scholarly journals Role of Various Enterotoxins in Aeromonas hydrophila-Induced Gastroenteritis: Generation of Enterotoxin Gene-Deficient Mutants and Evaluation of Their Enterotoxic Activity

2002 ◽  
Vol 70 (4) ◽  
pp. 1924-1935 ◽  
Author(s):  
Jian Sha ◽  
E. V. Kozlova ◽  
A. K. Chopra
Keyword(s):  
Biological Activity ◽  
Mouse Model ◽  
Aeromonas Hydrophila ◽  
Fluid Secretion ◽  
The Other ◽  
Enterotoxin Gene ◽  
Knockout Mutant ◽  
Heat Stable ◽  
Isogenic Mutants

ABSTRACT Three enterotoxins from the Aeromonas hydrophila diarrheal isolate SSU have been molecularly characterized in our laboratory. One of these enterotoxins is cytotoxic in nature, whereas the other two are cytotonic enterotoxins, one of them heat labile and the other heat stable. Earlier, by developing an isogenic mutant, we demonstrated the role of a cytotoxic enterotoxin in causing systemic infection in mice. In the present study, we evaluated the role of these three enterotoxins in evoking diarrhea in a murine model by developing various combinations of enterotoxin gene-deficient mutants by marker-exchange mutagenesis. A total of six isogenic mutants were prepared in a cytotoxic enterotoxin gene (act)-positive or -negative background strain of A. hydrophila. We developed two single knockouts with truncation in either the heat-labile (alt) or the heat-stable (ast) cytotonic enterotoxin gene; three double knockouts with truncations of genes encoding (i) alt and ast, (ii) act and alt, and (iii) act and ast genes; and a triple-knockout mutant with truncation in all three genes, act, alt, and ast. The identity of these isogenic mutants developed by double-crossover homologous recombination was confirmed by Southern blot analysis. Northern and Western blot analyses revealed that the expression of different enterotoxin genes in the mutants was correspondingly abrogated. We tested the biological activity of these mutants in a diet-restricted and antibiotic-treated mouse model with a ligated ileal loop assay. Our data indicated that all of these mutants had significantly reduced capacity to evoke fluid secretion compared to that of wild-type A. hydrophila; the triple-knockout mutant failed to induce any detectable level of fluid secretion. The biological activity of selected A. hydrophila mutants was restored after complementation. Taken together, we have established a role for three enterotoxins in A. hydrophila-induced gastroenteritis in a mouse model with the greatest contribution from the cytotoxic enterotoxin Act, followed by the Alt and Ast cytotonic enterotoxins.

scholarly journals Effect of Farnesol on a Mouse Model of Systemic Candidiasis, Determined by Use of a DPP3 Knockout Mutant of Candida albicans

2007 ◽  
Vol 75 (4) ◽  
pp. 1609-1618 ◽  
Author(s):  
Dhammika H. M. L. P. Navarathna ◽  
Jacob M. Hornby ◽  
Navasona Krishnan ◽  
Anne Parkhurst ◽  
Gerald E. Duhamel ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Mouse Model ◽  
Tween 80 ◽  
Sublethal Dose ◽  
Systemic Candidiasis ◽  
Knockout Mutant ◽  
Gene Encoding

ABSTRACTThis work extends our previous observation that the fungusCandida albicanssecretes micromolar levels of farnesol and that accumulation of farnesol in vitro prevents the yeast-to-mycelium conversion in a quorum-sensing manner. What does farnesol do in vivo? The purpose of this study was to determine the role of farnesol during infection with a well-established mouse model of systemic candidiasis withC. albicansA72 administered by tail vein injection. This question was addressed by altering both endogenous and exogenous farnesol. For endogenous farnesol, we created a knockout mutation inDPP3, the gene encoding a phosphatase which converts farnesyl pyrophosphate to farnesol. This mutant (KWN2) produced six times less farnesol and was ca. 4.2 times less pathogenic than its SN152 parent. The strain withDPP3reconstituted (KWN4) regained both its farnesol production levels and pathogenicity. These mutants (KWN1 to KWN4) retained their full dimorphic capability. With regard to exogenous farnesol, farnesol was administered either intraperitoneally (i.p.) or orally in the drinking water. Mice receivingC. albicansintravenously and farnesol (20 mM) orally had enhanced mortality (P< 0.03). Similarly, mice (n= 40) injected with 1.0 ml of 20 mM farnesol i.p. had enhanced mortality (P< 0.03), and the onset of mortality was 30 h sooner than for mice which received a control injection without farnesol. The effect of i.p. farnesol was more pronounced (P< 0.04) when mice were inoculated with a sublethal dose ofC. albicans. These mice started to die 4 days earlier, and the percent survival on day 6 postinoculation (p.i.) was five times lower than for mice receivingC. albicanswith control i.p. injections. In all experiments, mice administered farnesol alone or Tween 80 alone remained normal throughout a 14-day observation period. Finally, beginning at 12 h p.i., higher numbers ofC. albicanscells were detected in kidneys from mice receiving i.p. farnesol than in those from mice receiving control i.p. injections. Thus, reduced endogenous farnesol decreased virulence, while providing exogenous farnesol increased virulence. Taken together, these data suggest that farnesol may play a role in disease pathogenesis, either directly or indirectly, and thus may represent a newly identified virulence factor.

