Search

Cycloalkylated biimidazolium dications (A2+) of reduction potentials from -0.4 to -1.4 V form ion pair charge-transfer complexes {A2+ [M(mnt)2]2−} with dithiolene metalates, M = Zn, Ni, Pd, Pt, mnt2− = maleonitrile-2,3-dithiolate. X-ray analyses of {P2BBIm2+[Ni(mnt)2]2−} [P2BBIm2+ = 1,1′,3,3′-bis(propane-1,3-diyl)bibenzimidazolium] and {B2Blm2+ [Pd(mnt)2]2−} [B2BIm2+ = 1,1′,3,3′-bis(butane-1,4-diyl)biimidazolium] reveal that the solid-state structure is largely determined by the geometry of the acceptor. When the latter is strongly twisted, the usually observed mixed donor-acceptor columns are modified to a chain-like arrangement. In the case of the bibenzimidazolium dication P2BBIm2+ the otherwise planar [Ni(mnt)2]2− becomes tetrahedrally distorted. By the application of the Hush model a reorganization energy of about 67 kJ/mol is estimated for the thermal electron transfer from [M(mnt)2]2− to A2+ when M = Ni, Pd, Pt, but considerable deviations from this model are observed when M = Zn. Irradiation of the free biimidazolium acceptors in the presence of EDTA affords the strongly reducing radical cations which reduce water to hydrogen in the presence of colloidal platinum. Attempts to sensitize this reaction by irradiating into the charge-transfer band of {A2+ [M(mnt)2]2−} have failed until now. The molar absorptivity of one biimidazolium radical cation is measured by spectroelectrochemistry.

In human skin fibroblasts, a lysosomal transport system specific for cationic amino acids has been described and named system c. We asked if SLC7A14 (solute carrier family 7 member A14), an orphan protein assigned to the SLC7 subfamily of cationic amino acid transporters (CATs) due to sequence homology, may represent system c. Fusion proteins between SLC7A14 and enhanced GFP localized to intracellular vesicles, co-staining with the lysosomal marker LysoTracker(®). To perform transport studies, we first tried to redirect SLC7A14 to the plasma membrane (by mutating putative lysosomal targeting motifs) but without success. We then created a chimera carrying the backbone of human (h) CAT-2 and the protein domain of SLC7A14 corresponding to the so-called "functional domain" of the hCAT proteins, a protein stretch of 81 amino acids that determines the apparent substrate affinity, sensitivity to trans-stimulation, and (as revealed in this study) pH dependence. The chimera mediated arginine transport and exhibited characteristics similar but not identical to hCAT-2A (the low affinity hCAT-2 isoform). Western blot and microscopic analyses confirmed localization of the chimera in the plasma membrane of Xenopus laevis oocytes. Noticeably, arginine transport by the hCAT-2/SLC7A14 chimera was pH-dependent, trans-stimulated, and inhibited by α-trimethyl-L-lysine, properties assigned to lysosomal transport system c in human skin fibroblasts. Expression analysis showed strong expression of SLC7A14 mRNA in these cells. Taken together, these data strongly suggest that SLC7A14 is a lysosomal transporter for cationic amino acids.

Das folgende Kapitel rekonstruiert – aufbauend auf dem vorangegangenen Metadiskurs uber die soziopolitischen Rahmenbedingungen von Wandel – das Bild des Menschen als politisch befahigtem Akteur, insofern dieser im Diskurs uber gesellschaftliche Transformationsermoglichungen selbst als Trager dieses Wandels entworfen wird. Dieser politisch befahigte Mensch erscheint dabei als Trager von Rechten – ohne dass jedoch damit gleich eine dezidierte Rechtsstaatskonzeption mit entwickelt wurde – und unterscheidet sich dadurch fundamental vom bolschewistischen Entwurf. Denn dieser betrachtet den Menschen wiederum als integralen Bestandteil seiner Klasse, also als Verfugungsmasse (Elias Canetti). Dieser Zugriff erweist sich als hochgradig ambivalent, da der Mensch so einerseits als Angehoriger einer Elite gilt, die einen als historisch notwendig postulierten Wandel tatsachlich zu gestalten vermag, der andererseits jedoch gleichzeitig Subjekt jener Elite und damit dem Vollzug von Wandel ausgeliefert ist. Dieses schizophrene Bild des Menschen als Gestalter und Subjekt des politisch Notwendigen wird vom demokratischen Sozialismus eindeutig und nachhaltig zugunsten eines emanzipierten, also primar gestaltend tatigen Individuums verworfen.

