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Biomedical subjects

C Stewart

Publications and source records attributed to C Stewart.

At least 55 records · Page 3Linked to original sources
PubMed1999

The detection of biomarkers of genotoxin exposure in the European flounder (Platichthys flesus) collected from the River Tyne Estuary.

The Tyne Estuary (North East England) is known to contain elevated levels of polycyclic aromatic hydrocarbons (PAH), compared with other less industrialised English waterways. Previous studies suggest that such contamination is responsible for the toxicity detected in invertebrate bioassays conducted on water and sediment samples collected from the Tyne. Here we present data from a biomonitoring study using hepatic DNA adducts (32P-postlabelling assay) and bile metabolites (synchronous fluorescence spectrometry) to investigate genotoxic exposure in flounder (Platichthys flesus) collected from three sites (Scotswood, Newcastle and Redheugh) along the Tyne Estuary. Flounder were also collected from a clean reference site, the Alde Estuary. Levels of bile metabolites (microgram kg-1 wet weight 1-OH pyrene equivalents) were elevated in flounder caught from the Tyne (Scotswood = 22,247 +/- 3408; Newcastle = 14,572 +/- 1888; Redheugh = 21,872 +/- 2935) compared with those collected from the Alde (632 +/- 56). The levels of DNA adducts (adducted nucleotides per 10(8) normal nucleotides) were also elevated in Tyne flounder (Scotswood = 24.6 +/- 3.2; Newcastle = 34.4 +/- 3.7; Redheugh = 27.6 +/- 6.3) compared with fish collected from the Alde (10.1 +/- 4.8), suggesting that a proportion of the bioavailable PAH was being converted into genotoxic metabolites. All DNA adduct profiles in flounder collected from the Tyne consisted of diagonal radioactive zones of radiolabelled adducts, which were not present in fish sampled from the Alde. The in vivo dosing of flounder with benzo[a]pyrene (BaP) to produced DNA adducts in similar chromatographic positions to the diagonal radioactive zones in the Tyne caught flounder are also described.

Animals↗
PubMed1999

An assessment of the genotoxic impact of the Sea Empress oil spill by the measurement of DNA adduct levels in selected invertebrate and vertebrate species.

The grounding of the Sea Empress oil tanker resulted in the release of 72,000 tonnes of crude oil into Milford Haven, Wales, UK. Our initial studies indicated that this contamination resulted in elevated levels of DNA adducts in one of the area's native marine species Lipophrys pholis [B.P. Lyons, J.S. Harvey, J.M. Parry, An initial assessment of the genotoxic impact of the Sea Empress oil spill by the measurement of DNA adduct levels in the intertidal teleost Lipophrys pholis, Mutat. Res. 390 (1997) 263-268]. These original studies were extended and the genotoxic impact of the oil contamination was investigated in the invertebrates Halichondria panicea and Mytilus edulis, along with the vertebrate fish species L. pholis, Pleuronectes platessa and Limanda limanda. DNA adduct levels were assessed in these species over a period of 2-17 months after the incident. The studies indicate differences in the impact of acute oil contamination upon vertebrate and invertebrate species. The oil contamination did not induce any detectable elevations in adduct levels in the invertebrate species H. panicea and M. edulis. In contrast, the oil contamination did appear to induce adducts in the vertebrate teleost species L. pholis, P. platessa and Lim. limanda. Despite some difficulties in sampling, the data obtained 12-17 months after the spill suggested that the affected species recovered from the oil contamination. While the studies indicate that the genetic impact of the oil contamination was less severe than might have been expected, it remains possible that the DNA adducts detected in the teleosts could lead to genetic changes in these species in the future.

Animals↗
PubMed1999

A 500-kb sequence-ready cosmid contig and transcript map of the MEN1 region on 11q13.

We have generated a transcript map of an approximately 1.2-Mb region from human chromosome band 11q13 between the loci VEGFB and CAPN1, which flank the multiple endocrine neoplasia type 1 (MEN 1) locus. In total, we isolated 144 cosmids from this region and generated a sequence-ready cosmid contig of the approximately 500-kb region between the neurexin locus and D11S2196E. We identified 54 genes/ESTs by sample sequencing and have constructed a transcript map of this region. Genes were found to be clustered in three regions, and one of these genes was identical to the recently identified MEN1 locus. Relative to the latter, we have mapped the positions of 13 known genes, 18 genes which show homology to genes from humans or other organisms, and 22 genes/ESTs that appear novel. In addition, we have ascertained the directions of transcription of some of these genes and have determined intergenic distances between many loci. Full characterization of some of these genes, as well as the novel ESTs, will be useful in identifying candidate genes for other diseases known to map to this chromosomal region.

