray process, both regarding ligand binding and the protein quaternary structure. Low amounts of DMSO can reduce in-source dissociation of native protein oligomers and their interactions with hydrophobic ligands, even under destabilizing conditions. We interpret the effects of DMSO as being derived from its enrichment in the electrospray droplets during evaporation. Protection of labile interactions can arise from the decrease in ion charges to reduce the contributions from Coulomb repulsions, as well as from the cooling effect of adduct dissociation. The protective effects of DMSO on labile protein interactions are an important property given its widespread use in protein analysis by electrospray ionization mass spectrometry (ESI-MS). PMID:24754426

Landreh, Michael; Alvelius, Gunvor; Johansson, Jan; Jörnvall, Hans

2014-05-01

325

Constraints on Transport and Emplacement Mechanisms of Labile Fractions in Lunar Cold Traps  

NASA Technical Reports Server (NTRS)

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.

Rickman, D.; Gertsch, L.

2014-01-01

326

Initiation, labile, and stabilization phases of experience-dependent plasticity at neocortical synapses.  

PubMed

Alteration of sensory input can change the strength of neocortical synapses. Selective activation of a subset of whiskers is sufficient to potentiate layer 4-layer 2/3 excitatory synapses in the mouse somatosensory (barrel) cortex, a process that is NMDAR dependent. By analyzing the time course of sensory-induced synaptic change, we have identified three distinct phases for synaptic strengthening in vivo. After an early, NMDAR-dependent phase where selective whisker activation is rapidly translated into increased synaptic strength, we identify a second phase where this potentiation is profoundly reduced by an input-specific, NMDAR-dependent depression. This labile phase is transient, lasting only a few hours, and may require ongoing sensory input for synaptic weakening. Residual synaptic strength is maintained in a third phase, the stabilization phase, which requires mGluR5 signaling. Identification of these three phases will facilitate a molecular dissection of the pathways that regulate synaptic lability and stabilization, and suggest potential approaches to modulate learning. PMID:23658185

Wen, Jing A; DeBlois, Mark C; Barth, Alison L

2013-05-01

327

Initiation, labile, and stabilization phases of experience-dependent plasticity at neocortical synapses  

PubMed Central

Alteration of sensory input can change the strength of neocortical synapses. Selective activation of a subset of whiskers is sufficient to potentiate layer 4-layer 2/3 excitatory synapses in the mouse somatosensory (barrel) cortex, a process that is NMDAR-dependent. By analyzing the time-course of sensory-induced synaptic change, we have identified three distinct phases for synaptic strengthening in vivo. After an early, NMDAR-dependent phase where selective whisker activation is rapidly translated into increased synaptic strength, we identify a second phase where this potentiation is profoundly reduced by an input-specific, NMDAR-dependent depression. This labile phase is transient, lasting only a few hours, and may require ongoing sensory input for synaptic weakening. Residual synaptic strength is maintained in a third phase, the stabilization phase, which requires mGluR5 signaling. Identification of these three phases will facilitate a molecular dissection of the pathways that regulate synaptic lability and stabilization, and suggest potential approaches to modulate learning.

Wen, Jing A.; DeBlois, Mark C.; Barth, Alison L.

2013-01-01

328

High rates of soil respiration suggest large fluxes of labile C in a turfgrass system  

NASA Astrophysics Data System (ADS)

We measured high rates of soil respiration (up to 19 ?mol C m-2 sec-1) in a study of management effects on turfgrass lawns. Estimates based on these measurements indicate that annual soil respiration is on the order of 15-30 Mg C ha-1, which seems high, given measured NPP of 3-6 Mg C ha-1 yr-1 and 0-10 cm soil C pools of 15-20 Mg C ha-1 which showed no net change over the study period. We contend that this flux is plausible, given irrigation and fertilizer applications, and hypothesize that in this context, soil respiration is driven largely by assimilate availability. We provide several lines of evidence supporting the idea that large fluxes of readily labile C move through this system: Biomass growth rates were highly correlated with soil respiration rates; we observed statistically significant variation in soil C stocks, dramatic changes in microbial biomass stoichiometry, and major shifts in N mineralization and nitrification over the course of a single growing season; and long-term soil incubations appear to show the accumulation and depletion of a substantial pool of labile C.

Lilly, P.; Jenkins, J. C.; Carroll, M.

2013-12-01

329

Determination of the Labile Iron Pool of Human Lymphocytes using the Fluorescent Probe, CP655  

PubMed Central

The present study introduces a method for determining the labile iron pool (LIP) in human lymphocytes. It is measured using the probe CP655, the fluorescence of which is stoichiometrically quenched by the addition of iron. The intracellular CP655 fluorescence in lymphocytes was quenched by increasing intracellular iron concentrations using the highly lipophilic 8-hydroxyquinoline iron complex. Intracellular fluorescence quenching, mediated by the physiological intracellular labile iron, can be recovered on the addition of excess membrane-permeable iron chelator, CP94. The intracellular probe concentration was measured using laser scanning microscopy. An ex situ calibration was performed in a “cytosolic” medium based on the determined intracellular CP655 concentration and probe fluorescence quenching in the presence of iron. The concentration of the LIP of healthy human lymphocytes was determined to be 0.57 ± 0.27 ?M. The use of the fluorescent probe CP655 renders it possible to record the time course of iron uptake and iron chelation by CP94 in single intact lymphocytes.

Ma, Yongmin; Liu, Zudong; Hider, Robert C; Petrat, Frank

2007-01-01

330

Tracing of labile zinc in live fish hepatocytes using FluoZin-3.  

PubMed

Intracellular zinc levels are homeostatically regulated and although most is bound, a pool of labile Zn(II) is present in cells. We show here that the zinc probe FluoZin-3 is useful to monitor zinc fluxes during fluorescent imaging of the trout hepatic cell line D11. Nuclei and bulk cytosol appeared to lack detectable labile zinc, while the punctuate staining pattern colocalized with a lysosome-specific probe. Applying extracellular zinc alone resulted in vesicular sequestration of the metal ion. Together with Na-pyrithione a delayed and toxic rise in cellular fluorescence was triggered. When using another ionophore, 4-Br A23187, a zinc buffering effect of the vesicular pools was evident. Secondly, N-ethylmaleimide induced a homogeneous fluorescence rise, which was strongly enhanced by addition of Zn-pyrithione and disappeared after TPEN washing. This suggests the involvement of thiol residues in controlling available cytosolic zinc. Our observations have implications for the interpretation of calculated intracellular Zn2+ concentrations. PMID:16841253

Muylle, Frederik A R; Adriaensen, Dirk; De Coen, Wim; Timmermans, Jean-Pierre; Blust, Ronny

2006-08-01

331

Multivariate Statistical Analysis of Labile Trace Elements in H Chondrites: Evidence for Meteoroid Streams  

NASA Astrophysics Data System (ADS)

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 logistic regression statistical techniques as tools for discriminant analysis. A randomization-simulation technique can also be used to make distribution-independent comparisons and to verify that any observed differences are not due to insufficient samples or too many independent variables (Lipschutz and Samuels, 1991). These methods allow us to test for the existence of distinct compositional subpopulations in what is supposedly a single meteorite population. At the time of writing this abstract our database consists of 55 H4-6 chondrites (Lingner et al, 1987 and this work). Nine of these meteorites are members of the proposed "cluster 1" co-orbital meteoroid stream. For these 9 samples, linear discriminant analysis based on the concentrations of 10 labile trace elements reveals a difference between the "cluster 1" subpopulation of H chondrite falls and all other H chondrite falls at the <0.03 significance level. Logistic regression reveals a difference at the <0.0001 significance level. Normalization of data to Allende standard meteorite reference standard to eliminate bias conceivably due to different analysts yields results comparable to results from the non-normalized data. Additional evidence for the absence of interanalyst bias is provided by data of samples from Victoria Land, Antarctica: random populations analyzed by the present authors (Wolf and Lipschutz, 1992) are statistically indistinguishable from populations analyzed previously (Dennison and Lipschutz, 1987). A logistic regression validation run also supports the lack of interanalyst bias. Results from linear discriminant analysis, and logistic regression randomization-simulations will be presented in Copenhagen. These results on a limited population, which may be expanded by meeting time demonstrate that the "cluster 1" subpopulation of H chondrite falls are distinguishable from all other H chondrite falls on the basis of their labile trace elements, a result that is consistent with the idea that these meteorites had a common thermal history and were assoc

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

1992-07-01

332

Cu lability and bioavailability in an urban stream during baseflow versus stormflow  

NASA Astrophysics Data System (ADS)

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 ?g/L, and 0.9 to 5.1 ?g/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 concentrations, and that percentage increased in the days following a storm, suggesting more labile Cu compounds remained in the water column longer. Whereas solution metal concentrations in stormwater influenced reaches did not largely change upstream versus downstream, concentrations of Cu in periphyton cultures increased 2-fold downstream of a stormwater input. This is likely due to differences in discrete sampling locations, but indicates the potential importance of resuspended sediment on enhancing metal bioavailability. These results suggest that legacy sediment contamination is contributing to water column Cu concentrations. Downstream Cu concentrations are elevated compared to near the wastewater treatment plant effluent but are mostly unchanged before and after stormwater inputs. In addition, DGT concentrations indicate a shift in percentage of labile metals, in part distinguished based on size exclusion by the DGT device, following a storm event. As total dissolved Cu concentration decreases, labile Cu increases likely due to settling or size dependent partitioning to the solid phases such as periphyton. Understanding the transport and bioavailability of size dependent Cu compounds in stream water is important to allocating resources to mitigate metal contamination.

