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Hemolytic Activity (hemolytic + activity)

Distribution by Scientific Domains

Medical Sciences	41%
Chemistry	29%
Life Sciences	20%

Selected Abstracts

SIDEROPHORE PRODUCTION, SERUM RESISTANCE, HEMOLYTIC ACTIVITY AND EXTENDED-SPECTRUM ,-LACTAMASE-PRODUCING KLEBSIELLA SPECIES ISOLATED FROM MILK AND MILK PRODUCTS

JOURNAL OF FOOD SAFETY, Issue 3 2007
HAN GUNDOGAN
ABSTRACT This study aimed at the isolation and identification of Klebsiella spp. from dairy product to establish their public health significance by determining their virulence factors, antibiotic resistance and extended-spectrum ,-lactamase (ESBL). Klebsiella pneumoniae, Klebsiella oxytoca and Klebsiella rhinoscleromatis were identified in 25 (58%), 11 (26%) and 7 (16%) isolates, respectively. A high prevalence of Klebsiella isolates had virulence factors such as siderophore production (63%), serum resistance (32.5%) and hemolytic activity (58%). ESBL - producing Klebsiella spp. was detected in 35% of the isolates. Resistance to the antimicrobial agents tested was found to be much higher in the ESBL-producing Klebsiella spp. than in non-ESBL-producing isolates. All ESBL-producing Klebsiella spp. showed high-level resistance to cephalosporins and monobactams. The majority of the serum resistant, siderophore, hemolysin and ESBL producers were K. pneumoniae. [source]

HEMOLYTIC ACTIVITY OF HETEROCAPSA CIRCULARISQUAMA (DINOPHYCEAE) AND ITS POSSIBLE INVOLVEMENT IN SHELLFISH TOXICITY

JOURNAL OF PHYCOLOGY, Issue 4 2001
Tatsuya Oda
Heterocapsa circularisquama Horiguchi is lethal to shellfish, particularly bivalves such as pearl oysters (Pinctada fucata Gould). No detrimental effects of this flagellate on fish have been observed thus far. In this study, we found that H. circularisquama causes mammalian erythrocytes to lyse. Among the erythrocytes tested, rabbit erythrocytes showed the highest susceptibility, whereas erythrocytes from cattle, sheep, and human were relatively insensitive. Heterocapsa triquetra Stein, which is morphologically similar to H. circularisquama but not toxic to bivalves, showed no hemolytic activity toward rabbit erythrocytes. Culture supernatant or ultrasonic-ruptured cells of H. circularisquama showed only weak hemolytic activity. Hemolytic activity was found in the ethanol extract of H. circularisquama cells, suggesting that the hemolytic agents may be more stable in ethanol than in aqueous solution. Both an intact flagellate cell suspension and the ethanol extract caused morphological changes and eventual collapse of unfertilized eggs of Pacific oyster. Furthermore, the ethanol extract was lethal to the microzooplankton rotifer Brachionus plicatilis Müller, which is highly sensitive to H. circularisquama. Our results suggest that a hemolytic toxin produced by H. circularisquama may be one of the causative agents responsible for the shellfish toxicity. [source]

Antibacterial and Hemolytic Activities of Quaternary Pyridinium Functionalized Polynorbornenes

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 5 2008
Tarik Eren
Abstract In this study, amphiphilic polyoxanorbornene with different quaternary alkyl pyridinium side chains were synthesized. The biological efficiencies of these polymers, with various alkyl substituents, were determined by bacterial growth inhibition assays and hemolytic activity (HC50) against human red blood cells (RBCs) to provide selectivity of these polymers for bacterial over mammalian cells. A series of polymers with different alkyl substituents (ethyl, butyl, hexyl, octyl, decyl and phenylethyl) and two different molecular weights (3 and 10 kDa) were prepared. The impact of alkyl chain length divided the biological activity into two different cases: those with an alkyl substituent containing four or fewer carbons had a minimum inhibitory concentration (MIC) of 200 µg,·,mL,1 and a HC50 greater than 1,650 µg,·,mL,1, while those with six or more carbons had lower MICs,,,12.5 µg,·,mL,1 and HC50,,,250 µg,·,mL,1. Using MSI-78, the potent Magainin derivative which has an MIC,=,12.0 µg,·,mL,1 and HC50,=,120 µg,·,mL,1, as a comparison, the polymers with alkyl substituents ,C4 (four carbons) were not very potent, but did show selectivity values greater than or equal to MSI-78. In contrast, those with alkyl substituents ,C6 were as potent, or more potent, than MSI-78 and in three specific cases demonstrated selectivity values similar to, or better than, MSI-78. To understand if these polymers were membrane active, polymer induced lipid membrane disruption activities were evaluated by dye leakage experiments. Lipid composition and polymer hydrophobicity were found to be important factors for dye release. [source]

