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Biomedical subjects

M Stewart

Publications and source records attributed to M Stewart.

At least 37 records · Page 2Linked to original sources
PubMed2002

The prognostic influence of bcl-2 in malignant glioma.

The bcl-2 gene is one of a complex group of genes which control programmed cell death. Bcl-2 acts to extend cell survival by blocking apoptosis, and thereby may influence tumour prognosis. This study of 187 high grade gliomas reviews clinicopathological prognostic features and the relationship to bcl-2 expression. Bcl-2 immunostaining was assessed in 159 specimens from these patients, by scoring systems of 0 to 3 for intensity of scoring and proportion of cells staining. Age, histology, pre- and post-operative performance status were found to be strongly predictive of survival (log rank test P<0.0001). The type of surgery performed did not influence survival in this group of patients. The expression of bcl-2 had a significant relationship with survival (univariate Cox model P=0.0302, hazard ratio 0.8, 95% confidence interval 0.65-0.98), with increased staining associated with improved survival. Multivariate analysis showed performance status, histology and proportion of cells staining for bcl-2 to be independently predictive of survival. Bcl-2 staining was not related to histological grade of tumours.

Adolescent↗
PubMed2002

Adapting portfolio theory for the evaluation of multiple investments in health with a multiplicative extension for treatment synergies.

Portfolio theory is central to the analysis of risk in many areas of economics but is seldom used appropriately in health economics. This contribution examines the use of portfolio theory in the context of cost-effectiveness analysis (CEA). A number of modifications are needed to apply portfolio analysis to the economic evaluation of health care interventions. First, the method of reporting the results of a CEA, and consequently some of the underlying assumptions, needs to be modified. Second, portfolio theory needs to be expressed in terms of effects on individuals aggregated to a population. Finally, one needs to allow for the possibility of synergy between the various health interventions. This paper derives a general formula for a portfolio of health care interventions that allows for synergies between interventions where the population effects are aggregated from individual effects. A number of special cases are also derived to highlight the nature of the formulation of the modified portfolio theory. We conclude that, while modified portfolio theory adds a theoretical foundation to health care evaluations, it may not be operational until estimates of the correlation between interventions are available, and the question of uncertainty is resolved in health care evaluation. Also, while a synergy may be present at the individual level, when aggregated over a large population it may not be significant given the standard assumption of constant returns to scale.

Journal Article↗
PubMed2002

Expression of angiogenic factors and hypoxia inducible factors HIF 1, HIF 2 and CA IX in non-Hodgkin's lymphoma.

AIMS: Angiogenesis in solid tumour pathology is well established but less is known about its role in haematological malignancies. Our study investigated the immunohistochemical expression of a variety of angiogenic and hypoxic factors and microvessel densities on 110 cases of high- and low-grade non-Hodgkin's lymphomas and reactive lymphoid tissues. methods and results: Expression of vascular endothelial growth factor (VEGF) was present in 82 (96%) of the non-Hodgkin's cases and 35 (100%) of the reactive lymphoid tissue cases. Both hypoxia inducible factors 1 alpha and 2 alpha (HIF 1 alpha, 2 alpha) were weakly expressed in the majority of high- and low-grade lymphomas. Carbonic anhydrase IX (CA IX), a HIF-inducible membrane-bound enzyme, expression was not abundant with membranous staining being present in seven (8%) of the lymphoma cases and none of the reactive cases. Thymidine phosphorylase (TP) was distributed amongst macrophages and follicular dendritic cells but was not present in the neoplastic population. The vasculature was stained using CD34 which gave rise to a distinct vascular, predominantly paracortical network present in low-grade lymphomas and reactive lymphoid tissue but which was lost in high-grade lymphomas. CONCLUSION: Our results suggest that non-Hodgkin's lymphomas may be less angiogenic and hypoxically driven than most solid tumours, which has implications for possible future therapies.

