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W Lukas

Publications and source records attributed to W Lukas.

At least 19 recordsLinked to original sources
PubMed1996

The S. cerevisiae outwardly-rectifying potassium channel (DUK1) identifies a new family of channels with duplicated pore domains.

Potassium channel subunits have six or two transmembrane segments in addition to a conserved pore-forming (P) domain; four subunits come together to form a channel. A gene was identified in S. cerevisiae (J0911) encoding a protein with eight probable membrane-spanning segments and two such P regions. This protein (Duk1p) is a potassium channel because Xenopus oocytes injected with the corresponding RNA express potassium currents activated by depolarization that are not seen in control oocytes. Similar potassium currents were recorded from wildtype S. cerevisiae spheroplasts, but not from those in which the DUK1 locus had been disrupted. Cells carrying the duk1 delta 1::HIS disruption in addition to a chimeric gene comprising DUK1 behind the GAL1 promoter showed outward currents when grown in galactose, but not when grown in glucose. Additional sequences with the duplicate pore motif were found in C. elegans, suggesting that these proteins represent a novel structural family of potassium channel proteins.

Amino Acid Sequence↗
PubMed1994

Functional properties of a cloned 5-hydroxytryptamine ionotropic receptor subunit: comparison with native mouse receptors.

1. A comparative study of the whole-cell and single-channel properties of cloned and native mouse 5-hydroxytryptamine ionotropic receptors (5-HT3) was undertaken using mammalian cell lines expressing the cloned 5-HT3 receptor subunit A (5-HT3R-A), superior cervical ganglia (SCG) neurones and N1E-115 cells. 2. No pharmacological difference was found in the sensitivity to the agonists 5-HT and 2-methyl-5-HT, or to the antagonists d-tubocurare and 3-tropanyl-3,5-dichlorobenzoate (MDL-72222). 3. Current-voltage (I-V) relationships of whole-cell currents showed inward rectification in the three preparations. Rectification was stronger both in cells expressing the 5-HT3R-A subunit and in N1E-115 cells when compared with SCG neurones. 4. No clear openings could be resolved in 5-HT-activated currents in patches excised from cells expressing the 5-HT3R-A subunit or N1E-115 cells. Current fluctuation analysis of whole-cell and excised-patch records revealed a slope conductance of 0.4-0.6 pS in both preparations. Current-voltage relationships of these channels showed strong rectification that fully accounted for the whole-cell voltage dependence. 5. In contrast, single channels of about 10 pS were activated by 5-HT in patches excised from SCG neurones. The weak voltage dependence of their conductance did not account completely for the rectification of whole-cell currents. A lower unitary conductance (3.4 pS) was inferred from whole-cell noise analysis. 6. We conclude that the receptor expressed from the cloned cDNA is indistinguishable from the 5-HT3 receptor of N1E-115 cells, suggesting an identical structure for these two receptors. The higher conductance and different voltage dependence of the 5-HT3 receptor in SCG neurones might indicate the participation of an additional subunit in the structure of native ganglionic 5-HT3 receptors. Homo-oligomeric 5-HT3R-A channels may also be present as suggested by the lower conductance estimated by whole-cell noise analysis.

Animals↗
PubMed1994

Cortical neurons containing calretinin are selectively resistant to calcium overload and excitotoxicity in vitro.