HEMOLYTIC ACTIVITY OF HETEROCAPSA CIRCULARISQUAMA (DINOPHYCEAE) AND ITS POSSIBLE INVOLVEMENT IN SHELLFISH TOXICITY

Structure,activity relationship of an antibacterial peptide, maculatin 1.1, from the skin glands of the tree frog, Litoria genimaculata

JOURNAL OF PEPTIDE SCIENCE, Issue 7 2004
Takuro Niidome
Abstract Maculatin 1.1 (Mac) is a cationic antibacterial peptide isolated from the dorsal glands of the tree frog, Litoria genimaculata, and has a sequence of GLFGVLAKVAAHVVPAIAEHF-NH2. A short peptide lacking the N -terminal two residues of Mac was reported to have no activity. To investigate the structure,activity relationship in detail, several analogs and related short peptides of Mac were synthesized. CD measurement showed that all the peptides took more or less an ,-helical structure in the presence of anionic lipid vesicles. Analogs which are more basic than Mac had strong antibacterial and hemolytic activities, while short peptides lacking one or two terminal residues exhibited weak or no activity. Outer and inner membrane permeabilization activities of the peptides were also reduced with shortening of the peptide chain. These results indicate that the entire chain length of Mac is necessary for full activity, and the basicity of the peptides greatly affects the activity. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd. [source]

Two distinct hemolysins in Trichomonas tenax ATCC 30207

MOLECULAR ORAL MICROBIOLOGY, Issue 6 2000
E. Nagao
An oral protist Trichomonas tenax ATCC 30207 was investigated for the ability to lyse erythrocytes of sheep, rabbits, horses and humans. Five fractions, including intact cells, culture supernatant, culture filtrate, cell debris and lipid-enriched fractions, were prepared from the protozoan cells, and their hemolytic activities were assayed under various conditions. All the samples except culture supernatant had hemolytic activities, which were due to two different kinds of hemolysins. One hemolysin was protein-like and mainly found in cell-free fractions: culture supernatant and culture filtrate. It was heat-labile and inhibited by various cysteine-proteinase inhibitors. The other hemolysin was lipid-like and found in cell-associated fractions: intact cells, cell-debris and lipid-enriched fractions. It was heat-stable, organic solvent,tolerant and unaffected by various proteinase inhibitors and stimulators. These results suggested that T. tenax ATCC 30207 possessed two distinct hemolysins, protein and lipid. [source]

Role of the complement-lectin pathway in anaphylactoid reaction induced with lipopolysaccharide in mice

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 10 2003
wierzko
Abstract We show that Proteus vulgaris,O25 (PO25) lipopolysaccharide (LPS) induced an anaphylactoid reaction not only in wild-type and in lipid,A non-responding mice but also in recombinase-activating gene-2-deficient (RAG-2,/,) and in mast cell-deficient (W/Wv) animals. Western blot analysis indicated that PO25 LPS bound to Ra-reactive factor (RaRF), the complex of mannan-binding lectins (MBL) and MBL-associated serine proteases. Binding of RaRF to PO25 LPS led to the activation of C4 component without participation of either C1 or Ig, via the lectin pathway. Relative concentration of RaRF and hemolytic activity in mouse serum decreased rapidly during the process of anaphylactoid reaction. A significant drop of MBL-A, but not MBL-C level was observed. Administrationwith antiserum to RaRF prevented animals from death as a consequence of the inhibition of interaction of RaRF with the carbohydrate target and complement activation. These results indicate that complement-lectin pathway activation is responsible for the anaphylactoid reaction induced with LPS in muramyldipeptide-primed mice. RaRF also activated fibrinogen in vitro suggesting the involvement of the coagulation system in the process investigated. [source]

