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Biomedical subjects

Stephen Brown

Publications and source records attributed to Stephen Brown.

At least 19 recordsLinked to original sources
PubMed2006

Relationships between community characteristics and municipal smoke-free bylaw status and strength.

BACKGROUND: Municipal smoke-free spaces bylaws are a common population-level intervention to address the prominent health risks associated with exposure to second-hand smoke. In Canada, bylaw prevalence is increasing, but inequities in level of protection across communities remain as bylaws vary from place to place. Little is known about the role of place in this policy disparity. To address this gap, this study examined associations between community characteristics and municipal smoke-free spaces policy outcomes to elucidate how ecological conditions are associated with bylaw status and strength. METHOD: Smoke-free public place and workplace bylaws were obtained from all municipalities with a population of >or=5000 in the provinces of Alberta (N=78) and Ontario (N=245), Canada. Bylaws were assigned a strength score (ranging 0-100) rating the degree of bylaw comprehensiveness, restrictiveness and enforcement provisions. These data were then linked to socio-demographic data from the Canadian Census (1996) and the Canadian Community Health Survey Cycle 1.1 (2000/2001). Logistic and multiple linear regression analyses were used to develop models for municipal bylaw status and strength using community factors including: socio-demographics, municipality type, health region smoking rates, and provincial tobacco control environment. CONCLUSIONS: Study findings suggest that community characteristics play a key role in the status and strength of municipal smoke-free bylaws. As smoking bans continue to emerge world-wide under the Framework Convention on Tobacco Control, knowledge about conditions that promote policy success will be critical for those in need of immediate information to maximize policy-making in their own settings. Use of community profiles that consider socio-demographics along with broader contextual factors can aid decision-makers, public health advocates, and researchers in identifying similar jurisdictions with a successful smoke-free spaces policy and communicating with them about their policy-making experiences. Knowledge about the conditions associated with municipal policy-development may be translated to other jurisdictions where information is sparse, or evidence is newly emerging.

Alberta↗
PubMed2006

JAK/STAT signalling in Drosophila controls cell motility during germ cell migration.

The gonad is formed from two populations of cells originating at different locations: the primordial germ cells (PGCs), giving rise to either sperm or oocytes, and the somatic gonadal mesoderm precursors (SGPs), which support development of the gametes. Following the PGCs' migration during gastrulation, these two populations meet, forming the immature gonad. We present evidence that during embryonic development, the PGCs require the canonical JAK/STAT signalling cascade to migrate efficiently towards the SGPs. Loss of function for any element of the JAK/STAT pathway causes frequent germ cell mislocalisation. We have found that wild-type germ cells produce filopodia while they migrate through the mesoderm towards the gonad. Our observations suggest that PGCs use filopodia to migrate and to keep contact with each other. Interestingly, activation of the JAK/STAT pathway is required for these filopodia to form, and ectopic JAK/STAT activation enhances their formation.

Animals↗
PubMed2006

Validation of QF-PCR for prenatal aneuploidy screening in the United States.

OBJECTIVE: QF-PCR is an inexpensive and reliable method for aneuploidy screening; however, despite its obvious advantages, it is not in routine use in the United States. Our objective in the present study was to validate QF-PCR as a means for prenatal aneuploidy screening in our institution. METHODS: A QF-PCR assay using 15 primer pairs located on chromosomes 13, 18, 21 X and Y was established for aneuploidy screening. Amniotic fluid (AF) and chorionic villus sampling (CVS) samples consisting only of the cells recovered from the plasticware discarded by our institutional cytogenetics laboratory were collected and DNA was prepared by a simple and inexpensive microwave procedure. QF-PCR was then performed and interpreted using established criteria. RESULTS: 687 consecutive prenatal samples were screened in a blinded prospective manner, and results were compared to those obtained by conventional cytogenetics. 100% of autosomal trisomies were detected, and there were zero false positives. A single case each of XXY and 45X were missed. CONCLUSIONS: QF-PCR for prenatal aneuploidy screening was validated in our laboratory and has now been approved by the New York State Clinical Laboratory Evaluation Program. We propose a simple protocol for integrating QF-PCR into the normal cytogenetics laboratory workflow.

Amniotic Fluid↗
PubMed2006

Design and characterization of a metalloproteinase inhibitor-tethered resin for the detection of active MMPs in biological samples.