Calbindin and the more recently identified protein calretinin are structurally related calcium-binding proteins having a broad distribution in the brain. Recent evidence supports a neuroprotective role for calbindin in regulating calcium homeostasis during periods of heightened Ca2+ influx. It is not known if calretinin might have a similar function. We investigated if calretinin-containing neurons have a survival advantage in rat neocortical cultures treated with a calcium ionophore or excitatory amino acids. Neuronal cultures were challenged with the calcium ionophore A23187 at different concentrations to produce a broad range of cell death. Cell loss was quantified for both the calretinin immunopositive and the calretinin immunonegative populations of neurons. We found that 3 h after exposure to 2 microM A23187 there was a 48% loss of the calretinin immunonegative population of neurons whereas the calretinin immunopositive set of neurons was reduced by only 18%. Calretinin positive neurons were still relatively spared after treatment with 3 microM A23187. The ionophore had no cytotoxic effect when calcium ions were removed from the extracellular medium. We also studied glutamate excitotoxicity by treating the neuronal cultures with the excitatory amino acids glutamate, N-methyl-D-aspartate or kainate for 5 min and examining survival three hours later. We found again that calretinin-containing neurons were relatively spared after exposure to the excitatory amino acids; at doses of N-methyl-D-aspartate and kainate that produced a 32-40% loss of calretinin immunonegative neurons, only 2-10% of calretinin immunopositive neurons died. Similar results were obtained for glutamate. These results demonstrate that neurons containing calretinin are better able to survive disturbances in calcium homeostasis than cells not containing this calcium-binding protein. The fact that this effect was observed with ionophore treatment, as well as excitatory amino acids, suggests that neither the density nor distribution of glutamate receptors on the different cell types was a factor in determining selective vulnerability. We hypothesize that the neuroprotective effect of calretinin is due to the buffering capacities of the protein in a manner analogous to that suggested for calbindin.

Animals↗
PubMed1994

Cord blood levels of potentially neurotoxic pollutants (polychlorinated biphenyls, lead and cadmium) in the areas of Prague (Czech Republic) and Katowice (Poland). Comparison with reference values in The Netherlands. The Czech/Polish/Dutch/German Research Team.

In a preliminary study the levels of four non-planar polychlorinated biphenyls congeners (118, 138, 153 and 180), and of the toxic metals lead and cadmium, and their antagonist selenium and zinc were measured in cord blood from apparently healthy neonates from the region of Prague and Upper Silezia (Katowice). These "background" levels were compared with similar values from neonates in the Netherlands. It was found that the levels of three PCB congeners (138, 153 and 180) were significantly higher in the Prague samples than in the Netherlands; but in the Katowice group they were significantly lower. In Upper Silezia (Katowice) the values of the metals lead and cadmium, and in Prague those of cadmium and selenium were significantly higher than in the Netherlands. The importance of these findings is discussed. It is argued that neurotoxic effects of perinatal exposure can be expected to be more prominent in Central Europe than in Western European countries. A more thorough study is indicated and will be undertaken by a joint Czech/Polish/Dutch/German research group.

Cadmium↗
PubMed1986

Granulocyte viability test in children from an environment with heavy metal pollution.

In a group of 43 school-children living near a zinc plant, the test of granulocyte viability by the method of Cocchi et al, the lead level by flame atomic absorptiometry, and the level of erythrocyte zinc-protoporphyrin by the fluorimetric method were determined in peripheral blood. The mean result of the granulocyte viability test was 6.49%. In 18 children, the proportion of abnormal granulocytes was raised abnormally above 6.0%. The lead level was in the range from 14.1 to 53 micrograms/dl, and the level of erythrocyte ZPP was from 0.3 to 2.1 micrograms/g Hb. No correlation was found between the results of the granulocyte viability test and the blood lead level. The result of a comparison with the ZPP value was of borderline significance (p = 0.05).

Cell Survival↗
PubMed1979

Cyclic 3',5'-adenosine monophosphate (cAMP) in a 42-month-old child with clinical evidence of multiple hormonal disturbances.

In a boy aged 42 months, small stature, retarded psychomotor development, dry skin, excessive thirst, polyuria, cryptorchidism, and rickets were signs of multihormonal disturbances. Contrary to the clinical manifestations, laboratory investigations showed normal or raised levels of hormones (hGH, insulin, T3RU, T4, TSH, PTH). The cAMP level in the plasma was low and its urinary excretion was reduced. After administration of hGH, adrenaline, T3, T4, pitressin, vitamin D3 and aminophylline there was no rise in the cAMP concentration in plasma and urine. In the light of these results it may be assumed that deficient function of the adenyl cyclase system led to development of a clinical syndrome of tissue insensitivity to multiple hormonal factors in this case.

Child, Preschool↗