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At least 1,063 records · Page 59Linked to original sources
PubMed1997

Effect of the thyrotropin releasing hormone analogue posatirelin (RGH 2202) on microanatomical changes induced by lesions of the nucleus basalis magnocellularis in the rat.

The effect of 4 and 8 weeks treatment with 10 mg/kg/day of the thyrotropin releasing hormone analogue posatirelin (L-6-ketopiperidine-2-carbonyl-L-leucyl-proline amide) on microanatomical changes induced by monolateral and bilateral lesions of the nucleus basalis magnocellularis (NBM) were investigated. The following parameters were assessed in the frontal cortex and hippocampus of NBM-lesioned and sham-operated rats: 1) number of nerve cell and glial fibrillary acidic protein (GFAP)-immunoreactive astrocyte profiles; 2) density of silver-gold impregnated fibres; 3) density of choline acetyltransferase (ChAT)-immunoreactive fibres; 4) intensity of acetylcholinesterase (AChE) staining. In NBM-lesioned untreated rats, no changes in the number of nerve cell or of astrocyte profiles were found either in the frontal cortex or in the hippocampus. The only exception was a decrease in the number of granule neuron profiles in the dentate gyrus at 8 weeks after lesioning. Silver-gold impregnated fibres, which express the width of interneuronal connections, were reduced in the hippocampus but not in the frontal cortex of NBM-lesioned rats. ChAT immunoreactivity and AChE reactivity, which were localised respectively in nerve fibre-like structures and in the neuropil, were decreased in the frontal cortex but not in the hippocampus from the fourth week after NBM lesioning. Lesions did not change the number of ChAT-immunoreactive nerve fibres or intensity of AChE staining in the hippocampus. Treatment with posatirelin was without effect on the number of nerve cell profiles or of GFAP-immunoreactive astrocytes both at 4 and 8 weeks after NBM lesioning. Treatment with the compound increased the number of silver-gold impregnated fibres in the hippocampus of NBM-lesioned rats and restored in part ChAT immunoreactivity and AChE reactivity in the frontal cortex. These effects were noticeable in NBM-lesioned rats after 8 weeks of treatment. The possible significance of the neuroprotective effect elicited by posatirelin treatment after lesions of the NBM is discussed.

Acetylcholinesterase↗
PubMed2006

Manipulating the generation of Ca-alginate microspheres using microfluidic channels as a carrier of gold nanoparticles.

In this paper the manipulation of Ca-alginate microspheres, using a microfluidic chip, for the encapsulation of gold nanoparticles is presented. Our strategy is based on hydrodynamic-focusing on the forming of a series of self-assembling sphere structures, the so-called water-in-oil (w/o) emulsions, in the cross-junction microchannel. These fine emulsions, consisting of aqueous Na-alginates, are then dripped into a solution of 20% calcium salt to accomplish Ca-alginate microspheres in an efficient manner. Experimental data show that microspheres with diameters ranging from 50 microm to 2000 microm with a variation less than 5% were precisely generated. The size and gap of the droplets are tunable by adjusting the relative sheath/sample flow rate ratio. Furthermore, we applied them to encapsulated gold nanoparticles, and this one shot operation performs the 'Lab on a Chip'.

Alginates↗
PubMed2005

Gold-polyaniline composites. Part II. Effects of nanometer sized particles.

The amount of electronic charge transferred between gold particles and polyaniline depends not only on the electron affinity of the two materials but also on the size of the gold particles. As measured by X-ray photoelectron spectroscopy, for particles < approximately 5 nm the binding energy of the electrons is size dependent. This "nano-effect" has its origin in the electrostatics of particles. It is demonstrated as a measurable shift of the binding energy of the Au(4f7/2) photoelectrons emitted from Au particles embedded in a polyaniline matrix. Gold nanoparticle size was evaluated by high resolution transmission electron microscopy.

Aniline Compounds↗
PubMed2004

P-glycoprotein in autoimmune diseases.

Multidrug resistance-1 (MDR-1) is characterized by overfunction of P-glycoprotein (P-gp), a pump molecule that decreases intracellular drug concentration by effluxing them from the intracellular space. Broad ranges of structurally unrelated compounds are transported by P-gp, including antineoplastic agents, HIV protease inhibitors, prednisone, gold salts, methotrexate, colchicine as well as several antibiotics. In contrast, many other compounds such as calcium channel blockers (verapamil) and immunosupressors (cyclosporine-A) are able to inhibit P-gp function. The P-gp role in therapeutic failures has been extensively studied in cancer; however, there is little information regarding MDR-1 phenotype in autoimmune disorders. It has been reported that an increased number of lymphocytes are able to extrude P-gp substrates in rheumatoid arthritis, immune thrombocytopenic purpura and systemic lupus erythematosus, the patients with poor response to treatment being the ones that exhibit the highest values. This may be due, at least in part, to a simultaneous long-term usage of several drugs that induce P-gp function. Since abnormally activated cell compartments characterize autoimmune diseases, it is possible that those cells are the ones that exhibit drug resistance. The study of drug resistance mechanisms in autoimmunity may be helpful for the optimization of the current therapeutic schemes through their combination with low doses of P-gp inhibitors.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2003

A new method for the synthesis of hydrophobic gold nanotapes.