Vadas, T.; Luan, H.

2012-12-01

333

Retrograde transport of protein toxins through the Golgi apparatus.  

PubMed

A number of protein toxins from plants and bacteria take advantage of transport through the Golgi apparatus to gain entry into the cytosol where they exert their action. These toxins include the plant toxin ricin, the bacterial Shiga toxins, and cholera toxin. Such toxins bind to lipids or proteins at the cell surface, and they are endocytosed both by clathrin-dependent and clathrin-independent mechanisms. Sorting to the Golgi and retrograde transport to the endoplasmic reticulum (ER) are common to these toxins, but the exact mechanisms turn out to be toxin and cell-type dependent. In the ER, the enzymatically active part is released and then transported into the cytosol, exploiting components of the ER-associated degradation system. In this review, we will discuss transport of different protein toxins, but we will focus on factors involved in entry and sorting of ricin and Shiga toxin into and through the Golgi apparatus. PMID:23765164

Sandvig, Kirsten; Skotland, Tore; van Deurs, Bo; Klokk, Tove Irene

2013-09-01

334

Toxin-induced cardiovascular failure.  

PubMed

Adverse cardiovascular events comprise a large portion of the morbidity and mortality in drug overdose emergencies. Adverse cardiovascular events encountered by emergency physicians treating poisoned patients include myocardial injury, hemodynamic compromise with shock, tachydysrhythmias, and cardiac arrest. Early signs of toxin-induced cardiovascular failure include bradycardia, tachycardia, and specific ECG findings. Treatment of toxicologic tachycardia relies on rapid supportive care along with proper use of benzodiazepines for sedation. Treatment of toxicologic bradycardia consists of the use of isotonic fluids, atropine, calcium salts, and glucagon. High-dose insulin euglycemia should be used early in the course of suspected severe poisoning and intravenous lipid emulsion given to patients who suffer cardiac arrest. PMID:24275170

Jang, David H; Spyres, Meghan B; Fox, Lindsay; Manini, Alex F

2014-02-01

335

Tetanus toxin blocks the neuromuscular transmission in vitro like botulinum a toxin  

Microsoft Academic Search

1.The blocking effect of tetanus toxin on the neuromuscular junction of the mouse phrenic nervehemidiaphragm preparation exposed to the toxin (0.05–20 µg\\/ml) in the organ bath was studied and compared with the action of botulinum A toxin.2.The time course of the paralysis of the diaphragm could be divided into a latent and a manifest period. Still during the latent period

E. Habermann; F. Dreyer; H. Bigalke

1980-01-01

336

Isogenic Lysogens of Diverse Shiga Toxin 2Encoding Bacteriophages Produce Markedly Different Amounts of Shiga Toxin  

Microsoft Academic Search

We produced isogenic Escherichia coli K-12 lysogens of seven different Shiga toxin 2 (Stx2)-encoding bacteriophages derived from clinical Shiga toxin-producing E. coli (STEC) isolates of serotypes O157:H7, O145, O111, and O83 to assess the variability among these phages and determine if there were phage-related differences in toxin production. Phage genomic restriction fragment length polymorphisms (RFLP) and superinfection resistance studies revealed

PATRICK L. WAGNER; DAVID W. K. ACHESON; MATTHEW K. WALDOR

1999-01-01

337

Assessment of the labile fractions of copper and zinc in marinas and port areas in Southern Brazil.  

PubMed

The dissolved labile and labile particulate fractions (LPF) of Cu and Zn were analyzed during different seasons and salinity conditions in estuarine waters of marina, port, and shipyard areas in the southern region of the Patos Lagoon (RS, Brazil). The dissolved labile concentration was determined using the diffusive gradients in thin films technique (DGT). DGT devices were deployed in seven locations of the estuary for 72 h and the physicochemical parameters were also measured. The LPF of Cu and Zn was determined by daily filtering of water samples. Seasonal variation of DGT-Cu concentrations was only significant (p?labile Cu and Zn in both fractions. Strong relationship between DGT-Zn and LPF-Zn was found suggesting that the DGT-Zn fraction originates from the suspended particulate matter. Water salinity and suspended particulate matter content indicated their importance for the control of the labile concentrations of Cu and Zn in the water column. These parameters must be taken into consideration for comparison among labile metals in estuaries. PMID:23475526

Costa, Luiza Dy Fonseca; Wallner-Kersanach, Mônica

2013-08-01

338

The interactions of human neutrophils with shiga toxins and related plant toxins: danger or safety?  

PubMed

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

Brigotti, Maurizio

2012-03-01

339

Sources, lability and solubility of Pb in alluvial soils of the River Trent catchment, U.K.  

PubMed

Alluvial soils are reservoirs of metal contaminants such as Pb that originate from many different sources and are integrated temporally and spatially through erosional and depositional processes. In this study the source, lability and solubility of Pb were examined in a range of alluvial soils from the middle and lower River Trent and its tributary the River Dove using Pb isotope apportionment and isotopic dilution. All samples were collected within 10 m of the river bank to represent the soil that is most likely to be remobilised during bank erosion. Paired samples were taken from the topsoil (0-15 cm) and subsoil (35-50 cm) to assess differences with depth. Lead concentrations in soil ranged from 43 to 1282 mg/kg. The lability of soil Pb varied between 9 and 56% of total metal concentration whilst Pb concentrations in pore water varied between 0.2 and 6.5 ?g/L. There was little difference in the % Pb lability between paired top and sub soils, possibly because soil characteristics such as pH, iron oxides and clay content were generally similar; a result of the recycling of eroded and deposited soils within the river system. Soil pH was found to be negatively correlated with % Pb lability. Source apportionment using (206)Pb/(207)Pb and (208)Pb/(207)Pb ratios showed that the isotopic ratios of Pb in the total, labile and solution pools fitted along a mixing line between Broken Hill Type ('BHT') Pb, used as an additive in UK petrol, and the local coal/Southern Pennine ore Pb. Various anomalies were found in the Pb isotopes of the bankside alluvial soils which were explained by point source pollution. Statistically significant differences were found between (i) the isotopic composition of Pb in the total soil pool and the labile/solution pools and (ii) the isotopic composition of Pb in the labile and solution pools, suggesting an enrichment of recent non-Pennine sources of Pb entering the soils in the labile and solution pools. PMID:22771468

Izquierdo, M; Tye, A M; Chenery, S R

2012-09-01

340

Mechanism of Action of Tetanus Toxin.  

National Technical Information Service (NTIS)

The authors examined an in vivo system to explore whether protein kinase C (PKC) activity is diminished when animals become intoxicated with tetanus toxin (TT). Homogenates of brain and spinal cord from mice manifesting generalized tetanus after receiving...

M. S. Klempner

1988-01-01

341

Mechanism of Action of Tetanus Toxin.  

National Technical Information Service (NTIS)

The mechanism by which tetanus toxin (TT) inhibits the release of neurotransmitters from neurons is unknown. Since secretion of lysosomal contents from monocytes/macrophages (MOs) appears to be similar to neurosecretion, the authors examined the effects o...

M. S. Klempner

1986-01-01

342

[Botulinum toxin in disabling dermatological diseases].  

PubMed

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

Messikh, R; Atallah, L; Aubin, F; Humbert, P

2009-05-01

343

Vaccines against Clostridium perfringens alpha-toxin.  

PubMed

Clostridium perfringens alpha-toxin is thought to be an important agent in gas gangrene, which is a lifethreatening infection with fever, pain, edema, myonecrosis, and gas production. The toxin (370 residues) is composed of an N-terminal domain (1-250 residues, N-domain) in which the catalytic site is found and a C-terminal domain (251-370 residues, C-domain) responsible for binding to membranes. During the past decade, recombinant DNA technology has been employed to develop second-generation vaccines, including site-directed mutants and the C-domain of the toxin, to prevent gas gangrene. These immunities have led to protection against the lethal effects of wild-type C. perfringens in mice. C-domain vaccines are capable of protecting against heterologous clostridia causing clostridial myonecrosis. This article summarizes the current knowledge on vaccines against alpha-toxin. PMID:24372250

Nagahama, Masahiro

2014-11-01

344

Metabolism of the cyclic peptide HC-toxin, a host-specific toxin, by resistant (R) and susceptible (S) maize  

Microsoft Academic Search

Cochliobolus carbonum (race 1) and the toxin it produces, HC-toxin, affect only maize that is homozygous recessive at the nuclear locus, Hm. Radiolabeled HC-toxin was purified after controlled feeding of D,L-(³H)-alanine to the fungus and used to study metabolism as a basis for its host-selectivity. A single HC-toxin metabolite was recovered from maize leaves exposed to (³H)-HC-toxin. The 8-keto group

R. Meeley; J. D. Walton

1990-01-01

345

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

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.