Angiogenesis Inducing Agents↗
PubMed2002

The effects of stock crate design and stocking density on environmental conditions for lambs on road transport vehicles.

AIM: The aim of this study was to evaluate the potential of variations in stock crate design (especially ventilation) and stocking density on road transport vehicles for reducing the risk of environmental stress for lambs during long-haul transport in hot weather. METHODS: In Experiment 1, lambs were transported on vehicles fitted with either a newer-design aluminium crate comprising a three-deck truck and four-deck trailer, or an older-design, more open, steel crate of a three-deck truck and three-deck trailer. In Experiment 2, lambs were transported on newer-design vehicles at either standard stocking density (0.20 m2 per 35 kg lamb) or at a 20% lower density (0.26 m2 per 35 kg lamb). In each experiment, each journey was replicated twice and consisted of travel periods and stationary periods designed to emulate conditions associated with an inter-island ferry crossing. Air ammonia concentrations and temperature and humidity were monitored within six pens on each vehicle, and the temperature-humidity index (THI) was calculated. RESULTS: Ammonia concentrations were variable and generally 50 ppm, and did not vary significantly with treatment. The THI increased when the vehicles were stationary, especially under conditions designed to emulate an enclosed ferry deck. The ambient temperature during Experiment 1 was moderate (up to 21 degrees C), and THI was slightly lower in the older-design crate. High ambient temperatures (up to 33 degrees C) were present during Experiment 2, and THI was significantly lower at the lower stock density. During a 3-h stationary period, the peak THI at standard stocking density was 91.0, compared with 84.9 for the low density treatment (p<0.001). CONCLUSIONS: For standard road transport vehicles used for long-haul transport of lambs, lowered loading density may be of considerable benefit in alleviating conditions that increase the risk of lamb deaths during inter-island transport on hot days.

Journal Article↗
PubMed2002

Observation of radiation-specific damage in human cells exposed to depleted uranium: dicentric frequency and neoplastic transformation as endpoints.

Depleted uranium (DU) is a dense heavy metal used primarily in military applications. Published data from our laboratory have demonstrated that DU exposure in vitro to immortalised human osteoblast cells (HOS) is both neoplastically transforming and genotoxic. DU possesses both a radiological (alpha-particle) and chemical (metal) component. Since DU has a low specific activity in comparison to natural uranium, it is not considered to be a significant radiological hazard. The potential contribution of radiation to DU-induced biological effects is unknown and the involvement of radiation in DU-induced biological effects could have significant implications for current risk estimates for internalised DU exposure. Two approaches were used to address this question. The frequency of dicentrics was measured in HOS cells following DU exposure in vitro. Data demonstrated that DU exposure (50 microM, 24 h) induced a significant elevation in dicentric frequency in vitro in contrast to incubation with the heavy metals, nickel and tungsten which did not increase dicentric frequency above background levels. Using the same concentration (50 microM) of three uranyl nitrate compounds that have different uranium isotopic concentrations and therefore, different specific activities, the effect on neoplastic transformation in vitro was examined. HOS cells were exposed to one of three-uranyl nitrate compounds (238U-uranyl nitrate, specific activity 0.33 microCi.g-1; DU-uranyl nitrate, specific activity 0.44 microCi.g-1; and 235U-uranyl nitrate, specific activity 2.2 microCi.g-1) delivered at a concentration of 50 microM for 24 h. Results showed, at equal uranium concentration, there was a specific activity dependent increase in neoplastic transformation frequency. Taken together these data suggest that radiation can play a role in DU-induced biological effects in vitro.

Cell Transformation, Neoplastic↗
PubMed2002

Can physical trauma cause breast cancer?

