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Biomedical subjects

Paul Williams

Publications and source records attributed to Paul Williams.

At least 73 records · Page 4Linked to original sources
PubMed2004

Positive control of swarming, rhamnolipid synthesis, and lipase production by the posttranscriptional RsmA/RsmZ system in Pseudomonas aeruginosa PAO1.

In Pseudomonas aeruginosa, the small RNA-binding, regulatory protein RsmA is a negative control element in the formation of several extracellular products (e.g., pyocyanin, hydrogen cyanide, PA-IL lectin) as well as in the production of N-acylhomoserine lactone quorum-sensing signal molecules. RsmA was found to control positively the ability to swarm and to produce extracellular rhamnolipids and lipase, i.e., functions contributing to niche colonization by P. aeruginosa. An rsmA null mutant was entirely devoid of swarming but produced detectable amounts of rhamnolipids, suggesting that factors in addition to rhamnolipids influence the swarming ability of P. aeruginosa. A small regulatory RNA, rsmZ, which antagonized the effects of RsmA, was identified in P. aeruginosa. Expression of the rsmZ gene was dependent on both the global regulator GacA and RsmA, increased with cell density, and was subject to negative autoregulation. Overexpression of rsmZ and a null mutation in rsmA resulted in quantitatively similar, negative or positive effects on target genes, in agreement with a model that postulates titration of RsmA protein by RsmZ RNA.

Amino Acid Sequence↗
PubMed2004

Biofilm formation in Pseudomonas aeruginosa: fimbrial cup gene clusters are controlled by the transcriptional regulator MvaT.

Pseudomonas aeruginosa is an opportunistic bacterial pathogen which poses a major threat to long-term-hospitalized patients and individuals with cystic fibrosis. The capacity of P. aeruginosa to form biofilms is an important requirement for chronic colonization of human tissues and for persistence in implanted medical devices. Various stages of biofilm formation by this organism are mediated by extracellular appendages, such as type IV pili and flagella. Recently, we identified three P. aeruginosa gene clusters that were termed cup (chaperone-usher pathway) based on their sequence relatedness to the chaperone-usher fimbrial assembly pathway in other bacteria. The cupA gene cluster, but not the cupB or cupC cluster, is required for biofilm formation on abiotic surfaces. In this study, we identified a gene (mvaT) encoding a negative regulator of cupA expression. Such regulatory control was confirmed by several approaches, including lacZ transcriptional fusions, Northern blotting, and transcriptional profiling using DNA microarrays. MvaT also represses the expression of the cupB and cupC genes, although the extent of the regulatory effect is not as pronounced as with cupA. Consistent with this finding, mvaT mutants exhibit enhanced biofilm formation. Although the P. aeruginosa genome contains a highly homologous gene, mvaU, the repression of cupA genes is MvaT specific. Thus, MvaT appears to be an important regulatory component within a complex network that controls biofilm formation and maturation in P. aeruginosa.

Bacterial Proteins↗
PubMed2004

Incorporation of an invasive object.

The author discusses the experience of 'being invaded' that is sometimes communicated by certain severely disturbed patients. The complaint can sometimes be couched in terms of bodily suffering and such patients may state that they have the experience of a 'foreign body' inside. It is suggested that these patients have suffered severe early failure of containment of their projections, while at the same time they have incorporated primitive characteristics of the object that have been powerfully projected into them. An object that invades in this way, it is suggested, experiences a compulsive need to expel unbearable states of mind using others as a repository. The infant incorporates these violent projections as part of his own mental representational system, and normal identification processes are disrupted. There follows impairment of the development of the sense of self. Clinical examples of how the invasive experience manifests itself in the analytic setting and in the transference and countertransference are presented. It is argued that this highly complex form of early subject-object interaction (prior to the differentiation of psyche-soma) is more likely to be found in severely narcissistically disturbed individuals. Some reflections on the origins of invasive phenomena are given.

Adult↗
PubMed2003

Functional complementation of E. coli secD and secG mutants by Helicobacter pylori homologues.