Gill, D.M.; Coburn, J.

1987-10-06

346

Alpine grassland soils contain large proportion of labile carbon but indicate long turnover times  

NASA Astrophysics Data System (ADS)

Alpine soils are expected to contain large amounts of labile carbon (C) which may become a further source of atmospheric carbon dioxide (CO2) as a result of global warming. However, there is little data available on these soils, and understanding of the influence of environmental factors on soil organic matter (SOM) turnover is limited. We extracted 30 cm deep cores from five grassland sites along a small elevation gradient from 2285 to 2653 m a.s.l. in the central Swiss Alps. Our aim was to determine the quantity, allocation, degree of stabilization and mean residence time (MRT) of SOM in relation to site factors such as soil pH, vegetation, and SOM composition. Soil fractions obtained by size and density fractionation revealed a high proportion of labile C in SOM, mostly in the uppermost soil layers. Labile C in the top 20 cm across the gradient ranged from 39.6-57.6 % in comparison to 7.2-29.6 % reported in previous studies for lower elevation soils (810-1960 m a.s.l.). At the highest elevation, MRTs measured by means of radiocarbon dating and turnover modelling, increased between fractions of growing stability from 90 years in free POM (fPOM) to 534 years in the mineral associated fraction (mOM). Depending on elevation and pH, plant community data suggested considerable variation in the quantity and quality of organic matter input, and these patterns could be reflected in the dynamics of soil C. 13C NMR data confirmed a relationship of SOM composition to MRT. While low temperature in alpine environments is likely to be a major cause for the slow turnover rate observed, other factors such as residue quality and soil pH, as well as the combination of all factors, play an important role in causing small scale variability of SOM turnover. Failing to incorporate this interplay of controlling factors into models may impair the performance of models to project SOM responses to environmental change.

Budge, K.; Leifeld, J.; Hiltbrunner, E.; Fuhrer, J.

2011-07-01

347

14C as a tracer of labile organic matter in Antarctic benthic food webs  

NASA Astrophysics Data System (ADS)

14C measurements were made on surface plankton, particle-trap material, surface sediment, benthic invertebrate gut contents, and body tissue samples to assess the effectiveness of this radioisotope as a tracer of labile organic carbon in Antarctic benthic food webs. Samples were collected on five cruises to the West Antarctic Peninsula (WAP) shelf between November 1999 and March 2001 as part of the Food for Benthos on the ANtarctic Continental-Shelf (FOODBANCS) Project. The 14C contents of the body tissues from a variety of deposit feeders (-126±13 per mil) were substantially enriched relative to the surface sediment (-234±13 per mil) and statistically similar to the organic matter collected in plankton tows (-135±10 per mil), indicating that recently produced marine plankton are the primary source of nutrition for these deposit feeders on the West Antarctic shelf. Selective ingestion was the primary feeding strategy used by echiuran worms and certain holothurians (i.e. Peniagone vignoni) for incorporating labile organic carbon into their tissues as demonstrated by the large differences (105±13 per mil) between surface sediment and gut content 14C activities. In contrast, digestive and/or assimilatory selection was the predominant strategy used by an irregular urchin ( Amphipneustes lorioli) and several other holothurians ( Protelpidia murrayi, Bathyplotes fuscivinculum and the head-down conveyor belt feeder, Molpadia musculus), as demonstrated by large differences (42±7 per mil) between the 14C activities of their foregut or whole-gut organic contents and their body tissues. Despite large fluctuations in carbon export from the euphotic zone, benthic feeding strategies remained essentially constant over the 15-month sampling period. No seasonal variation was evident in either the 14C abundance of the deposit-feeder body tissues, or in the 14C abundance of their gut contents. The mean 14C abundance in the body tissues of the two sub-surface deposit feeders ( A. lorioli and M. musculus; mean=-136.2±8.5 per mil) was distinct ( p=0.0008) from the mean 14C abundance in the body tissues of the four surface deposit feeders (echiuran worm, P. vignoni, P. murrayi, and B. fusciviculum; -122.6±12.3 per mil). The mean 14C abundance of the gut contents from the sub-surface deposit feeders (-178.0±18.6 per mil) also was significantly depleted ( p=0.0009) relative to that of the surface deposit feeders (-149.5±26.6 per mil). The 14C measurements proved to be a much more sensitive tracer for tracking labile organic carbon during ingestive and assimilatory processes than the stable isotopes of carbon or nitrogen.

Purinton, Brett L.; DeMaster, David J.; Thomas, Carrie J.; Smith, Craig R.

2008-11-01

348

Sea Anemone Toxins Affecting Potassium Channels  

NASA Astrophysics Data System (ADS)

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.

Diochot, Sylvie; Lazdunski, Michel

349

Calcium-labile mitotic spindles isolated from sea urchin eggs (Lytechinus variegatus)  

Microsoft Academic Search

ABSTRACT ? We,isolatedcalcium-labile,mitotic,spindles,from,eggs,of the sea,urchin,Lytechinus variegatus,using a low ionic strength,EGTA lysisbuffer that contained 5.0 mM EGTA, 0.5mM M9Cl 2, 10-50 mM PIPES, pH 6.8,with 1% Nonidet P-40 (detergent) and 20-25% glycerol. Isolatedspindles,were,stored,in EGTA buffer,with,50% glycerolfor5-6 wk,without,deterioration. The isolated spindles were composed,primarily of microtubules with the chromosomes,at- tached .No membranes were seen .Isolatedspindles,perfused with EGTA buffer to remove the detergent and

E. D. Salmon; R. r. segall

1980-01-01

350

[Concept of labile protein and the adaptation of nitrogen metabolism in protein deficiency in man].  

PubMed

Investigations involving 30 healthy males, who for 45 days consumed standard semisynthetic diets differing in the caseine content (from 0 to 15.1 g of nitrogen per day) and serving as a sole source of protein, furnished data on the nitrogen excretion kinetics and nitrogen balance. Mathematical analysis of these data allowed it to find the existence of general regularity in the nitrogen excretion and to deduce an integral equation of its losses at different levels of nitrogen consumption. Pertinent calculations have ascertained that by the labile protein one should understand not the specific proportion of the total protein in the organism, but the actual rate of its metabolism, manifesting itself in the routine lag-phase during adaptation of the nitrogen metabolism to a new level of the protein allowances in the organism. The data thus made available permitted it, at the same time, to propose a criterion for estimating the optimal requirements of man in proteins. PMID:1021987

Vysotski?, V G; Sokolov, V N; Iatsyshina, T A

1976-01-01

351

Effect of temperature on the decomposition rate of labile and stable organic matter in an agrochernozem  

NASA Astrophysics Data System (ADS)

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.

Larionova, A. A.; Kvitkina, A. K.; Yevdokimov, I. V.; Bykhovets, S. S.; Stulin, A. F.

2014-05-01

352

High lability of sexual system over 250 million years of evolution in morphologically conservative tadpole shrimps  

PubMed Central

Background Sexual system is a key factor affecting the genetic diversity, population structure, genome structure and the evolutionary potential of species. The sexual system androdioecy – where males and hermaphrodites coexist in populations – is extremely rare, yet is found in three crustacean groups, barnacles, a genus of clam shrimps Eulimnadia, and in the order Notostraca, the tadpole shrimps. In the ancient crustacean order Notostraca, high morphological conservatism contrasts with a wide diversity of sexual systems, including androdioecy. An understanding of the evolution of sexual systems in this group has been hampered by poor phylogenetic resolution and confounded by the widespread occurrence of cryptic species. Here we use a multigene supermatrix for 30 taxa to produce a comprehensive phylogenetic reconstruction of Notostraca. Based on this phylogenetic reconstruction we use character mapping techniques to investigate the evolution of sexual systems. We also tested the hypothesis that reproductive assurance has driven the evolution of androdioecy in Notostraca. Results Character mapping analysis showed that sexual system is an extremely flexible trait within Notostraca, with repeated shifts between gonochorism and androdioecy, the latter having evolved a minimum of five times. In agreement with the reproductive assurance hypothesis androdioecious notostracans are found at significantly higher latitudes than gonochoric ones indicating that post glacial re-colonisation may have selected for the higher colonisation ability conferred by androdioecy. Conclusions In contrast to their conserved morphology, sexual system in Notostraca is highly labile and the rare reproductive mode androdioecy has evolved repeatedly within the order. Furthermore, we conclude that this lability of sexual system has been maintained for at least 250 million years and may have contributed to the long term evolutionary persistence of Notostraca. Our results further our understanding of the evolution of androdioecy and indicate that reproductive assurance is a recurrent theme involved in the evolution of this sexual system.