Protocols for the synthesis of gold nanoparticles are increasingly focusing on controlling the morphology of the nanocrystals. We demonstrate in this article the facile, one-step synthesis of gold nanotapes that are readily dispersible in organic media. This is accomplished by the spontaneous reduction of aqueous chloroaurate ions by hexadecylaniline molecules present in chloroform at the static interface between water and chloroform. The hexadecylaniline molecules cap the gold nanotapes thus formed, rendering them hydrophobic and dispersible in a range on nonpolar and weakly polar organic solvents. Possible reasons for the growth of gold nanotapes are discussed.

Aniline Compounds↗
PubMed2006

Organization of nanoparticles on hard substrates using block copolymer films as templates.

We present a technique for the organization of pre-synthesized nanoparticles on hard substrates, using block copolymer films as sacrificial templates. A thin block copolymer film is dip-coated on the substrate of interest and the sample is exposed to a solution containing nanoparticles. Spontaneous preferential adsorption of the nanoparticles on one phase of the block copolymer film results in their lateral organization. An oxygen plasma etch is used to remove the polymer film; the nanoparticles end up organized on the substrate. We demonstrate that this is a general approach for the patterning of inorganic nanoparticles on hard substrates, showing the organization of metal and semiconductor nanoparticles having different chemistries at the particle/solvent and solvent/polymer interfaces. The nanoparticle patterns that we present have typical periodicities in the nanometer scale. In some cases, microcontact printing is used to create a double length scale of organization, on the micrometer and on the nanometer level. The characteristic periodicity of the template is studied with respect to the nanoparticle size in order to optimize the organization. Finally, we describe how to extend this technique for the production of continuous gold nanowires on hard substrates. We expect that the flexibility of this approach and the degree of control that can be obtained over nanoparticle organization should make it a powerful tool for nanoscale fabrication.

Cadmium Compounds↗
PubMed1989

Ferrocene modified polypyrrole with immobilised glucose oxidase and its application in amperometric glucose microbiosensors.

Gold microelectrodes were modified with electropolymerised polypyrrole in both organic and aqueous electrolytes. Cyclic voltammetry studies confirmed that electron conduction through the films in aqueous electrolytes is greatly reduced and is inefficient at mediating the oxidation/reduction of solution redox species. Films formed in aqueous electrolyte were also found to be more heterogenous in structure compared to those formed in acetonitrile. Aqueous polymerised films were used as an immobilisation matrix for glucose oxidase, and modified gold micro electrodes were used in the analysis of glucose using hydrogen peroxide detection. It was found that glucose oxidase was strongly absorbed into the films and that the sensors remained stable for several weeks. An improved linear range and oxygen insensitivity was achieved by incorporating the "water-insoluble" electron transfer mediator, dimethyl ferrocene, into the polypyrrole films by absorption. Good currents and response times to glucose addition were obtained from these electrodes, however, the electrodes possessed poor stability caused by the apparent loss of mediator from the films. Greater operational stability was achieved by covalently functionalising the films with the ferrocene derivative, ferrocenecarbonyl chloride. Covalently bound ferrocence was found to be an efficient oxidant of reduced glucose oxidase. Electrodes constructed in this manner possessed a good linear range, oxygen insensitivity and better stability. Electron transfer mechanisms are discussed.

Biosensing Techniques↗
PubMed2006

Cationic, linear Au(I) N-heterocyclic carbene complexes: synthesis, structure and anti-mitochondrial activity.