The Sec machinery is one mechanism used by bacteria to translocate proteins across their cytoplasmic membrane. Most of the Sec components have been identified within the important gastric pathogen, Helicobacter pylori, however their functionality has not yet been demonstrated. Here we report the existence of putative homologues to the Sec components yajC (HP1450) and yidC (HP1551), and demonstrate the ability of the H. pylori secD (HP1550) and secG (HP1255) homologues to facilitate inner membrane translocation of the maltose-binding protein MalE, by complementation of the respective secretion-deficient Escherichia coli mutants, thus providing evidence of their functionality.

Amino Acid Sequence↗
PubMed2003

Side-chain-to-tail thiolactone peptide inhibitors of the staphylococcal quorum-sensing system.

The expression of many staphylococcal virulence factors are regulated by the agr locus via a two-component signal transduction system (TCSTS), which is activated in response to a secreted autoinducer peptide (AIP). By exploiting the unique chemical architecture of the naturally occurring AIP-1, several potent inhibitors of staphylococcal TCSTS were designed and synthesized using either a linear or branched solid-phase approach. These inhibitors are competitive binders and contain the crucial 16-membered side-chain-to-tail thiolactone peptide pharmacophore.

4-Butyrolactone↗
PubMed2003

The structure and mechanism of methanol dehydrogenase.

This is a review of recent work on methanol dehydrogenase (MDH), a pyrroloquinoline quinone (PQQ)-containing enzyme catalysing the oxidation of methanol to formaldehyde in methylotrophic bacteria. Although it is the most extensively studied of this class of dehydrogenases, it is only recently that there has been any consensus about its mechanism. This is partly due to recent structural studies on normal and mutant enzymes and partly due to more definitive work on the mechanism of related alcohol and glucose dehydrogenases. This work has also led to conclusions about the subsequent path of electrons and protons during the reoxidation of the reduced quinol form of the prosthetic group.

Alcohol Oxidoreductases↗
PubMed2003

Synthetic analogues of the bacterial signal (quorum sensing) molecule N-(3-oxododecanoyl)-L-homoserine lactone as immune modulators.

Comparative immune modulatory activity for a range of synthetic analogues of a Pseudomonas aeruginosa signal molecule, N-(3-oxododecanoyl)-l-homoserine lactone (3O, C(12)-HSL), is described. Twenty-four single or combination systematic alterations of the structural components of 3O, C(12)-HSL were introduced as described. Given the already defined immunological profile of the parent compound, 3O, C(12)-HSL, these compounds were assayed for their ability to inhibit murine and human leucocyte proliferation and TNF-alpha secretion by lipopolysaccharide (LPS) stimulated human leucocytes in order to provide an initial structure-activity profile. From IC(50) values obtained with a murine splenocyte proliferation assay, it is apparent that acylated l-homoserine lactones with an 11-13 C side chain containing either a 3-oxo or a 3-hydroxy group are optimal structures for immune suppressive activity. These derivatives of 3O, C(12)-HSL with monounsaturation and/or a terminal nonpolar substituent on the side chain were also potent immune suppressive agents. However, structures lacking the homoserine lactone ring, structures lacking the l-configuration at the chiral center, and those with polar substituents were essentially devoid of activity. The ability of compounds selected from the optimal activity range to modulate mitogen-driven human peripheral blood mononuclear cell proliferation and LPS-induced TNF-alpha secretion indicates the suitability of these compounds for further investigation in relation to their molecular mechanisms of action in TNF-alpha driven immunological diseases, particularly autoimmune diseases such as psoriasis, rheumatoid arthritis, and type 1 (autoimmune) diabetes.

Adjuvants, Immunologic↗
PubMed2003

Early development and quorum sensing in bacterial biofilms.

We develop mathematical models to examine the formation, growth and quorum sensing activity of bacterial biofilms. The growth aspects of the model are based on the assumption of a continuum of bacterial cells whose growth generates movement, within the developing biofilm, described by a velocity field. A model proposed in Ward et al. (2001) to describe quorum sensing, a process by which bacteria monitor their own population density by the use of quorum sensing molecules (QSMs), is coupled with the growth model. The resulting system of nonlinear partial differential equations is solved numerically, revealing results which are qualitatively consistent with experimental ones. Analytical solutions derived by assuming uniform initial conditions demonstrate that, for large time, a biofilm grows algebraically with time; criteria for linear growth of the biofilm biomass, consistent with experimental data, are established. The analysis reveals, for a biologically realistic limit, the existence of a bifurcation between non-active and active quorum sensing in the biofilm. The model also predicts that travelling waves of quorum sensing behaviour can occur within a certain time frame; while the travelling wave analysis reveals a range of possible travelling wave speeds, numerical solutions suggest that the minimum wave speed, determined by linearisation, is realised for a wide class of initial conditions.

