Gadolinium as an opener of the outwardly rectifying Cl(-) channel (ORCC). Is there relevance for cystic fibrosis therapy?

There is indirect evidence that the plasmalemma-integrated eukaryotic porin (the voltage-dependent anion-selective channel, VDAC) functions as the outwardly rectifying chloride channel (ORCC). The channel, which is believed to play a role in cell volume regulation, appears to be relevant for cystic fibrosis (CF) therapy, in that it may function as an alternative Cl(-) channel. In the present study we showed first that Gd(3+) altered the voltage dependence of human type-1 porin incorporated into artificial planar lipid bilayers. Next, using a light-scattering approach on transformed normal or CF human B-lymphocytes in hypotonic Ringer solution, we found slightly differing regulatory volume decrease (RVD) curves for the cell lines under study. Addition of 15-60 microM GdCl3 in hypotonic Ringer increased light scattering, pointing to cell swelling beyond normal values. RVD was not observed in those experiments. A corresponding effect was seen in isotonic Ringer containing GdCl3. In either osmotic situation Gd(3+)-induced cell swelling was abolished by monoclonal mouse anti-human type-1 porin antibodies. Agonist and antibody effects were dose dependent. Finally, videocamera-monitored control experiments with adherent HeLa cells verified the direct effect of the agonist on cell swelling in hypo- or isotonic situations and its prevention by the antibodies. We conclude that GdCl3 opens plasmalemma-integrated porin channels, allowing ions to following their gradients, resulting in cell swelling. Since respiratory epithelium expresses porin channels in the apical membrane, the use of gadolinium to activate ORCC may represent a new therapeutic approach in CF.

Hot water immersion to eliminate Escherichia coli O157:H7 on the surface of whole apples: thermal effects and efficacy

The effect of hot water immersion on both the reduction of Escherichia coli O157:H7 on the apple surface and internal temperatures of the apple was assessed in this study. Microbial reductions were measured experimentally, whereas internal temperatures were calculated through a mathematical analysis of experimental heat transfer data obtained from the apples. A method was developed to provide a purely surface-based inoculation of E. coli O157:H7. Rinsing produced no reduction, and treatments at 80 and 95 degrees C produced reductions of more than 5 logs in 15 s or less. The heat transfer analysis based on experimental data was used to calculate surface heat transfer coefficients and predict temperatures throughout the apple. The analysis indicated a low heat transfer rate. Although it reduces thermal degradation, a low heat transfer rate precludes thermal-based reduction of any internalized microorganisms.

Human voltage-dependent anion-selective channel expressed in the plasmalemma of Xenopus laevis oocytes

Recent studies indicate a plasmalemmal localisation of eukaryotic porin, i.e. voltage-dependent anion-selective channel (VDAC), and there is evidence that the channel in this cell compartment is engaged in cell volume regulation. Until recently, others and we have used immuno-topochemical and biochemical methods to demonstrate the integration of the channel into the cell membrane and endoplasmic reticulum of vertebrate cells. In the present study, we used molecular biological methods to induce the heterologous expression of tagged human type-1 porin in oocytes of Xenopus laevis and to illustrate its appearance at the plasma membrane of these cells. Applying confocal fluorescent microscopy, green fluorescent protein attached to the C-terminus of porin could clearly be recorded at the cell surface. N-terminal green fluorescent protein-porin fusion proteins remained in the cytoplasm, indicating a strong influence of the porin N-terminus on protein trafficking to the plasma membrane. FLAG-tagged porin was also expressed in frog oocytes. Here, plasmalemmal expression was observed using anti-FLAG M2 monoclonal antibodies and gold-conjugated secondary antibodies, followed by silver enhancement through scanning electron microscopy. In contrast to the EGFP-porin fusion protein, the influence of the small FLAG-epitope (8 amino acids) did not prevent plasmalemmal expression of N-terminally tagged porin. These results indicate the definite expression of human type-1 porin in the plasma membrane of Xenopus oocytes. They thus corroborate our early data on the extra-mitochondrial expression of the eukaryotic porin channel and are essential for future electrophysiological studies on the channel.