scholarly journals Role of Hcp, a type 6 secretion system effector, of Aeromonas hydrophila in modulating activation of host immune cells

Microbiology ◽  
2010 ◽  
Vol 156 (12) ◽  
pp. 3678-3688 ◽  
Author(s):  
Giovanni Suarez ◽  
Johanna C. Sierra ◽  
Michelle L. Kirtley ◽  
Ashok K. Chopra
Keyword(s):  
Mouse Model ◽  
Aeromonas Hydrophila ◽  
Transforming Growth Factor ◽  
Interleukin 10 ◽  
Secretion System ◽  
Bacterial Virulence ◽  
Host Cells ◽  
Extracellular Milieu

Recently, we reported that the type 6 secretion system (T6SS) of Aeromonas hydrophila SSU plays an important role in bacterial virulence in a mouse model, and immunization of animals with the T6SS effector haemolysin co-regulated protein (Hcp) protected them against lethal infections with wild-type bacteria. Additionally, we showed that the mutant bacteria deleted for the vasH gene within the T6SS gene cluster did not express the hcp gene, while the vasK mutant could express and translocate Hcp, but was unable to secrete it into the extracellular milieu. Both of these A. hydrophila SSU mutants were readily phagocytosed by murine macrophages, pointing to the possible role of the secreted form of Hcp in the evasion of the host innate immunity. By using the ΔvasH mutant of A. hydrophila, our in vitro data showed that the addition of exogenous recombinant Hcp (rHcp) reduced bacterial uptake by macrophages. These results were substantiated by increased bacterial virulence when rHcp was added along with the ΔvasH mutant in a septicaemic mouse model of infection. Analysis of the cytokine profiling in the intraperitoneal lavage as well as activation of host cells after 4 h of infection with the ΔvasH mutant supplemented with rHcp indicated that this T6SS effector inhibited production of pro-inflammatory cytokines and induced immunosuppressive cytokines, such as interleukin-10 and transforming growth factor-β, which could circumvent macrophage activation and maturation. This mechanism of innate immune evasion by Hcp possibly inhibited the recruitment of cellular immune components, which allowed bacterial multiplication and dissemination in animals, thereby leading to their mortality.

scholarly journals Inhibition of the Ventral Hippocampus Increases Alcohol Drinking

2019 ◽  
Author(s):  
William C. Griffin ◽  
Jennifer A. Rinker ◽  
John J. Woodward ◽  
Patrick J. Mulholland ◽  
Howard C. Becker
Keyword(s):  
Mouse Model ◽  
Ventral Hippocampus ◽  
The Other ◽  
Calcium Dependent ◽  
Ethanol Drinking ◽  
Reward Seeking ◽  
Ethanol Dependence ◽  
Dependent Activity ◽  
Drinking Ethanol

AbstractThe function of the ventral hippocampus (vHC) supports many behaviors, including those related to reward seeking behaviors and drug addiction. We used a mouse model of alcohol dependence and relapse to investigate the role of the vHC in alcohol (ethanol) drinking. One experiment used a chemogenetic approach to inhibit vHC function while ethanol dependent and non-dependent mice had access to ethanol. Interestingly, the non-dependent mice expressing an inhibitory DREADD in the VHC showed a significant increase in ethanol drinking (∼30%) after hM4Di DREADD activation with clozapine-n-oxide (CNO; 3 mg/kg, ip.) compared to vehicle. On the other hand, ethanol dependent mice, which were already drinking significantly more ethanol than non-dependent mice, only had a slight, non-significant increase in drinking after CNO challenge. In a separate group of dependent and non-dependent mice, GCaMP6f calcium-dependent activity was recorded in the vHC while mice were actively drinking ethanol. These data showed that once mice were rendered ethanol dependent and were drinking more ethanol than the non-dependent mice, calcium signaling in the ventral hippocampus decreased (∼45%) in the ethanol dependent mice compared to the non-dependent mice. Together, these findings suggest that ethanol dependence reduces activity of the ventral hippocampus and that reduced function of this brain region contributes to increased ethanol drinking.