Six linear, two-coordinate cationic Au(I) N-heterocyclic carbene complexes of the form [(R2Im)2Au]+ (R = Me 1, Me, Et 2, i-Pr 3, n-Bu 4, t-Bu 5 and Cy 6) have been prepared by the reaction of two equivalents of the appropriate dialkylimidazol-2-ylidene (R2Im) with (Me2S)AuCl in dmf. Single crystal structural studies for 1.PF6, 2.PF6), 3.Cl and 4-6.PF6 show that for all six complexes the gold(I) centres have quasi-linear C-Au-C coordination, with quasi-parallel pairs of aromatic imidazole planes, except in 5.PF6 where they are quasi-normal; in the latter, Au-C are 2.038(3), 2.033(3) A, cf. (e.g.) 2.027(2) A. Inter-cation Au...Au are close at 3.487(2), 3.525(2) A in 1PF6 and 2.PF6. The structural studies and low temperature NMR experiments provide no supportive evidence for the presence of pi back-bonding within this series of complexes. The lipophilicities of the six compounds, as estimated from the logarithm of the n-octanol-water partition coefficients (log P), varied across the series within the range -1.09 to 1.73. To investigate their potential as possible anti-mitochondrial anti-tumour agents, five of the compounds have been evaluated for their propensities to induce mitochondrial membrane permeabilization (MMP) in isolated rat liver mitochondria. At concentrations between 1-10 microM compounds 1.Br and 3-6.Cl induced dose-dependent, Ca2+-sensitive mitochondrial swelling at rates that increased with the lipophilicities of the complexes, with the most lipophilic compounds inducing the most rapid onset of swelling. The swelling was completely inhibited by cyclosporin A, the specific inhibitor of the mitochondrial permeability transition pore.

Animals↗
PubMed1966

Bipiperidyl mustard, a new obesifying agent in the mouse.

Bipiperidyl mustard, after conversion to its bis-cyclic immonium ion forme, has been found to cause rapid and extensive lipid deposition in mice given single doses of the drug. The obe sity appears to result from an alkylation reaction; the responses of the treated ani mals to food restriction and realimenta tion resemble those observed in gold thioglucose-treated mice; also in anal ogy to gold thioglucose, the bipiperidyl mustard effects can be counteracted by sulfhydryl compounds. These observa tions are suggestive of a similarity of mode of action between the alkylating agent and gold thioglucose, a conclusion which is supported by preliminary find ings of ventromedial lesions in the hypo thalamus of the bipiperidyl mustard treated mice.

Acetylcysteine↗
PubMed2003

Microbial destruction of cyanide wastes in gold mining: process review.

Microbial destruction of cyanide and its related compounds is one of the most important biotechnologies to emerge in the last two decades for treating process and tailings solutions at precious metals mining operations. Hundreds of plant and microbial species (bacteria, fungi and algae) can detoxify cyanide quickly to environmentally acceptable levels and into less harmful by-products. Full-scale bacterial processes have been used effectively for many years in commercial applications in North America. Several species of bacteria can convert cyanide under both aerobic and anaerobic conditions using it as a primary source of nitrogen and carbon. Other organisms are capable of oxidizing the cyanide related compounds of thiocyanate and ammonia under varying conditions of pH, temperature, nutrient levels, oxygen, and metal concentrations. This paper presents an overview of the destruction of cyanide in mining related solutions by microbial processes.

Bacteria↗
PubMedDate not supplied

Metals and metal compounds in cancer treatment.

Metals and metal compounds have been used in medicine for several thousands of years. In this review we summarized the anti-cancer activities of the ten most active metals: arsenic, antimony, bismuth, gold, vanadium, iron, rhodium, titanium, gallium and platinum. The first reviewed metal, arsenic, presents the anomaly of displaying anti-cancer and oncogenic properties simultaneously. Some antimony derivatives, such as Sb2O3, salt (tartrate) and organic compounds, show interesting results. Bismuth directly affects Helicobacter pylori and gastric lymphoma; the effects of bismuth complexes of 6-mercaptopurine are promising. Gold(I) and (III) compounds show anti-tumour activities, although toxicity remains high. Research into the potential use of gold derivatives is still ongoing. Several derivatives of vanadium show anti-proliferative activity, but their toxicity must be overcome. Several pieces of evidence indicate that iron deprivation could be an excellent therapeutic approach; furthermore, it is synergistic with classic anti-cancer drugs. Rhodium belongs to the same group as platinum and it also presents interesting activity, but with the same nephrotoxicity. Several rhodium compounds have entered phase I clinical trials. In contrast to the platinum complexes, titanium derivatives showed no evidence of nephrotoxicity or myelotoxicity; titanocene dichloride is undergoing clinical trial. The anti-proliferative effect of gallium could be related to its competition with the iron atom; in addition a derivative appears to reverse the multidrug resistance. The last metal reviewed, platinum, has given some of the very best anti-cancer drugs. Four derivatives are used today in the clinic; their mechanism of action and of resistance are described.

Animals↗
PubMed1995

Human exposure to volatile organic compounds: a comparison of organic vapor monitoring badge levels with blood levels.

We undertook a study in Albany, New York, to investigate whether volatile organic compounds (VOCs) were measurable in the blood and in the breathing-zone air of people exposed to gasoline fumes and automotive exhaust. We sampled blood of 40 subjects, placed organic vapor badges on 40 subjects, and obtained personal breathing-zone samples from 24 subjects. We limited this analysis to 19 subjects who wore the organic vapor badges for at least 5 h. VOC levels, as determined by the organic vapor badges, were highly correlated with blood levels of these same compounds. Using detection in blood as the gold standard, we found the badges to be more sensitive than conventional charcoal tube samples in detecting low levels of methyl tert-butyl ether (0.60 vs 0.08), toluene (0.95 vs 0.64), and o-xylene (0.85 vs 0.64). In this study, organic vapor badges provided data on VOC exposure that correlated with blood assay results. These organic vapor badges might provide a convenient means of determining human exposure to VOCs in epidemiologic studies.