Studies on human porin XXII: cell membrane integrated human porin channels are involved in regulatory volume decrease (RVD) of HeLa cells

Cell volume regulation receives increasing attention not only as the basis of regulatory volume increase or regulatory volume decrease (RVD) of cells in surroundings of changing osmolarity, but also appears to be relevant in cell proliferation, differentiation, and apoptosis. A central event in RVD is the opening of a volume-sensitive chloride/anion channel(s), and blocking this pathway would abolish RVD. This is shown here with monoclonal mouse anti-human type-1 porin antibodies, proving that porin is involved in this process. HeLa cells preincubated with these antibodies dramatically increase their volume within about 1 min after a hypotonic stimulus by 70 mM NaCl Ringer solution, but do not move back toward their starting volume, thus indicating abolished RVD. Corresponding effects are induced by the established anion channel inhibitor DIDS. Video camera monitoring of cell size over time was used as a direct and noninvasive approach. We had already accumulated evidence that plasmalemma integrated eukaryotic porin channels form chloride/anion channels in this cell compartment and that they are involved in cell volume regulation. Finally, the present data again demonstrate the suitability of our anti-porin antibodies in physiological studies.

Studies on human porin XXI: gadolinium opens Up cell membrane standing porin channels making way for the osmolytes chloride or taurine-A putative approach to activate the alternate chloride channel in cystic fibrosis

We recently proposed that cell-membrane-integrated vertebrate porin/voltage-dependent anion-selective channel (VDAC) forms part of the outwardly rectifying chloride channel (ORCC) complex that may be involved in volume regulation. The results we present here support this thesis. According to light scattering measurements micromolar concentrations of Gd(3+) induce cell swelling of human healthy and cystic fibrosis (CF) B-lymphocyte cell lines in isotonic Ringer solution. In high-potassium Ringer solution additional swelling is observed. Gd(3+) induces excessive cell swelling of cell lines in hypotonic Ringer solutions, containing 70 mM NaCl or 135 mM taurine, respectively. The gadolinium effect is lost when NaCl is replaced by Na-gluconate. Using video camera monitoring we show that HeLa cells also swell in micromolar concentrations of Gd(3+) in isotonic taurine Ringer solution. The dose-dependent effect of the agonist was always blocked by extracellular application of anti-human type-1 porin antibodies. Together with data on a decreasing effect of micromolar amounts of gadolinium on the voltage dependence of reconstituted human porin the results prove the involvement of porin channels in the swelling behavior in different cell lines. As a mechanism we propose that ionic gadolinium opens up plasmalemma-integrated porin channels, chloride or taurine then following their concentration gradients into the cells. Furthermore, our data argue for a single pathway for inorganic and organic osmolytes during regulatory volume decrease after cell swelling. There is indirect evidence that porin forms part of the cystic fibrosis relevant ORCC channel. Gadolinium thus may work to open the alternate chloride channel in CF.

Germ tubes and proteinase activity contribute to virulence of Candida albicans in murine peritonitis

Peritonitis with Candida albicans is an important complication of bowel perforation and continuous ambulatory peritoneal dialysis. To define potential virulence factors, we investigated 50 strains of C. albicans in a murine peritonitis model. There was considerable variation in their virulence in this model when virulence was measured as release of organ-specific enzymes into the plasma of infected mice. Alanine aminotransferase (ALT) and alpha-amylase (AM) were used as parameters for damage of the liver and pancreas, respectively. The activities of ALT and AM in the plasma correlated with invasion into the organs measured in histologic sections and the median germ tube length induced with serum in vitro. When the activity of proteinases was inhibited in vivo with pepstatin A, there was a significant reduction of ALT and AM activities. This indicates that proteinases contributed to virulence in this model. Using strains of C. albicans with disruption of secreted aspartyl proteinase gene SAP1, SAP2, SAP3, or SAP4 through SAP6 (collectively referred to as SAP4-6), we showed that only a Deltasap4-6 triple mutant induced a significantly reduced activity of ALT in comparison to the reference strain. In contrast to the Deltasap1, Deltasap2, and Deltasap3 mutants, the ALT induced by the Deltasap4-6 mutant could not be further reduced by pepstatin A treatment, which indicates that Sap4-6 may contribute to virulence in this model.