The objective of this study is to explore the effect of lifestyle on the risk of invasive breast carcinoma in women aged 50-65 years. A case-control study using a questionnaire and a semi-structured interview. Cases (n = 67) and controls (n = 134) were closely matched on known risk factors for breast cancer including age, family history, age at menarche, parity, age at first birth and menopausal status. Controls were chosen from a pool of 5600 women who attended for breast screening and filled in a questionnaire giving details to allow matching with cases. The study took place at the North Lancashire Breast Screening Service. Women were aged 50-65 years and presented with breast cancer or attended for breast screening. Women with breast carcinoma were more likely to report physical trauma to the breast in the previous 5 years than were the controls (odds ratio (OR) 3.3, 95% confidence interval (CI) 1.3-10.8, P < 0.0001). There were no significant differences in a wide range of other lifestyle indicators including factors relevant to social class, education, residence, smoking and alcohol consumption. In conclusion, recall bias is an unlikely explanation for these results in view of the nature and severity of physical trauma. Models of epithelial cell generation indicate that a causal link between physical trauma and cancer is plausible. A latent interval between cancer onset and presentation of under 5 years is also plausible. The most likely explanation of the findings is that physical trauma can cause breast cancer.

Aged↗
PubMed2002

Near-infrared diffuse optical tomography.

Diffuse optical tomography (DOT) is emerging as a viable new biomedical imaging modality. Using near-infrared (NIR) light, this technique probes absorption as well as scattering properties of biological tissues. First commercial instruments are now available that allow users to obtain cross-sectional and volumetric views of various body parts. Currently, the main applications are brain, breast, limb, joint, and fluorescence/bioluminescence imaging. Although the spatial resolution is limited when compared with other imaging modalities, such as magnetic resonance imaging (MRI) or X-ray computerized tomography (CT), DOT provides access to a variety of physiological parameters that otherwise are not accessible, including sub-second imaging of hemodynamics and other fast-changing processes. Furthermore, DOT can be realized in compact, portable instrumentation that allows for bedside monitoring at relatively low cost. In this paper, we present an overview of current state-of-the -art technology, including hardware and image-reconstruction algorithms, and focus on applications in brain and joint imaging. In addition, we present recent results of work on optical tomographic imaging in small animals.

Algorithms↗
PubMed2002

Suggestions in maternal and child health for the National Technology Assessment Programme: a consideration of consumer and professional priorities.

In North Staffordshire, the Achieving Sustainable Quality in Maternity (ASQUAM) meetings provide the programme for clinical guidelines and audit over the following year. The ASQUAM clinical effectiveness programme has attempted to address a number of the issues identified as obstacles to informed democratic prioritization. For example, it became clear that a number of topics raised were actually research questions. The organizers therefore decided to split the fourth ASQUAM day into an 'audit' morning and a 'research' afternoon. The meeting organized by RJ, CR and PJ in partnership with the Midwives Information and Resource Service and the National Childbirth Trust, was timed to allow the research ideas to feed into the national Health Technology Assessment (HTA) programme. This meeting was designed to increase the profile of ASQUAM amongst consumers and to increase their representation at the meeting. Objectives were to choose a new set of research priorities for the year 2000, and to ascertain the voting pattern of comparison to health professionals. There was overall agreement in terms of priorities, with the consumer group prioritizing 8 of the 10 topics chosen by the professionals (or 10 of the 11). No significant differences between the proportions of voted cast for each topic by professionals and consumers were found apart from topic 20. The numbers of consumers were small which does limit the number the validity of statistical comparisons. Nevertheless, it is clear that voting patterns were similar. Overall the process suggests that democratic prioritization is a viable option and one that may become essential within the framework of clinical and research governance.

Community Participation↗
PubMed2002

Susceptibility to varicella-zoster virus in applicants for nurse training in Scotland.