scholarly journals Gut-associated cGMP mediates colitis and dysbiosis in a mouse model of an activating mutation in GUCY2C

2021 ◽  
Vol 218 (11) ◽  
Author(s):  
Vishwas Mishra ◽  
Avipsa Bose ◽  
Shashi Kiran ◽  
Sanghita Banerjee ◽  
Idrees A. Shah ◽  
...  
Keyword(s):  
Mouse Model ◽  
Fluid Secretion ◽  
Sodium Content ◽  
Mutant Mice ◽  
Chronic Inflammatory Bowel Disease ◽  
Small Intestinal Transit ◽  
Fecal Microbiome ◽  
Activating Mutations ◽  
Heat Stable ◽  
Activating Mutation

Activating mutations in receptor guanylyl cyclase C (GC-C), the target of gastrointestinal peptide hormones guanylin and uroguanylin, and bacterial heat-stable enterotoxins cause early-onset diarrhea and chronic inflammatory bowel disease (IBD). GC-C regulates ion and fluid secretion in the gut via cGMP production and activation of cGMP-dependent protein kinase II. We characterize a novel mouse model harboring an activating mutation in Gucy2c equivalent to that seen in an affected Norwegian family. Mutant mice demonstrated elevated intestinal cGMP levels and enhanced fecal water and sodium content. Basal and linaclotide-mediated small intestinal transit was higher in mutant mice, and they were more susceptible to DSS-induced colitis. Fecal microbiome and gene expression analyses of colonic tissue revealed dysbiosis, up-regulation of IFN-stimulated genes, and misregulation of genes associated with human IBD and animal models of colitis. This novel mouse model thus provides molecular insights into the multiple roles of intestinal epithelial cell cGMP, which culminate in dysbiosis and the induction of inflammation in the gut.

scholarly journals Expression of Heat-Stable Enterotoxin STb by Adherent Escherichia coli Is Not Sufficient To Cause Severe Diarrhea in Neonatal Pigs

1998 ◽  
Vol 66 (3) ◽  
pp. 1270-1272 ◽  
Author(s):  
Thomas A. Casey ◽  
Cheryl J. Herring ◽  
Robert A. Schneider ◽  
Brad T. Bosworth ◽  
Shannon C. Whipp
Keyword(s):  
Escherichia Coli ◽  
Fluid Secretion ◽  
E Coli ◽  
Severe Diarrhea ◽  
Neonatal Pigs ◽  
Heat Stable ◽  
Isogenic Strains ◽  
Mild Diarrhea

ABSTRACT The role of Escherichia coli heat-stable enterotoxin B (STb) in neonatal porcine diarrhea caused by enterotoxigenic E. coli was examined by comparing adherent isogenic strains with or without STb. The cloned STb gene (in the plasmid pRAS1) was electroporated into a nonenterotoxigenic strain (226M) which expresses the F41 adhesin. Strain 226M pRAS1 adhered and expressed STb in vivo, causing fluid secretion in ligated ileal loops in neonatal pigs. Although strain 226M pRAS1 caused very mild diarrhea in some orally inoculated neonatal pigs, the weight loss in these pigs was similar to that caused by the parental strain without STb. We conclude that STb does not significantly contribute to diarrhea caused by enterotoxigenic E. coli in neonatal pigs.

scholarly journals Ammonia plus another factor are necessary for differentiation in submerged clumps of Dictyostelium

1979 ◽  
Vol 38 (1) ◽  
pp. 181-191
Author(s):  
J. Sternfeld ◽  
C.N. David
Keyword(s):  
Biological Activity ◽  
Conditioned Medium ◽  
Oxygen Atmosphere ◽  
The Other ◽  
Free Medium ◽  
Heat Stable