Animals↗
PubMed1999

Increased oxidative stress brought on by pro-inflammatory cytokines in neurodegenerative processes and the protective role of nitrone-based free radical traps.

Nitrone-based free radical traps (NFTs) have been shown to be protective in several neurodegenerative models. Our research has strongly implicated that: A) several neurodegenerative conditions exhibit increased levels of pro-inflammatory cytokines which consequently result in increased levels of oxidative stress and B) that NFTs act in part by suppressing oxidative stress through suppression of the action of the cytokine cascade. Acquired Immune Deficiency Syndrome (AIDS) dementia complex (ADC) is one of several conditions where the data collected helped to develop these concepts. Novel observations include demonstration that IL-1beta acts on cultured brain glia cells to invoke protein nitration and oxidative stress and that low levels of PBN (alpha-phenyl tert-butyl nitrone) inhibit this effect. We interpret these data as indicating that PBN prevents IL-1beta mediated peroxynitrite formation. Additionally, we have found that the AIDS viral envelope protein gp120 upregulates mRNA for the cytokines TNF alpha and TNF beta in rat neonatal brain, and that PBN prevents this. Western blots of protein extracts showed upregulation of inducible nitric oxide synthase (iNOS) in gp120 treated neonatal rat brains, and that PBN prevented induction of this enzyme as well. These observations underscore the general concept that PBN inhibits the induction of genes which produce neurotoxic products, one of which is peroxynitrite formed by the reaction of nitric oxide with superoxide, and may act also by inhibiting the induction of cytokines which mediate pro-inflammatory conditions in the brain.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Safe mobilization of normal progenitors in advanced chronic myeloid leukemia with intensive chemotherapy and granulocyte-colony stimulating factor.

Twenty-one patients with advanced chronic myeloid leukemia (late chronic phase (n = 8), accelerated phase (n = 11) and blast crisis (n = 2)) were treated with idarubicin, cytarabine, and etoposide followed by G-CSF and subsequent collection of peripheral blood progenitor cells in the early recovery phase. Treatment was reasonably well tolerated with no deaths or intensive care admissions. Despite the advanced phase of disease and heavy pretreatment with cytotoxics and interferon-alfa, 11 of 21 patients (52%) achieved a cytogenetic response. Of the nine major cytogenetic responses (complete (n = 3) and partial (n = 6)), seven achieved adequate progenitor collections for consideration for autologous transplantation. The only predictor of response was disease duration (P = 0.02). With a median follow-up of 1171 days from treatment it appears unlikely that G-CSF contributed to disease progression. Survival post-IcE was predicted by disease stage (P = 0.0001). Intensive chemotherapy followed by G-CSF allowed adequate yields of predominantly Philadelphia chromosome negative progenitor cells to be obtained from one-third of patients with advanced CML.

Adult↗
PubMed1999

Prevalence of disease-related DNA polymorphisms among participants in a large cancer prevention trial.

Genetic susceptibility polymorphisms may be of substantial importance in the modulation of cancer risk. The prevalence for an array of polymorphic genes was determined in a cohort of male smokers who participated in a cancer prevention trial in Finland. A random sample of 120 individuals was selected from the trial cohort and the prevalence of variant alleles for nine genes was determined using a polymerase chain reaction-based approach. The prevalence values from this study were also compared with those of other populations derived from previous studies. Our results show that, with the exception of cytochrome P450-1A1 (CYP1A1) and cytochrome P450-2E1 (CYP2E1), all genes tested were sufficiently polymorphic to warrant an investigation of gene-environment studies. Most of the variant alleles, including alcohol dehydrogenase 3 (ADH3), glutathione-S-transferase (GSTM1), methionine synthase (MS), methylene tetrahydofolater reductase (MHTFR), CYP2E1 and CYP1A1, exhibited similar frequencies to other Caucasian populations. Interestingly, the prevalence of androgen receptor-CAG repeat (AR-CAG) and vitamin D receptor (VDR) polymorphisms differed significantly between the alpha-tocopherol, beta-carotene (ATBC) Study and other Caucasian populations. We present herein results from this survey and conclude that the ATBC study population in Finland is sufficiently heterogeneous to facilitate analysis of genetic polymorphisms and disease associations.