Bacteria↗
PubMed2003

Cost-effectiveness of almotriptan and rizatriptan in the treatment of acute migraine.

BACKGROUND: Migraine is a common disorder that costs US employers billions of dollars each year in missed workdays and reduced productivity. Seven triptans, including almotriptan and rizatriptan, are recommended as first-line therapy for acute migraine. OBJECTIVE: The aim of this study was to assess the relative cost-effectiveness of almotriptan and rizatriptan in the treatment of acute migraine. METHODS: A model was built to compare almotriptan 12.5 mg and rizatriptan 10 mg for the treatment of a single, acute migraine attack. Cost-effectiveness (in year-1999 US dollars) was evaluated from the perspective of a US health care payer. Mean and incremental cost-effectiveness ratios (CERs) were calculated. The effectiveness measure was the proportion of patients who achieved sustained freedom from pain with no adverse events (SNAE). Data on sustained pain-free outcomes and adverse-event rates were obtained from a meta-analysis of oral triptan trials. Efficacy and tolerability were assumed to be independent in the base-case scenario, so the total direct cost of treating a single migraine attack was calculated, adding drug costs to health service costs per attack. RESULTS: In the base-case analysis, the mean CERs for almotriptan 12.5 mg and rizatriptan 10 mg were 91.12 dollars and 131.26 dollars, respectively, per attack at which SNAE was achieved after treatment. The incremental CER for almotriptan (compared with rizatriptan 10 mg) was 6.94 dollars per additional SNAE achieved. The economic benefit of almotriptan 12.5 mg was robust in a range of sensitivity analyses. CONCLUSION: Almotriptan 12.5 mg was more cost-effective than rizatriptan 10 mg for the treatment of acute migraine in this analysis based on published data.

Acute Disease↗
PubMed2003

Electrostatic sensor for identifying interactions between peptides and bacterial membranes.

The use of the membrane probe fluorescein phosphatidylethanolamine (FPE) to investigate membrane binding is well established. However, until now, its use has been restricted to studies involving peptides and eukaryotic membranes. This useful tool has been developed to interrogate peptide:prokaryotic membrane interactions by introducing novel methodology to incorporate FPE into the membranes of UV killed, whole bacterial cells. The electrostatic potential of the membrane in the immediate vicinity of the probe affects the protonation state of the xanthene ring system in the fluorescein head group, which is held close to the membrane surface. When altered, e.g. by peptide binding and insertion, a change in fluorescence results, which can be measured spectrophotometrically. Applicability of this technique to bacterial surface interactions was confirmed by production of a binding curve for both a synthetic peptide and a 37kDa protein. Future investigations are anticipated to utilize this technology to characterize interactions of other toxins plus antimicrobial peptides such as lactoferricin and defensins with their target membranes.

Bacteria↗
PubMed2003

The Pseudomonas aeruginosa quinolone signal molecule overcomes the cell density-dependency of the quorum sensing hierarchy, regulates rhl-dependent genes at the onset of stationary phase and can be produced in the absence of LasR.

In Pseudomonas aeruginosa, diverse exoproduct virulence determinants are regulated via N-acylhomoserine lactone-dependent quorum sensing. Here we show that 2-heptyl-3-hydroxy-4(1H)-quinolone (PQS) is also an integral component of the quorum sensing circuitry and is required for the production of rhl-dependent exoproducts at the onset of stationary phase. Analysis of spent P. aeruginosa culture supernatants revealed that PQS is produced at the end of exponential phase in the parent strain and in the late stationary phase of a lasR mutant. Mutants defective in both PQS production (pqsR-) and response (pqsE-) produced substantially reduced levels of exoproducts but retained wild-type N-butanoyl homoserine lactone (C4-HSL) levels. In the wild type, provision of exogenous PQS at the time of inoculation significantly increased PA-IL lectin, pyocyanin and elastase production during early stationary phase and promoted biofilm formation. Exogenous PQS but not PQS derivatives lacking the 3-hydroxy group overcame the cell density but not growth phase-dependent production of exoproducts. PQS also overcame the transcriptional and post-transcriptional repression of lecA (which codes for the PA-IL lectin) mediated via the negative regulators MvaT and RsmA respectively. Increased expression of lecA in the presence of exogenous PQS can be explained partially by increases in RhlR, RpoS and C4-HSL levels. A refined model for quorum sensing in P. aeruginosa is presented.

