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Biomedical subjects

M J Stewart

Publications and source records attributed to M J Stewart.

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

Detection of poisoning by Impila (Callilepis laureola) in a mother and child.

Poisoning with impila (Callilepis laureola) is a recurring phenomenon in South Africa. Cases of poisoning with other plants which contain atractyloside also occur in Europe and the Americas. Since poisoning leads to rapid death from renal and/or hepatic failure, it is suspected that many cases are undiagnosed; this is especially so in South Africa, where patients may die without reaching hospital and do not often admit to ingestion of a traditional remedy. We have developed a thin layer chromatographic method for the detection of impila constituents in urine. We describe the clinical symptoms and the application of the screening method to diagnosis in the case of a mother and child, who both showed symptoms of impila poisoning; the mother died but the child survived. This method is rapid and may be used for the definitive diagnosis in cases of poisoning with atractyloside-containing plants.

Adult↗
PubMed1999

An A/G polymorphism in the promoter of mitochondrial aldehyde dehydrogenase (ALDH2): effects of the sequence variant on transcription factor binding and promoter strength.

INTRODUCTION: The strong protective effect of the ALDH2*2 mutation on risk of alcoholism suggests that other mutations that reduce mitochondrial aldehyde dehydrogenase (ALDH) activity in the liver might also deter drinking. This study describes a polymorphic locus found in the promoter of the ALDH2 gene that affects expression of reporter constructs. METHODS: Polymerase chain reaction (PCR)-based sequencing was used to search for polymorphisms. The ability of the promoter variants to bind transcription factors apolipoprotein A regulatory protein 1 (ARP-1) and chicken ovalbumin upstream promoter-transcription factor (COUP-TF) was tested in gel retardation assays using in vitro synthesized transcription factors. The variant promoters were tested for transcriptional activity using a heterologous promoter system and transient transfection assays. RESULTS: A common polymorphism (A or G) in the human ALDH2 promoter region was found at -361 base pair (bp) from the translation start site. This polymorphism was found at different frequencies in African Americans, Caucasians, and Asians. The polymorphism occurs adjacent to the core binding motif for the transcription factors COUP-TF and ARP-1. Competition and binding affinity determinations did not show differences in the ability of these two sequences to bind the factors. Reporter genes containing these elements upstream of a basal thymidine kinase promoter had similar activity when transfected into a fibroblast (CV-1) cell line. However, the reporter containing the G allele was more active than that containing the A allele in hepatoma (H4IIEC3) cells. CONCLUSIONS: The -361 bp A/G polymorphism is common in all racial groups tested. The G allele was more active than the A allele in a transfection assay. The basis for this difference is not known. If the differences in activity of the promoter constructs were paralleled by differences in ALDH2 enzyme activity in the liver, this polymorphism could affect risk of alcoholism.

Aldehyde Dehydrogenase↗
PubMed1999

Oxygenation is not improved by partial liquid high frequency ventilation using a high lung volume strategy. An experimental study.

OBJECTIVE: To investigate the effect on oxygenation and lung damage of partial perfluorocarbon liquid high frequency oscillatory ventilation (PL-HFOV) versus high frequency oscillatory ventilation (HFOV) alone, in rabbits with acute lung injury, using high lung volume strategy HFOV. METHODS: Twelve adult New Zealand white rabbits were initially ventilated with HFOV after anaesthesia, sedation and paralysis. After induction of lung injury with saline lavage, all animals received a single sigh breath of 30 cmH(2)O for 30 seconds. They were then allocated to receive either HFOV alone (n = 6) or PL-HFOV (n = 6). Arterial blood gases were taken pre- and post-lavage and then hourly for 5 hours. The oxygenation index (OI, in cmH(2)O/mmHg) was calculated using the formula: OI = (MAP x F(I)O(2) x 100) / PaO(2). The lungs were then removed for histological examination to score lung injury. RESULTS: Two rabbits died in the PL-HFOV group and none in the HFOV group, p = 0.45 (Fisher's exact test). At one hour the oxygenation index (OI) was 4.5 in the HFOV group and 6.6 in the PL-HFOV group, p = 0.49 and the PaO(2) was 374 mmHg in the HFOV group and 311 mmHg in the PL-HFOV group, p = 0.39. Average OI over the first three hours was 3.6 in the HFOV group and 5.0 in the PL-HFOV group, p = 0.27 and the PaO(2) was 404 mmHg in the HFOV group and 337 mmHg in the PL-HFOV group, p = 0.12. The lung histology damage score was 2.33 in the HFOV group and 2.50 in the PL-HFOV group, p = 0.83. CONCLUSIONS: In this model of acute lung injury, using a high volume HFOV strategy to optimise lung recruitment, PL-HFOV did not result in any further improvement in oxygenation when compared with HFOV alone. The question of safety with PL-HFOV remains.

