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1.
Pol J Vet Sci ; 17(2): 339-45, 2014.
Article in English | MEDLINE | ID: mdl-24988861

ABSTRACT

The aim of our study was to analyze the anatomy and surgical approach of the rabbit brachial plexus. The research included 18 rabbits. The rabbit seems to be a good experimental model for spinal nerves injury, especially for the C5 and C6 segments. The anatomical structure of the rabbit's brachial plexus is similar to the human brachial plexus. The structure of the rabbit C5 and C6 segments is analogous to the human structure. The spinal nerves of the C5 and C6 segments in the rabbit are wide and long enough for microsurgical procedures.


Subject(s)
Brachial Plexus/anatomy & histology , Rabbits/anatomy & histology , Animals , Female
2.
Phys Rev Lett ; 104(1): 017202, 2010 Jan 08.
Article in English | MEDLINE | ID: mdl-20366388

ABSTRACT

We consider tunneling transport through a Mn12 molecular magnet using spin density functional theory. A tractable methodology for constructing many-body wave functions from Kohn-Sham orbitals allows for the determination of spin-dependent matrix elements for use in transport calculations. The tunneling conductance at finite bias is characterized by peaks representing transitions between spin multiplets, separated by an energy on the order of the magnetic anisotropy. The energy splitting of the spin multiplets and the spatial part of their many-body wave functions, describing the orbital degrees of freedom of the excess charge, strongly affect the electronic transport, and can lead to negative differential conductance.

3.
Nano Lett ; 8(3): 848-52, 2008 Mar.
Article in English | MEDLINE | ID: mdl-18254603

ABSTRACT

We observe spin-valve-like effects in nanoscaled thermally evaporated Co/AlOx/Au tunnel junctions. The tunneling magnetoresistance is anisotropic and depends on the relative orientation of the magnetization direction of the Co electrode with respect to the current direction. We attribute this effect to a two-step magnetization reversal and an anisotropic density of states resulting from spin-orbit interaction. The results of this study points to future applications of novel spintronics devices involving only one ferromagnetic layer.

4.
Rapid Commun Mass Spectrom ; 22(7): 925-9, 2008 Apr.
Article in English | MEDLINE | ID: mdl-18302166

ABSTRACT

We report the results of experimental studies on the effects of sample supports in laser desorption/ionization mass spectrometry (LDI-MS). LDI time-of-flight (TOF) mass spectra obtained for C(60) and insulin samples deposited onto standard stainless steel substrate and/or onto some non-metallic materials (glass, scotch tape, floppy disc foil, Teflon foil, photocopy film), all recorded under identical, typical experimental conditions, have been compared with regard to their intensity and quality. The LDI investigations show that compared with stainless steel, glass and floppy disc foil sample supports boost (2-3.5 times) ion yields for C(60)(+) and C(60)(-) ions, respectively. The stainless steel and scotch tape sample supports are the best for the mass resolution of positive ions and the formation of (C(60))(n)(-) (n

Subject(s)
Biocompatible Materials/chemistry , Fullerenes/chemistry , Insulin/chemistry , Spectrometry, Mass, Electrospray Ionization/methods , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/methods , Materials Testing , Reproducibility of Results , Sensitivity and Specificity , Specimen Handling/methods
5.
Nano Lett ; 7(1): 81-5, 2007 Jan.
Article in English | MEDLINE | ID: mdl-17212444

ABSTRACT

We have investigated spin accumulation in Ni/Au/Ni single-electron transistors assembled by atomic force microscopy. The fabrication technique is unique in that unconventional hybrid devices can be realized with unprecedented control, including real-time tunable tunnel resistances. A grid of Au disks, 30 nm in diameter and 30 nm thick, is prepared on a SiO2 surface by conventional e-beam writing. Subsequently, 30 nm thick ferromagnetic Ni source, drain, and side-gate electrodes are formed in similar process steps. The width and length of the source and drain electrodes were different to exhibit different coercive switching fields. Tunnel barriers of NiO are realized by sequential Ar and O2 plasma treatment. By use of an atomic force microscope with specially designed software, a single nonmagnetic Au nanodisk is positioned into the 25 nm gap between the source and drain electrodes. The resistance of the device is monitored in real time while the Au disk is manipulated step-by-step with angstrom-level precision. Transport measurements in magnetic field at 1.7 K reveal no clear spin accumulation in the device, which can be attributed to fast spin relaxation in the Au disk. From numerical simulations using the rate-equation approach of orthodox Coulomb blockade theory, we can put an upper bound of a few nanoseconds on the spin-relaxation time for electrons in the Au disk. To confirm the magnetic switching characteristics and spin injection efficiency of the Ni electrodes, we fabricated a test structure consisting of a Ni/NiO/Ni magnetic tunnel junction with asymmetric dimensions of the electrodes similar to those of the single-electron transistors. Magnetoresistance measurements on the test device exhibited clear signs of magnetic reversal and a maximum tunneling magnetoresistance of 10%, from which we deduced a spin polarization of about 22% in the Ni electrodes.