Adult↗
PubMed1994

Morphine: new aspects in the study of an ancient compound.

Morphine is the most widely used compound among narcotic analgesics and remains the gold standard when the effects of other analgetic drugs are compared. Apart from its presence in the poppy plant Papaver somniferum, morphine has been shown to be present in milk, cerebrospinal fluid and also in nervous tissue extracts. Recent evidence suggests that biosynthetic pathways for morphine exist in animal and even human tissues such as liver, blood and brain. The most characteristic effect of morphine is the modulation of pain perception resulting in an increase in the threshold of noxious stimuli. Antinociception induced by morphine is mediated via opioid receptors and therefore can be inhibited by opioid antagonists, e.g., naloxone. Nevertheless, consideration of morphine as endogenous ligand for opioid receptors seems to be speculative. Recently, the primary receptor for morphine-type drugs called the mu-opioid receptor has been cloned from rat brain. There is accumulating evidence that morphine actions are, at least partly, due to one of its major metabolite morphine-6-glucuronide in man. It is concluded that further investigations are necessary to elucidate the mechanisms, whereby multiple actions of morphine are expressed in the nervous system.

Amino Acid Sequence↗
PubMedDate not supplied

Molecular shape diversity of combinatorial libraries: a prerequisite for broad bioactivity.

A computational method to rapidly assess and visualize the diversity in molecular shape associated with a given compound set has been developed. Normalized ratios of principal moments of inertia are plotted into two-dimensional triangular graphs and then used to compare the shape space covered by different compound sets, such as combinatorial libraries of varying size and composition. We have further developed a computational method to analyze interset similarity in terms of shape space coverage, which allows the shape redundancy between the different subsets of a given compound collection to be analyzed in a quantitative way. The shape space coverage has been found to originate mainly from the nature and the 3D-geometry (but not the size) of the central scaffold, while the number and nature of the peripheral substituents and conformational aspects were shown to be of minor importance. Substantial shape space coverage has been correlated with broad biological activity by applying the same shape analysis to collections of known bioactive compounds, such as MDDR and the GOLD-set. The aggregate of our results corroborates the intuitive notion that molecular shape is intimately linked to biological activity and that a high degree of shape (hence scaffold) diversity in screening collections will increase the odds of addressing a broad range of biological targets.

Combinatorial Chemistry Techniques↗
PubMed2000

Studies of the Anodic Oxidation of 1,4-Diazabicyclo

The title compound (1) was studied at platinum and gold electrodes in acetonitrile. A reversible oxidation peak occurs at +0.30 V vs the standard potential for ferrocenium ion/ferrocene. This process is followed by a second irreversible anodic peak that is due to the oxidation of the initially formed radical cation to the dication. The principal ultimate product of the first oxidation, the conjugate acid of 1, is also oxidized over the range of potentials corresponding to the second anodic peak. The rate of disappearance of the radical cation of 1 has been determined by cyclic voltammetry. The results are best interpreted in terms of parallel pseudo-first-order decay (k(1) = 0.6 s(-)(1)) and second-order reactions. The first of these second-order reactions is either proton transfer from the radical cation to neutral 1 or hydrogen atom abstraction by the radical cation from neutral 1, reactions that give the same products (k(2) = 100 M(-)(1) s(-)(1)) and are kinetically indistinguishable. The other second-order reaction is the hydrogen-atom-transfer disproportionation of the radical cation giving the conjugate acid of 1 and the immonium ion (k(3) = 100 M(-)(1) s(-)(1)). Both second-order processes must be included to account for the results. The present results are thought to be the first experimental evidence for the occurrence of hydrogen-atom-transfer disproportionation of amine radical cations.

Journal Article↗
PubMed2002

A new redox site as an alternative to ferrocene to study electron transfer in self-assembled monolayers.

The cyclometallated ruthenium complex [Ru(bpy)2(pp)]+ (bpy: 2,2'-bipyridine; pp: 2-(2'-ylphenyl)pyridine) was easily grafted to a omega-alkanethiol and the resulting compound was coadsorbed with 11-hydroxyundecanethiol on gold yielding a Self-Assembled Monolayer (SAM) in an analogous manner as for a ferrocene derivative, as shown by impedance spectroscopy; the kinetics of the heterogeneous electron transfer were shown to be very fast, compared to ferrocene, which makes this new redox site a promising candidate for further studies about molecular wires.

Journal Article↗