Journal Article↗
PubMed1998

Regulation of the c-jun gene in p210 BCR-ABL transformed cells corresponds with activity of JNK, the c-jun N-terminal kinase.

Activity of the c-jun N-terminal kinase (JNK) has been shown in hematopoietic cells transformed by p210 BCR-ABL. However, analysis has not been reported for hematopoietic cells on the consequences of this activity for c-jun promoter regulation within its distinctive proximal 8-base consensus CRE-like element, an element linked to JNK-mediated increase in c-jun transcription. In the present study, regulation of the proximal c-jun promoter was studied in murine myeloid cells transformed by p210 BCR-ABL. Promoter regulation in p210 BCR-ABL transformed cells was compared with regulation of the promoter in nontransformed interleukin-3 (IL-3)-dependent parental cells. The composition of nuclear AP-1 proteins contained within cells with p210 BCR-ABL, and their binding to the c-jun promoter proximal CRE-like element, was compared with the composition and binding of AP-1 proteins in IL-3-treated parental cells without p210 BCR-ABL. The present analysis found fivefold increased c-jun transcription occurring in p210 BCR-ABL transformed murine myeloid cells possessing a corresponding magnitude of increased kinase activity of JNK, compared with IL-3-stimulated parental cells. Augmented JNK activity was accompanied by increased nuclear abundance of c-jun and c-fos proteins that bound specifically to the proximal c-jun promoter CRE element. Also, representative human leukemic cell lines expressing p210 BCR-ABL and possessing abundant kinase activity of JNK, when compared with parental cells that were deficient in JNK activity, had increased c-jun and c-fos proteins. Finally, to show the relevance of these observations in model systems, we studied blast cells from patients with Philadelphia chromosome-positive acute leukemic transformation, and observed comparable activities of JNK catalysis and c-jun/AP-1 protein relative to the cell lines that possessed p210 BCR-ABL and JNK activity. These studies provide a basis for investigating the set of downstream genes which augmented c-jun/AP-1 activity enlists in the process of transformation by p210 BCR-ABL.

Animals↗
PubMed1998

Binding and activation of the human aldehyde dehydrogenase 2 promoter by hepatocyte nuclear factor 4.

Mitochondrial aldehyde dehydrogenase 2 (ALDH2) is expressed in a tissue-specific fashion with high levels in liver, heart, kidney, and muscle, and low levels in most other tissues. The ALDH2 promoter was found to bind nuclear proteins at a pair of adjacent sites approximately 300 bp upstream from the translation start site, each of which was contacted at motifs containing the hexamer A/GGGTCA. The 3' site was shown to bind in vitro translated HNF-4. It was also shown by electrophoretic mobility shift assay utilizing antibodies against nuclear factors and rat liver nuclear extracts to be bound by hepatocyte nuclear factor 4 (HNF-4), chicken ovalbumin upstream promoter transcription factor I and II, and retinoid X receptors. A reporter construct containing four copies of this promoter element was activated by co-transfection of an HNF-4 expression plasmid in COS-1 and hepatoma cell lines. These results suggest that the tissue specificity of ALDH2 expression is in part determined by its activation by HNF-4.

Aldehyde Dehydrogenase↗
PubMed1998

The toxicology of African herbal remedies.

Toxicity related to traditional medicines is becoming more widely recognized as these remedies become popular in developed countries. Accidental herbal toxicity occurs not only as a result of a lack of pharmaceutic quality control in harvesting and preparation but also because herbal remedies are believed to be harmless. Although there is a huge amount of data available documenting the pharmacologically active ingredients of many plants, it is seldom helpful to the toxicologist in an acute situation. Current analytic methods such as high-performance liquid chromatography, gas chromatography--mass spectrometry, and immunoassays can provide identification of the toxin in those few cases in which the history or symptoms give a clear lead, but broad screening methods remain to be developed. In most cases of plant poisoning, treatment continues to be only of symptoms, with few specific antidotes available. It is important that toxicologists in the West be alert to the possibility of encountering poisoning in patients due to traditional African remedies.