Subject(s)
Electrodes , Gold/chemistry , Nickel/chemistry , Spin Labels , Electrons , Microscopy, Atomic Force , Nanotechnology
6.
Phys Rev Lett ; 97(9): 096804, 2006 Sep 01.
Article in English | MEDLINE | ID: mdl-17026391

ABSTRACT

We present a theory of single-electron tunneling transport through a ferromagnetic nanoparticle in which particle-hole excitations are coupled to spin collective modes. The model employed to describe the interaction between quasiparticles and collective excitations captures the salient features of a recent microscopic study. Our analysis of nonlinear quantum transport in the regime of weak coupling to the external electrodes is based on a rate-equation formalism for the nonequilibrium occupation probability of the nanoparticle many-body states. For strong electron-boson coupling, we find that the tunneling conductance as a function of bias voltage is characterized by a large and dense set of resonances. Their magnetic field dependence in the large-field regime is linear, with slopes of the same sign. Both features are in agreement with recent tunneling experiments.

7.
J Chem Phys ; 120(6): 2686-92, 2004 Feb 08.
Article in English | MEDLINE | ID: mdl-15268412

ABSTRACT

Using a newly constructed three sector field mass spectrometer (resulting in a BE1E2 field configuration) we have measured the kinetic energy release distributions of neon, argon, and krypton cluster ions. In the present study we used the first two sectors, B and E1, constituting a high resolution mass spectrometer, to select the parent ions in terms of mass, charge, and energy, and studied the decay of those ions in the third field free region. Due to the improved mass resolution we were able to extend earlier studies carried out with a two sector field machine, where an upper size limit arose from the fact that several isotopomers contribute to a decaying parent ion beam when the cluster size exceeds a certain value. Furthermore we developed a new data analysis. It allows us to model also fragment ion peaks that are a superposition of different decay reactions and thus we can determine the average kinetic energy release for all decay reactions of a given cluster ion. In a further step we used these results to determine the binding energies of cluster ions Rg(n) (n> or =10) by applying finite heat bath theory. The smaller sizes have not been included in this analysis, because the validity of finite heat bath theory becomes questionable below n approximately 10. The present average kinetic energy releases and binding energies are compared with other experiments and various calculations.

8.
Rapid Commun Mass Spectrom ; 15(24): 2383-6, 2001.
Article in English | MEDLINE | ID: mdl-11746906

ABSTRACT

The effect of impurity (sodium sulfate Na2SO4; copper sulfate CuSO4; potassium ferrocyanide K4Fe(CN)6; and triammonium citrate (NH4)3C6H5O7) concentration on the positive matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) spectra of insulin is described. 2,5-Dihydroxybenzoic acid was used as a desorption matrix. The estimated maximum concentrations of tested salts for which no insulin signal was observed were determined.


Subject(s)
Gentisates , Hypoglycemic Agents/analysis , Insulin/analysis , Drug Contamination , Hydroxybenzoates , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
9.
Rapid Commun Mass Spectrom ; 14(16): 1455-61, 2000.
Article in English | MEDLINE | ID: mdl-10931537

ABSTRACT

An electron impact ion source on a double focusing sector field mass spectrometer was used to investigate ammonia micro-clusters produced by the adiabatic free jet expansion of ammonia gas. The appearance energies for [NH(3)](n)(+), n

10.
Arch Pharm (Weinheim) ; 328(6): 531-3, 1995 Jun.
Article in English | MEDLINE | ID: mdl-7677568

ABSTRACT

DMAP reacts readily with chloromethylcycloalkyl ethers and alpha-chloroethyl alkyl ethers to give stable (1a-1e) and unstable (2a-2h) pyridinium chlorides. Reaction of these chlorides with NaOH produces the corresponding 4-pyridones. All the chlorides synthesized showed antibiotic activity. Particularly high activity against microbes representing cocci, rods, fungi, and bacilli was shown by 1-cyclododecyloxymethyl-4-dimethylaminopyridinium chloride 1d and 1-[(1-dodecyloxy)ethyl]-4-dimethylaminopyridinium chloride 2f.