2013-01-01

353

In vivo lability of glucose-6-phosphate dehydrogenase in GdA- and Gdmediterranean deficiency  

PubMed Central

A decreased level of glucose-6-phosphate dehydrogenase might result from decreased rate of synthesis, synthesis of an enzyme of lower catalytic efficiency, increased lability, or a combined mechanism. To test the hypothesis of increased lability, the rate of decline of the enzyme in vivo was measured in three groups of individuals, controls, Gd(—),A-males, and Gd(—), Mediterranean males, by the slope of decline of activity in fractions containing erythrocytes of progressively increasing mean age. These fractions were obtained by ultracentrifugation on a discontinuous density gradient of erythrocyte suspensions free of contaminating platelets and leukocytes. The rate of in vivo decline of pyruvate kinase (another age-dependent enzyme) was also measured and found very similar in the three groups. The in vivo decline of glucose-6-phosphate dehydrogenase was found to follow an exponential rate, with a half-life of 62 days for controls and 13 days for Gd(—),A- erythrocytes. The activity in normal reticulocytes was estimated at 9.7 U and in Gd(—),A- reticulocytes at 8.8 U. These estimates were confirmed by direct measurements in reticulocytes isolated from patients with extreme reticulocytosis. In Gd(—),Mediterranean erythrocytes activity could be demonstrated only in reticulocytes, which were estimated to average 1.4 U. The rate of decline is so extreme that no activity could be detected in mature erythrocytes. These data suggest that the glucose-6-phosphate dehydrogenase deficiency of both the GdA- and the GdMediterranean variant results from different degrees of in vivo instability of the abnormal enzyme.

Piomelli, Sergio; Corash, Laurence M.; Davenport, Deatra D.; Miraglia, Janet; Amorosi, Edward L.

1968-01-01

354

The labile iron pool: characterization, measurement, and participation in cellular processes(1).  

PubMed

The cellular labile iron pool (LIP) is a pool of chelatable and redox-active iron, which is transitory and serves as a crossroad of cell iron metabolism. Various attempts have been made to analyze the levels of LIP following cell disruption. The chemical identity of this pool has remained poorly characterized due to the multiplicity of iron ligands present in cells. However, the levels of LIP recently have been assessed with novel nondisruptive techniques that rely on the application of fluorescent metalosensors. Methodologically, a fluorescent chelator loaded into living cells binds to components of the LIP and undergoes stoichiometric fluorescence quenching. The latter is revealed and quantified in situ by addition of strong permeating iron chelators. Depending on the intracellular distribution of the sensing and chelating probes, LIP can be differentially traced in subcellular structures, allowing the dynamic assessment of its levels and roles in specific cell compartments. The labile nature of LIP was also revealed by its capacity to promote formation of reactive oxygen species (ROS), whether from endogenous or exogenous redox-active sources. LIP and ROS levels were shown to follow similar "rise and fall" patterns as a result of changes in iron import vs. iron chelation or ferritin (FT) degradation vs. ferritin synthesis. Those patterns conform with the accepted role of LIP as a self-regulatory pool that is sensed by cytosolic iron regulatory proteins (IRPs) and feedback regulated by IRP-dependent expression of iron import and storage machineries. However, LIP can also be modulated by biochemical mechanisms that override the IRP regulatory loops and, thereby, contribute to basic cellular functions. This review deals with novel methodologies for assessing cellular LIP and with recent studies in which changes in LIP and ROS levels played a determining role in cellular processes. PMID:12374615

Kakhlon, Or; Cabantchik, Z Ioav

2002-10-15

355

Are DNA-based vaccines useful for protection against secreted bacterial toxins? Tetanus toxin test case  

Microsoft Academic Search

Polypeptide and DNA vaccine alternatives to the conventional tetanus toxoid were compared. Mouse immunizations with plasmid DNA that encoded the tetanus toxin C fragment polypeptide induced consistently lower antibody responses than direct immunization with the C fragment polypeptide or toxoid, yet provided some degree of protection from a lethal toxin challenge. Cytotoxic T-cell responses dominated DNA immunizations, while specific T-cell

Kamal U. Saikh; Julie Sesno; Patricia Brandler; Robert G. Ulrich

1998-01-01

356

Exposure to anthrax toxin alters human leucocyte expression of anthrax toxin receptor 1  

PubMed Central

Anthrax is a toxin-mediated disease, the lethal effects of which are initiated by the binding of protective antigen (PA) with one of three reported cell surface toxin receptors (ANTXR). Receptor binding has been shown to influence host susceptibility to the toxins. Despite this crucial role for ANTXR in the outcome of disease, and the reported immunomodulatory consequence of the anthrax toxins during infection, little is known about ANTXR expression on human leucocytes. We characterized the expression levels of ANTXR1 (TEM8) on human leucocytes using flow cytometry. In order to assess the effect of prior toxin exposure on ANTXR1 expression levels, leucocytes from individuals with no known exposure, those exposed to toxin through vaccination and convalescent individuals were analysed. Donors could be defined as either ‘low’ or ‘high’ expressers based on the percentage of ANTXR1-positive monocytes detected. Previous exposure to toxins appears to modulate ANTXR1 expression, exposure through active infection being associated with lower receptor expression. A significant correlation between low receptor expression and high anthrax toxin-specific interferon (IFN)-? responses was observed in previously infected individuals. We propose that there is an attenuation of ANTXR1 expression post-infection which may be a protective mechanism that has evolved to prevent reinfection.

Ingram, R J; Harris, A; Ascough, S; Metan, G; Doganay, M; Ballie, L; Williamson, E D; Dyson, H; Robinson, J H; Sriskandan, S; Altmann, D M

2013-01-01

357

Identification of shiga toxin-producing bacteria by a new immuno-capture toxin gene PCR  

Microsoft Academic Search

Infections with bacteria producing shiga toxin are responsible for widespread disease and for the death of a large number of people. In the present study, we have developed a rapid method of high specificity for the detection of Shigella dysenteriae by combining immuno-capture of the bacteria and polymerase chain reaction (PCR) amplification of their toxin gene. We compared the sensitivity

Wen Luo; Sanying Wang; Xuanxian Peng

2002-01-01

358

Lability of Cd, Cu, and Zn in polluted soils treated with lime, beringite, and red mud and identification of a non-labile colloidal fraction of metals using istopic techniques.  

PubMed

The use of soil amendments has been proposed as a low input alternative for the remediation of metal polluted soils. However, little information is available concerning the stability, and therefore the longevity, of the remediation treatments when important soil parameters change. In this paper we investigate the effect of pH changes on the lability of heavy metals in soils treated with lime, beringite, and red mud using a modified isotopic dilution technique in combination with a stepwise acidification procedure. Significant amounts of nonlabile (fixed) Cu and Zn were found to be associated with colloids <0.2 microm in the solution phase. The results obtained indicated that the mobility of fixed colloidal metals is significant and increases with soil pH. This must be considered because most of the soil amendments are alkaline and increase soil pH. All the soil amendments significantly decreased the lability of Cd, Zn, and Cu in the soils as a whole. However, when the soils were re-acidified, the labile pool of metals increased sharply and in the case of lime and beringite, the lability of the metals was similar, at equal pH, to the untreated soil. In contrast the lability of metals in the red mud treated soils was always smaller than that in the untreated soils across the range of pH values tested. These results suggest that the mechanism of action of lime and beringite is similar and probably related to increased metal adsorption and precipitation of metal hydroxides and carbonates at high pH. In the case of red mud, a combination of pH dependent and independent mechanisms (possibly solid-phase diffusion or migration into micropores) may be responsible for the metal fixation observed. PMID:12666929

Lombi, Enzo; Hamon, Rebecca E; McGrath, Steve P; McLaughlin, Mike J

2003-03-01

359

An anaerobic incubation study of metal lability in drinking water treatment residue with implications for practical reuse.  

PubMed

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. PMID:24813662

Wang, Changhui; Yuan, Nannan; Pei, Yuansheng

2014-06-15

360

Predicting the activity of Cd 2+ and Zn 2+ in soil pore water from the radio-labile metal fraction  

Microsoft Academic Search

Cadmium and zinc were added at 3 and 300 mg kg?1, respectively, to 23 soils and incubated at 16°C and 80% field capacity for 818 d. Following addition of metal, changes in the radio-labile concentrations of both elements were examined on seven separate sampling occasions over 818 d. At each sample time, soil pore water was extracted using Rhizon soil

A. M Tye; S. D Young; N. M. J Crout; H. Zhang; S. Preston; V. L Barbosa-Jefferson; W. Davison; S. P McGrath; G. I. Paton; K. Kilham; L. Resende

2003-01-01

361

Comparison of two experimental speciation methods with a theoretical approach to monitor free and labile Cd fractions in soil solutions  

Microsoft Academic Search

This work focused on the suitability of two techniques to monitor cadmium speciation in soil solutions collected during a 7-day incubation of a contaminated soil. Anodic stripping voltammetry (ASV) and ion exchange were performed on soil solutions collected daily and results were compared with calculations obtained with the speciation software Visual MINTEQ. The electrochemically labile Cd fraction was greater than

C. Parat; J.-Y. Cornu; A. Schneider; L. Authier; V. Sapin-Didier; L. Denaix; M. Potin-Gautier

2009-01-01

362

Emotional Lability in Children and Adolescents with Attention Deficit/Hyperactivity Disorder (ADHD): Clinical Correlates and Familial Prevalence  

ERIC Educational Resources Information Center

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…

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

363

Effects of phosphate buffer capacity on critical levels and relationships between soil tests and labile phosphate in wheat growing soils  

Microsoft Academic Search

Thirty-nine soils from northern New South Wales were used to examine the effects of phosphate buffer capacity on (i) the extraction of labile phosphate by four soil tests, (ii) the relationships between the four soil tests, and (iii) the critical level of each soil test required for near-maximum yield of wheat under field conditions. The results confirmed the principle, recently

I. C. R. Holford

1980-01-01

364

Thermal Analysis of Labile Trace Elements in CM and CV Carbonaceous Chondrites Using Inductively Coupled Plasma-Mass Spectrometry  

NASA Technical Reports Server (NTRS)

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.

