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Notes: Summary Fibrinolysis induced by the infusion of plasminogen activators into the circulation has been shown to cause coagulation disorders in ascites retransfusion. Dexamethasone is known to inhibit the synthesis of plasminogen activators by peritoneal macrophages. We therefore assessed its potential in preventing the occurrence of fibrinolysis by injecting 16 mg dexamethasone intraperitoneally in 10 patients 24 h before ascites retransfusion was performed. In addition, the effect of dexamethasone upon the activity or concentration of several proteases and antiproteases related to coagulation in plasma and ascites was analyzed on 15 occasions. An increase of the activity of plasminogen, α2-antiplasmin, and antithrombin III, and in the concentration of α1-protease inhibitor in ascites was induced by the dexamethasone injection. However, the reaction was not identical in all patients. Those patients having an increase of plasminogen activities of 0.6 CTA U/ml or more did not show signs of fibrinolysis during retransfusion. The results obtained indicate that intraperitoneal injection of dexamethasone decreases the concentration of plasminogen activators in ascites and thereby reduces the risk of coagulation disorders during retransfusion procedures. Since the effect is variable and not sustained, assessment of preoperative plasminogen concentrations is mandatory in order to prevent complications.

Notes: Summary The concentrations of several proteases and antiproteases known to be present in ascites were tested in plasma and ascitic fluid with regard to their ability to separate ascites according to malignant or nonmalignant disease. Seventeen patients with proven malignant ascites and 37 with ascites due to liver cirrhosis were included. Activities of plasminogen,α 2-antiplasmin, antithrombin-III, and factor V, and the concentration ofα 1-protease inhibitor were significantly higher in the plasma of patients with malignant ascites than in cirrhotic patients. Fibronectin, plasminogen,α 2-macroglobulin,α 1-protease inhibitor, antithrombin-III, and albumin revealed higher concentrations or activities in malignant ascites than in cirrhotic ascites. Due to a wide variation of most parameters, only fibronectin, antithrombin III, andα 1-protease inhibitor in ascites had a sensitivity and specificity higher than 90% for malignant ascites. When the specific protein/albumin ratio was used, only the accuracy of fibronectin was increased reaching a sensitivity and specificity of 100%. The plasma/ascites gradients of the proteins assessed differed significantly, that of fibronectin being much higher (22±7) than that of all other proteins. In malignant ascites fibronectin concentration was only correlated withα 1-protease inhibitor concentration but not with the concentration or activity of all other proteins, while in cirrhotic ascites most proteins revealed a positive correlation. The determination of the fibronectin concentration or the fibronectin/albumin ratio in ascites can differentiate malignant and nonmalignant ascites. All other proteases and antiproteases assessed are of lesser value for this purpose, although most are significantly increased in ascites and plasma of patients with malignant disorders.

Notes: Abstract The unicellular littoral alga Chaetomorpha linum is especially capable of maintaining its cell-turgor constant by regulation of the internal osmotic pressure, when the salinity of the sea water is altered. The decrease or increase of the external potassium concentration is seen to be an important cause of this turgor regulation, as well as the alteration of the external osmotic pressure, which was already known to be an important factor. This has been shown by experiments in artificial sea water with reduced osmolality and variable potassium concentration (1 to 50 mMol/l).

Notes: Summary The water relations parameters and the osmoregulatory response ofEremosphaera viridis were investigated both by using the pressure probe technique and by analyzing the intracellular pool of osmotically active agents. In the presence of various concentrations of different salts a biphasic osmoregulatory response was recorded, consisting of a rapid decrease in turgor pressure due to water loss followed by an increase in turgor pressure to the original turgor pressure value (depending on the salt). The values of turgor pressure, volumetric elastic modulus and hydraulic conductivity depended on the composition of the media. Nonelectrolytes did not cause a turgor recovery after the initial water efflux. The second phase of turgor regulation in the presence of salts was characterised by the intracellular accumulation of ions and sugars and required at least 24 hr. Analysis of the cell sap showed that the increase in the internal osmotic pressure was mainly achieved by accumulation of sucrose. Additionally, accumulation of glucose was observed in illuminated cells in the presence of Rb and K. Electron micrographs suggested that the sucrose was produced by degradation of starch granules. Turgor pressure recovery after salt stress seemed to be dependent on temperature and is well correlated with the according photosynthetic activity. The data suggest that a temperature-dependent enzyme which is activated by potassium or rubidium is involved in the regulatory response.

Notes: Abstract. In this study, electrorotation spectra of individual cells (that is, frequency dependence of cell rotation speed) have been proved to yield information not only about the passive electric properties of cell constituents, but also about the presence of mobile charges within the plasma membrane being part of ion carrier transport systems. Experiments on human erythrocytes pretreated with the lipophilic anion dipicrylamine (DPA) gave convincing evidence that these artificial mobile charges adsorbed to the plasma membrane contributed significantly to the rotational spectrum at relatively low conductivity of the external medium (2–5 mS m−1). Theoretical integration of the mobile charge concept into the single-shell model (viewing the cell as a homogenous sphere surrounded by a membrane) led to a set of equations which predicted electrorotational behavior of DPA-treated cells in dependence on medium conductivity. The quantitative data on the partition and the transmembrane translocation rate of the DPA anion extracted from the experimental rotational spectra agreed well with the corresponding literature values.

