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Biomedical subjects

B J Murray

Publications and source records attributed to B J Murray.

At least 19 recordsLinked to original sources
PubMed2006

Seizures during stroke thrombolysis heralding dramatic neurologic recovery.

Seizures during thrombolytic therapy for ischemic stroke have not previously been described as a favorable prognostic sign. We report three patients with severe stroke (NIH Stroke Scale [NIHSS] score 15 to 20) who experienced a seizure during tissue plasminogen activator (tPA) infusion. While initially raising alarm about possible hemorrhage, the seizures heralded dramatic recovery (an immediate 15-point NIHSS score improvement after tPA; NIHSS score 0 or 1 at 24 hours). We propose that the seizures during thrombolysis may indicate cortical reperfusion and/or hyperperfusion due to early recanalization of an acutely occluded intracranial artery.

Adult↗
PubMed2005

Reversible resistance modulation in mesoscopic silver wires induced by exposure to amine vapor.

Ensembles of silver nanowires (AgNEs) with diameters ranging from 200 nm to 1.0 microm have been prepared by electrochemical step edge decoration. These AgNEs showed a rapid (< 5 s), reversible increase in resistance upon exposure to the vapor of ammonia, trimethylamine, and pyridine. The amplitude of the resistance change was up to +3000% (DeltaR/Ro)-more than 2 orders of magnitude larger than can be explained based on boundary layer scattering effects. We experimentally probe the mechanism for this resistance modulation in the case of ammonia, and we propose a model to describe it. Conductive tip atomic force microscopy was used to probe individual sections of nanowires in AgNEs; these data revealed that the resistance change caused by NH(3) exposure was concentrated within a minority (approximately 10%) of the 5-microm wire segments that were probed--not uniformly distributed along each nanowire. All AgNEs showed a temperature dependence of their resistance, alpha, that was smaller than expected for silver metal. Highly sensitive AgNEs sometimes showed a negative alpha, characteristic of semiconductors, but negative alpha values were never observed for AgNEs with a low sensitivity to NH3. AgNEs did not respond to hydrocarbons, O2, H2O, N2, CO, or Ar, but a large (DeltaR/Ro > |-50%|) irreversible decrease in resistance was seen upon exposures to acids including HCl, HNO3, and H2SO4. Based on these and other data, we propose a model in which oxidized constrictions in silver nanowires limit the conductivity of the wire and provide a means for "gating" conduction based on the protonation state of the oxide surface.

Journal Article↗
PubMed2005

Molybdenum disulfide nanowires and nanoribbons by electrochemical/chemical synthesis.

Molybdenum disulfide nanowires and nanoribbons have been synthesized by a two-step, electrochemical/chemical synthetic method. In the first step, MoO(x) wires (a mixture of MoO(2) and MoO(3)) were electrodeposited size-selectively by electrochemical step-edge decoration on a highly oriented pyrolytic graphite (HOPG) surface. Then, MoO(x) precursor wires were converted to MoS(2) by exposure to H(2)S either at 500-700 degrees C, producing "low-temperature" or LT MoS(2) nanowires that were predominantly 2H phase, or above 800 degrees C producing "high-temperature" or HT MoS(2) ribbons that were predominantly 3R phase. The majority of these MoS(2) wires and ribbons were more than 50 microm in length and were organized into parallel arrays containing hundreds of wires or ribbons. MoS(2) nanostructures were characterized by X-ray photoelectron spectroscopy, scanning and transmission electron microscopy, selected area electron diffraction, X-ray diffraction, UV-visible absorption spectrometry, and Raman spectroscopy. HT and LT MoS(2) nanowires were structurally distinct: LT MoS(2) wires were hemicylindrical in shape and nearly identical in diameter to the MoO(x) precursor wires from which they were derived. LT MoS(2) wires were polycrystalline, and the internal structure consisted of many interwoven, multilayer strands of MoS(2); HT MoS(2) ribbons were 50-800 nm in width and 3-100 nm thick, composed of planar crystallites of 3R-MoS(2). These layers grew in van der Waals contact with the HOPG surface so that the c-axis of the 3R-MoS(2) unit cell was oriented perpendicular to the plane of the graphite surface. Arrays of MoS(2) wires and ribbons could be cleanly separated from the HOPG surface and transferred to glass for electrical and optical characterization. Optical absorption measurements of HT MoS(2) nanoribbons reveal a direct gap near 1.95 eV and two exciton peaks, A1 and B1, characteristic of 3R-MoS(2). These exciton peaks shifted to higher energy by up to 80 meV as the wire thickness was decreased to 7 nm (eleven MoS(2) layers). The energy shifts were proportional to 1/ L( parallel)(2), and the effective masses were calculated. Current versus voltage curves for both LT and HT MoS(2) nanostructures were probed as a function of temperature from -33 degrees C to 47 degrees C. Conduction was ohmic and mainly governed by the grain boundaries residing along the wires. The thermal activation barrier was found to be related to the degree of order of the crystallites and can be tuned from 126 meV for LT nanowires to 26 meV for HT nanoribbons.