Lauretta, D. S.; Klaue, B.; Blum, J. D.; Buseck, P. R.

2001-01-01

365

A Longitudinal Study of Emotion Regulation, Emotion Lability-Negativity, and Internalizing Symptomatology in Maltreated and Nonmaltreated Children  

ERIC Educational Resources Information Center

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…

Kim-Spoon, Jungmeen; Cicchetti, Dante; Rogosch, Fred A.

2013-01-01

366

[Labile blood products from donors immunized against the HLA system. Apropos of a case of transfusional pulmonary edema].  

PubMed

A case of transfusion-related acute lung injury (TRALI) due to HLA antibodies present in one unit of packed red blood cells led us to discuss the screening of HLA antibodies for female donors having been pregnant, and the use of labile blood products. PMID:9894328

Fruchart, M F; Belhocine, R; Klaren, J; Ben Hadj Amor, H; Fretz, C

1998-12-01

367

Animal Toxins: How is Complexity Represented in Databases?  

PubMed Central

Peptide toxins synthesized by venomous animals have been extensively studied in the last decades. To be useful to the scientific community, this knowledge has been stored, annotated and made easy to retrieve by several databases. The aim of this article is to present what type of information users can access from each database. ArachnoServer and ConoServer focus on spider toxins and cone snail toxins, respectively. UniProtKB, a generalist protein knowledgebase, has an animal toxin-dedicated annotation program that includes toxins from all venomous animals. Finally, the ATDB metadatabase compiles data and annotations from other databases and provides toxin ontology.

Jungo, Florence; Estreicher, Anne; Bairoch, Amos; Bougueleret, Lydie; Xenarios, Ioannis

2010-01-01

368

[Production and characteristics of monoclonal antibodies to the diphtheria toxin].  

PubMed

Monoclonal antibodies to the diphtheria toxin were produced without cross reactivity with the thermolabile toxin (LT) from Escherichia coli; ricin; choleraic toxin; the SeA, SeB, SeE, SeI, and SeG toxins of staphylococcus; the lethal factor of the anthrax toxin; and the protective antigen of the anthrax toxin. A pair of antibodies for the quantitative determination of the diphtheria toxin in the sandwich variation of enzyme-linked immunosorbent assay (ELISA) was chosen. The determination limit of the toxin was 0.7 ng/ml in plate and 1.6 ng/ml in microchip ELISA. The presence of a secretion from the nasopharynx lavage did not decrease the sensitivity of the toxin determination by sandwich ELISA. The immunization of mice with the diphtheria toxin and with a conjugate of the diphtheria toxin with polystyrene microspheres demonstrated that the conjugate immunization resulted in the formation of hybridoma clones which produced antibodies only to the epitopes of the A fragment of the diphtheria toxin. The immunization with the native toxin caused the production of hybridoma clones which predominantly produced antibodies to the epitopes of the B fragment. PMID:19915639

Valiakina, T I; Lakhtina, O E; Komaleva, R L; Simonova, M A; Samokhvalova, L V; Shoshina, N S; Kalinina, N A; Rubina, A Iu; Filippova, M A; Vertiev, Iu V; Grishin, E V

2009-01-01

369

Array biosensor for detection of toxins  

NASA Technical Reports Server (NTRS)

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).

Ligler, Frances S.; Taitt, Chris Rowe; Shriver-Lake, Lisa C.; Sapsford, Kim E.; Shubin, Yura; Golden, Joel P.

2003-01-01

370

[Botulinum toxin in focal hyperhidrosis. An update].  

PubMed

Eight years after its approval, intralesional injections of botulinum toxin type A have become established as an easily performed, highly effective and almost complication-free therapeutic option in primary axillary hyperhidrosis. Sweat production is decreased to about a sixth of previous amounts, and the effect persists for 7 months on average. Restoration of the often significantly impaired quality of life has been convincingly documented in large studies. The effect of botulinum toxin is based on the inhibition of the release of acetylcholine into the synaptic cleft. In addition to this approved use, botulinum toxin is also successfully employed in other forms of focal hyperhidrosis, particularly in gustatory sweating. However, its use in palmoplantar hyperhidrosis, the second most common form of primary hyperhidrosis, is limited because of the pain from numerous injections, need for increased doses of the expensive toxin and the relatively short effective period of about 4 months. Botulinum toxin type B appears to be comparably effective as type A products but is more often associated with systemic adverse events. PMID:22638981

Hosp, C; Naumann, M K; Hamm, H

2012-06-01

371

Cyanobacterial toxin degrading bacteria: who are they?  

PubMed

Cyanobacteria are ubiquitous in nature and are both beneficial and detrimental to humans. Benefits include being food supplements and producing bioactive compounds, like antimicrobial and anticancer substances, while their detrimental effects are evident by toxin production, causing major ecological problems at the ecosystem level. To date, there are several ways to degrade or transform these toxins by chemical methods, while the biodegradation of these compounds is understudied. In this paper, we present a meta-analysis of the currently available 16S rRNA and mlrA (microcystinase) genes diversity of isolates known to degrade cyanobacterial toxins. The available data revealed that these bacteria belong primarily to the Proteobacteria, with several strains from the sphingomonads, and one from each of the Methylobacillus and Paucibacter genera. Other strains belonged to the genera Arthrobacter, Bacillus, and Lactobacillus. By combining the ecological knowledge on the distribution, abundance, and ecophysiology of the bacteria that cooccur with toxic cyanobacterial blooms and newly developed molecular approaches, it is possible not only to discover more strains with cyanobacterial toxin degradation abilities, but also to reveal the genes associated with the degradation of these toxins. PMID:23841072

Kormas, Konstantinos Ar; Lymperopoulou, Despoina S

2013-01-01

372

Thermal degradation of paralytic shellfish poisoning toxins in scallop digestive glands  

Microsoft Academic Search

Digestive glands containing paralytic shellfish poisoning (PSP) toxins were isolated from toxic scallops. Citrate\\/phosphate buffers with the pH values ranging from 3 to 7 were added to achieve predetermined pH levels. The samples were heated at 90, 100, 110, 120 and 130°C using a computer controlled oil bath, and three tubes at each pH level were transferred into an ice

W. M Indrasena; T. A Gill

1999-01-01

373

Detoxication of a Purified and Concentrated Diphtheria Toxin by Formalin.  

National Technical Information Service (NTIS)

Results are presented from a study of the preparation of purified and concentrated diphtheria anatoxin by detoxication of purified toxin. Acid precipitation was used to purify the toxin. Loss of activity in the supernatant fluid and the precipitate did no...

L. V. Larionova N. N. Vasilev A. A. Vorobev N. A. Kalinskaya S. V. Chevotareva

1969-01-01

374

The Fixation of Tetanus Toxin by Synaptic Membranes.  

National Technical Information Service (NTIS)

The ability of subfractions of disrupted synaptosomes to bind tetanus toxin has been studied. Synaptic vesicles had little toxin-fixing capacity, but a fraction believed on morphological appearance and enzymic composition to be rich in external synaptosom...

J. Mellanby V. P. Whittaker

1968-01-01

375

[Action of some factors on P.R. toxin excretion].  

PubMed

Conditions of P.R. toxin production by 4 strains of Penicillium roqueforti are tested. This production occurs only in specific conditions of culture. Some strains do not produce P.R. toxin. PMID:613921

Guiraud, J; Piva, M T; Crouzet, J; Galzy, P

1977-01-01

376

Modulation of TRP Ion Channels by Venomous Toxins.  

PubMed

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. PMID:24961983

Siemens, Jan; Hanack, Christina

2014-01-01

377

In vitro metabolism of T-2 toxin in rats.  