Matrix metalloproteinases (MMPs), zinc-dependent endopeptidases, are implicated in tumor progression. We describe herein the development of a resin-immobilized, broad-spectrum synthetic MMP inhibitor for selective binding of the active forms of MMPs from different experimental samples. We confirmed the activity-based binding of MMPs to the inhibitor-tethered resin with purified human recombinant MMP-2, -9, and -14, samples of cultured cells, and tissue extracts. Our results show that only the free active MMPs, and not the zymogens or MMP/TIMP (enzyme-protein inhibitor) complexes, bound specifically to the resin. In our comparison of benign and carcinoma tissue extracts, we detected active MMP-2 and MMP-14 forms only in the cancerous tissue samples, indicating that a pool of the tumor MMPs is free of endogenous inhibitors (TIMPs), and is thus likely to contribute to proteolytic events that precipitate tumor metastasis.

Breast Neoplasms↗
PubMed2006

X-chromosome inactivation and ovarian age during the reproductive years.

OBJECTIVE: To explore whether skewed X-chromosome inactivation (XCI) is related to indicators of ovarian age. DESIGN: The XCI skewing percent and indicators of ovarian age were measured in women with recent pregnancy losses and women with recent livebirths. All analyses adjust for chronologic age and pregnancy outcome. SETTING: Hospital in eastern central New York. PATIENT(S): One hundred thirty-six women with informative XCI assays: 83 with index pregnancy losses and 53 with livebirths. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): The primary indicators of ovarian age were antral follicle count, levels of FSH and inhibin B. A secondary indicator was level of estradiol (E2). RESULT(S): The XCI skewing percent, defined either continuously or categorically (> or =90%), was unrelated to the indicators of ovarian age. The sample was large enough to rule out as unlikely a modest decline in antral follicle count or a modest increase in FSH in relation to skewed XCI. CONCLUSION(S): X-chromosome anomalies are associated with skewed XCI and with premature ovarian failure. Our data raise the possibility that X-chromosome anomalies may not be an important influence on ovarian aging in menstruating women.

Adolescent↗
PubMed2006

Lack of decay of HIV-1 in gut-associated lymphoid tissue reservoirs in maximally suppressed individuals.

Although peripheral blood mononuclear cells (PBMCs) and lymph nodes represent a principal reservoir, the contribution of gut-associated lymphoid tissue (GALT) has not been evaluated. In 15 HIV-1-infected subjects with maximal suppression of HIV replication by highly active antiretroviral therapy, we quantified HIV-1 DNA and RNA in mucosal biopsy specimens, PBMCs, and plasma with ultrasensitive assays. We also calculated compartmental burdens of HIV-1 DNA-positive cells and characterized the temporal decay of these reservoirs in a period of 1 year (with projections to >50 years). HIV-1 RNA was detected in 20% of the subjects' mucosal biopsy specimens and in 80% of the PBMC samples. Mucosal HIV-1 DNA was detected in 80% of the subjects and in 100% of the PBMC samples. Calculated numbers of lymphoid cells containing "potentially replication-competent" HIV-1 DNA showed that the PBMC compartment contained approximately 70,000 such cells, and GALT contained approximately 160,000 cells. Rates of decay slopes for all 15 subjects in both compartments were not statistically significantly different when compared with each other or with zero slope. Our data indicate that GALT is a quantitatively important reservoir of potentially replicative cells containing HIV-1 DNA, harboring at least as many or more of such cells as the PBMC compartment. In well-suppressed patients on highly active antiretroviral therapy, the GALT compartment showed no clear pattern of HIV-1 decay, similar to that in the PBMCs.

DNA, Viral↗
PubMed2006

Deterioration.

Intellectual deterioration in epilepsy may be real or apparent. The latter refers to delay in cognitive development such that performance against age-related norms appears to drop. The former, real deterioration can occur due to concomitant degenerative neurological disease of which epilepsy is also a symptom, or it may happen as a consequence of one or more of a number of other factors. These include (1) direct effects of seizures and abnormal electroencephalogram activity on brain function, (2) traumatic brain injury secondary to seizures, including status epilepticus, (3) the influence of antiepileptic therapy, both drugs and surgery, on cognitive function, (4) psychosocial sequelae of diagnosis. Some epilepsy syndromes include intellectual deterioration as a frequent feature, with various causes. Developmental factors may also play a part. Cognitive functioning may be impaired by the presence of an epileptogenic lesion, and also in different ways and at different times by other brain areas involved with partial seizures, including irritative and functional deficit zones. Abnormal activity in these areas at critical periods in development may interact and disrupt pathways necessary for maturation of frontal lobe and limbic system functioning, leading to long-term neurological deficits. Increased understanding of the mechanisms by which this may happen raises intriguing possibilities for prevention and remediation.