Journal Article↗
PubMed2005

Shape- and size-selective electrochemical synthesis of dispersed silver(I) oxide colloids.

Silver(I) oxide (Ag2O) micro- and nanoparticles were electrochemically synthesized by anodizing a sacrificial silver wire in a basic aqueous sulfate solution. Ag2O particles were released from the silver electrode surface during synthesis producing a visible sol "stream". The composition of these particles was established using selected area electron diffraction, X-ray diffraction, and X-ray photoelectron spectroscopy. The shape of Ag2O crystallites could be adjusted using the potential of the silver wire generator electrode. The generation of a dispersed Ag2O sol and the observed shape selectivity are both explained by a two-step mechanism involving the anodic dissolution of silver metal, Ag0 --> Ag+(aq) + 1e-, followed by the precipitation of Ag2O particles, 2Ag+ + 2OH- --> Ag2O(s) + H2O. Within 100 mV of the voltage threshold for particle growth, cubic particles with a depression in each face ("hopper crystals") were produced. The application of more positive voltages resulted in the generation of 8-fold symmetric "flower"-shaped particles formed as a consequence of fast growth in the <111> crystallographic direction. The diameter of flower particles was adjustable from 250 nm to 1.8 microm using the growth duration at constant potential.

Journal Article↗
PubMed2001

Chromium treatment decreases the sensitivity of 5-HT2A receptors.

RATIONALE: Recent case series suggest that chromium picolinate in doses of 400 microg daily may have antidepressant properties, perhaps through increasing the peripheral availability of tryptophan for brain serotonin (5-HT) synthesis. OBJECTIVES: To determine the effects of chromium treatment on plasma tryptophan availability and on brain 5-HT function in human and animal models. METHODS: We studied the effects of short-term chromium supplementation on plasma concentrations of tryptophan and other large neutral amino acids. Brain 5-HT function was assessed by measuring the corticosterone/cortisol response to the 5-HT precursor, 5-hydroxytryptophan (5-HTP), a response believed to be mediated via indirect activation of 5-HT(2A) receptors. RESULTS: In rats, chromium increased peripheral and central tryptophan availability and elevated brain 5-HT content. Changes in peripheral tryptophan availability were not seen in humans but in both rats and humans, chromium lowered the cortisol response to challenge with 5-HTP. CONCLUSIONS: Chromium can modify brain 5-HT function in humans and animals, perhaps by altering the sensitivity of central 5-HT(2A) receptors.

Adult↗
PubMed2001

The effect of Li 1370, extract of Ginkgo biloba, on REM sleep in humans.