Differentiation of Dictyostelium amoebae can occur in submerged clumps of cells; under an oxygen atmosphere mature stalk cells and spores form, as has been shown in previous work. This report shows that at least 2 factors are released by the cells under these conditions, and that both, together, are required for differentiation of stalk cells and spores. One of the factors is ammonia (NH3 + NH4+). The other factor(s) is heat stable and dialysable but has not yet been further characterized. The factors can be collected in conditioned medium and, when added to cells, stimulate differentiation. Conditioned medium loses its biological activity upon the removal of the NH3 + NH4+. When NH3 + NH4+ is added back, activity is restored. Because NH3 + NH4+, alone, has no activity, a second factor(s) in the conditioned medium must be required for differentiation. It is also shown that calcium inhibits differentiation in submerged clumps and that in calcium-free medium the timing of differentiation is essentially the same as under aerial conditions.

Plasma Levels of Protein S, Protein C, and Factor X: Effects of Sex, Hormonal State and Age

1995 ◽  
Vol 74 (05) ◽  
pp. 1271-1275 ◽  
Author(s):  
C M A Henkens ◽  
V J J Bom ◽  
W van der Schaaf ◽  
P M Pelsma ◽  
C Th Smit Sibinga ◽  
...  
Keyword(s):  
Regression Analysis ◽  
Postmenopausal Women ◽  
Protein C ◽  
Blood Donors ◽  
Premenopausal Women ◽  
Protein S ◽  
The Other ◽  
Factor X ◽  
Normal Ranges

SummaryWe measured total and free protein S (PS), protein C (PC) and factor X (FX) in 393 healthy blood donors to assess differences in relation to sex, hormonal state and age. All measured proteins were lower in women as compared to men, as were levels in premenopausal women as compared to postmenopausal women. Multiple regression analysis showed that both age and subgroup (men, pre- and postmenopausal women) were of significance for the levels of total and free PS and PC, the subgroup effect being caused by the differences between the premenopausal women and the other groups. This indicates a role of sex-hormones, most likely estrogens, in the regulation of levels of pro- and anticoagulant factors under physiologic conditions. These differences should be taken into account in daily clinical practice and may necessitate different normal ranges for men, pre- and postmenopausal women.

The role of tachykinin 1 in a mouse model of trait anxiety

2007 ◽  
Vol 40 (05) ◽  
Author(s):  
L Czibere ◽  
LA Baur-Jaronowski ◽  
P Weber ◽  
B Pütz ◽  
M Panhuysen ◽  
...  
Keyword(s):  
Mouse Model ◽  
Trait Anxiety

On the role of the dispute between "non-possessors" and "Josephites" in the culture of Moscow's prediction

1998 ◽  
pp. 61-62
Author(s):  
N. S. Jurtueva
Keyword(s):  
The Other ◽  
Moral Transformation ◽  
15Th Century ◽  
The Future ◽  
Secular Power

In the XIV century. centripetal tendencies began to appear in the Moscow principality. Inside the Russian church, several areas were distinguished. Part of the clergy supported the specificobar form. The other understood the need for transformations in society. As a result, this led to a split in the Russian church in the 15th century for "non-possessors" and "Josephites". The former linked the fate of the future with the ideology of hesychasm and its moral transformation, while the latter sought support in alliance with a strong secular power.

From Container to Claustrum: Projective Identification in Couples

2014 ◽  
Vol 4 (2) ◽  
Author(s):  
Tamara Feldman
Keyword(s):  
Psychological Health ◽  
Projective Identification ◽  
The Self ◽  
The Other ◽  
Intimate Partners ◽  
And Control ◽  
The Relationship ◽  
As If

This paper is a contribution to the growing literature on the role of projective identification in understanding couples' dynamics. Projective identification as a defence is well suited to couples, as intimate partners provide an ideal location to deposit unwanted parts of the self. This paper illustrates how projective identification functions differently depending on the psychological health of the couple. It elucidates how healthier couples use projective identification more as a form of communication, whereas disturbed couples are inclined to employ it to invade and control the other, as captured by Meltzer's concept of "intrusive identification". These different uses of projective identification affect couples' capacities to provide what Bion called "containment". In disturbed couples, partners serve as what Meltzer termed "claustrums" whereby projections are not contained, but imprisoned or entombed in the other. Applying the concept of claustrum helps illuminate common feelings these couples express, such as feeling suffocated, stifled, trapped, held hostage, or feeling as if the relationship is killing them. Finally, this paper presents treatment challenges in working with more disturbed couples.

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