Subject(s)
Anti-Bacterial Agents/chemical synthesis , Pyridinium Compounds/chemical synthesis , Anti-Bacterial Agents/pharmacology , Bacteria/drug effects , Candida/drug effects , Magnetic Resonance Spectroscopy , Microbial Sensitivity Tests , Pyridinium Compounds/pharmacology
12.
Glia ; 10(2): 114-20, 1994 Feb.
Article in English | MEDLINE | ID: mdl-8168865

ABSTRACT

The release of preloaded radiolabeled taurine (TAU) from cultured rabbit Müller cells [14-21 days in vitro (DIV)] was measured before and after treatment with the following stimuli: 1) isoosmotic 65 mM KCl; 2) a medium made hypoosmotic by uncompensated lowering of Na+ by 40-100 mM; and 3) NH4Cl ranging from 0.25 to 5 mM. The same stimuli were tested for their effect on the cell volume by the 3-O-methyl-D-glucose (OMG) uptake method of Kletzien et al. (Anal Biochem 68:537, 1975). Hypoosmotic media and 65 mM KCl stimulated TAU release, and the release was well correlated with the increase of cell volume. The stimulatory effect of 65 mM KCl was abolished by isotonic removal of Cl- or Na+, and omission of either ion markedly enhanced the basal release of TAU. The results are roughly consistent with the characteristics of the swelling-induced TAU release reported for cultured astrocytes and neurons of various CNS regions, and also for freshly isolated, nondissociated retina. Taken together, the results are indicative of a significant role of TAU release from Müller cells, in the osmosensory response of the retina. Ammonium chloride stimulated TAU release in a dose-dependent manner, a significant stimulation being already observed at 0.5 mM, a concentration that is frequently measured in brain during acute hyperammonemia. The effect of NH4Cl was strictly chloride dependent at 0.5-2 mM, but partly Cl- independent at 5 mM. The Kletzien's method did not appear to be well suited for measuring cell volume in the presence of ammonium ions.(ABSTRACT TRUNCATED AT 250 WORDS)


Subject(s)
Chlorides/pharmacology , Potassium/pharmacology , Quaternary Ammonium Compounds/pharmacology , Retina/metabolism , Sodium/pharmacology , Taurine/metabolism , Animals , Cells, Cultured , Ions , Osmolar Concentration , Rabbits , Retina/cytology
14.
Brain Res ; 618(2): 299-302, 1993 Aug 06.
Article in English | MEDLINE | ID: mdl-8104085

ABSTRACT

The effects of hepatic encephalopathy (HE) due to thioacetamide (TAA)-induced liver failure and hyperammonemia (HA) produced by repeated i.p. administration of ammonium acetate on the activity of glutamate dehydrogenase (GlDH) in the direction of glutamate (Glu) synthesis from--(GlDH-NADH) or its oxidation to alpha-ketoglutarate (alpha-KG) (GlDH-NAD), respectively, were examined in non-synaptic and synaptic mitochondria from rat cerebral hemispheres. In non-synaptic mitochondria, HE and HA stimulated the GlDH-NADH activity by, respectively, 33% and 49%, but neither condition affected the GlDH-NAD activity. In synaptic mitochondria, HE and HA decreased the GlDH-NADH activity by, respectively, 31% and 28%, but stimulated the GlDH-NAD activity by as much as 90% (HE) and 100% (HA). Kinetic assays revealed that HA increased the Vmax of the synaptic mitochondrial GLDH-NAD by 105%, without affecting the Km for Glu. The stimulation of GlDH-NAD favors the oxidation of synaptic Glu to alpha-KG, and may represent an adaptive response serving to counteract hyperammonemia-induced decrease of cerebral alpha-KG production in other metabolic pathways.


Subject(s)
Ammonia/blood , Brain/enzymology , Glutamate Dehydrogenase/metabolism , Glutamates/metabolism , Hepatic Encephalopathy/enzymology , Mitochondria/enzymology , Synapses/enzymology , Animals , Brain/ultrastructure , Glutamic Acid , Hepatic Encephalopathy/chemically induced , Ketoglutaric Acids/metabolism , Kinetics , Oxidation-Reduction , Rats , Rats, Wistar , Stimulation, Chemical , Thioacetamide
15.
Mol Chem Neuropathol ; 18(3): 257-65, 1993 Apr.
Article in English | MEDLINE | ID: mdl-8507304

