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Biomedical subjects

K Duncan

Publications and source records attributed to K Duncan.

At least 19 recordsLinked to original sources
PubMed2006

Immune markers measured before treatment predict outcome of intensive phase tuberculosis therapy.

The development of a statistical model based on simple immunological markers which could predict the response to tuberculosis treatment would facilitate clinical trials of new anti-tuberculosis drugs. We have examined the ability of immunological biomarkers, measured at diagnosis and after 4 weeks of treatment, to predict sputum smear status at week 8. Eighteen tuberculosis patients with positive Ziehl-Nielsen (ZN)-stained sputum smears 8 weeks after initiation of treatment (slow response) were matched for age, gender, sputum smear grade and extent of disease on chest radiograph to 18 patients with negative sputum smears at week 8 (fast response). In addition to total white blood cell (WBC) counts and absolute lymphocyte, monocyte and neutrophil numbers, concentrations of six serum markers were measured by enzyme-linked immunosorbent assay (ELISA) in all patients (soluble interleukin-2 receptor alpha (sIL-2Ralpha), granzyme B, soluble tumour necrosis factor alpha receptors 1 and 2 (sTNF-R1 and -2), nitrotyrosine and interferon-gamma (IFN-gamma). At diagnosis, 4 biomarkers (sTNF-R1, total WBC, absolute monocyte and absolute neutrophil numbers) were significantly higher in slow response patients. At week 4, total WBC count and absolute monocyte and neutrophil numbers remained significantly higher in slow responders. Discriminant analysis of the diagnosis and week 4 data provided models for classification of slow response patients with 67% and 83% predictive accuracy. We suggest that treatment response phenotypes can be determined before the start of treatment. Reliable predictive models would allow targeted interventions for patients at risk for slow treatment response to standard tuberculosis therapy.

Adult↗
PubMed2006

An oral health education programme based on the National Curriculum.

AIM: The aim of this study was to develop and evaluate a teaching programme based on the national curriculum for use in a primary school setting. DESIGN: National Curriculum guidelines were combined with oral health education messages to draw up lesson plans for teachers to deliver. A questionnaire was used to demonstrate children's oral health knowledge prior to the teaching programme, and at 1 and 7 weeks following the programme. The study took place in inner-city, state-run primary schools in Manchester and North London, UK. The subjects were children between the ages of 7 and 8 years from Manchester (n = 58) and North London (n = 30). The main outcome measure was change in knowledge attributable to a newly developed teaching programme. RESULTS: The children in Manchester had a higher level of knowledge prior to the teaching programme. Following the teaching programme, children in both schools showed a significant improvement in dental health knowledge (P < 0.001). Seven weeks later, the Manchester children showed no significant loss of knowledge (P < 0.001). CONCLUSIONS: The aims of the National Curriculum were easily integrated with oral health messages. A more widely available teaching resource, such as the one described in this study, would be useful to encourage the teaching profession to take on oral health education without more costly input from dental professionals.

Child↗
PubMed2005

Aggregation of inertial particles in random flows.

We consider the trajectories of particles suspended in a randomly moving fluid. If the Lyapunov exponent of these trajectories is negative, the paths of these particles coalesce, so that particles aggregate. Here we give a detailed account of a method [B. Mehlig and M. Wilkinson, Phys. Rev. Lett. 92, 250602 (2004)] for calculating this exponent: it is expressed as the expectation value of a random variable evolving under a stochastic differential equation. We analyze this equation in detail in the limit where the correlation time of the velocity field of the fluid is very short, such that the stochastic differential equation is a Langevin equation. We derive an asymptotic perturbation expansion of the Lyapunov exponent for particles suspended in three-dimensional flows in terms of a dimensionless measure of the inertia of the particles, epsilon, and a measure of the relative intensities of potential and solenoidal components of the velocity field, Gamma. We determine the phase diagram in the epsilon-Gamma plane.

Journal Article↗
PubMed2005

Production of recombinant protein Pap31 and its application for the diagnosis of Bartonella bacilliformis infection.

