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Biomedical subjects

M Russel

Publications and source records attributed to M Russel.

At least 19 recordsLinked to original sources
PubMed2005

Survival of the probiotic, L. plantarum 299v and its effects on the faecal bacterial flora, with and without gastric acid inhibition.

INTRODUCTION: Probiotic bacteria have to survive passage through the gastrointestinal tract. In this placebo-controlled double-blind study, the effect of Lactobacillus plantarum 299v on the faecal flora was studied with and without gastric acid inhibition. METHODS: Thirty-two healthy volunteers were given pantoprazole (40 mg/day) or placebo for 3 weeks from week 2 until week 4. In addition, from week 3 until week 4, L. plantarum 299v in an oatmeal-fermented drink (10(9) CFU/ml) was given twice daily to both groups. From each healthy volunteer, faecal samples were collected at the end of week 1, 2, 4 and 8 (4 weeks after cessation of L. plantarum 299v and pantoprazole/placebo). Several aerobically and anaerobically growing bacteria were counted and short chain fatty acid concentrations were determined. RESULTS: In both the pantoprazole and the placebo group, median lactobacilli counts increased significantly in week 4 compared to week 1 (from log 4.5 to 8.0 CFU/g faeces in pantoprazole and from log 4.2 to 7.7 CFU/g faeces in placebo group) and decreased significantly in week 8 (to log 4.5 CFU/g faeces in pantoprazole and log 4.3 CFU/g faeces in placebo group). These lactobacilli were identified as L. plantarum 299v. No significant differences were observed in all other bacterial counts and short chain fatty acid concentrations. CONCLUSIONS: The comparable increase of faecal lactobacilli counts in both the pantoprazole and the placebo-treated group demonstrates that L. plantarum 299v survives passage through the gastrointestinal tract irrespective of gastric acidity. The increment of the intra-gastric pH in combination with L. plantarum 299v did not modulate bacterial composition and/or the production of short chain fatty acids.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed2003

The effect of Lactobacillus plantarum 299v on the bacterial composition and metabolic activity in faeces of healthy volunteers: a placebo-controlled study on the onset and duration of effects.

AIM: To study the onset and duration of a possible effect of a fermented oatmeal drink containing Lactobacillus plantarum 299v on the composition of the faecal flora of healthy volunteers in a placebo-controlled, double-blind study. METHODS: Twenty-two participants consumed a fermented oatmeal drink with or without L. plantarum 299v for 4 weeks. Faecal samples were collected weekly: two samples before, four during and four after the consumption of the drink. Several bacterial species were counted and enzyme activities, short-chain fatty acid concentrations, endotoxin concentration and pH were determined. L. plantarum 299v was identified using randomly amplified polymorphic DNA. RESULTS: In contrast with the placebo group, median lactobacilli counts increased significantly from 4.2 (3.4-6.3) to 8.2 (7.3-8.5) log colony-forming units/gram faeces (P = 0.005) after 1 week of consumption of L. plantarum 299v, thereafter remaining stable during the treatment period. One week after cessation, a significant decrease in lactobacilli [to 4.4 (2.2-6.5) log colony-forming units/gram faeces] was observed (P = 0.003). These lactobacilli were identified as L. plantarum 299v. All other bacterial counts, enzyme activities, short-chain fatty acid concentrations, endotoxin concentration and pH remained unchanged. CONCLUSIONS: L. plantarum 299v significantly increased the number of lactobacilli in the faecal flora within 1 week, and this effect disappeared within 1 week after cessation of intake. No other changes in bacterial counts and metabolic products were observed.

Adult↗
PubMed2003

Probiotics in gastroenterology: indications and future perspectives.