We investigated the immunity to varicella-zoster virus (VZV) of a cohort of applicants for nurse training and determined the relationship between immune status and history of chickenpox or shingles based on a self-completed questionnaire. Three hundred and fifty-six applicants for nurse training were enrolled at an occupational health department in NHS Scotland and 96% were immune to VZV. The positive predictive value of a history of VZV infection for seropositivity was 98% (286/292). The negative predictive value was 14% (9/64). History of chicken pox/shingles had a sensitivity of 84% (286/341) and specificity of 60% (9/15). Screening using past clinical history compatible with VZV infection would have missed 40% of those possibly susceptible to VZV on the basis of the ELISA IgG test. We conclude absence of past history of chickenpox or shingles is an unreliable identifier of susceptibility to VZV in healthcare workers. The Control of Substances Hazardous to Health (COSHH) Regulations 1999 require employers to make effective vaccines available for those employees who are not already immune to a biological agent to which they are exposed or liable to be exposed. Serological testing of healthcare workers would better identify those who are susceptible to VZV infection.

Adolescent↗
PubMed2001

Nuclear thymidylate synthase expression, p53 expression and 5FU response in colorectal carcinoma.

Thymidylate synthase (TS) is a key enzyme in DNA synthesis and is inhibited by metabolites of the chemotherapeutic agent 5-fluorouracil (5FU). Nuclear expression of TS in human tissue in vivo has not been characterised and its clinicopathological correlates in malignancy are unknown. 52 cases of primary colorectal carcinoma (CRC) and 24 cases of matched metastatic carcinoma were studied immunohistochemically using the monoclonal antibody TS106. The degree of nuclear TS immunostaining correlated closely with levels of TS mRNA expression amongst 10 CRCs studied. Strong nuclear immunostaining was seen in normal basal crypt colonocytes and germinal centre cells, and in a varying proportion of adenocarcinoma cells. Amongst the primary carcinomas, higher TS nuclear expression was associated with prominent extracellular mucin production and right-sided location. Higher TS nuclear expression also showed a significant association with poorer response to protracted venous infusional 5FU therapy. There was no clear association between TS nuclear expression and Ki67 or p53 expression assessed immunohistochemically. There was a strong positive correlation between TS nuclear expression in primary and metastatic CRC but the latter generally showed higher expression than matched primary tumour tissue. These findings confirm the nuclear expression of TS protein in human cells in vivo and provide new insight into how such expression may relate to the behaviour of CRCs.

Adenocarcinoma↗
PubMed2001

NTF2 monomer-dimer equilibrium.

Nuclear transport factor 2 (NTF2) mediates nuclear import of RanGDP, a central component of many nuclear trafficking pathways. NTF2 is a homodimer and each chain has independent binding sites for RanGDP and nuclear pore proteins (nucleoporins) that contain FxFG sequence repeats. We show here that the monomer-dimer dissociation constant for NTF2 obtained by sedimentation equilibrium ultracentrifugation is in the micromolar range, indicating that a substantial proportion of cellular NTF2 may be monomeric. To investigate the functional significance of NTF2 dimerization, we engineered a series of point mutations at the dimerization interface and one of these (M118E) remained monomeric below concentrations of 150 microM. CD spectra and X-ray crystallography showed that M118E-NTF2 preserved the wild-type NTF2 fold, although its thermal stability was 20 deg. C lower than that of the wild-type. M118E-NTF2 bound both RanGDP and FxFG nucleoporins less strongly, suggesting that dissociation of the NTF2 dimer could facilitate RanGDP release and thus nucleotide exchange after it had been transported into the nucleus. Moreover, colloidal gold coated with M118E-NTF2 showed reduced binding to Xenopus oocyte nuclear pores. Overall, our results indicate that dimer formation is important for NTF2 function and give insight into the formation of heterodimers by mRNA export factors such as TAP1 and NXT1 that contain NTF2-homology domains.

Amino Acid Substitution↗
PubMed2001

Synthesis and biological evaluation of s-triazine substituted polyamines as potential new anti-trypanosomal drugs.