Das Abschlusskapitel erfullt eine doppelte Funktion. Einerseits wird es darum gehen, die wesentlichen Diskursstrange noch einmal zusammenzufassen, anhand derer sich die argumentative Positionierung des Sozialismus – unter Betonung von Demokratie und rechtsstaatlich eingehegter Individualitat – im Prozess des politischen Ringens gegen den Kommunismus nachzeichnen lasst. Daruber hinaus gilt es, hinsichtlich des Transfers des konkreten, historisch verortbaren Diskurses, zu reflektieren, welche zeitunabhangigen Implikationen die projizierte Praxis des antitotalitaren Sozialismus mit Blick auf eine politische Theorie gesellschaftlichen Wandels birgt. Fur eine Gegenwart namlich, die sich mehr und mehr auch fur die etablierten Industriestaaten und die westlichen Demokratien als besonders krisenanfallig und damit als verstarkt wandlungsbedurftig erweist, enthalt der Diskurs moglicherweise interessante Anregungen, die zumindest die Organisation und Gestaltung von Wandlungsphanomenen orientieren konnen.

„Ist der Sozialismus liberal?“ – diese auf den ersten Blick einfache und gleichsam verquer anmutende Frage steckt im Titel eines von Monique Canto-Sperber und Nadia Urbinati herausgegebenen Bandes zur sozialistischen Theorie und Ideengeschichte. Im Kern geht es dabei nicht um eine – wie parteipolitische Puristen meinen konnten – Aufweichung sozialistischen Denkens hin zu liberalen, oder gar libertareren Politikentwurfen im Sinne eines wie auch immer gearteten Dritten Weges. Das Anliegen, das Canto-Sperber und Urbinati verfolgen ist vielmehr politisch-philosophischer Natur, insofern sie bemuht sind, die emanzipatorischen, freiheitlichen und demokratischen Kompetenzen sozialistischen und liberalen Denkens aufzuzeigen, wie das in zeitgenossischer Perspektive etwa Carlo Rosselli, Grunder der antifaschistischen Gruppe Giustizia e Liberta in seinem 1930 erschienenen Buch Le Socialisme liberal formuliert hatte: „Sozialismus, das ist wenn die Freiheit im Leben der Armsten Einzug halt.“

Solutions of differential equations are derived by a recursive procedure. For partial differential equations this solution can be transformed to an operator expression. Stronger conditions than in other solution procedures are required to solve the initial-value or boundary value problem. Examples are given, where this method is more favorable than others.

An experimemtal investigation in a high speed compressor cascade has been carried out to show the effect of different types of secondary flow suction. In order to get deeper insight into the separated three dimensional flow topology and to determine appropriate suction positions, numerical simulations are performed additionally for the baseline cascade. To obtain the flow solution, an implicit, pressure based solver, elaN3D (by ISTA TU Berlin), is employed in steady RANS mode, whereby the Menter SST-k model is used for turbulence treatment. Both investigations are conducted at Mach number Ma = 0.67 and Reynolds number Re = 560.000. The aerodynamic design condition is used. The examined cascade consists of NACA65-K48 type vanes. The experiments include measurements with four different types of suction geometries plus reference measurements. Total pressure and flow angle measurements in the wake show the flow deflection, total pressure loss and the rise of the static pressure of the cascade. The best suction geometry follows the design of R.E. Peacock, designed for low Mach number cascades, with small changes. Using a maximum suction rate of 2% of the main flow the total loss coefficient was reduced by 23%. In this case the stage efficiency — calculated with a reference rotor — is increased by almost 1%. The vacuum pump energy consumption has been taken into account for this calculation. In another case the suction geometry has been chosen in a way that the suction slot is placed along the sidewall from suction side to pressure side following the wall streamlines. With an increased suction rate of 5% of the main flow, the vortex system in the passage is eliminated and the total loss coefficient is decreased to 0.055, which equals to a decrease of 37%. Taking into account that compressors in aero-engines provide bleed air for the plane’s air system, enormous efficiency increase is possible. For this the air bleed valves need to be redesigned.Copyright © 2010 by ASME