Nowadays. there is a growing interest in probiotics as a safe way of changing the intestinal bacterial flora. Probiotics may have potential in several gastroenterological conditions, especially when the intestinal flora has been disturbed. Most scientific evidence is available for diarrhoea patients treated with Lactobacillus GG, Lactobacillus reuteri or Saccharomyces boulardii. Meta-analyses have shown an overall reduction in the risk of antibiotic-associated diarrhoea during treatment with probiotics, and benefits have also been demonstrated for patients with rota-virus-associated diarrhoea. Patients with inflammatory bowel disease, an inflammatory disorder characterized by a change in the intestinal flora, are another important target group for which probiotics may be beneficial. It has been claimed that in ulcerative colitis and Crohn disease patients, lactobacilli, S. boulardii and Escherichia coli reduce relapses. but most studies were not placebo-controlled. A reduction in relapses has also been demonstrated in pouchitis patients treated with a multispecies probiotic. Irritable bowel syndrome might be another clinical indication for probiotic therapy, but results of clinical trials performed in these patients are inconsistent. Additionally, probiotics may improve lactose absorption. Helicobacter pylori eradication and constipation. Finally, in animal models of colorectal cancer, treatment with probiotics reduces the prevalence of this disease, and in humans the amount of genotoxic substances in faeces has been reduced. In conclusion, the results of studies on the effects of probiotics in gastrointestinal conditions are encouraging. but well-designed placebo-controlled studies are warranted before recommendations for therapeutic or preventive use can be given. Many issues still have to be resolved, including optimal dose and duration of treatment, selection of and differences between the several available probiotic strains, and, importantly, their mechanisms of actions have to be elucidated.

Colorectal Neoplasms↗
PubMed2001

Assembling filamentous phage occlude pIV channels.

Filamentous phage f1 is exported from its Escherichia coli host without killing the bacterial cell. Phage-encoded protein pIV, which is required for phage assembly and secretion, forms large highly conductive channels in the outer membrane of E. coli. It has been proposed that the phage are extruded across the bacterial outer membrane through pIV channels. To test this prediction, we developed an in vivo assay by using a mutant pIV that functions in phage export but whose channel opens in the absence of phage extrusion. In E. coli lacking its native maltooligosacharride transporter LamB, this pIV variant allowed oligosaccharide transport across the outer membrane. This entry of oligosaccharide was decreased by phage production and still further decreased by production of phage that cannot be released from the cell surface. Thus, exiting phage block the pIV-dependent entry of oligosaccharide, suggesting that phage occupy the lumen of pIV channels. This study provides the first evidence, to our knowledge, for viral exit through a large aqueous channel.

Coliphages↗
PubMed2001

Quality of health care in inflammatory bowel disease: development of a reliable questionnaire (QUOTE-IBD) and first results.

OBJECTIVES: As inflammatory bowel disease is a chronic disorder, usually with an early onset in life, quality of care plays an important role for patients. The aim of this study was to develop a questionnaire to measure quality of care through the eyes of patients with inflammatory bowel disease. METHODS: Ten generic questions were already available because the questionnaire is based on an existing instrument. Patients with inflammatory bowel disease in seven countries were involved in the development of additional disease-specific items. Validation and first field testing of the total questionnaire (QUOTE-IBD) was performed in The Netherlands. RESULTS: A total of 380 patients cooperated in the development of 13 disease-specific items, with high internal reliability (Cronbach's alpha = 0.83). Another 162 patients were involved in validating and testing of the QUOTE-IBD, which consists of 23 items in total. Pearson's correlation coefficient between QUOTE-IBD and visual analog scale scores of health care items was 0.55. Intraclass correlation coefficient of two assessments was 0.64. First testing showed that patients gave relatively poor marks to some part of health care services, such as providing information about extraintestinal complaints and the psychological as well as physical approach to complaints. CONCLUSIONS: A short, valid, reliable questionnaire was developed to measure the opinions of patients with inflammatory bowel disease on quality of health care. The QUOTE-IBD can be used for identification of areas for improvement, with the aim of optimizing health care in inflammatory bowel disease.

Europe↗
PubMed2000

Influence of quality of care on quality of life in inflammatory bowel disease (IBD): literature review and studies planned.

Inflammatory bowel disease (IBD) is a chronic disorder with an early onset in life. Therefore, it is reasonable to assume that IBD patients are in considerable need of health care. The quality of life of IBD patients is reported to be impaired. Whether optimizing the quality of health care for these patients may positively influence their quality of life is a question that has been raised often during recent years. This review of the literature on health care research discusses different concepts regarding the quality of care assessment in chronic disease, stresses the need to see things from the patient's perspective, and provides recommendations to optimize health care research. The two most important conclusions that can be drawn are that: (1) the relationship between quality of health care and quality of life in IBD is one that is certainly worth studying; and (2) when developing a means to assess patient data on quality of care, it is essential to involve patients from the very start.