Identification of residues critical for toxicity in Clostridium perfringens phospholipase C, the key toxin in gas gangrene

FEBS JOURNAL, Issue 16 2000
Alberto Alape-Girón
Clostridium perfringens phospholipase C (PLC), also called ,-toxin, is the major virulence factor in the pathogenesis of gas gangrene. The toxic activities of genetically engineered ,-toxin variants harboring single amino-acid substitutions in three loops of its C-terminal domain were studied. The substitutions were made in aspartic acid residues which bind calcium, and tyrosine residues of the putative membrane-interacting region. The variants D269N and D336N had less than 20% of the hemolytic activity and displayed a cytotoxic potency 103 -fold lower than that of the wild-type toxin. The variants in which Tyr275, Tyr307, and Tyr331 were substituted by Asn, Phe, or Leu had 11,73% of the hemolytic activity and exhibited a cytotoxic potency 102 - to 105 -fold lower than that of the wild-type toxin. The results demonstrated that the sphingomyelinase activity and the C-terminal domain are required for myotoxicity in vivo and that the variants D269N, D336N, Y275N, Y307F, and Y331L had less than 12% of the myotoxic activity displayed by the wild-type toxin. This work therefore identifies residues critical for the toxic activities of C. perfringens PLC and provides new insights toward understanding the mechanism of action of this toxin at a molecular level. [source]

High relative content of lysophospholipids of Helicobacter pylori mediates increased risk for ulcer disease

FEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 1 2005
Tone Tannaes
Abstract Helicobacter pylori phospholipase A (OMPLA) degrades bacterial membrane phospholipids to lysophospholipids. High levels of lysophospholipids are associated with higher hemolytic activity, increased release of urease and vacA and better adherence to epithelial cells in vitro. The phospholipase A gene (pldA) displays phase variation due to a slippage in a homopolymeric tract. The aim of this study was to determine if the relative amount of lysophospholipids in the cell wall is associated with ulcer disease, and to further investigate the significance of pldA phase variation. H. pylori isolates of 40 patients were examined. The relative lysophospholipid content of each isolate was determined and the pldA gene was sequenced. The study indicated that H. pylori can regulate its OMPLA activity by phase variation in the pldA gene or by protein level regulation among phase variants in the pldA,ON' status. We found a significant difference between the relative amount of lysophospholipids of the ulcer group and the non-ulcer group (p= 0.022). When the lysophospholipid/phospholipid ratios were compared with outcome, the OR for ulcer disease was 9.0 (95% CI 1.6,49.4; p= 0.014). Isolates with a high OMPLA activity are significantly associated with patients with ulcer disease. [source]

Secretion of the Escherichia coli K-12 SheA hemolysin is independent of its cytolytic activity

FEMS MICROBIOLOGY LETTERS, Issue 2 2001
Francisco J del Castillo
Abstract The Escherichia coli K-12 sheA gene encodes a pore-forming hemolysin that is secreted to the medium by a hitherto unidentified mechanism. To study SheA secretion, we constructed fusions between SheA and the mature form of the periplasmic enzyme ,-lactamase, and performed site-directed mutagenesis on these constructs. The SheA-Bla and Bla-SheA hybrid proteins displayed hemolytic activity and were efficiently exported to the extracellular medium. Our results with mutant hybrid proteins show that secretion of SheA is independent of its cytolytic activity, that secretion is paralleled by a transient leakage of periplasmic contents to the extracellular medium, and that deletion of the 11 C-terminal residues of SheA has no effect on its secretion and cytolytic activity. [source]