Generation of free radicals and subsequent lipid peroxidation have been proposed to contribute to delayed tissue damage following traumatic spinal cord injury (SCI). Ubiquinols (reduced coenzyme Q), ascorbate (vitamin C), and alpha-tocopherol (vitamin E) are endogenous antioxidants; decreases in tissue levels of these compounds may, therefore, reflect ongoing oxidative reactions. In the present studies, alterations in tissue levels of ubiquinol-9 and -10, ascorbate, and alpha-tocopherol were examined after SCI of varying severity in the rat. Levels of alpha-tocopherol did not change significantly after injury. Ascorbate and ubiquinol levels were decreased after trauma. Changes in tissue levels of ubiquinol, but not ascorbate reflected the degree of trauma. Thus, ubiquinol levels may provide a useful marker of the oxidative component of the secondary injury response.

Changes in the total tissue content of water, sodium, potassium, and magnesium were measured in spinal cord from pentobarbital-anesthetized rats subjected to impact trauma (T9) of varying severity (low, 25 g-cm; moderate, 50 g-cm; severe, 100 g-cm). Laminectomized animals served as controls. Spinal cord samples were taken from rats in the high injury group at 15 min, 60 min, 4 hr, 24 hr, 3 days, or 7 days posttrauma. Samples from the low and moderate injury groups were taken at 24 hr postinjury. In all groups, spinal cord tissue was rapidly removed (less than 30 sec), frozen in liquid N2, and dissected into the injured segment and adjacent two caudal and rostral segments. Severe injury caused significant increases in tissue water content; changes were present at 15 min, peaked at 24 hr, and continued at 3-7 days. Sodium levels were increased at 4 hr and remained elevated for up to 7 days. Potassium levels were decreased at 60 min, remained at low levels for up to 3 days, and partially recovered at 7 days. Tissue magnesium levels were significantly decreased only at 4 hr and 24 hr. Changes in water content and total sodium at 24 hr were not correlated with injury severity. Although potassium decreases did correlate with injury severity, alterations in magnesium levels had a much higher degree of correlation. Thus, reductions in magnesium content may contribute to the development of irreversible tissue damage. In contrast, edema formation after spinal cord trauma may be an epiphenomenon, since it was found to an equal degree in low, moderate, and severe injuries.

A new method is proposed to derive ion distributions and the electric potential near charged surfaces. The diffuse double layer is described by a proposed thermodynamic equilibrium condition between electrostatic forces and osmotic pressure. Problems related with the osmotic pressure and the integration of Coulomb forces are investigated in this paper. A numeric example is given based on erythrocyte data.

Ich war im Studienjahr 1990 / 91 in Jena Dozent des DAAD in den Bereichen Biologie und Medizin. Ich mochte zunachst meinen Werdegang darstellen und meine Entscheidung fur Jena. Anschliesend an eine Darstellung meiner Tatigkeit versuche ich eine personliche Einschatzung der Situation an der Hochschule und zu Tendenzen der Wissenschaftsintegration zu geben.

Ischemia to the central nervous system (CNS) may cause tissue damage through both direct and indirect mechanisms (Siesjo, 1981; Raichle, 1983; Krause et al., 1988). Direct effects occur acutely as a result of interruption of blood flow. Indirect effects are delayed and develop over a period of minutes to hours following the ischemic insult; this secondary injury process results, in part, from the action of endogenous biochemical factors that are activated, synthesized, or released in response to ischemia. A partial list of such factors includes phospholipases (Edgar et al., 1982; Hirashima et al., 1984), membrane lipid hydrolysis products (Bazan, 1970; Bazan et al., 1971; Tang and Sun, 1982, 1985; Ikeda et al., 1986), eicosanoids (Moskowitz et al., 1983; Chen et al., 1986), oxygen radical species (Kontos, 1985), monovalent and divalent metal cations (Young et al., 1987; Hoehner et al., 1987), excitatory amino acids (Meldrum, 1985; Rothman and Olney, 1986), and opioid peptides (Faden, 1990). It is likely that the effects of a number of these factors are interactive, with ultimate tissue damage resulting from a complex multifactorial process.