Journal Article↗
PubMed1999

An aqueous channel for filamentous phage export.

Filamentous phage f1 exits its Escherichia coli host without killing the bacterial cell. It has been proposed that f1 is secreted through the outer membrane via a phage-encoded channel protein, pIV. A functional pIV mutant was isolated that allowed E. coli to grow on large maltodextrins and rendered E. coli sensitive to large hydrophilic antibiotics that normally do not penetrate the outer membrane. In planar lipid bilayers, both mutant and wild-type pIV formed highly conductive channels with similar permeability characteristics but different gating properties: the probability of the wild-type channel being open was much less than that of the mutant channel. The high conductivity of pIV channels suggests a large-diameter pore, thus implicating pIV as the outer membrane phage-conducting channel.

Anti-Bacterial Agents↗
PubMed1999

A trans-envelope protein complex needed for filamentous phage assembly and export.

Assembly and export of filamentous phage requires four non-capsid proteins: the outer membrane protein, pIV; the inner membrane proteins, pI and pXI; and a cytoplasmic host factor, thioredoxin. Chemical cross-linking of intact cells demonstrates a trans-membrane complex containing pI and pIV. Formation of the complex protects pI from proteolytic cleavage by an endogenous protease. This protection also requires pXI, which is identical to the C-terminal portion of pI. This indicates that pXI, which is required for phage assembly in its own right, is also part of the complex. This complex forms in the absence of any other phage proteins or the DNA substrate; hence, it represents the first preinitiation step of phage morphogenesis. On the basis of protease protection data, we propose that the preinitiation complex is converted to an initiation complex by binding phage DNA, thioredoxin and the initiating minor coat protein(s).

Bacteriophages↗
PubMed1998

Macromolecular assembly and secretion across the bacterial cell envelope: type II protein secretion systems.

A decade ago, Pugsley and colleagues reported the existence of a large region of Klebsiella DNA, distinct from the Klebsiella gene encoding pullulanase, which was necessary for secretion of this enzyme to the cell surface in Escherichia coli (d'Enfert et al., 1987a,b). The pul genes it contained proved to be the tip of an iceberg. The sequences reported before 1992 (d'Enfert et al., 1987a,b; d'Enfert & Pugsley, 1989; Pugsley & Reyss, 1990; Reyss & Pugsley, 1990) included only one gene (pulD) that matched any sequence in the data base; a 220 amino acid residue segment of PulD was 32% identical with a portion of the filamentous phage-encoded protein, pIV. But by the time the sequence of the 18.8 kb DNA fragment that contained the pul genes had been completed (Possot et al., 1992), reports of sets of homologous genes in several species of Gram-negative plant and animal pathogens had appeared. For the most part, these gene clusters were cloned by their ability to complement mutants that produced, but failed to secrete, proteins normally found in the extracellular milieu; when tested, the mutants showed reduced pathogenicity or were totally avirulent. The secreted proteins included hydrolytic enzymes such as cellulase and pectinase from plant pathogens, and proteases and toxins from animal pathogens. The multi-gene family necessary for secretion of these enzymes is now known as the type II system or the main terminal branch (MTB) of the general secretion pathway (GSP). As summarized by Pugsley et al. (1997), the current tally includes type II systems from Klebsiella oxytoca (pul), Erwinia chrysanthemi and carotovora (out), Xanthomonas campestris (xps), Pseudomonas aeruginosa (xcp), Aeromonas hydrophila (exe), and Vibrio cholerae (eps). A second type II system (sps) necessary for deposition of the S-layer on the cell surface in A. hydrophila is more similar to the X. campestris than A. hydrophila genes (Thomas & Trust, 1995). The biggest surprise has been the discovery of a complete set of type II secretion genes in E. coli K12. The E. coli genes are not expressed under normal growth conditions, and a search is underway to find inducing conditions and secretion substrates (Francetic & Pugsley, 1996). Impressive progress has already been made in defining components of the pathway. What remains to be understood in mechanistic detail is how this protein secretion system functions.