ABSTRACT

The activities of the cytoplasmic and plasma membrane marker enzymes: lactate dehydrogenase (LDH) and acetylcholinesterase (AChE), respectively, were measured in the cerebral homogenates, in the synaptic and nonsynaptic mitochondrial fractions, and in the postmitochondrial supernatants derived from rats in which a 3-d, moderately hyperammonemic condition (no more than 120% increases in blood ammonia) was produced by repeated administration of ammonium acetate (simple hyperammonemia, SHA) or a hepatotoxin, thioacetamide (TAA) (hepatic encephalopathy, HE). As measured in the homogenate and postmitochondrial supernatants, neither of the enzyme activities was affected by SHA or HE. SHA and HE increased the synaptic mitochondrial LDH activity by respectively 53 and 24%, but reduced this enzyme activity in nonsynaptic mitochondria by 19%. Both conditions stimulated the synaptic and nonsynaptic mitochondrial AChE activity by 30-40%. By contrast, the only significant change produced in these fractions by in vitro treatment with a toxic (3 mM) concentration of ammonium chloride was a slight decrease of LDH activity in nonsynaptic mitochondria and postmitochondrial supernatants. It is concluded that moderate hyperammonemia modifies subsequent separation of both cerebral classes of mitochondria from the cytosolic and plasma membrane components. This modification is likely to reflect subtle hyperammonemia-related changes in the physicochemical properties of the two mitochondrial classes and/or other subcellular components.


Subject(s)
Acetylcholinesterase/metabolism , Ammonia/blood , Cytoplasm/enzymology , L-Lactate Dehydrogenase/metabolism , Mitochondria/enzymology , Synapses/enzymology , Animals , Biomarkers , Cell Membrane/enzymology , Chemical Phenomena , Chemistry, Physical , Hepatic Encephalopathy/chemically induced , Hepatic Encephalopathy/enzymology , Nerve Tissue Proteins/metabolism , Rats , Rats, Wistar , Subcellular Fractions/enzymology
16.
Arch Pharm (Weinheim) ; 326(4): 237-40, 1993 Apr.
Article in German | MEDLINE | ID: mdl-8494485

ABSTRACT

Syntheses and antimicrobial activity of 3-alkoxymethyl-1-ethyl-, 3-alkylthiomethyl-1-ethyl-, 3-alkoxymethyl-1-butyl-, and 3-alkylthiomethyl-1-butylbenzimidazolium chlorides are described. The compounds were obtained by reaction of 1-ethyl- or 1-butylbenzimidazole with chloromethylalkyl ethers or chloromethylalkyl sulfide. Antibacterial properties were tested on 13 strains of bacteria and fungi. 3-Dodecylthio-methyl-1-ethyl-benzimidazolium chloride exhibited the highest antibacterial activity.


Subject(s)
Anti-Infective Agents/chemical synthesis , Bacteria/drug effects , Benzimidazoles/chemical synthesis , Fungi/drug effects , Anti-Bacterial Agents , Anti-Infective Agents/pharmacology , Benzimidazoles/pharmacology , Chromatography, High Pressure Liquid , Microbial Sensitivity Tests
17.
Neurochem Res ; 18(2): 119-23, 1993 Feb.
Article in English | MEDLINE | ID: mdl-8474555

ABSTRACT

The effects of in vitro treatment with ammonium chloride, hepatic encephalopathy (HE) due to thioacetamide (TAA) induced liver failure and chronic hyperammonemia produced by i.p. administration of ammonium acetate on the two components of the multienzyme 2-oxoglutarate dehydrogenase complex (OGDH): 2-oxoglutarate decarboxylase (E1) and lipoamide dehydrogenase (E3), were examined in synaptic and nonsynaptic mitochondria from rat brain. With regard to E1 the response to ammonium ions in vitro (3 mM NH4Cl) was observed in nonsynaptic mitochondria only and was manifested by a 21% decrease of Vmax and a 35% decrease of Km for 2-oxoglutarate (2-OG). By contrast, both in vivo conditions primarily affected the synaptic mitochondrial E1: TAA-induced HE produced an 84% increase of Vmax and a 38% increase of Km for 2-OG. Hyperammonemia elevated Vmax of E1 by 110% and Km for 2-OG by 30%. HE produced no effect at all in nonsynaptic mitochondria while hyperammonemia produced a 35% increase of Vmax and a 30% increase of Km for 2-OG of E1. Both in vivo conditions produced a 20% increase of E3 activity in synaptic mitochondria, but no effect at all in nonsynaptic mitochondria. The preferential sensitivity of E1 to ammonium chloride in vitro in nonsynaptic mitochondria and hyperammonemic conditions in vivo in synaptic mitochondria may play a crucial role in the compartmentation of OGDH responses under analogous conditions. These results confirm the intrinsic differences between the OGDH properties in the synaptic and nonsynaptic brain compartments.