Secondary neurochemical events contribute to progressive tissue damage and subsequent neurological deficit after traumatic spinal-cord injury (SCI). Among proposed injury factors are alterations of phospholipids and certain cations. To clarify the relationship of membrane lipid changes (phospholipids, cholesterol, and arachidonic acid) to changes in tissue content of water and selected ions (sodium, potassium, and magnesium) after SCI, these variables were examined in spinal-cord segments from anesthetized ventilated rabbits subjected to laminectomy or to moderate (40 g-cm) or severe (150 g-cm) impact trauma at the lumbar (L2) segment. Trauma caused significant increases in tissue sodium, water, and arachidonic acid content, and significant decreases in phospholipids, cholesterol, potassium, and magnesium content. Alterations in magnesium were significantly related to injury severity. In contrast, changes in spinal-cord water content occurred to a similar degree in the two injury groups, as did tissue sodium and potassium content. Decreases in phospholipids were strongly correlated with decreases in tissue magnesium content, whereas changes in sodium and potassium were less well-correlated. Because magnesium ions play a critical role with regard to cellular bioenergetic state, calcium flux, amino acid receptor function, and eicosanoid production, reductions in tissue magnesium after injury may be important in the progression of secondary tissue damage.

The mechanisms by which traumatic injury to the central nervous system cause irreversible tissue damage remain speculative. Recent reports suggest that a decrease in tissue total and free Mg2+ concentration may be an important factor in the development of such injury after experimental brain trauma. Although total Mg changes have been reported following spinal cord trauma, no studies have examined spinal cord-free Mg2+. In the present study, we have used phosphorus magnetic resonance spectroscopy to determine intracellular free Mg2+ concentration and atomic absorption spectrophotometry to measure total tissue Mg concentration in rabbit spinal cord prior to and following impact trauma. We report that intracellular free Mg2+ concentration decreases from a pre-injury value of 0.80 +/- 0.12 mM (mean +/- S.E.M.) to 0.31 +/- 0.05 mM at 2 h post-trauma. Following injury there was an associated decrease in total tissue Mg and K concentration, but no alterations in tissue Na or water content.

Alterations in water content and total tissue Na+ and Mg++ of rat spinal cord tissue were followed over time after a 100 g-cm impact injury to the T-9 spinal cord segment. Rats subjected to laminectomy but not trauma served as controls. In the injured segment there was a progressive increase in water content with increased Na+ and decreased Mg++ at 1 hour and 24 hours after trauma. At seven days, water and Na+ content remained elevated, whereas Mg++ levels had returned to preinjury baseline values. Because of its important role in many metabolic and physiological regulatory processes the early decline in Mg++ concentration after trauma may contribute to the development of secondary tissue damage after spinal cord injury.

BW755C is an inhibitor of both cyclo-oxygenase and lipoxygenase, which has been found to have protective effects after myocardial ischemia in dogs. Impact injury to the spinal cord is associated with tissue ischemia as well as with the accumulation of eicosanoids. In the present studies we evaluated the effects of BW755C after traumatic spinalcord injury in rats. Drug treatment reduced thromboxane B2 levels and improved neurological recovery as compared to treatment with equal-volume physiological saline. The findings suggest that this drug or related compounds may be useful for the treatment of clinical spinal cord injury.

Antagonism of N-methyl-d-aspartate (NMDA) excitatory amino acid receptors limits tissue damage after experimental cerebral ischemia. Spinal cord trauma leads to a progressive decline in blood flow that is associated with secondary tissue damage. In the present studies, we evaluated the hypothesis that NMDA receptor activation contributes to the pathophysiology of spinal cord injury by examining the effects of the NMDA antagonist MK801 after impact trauma to rat thoracic spinal cords. MK801, in doses of 1.0 and 5.0 mg/kg administered intravenously (IV) at 15 min after trauma, improved long-term neurologic recovery. At a dose of 1.0 mg/kg, the drug reduced histologic changes as well as alterations in certain tissue cations found after spinal trauma. These findings suggest that excitotoxins contribute to the pathophysiology of spinal cord injury and that early treatment with NMDA antagonists may reduce posttraumatic tissue damage.