Tropical bartonellosis is a highly fatal epidemic and endemic infectious disease that occurs throughout the communities of the Andes Mountains in South America. The disease is caused by the facultative intracellular bacteria, Bartonella bacilliformis. The emergence of bartonellosis in new geographic areas and an increase in the number of reported cases suggest the need for a rapid test for epidemiologic study and investigation of the disease burden. The objective of this research is to develop a rapid serologic diagnostic test using recombinant antigens to overcome the limitations of the current standard IFA technique for laboratory diagnosis. Western blot analysis with patient sera of whole cell lysate separated on a 2D gel identified Pap31 as a dominant antigen. PCR primers were designed according to the sequence of ATCC strain 35685 to amplify the gene coding for Pap31 from a local isolate (HOSP 800-09, Peru). The amplicon was subsequently cloned into pET24a, adding the T7 tag, and expressed in E. coli. Patient sera with different IFA titers confirmed the diagnostic band of 31 kDa on a Western blot of SDS-PAGE. The performance of affinity-purified recombinant Pap31 (rPap31) was also evaluated in an ELISA format with 137 patient sera of known IFA titers. The range of ELISA reading from positive sera did not overlap with the range of those from negative sera, suggesting the potential application of rPap31 in both ELISA for high throughput regional hospital settings and in the construction of handheld rapid tests for rural clinical sites.

Antigens, Bacterial↗
PubMed2004

The Mycobacterium tuberculosis dosRS two-component system is induced by multiple stresses.

Induction of the Mycobacterium tuberculosis dosR gene, which is known to respond to hypoxia, was measured using RTq-PCR following exposure to different stresses. Increased expression was seen after exposure to S-nitrosoglutathione (GSNO), ethanol and (to a lesser extent) H2O2, but not heat- or cold-shock. We also demonstrated that hspX, which is dependent on dosR for expression, is induced when cultures are left standing for 30 min, while significant but minor induction was seen following a 10 min centrifugation. Microarray analysis was used to compare gene expression in wild-type and deltadosR strains following 30 min standing. Fifty-two genes were significantly up-regulated, and 19 genes were down-regulated. These included genes that had previously been reported as being part of the dosR regulon, and also some novel ones.

DNA, Bacterial↗
PubMed2004

Identification and validation of novel drug targets in tuberculosis.

There is an urgent need for new antimycobacterial drugs, and in particular for novel agents that will shorten the duration of tuberculosis chemotherapy, or overcome drug-resistant strains of the causative organism, Mycobacterium tuberculosis. Our knowledge of the tubercle bacillus and its complex interaction with the human host has improved dramatically in recent years, particularly with the determination of its complete genome sequence. New genome-scale tools are being applied to aid in drug target identification, alongside traditional approaches aimed at understanding the basic biology of M. tuberculosis. Many potential drug targets have been identified, but very few have been validated by showing that they are essential for growth or survival of the bacterium. In this review, the landscape of potential drug targets is surveyed.Structural Bioinformatic Approaches to the Discovery of New Antimycobacterial Drugs.

Animals↗
PubMed2003

Unusual manifestations in X-linked amelogenesis imperfecta.

This paper describes a female with X-linked amelogenesis imperfecta (XAI). This case is unusual in having taurodontism, pulpal calcifications, coronal defects prior to tooth eruption and unerupted teeth. These findings have been reported in some cases of autosomal dominant and autosomal recessive AI but have not previously been documented in XAI.

Adolescent↗
PubMed2001

Galactan biosynthesis in Mycobacterium tuberculosis. Identification of a bifunctional UDP-galactofuranosyltransferase.