Notes: Abstract. The interaction of human red blood cells (RBCs) with diethylenetriamine-pentaacetic acid (DTPA) or its Gd-complex (Magnevist, a widely used clinical magnetic resonance contrast agent containing free DTPA ligands) led to the following, obviously interrelated phenomena. (i) Both compounds protected erythrocytes against electrohemolysis in isotonic solutions caused by a high-intensity DC electric field pulse. (ii) The inhibition of electrohemolysis was observed only when cells were electropulsed in low-conductivity solutions. (iii) The uptake of Gd-DTPA by electropulsed RBCs was relatively low. (iv) (Gd-) DTPA reduced markedly deformability of erythrocytes, as revealed by the electrodeformation experiments using high-frequency electric fields. Taken together, the results indicate that (Gd-) DTPA produce stiffer erythrocytes that are more resistant to electric field exposure. The observed effects of the chelating agents on the mechanical properties and the electropermeabilization of RBCs must have an origin in molecular changes of the bilayer or membrane-coupled cytoskeleton, which, in turn, appear to result from an alteration of the ionic equilibrium (e.g., Ca2+ sequestration) in the vicinity of the cell membrane.

Notes: Abstract. The charge-pulse relaxation spectrum of nonperfused and perfused (turgescent) cells of the giant marine alga Ventricaria ventricosa showed two main exponential decays with time constants of approximately 0.1 msec and 10 msec, respectively, when the cells were bathed in artificial sea water (pH 8). Variation of the external pH did not change the relaxation pattern (in contrast to other giant marine algae). Addition of nystatin (a membrane-impermeable and pore-forming antibiotic) to the vacuolar perfusion solution resulted in the disappearance of the slow exponential, whereas external nystatin decreased dramatically the time constant of the fast one. This indicated (by analogy to corresponding experiments with Valonia utricularis, J. Wang, I. Spieß, C. Ryser, U. Zimmermann, J. Membrane Biol. 157: 311–321, 1997) that the fast relaxation must be assigned to the RC-properties of the plasmalemma and the slow one to those of the tonoplast. Consistent with this, external variation of [K+] o or of [Cl−] o as well as external addition of K+- or Cl−-channel/carrier inhibitors (TEA, Ba2+, DIDS) affected only the fast relaxation, but not the slow one. In contrast, addition of these inhibitors to the vacuolar perfusion solution had no measurable effect on the charge-pulse relaxation spectrum. The analysis of the data in terms of the ``two membrane model'' showed that K+- and (to a smaller extent) Cl−-conducting elements dominated the plasmalemma conductance. The analysis of the charge-pulse relaxation spectra also yielded the following area-specific data for the capacitance and the conductance for the plasmalemma and tonoplast (by assuming that both membranes have a planar surface): (plasmalemma) C p = 0.82 * 10−2 F m−2, R p = 1.69 * 10−2Ω m2, G p = 5.9 * 104 mS m−2, (tonoplast) C t = 7.1 * 10−2 F m−2, R t = 14.9 * 10−2Ω m2 and G t = 0.67 * 104 mS m−2. The electrical data for the tonoplast show that (in contrast to the literature) the area-specific membrane resistance of the tonoplast of these marine giant algal cells is apparently very high as reported already for V. utricularis. The exceptionally high value of the area-specific capacitance could be explained — among other interpretations — by assuming a 9-fold enlargement of the tonoplast surface. The hypothesis of a multifolded tonoplast was supported by transmission electronmicroscopy of cells fixed under maintenance of turgor pressure and of the electrical parameters of the membranes. This finding indicates that the tonoplast of this species exhibited a sponge-like appearance. Taking this result into account, it can be easily shown that the tonoplast exhibits a high-resistance (1.1 Ω m2). Vacuolar membrane potential measurements (performed in parallel with charge-pulse relaxation studies) showed that the potential difference across the plasmalemma was mainly controlled by the external K+-concentration which suggested that the resting membrane potential of the plasmalemma is largely a K+-diffusion potential. After permeabilization of the tonoplast with nystatin the potential of the intact membrane barrier dropped from about slightly negative or positive (−5.1 to +18 mV, n= 13) to negative values (−15 up to −68 mV; n= 8). This indicated that the cytoplasm of V. ventricosa was apparently negatively charged relative to the external medium. Permeabilization of the plasmalemma by addition of external nystatin resulted generally in an increase in the potential to slightly more positive values (−0.8 to +4.3 mV; n= 5), indicating that the vacuole is positively charged relative to the cytoplasm. These findings apparently end the long-term debate about the electrical properties of V. ventricosa. The results presented here support the findings of Davis (Plant Physiol. 67: 825–831, 1981), but are contrary to the results of Lainson and Field (J. Membrane Biol. 29: 81–94, 1976).

