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Biomedical subjects

U Strauss

Publications and source records attributed to U Strauss.

6 recordsLinked to original sources
PubMed2001

Simultaneous direct high-performance liquid chromatographic enantioseparation of 2-methylglycidol-1-benzyl ether and 2-methylglycerol-1-benzyl ether using a solvent-switching technique.

Simultaneous HPLC separation of the enantiomers of 3-benzyloxy-2-methyl-1,2-propanediol and the corresponding 3-benzyloxy-2-methyl-1,2-propene oxide could be accomplished on amylose derived Chiralpak AD switching between 10% 2-propanol and 3% 1,2-dimethoxyethane as polar modifier in n-heptane.

Chromatography, Gas↗
PubMed2001

Whole-cell patch-clamp: true perforated or spontaneous conventional recordings?

Perforated whole-cell patch-clamp recordings obtained with nystatin are frequently used to preserve intracellular integrity. However, the perforated-patch configuration may sometimes undergo a spontaneous change into the conventional whole-cell configuration, especially when lymphocytes are investigated. The electrophysiological criteria-- previously described--for establishing the existence of the perforated whole-cell configuration have been shown to be insufficient. Thus, the dye eosin, applied to the pipette solution, was tested as a tool for discriminating between the perforated and the conventional whole-cell configurations on rat T-lymphocytes. The dye never entered the cell from the pipette during the entire measurement in the perforated whole-cell configuration. In contrast, all cells in the conventional whole-cell configuration became red immediately after membrane rupture. Eosin barely changed the currents studied. The results suggest that eosin is a dye of choice for verifying a true perforated-patch configuration.

Animals↗
PubMed2000

K(+) channel-blocking alkoxypsoralens inhibit the immune response of encephalitogenic T line cells and lymphocytes from Lewis rats challenged for experimental autoimmune encephalomyelitis.

Alkoxypsoralens, known as DNA photomodifying agents, have been shown to block voltage-dependent K(+) channels (Kv) as well as to alleviate functional deficits in certain multiple sclerosis (MS) patients in a manner similar to 4-aminopyridine. Since Kv channel blockers are known to inhibit T cell-mediated immune responses both in vitro and in vivo, we investigated the effects of three alkoxypsoralens, 5-methoxypsoralen (5-MOP), 8-methoxypsoralen (8-MOP), and 5,8-diethoxypsoralen (H37), on the following parameters: (1) whole-cell K(+) currents of encephalitogenic, myelin basic protein-specific memory T cell line cells (MBP-TCLC) derived from Lewis rats as measured by patch-clamp technique, (2) proliferation of MBP-TCLC and lymph node cells (LNC) from Lewis rats challenged for experimental autoimmune encephalomyelitis (EAE) by immunisation with spinal cord homogenate as measured by 3H-thymidine incorporation, (3) interferon-gamma (IFN-gamma) secretion of MBP-TCLC as measured by ELISA, and (4) IFN-gamma gene expression of LNC as measured by quantitative reverse transcription polymerase chain reaction (RT-PCR) with ELISA-detection. The examined alkoxypsoralens exhibited suppressive effects on the measured parameters with the same sequence of efficacy: H37>5-MOP>8-MOP. We, therefore, conclude that Kv channel-blocking alkoxypsoralens interfere with voltage-controlled signal transduction in lymphocytes and might thereby suppress immune responses in autoimmune diseases of the central nervous system and most likely also in other autoimmune disorders. Thus, alkoxypsoralens, especially the non-phototoxic substance H37, are new candidates for further studies on K(+) channel blocking immunosuppressive drugs. The agents may exert a dual beneficial effect on demyelinating diseases like MS, because they could attenuate the inflammatory process and improve axonal conductivity.

4-Aminopyridine↗
PubMed1998

K+ currents of encephalitogenic memory T cells decrease with encephalitogenicity while interleukin-2 (IL-2) receptor expression remains stable during IL-2 dependent cell expansion.

Previous studies revealed a linkage between increased K+ current and lymphocyte activation upon non-specific stimulation with mitogenic lectins and antibodies. So far no information is available about the behaviour of K+ currents in specifically autoantigen-stimulated lymphocytes. Therefore, we have investigated K+ currents in encephalitogenic T line cells, specifically stimulated with myelin basic protein, using the whole-cell patch-clamp technique. In parallel, the T cell activation marker interleukin-2 (IL-2) receptor was measured quantitatively by flow cytometry. Outward currents were observed in response to depolarizing voltage steps from a holding potential of -80mV. The peak current density increased with more positive membrane potentials, where the current threshold was about -40mV and the maximum conductance was 1.22nS/pF. This current was characterized by a fast activation and a fast inactivation with half maximal inactivation at -67mV. The sensitivity of the peak current to K+ channel blocking agents was as follows: 4-aminopyridine (4-AP) had a half blocking concentration of 0.4mM and a maximal block of 83.7% at 10mM 4-AP, tetraethyl-ammonium caused a block of 6% at 0.1mM, 15% at 1mM and 40% at 10mM, charybdotoxin blocked 90% at 100nM, whereas iberiotoxin had no effect (all values at a clamped membrane potential of +30mV). The encephalitogenic T cells used in our study reach their highest encephalitogenic potency on day 3 to 4 after the onset of restimulation. Furthermore, K+ currents were measured during the whole course of an in vitro restimulation cycle. The peak currents normalized to cell capacitance reached their maximum on day 2 (326+/- 52.8pA/pF, n = 4) and decreased thereafter as follows: day 3: 139.7 +/- 7.87pA/pF (n = 27), day 4: 85.4 +/- 8.95pA/pF (n = 28) and day 5: 40.9 +/- 7.45pA/pF (n = 17). The activation and inactivation characteristics of the current and its responses to selective blockers were similar at all days after restimulation. In contrast to the K+ current, IL-2 receptor expression was maintained on > 95% of cells until day 6 after restimulation. In conclusion, the K+ currents measured in rat encephalitogenic T cells resemble n-type voltage-gated K+ currents described in mice and man. The comparison of K+ current, IL-2 receptor expression and encephalitogenic potency let us suppose that the observed K+ current represents an early event of specific T cell activation and can serve as a parameter of high functional activity of T cells corresponding to their encephalitogenicity.

Animals↗
PubMed1996

Cicutoxin from Cicuta virosa--a new and potent potassium channel blocker in T lymphocytes.

The effect of cicutoxin, the poisonous principle of the genus Cicuta, on K+ currents of activated T lymphocytes was investigated using the patch clamp technique. Cicutoxin produced a dose-dependent [5 x 10(-6) to 7 x 10(-5) mol/l] and completely reversible block of K+ currents with an EC50 of 1.8 x 10(-5) mol/l. A maximum block of 71% was achieved with cicutoxin at a concentration of 7 x 10(-5) mol/l. Since previous studies have shown that T lymphocyte proliferation is associated with K+ currents, the effect of cicutoxin on T lymphocyte proliferation was studied by means of 3H-thymidine uptake assays. At noncytotoxic concentrations [10(-7) to 5 x 10(-5) mol/l] cicutoxin reduced the 3H-thymidine incorporation dose-dependently. In conclusion, cicutoxin is a potent K+ current blocker which inhibits K+ channel-dependent proliferation of naive and memory T lymphocytes.

Alkynes↗