SIDEROPHORE PRODUCTION, SERUM RESISTANCE, HEMOLYTIC ACTIVITY AND EXTENDED-SPECTRUM ,-LACTAMASE-PRODUCING KLEBSIELLA SPECIES ISOLATED FROM MILK AND MILK PRODUCTS

Structural studies and model membrane interactions of two peptides derived from bovine lactoferricin

JOURNAL OF PEPTIDE SCIENCE, Issue 7 2005
Leonard T. Nguyen
Abstract The powerful antimicrobial properties of bovine lactoferricin (LfcinB) make it attractive for the development of new antimicrobial agents. An 11-residue linear peptide portion of LfcinB has been reported to have similar antimicrobial activity to lactoferricin itself, but with lower hemolytic activity. The membrane-binding and membrane-perturbing properties of this peptide were studied together with an amidated synthetic version with an added disulfide bond, which was designed to confer increased stability and possibly activity. The antimicrobial and cytotoxic properties of the peptides were measured against Staphylococcus aureus and Escherichia coli and by hemolysis assays. The peptides were also tested in an anti-cancer assay against neuroblastoma cell lines. Vesicle disruption caused by these LfcinB derivatives was studied using the fluorescent reporter molecule calcein. The extent of burial of the two Trp residues in membrane mimetic environments were quantitated by fluorescence. Finally, the solution NMR structures of the peptides bound to SDS micelles were determined to provide insight into their membrane bound state. The cyclic peptide was found to have greater antimicrobial potency than its linear counterpart. Consistent with this property, the two Trp residues of the modified peptide were suggested to be embedded deeper into the membrane. Although both peptides adopt an amphipathic structure without any regular ,-helical or ß-sheet conformation, the 3D-structures revealed a clearer partitioning of the cationic and hydrophobic faces for the cyclic peptide. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd. [source]

HEMOLYTIC ACTIVITY OF HETEROCAPSA CIRCULARISQUAMA (DINOPHYCEAE) AND ITS POSSIBLE INVOLVEMENT IN SHELLFISH TOXICITY

Antibacterial and Hemolytic Activities of Quaternary Pyridinium Functionalized Polynorbornenes

LuxS and expression of virulence factors in Streptococcus intermedius

MOLECULAR ORAL MICROBIOLOGY, Issue 1 2008
D. Pecharki
Background/aims:, Autoinducer-2 (AI-2) is used by several bacteria in quorum-sensing signaling and is a product of LuxS. The aim was to investigate the effect of LuxS mutation on expression of Streptococcus intermedius virulence factors. Methods:,S. intermedius mutants were constructed by insertion inactivation or gene deletion. Real time RT-PCR was used to assess transcription of pas, ily and hyl. Hyaluronidase and intermedilysin activities were measured biochemically. Results:, The results indicated that disruption of luxS in S. intermedius may affect hyaluronidase and intermedilysin gene expressions. No difference in antigen I/II expression was observed. Biochemical methods showed a five-fold decrease in hemolytic activity of the luxS mutant; however, secreted hyaluronidase activity was unaffected. The AI-2 precursor 4,5-dihydroxy-2,3-pentanedione complemented lack of AI-2 production by the mutant thus restoring hemolytic activity. Conclusions:, We suggest that AI-2 communication is involved in intermedilysin expression. [source]

Distribution and characterization of hemolytic activity by an oral anaerobe from the Streptococcus milleri group

MOLECULAR ORAL MICROBIOLOGY, Issue 2 2004
T. Yamaguchi
Some oral anaerobes from the Streptococcus milleri strain group were found to secrete human specific hemolytic toxin, which was detected when bacteria were cultured in Todd-Hewitt broth and Brain Heart Infusion broth. The toxin elicited by the Streptococcus intermedius strain was partially fractionated by ammonium sulfate precipitation. Preincubation with glutathione or cysteine showed significant inhibiting effects; however, no effects were seen with dithiothreitol or ,-mercaptoethanol, and cholesterol was a weak inhibitor. Five kinds of protease inhibitor had no effect on the hemolytic activity, and rabbit preimmune and immune sera against the bacterial cells showed weak inhibition at a similar level. Digestion with trypsin, chymotrypsin, proteinase-K, subtilisin and pronase-P brought about a rise in activity, followed by a decrease during long-term incubation. Other enzymes tested showed no effects. Further, the presence of the intermedilysin gene in the portion with hemolytic activity was not identified by polymerase chain reaction. [source]