Africa↗
PubMed1998

Sources and magnitude of perceived psychological stress in high school volleyball officials.

Research has indicated that sporting officials experience perceived psychological stress from a variety of sources. The reported magnitude of that stress has been mixed depending on the sport. The present study examined the sources and magnitude of perceived psychological stress among 353 American high school volleyball officials in a midwestern state. Principal component analysis with varimax rotation identified four factors: fear of failure, time pressure, interpersonal conflict, and fear of physical harm. 57% of the officials reported "none" or "very little" stress associated with volleyball officiating. Recommendations for further research are discussed.

Adult↗
PubMed1998

Peer visitor support for family caregivers of seniors with stroke.

The objectives of this nationally funded intervention study were to: (1) implement a home visiting support program for family caregivers of seniors with a recent stroke using experienced peers; (2) monitor, describe, and evaluate the support intervention process; and (3) measure the impact of the peer support intervention on caregivers' perceptions of their social support, burden, stress, and competence and the use of health-care services by stroke survivors. This paper focuses on the first two objectives. Twenty family caregivers were visited initially by a health professional (nurse, occupational therapist) for assessment, and thereafter twice weekly for 12 weeks by a peer (experienced family caregiver). Transcripts of audiotaped post-intervention and delayed post-intervention (3 and 6 months) interviews with participants and the diaries/logs of professionals and peers were subjected to content analysis. Peer visitors offered emotional, informational, and affirmational support to family caregivers. Family caregivers reported that the intervention met their support needs, lessened some of their caregiving demands, and enhanced their confidence and ability to cope.

Aged↗
PubMed1997

Stress, coping, and social support as psychosocial factors in readmissions for ischaemic heart disease.

This exploratory investigation aimed to identify psychological and social factors associated with early (4 months postdischarge) readmission to hospital of persons with ischaemic heart disease (IHD). Data on stress (Stress Appraisal Scale), coping strategies (Ways of Coping Questionnaire), and social network/social support (Norbeck Social Support Questionnaire) were collected from 100 persons with the primary diagnosis of IHD prior to discharge from hospital. Twenty-four persons were readmitted during the 4-month study period. The sample was divided into two groups for analysis: (1) persons with a first admission for IHD, and (2) persons with a prior history of admission for IHD. In comparison to persons with multiple admissions for cardiac illness, first time admissions appraised their IHD as less central and threatening, perceived less affective and affirmational support from health professionals, and identified health professionals less and neighbours more as sources of support. Greater use of the coping strategy 'seeking social support' was associated with the readmission of persons who had had their first admission for IHD. Less use of the coping strategy 'accepting responsibility' was associated with the readmission of persons who had a history of prior admission for IHD.

Adaptation, Psychological↗
PubMed1997

A direct repeat (DR-1) element in the first exon modulates transcription of the preproenkephalin A gene.

The preproenkephalin A gene is regulated by upstream cis-acting elements which respond to various signals, such as cAMP, calcium, and phorbol esters. An additional regulatory element was detected downstream of the transcription start site of the human preproenkephalin A gene in transfection experiments. The element was localized by DNAse I footprinting and methylation interference assays to a direct repeat (DR-1) element in the first (untranslated) exon. Deletion or mutation of this site reduced transcriptional activity of promoter-reporter constructs by over 50%. Antibodies against COUP-TF beta/ARP-1 and RXR transcription factors altered the pattern seen on electrophoretic mobility shift assays using double-stranded oligonucleotide containing the exon 1 protein binding site. This suggests that the factors that bind this site and modulate transcription of the PPE gene include members of the COUP-TF and retinoid X receptor families.

Animals↗
PubMed1997

Screening for drugs of abuse (II): Cannabinoids, lysergic acid diethylamide, buprenorphine, methadone, barbiturates, benzodiazepines and other drugs.