Adult↗
PubMed1999

Virulence properties of Escherichia coli 83972, a prototype strain associated with asymptomatic bacteriuria.

Little is known about bacteria associated with asymptomatic bacteriuria (ABU) with regard to urinary tract colonization mechanisms. In this study, virulence properties of Escherichia coli 83972, a strain that was isolated from a clinical ABU episode, were examined. The genetic potential for expression of P and type 1 pili was demonstrated, and DNA sequences related to type 1C and G (UCA) pilus genes were also detected. However, E. coli 83972 did not express D-mannose-resistant or D-mannose-sensitive hemagglutination after growth under standard conditions in vitro or upon isolation from the urine of colonized test subjects. Limited uroepithelial cell adherence was observed in vivo, and weak D-mannose-sensitive hemagglutination was detected after extended growth in urine in vitro.

Adhesins, Escherichia coli↗
PubMed1999

The use of dexamethasone in women with preterm premature rupture of membranes--a multicentre, double-blind, placebo-controlled, randomised trial. Dexiprom Study Group.

OBJECTIVE: To assess whether administration of dexamethasone in women with preterm premature rupture of membranes (PPROM) has an effect on the prevalence of maternal sepsis, neonatal respiratory distress syndrome (RDS), perinatal mortality and neonatal sepsis in a developing country. SETTING: Six public hospitals in South Africa that deal mainly with indigent women. METHOD: A multicentre, double-blind, placebo-controlled, randomised trial was performed on women with PPROM and fetuses of 28-34 weeks' gestation or clinically estimated fetal weight between 1,000 and 2,000 g if the gestational age was unknown. Women were randomised to receive either dexamethasone 24 mg intramuscularly or placebo in two divided doses 24 hours apart. All women received amoxycillin and metronidazole and were managed expectantly. Hexoprenaline was administered if contractions occurred within the first 24 hours after admission to the trial. OUTCOME MEASURES: The maternal outcome measures were clinical chorio-amnionitis and postpartum sepsis. The outcome measures for infants were perinatal death, RDS, mechanical ventilation, necrotising enterocolitis, and neonatal infection within 72 hours. RESULTS: One hundred and two women who delivered 105 babies were randomised to the dexamethasone group and 102 women who delivered 103 babies, to the placebo group. The groups were well balanced with regard to clinical features. There was a trend towards fewer perinatal deaths in the dexamethasone group: 4 compared with 10 (P = 0.16, odds ratio 0.37, 95% confidence intervals 0.09-1.34). A subanalysis of mothers who delivered more than 24 hours after admission to the study and their infants revealed a significant reduction in perinatal deaths; 1 death in the dexamethasone group and 7 in the placebo group, P = 0.047 (Fisher's exact test). No woman in either group developed severe sepsis, and the incidence of sepsis in the women did not differ significantly. Eleven infants in each group developed sepsis. CONCLUSION: This is the first randomised trial in women with PPROM to compare the effects of the use of corticosteroids with placebo, where all women received prophylactic antibiotics concomitantly with the corticosteroids. A trend towards an improved perinatal outcome was demonstrated in the women who received dexamethasone. There was no increased risk of infection in the women or their infants where dexamethasone was administered. Administration of corticosteroids to women with PPROM has more advantages than disadvantages in developing countries.

Anti-Inflammatory Agents↗
PubMed1999

Effect of vitamin intervention on the relationship between GSTM1, smoking, and lung cancer risk among male smokers.