Adult↗
PubMed2005

Intravenous amiodarone for incessant tachyarrhythmias in children: a randomized, double-blind, antiarrhythmic drug trial.

BACKGROUND: Intravenous (IV) amiodarone has proven efficacy in adults. However, its use in children is based on limited retrospective data. METHODS AND RESULTS: A double-blind, randomized, multicenter, dose-response study of the safety and efficacy of IV amiodarone was conducted in 61 children (30 days to 14.9 years; median, 1.6 years). Children with incessant tachyarrhythmias (supraventricular arrhythmias [n=26], junctional ectopic tachycardia [JET, n=31], or ventricular arrhythmias [n=4]) were randomized to 1 of 3 dosing regimens (low, medium, or high: load plus 47-hour maintenance) with up to 5 open-label rescue doses. The primary efficacy end point was time to success. Of 229 patients screened, 61 were enrolled during 13 months by 27 of 48 centers in 7 countries. Median time to success was significantly related to dose (28.2, 2.6, and 2.1 hours for the low-, medium-, and high-dose groups, respectively; P=0.028). There was no significant association with dose for any arrhythmia subgroup, including JET, but the subgroups were too small for an accurate assessment. Adverse events (AEs) were common (87%), leading to withdrawal of 10 patients. There were 5 deaths in the 30-day follow-up period (2 possibly related to the study drug). Dose-related AEs included hypotension (36%), vomiting (20%), bradycardia (20%), atrioventricular block (15%) and nausea (10%). CONCLUSIONS: In children, the overall efficacy of IV amiodarone, as measured by time to success, was dose related but not significantly for any arrhythmia subgroup. AEs were common and appeared to be dose related. Although efficacious for critically ill patients, the dose-related risks of IV amiodarone should be taken into account when treating children with incessant arrhythmias. Prospective, placebo-controlled trials would be helpful in assessing antiarrhythmic drug efficacy in children, because their results may differ from retrospective series and adult studies.

Adolescent↗
PubMed2005

Performance evaluation of a thermal Doppler Michelson interferometer system.

The thermal Doppler Michelson interferometer is the primary element of a proposed limb-viewing satellite instrument called SWIFT (Stratospheric Wind Interferometer for Transport studies). SWIFT is intended to measure stratospheric wind velocities in the altitude range of 15-45 km. SWIFT also uses narrowband tandem etalon filters made of germanium to select a line out of the thermal spectrum. The instrument uses the same technique of phase-stepping interferometry employed by the Wind Imaging Interferometer onboard the Upper Atmosphere Research Satellite. A thermal emission line of ozone near 9 microm is used to detect the Doppler shift due to winds. A test bed was set up for this instrument that included the Michelson interferometer and the etalon filters. For the test bed work, we investigate the behavior of individual components and their combination and report the results.

Journal Article↗
PubMed2005

Characterisation of Upd2, a Drosophila JAK/STAT pathway ligand.

The characterisation of ligands that activate the JAK/STAT pathway has the potential to throw light onto a comparatively poorly understood aspect of this important signal transduction cascade. Here, we describe our analysis of the only invertebrate JAK/STAT pathway ligands identified to date, the Drosophila unpaired-like family. We show that upd2 is expressed in a pattern essentially identical to that of upd and demonstrate that the proteins encoded by this region activate JAK/STAT pathway signalling. Mutational analysis demonstrates a mutual semi-redundancy that can be visualised in multiple tissues known to require JAK/STAT signalling. In order to better characterise the in vivo function of these ligands, we developed a reporter based on a natural JAK/STAT pathway responsive enhancer and show that ectopic upd2 expression can effectively activate the JAK/STAT pathway. While both Upd and Upd2 are secreted JAK/STAT pathway agonists, tissue culture assays show that the signal-sequences of Upd and Upd2 confer distinct properties, with Upd associated primarily with the extracellular matrix and Upd2 secreted into the media. The differing biophysical characteristics identified for Upd-like molecules have implications for their function in vivo and adds another aspect to our understanding of cytokine signalling in Drosophila.

Amino Acid Sequence↗
PubMed2005

Design, synthesis, and evaluation of a mechanism-based inhibitor for gelatinase A.