Requirements for the provision of an efficient and reliable service for drugs of abuse screening in urine have been summarized in Part I of this review. The requirements included rapid turn-around times, good communications between requesting clinicians and the laboratory, and participation in quality assessment schemes. In addition, the need for checking/confirmation of positive results obtained for preliminary screening methods was stressed. This aspect of the service has assumed even greater importance with widespread use of dip-stick technology and the increasing number of reasons for which drug screening is performed. Many of these additional uses of drug screening have possible serious legal implications, for example, screening school pupils, professional footballers, parents involved in child custody cases, persons applying for renewal of a driving licence after disqualification for a drug-related offence, doctors seeking re-registration after removal for drug abuse, and checking for compliance with terms of probation orders; as well as pre-employment screening and work-place testing. In many cases these requests will be received from a general practitioner or drug clinic with no indication of the reason for which testing has been requested. This also raises the serious problems of a chain of custody, provision of two samples, stability of samples, and secure and lengthy storage of samples in the laboratory-samples may be requested by legal authorities several months after the initial testing. The need for confirmation of positive results is now widely accepted but it may be equally important to confirm unexpected negative results. Failure to detect the presence of maintenance drugs may lead to the patient being discharged from a drug treatment clinic and, if attendance at the clinic is one of the terms of continued employment, to dismissal. It seems likely that increasing abuse of drugs and the efforts of regulatory authorities to control this, will lead to the manufacture of more designer drugs. Production of substituted phenethylamines was facilitated by the drug makers' cook book, 'PIHKAL' (Phenethylamines I Have Known And Loved) by Dr Alexander Shulgin and Ann Shulgin, and production of substituted tryptamines is promised in their next book, TIHKAL. Looking to the future, laboratories will need to ensure that they can detect and quantitate an ever-increasing number of drugs and related substances. The question of confidence in results of drugs of abuse testing raised in 1993 by Watson has assumed even greater importance as a result of attention focused on the OJ Simpson trial in Los Angeles. Toxicological investigations are likely to be challenged more frequently in the future. Even if analyses have been performed by GC-MS, there is a need to establish the level of match between the spectrum of the unknown substance and a library spectrum which is considered acceptable for legal purposes. It will also be essential to ensure that computer libraries contain spectra for all substances likely to be encountered in drugs of abuse screening.

Barbiturates↗
PubMed1997

Insights from a nursing research program on social support.

This paper highlights the conceptual and practical implications of a nursing research program that focuses on social support. The diverse dimensions of the construct of social support; its relationship to stress and coping; and its impact on health, health behaviour, and use of health services are explicated in the conceptual framework underpinning the program. These associations will be elucidated by citing examples from eight assessment studies and four intervention studies. The research program yielded new insights and reinforced reported findings of other social-support research.

Adaptation, Psychological↗
PubMed1996

The Drosophila p70s6k homolog exhibits conserved regulatory elements and rapamycin sensitivity.

The protein p70s6k/p85s6k lies on a mitogen-stimulated signaling pathway and plays a key role in G1 progression of the cell cycle. Activation of this enzyme is mediated by a complex set of phosphorylation events, which has largely contributed to the difficulty in identifying the upstream kinases that mediate p70s6k activation. Genetics has proved a powerful complementary approach for such problems, providing an alternative means to identify components of signaling cascades and their functional end targets. As a first step toward implementing such an approach, we have cloned cDNAs encoding the Drosophila melanogaster p70s6k homolog (Dp70s6k). Dp70s6k is encoded by a single gene, which generates three mRNA transcripts and exhibits an overall identity of 78% in the catalytic domain with its mammalian counterpart. Importantly, this high identity extends beyond the catalytic domain to the N terminus, linker region, and the autoinhibitory domain. Furthermore, all the critical phosphorylation sites required for mammalian p70s6k activation are conserved within these same domains of Dp70s6k. Chief amongst these conserved sites are those associated with the selective rapamycin-induced p70s6k dephosphorylation and inactivation. Consistent with this observation, analysis of total S6 kinase activity in fractionated Drosophila Schneider line 2 cell extracts reveals two peaks of activity, only one of which is rapamycin sensitive. By employing a monospecific polyclonal antibody generated against Dp70s6k, we show that the cloned DP70s6k cDNA has identity with only the rapamycin sensitive peak, suggesting that this biological system would be useful in determining not only the mechanism of p70s6k activation, but also in elucidating the mechanism by which rapamycin acts to inhibit cell growth.

Amino Acid Sequence↗
PubMed1996

The role of nuclear factor NF-Y/CP1 in the transcriptional regulation of the human aldehyde dehydrogenase 2-encoding gene.