PubMed Central

T-2 toxin was rapidly converted in the 9,000 X g supernatant fraction of rat liver homogenate into HT-2 toxin, T-2 tetraol, and two unknown metabolites designated as TMR-1 and TMR-2. TMR-1 was characterized as 4-deacetylneosolaniol (15-acetoxy-3 alpha, 4 beta, 8 alpha-trihydroxy-12,13-epoxytrichothec-9-ene) by spectroscopic analyses. Since the same metabolites were also obtained from HT-2 toxin used as substrate, it was concluded that T-2 toxin was hydrolyzed preferentially at the C-4 position to give HT-2 toxin, which was then metabolized to T-2 tetraol via 4-deacetylneosolaniol. In addition to HT-2 toxin, 4-deacetylneosolaniol and T-2 tetraol, a trace amount of neosolaniol was transformed from T-2 toxin by rat intestinal strips. In vitro metabolic pathways for T-2 toxin in rats are proposed.

Yoshizawa, T; Swanson, S P; Mirocha, C J

1980-01-01

378

[Treatment of lingual dystonia with botulinum toxin injections. First report].  

PubMed

This is the first report about successful botulinum toxin therapy of the intrinsic muscles of the tongue in two patient with lingual dystonias. In these patients botulinum toxin was injected direct into the tongue. PMID:19340405

Reichel, G; Stenner, A

2009-08-01

379

Domain Organization and Evolution of Multifunctional Autoprocessing Repeats-in-Toxin (MARTX) Toxin in Vibrio vulnificus? †  

PubMed Central

The objective of this study was to analyze multifunctional autoprocessing repeats-in-toxin (MARTX) toxin domain organization within the aquatic species Vibrio vulnificus as well as to study the evolution of the rtxA1 gene. The species is subdivided into three biotypes that differ in host range and geographical distribution. We have found three different types (I, II, and III) of V. vulnificus MARTX (MARTXVv) toxins with common domains (an autocatalytic cysteine protease domain [CPD], an ?/?-hydrolase domain, and a domain resembling that of the LifA protein of Escherichia coli O127:H6 E2348/69 [Efa/LifA]) and specific domains (a Rho-GTPase inactivation domain [RID], a domain of unknown function [DUF],a domain resembling that of the rtxA protein of Photorhabdus asymbiotica [rtxAPA], and an actin cross-linking domain [ACD]). Biotype 1 isolates harbor MARTXVv toxin types I and II, biotype 2 isolates carry MARTXVv toxin type III, and biotype 3 isolates have MARTXVv toxin type II. The analyzed biotype 2 isolates harbor two identical copies of rtxA1, one chromosomal and the other plasmidic. The evolutionary history of the gene demonstrates that MARTXVv toxins are mosaics, comprising pieces with different evolutionary histories, some of which have been acquired by intra- or interspecific horizontal gene transfer. Finally, we have found evidence that the evolutionary history of the rtxA1 gene for biotype 2 differs totally from the gene history of biotypes 1 and 3.

Roig, Francisco J.; Gonzalez-Candelas, Fernando; Amaro, Carmen

2011-01-01

380

Hemorrhagic toxins from rattlesnake (Crotalus atrox) venom. Pathogenesis of hemorrhage induced by three purified toxins.  

PubMed Central

The pathogenesis of hemorrhage induced by three purified components of rattlesnake (Crotalus atrox) venom was studied at the light and electron microscopic levels. Crude venom was fractionated by anion exchange and gel filtration in four steps. beta-Alanine acetate disk gel electrophoresis was used to demonstrate electrophoretic homogeneity. White mice were injected intramuscularly with 0.1 ml of a sublethal dose of hemorrhagic toxin. Gross examination revealed extensive hemorrhage 5 minutes after the injection of hemorrhagic toxins alpha and episilon; the same amount of hemorrhage was not present until 3 hours after the injection of hemorrhagic toxin beta. Light microscopic examination of muscel after injection of the toxins revealed areas of extensive hemorrhage in which very few intact capillaries could be found and also adjacent areas of slight hemorrhage in which capillaries were in various stages of degeneration. Necrosis of muscle cells was evident in tissue injected with hemorrhagic toxin beta. Electron microscopic examination showed that capillaries from toxin-injected muscle were in various stages of degeneration. Endothelial cells became very thin and broke down into vesicles prior to complete rupture. Gaps were formed within the cells while intercellular junctions remained intact. Plasma and erythrocytes leaked through these gaps and were observed in the endomysium. Many gaps were plugged with platelet aggregations. Collagen and the basal lamina associated with capillaries were usually disorganized or absent. The experimental injection of three purified hemorrhagic toxins induced hemorrhage by the same mechanism as does the crude venom, ie, per rhexis. In addition, one of the toxins, hemorrhagic toxin beta, causes myonecrosis. Images Figure 7 Figure 8 Figure 15 Figure 16 Figure 9 Figure 10 Figure 1 Figure 2 Figure 3 Figure 4 Figure 11 Figure 12 Figure 13 Figure 14 Figure 5 Figure 6

Ownby, C. L.; Bjarnason, J.; Tu, A. T.

1978-01-01

381

FURTHER STUDIES ON A LABILE IMMUNOGENIC PARTICULATE SUBSTANCE ISOLATED FROM MYCOBACTERIUM TUBERCULOSIS  

PubMed Central

Youmans, Anne S. (Northwestern University Medical School, Chicago, Ill.), and Guy P. Youmans. Further studies on a labile immunogenic particulate substance isolated from Mycobacterium tuberculosis. J. Bacteriol. 87:278–285. 1964.—A particulate fraction which was highly immunogenic for mice was collected by ultracentrifugation from mycobacteria disrupted in 0.25 m sucrose buffer. The active immunogenic material was present in the gelatinous pellet obtained after centrifugation at 40,000 rev/min (144,000 × g) for 3 hr. This active material could be prepared free from whole cells and cell walls. This was done either by several centrifugations at lower speeds, or by filtering the supernatant fluid from the 10,000 rev/min centrifugation through a Millipore filter (porosity 0.5 ?). No microorganisms were found on slides or in cultures made from these filtrates. The immunogenic moiety in the particulate fraction was found to be very labile. Temperatures higher than 0 to 4 C inactivated the immunogenic activity. There was an irreversible linear decrease in activity as the temperature increased. If fractions were frozen or lyophilized, the activity remained as high as the original material for 4 weeks, and then rapidly decreased. The immunogenic material also was very sensitive to the hydrogen-ion concentration; the optimal activity was found at pH 6.8 to 7.0. The activity decreased rapidly at more acid or alkaline pH values. Also, particulate fraction prepared in sucrose buffer at pH 7.3 and 7.6 was much less active than that prepared in sucrose buffer at pH 7.0. Immunogenic activity was decreased if the particulate fraction was dialyzed overnight against 0.01 m phosphate buffer or distilled water at 4 C. The detergent sodium lauryl sulfate inactivated immunogenic activity. Moreover, the use of a Waring Blendor to blend the ruptured cell mass before centrifugation decreased the activity. Finally, a markedly lower activity resulted if both the 20,000 and 40,000 rev/min centrifugations were done the day after the rupture of the cells. Some refinements in technique which are used now in the preparation of the particulate fraction are detailed.

Youmans, Anne S.; Youmans, Guy P.

1964-01-01

382

Preservation of labile organic matter in soils of drained thaw lakes in Northern Alaska  

NASA Astrophysics Data System (ADS)

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 clearly shown by increased amounts of aliphatic C in these small POM fractions. As revealed by 13C CPMAS NMR, with advancing soil age increasing aliphaticity was also detected in occluded small POM fractions. By 14C dating we could show the stabilization of younger more labile OM at greater depth in buried O horizons. Additionally the study of the microscale elemental distributions, using nano-scale secondary ion mass spectrometry (NanoSIMS) showed the initial formation of aggregates and organo-mineral interfaces in the studied permafrost soils.

Mueller, Carsten W.; Rethemeyer, Janet; Kao-Kniffin, Jenny; Löppmann, Sebastian; Hinkel, Kenneth; Bockheim, James

2014-05-01

383

Determination of labile inorganic and organic species of Al and Cu in river waters using the diffusive gradients in thin films technique.  

PubMed

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. PMID:21221548

Tonello, Paulo Sergio; Goveia, Danielle; Rosa, André Henrique; Fraceto, Leonardo Fernandes; Menegário, Amauri Antonio

2011-03-01

384

Bacterial Toxins and the Nervous System: Neurotoxins and Multipotential Toxins Interacting with Neuronal Cells  

PubMed Central

Toxins are potent molecules used by various bacteria to interact with a host organism. Some of them specifically act on neuronal cells (clostridial neurotoxins) leading to characteristics neurological affections. But many other toxins are multifunctional and recognize a wider range of cell types including neuronal cells. Various enterotoxins interact with the enteric nervous system, for example by stimulating afferent neurons or inducing neurotransmitter release from enterochromaffin cells which result either in vomiting, in amplification of the diarrhea, or in intestinal inflammation process. Other toxins can pass the blood brain barrier and directly act on specific neurons.

Popoff, Michel R.; Poulain, Bernard

2010-01-01

385

Applications of Botulinum toxin in urogynaecology.  