The GSTM1 (glutathione S-transferase mu-1) null genotype is suspected of increasing an individual's susceptibility to tobacco smoke carcinogens because of impaired carcinogen detoxification. We were interested in whether there were differences in lung cancer susceptibility to smoking within the GSTM1 genotypes and the impact of antioxidant supplementation on this. For this purpose, we conducted a nested lung cancer case-control study and evaluated the role of GSTM1 within the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study. GSTM1 genotype status was determined for 319 cases and 333 controls using a PCR-based approach. GSTM1 was evaluated as an independent risk factor and as an effect modifier of smoking using logistic regression analyses. The GSTM1 null genotype itself was unrelated to risk of lung cancer, odds ratio (OR) = 1.09 and 95% confidence interval (CI), 0.79-1.50, but it may have modified the effect of smoking. There was a suggestion for a stronger association between years of smoking and lung cancer among the GSTM1 null genotype, but the differences between GSTM1 null and present genotypes were not statistically significant (P = 0.12). Furthermore, the smoking association was strongest among those with the GSTM1 null genotype not receiving alpha-tocopherol supplementation, whereas among those receiving alpha-tocopherol, there was no modification by GSTM1 on the association between smoking duration and lung cancer risk. Beta-carotene supplementation did not modify the relationship between GSTM1, smoking years, and lung cancer risk. In conclusion, GSTM1 is not associated with lung cancer risk in male smokers but may confer a higher susceptibility to cumulative tobacco exposure. This association may be attenuated by alpha-tocopherol but not by beta-carotene supplementation.

Adult↗
PubMed1999

Advanced directives, the right to die and the common law: recent problems with blood transfusions.

The Australian common law suffers from a lack of judicial authority on the right to die, in particular the right of patients to make anticipatory decisions to refuse treatment. Recent cases concerning the right of patients to refuse life-saving blood transfusions have highlighted the need for a substantial judicial clarification of this area. This article critically examines one of the most recent Australian cases in detail and compares its approach with those from other common countries. After taking this comparative analysis the article puts forth a common law model of anticipatory decision-making and examines how that model might work in the context of current legislative frameworks.

Advance Directive Adherence↗
PubMed1998

Characterization of the mouse Men1 gene and its expression during development.

The gene responsible for multiple endocrine neoplasia type 1 (MEN1), a heritable predisposition to endocrine tumours in man, has recently been identified. Here we have characterized the murine homologue with regard to cDNA sequence, genomic structure, expression pattern and chromosomal localisation. The murine Men1 gene spans approximately 6.7 kb of genomic DNA and is comprised of 10 exons with similar genomic structure to the human locus. It was mapped to the pericentromeric region of mouse chromosome 19, which is conserved with the human 11q13 band where MEN1 is located. The predicted protein is 611 amino acids in length and overall is 97% homologous to the human orthologue. The 45 reported MEN1 mutations which alter or delete a single amino acid in human all occur at conserved residues, thereby supporting their functional significance. Two transcripts of approximately 3.2 and 2.8 kb were detected in both embryonal and adult murine tissues, resulting from alternative splicing of intron 1. By RNA in situ hybridization and Northern analysis the spatiotemporal expression pattern of Men1 was determined during mouse development. Men1 gene activity was detected already at gestational day 7. At embryonic day 14 expression was generally high throughout the embryo, while at day 17 the thymus, skeletal muscle, and CNS showed the strongest signal. In selected tissues from postnatal mouse Men1 was detected in all tissues analysed and was expressed at high levels in cerebral cortex, hippocampus, testis, and thymus. In brain the menin protein was detected mainly in nerve cell nuclei, whereas in testis it appeared perinuclear in spermatogonia. These results show that Men1 expression is not confined to organs affected in MEN1, suggesting that Men1 has a significant function in many different cell types including the CNS and testis.

Amino Acid Sequence↗
PubMed1998

Mutant membrane protein toxicity.

This report describes an extensive mutational analysis of the most carboxyl-terminal membrane-spanning sequence of Escherichia coli lac permease (TM12). In addition to identifying residues important for lactose transport function, the analysis revealed that numerous mutations made lac permease highly toxic to cells. In the most extreme cases, production of such proteins at very low steady-state levels reduced cell viability greater than 10(4)-fold. Both frameshift and missense mutations led to toxicity, with the frameshift mutations having the strongest effects observed. The toxic missense mutations corresponded to changes in TM12 expected to interfere with membrane insertion or folding, such as the introduction of charged residues or prolines in the putative helix. The results suggest that cellular toxicity may be a relatively common consequence of mutations altering integral membrane protein folding. An analogous toxicity might contribute to the pathogenesis of several degenerative diseases caused by mutant membrane proteins, such as retinitis pigmentosa, Charcot-Marie-Tooth syndrome, and Alzheimer's disease.

Amino Acid Sequence↗
PubMed1998

The true cost of treating children.