Mitochondrial aldehyde dehydrogenase (ALDH2) activity is produced at low levels in many tissues, with highest production in liver. Transfection assays using the first 600 bp of upstream DNA provided evidence for both positive and negative regulatory elements in the proximal promoter. A region from -79 to -116 bp was protected in DNase I footprinting assays and bound in electrophoretic mobility shift assays (EMSA) by a nuclear factor found in all cell lines and tissues tested. This region, denoted FP160, contained the consensus recognition sites for Sp1 and AP2, and a CCAAT box. The CCAAT box was specifically protected by a nuclear factor in methylation interference assays. Mutagenesis of specific bp within the CCAAT box eliminated protein binding in vitro and decreased transcriptional activity from the ALDH2 promoter approximately 50% in reporter gene assays. Competition experiments showed that the nuclear factor binding to the FP160 oligodeoxyribonucleotide (oligo) was competed by oligos corresponding to an NY-Y/CP1-binding site to a greater extent than by those containing sites for CTF/NF1, C/EPB or CP2. The heat stability, resistance to proteinase K digestion, sensitivity to inhibition of DNA binding by o-phenanthroline, and immunological properties of the liver factor binding to FP160 were very similar to the corresponding properties of NF-Y/CP1. Thus, the proximal ALDH2 promoter was bound by NF-Y/CP1 and this transcription factor may be responsible for the basal expression of the gene observed in most tissues. The NFY-CP1 present in rat liver has similar properties to that previously characterized in M12 B-lymphoma cells and LMTK mouse fibroblasts.

Aldehyde Dehydrogenase↗
PubMed1996

Dexamethasone represses phorbol ester-, forskolin-, and calcium-stimulated expression of a preproenkephalin A promoter-chloramphenicol acetyltransferase gene via a receptor-mediated mechanism.

CV-1 cells were stably transfected with a preproenkephalin A (PPE) promoter-chloramphenicol acetyltransferase (CAT) reporter plasmid containing -176 to +171 bp of the human PPE gene. Low levels of CAT were expressed constitutively. The reporter enzyme activity was induced by treatment of the cells for 6 h with drugs that increased intracellular cAMP (forskolin and 8-bromo-cAMP), intracellular calcium (A23187), or protein kinase C activity (tetradecanoyl phorbol-4-acetate, TPA) in the presence of the phosphodiesterase inhibitor isobutylmethylxanthine. Co-administration of dexamethasone reduced the magnitude of phorbol ester-stimulated CAT activity by about 50%, while there were smaller but not significant effects on forskolin- or A23187-stimulated expression of this reporter construct. In transient transfections which included the PPE-CAT reporter gene and a glucocorticoid receptor expression plasmid, dexamethasone significantly reduced stimulated expression of the reporter by TPA, forskolin, and A23187. The effect was observed with 10(-8)-10(-6) M dexamethasone and was blocked by the presence of the glucocorticoid antagonist RU486, suggesting that the effect of dexamethasone was mediated by the glucocorticoid receptor. The promoter region contained in this construct lacks a classical glucocorticoid response element or known negative elements; thus, dexamethasone may reduce stimulated expression of the PPE promoter via indirect effects.

Calcimycin↗
PubMed1996

The effects of four neuropeptides on the degranulation of mucosal mast cells from sheep.

Isolated mucosal mast cells (MMC) were used to examine the ability of four neuropeptides, substance P, vasoactive intestinal peptide, beta-endorphin and somatostatin, to release mediators in the presence or absence of parasite antigen. None of the neuropeptides induced the release of sheep mast cell protease (SMCP) or histamine from MMC of helminth-immune sheep in the absence of parasite antigen. Incubation of immune MMC with 100 and 1.0 microgram/mL parasite antigen induced 32.1 and 15.5% specific SMCP release, respectively. While the neuropeptides did not augment SMCP release at 100 micrograms/mL parasite antigen, significant enhancement (40-98%) of SMCP release at 1 microgram/mL antigen was obtained by each neuropeptide at concentrations from 10(-8) to 10(-12) mol/L. The results provide additional support for modulation of MMC degranulation by neural activity in sheep and, to our knowledge, this is the first demonstration that the threshold antigen concentration for allergic responses may also be lowered by neuropeptides to render the reaction more sensitive to antigen.

Animals↗