[Serum lipid levels under chronical treatment with beta-receptor blocking agents in patients with coronary artery disease (author's transl)]

Concerning the effects of beta-receptor blocking agents (beta-RB) on serum lipids levels of total cholesterol, HDL cholesterol and triglycerides were determined in 237 consecutive male patients with coronarographically proven coronary artery disease. 43% (n = 101) of all patients were taking beta-RB. The percentage of factors apt to influence serum lipid levels and the extent of coronary artery disease were similar in the subsets with (group 1) and without (group 2) chronical beta-RB therapy.-The mean values of total cholesterol (group 1: 242 mg%, group 2: 239 mg%) and HDL cholesterol (group 1: 42 mg%, group 2: 41 mg%) were nearly identical; there were, however, significantly enhanced triglyceride concentration under beta-RB therapy (group 1: 222 mg%, group 2: 184 mg%, p less than 0.0125). This difference was most pronounced in patients with one-vessel disease. Patients treated with beta-1-selective RB had lower triglyceride levels than those treated with nonselective RB (208 mg% vs. 222 mg%, n.s.). In accordance with findings of other authors, these data might indicate that serum triglycerides are elevated by chronical administration of beta-RB. It should be a topic of further investigations if the present results can be interpreted the way that chronical application of beta-RB might favour development and/or deterioration of coronary artery disease.

Use of cryopreserved cells in quality control of human lymphocyte assays: analysis of variation and limits of reproducibility in long-term replicate studies

Cryopreserved cells obtained by leucopheresis of normal donors were found to be useful as quality control reagents in long-term studies of human lymphocytes. Enough cells were obtained from one donor on a single day to test aliquots in parallel with patient samples for periods of up to 10 months. The results of E-rosette assays of two such cryopreserved panels, expressed as the mean percentage of lymphoid cells±s.d., were 63·7±8·4 (panel 1) and 52·3±7·8 (panel 2). The results of EAC-rosette assays on these cells were 6·2±1·7 and 11·3±6·0. These data were comparable to the values of 69·3±2·3 for E-rosettes and 6·5±4·9 for EAC-rosettes obtained using fresh cells from normal individuals. The long-term variation in rosette assays was also comparable to that in replicate samples counted on a single day. Detailed analysis of 155 serial tests showed that much of the variation was inherent in the microscope counting procedures and sampling errors. The cryopreserved cells were also used in lymphocyte stimulation assays with the mitogens concanavalin A, phytohaemagglutinin P and pokeweed. In mitogen assays, the principal sources of variation were found to be initial cell viability and incubation conditions. The major limitation of cryopreserved cells was that they did not control for the variation encountered in the gradient procedures used to separate lymphocytes from blood. Nevertheless, cryopreserved cells have been shown to be valuable for defining the limits of reproducibility in these assays and their consistent use has increased our confidence in the interpretation of day to day results on patient samples.

Lymphocyte stimulation by yeast phase Histoplasma capsulatum in presumed ocular histoplasmosis syndrome

We measured skin reactions serum antibody, and lymphocyte stimulation to Histoplasma antigens in a series of patients with presumed ocular histoplasmosis syndrome and in controls. The most sensitive test, lymphocyte stimulation to H. capsulatum sonicate, also correlated with severity of the disease. Lymphocyte stimulation to Histoplasma may be a useful adjunct to the monitoring of presumed ocular histoplasmosis syndrome.