Novel complement inhibitor limits severity of experimentally myasthenia gravis,

ANNALS OF NEUROLOGY, Issue 1 2009
Jindrich Soltys DVM
Objective Complement mediated injury of the neuromuscular junction is considered a primary disease mechanism in human myasthenia gravis and animal models of experimentally acquired myasthenia gravis (EAMG). We utilized active and passive models of EAMG to investigate the efficacy of a novel C5 complement inhibitor rEV576, recombinantly produced protein derived from tick saliva, in moderating disease severity. Methods Standardized disease severity assessment, serum complement hemolytic activity, serum cytotoxicity, acetylcholine receptor (AChR) antibody concentration, IgG subclassification, and C9 deposition at the neuromuscular junction were used to assess the effect of complement inhibition on EAMG induced by administration of AChR antibody or immunization with purified AChR. Results Administration of rEV576 in passive transfer EAMG limited disease severity as evidenced by 100% survival rate and a low disease severity score. In active EAMG, rats with severe and mild EAMG were protected from worsening of disease and had limited weight loss. Serum complement activity (CH50) in severe and mild EAMG was reduced to undetectable levels during treatment, and C9 deposition at the neuromuscular junction was reduced. Treatment with rEV576 resulted in reduction of toxicity of serum from severe and mild EAMG rats. Levels of total AChR IgG, and IgG2a antibodies were similar, but unexpectedly, the concentration of complement fixing IgG1 antibodies was lower in a group of rEV576-treated animals, suggesting an effect of rEV576 on cellular immunity. Interpretation Inhibition of complement significantly reduced weakness in two models of EAMG. C5 inhibition could prove to be of significant therapeutic value in human myasthenia gravis. Ann Neurol 2009;65:67,75 [source]

In vitro activity of dermaseptin S1 derivatives against genital pathogens

APMIS, Issue 9 2010
DIANELLA SAVOIA
Savoia D, Donalisio M, Civra A, Salvadori S, Guerrini R. In vitro activity of dermaseptin S1 derivatives against genital pathogens. APMIS 2010; 118: 674,80. The aim of this study was to evaluate the biological activity of nine dermaseptin-S1 (DRS-S1) derivatives (synthesized by solid-phase methods and purified) against different pathogens causing genital infections (Trichomonas vaginalis, Herpes simplex virus, Papillomavirus). The in vitro activity on T. vaginalis was determined by counting the protozoon in a hemocytometer after vital staining with trypan blue; antiviral activity of the compounds was tested on monolayers of Vero cells for Herpes simplex virus-1 (GFP) and on 293TT cells for human papillomavirus (HPV-16) pseudovirions (GFP). The cytotoxicity of the derivatives was assessed by evaluating both the hemolytic activity and the effect on Vero and 293TT cells. The DRS-S1 longer peptides demonstrated a superior activity on T. vaginalis but also a certain cytopathic effect. The compounds with 29 amino acids exhibited activity against the two viruses tested at concentrations not toxic to cells. The results obtained show that some of the synthetic peptides assessed have inhibitory activity against the pathogens tested, indicating a potential for the development of new molecules for use as topical microbicides to prevent the sexual transmission of microorganisms. [source]

Bactrocerin-1: A novel inducible antimicrobial peptide from pupae of oriental fruit fly Bactrocera dorsalis Hendel

ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 3 2009
Xiang-Li Dang
Abstract A novel antimicrobial peptide, Bactrocerin-1, was purified and characterized from an immunized dipteran insect, Bactrocera dorsalis. Bactrocerin-1 has 20 amino acid residues with a mass of 2,325.95 Da. The amino acid sequence of Bactrocerin-1 showed very high similarity to the active fragment (46V-65S-NH2) of Coleoptericin A. The composition of amino acid residues revealed that Bactrocerin-1 is a hydrophobic, positively charged, and Lys/Ile/Gly-rich peptide. Minimal growth inhibition concentration (MIC) measurements for synthesized Bactrocerin-1 showed a very broad spectrum of anti-microbial activity against Gram-positive bacteria, Gram-negative bacteria, and fungi. Bactrocerin-1 did not show hemolytic activity toward mouse red blood cells even at a concentration of 50,µM. Analysis of the Helical-wheel projection and the CD spectrum suggested that Bactrocerin-1 contains the amphipathic ,-helix. © 2009 Wiley Periodicals, Inc. [source]

Melectin: A Novel Antimicrobial Peptide from the Venom of the Cleptoparasitic Bee Melecta albifrons

CHEMBIOCHEM, Issue 17 2008
Václav, ovský Dr.
Abstract A novel antimicrobial peptide designated melectin was isolated from the venom of the cleptoparasitic bee Melecta albifrons. Its primary sequence was established as H-Gly-Phe-Leu-Ser-Ile-Leu-Lys-Lys-Val-Leu-Pro-Lys-Val-Met-Ala-His-Met-Lys-NH2 by Edman degradation and ESI-QTOF mass spectrometry. Synthetic melectin exhibited antimicrobial activity against both Gram-positive and -negative bacteria and it degranulated rat peritoneal mast cells, but its hemolytic activity was low. The CD spectra of melectin measured in the presence of trifluoroethanol and sodium dodecyl sulfate showed a high content ,-helices, which indicates that melectin can adopt an amphipathic ,-helical secondary structure in an anisotropic environment such as the bacterial cell membrane. To envisage the role of the proline residue located in the middle of the peptide chain on biological activity and secondary structure, we prepared several melectin analogues in which the Pro11 residue was either replaced by other amino acid residues or was omitted. The results of biological testing suggest that a Pro kink in the ,-helical structure of melectin plays an important role in selectivity for bacterial cells. In addition, a series of N- and C-terminal-shortened analogues was synthesized to examine which region of the peptide is related to antimicrobial activity. [source]

Impact of in vivo complement activation and cryoglobulins on graft outcome of HCV-infected renal allograft recipients

CLINICAL TRANSPLANTATION, Issue 1 2004
Stefan M Weiner
Abstract:, Background:, Chronic hepatitis C virus (HCV) infection is closely associated with mixed cryoglobulinemia. Cryoglobulins can activate complement leading to vascular damage. We examined whether cryoglobulinemia and complement turnover is associated with HCV infection in renal transplant recipients and whether this has an adverse effect on graft outcome. Methods:, Sera and fresh plasma from 31 HCV-RNA-positive patients after renal transplantation (group I) were studied for cryoglobulins, complement hemolytic activity (CH50), and complement split product C3d. In total, 80 HCV-negative renal transplant recipients (group II) and 72 untreated patients with chronic hepatitis C (group III) without renal transplantation served as controls. Results:, Cryoglobulins were detected in 45, 28, and 26% of the patients in group I, II, and III, respectively. A high cryocrit (>5%) was present only in patients of group III (p < 0.01%). Mean CH50 values were lower and C3d levels higher in HCV-positive patients (group I and III) compared with HCV-negative patients (p < 0.0001). Cryoglobulins were not associated with extrahepatic manifestations or graft dysfunction, except in five patients of group III demonstrating cryoglobulinemic vasculitis. HCV-positive renal transplant recipients with signs of complement activation showed a significantly greater increase of serum creatinine (0.88 ± 1.14 mg/dL) when compared with baseline than patients without complement activation (0.34 ± 0.37 mg/dL; p = 0.035). There was also a tendency toward a higher extent of proteinuria in patients with complement activation (1.38 ± 2.17 g/d vs. 0.50 ± 0.77 g/d; p = 0.25, NS). Conclusions:, Cryoglobulins are common in renal allograft recipients, but do not affect graft function. However, complement activation appears to be involved in chronic allograft dysfunction in HCV-infected recipients. [source]