Bacterial Proteins↗
PubMed1998

The Salmonella typhimurium InvH protein is an outer membrane lipoprotein required for the proper localization of InvG.

The secretion of pathogenicity factors by Salmonella typhimurium is mediated by a type III secretion system that includes an outer membrane protein of the secretin family. Related secretins are also required for f1 phage assembly and type II secretion. When the C-terminal 43 amino acids of the S. typhimurium secretin InvG are added to f1 pIV, the chimeric f1 pIV-'InvG43 protein becomes dependent on the co-expression of another gene, invH, for function in phage assembly. [3H]-palmitic acid labelling, globomycin sensitivity and density gradient flotation were used to demonstrate that InvH is an outer membrane lipoprotein that is processed by signal peptidase II. A complex between chimeric f1 pIV-'InvG43 and InvH was demonstrated in vivo. InvH was shown to be required for the proper localization of InvG in the outer membrane and for the secretion of the virulence factor SipC. These results suggest that InvH and InvG are part of the functional outer membrane translocation complex in type III secretion systems.

Amino Acid Sequence↗
PubMed1997

The filamentous phage pIV multimer visualized by scanning transmission electron microscopy.

A family of homomultimeric outer-membrane proteins termed secretins mediates the secretion of large macromolecules such as enzymes and filamentous bacteriophages across bacterial outer membranes to the extracellular milieu. The secretin encoded by filamentous phage f1 was purified. Mass determination of individual molecules by scanning transmission electron microscopy revealed two forms, a unit multimer composed of about 14 subunits and a multimer dimer. The secretin is roughly cylindrical and has an internal diameter of about 80 angstroms, which is large enough to accommodate filamentous phage (diameter of 65 angstroms).

Biopolymers↗
PubMed1997

Filamentous phage assembly: variation on a protein export theme.

Biogenesis of both filamentous phage and type-IV pili involves the assembly of many copies of a small, integral inner membrane protein (the phage major coat protein or pilin) into a helical, tubular array that passes through the outer membrane. The occurrence of related proteins required for assembly and export in both systems suggests that there may be similarities at the mechanistic level as well. This report summarizes the properties of filamentous phage and the proteins required for their assembly, with particular emphasis on features they may share with bacterial protein export and pilus biogenesis systems, and it presents evidence that supports the hypothesis that one of the phage proteins functions as an outer membrane export channel.

Bacterial Outer Membrane Proteins↗
PubMed1997

A permeabilized cell system that assembles filamentous bacteriophage.

A permeabilized cell system has been developed that is capable of assembling filamentous phage only upon addition of exogenous thioredoxin. The in vitro system exhibits the same component requirements seen in vivo: functional thioredoxin, an intact packaging signal in the substrate DNA, and the assembly protein, pIV. This crude in vitro system is insensitive to inhibitors of protein or DNA synthesis, demonstrating that particle assembly uses components that had accumulated before cell permeabilization. The temporal separation of the synthetic period, during which phage proteins and DNA accumulate, from the assembly period enabled us to examine the energy requirement for assembly. We show here that ATP hydrolysis is required for filamentous phage assembly and that the proton motive force is also important.

Bacteriophages↗
PubMed1997

Module swaps between related translocator proteins pIV(f1), pIV(IKe) and PulD: identification of a specificity domain.

In Gram-negative bacteria, type II and type III secretion and filamentous phage assembly systems use related outer membrane proteins for substrate-specific transport across the outer membrane. We show here that the specificity domain of the phage f1 outer membrane protein pIV is contained within the 149 N-terminal amino acid residues. When the pIV(f1) specificity domain is fused to the translocator domain of the related pIV of phage IKe, the chimeric construct supports f1 but not IKe assembly. Functional coupling between the two domains in this chimeric construct is poor and is improved by a single amino acid change in the translocator domain of the pIV(IKe). In native pIV(IKe), two amino acid changes within its specificity domain are both necessary and sufficient to change the specificity from IKe to f1 assembly. Analysis of 39 chimeric constructs between pIV(f1) and the outer membrane protein PulD of the pullulanase secretion system failed to identify a comparable exchangeable specificity domain. These results indicate that the two domains may not function autonomously, and suggest that tertiary and quarternary changes of the entire translocator component rather than of an autonomous functional domain are required for specific translocation across the outer membrane.