Subject(s)
Ammonia/blood , Brain/enzymology , Hepatic Encephalopathy/enzymology , Ketoglutarate Dehydrogenase Complex/chemistry , Mitochondria/enzymology , Synapses/enzymology , Acetates , Animals , Brain/ultrastructure , Catalysis , Hepatic Encephalopathy/chemically induced , In Vitro Techniques , Rats , Rats, Wistar
19.
Metab Brain Dis ; 6(4): 187-97, 1991 Dec.
Article in English | MEDLINE | ID: mdl-1812392

ABSTRACT

The effects of in vitro treatment with ammonium chloride, hepatic encephalopathy (HE) due to thioacetamide (TAA) induced liver failure and chronic hyperammonemia produced by i.p. administration of ammonium acetate on the activity of the two malate-aspartate shuttle enzymes: aspartate aminotransferase (AAT), malate dehydrogenase (MDH), and on the pyruvate carboxylase (PC) activity were examined in synaptic and nonsynaptic mitochondria from rat brain. With regard to the shuttle enzymes the response to ammonium ions in vitro (3mM NH4Cl) was observed in nonsynaptic mitochondria only, and was manifested by a 27% decrease of AAT activity and a 16% decrease in MDH activity. By contrast, both in vivo conditions primarily affected the synaptic mitochondrial enzymes: TAA-induced HE produced a 26% decrease of synaptic mitochondrial AAT and a 50% decrease of synaptic mitochondrial MDH. Hyperammonemia inhibited synaptic mitochondrial AAT by 30% and synaptic mitochondrial MDH by 45%. HE produced no effect at all in nonsynaptic mitochondria while hyperammonemia produced a 30% increase in the AAT activity, but no changes in MDH. All the experimental conditions affected the nonsynaptic mitochondria PC: ammonium chloride in vitro produced a 20% decrease, TAA-induced HE--a 30% decrease, whereas hyperammonemia inhibited the enzyme by 53%. The PC activity in synaptic mitochondria was very low (about 2% of that measured in nonsynaptic mitochondria), which is consistent with the primarily astrocytic localization of the enzyme.


Subject(s)
Ammonia/pharmacology , Aspartate Aminotransferases/metabolism , Hepatic Encephalopathy/enzymology , Malate Dehydrogenase/metabolism , Mitochondria/enzymology , Pyruvate Carboxylase/metabolism , Synapses/enzymology , Ammonia/blood , Animals , In Vitro Techniques , Mitochondria/drug effects , Nerve Tissue Proteins/metabolism , Rats , Rats, Inbred Strains , Synapses/drug effects
20.
Acta Neurobiol Exp (Wars) ; 51(5-6): 165-9, 1991.
Article in English | MEDLINE | ID: mdl-1687972

ABSTRACT

The metabolism of [1-14C] glutamate to 14CO2 and the glutamate dehydrogenase (GLDH) activity towards alpha-ketoglutarate (alpha-KG) formation were measured in bulk isolated astrocytes derived from control rats and rats with acute hepatic encephalopathy (HE) induced with thioacetamide. In addition, the effects of in vitro treatment of control and HE astrocytes and non-synaptic mitochondria with toxic (3mM) NH4Cl concentration were followed. [1-14C] glutamate oxidation measured as a whole was identical in control and HE astrocytes and was inhibited by ammonia to the same degree in either fraction. In the presence of a glutamate transamination inhibitor--3mM aminooxyacetic acid (AOA), when only the GLDH-mediated part (25% of total) of the glutamate oxidation remained active, the inhibitory effect of ammonia treatment was much more pronounced in HE astrocytes than in control astrocytes. The ability of non-synaptic mitochondria to utilize glutamate to CO2 was not changed in presence of 3mM NH4Cl, whereas a substantial decrease of CO2 production (about 80%) in both the control and HE preparations was observed in the presence of 3mM AOA. GLDH activity was not at all affected by either of the experimental conditions, both in astrocytes and purified non-synaptic mitochondria. Thus, the inhibition of glutamate oxidation in astrocytes by ammonia and the compounded inhibitory effect of HE, ammonia and AOA appeared to be located beyond the glutamate dehydrogenation step within the tricarboxylic acid cycle.


Subject(s)
Ammonia/pharmacology , Astrocytes/metabolism , Brain/metabolism , Glutamates/metabolism , Hepatic Encephalopathy/metabolism , Mitochondria/metabolism , Animals , Brain/drug effects , Brain/ultrastructure , Female , Glutamic Acid , In Vitro Techniques , Mitochondria/drug effects , Oxidation-Reduction , Rats , Rats, Inbred Strains
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