Ginkgo biloba extracts (GBE) have been shown to be as effective as anti-cholinesterase inhibitors in improving the cognitive test scores of patients with dementia. Although it has been assumed that GBE works via its antioxidant and vascular effects, some evidence has emerged that GBE may have some pro-cholinergic activity. We wished to test the hypothesis that a standardised preparation of GBE, Li 1370, increases cholinergic activity by measuring its effect on the sleep polysomnogram. In particular, latency to Rapid Eye Movement (REM) sleep is sensitive to cholinergic activity. For this purpose we recruited 10 healthy volunteers of both sexes and recorded sleep polysomnograms in a randomised cross-over study, comparing sleep polysomnograms taken the night after a single evening dose of Li 1370 (240 mg) with sleep polysomnograms taken after an evening dose of placebo. No significant differences in sleep parameters (including REM sleep measures) were detected; however sleep efficiency measures and subjective sleep quality reports showed that Li 1370 was well tolerated.

Adolescent↗
PubMed2001

Self-mutilation: review and case study.

This article reviews in a systematic way the literature on severe self-mutilation, emphasising possible aetiological factors and warning signs of impending self-mutilation. It provides practical advice on the prevention and management of such events, including legal issues of capacity and consent. An illustrative case history is provided of an artist who cut off his ear.

Humans↗
PubMed2000

An unusual case of trisomy and triploidy in a chorion villus biopsy.

A case is reported of a 35-year-old woman who underwent a chorion villus biopsy (CVB) at 17 weeks' gestation after intrauterine growth retardation and oligohydramnios were diagnosed by ultrasound scan. Chromosome analysis of the CVB direct preparations showed a 47,XX,+6 karyotype in all cells. The pregnancy was terminated and subsequent analysis of cultured cells from both the CVB and the post-mortem placenta showed three cell lines: 46,XX, 47,XX,+6 and 69,XXX, while fetal skin and muscle were entirely 69,XXX. An explanation is proposed for the origin and distribution of the three cell lines.

Adult↗
PubMed1993

Interaction of apolipoprotein AII with the putative high-density lipoprotein receptor.

There is strong evidence to indicate that binding of HDL by cells is due to recognition of apoproteins residing on the surface of the lipoprotein by the putative HDL receptor(s). Although both of the major HDL apoproteins, AI and AII, are recognized by the putative receptor, the nature of the binding interaction and the domains of the apoproteins involved are largely unknown. Previous data from this laboratory led to the proposal of a model to explain how HDL particles containing AII interacted with the HDL receptor in a different manner as compared to HDL particles which contain apoAI but not apoAII [Vadiveloo, P. K., & Fidge, N. H. (1992) Biochem. J. 284, 145-151]. The model predicted that each chain of the apoAII homodimer contained a binding domain capable of interacting with the HDL receptor. This model was tested in the current study by preparing apoAII monomers, complexing them with phospholipid, and determining the ability of these complexes to bind to putative HDL receptors in rat liver plasma membranes (RLPM) and bovine aortic endothelial cell membranes (BAECM) by ligand blotting. The data showed that these complexes were bound by HB1 and HB2 from RLPM, and to the 110-kDa HDL binding protein from BAECM, providing critical evidence to support the model. Further investigation into the binding interaction revealed that apoAII complexed with phospholipid (apoAII-PC) bound more than delipidated apoAII, which bound more than delipidated apoAII monomers. Thus, optimum binding required the presence of lipid.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

The effect of early labour, maternal analgesia and fetal acidosis on fetal plasma oxytocin concentrations.

OBJECTIVE: To determine the effect of early labour, maternal analgesia and fetal hypoxia on circulating fetal oxytocin concentrations. DESIGN: Prospective observational study. SETTING: Delivery suite in a District General Hospital. SUBJECTS: Fifty women at term who did not require oxytocin administration or more than one form of analgesia. Study groups: vaginal delivery with (1) no analgesia, (2) pethidine, or (3) epidural analgesia. Caesarean section under regional analgesia (4) prior to, and (5) after the onset of labour. INTERVENTIONS: Samples of blood were collected from the umbilical artery (UA) and umbilical vein (UV) immediately after fetal delivery prior to placental separation or oxytocic administration. MAIN OUTCOME MEASURES: Plasma oxytocin (OT) concentration, umbilical vein pH, cystine aminopeptidase activity. RESULTS: The geometric mean UA-OT was significantly greater than UV-OT in all groups and was not altered by pethidine; however, epidural administration increased the UA-UV difference. The UA-UV difference at caesarean section was not significantly altered by the onset of labour. There was no correlation between UV pH and UA-UV plasma oxytocin. Cystine aminopeptidase activity was not detectable in UA and UV plasma. CONCLUSIONS: Fetal OT production is increased by epidural but not by pethidine analgesia. It is not influenced by the onset of labour or fetal hypoxia.