[structure: see text] Matrix metalloproteinases (MMPs), of which 26 are known, have been implicated in a number of pathological conditions, including tumor metastasis. We have previously described the first mechanism-based inhibitor for MMPs (J. Am. Chem. Soc. 2000, 122, 6799-6800), which in chemistry mediated by the active site zinc ion selectively and covalently inhibits MMP-2, -3, and -9. Computational analyses indicated that this selectivity in inhibition of MMPs could be improved by design of new variants of the inhibitor class. We report herein the syntheses of methyl 2-(4-{4-[(2-thiiranylpropyl)sulfonyl]phenoxy}phenyl)acetate (3) and 2-(4-{4-[(2-thiiranylpropyl)sulfonyl]phenoxy}phenyl)acetic acid (4), and show that compound 3 serves as a mechanism-based inhibitor exclusively for MMP-2. This molecule should prove useful in delineating the functions of MMP-2 in biological systems.

Binding Sites↗
PubMed2005

A highly specific inhibitor of matrix metalloproteinase-9 rescues laminin from proteolysis and neurons from apoptosis in transient focal cerebral ischemia.

Neuronal cell death occurs during many neurodegenerative disorders and stroke. The aberrant, excessive activity of matrix metalloproteinases (MMPs), especially MMP-9, contributes directly to neuron apoptosis and brain damage (Rosenberg et al., 1996; Asahi et al., 2001; Gu et al., 2002; Horstmann et al., 2003). We determined that MMP-9 degrades the extracellular matrix protein laminin and that this degradation induces neuronal apoptosis in a transient focal cerebral ischemia model in mice. We also determined that the highly specific thiirane gelatinase inhibitor SB-3CT blocks MMP-9 activity, including MMP-9-mediated laminin cleavage, thus rescuing neurons from apoptosis. We conclude that MMP-9 is a highly promising drug target and that SB-3CT derivatives have significant therapeutic potential in stroke patients.

Animals↗
PubMed2005

crossveinless-c is a RhoGAP required for actin reorganisation during morphogenesis.

Members of the Rho family of small GTPases are required for many of the morphogenetic processes required to shape the animal body. The activity of this family is regulated in part by a class of proteins known as RhoGTPase Activating Proteins (RhoGAPs) that catalyse the conversion of RhoGTPases to their inactive state. In our search for genes that regulate Drosophila morphogenesis, we have isolated several lethal alleles of crossveinless-c (cv-c). Molecular characterisation reveals that cv-c encodes the RhoGAP protein RhoGAP88C. During embryonic development, cv-c is expressed in tissues undergoing morphogenetic movements; phenotypic analysis of the mutants reveals defects in the morphogenesis of these tissues. Genetic interactions between cv-c and RhoGTPase mutants indicate that Rho1, Rac1 and Rac2 are substrates for Cv-c, and suggest that the substrate specificity might be regulated in a tissue-dependent manner. In the absence of cv-c activity, tubulogenesis in the renal or Malpighian tubules fails and they collapse into a cyst-like sack. Further analysis of the role of cv-c in the Malpighian tubules demonstrates that its activity is required to regulate the reorganisation of the actin cytoskeleton during the process of convergent extension. In addition, overexpression of cv-c in the developing tubules gives rise to actin-associated membrane extensions. Thus, Cv-c function is required in tissues actively undergoing morphogenesis, and we propose that its role is to regulate RhoGTPase activity to promote the coordinated organisation of the actin cytoskeleton, possibly by stabilising plasma membrane/actin cytoskeleton interactions.

Actins↗
PubMed2005

Cleavage at the stem region releases an active ectodomain of the membrane type 1 matrix metalloproteinase.

MT1-MMP (membrane type 1 matrix metalloproteinase) is a membrane-anchored MMP that can be shed to the extracellular milieu. In the present study we report the primary structure and activity of the major soluble form of MT1-MMP. MS analysis of the purified 50-kDa soluble MT1-MMP form shows that the enzyme extends from Tyr112 to Val524, indicating that formation of this species requires a proteolytic cleavage within the stem region. In agreement, deletion of the entire stem region of MT1-MMP inhibited shedding of the 50-kDa species. A recombinant 50-kDa species (Tyr112-Val524) expressed in cells exhibited enzymatic activity against pro-MMP-2 and galectin-3, and thus this species is a competent protease. The recombinant 50-kDa soluble form also decreased the level of surface-associated TIMP-2 (tissue inhibitor of metalloproteinase 2) when administered to cells expressing wild-type membrane-anchored MT1-MMP, suggesting that ectodomain shedding of MT1-MMP can alter the MMP/TIMP balance on the cell surface. A approximately 53-kDa species of MT1-MMP was also isolated from a non-detergent extract of human breast carcinoma tissue and was found to lack the cytosolic tail, as determined with specific MT1-MMP domain antibodies. Together, these data show that MT1-MMP ectodomain shedding is a physiological process that may broaden MT1-MMP activity to the pericellular space.