PubMed

Botulinum toxin (BTX) is a neurotoxin produced by bacterium clostridium. It is the most poisonous naturally occurring substance known to mankind. The neurotoxin binds to the peripheral cholinergic terminals and inhibits acetylcholine release at that junction leading to flaccid paralysis. This process appears to offer an attractive therapeutic option, filling the void between anticholinergics and surgery in cases of neurogenic and idiopathic detrusor overactivity, detrusor sphincter dyssynergia (DSD), interstitial cystitis and pelvic pain. This article reviews the application of Botulinum toxin A in these conditions. PMID:17275980

Sinha, D; Karri, K; Arunkalaivanan, A S

2007-07-01

386

Use of botulinum toxin in dentistry.  

PubMed

A growing number of dentists are providing botulinum toxin to patients. The research presented here outlines potential uses of Botox related to oral health and facial problems as compared to traditional treatment methods. The administration of Botox (historically done by dermatologists and neurologists) may fall under dentists' jurisdiction, as their training and knowledge encompasses the entire head and neck. A review is made of the literature, based on Ovid and PubMed searches, selecting articles describing the injection of botulinum toxin A in areas related to the oral cavity and the face, excluding cosmetic purposes. PMID:20069790

Hoque, Afreen; McAndrew, Maureen

2009-11-01

387

Shiga toxin-producing Escherichia coli (STEC).  

PubMed

Shiga toxin-producing Escherichia coli (STEC) are important enteric pathogens worldwide, causing diarrhea with or without blood visibly present and hemolytic uremic syndrome. STEC are unique among diarrheogenic E coli in producing Shiga toxin type 1 and type 2, the virulence factors responsible for bloody diarrhea and hemolytic uremic syndrome. Cattle and other ruminants are the natural reservoir of STEC as their normal intestinal flora. Humans become infected by consumption of foods contaminated with cattle feces. Early diagnosis of STEC infection is important because of the contraindication for treating STEC using antimicrobial agents, and the intense supportive care needed if renal failure occurs. PMID:20513540

Hunt, John M

2010-03-01

388

MICROBIOLOGY: Arresting Features of Bacterial Toxins  

NSDL National Science Digital Library

Access to the article is free, however registration and sign-in are required: Bacteria produce an arsenal of sophisticated toxins that disrupt the normal processes of the host cell, usually by modifying or inactivating host cell proteins. Now, as Coburn and Leong discuss in their Perspective, members of the cytolethal distending toxin (CDT) family have been identified as enzymes that attack DNA (and not protein) within the host cell (Lara-Tejero and Galán). By attacking DNA, perhaps during chromosomal replication, CDTs cause the host cell to halt in G2 phase of the cell cycle.

Jenifer Coburn (Tufts-New England Medical Center;Division of Rheumatology and Immunology); John M. Leong (University of Massachusetts Medical School;Department of Molecular Genetics and Microbiology)

2000-10-13

389

Anthrax toxin-induced rupture of artificial lipid bilayer membranes.  

PubMed

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. PMID:23947891

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

2013-08-14

390

Pichia acaciae killer system: genetic analysis of toxin immunity.  

PubMed

The gene responsible for self-protection in the Pichia acaciae killer plasmid system was identified by heterologous expression in Saccharomyces cerevisiae. Resistance profiling and conditional toxin/immunity coexpression analysis revealed dose-independent protection by pPac1-2 ORF4 and intracellular interference with toxin function, suggesting toxin reinternalization in immune killer cells. PMID:17483256

Paluszynski, John P; Klassen, Roland; Meinhardt, Friedhelm

2007-07-01

391

Serological study of yeast killer toxins by monoclonal antibodies  

Microsoft Academic Search

Yeast killer toxins coded by determined and undetermined killer plasmids or presumptive nuclear gene(s) in various genera (Saccharomyces, Kluyveromyces, Pichia and Candida) have been serologically investigated by a monoclonal antibody (KT4), produced against the yeast killer toxin of Pichia (Hansenula) anomala UCSC 25F. Double immunodiffusion with the killer toxins as antigens and indirect immunofluorescence on whole cells of the corresponding

Luciano Polonelli; Stefania Manzara; Stefania Conti; Giuseppe Dettori; Giulia Morace; Carlo Chezzi

1989-01-01

392

Shiga toxins and their mechanisms of cell entry  

Microsoft Academic Search

The Shiga toxins (Stxs) are related toxins secreted by Shigella dysenteriae, Escherichia coli in addition to other bacteria. They all act by entering cells and inhibiting protein synthesis enzymatically, thereby, killing the cells. Toxicity can also be mediated by induction of apoptosis. Furthermore, the Shiga toxins can in some cells induce secretion of a number of cytokines, some of which

Kirsten Sandvig; Sébastien Wälchli; Silje U. Lauvrak

393

Mutants of Pertussis Toxin Suitable for Vaccine Development  

Microsoft Academic Search

Immunization with chemically detoxified pertussis toxin can prevent severe whooping cough with an efficacy similar to that of the cellular pertussis vaccine, which normally gives unwanted side effects. To avoid the reversion to toxicity and the loss of immunogenicity that may follow chemical treatment of pertussis toxin, inactive toxins were constructed by genetic manipulation. A number of genetically engineered alleles

Mariagrazia Pizza; Antonio Covacci; Antonella Bartoloni; Maria Perugini; Luciano Nencioni; Maria Teresa de Magistris; Luigi Villa; Daniele Nucci; Roberto Manetti; Massimo Bugnoli; Franco Giovannoni; Roberto Olivieri; Joseph T. Barbieri; Hiroko Sato; Rino Rappuoli

1989-01-01

394

Helicobacter pylori VacA, a paradigm for toxin multifunctionality  

Microsoft Academic Search

Bacterial protein toxins alter eukaryotic cellular processes and enable bacteria to successfully colonize their hosts. In recent years, there has been increased recognition that many bacterial toxins are multifunctional proteins that can have pleiotropic effects on mammalian cells and tissues. In this review, we examine a multifunctional toxin (VacA) that is produced by the bacterium Helicobacter pylori. The actions of

Steven R. Blanke

2005-01-01

395

High-throughput production of two disulphide-bridge toxins.  

PubMed

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. PMID:24947561

Upert, Grégory; Mourier, Gilles; Pastor, Alexandra; Verdenaud, Marion; Alili, Doria; Servent, Denis; Gilles, Nicolas

2014-07-01

396

Vth Pan American Symposium on Animal, Plant and Microbial Toxins.  

National Technical Information Service (NTIS)

This report covers recent work in the areas of snake, plant, microbial and arthro- pod toxins. Presentations on snake toxins include work done on neurotoxins such as B-bungarotoxin and k-neurotoxins, phospholipase A2 myotoxins, anti-muscarinic toxins, met...

C. L. Ownby

1996-01-01

397

Effect of treatment with botulinum toxin on spasticity  

Microsoft Academic Search

Botulinum toxin, a product of Clostridium botulinum, produces presynaptic neuromuscular block by preventing release of acetylcholine from nerve endings. The toxin was injected directly into the skeletal muscles of six patients with severe spasticity due to stroke-related hemiplegia. It produced both subjective and objective improvement. The toxin injections were well tolerated and no significant side effect was reported.

T. K. Das; D. M. Park

1989-01-01

398

Mechanisms of Toxin Production of Food Bacteria (Clostridium botulinum).  

National Technical Information Service (NTIS)

Clostridium botulinum types C and D produced at least three toxins designated as C1, C2, and D. When different strains of types C and D were cured of their prophages, they ceased to produce C1 and D toxins, respectively. Toxin production depended upon the...

M. W. Eklund F. T. Poysky M. Strom L. Mseitif

1983-01-01

399

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...

400

Methyl methanesulfonate (MMS) produces heat-labile DNA damage but no detectable in vivo DNA double-strand breaks  

Microsoft Academic Search

Homologous recombination (HR) deficient cells are sensitive to methyl methanesulfonate (MMS). HR is usually involved in the repair of DNA double-strand breaks (DSBs) in Saccharomyces cerevisiae implying that MMS somehow induces DSBs in vivo. Indeed there is evidence, based on pulsed-field gel electro- phoresis (PFGE), that MMS causes DNA fragmenta- tion. However, the mechanism through which MMS induces DSBs has

Cecilia Lundin; Matthew North; Klaus Erixon; Kevin Walters; Dag Jenssen; Alastair S. H. Goldman; Thomas Helleday

2005-01-01

401

Clostridium difficile toxin B is more potent than toxin A in damaging human colonic epithelium in vitro.  