The cell wall of Mycobacterium tuberculosis and related genera is unique among prokaryotes, consisting of a covalently bound complex of mycolic acids, D-arabinan and D-galactan, which is linked to peptidoglycan via a special linkage unit consisting of Rhap-(1-->3)-GlcNAc-P. Information concerning the biosynthesis of this entire polymer is now emerging with the promise of new drug targets against tuberculosis. Accordingly, we have developed a galactosyltransferase assay that utilizes the disaccharide neoglycolipid acceptors beta-d-Galf-(1-->5)-beta-D-Galf-O-C(10:1) and beta-D-Galf-(1-->6)-beta-D-Galf-O-C(10:1), with UDP-Gal in conjunction with isolated membranes. Chemical analysis of the subsequent reaction products established that the enzymatically synthesized products contained both beta-D-Galf linkages ((1-->5) and (1-->6)) found within the mycobacterial cell, as well as in an alternating (1-->5) and (1-->6) fashion consistent with the established structure of the cell wall. Furthermore, through a detailed examination of the M. tuberculosis genome, we have shown that the gene product of Rv3808c, now termed glfT, is a novel UDP-galactofuranosyltransferase. This enzyme possesses dual functionality in performing both (1-->5) and (1-->6) galactofuranosyltransferase reactions with the above neoglycolipid acceptors, using membranes isolated from the heterologous host Escherichia coli expressing Rv3808c. Thus, at a biochemical and genetic level, the polymerization of the galactan region of the mycolyl-arabinogalactan complex has been defined, allowing the possibility of further studies toward substrate recognition and catalysis and assay development. Ultimately, this may also lead to a more rational approach to drug design to be explored in the context of mycobacterial infections.

Bacterial Proteins↗
PubMed2000

A putative ubiquitin ligase required for efficient mRNA export differentially affects hnRNP transport.

BACKGROUND: In the nucleus, mRNAs are bound by hnRNP proteins. A subset of hnRNP proteins shuttle between the nucleus and cytoplasm and are believed to promote mRNA export by acting as adaptors between mRNA and the transport machinery. The existence of multiple shuttling hnRNP proteins raises the question of whether differentially regulated, hnRNP-specific mRNA export pathways exist. RESULTS: We have determined that Tom1p, a conserved protein with a hect (homology to E6-AP carboxyl terminus) E3 ubiquitin ligase domain, is required for efficient mRNA export in S. cerevisiae, yet differentially affects hnRNP protein localization and export. Mutations in tom1 predicted to abolish ubiquitin ligase activity block efficient export of Nab2p and mRNA, causing Nab2p-mRNA complexes to accumulate in a punctate pattern coincident with the nuclear pore complex (NPC). Notably, the subcellular distribution of several other hnRNP proteins is not affected. In particular, Np13p remains mRNA-associated and continues to be efficiently exported in tom1 mutants. CONCLUSION: Our results demonstrate that mutations predicted to affect the enzymatic activity of the Tom1p ubiquitin ligase differentially affect export of hnRNP proteins in association with mRNA. We propose the existence of multiple mRNA export pathways, with export of Nab2p-associated mRNAs dependent on a branch of the ubiquitin protein modification pathway.

Amino Acid Sequence↗
PubMed2000

Apparent confined placental mosaicism of trisomy 16 and multiple fetal anomalies: case report.

Trisomy 16 is frequently found confined to the placenta (confined placental mosaicism (CPM)), with a structurally normal fetus. In some cases of trisomy 16, the fetus has uniparental disomy for chromosome 16 (UPD16) which is associated with intrauterine growth restriction (IUGR) and fetal anomalies. We report a case of apparent confined placental mosaicism for trisomy 16, using standard cytogenetic techniques, but with multiple fetal abnormalities including congenital diaphragmatic hernia in which there was no evidence of UPD in the disomic tissues examined. Subsequent examination of fetal tissues using fluorescent in situ hybridization (FISH) demonstrated low levels of mosaicism for trisomy 16 in all the tissues examined. The use of FISH permits identification of mosaicism which conventional techniques may not identify.

Abnormalities, Multiple↗
PubMed2000

Middle cerebral artery peak systolic velocity in the prediction of fetal anemia.