Notes: Summary Electrical breakdown of cell membranes is interpreted in terms of an electro-mechanical model. It postulates for certain finite membrane areas that the actual membrane thickness depends on the voltage across the membrane and the applied pressure. The magnitude of the membrane compression depends both on the dielectric constant and the compressive, elastic modulus transverse to the membrane plane. The theory predicts the existence of a critical absolute hydrostatic pressure at which the intrinsic membrane potential is sufficiently high to induce “mechanical” breakdown of the membrane. The theoretically expected value for the critical pressure depends on the assumption made both for the pressure-dependence of the elastic modulus of the membrane and of the intrinsic membrane potential. It is shown that the critical pressure is expected at about 65 MPa. The prediction of a critical pressure could be verified by subjecting human erythrocytes to high pressures (up to 100 MPa) in a hyperbaric chamber. The net potassium efflux in dependence on pressure was used as an criterion for breakdown. Whereas the potassium net efflux was linearly dependent on presure up to 60 MPa, a significant increase in potassium permeability was observed towards higher pressure in agreement with the theory. The increase as indicated by measurements in which the same erythrocyte sample was subjected to several consecutive pressure pulses. Temperature changes in the erythrocyte suspension during compression and decompression were so small (less than 2°C) that they could not account for the observed effects.

Notes: Summary The elastic modulus, ε, for the cell wall ofHalicystis parvula (defined by $$\varepsilon = V\frac{{dP}}{{dV}}$$ ) was determined by two different ways: 1) By measuring the stationary pressure-volume curve and by calculating the long-term elastic coefficient,ɛ s, from the slope of the curve at a given volume and 2) By measuring differential changes in cell turgor pressure and cell volume using the pressure probe technique and by calculating the short-term elastic coefficient, ε, according to the definition equation. The values of the elastic coefficients differ considerably and show different dependences on cell turgor pressure.ɛ s is about 0.5 to 2 bar, and is therefore in agreement with measurements of Graves and Gutknecht (Graves, J., Gutknecht, J. (1976)J. Gen. Physiol. 67 ∶ 579) on perfused cells ofH. parvula.ɛ s is almost pressure independent within the pressure range of 0.05 to 0.9 bar. On the other hand, ε assumes values of about 1 to 2 bar at a low pressure (about 0.05 to 0.15 bar) and increases to about 16 bar at 0.9 bar turgor pressure. Evidence is presented that the short-term elastic coefficient, ε, determined from differential changes in cell turgor pressure,dP, and cell volume,dV, reflects the true elastic properties of the cell wall, whereas the long-term elastic coefficient,ɛ s, also includes other mechanical properties of the cell wall, which could not be identified up to now. The hydraulic conductivity,L p, of the cell membrane ofH. parvula was determined by directly measuring both the turgor pressure relaxation process (pressure probe) and the volume changes (microscope) in response to osmotic stress.L p was calculated from the slope of volume-time curves without knowledge of the elastic modulus. It has a value of about 0.8 to 2×10−6 cm sec−1 bar−1. The calculation ofL p from the turgor pressure relaxation process leads to identical results when using the short-term elastic coefficient. Under these conditionsL p assumes values of about 1.5 to 2.5×10−6 cm sec−1 bar−1.L p increases as the plasmolytic point is approached. The result demonstrates that the short-term elastic coefficient determined by the pressure probe technique controls the instantaneous water transport between the cell interior and the external medium. The high extensibility of the cell wall (resulting from the low elastic coefficient) is the reason whyH. parvula exhibits a change in cell volume rather than a change in cell turgor. The results are discussed in relation to pressure measurements in individual cells of higher plant tissues.

Notes: Summary A new Coulter Counter is described which measures on single microscopic cells the volume, membrane breakdown voltage, and the underestimation of volume after breakdown, this last parameter reflecting in part the internal conductivity of the cells. The system requires very few cells for measurement and does not require the population to be normally distributed in volume or free of debris from the preparation of the cells. The new development is to apply a voltage ramp across a Coulter orifice through which a particle flows. A differential dual orifice system is used to reduce the magnitude of the amplified ramp signal to that of the signal produced by the particle in the presence of a DC voltage across the orifice. Breakdown is detected by an underestimation of the cell volume once a critical voltage across the cell membrane has been established. Measurements made on protoplasts isolated from guard ceils ofVicia faba with a mean volume of 1800 μm3 reveal a breakdown voltage of 1 V and an average volume underestimation of about 30% after breakdown. Variations in this underestimation reflect the different internal structure of the protoplasts in terms of the size and number of nonconducting compartments. Different stages of vacuole development exist in each preparation. The breakdown voltage of 1 V suggests that only one membrane breaks down and that the electromechanical properties of these protoplast membranes are similar to other cell systems, when the pulse length dependence of the breakdown voltage is taken into consideration.