Acidosis↗
PubMed1990

Thiazolidine-diones. Biochemical and biological activity of a novel class of tyrosine protein kinase inhibitors.

Various derivatives of thiazolidine-diones have been identified as tyrosine protein kinase inhibitors. The epidermal growth factor (EGF) receptor kinase and c-src kinase were inhibited in vitro with IC50 values in the range of 1-7 microM. The v-abl tyrosine protein kinase was not inhibited by thiazolidine-diones. Inhibition was found to be specific for tyrosine protein kinases. Inhibition of serine/threonine protein kinases was not observed. The active derivatives were shown to inhibit EGF-induced receptor autophosphorylation, either in vitro or in intact cells, and were also found to inhibit growth of the EGF-dependent BALB/MK and A431 cell lines (IC50 1-3 microM). Growth of the interleukin-3-dependent myeloid cell line FDC-P1 was inhibited with equal efficiency. Thus, in these cell lines, members of the c-src kinase family are also potential targets for inhibition by the compounds.

Animals↗
PubMed1988

Identification of T epitopes within a potential Plasmodium falciparum vaccine antigen. A study of human lymphocyte responses to repeat and nonrepeat regions of Pf155/RESA.

PBMC from Melanesians who had high antibody reactivities to fusion proteins encompassing the 3' and the 5' repeat regions of the ring infected E surface antigen (Pf155/RESA), were tested for their ability to respond to synthetic and recombinant peptides representing regions of Pf155/RESA. The aim was to identify T cell epitopes within the Ag. Most of the synthetic peptides from the nonrepeat regions of Pf155/RESA were selected for study on the basis of their tendency to form amphipathic alpha-helices. Peptides representing immunodominant B cell epitopes were also tested. Three-quarters of the Melanesian donors responded to the recombinant peptides (Ag 1505 and Ag 632-100) and to the 8 x 4 mer, a synthetic peptide representative of the 3' repeat region. Whereas all the remaining eight peptides tested elicited a response in at least one donor, three peptides (M40, M42, and BTA3) representing sequences in the nonrepeat regions showed greatest promise as potentially useful T epitopes. Responses in control donors were also observed to most of the peptides but the percentage of responders was lower. T cell bulk lines specific to Ag 1505 and Ag 632-100 were established. All donors were HLA tissue typed, but no obvious correlations between responsiveness and HLA type were observed. Our results suggest that there are T cell epitopes within and outside the repeat regions of Pf155/RESA.

Adult↗
PubMed1988

Complications following coxsackievirus B infection.

Coxsackievirus B infection is common in children and young adults, usually causing mild symptoms in the gastrointestinal or upper respiratory tract. However, some patients develop pleurodynia, carditis or aseptic meningitis. This viral infection can be serious in the fetus and fatal in the newborn. Coxsackievirus B infection may cause a postviral fatigue syndrome, juvenile-onset insulin-dependent diabetes mellitus and other chronic diseases.

Child↗
PubMed1988

Nonrespiratory complications of M. pneumoniae infection.

Mycoplasma pneumoniae infection occurs in more than 10 million Americans each year. Most patients have a mild respiratory illness; only 5 percent develop clinical pneumonia. Nonrespiratory complications may involve skin, joints, central nervous system, heart, liver, kidneys or blood; some lead to significant morbidity and mortality. Immune-inflammatory responses appear to be the cause of these manifestations.

Arthritis, Infectious↗