Paediatric patients (compared with adults) require additional time, effort and skill from hospital staff caring for them. Many suggestions for making successive versions of AN-DRGs more child friendly have not been implemented. Rather than relying on age, the AN-DRG classification should allow a better definition of complexity within DRGs. The two groups of children who place a disproportionate burden on paediatric teaching centres are children under 3 years and those with congenital abnormalities and chronic illness. Cost weights are not specific for paediatric patients. The extra costs of caring for children are reflected in nursing costs, highlighting the importance of including nurse dependency data in any costing study.

Australia↗
PubMed1998

Case study: caudate glutamatergic changes with paroxetine therapy for pediatric obsessive-compulsive disorder.

Neurobiological models for obsessive-compulsive disorder (OCD) have consistently implicated the caudate nucleus in the pathophysiology of this disorder. OCD symptoms improved markedly in a 9-year-old boy treated with paroxetine, a selective serotonin reuptake inhibitor, for whom pre/posttreatment proton magnetic resonance spectroscopic examinations were acquired to assess the relationship between neurochemical profile in the caudate nucleus, symptom severity, and treatment with paroxetine. Striking changes of the glutamate resonance in the caudate were observed after 12 weeks of paroxetine treatment. These data provide further support for glutamatergic-serotonin pathway involvement in the caudate nucleus of OCD patients.

Caudate Nucleus↗
PubMed1998

Factors affecting levels of untreated caries in a sample of 14-15-year-old adolescents in Northern Ireland.

UNLABELLED: Dental caries experience in children in Northern Ireland is the highest in the United Kingdom. OBJECTIVE: The aims were to examine the levels of untreated decay in a sample of 14-15-year-old children from an area known to have high dental needs and to relate them to factors which affect dental attendance. METHOD: A sample of 470 pupils aged 14-15 years who attended the 4th form of second level schools in North and West Belfast was obtained and closed questionnaires were distributed 2 weeks prior to the dental examination. RESULTS: 417 pupils were included in the analysis (inclusion rate 88.7%). The mean D value was 1.52 and the D/DMFT mean was 0.31. Individual factors which had significant associations with untreated decay were social class, time since the last dental visit, dental anxiety ratings and the type of dentist attended (mean D of 2.78 for those attending community service dentists and 1.24 for those attending general dental practitioners). Stepwise multiple regression models were constructed with dependent variables of D and the D/DMFT ratio, and the above independent variables remained significantly related to the outcome variables, with the exception of the type of dentist attended. Those attending the community service had higher social needs and longer intervals since dental treatment. CONCLUSION: Factors related to dental attendance are important in relation to the level of untreated decay but exclusive analysis of the type of dental service attended can be misleading. An active approach is required in order to improve the status of pupils with the highest needs.

Adolescent↗
PubMed1998

Mutation analysis of the MEN1 gene in multiple endocrine neoplasia type 1, familial acromegaly and familial isolated hyperparathyroidism.

Multiple endocrine neoplasia type 1 (MEN 1) is an autosomal dominant disease characterized by neoplasia of the parathyroid glands, the endocrine pancreas, and the anterior pituitary gland. In addition, families with isolated endocrine neoplasia, notably familial isolated hyperparathyroidism (FIHP) and familial acromegaly, have also been reported. However, whether these families constitute MEN 1 variants or separate entities remains speculative as the genetic bases for these diseases are unclear. The gene for MEN 1 has recently been cloned and characterized. Using single strand conformation analysis (SSCA) and sequencing, we performed mutation analysis in: a) a total of 55 MEN 1 families from 7 countries, b) 13 isolated MEN 1 cases without family history of the disease, c) 8 acromegaly families, and d) 4 FIHP families. Mutations were identified in 27 MEN 1 families and 9 isolated cases. The 22 different mutations spread across most of the 9 translated exons and included frameshift (11), nonsense (6), splice (2), missense mutations (2), and in-frame deletions (1). Among the 19 Finnish MEN 1 probands, a 1466del12 mutation was identified in 6 families with identical 11q13 haplotypes and in 2 isolated cases indicating a common founder. One frameshift mutation caused by 359del4 (GTCT) was found in 1 isolated case and 4 kindreds of different origin and haplotypes; this mutation therefore represents a common "warm" spot in the MEN1 gene. By analyzing the DNA of the parents of an isolated case one mutation was confirmed to be de novo. No mutation was found in any of the acromegaly and small FIHP families, suggesting that genetic defects other than the MEN1 gene might be involved and that additional such families need to be analyzed.

Acromegaly↗