4-Butyrolactone↗
PubMed2003

Observing a fictitious stressful event: haematological changes, including circulating leukocyte activation.

The aim of this study was to assess the effect of watching a psychological stressful event on the activation of leukocytes in healthy human volunteers. Blood samples were obtained from 32 healthy male and female subjects aged between 20 and 26 years before, during and after either watching an 83-minute horror film that none of the subjects had previously seen (The Texas Chainsaw Massacre, 1974) or by sitting quietly in a room (control group). Total differential cell counts, leukocyte activation as measured by the nitroblue tetrazolium (NBT) test, heart rate and blood pressure (BP) measurements were taken at defined time points. There were significant increases in peripheral circulating leukocytes, the number of activated circulating leukocytes, haemoglobin (Hb) concentration and haematocrit (Hct) in response to the stressor. These were accompanied by significant increases in heart rate, systolic and diastolic BP (P<0.05 from baseline). This is the first reported study on the effects of observing a psychologically stressful, albeit fictitious event on circulating leukocyte numbers and the state of leukocyte activation as determined by the nitrotetrazolium test.

Adult↗
PubMed2003

Icodextrin improves the fluid status of peritoneal dialysis patients: results of a double-blind randomized controlled trial.

Worsening fluid balance results in reduced technique and patient survival in peritoneal dialysis. Under these conditions, the glucose polymer icodextrin is known to enhance ultrafiltration in the long dwell. A multicenter, randomized, double-blind, controlled trial was undertaken to compare icodextrin versus 2.27% glucose to establish whether icodextrin improves fluid status. Fifty patients with urine output <750 ml/d, high solute transport, and either treated hypertension or untreated BP >140/90 mmHg, or a requirement for the equivalent of all 2.27% glucose exchanges, were randomized 1:1 and evaluated at 1, 3, and 6 mo. Members of the icodextrin group lost weight, whereas the control group gained weight. Similar differences in total body water were observed, largely explained by reduced extracellular fluid volume in those receiving icodextrin, who also achieved better ultrafiltration and total sodium losses at 3 mo (P < 0.05) and had better maintenance of urine volume at 6 mo (P = 0.039). In patients fulfilling the study's inclusion criteria, the use of icodextrin, when compared with 2.27% glucose, in the long exchange improves fluid removal and status in peritoneal dialysis. This effect is apparent within 1 mo of commencement and was sustained for 6 mo without harmful effects on residual renal function.

Adult↗
PubMed2003

The cost-effectiveness of patient-applied treatments for anogenital warts.

A model was developed to estimate the cost-effectiveness of podophyllotoxin and imiquimod for self-treatment of anogenital warts. The effectiveness endpoint was sustained clearance after treatment and a subsequent follow-up period of approximately 12 weeks. Effectiveness of podophyllotoxin was estimated from a quantitative summary of nine placebo-controlled trials, while effectiveness of imiquimod was based on a quantitative summary of six placebo-controlled trials. Costs were considered from a UK health service provider perspective; drug acquisition costs were obtained from the British National Formulary and health service costs of clinic attendance were based on a recent survey of GUM clinics. The impact of uncertainty was explored in a wide range of one-way and probabilistic (multi-way) sensitivity analyses. The cost per sustained clearance was 313 for podophyllotoxin and 606 for imiquimod. The modest and statistically insignificant incremental effectiveness of imiquimod was purchased at high cost-2476 per additional sustained clearance. Sensitivity analyses showed the economic superiority of podophyllotoxin to be robust and statistically very significant.

Aminoquinolines↗