OBJECTIVE: The fetal middle cerebral artery peak systolic velocity (MCA PSV) has been suggested as a potential test to predict the fetal hematocrit level. We tested the hypothesis that a low fetal hematocrit is associated with an increase in MCA PSV in a prospective study of normal and alloimmunized pregnancies. METHODS: Fetal hematocrit and MCA PSV were obtained in 26 alloimmunized fetuses, immediately before their first fetal blood transfusions between 15 and 35 weeks. Results were compared with the MCA PSVs from 170 control fetuses not at risk of alloimmune anemia between 13 and 37 weeks. RESULTS: In control fetuses, PSV varied with gestation (PSV = 0.56 - 0.032 GA + 0.00086 GA2, where GA is gestational age; R2 = 0.41). The correlation between PSV and hematocrit Z scores (Pearson correlation coefficient r = -0.69) was highly significant (P = 0.0001). Using a PSV > 1 SD, the sensitivity of the test in predicting a fetal hematocrit < 2 SD below the mean was only 64% but the specificity was 100%. However, the sensitivity of the test in predicting a fetal hematocrit < 3 SD and < 4 SD rose to 73% and 83%, while the specificity was still good (93% and 80% respectively). CONCLUSIONS: MCA PSV and fetal hematocrit are highly significantly correlated. The sensitivity of the test was good and the high positive predictive value indicates that the presence of a raised PSV (defined as > 1 SD) is a strong indicator of fetal anemia. In conclusion, MCA PSV is a useful test in clinical practice for the detection of fetal anemia.

Adult↗
PubMed2000

Effects of performance feedback on patient pain outcomes.

The purpose of this study was to examine the effects of an individual feedback intervention provided to nurses on selected patient outcomes related to postoperative pain management Individual performance feedback served as the intervention. Thirty orthopedic staff nurses received feedback information on their past performance of recommended pain management practices. Data were collected preintervention and postintervention on selected patient pain outcomes from the medical records of 240 patients who had undergone total knee arthroplasty. The patient outcome measures were mean 4-hour pain intensity ratings, mean highest pain intensity ratings, mean number of times pain ratings exceeded patients' acceptable level of pain, mean administered morphine equivalents, and mean pain ratings on reassessment following analgesia administration. An improvement was noted in all pain outcomes following the feedback intervention. Results indicate that providing nurses with feedback on their past performance of pain management practices may contribute to decreased postoperative pain.

Aged↗
PubMed2000

Biotreatment of refinery spent-sulfidic caustic using an enrichment culture immobilized in a novel support matrix.

Sodium hydroxide solutions are used in petroleum refining to remove hydrogen sulfide (H2S) and mercaptans from various hydrocarbon streams. The resulting sulfide-laden waste stream is called spent-sulfidic caustic. An aerobic enrichment culture was previously developed using a gas mixture of H2S and methyl-mercaptan (MeSH) as the sole energy source. This culture has now been immobilized in a novel support matrix, DuPont BIO-SEP beads, and is used to bio-treat a refinery spent-sulfidic caustic containing both inorganic sulfide and mercaptans in a continuous flow, fluidized-bed column bioreactor. Complete oxidation of both inorganic and organic sulfur to sulfate was observed with no breakthrough of H2S and < 2 ppmv of MeSH produced in the bioreactor outlet gas. Excessive buildup of sulfate (> 12 g/L) in the bioreactor medium resulted in an upset condition evidenced by excessive MeSH breakthrough. Therefore, bioreactor performance was limited by the steady-state sulfate concentration. Further improvement in volumetric productivity of a bioreactor system based on this enrichment culture will be dependent on maintenance of sulfate concentrations below inhibitory levels.

Biotechnology↗
PubMed1999

Transgenic expression of green fluorescent protein in mouse oxytocin neurones.

Routine targeting of neurones for expression of exogenous genes would facilitate our ability to manipulate their internal milieu or functions, providing insight into physiology of neurones. The magnocellular neurones of the paraventricular and supraoptic nuclei of the hypothalamus have been the objects of limited success by this approach. Here we report on the placement of the enhanced green fluorescent protein (eGFP) coding sequence at various locations within an oxytocin transgene. Placement within the first exon yielded little to no expression, whereas placement in the third exon (as an in-frame fusion with the carboxyl terminus of the oxytocin preprohormone) resulted in cell-specific expression of eGFP in oxytocin neurones. Furthermore, placement of the eGFP sequence downstream of a picornavirus internal ribosomal entry site (IRES), also in the third exon, allowed expression of the eGFP as a separate protein. Other coding sequences should now be amenable to expression within oxytocin neurones to study their physiology.