The P2 transporter is a nucleoside transporter which is unique to the protozoan parasite Trypanosoma brucei, the causative organism of Human African Trypanosomasis. The transporter has been shown to bind some structural motifs not recognized by other transporters. In this paper we describe the use of the melamine motif, a substrate of the P2 transporter, as a potential tool to selectively deliver polyamine analogues to the parasites. The synthesis of a number of polyamine analogues attached to a variety of melamine analogues is described. Many of the compounds were shown to competitively inhibit uptake of adenosine, indicating that they are recognized by the transporter. Some of the compounds showed good in vitro activity against the parasites.

Adenosine↗
PubMed2001

Barriers to rotation in methyl formate by dynamic NMR spectroscopy and barriers to 1,3 oxygen-to-oxygen migration in methyl formate and trifluoromethyl formate by ab initio calculations.

Free-energy barriers of 9.85 and 11.91 +/- 0.15 kcal/mol at -70.8 degrees C were found by dynamic NMR spectroscopy for the E-to-Z and Z-to-E conversions, respectively, of methyl formate (1) enriched in 13C to 99% for the carbonyl carbon [methyl formate 13C (2)]. These barriers are higher than the literature values reported for -53 degrees C. The free-energy barrier to 1,3 oxygen-to-oxygen migration of the methyl group in methyl formate was determined by ab initio calculations at several levels. The value of 58.7 kcal/mol obtained at the MP2/6-311+G (df,pd) level was compared to a literature barrier for this process (MINDO/3) and to barriers for related compounds. A free-energy barrier of 63.0 kcal/mol for the oxygen - to - oxygen migration of the CF3 group in trifluoromethyl formate (3) was calculated at the MP2/6-31+G level.

Carbon Isotopes↗
PubMed2001

Interaction between Ran and Mog1 is required for efficient nuclear protein import.

Mog1 is a nuclear protein that interacts with Ran, the Ras family GTPase that confers directionality to nuclear import and export pathways. Deletion of MOG1 in Saccharomyces cerevisiae (Deltamog1) causes temperature-sensitive growth and defects in nuclear protein import. Mog1 has previously been shown to stimulate GTP release from Ran and we demonstrate here that addition of Mog1 to either Ran-GTP or Ran-GDP results in nucleotide release and formation of a stable complex between Mog1 and nucleotide-free Ran. Moreover, MOG1 shows synthetic lethality with PRP20, the Ran guanine nucleotide exchange factor (RanGEF) that also binds nucleotide-free Ran. To probe the functional role of the Mog1-Ran interaction, we engineered mutants of yeast Mog1 and Ran that specifically disrupt their interaction both in vitro and in vivo. These mutants indicate that the interaction interface involves conserved Mog1p residues Asp(62) and Glu(65), and residue Lys(136) in yeast Ran. Mutations at these residues decrease the ability of Mog1 to bind and release nucleotide from Ran. Furthermore, the E65K-Mog1 and K136E-Ran mutations in yeast cause temperature sensitivity and mislocalization of a nuclear import reporter protein, similar to the phenotype observed for the Deltamog1 strain. Our results indicate that a primary function of Mog1 requires binding to Ran and that the Mog1-Ran interaction is necessary for efficient nuclear protein import in vivo.

Crystallography, X-Ray↗
PubMed2001

Functional analysis of the hydrophobic patch on nuclear transport factor 2 involved in interactions with the nuclear pore in vivo.

Nuclear transport factor 2 (NTF2) is a small homodimeric protein that interacts simultaneously with both RanGDP and FxFG nucleoporins. The interaction between NTF2 and Ran is essential for the import of Ran into the nucleus. Here we use mutational analysis to dissect the in vivo role of the interaction between NTF2 and nucleoporins. We identify a series of surface residues that form a hydrophobic patch on NTF2, which when mutated disrupt the NTF2-nucleoporin interaction. Analysis of these mutants in vivo demonstrates that the strength of this interaction can be significantly reduced without affecting cell viability. However, cells cease to be viable if the interaction between NTF2 and nucleoporins is abolished completely, indicating that this interaction is essential for the function of NTF2 in vivo. In addition, we have isolated a dominant negative mutant of NTF2, N77Y, which has increased affinity for nucleoporins. Overexpression of the N77Y protein blocks nuclear protein import and concentrates Ran at the nuclear rim. These data support a mechanism in which NTF2 interacts transiently with FxFG nucleoporins to translocate through the pore and import RanGDP into the nucleus.