Amino Acid Sequence↗
PubMed1997

The C-terminal domain of the secretin PulD contains the binding site for its cognate chaperone, PulS, and confers PulS dependence on pIVf1 function.

Related outer membrane proteins, termed secretins, participate in the secretion of macromolecules across the outer membrane of many Gram-negative bacteria. In the pullulanase-secretion system, PulS, an outer membrane-associated lipoprotein, is required both for the integrity and the proper outer membrane localization of the PulD secretin. Here we show that the PulS-binding site is located within the C-terminal 65 residues of PulD. Addition of this domain to the filamentous phage secretin, pIV, or to the unrelated maltose-binding protein rendered both proteins dependent on PulS for stability. A chimeric protein composed of bacteriophage f1 pIV and the C-terminal domain of PuID required properly localized PulS to support phage assembly. An in vivo complex formed between the pIV-PulD65 chimera and PulS was detected by co-immunoprecipitation and by affinity chromatography.

Amino Acid Sequence↗
PubMed1996

Activation of MEKK by formyl-methionyl-leucyl-phenylalanine in human neutrophils. Mapping pathways for mitogen-activated protein kinase activation.

Mechanisms of neutrophil activation in response to chemoattractants remain incompletely understood. We have recently reported a Ras-mediated c-Raf pathway leading to the activation of mitogen-activated protein (MAP) kinase in human neutrophils stimulated with the chemoattractant formyl-Met-Leu-Phe (FMLP). However, concern that Raf activation may not fully account for the early FMLP-mediated human neutrophil responses prompted us to investigate the activation of MAP kinase/ERK kinase (MEK) by MEK kinase (MEKK). In cell lysates we identified protein species at 180, 160, 110, 72, and 54 kDa with a monoclonal antibody to MEKK. Activation of MEKK was determined on immunoprecipitates from FMLP-stimulated neutrophils by in vitro kinase assay, which utilized both MEK1 and MEK2 as substrates. It was rapid, detectable at 30 s and reaching a plateau at 5 min, and it was inhibited in a dose-dependent fashion by a specific phosphatidylinositol 3-kinase inhibitor, wortmannin. Partial inhibition by pertussis toxin was observed. We were unable to show inhibition of the MEKK response by GF 109203X, a protein kinase C-specific inhibitor. These data indicate that in neutrophils activation of MEKK in addition to Raf may underlie stimulation of MAP kinase and other MAP kinase homologues by FMLP.

Androstadienes↗
PubMed1996

Expression and localization of HrpA1, a protein of Xanthomonas campestris pv. vesicatoria essential for pathogenicity and induction ofthe hypersensitive reaction.

The hrp cluster of the pepper and tomato pathogen Xanthomonas campestris pv. vesicatoria is required for both pathogenicity on susceptible host plants and induction of the hypersensitive reaction on resistant plants. The hrpA locus is located at the left end of the 25-kb hrp region and encodes a single 64-kDa Hrp protein, HrpA1, which belongs to the PulD superfamily of proteins involved in type II and type III protein secretion. In this study, we developed a defined medium without any plant-derived molecules that induces expression of hrpA in vitro. The hrpA transcription start site was mapped in the coding region of the hrpB8 gene, which is the last gene of the hrpB operon. The inducible hrpA promoter shows no homology to known promoter elements or other hrp loci of X. campestris pv. vesicatoria. hrpA expression was shown to be independent of the hrp regulatory gene hrpX. The amino acid sequence of the HrpA1 protein is predicted to contain an N-terminal signal sequence and no further transmembrane domains and to be rich in beta-sheet stretches. Expression of HrpA1 in Escherichia coli cells causes induction of the psp operon like some of its counterparts, suggesting some commonality of function and that HrpA1 forms multimers. The protein product of hrpA1 was identified by using a specific polyclonal antibody. Cell fractionation studies demonstrated that the HrpA1 protein is localized in the outer membrane of X. campestris pv. vesicatoria. HrpA1 is the first component of the Hrp secretion system whose localization has been determined in the original organism.

Amino Acid Sequence↗