Amino Acid Motifs↗
PubMed2004

In vitro analysis of partial loss-of-function ZIC2 mutations in holoprosencephaly: alanine tract expansion modulates DNA binding and transactivation.

Heterozygous loss-of-function mutations in ZIC2 result in the severe brain malformation known as holoprosencephaly (HPE), indicating that forebrain development is exquisitely sensitive to the activity of this poorly understood transcription factor. To identify the regions of ZIC2 that are essential for activity, we have assessed the ability of a variety of ZIC2 mutant proteins to function in in vitro assays. Two sources of information were used to design relevant mutations. First, phenotype producing mutations in human and in mouse ZIC2 were mimicked and secondly, a comparative sequence analysis of the C-terminal was carried out. Analysis of these mutations suggests that either a decrease or an increase in ZIC2 mediated transcriptional activity can produce a forebrain phenotype. In addition, the analysis reveals that the C-terminal of ZIC2 contains both activation and repression domains. This region of ZIC2 contains an alanine-tract, and expansion of this domain is associated with HPE. In vitro analysis of proteins with alterations in alanine-tract length illustrates that the C-terminal alanine-tract of ZIC2 influences the strength of DNA binding and alters transcriptional activity in a promoter-specific manner. This finding provides a possible mechanism by which alanine-tract expansion mutations could alter the function of other transcription factors.

Alanine↗
PubMed2004

Spectral airglow temperature imager (SATI): a ground-based instrument for the monitoring of mesosphere temperature.

The spectral airglow temperature imager is a two-channel, Fabry-Perot spectrometer with an annular field of view and a cooled CCD detector. The detected fringe pattern contains spectral information in the radial direction and azimuthal spatial information from the annular field of view. The instrument measures the rotational temperature from the O2 atmospheric (0,1) nightglow emission layer at 94 km and from the Q branch of the OH Meinel (6,2) band emission layer at 87 km. The method for temperature derivation is based on the temperature dependence of the line-emission rates. This dependence allows a determination of the temperature by a least-squares fit of the measured spectrum to a set of synthetic spectra, an approach that minimizes the effect of noise from the sky background and the detector. The spectral airglow temperature imager was developed to meet a need for monitoring the role of the mesosphere in climate variability through long-term observation of the mean temperature and the gravity waves from a single station, as well as large-scale wave perturbations through the use of multiple stations.

Journal Article↗
PubMed2004

Safety, pharmacokinetics, and antiviral activity of AMD3100, a selective CXCR4 receptor inhibitor, in HIV-1 infection.

AMD3100 is a CXCR4 receptor inhibitor with anti-HIV-1 activity in vitro. We tested the safety, pharmacokinetics, and antiviral effect of AMD3100 administered for 10 days by continuous intravenous infusion in an open-label dose escalation study from 2.5 to 160 microg/kg/h. Forty HIV-infected patients with an HIV RNA level >5000 copies/mL on stable antiretroviral (ARV) regimens or off therapy were enrolled. Syncytium-inducing (SI) phenotype in an MT-2 cell assay was required in higher dose cohorts. Most subjects were black (55%), male (98%), and off ARV therapy. HIV phenotype was SI (30%), non-SI (45%), or not tested (25%). One patient (5 microg/kg/h) had serious and possibly drug-related thrombocytopenia. Two patients (40 and 160 microg/kg/h) had unexpected, although not serious, premature ventricular contractions. Most patients in the 80- and 160-microg/kg/h cohorts had paresthesias. Steady-state blood concentration and area under the concentration-time curve were dose proportional across all dose levels; the median terminal elimination half-life was 8.6 hours (range: 8.1-11.1 hours). Leukocytosis was observed in all patients, with an estimated maximum effect of 3.4 times baseline (95% confidence interval: 2.9-3.9). Only 1 patient, the patient whose virus was confirmed to use purely CXCR4 and who also received the highest dose (160 microg/kg/h), had a significant 0.9-log10 copies/mL HIV RNA drop at day 11. Overall, however, the average change in viral load across all patients was +0.03 log10 HIV RNA. Given these results, AMD3100 is not being further developed for ARV therapy, but development continues for stem cell mobilization.

Anti-HIV Agents↗