Active Transport, Cell Nucleus↗
PubMed2001

Intrinsic connectivity of the rat subiculum: I. Dendritic morphology and patterns of axonal arborization by pyramidal neurons.

The dendritic and axonal morphology of rat subicular neurons was studied in single cells labeled with Neurobiotin. Electrophysiological classification of cells as intrinsic burst firing or regular spiking neurons was correlated with morphologic patterns and cell locations. Every cell had dendritic branches that reached the outer molecular layer, with most cells having branches that reached the hippocampal fissure. All but two pyramidal cells had axon collaterals that entered the deep white matter (alveus). Branching patterns of apical dendrites varied as a function of the cell's soma location along the fissure-alveus axis of the cell layer. The first major dendritic branch point for most cells occurred at the superficial edge of the cell layer giving deep cells long primary apical dendrites and superficial cells short or absent primary apical dendrites. In contrast, basal dendritic arbors were similar across cells regardless of cell position. Apical and basal dendrites of all cells had numerous spines. Superficial and deep cells also differed in axonal collateralization. Deep cells (mostly intrinsically bursting [IB] class) had one or more ascending axon collaterals that typically remained within the region circumscribed by their apical dendrites. Superficial cells (mostly regular spiking [RS] class) tended to have axon collaterals that reached longer distances in the cell layer. Numerous varicosities and axonal extensions were present on axon collaterals in the cell layer and in the apical dendritic region, suggesting intrinsic connectivity. Axonal varicosities and extensions were found on axons that entered presubiculum, entorhinal cortex or CA1, supporting the notion that these were projection cells. Local collaterals were distinctly thinner than collaterals that would leave the subiculum, suggesting little or no myelin on local collaterals and some myelin on efferent fibers. We conclude that both IB and RS classes of subicular principal cells make synaptic contacts in and apical to the cell layer. Based on the patterns of axonal arborization, we suggest that subiculum has at least a crude columnar and laminar architecture, with ascending collaterals of deep cells forming columns and broader axonal arbors of superficial cells serving to distribute activity across multiple columns.

Animals↗
PubMed2001

Intrinsic connectivity of the rat subiculum: II. Properties of synchronous spontaneous activity and a demonstration of multiple generator regions.

Brain structures that can generate epileptiform activity possess excitatory interconnections among principal cells and a subset of these neurons that can be spontaneously active ("pacemaker" cells). We describe electrophysiological evidence for excitatory interactions among rat subicular neurons. Subiculum was isolated from presubiculum, CA1, and entorhinal cortex in ventral horizontal slices. Nominally zero magnesium perfusate, picrotoxin (100 microM), or NMDA (20 microM) was used to induce spontaneous firing in subicular neurons. Synchronous population activity and the spread of population events from one end of subiculum to the other in isolated subicular subslices indicate that subicular pyramidal neurons are coupled together by excitatory synapses. Both electrophysiological classes of subicular pyramidal cells (bursting and regular spiking) exhibited synchronous activity, indicating that both cell classes are targets of local excitatory inputs. Burst firing neurons were active in the absence of synchronous activity in field recordings, indicating that these cells may serve as pacemaker neurons for the generation of epileptiform activity in subiculum. Epileptiform events could originate at either proximal or distal segments of the subiculum from ventral horizontal slices. In some slices, events originated in both proximal and distal locations and propagated to the other location. Finally, propagation was supported over axonal paths through the cell layer and in the apical dendritic zone. We conclude that subicular burst firing and regular spiking neurons are coupled by means of glutamatergic synapses. These connections may serve to distribute activity driven by topographically organized inputs and to synchronize subicular cell activity.

Animals↗