PubMed Central

Toxin A but not toxin B, appears to mediate intestinal damage in animal models of Clostridium difficile enteritis. The purpose of this study was to investigate the electrophysiologic and morphologic effects of purified C. difficile toxins A and B on human colonic mucosa in Ussing chambers. Luminal exposure of tissues to 16-65 nM of toxin A and 0.2-29 nM of toxin B for 5 h caused dose-dependent epithelial damage. Potential difference, short-circuit current and resistance decreased by 76, 58, and 46%, respectively, with 32 nM of toxin A and by 76, 55, and 47%, respectively, with 3 nM of toxin B, when compared with baseline (P < 0.05). 3 nM of toxin A did not cause electrophysiologic changes. Permeability to [3H]mannitol increased 16-fold after exposure to 32 nM of toxin A and to 3 nM of toxin B when compared with controls (P < 0.05). Light and scanning electron microscopy after exposure to either toxin revealed patchy damage and exfoliation of superficial epithelial cells, while crypt epithelium remained intact. Fluorescent microscopy of phalloidin-stained sections showed that both toxins caused disruption and condensation of cellular F-actin. Our results demonstrate that the human colon is approximately 10 times more sensitive to the damaging effects of toxin B than toxin A, suggesting that toxin B may be more important than toxin A in the pathogenesis of C. difficile colitis in man. Images

Riegler, M; Sedivy, R; Pothoulakis, C; Hamilton, G; Zacherl, J; Bischof, G; Cosentini, E; Feil, W; Schiessel, R; LaMont, J T

1995-01-01

402

Functional and Structural Insights of a Staphylococcus aureus Apoptotic-like Membrane Peptide from a Toxin-Antitoxin Module*  

PubMed Central

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.

Sayed, Nour; Nonin-Lecomte, Sylvie; Rety, Stephane; Felden, Brice

2012-01-01

403

Functional and structural insights of a Staphylococcus aureus apoptotic-like membrane peptide from a toxin-antitoxin module.  

PubMed

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 SprA1(AS) 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) SprA1(AS). 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 SprA1(AS) 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

Sayed, Nour; Nonin-Lecomte, Sylvie; Réty, Stéphane; Felden, Brice

2012-12-21

404

Energy evaluation of forest residues originated from Eucalyptus globulus Labill in Galicia.  

PubMed

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

Núñez-Regueira, L; Proupín-Castiñeiras, J; Rodríguez-Añón, J A

2002-03-01

405

PLGA microparticles with zero-order release of the labile anti-Parkinson drug apomorphine.  

PubMed

The treatment of patients suffering from advanced Parkinson's disease is highly challenging, because the efficacy of the "gold standard" levodopa declines with time. Co-administration of the dopamine receptor agonist apomorphine is beneficial, but difficult due to the poor oral bioavailability and short half-life of this drug. In order to overcome these restrictions, PLGA-based microparticles allowing for controlled parenteral delivery of this morphine derivative were prepared using (solid-in-)oil-in-water extraction/evaporation techniques. Particular attention was paid to minimize spontaneous oxidation of the labile drug and to optimize the key features of the microparticles, including encapsulation efficiency, initial burst release and particle size. Various formulation and processing parameters were adjusted in this respect. The systems were thoroughly characterized using SEM, EDX, DSC, laser diffraction, headspace-GC as well as in vitro drug release measurements in agitated flasks and flow-through cells. Importantly, apomorphine could effectively be protected against degradation during microparticle preparation and within the delivery systems upon exposure to phosphate buffer pH 7.4 (containing 0.2% ascorbic acid) at 37 °C: 90% intact drug was released at a constant rate during about 10d. PMID:23313920

Regnier-Delplace, C; Thillaye du Boullay, O; Siepmann, F; Martin-Vaca, B; Degrave, N; Demonchaux, P; Jentzer, O; Bourissou, D; Siepmann, J

2013-02-25

406

Facile synthesis of acid-labile polymers with pendent ortho esters.  

PubMed

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

Cheng, Jing; Ji, Ran; Gao, Shi-Juan; Du, Fu-Sheng; Li, Zi-Chen

2012-01-01

407

Uncaria tomentosa (Willd. ex. Roem. & Schult.) DC. and Eucalyptus globulus Labill. interactions when administered with diazepam.  

PubMed

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. PMID:21928376

Quílez, A M; Saenz, M T; García, M D

2012-03-01

408

Assessment of labile plasma iron in patients who undergo hematopoietic stem cell transplantation.  

PubMed

Body iron disorders have been reported after myeloablative conditioning in patients undergoing hematopoietic stem cell transplantation (HSCT). There is a concern that labile plasma iron (LPI), the redox-active form of iron, can be involved in the occurrence of toxicity and other complications commonly observed in the early post-HSCT period. In order to better understand the LPI kinetics and its determinants and implications, we undertook sequential LPI determinations before and after conditioning until engraftment in 25 auto-HSCT patients. Increased LPI was present in only 5 patients before starting conditioning. Shortly after conditioning, LPI levels were increased in 23 patients, with peak at day 0, returning to normal range upon engraftment in 21 patients. Overall, LPI levels correlated weakly with serum ferritin and more strongly with transferrin saturation; however, both parameters were apparently not applicable as surrogate markers for increased LPI. Although this was a small cohort, logistic regression suggested that baseline LPI levels could predict occurrence of grade III or IV toxicity. In conclusion, LPI kinetics is influenced by aplasia following conditioning and engraftment. Measuring LPI before starting conditioning can offer an opportunity to predict toxicity and, perhaps, the need for chelation therapy. © 2013 S. Karger AG, Basel. PMID:24335268

Naoum, Flávio Augusto; Espósito, Breno Pannia; Ruiz, Lílian Piron; Ruiz, Milton Artur; Tanaka, Paula Yurie; Sobreira, Juliana Tavora; Cançado, Rodolfo Delfini; de Barros, José Carlos

2014-01-01

409

Detergent-labile, supramolecular assemblies of KcsA: relative abundance and interactions involved.  

PubMed

In this work, we illustrate the ability of the prokaryotic potassium channel KcsA to assemble into a variety of supramolecular clusters of defined sizes containing the tetrameric KcsA as the repeating unit. Such clusters, particularly the larger ones, are markedly detergent-labile and thus, disassemble readily upon exposure to the detergents commonly used in protein purification or conventional electrophoresis analysis. This is a reversible process, as cluster re-assembly occurs upon detergent removal and without the need of added membrane lipids. Interestingly, the dimeric ensemble between two tetrameric KcsA molecules are quite resistant to detergent disassembly to individual KcsA tetramers and along with the latter, are likely the basic building blocks through which the larger clusters are organized. As to the proteins domains involved in clustering, we have observed disassembly of KcsA clusters by SDS-like alkyl sulfates. As these amphiphiles bind to inter-subunit, "non-annular" sites on the protein, these observations suggest that such sites also mediate channel-channel interactions leading to cluster assembly. PMID:23022492

Giudici, A Marcela; Molina, M Luisa; Ayala, José L; Montoya, Estefanía; Renart, M Lourdes; Fernández, Asia M; Encinar, José A; Ferrer-Montiel, Antonio V; Poveda, José A; González-Ros, José M

2013-02-01

410

Ancestral deceit and labile evolution of nectar production in the African orchid genus Disa.  

PubMed

An outstanding feature of the orchid family is that approximately 30-40% of the species have non-rewarding flowers and deploy various modes of deception to attract pollinators, whereas the remaining species engage in pollination mutualisms based on provision of floral rewards. Here, we explore the direction, frequency and reversibility of transitions between deceptive and rewarding pollination systems in the radiation of the large African genus Disa, and test whether these transitions had consequences for diversification. By optimizing nectar production data for 111 species on a well-resolved phylogeny, we confirmed that floral deception was the ancestral condition and that nectar production evolved at least nine times and was lost at least once. Transitions to nectar production first occurred ca 17 million years ago but did not significantly affect either speciation or extinction rates. Nectar evolved independently of a spur, which was lost and gained multiple times. These results show that nectar production can be a highly labile trait and highlight the need for further studies of the genetic architecture of nectar production and the selective factors underlying transitions between deception and mutualism. PMID:23904568

Johnson, Steven D; Hobbhahn, Nina; Bytebier, Benny

2013-10-23

411

Development and Bioorthogonal Activation of Palladium-Labile Prodrugs of Gemcitabine  

PubMed Central

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 Pd0-labile prodrugs to develop spatially targeted therapies. Herein, we report the generation of biologically inert precursors of cytotoxic gemcitabine by introducing Pd0-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.

2014-01-01

412

The Dual Filter Model: Labile Plant Inputs Form Stable Soil Organic Matter  

NASA Astrophysics Data System (ADS)

The decomposition of above and below-ground plant detritus (litter) is the main process by which soil organic matter (SOM) is formed. Yet, research on litter decay and SOM formation has been uncoupled, failing to provide an effective nexus between these two fundamental processes for carbon (C) and nitrogen (N) cycling and storage. However, a unified framework for integrating litter decomposition and SOM formation is emerging, whereby microbial resource use efficiency and allocation of C and N, in interaction with the soil matrix, controls the proportion of plant derived-C and -N that is retained in long-term SOM pools. We synthesize this emerging understanding and call it the Dual Filter Model, with the two filters being microbial resource use efficiency and soil matrix interactions. This model suggests that, since labile plant constituents are degraded more efficiently by microbes, they are the dominant source of microbial products, relative to input rates. Via promoting aggregation and through strong chemical bonding to clay particles, these microbial products of decomposition become the main precursors of stable SOM.

Cotrufo, M.; Wallenstein, M. D.; Boot, C. M.; Denef, K.; Paul, E.

2012-12-01