Animals↗
PubMed1998

Improved fluorometric and chromatographic methods for the quantification of fumonisins B(1), B(2) and B(3).

Fumonisins pose serious health risks to humans and livestock, making their detection imperative in foods and feedstuffs. This detection can be accomplished quickly, precisely and accurately in a two-step chromatographic process. In the first step, fumonisins are extracted from a sample and isolated on an immunoaffinity column. In the second step, fumonisins are converted to fluorescent derivatives and quantified either through high-performance liquid chromatography (HPLC) or by fluorometer. These methods offer significant improvements in performance compared to earlier technology: limits of detection as low as 0.016 micrograms/g with HPLC-based detection and 0.25 micrograms/g for fluorometer-based detection; greater assay linearity (with HPLC, r = 0.997; with fluorometer, r = 0.998); larger immunoaffinity column capacity (77% recovery at 12.5 micrograms) and extended assay range (0-10 micrograms/g) for methods. The percentage recovery of fumonisins over the entire assay range averaged 83% for both the fluorometer and HPLC methods. Precision studies were performed for both the fluorometer and the HPLC methods. The average coefficient of variation was 14% for the fluorometer method and 8.3% for the HPLC method. As a result of the efficient separation, the improved HPLC method offers the advantage of precise individual quantification of FB1, FB2 and FB3. The two methods were compared using 33 naturally or artificially contaminated corn samples. Linear regression analysis demonstrated an excellent correlation (r = 0.996) between the two techniques. Higher recoveries of fumonisins were obtained using this HPLC method than with the official AOAC method.

Carboxylic Acids↗
PubMed1998

Stereochemical course of enzymatic enolpyruvyl transfer and catalytic conformation of the active site revealed by the crystal structure of the fluorinated analogue of the reaction tetrahedral intermediate bound to the active site of the C115A mutant of MurA.

MurA (UDP-GlcNAc enolpyruvyl transferase), the first enzyme in bacterial peptidoglycan biosynthesis, catalyzes the enolpyruvyl transfer from phosphoenolpyruvate (PEP) to the 3'-OH of UDP-GlcNAc by an addition-elimination mechanism that proceeds through a tetrahedral ketal intermediate. The crystal structure of the Cys115-to-Ala (C115A) mutant of Escherichia coli MurA complexed with a fluoro analogue of the tetrahedral intermediate revealed the absolute configuration of the adduct and the stereochemical course of the reaction. The fluorinated adduct was generated in a preincubation of wild-type MurA with (Z)-3-fluorophosphoenolpyruvate (FPEP) and UDP-GlcNAc and purified after enzyme denaturation. The fluorine substituent stabilizes the tetrahedral intermediate toward decomposition by a factor of 10(4)-10(6), facilitating manipulation of the adduct. The C115A mutant of MurA was utilized to avoid the microheterogeneity that arises in the wild-type MurA from the attack of Cys115 on C-2 of FPEP in competition with the formation of the fluorinated adduct. The crystal structure of the complex was determined to 2.8 A resolution, and the absolute configuration at C-2 of the adduct was found to be 2R. Thus, addition of the 3'-OH of UDP-GlcNAc is to the 2-si face of FPEP, corresponding to the 2-re face of PEP. Given the previous observation that, in D2O, the addition of D+ to C-3 of PEP proceeds from the 2-si face [Kim, D. H., Lees, W. J., and Walsh, C. T. (1995) J. Am. Chem. Soc. 117, 6380-6381], the addition across the double bond of PEP is anti. Also, because the overall stereochemical course has been shown to be either anti/syn or syn/anti [Lees, W. J., and Walsh, C. T. (1995) J. Am. Chem. Soc. 117, 7329-7337], it now follows that the stereochemistry of elimination of H+ from C-3 and Pi from C-2 of the tetrahedral intermediate of the reaction is syn.

Alkyl and Aryl Transferases↗