[Small renal mass]. / Der kleine Nierentumor.

The frequent application of ultrasound and radiological imaging for non-urological indications in recent years has resulted in an increase in the diagnosis of small renal masses. The treatment options for patients with a small renal mass include active surveillance, surgery (both open and minimally invasive) as well as ablative techniques. As there is a risk for metastatic spread even in small renal masses surgical extirpation remains the treatment of choice in most patients. Ablative procedures, such as cryoablation and radiofrequency ablation are appropriate for old and multi-morbid patients who require active treatment of a small renal mass. Active surveillance is an alternative for high-risk patients. Meticulous patient selection by the urologist and patient preference will determine the choice of treatment option in the future.

A human schwannoma cell line supports the in vitro adhesion of Plasmodium falciparum infected erythrocytes to chondroitin-4-sulfate.

The paucity of human cell lines expressing defined receptors for the cytoadhesion of erythrocytes infected with the human malarial parasite Plasmodium falciparumhas hampered the investigation of this important virulence property. Here, we investigate a permanent cell line derived from a human, malignant schwannoma, termed HMS-97, and show that this cell line expresses chondroitin-4-sulfate as the only surface receptor to which P. falciparum-infected erythrocytes can cytoadhere. Other common receptors for parasite adhesion, including CD36, vascular cellular adhesion molecule-1 (VCAM), intercellular adhesion molecule-1 (ICAM-1), and E-selectin are absent. Thus, HMS-97 cells are a useful tool for the study of P. falciparum adhesion to chondoitin-4-sulfate, the main receptor for parasite sequestration in the placenta. As chondoitin-4-sulfate can be readily cleaved from the cells, HMS-97 cells are also an ideal system for expressing recombinant adhesion receptors and studying their function in binding assays.

Functional properties of Drosophila inositol trisphosphate receptors.

The functional properties of the only inositol trisphosphate (IP(3)) receptor subtype expressed in Drosophila were examined in permeabilized S2 cells. The IP(3) receptors of S2 cells bound (1,4,5)IP(3) with high affinity (K(d)=8.5+/-1.1 nM), mediated positively co-operative Ca(2+) release from a thapsigargin-sensitive Ca(2+) store (EC(50)=75+/-4 nM, Hill coefficient=2.1+/-0.2), and they were recognized by an antiserum to a peptide conserved in all IP(3) receptor subtypes in the same way as mammalian IP(3) receptors. As with mammalian IP(3) receptors, (2,4,5)IP(3) (EC(50)=2.3+/-0.3 microM) and (4,5)IP(2) (EC(50) approx. 10 microM) were approx. 20- and 100-fold less potent than (1,4,5)IP(3). Adenophostin A, which is typically approx. 10-fold more potent than IP(3) at mammalian IP(3) receptors, was 46-fold more potent than IP(3) in S2 cells (EC(50)=1.67+/-0.07 nM). Responses to submaximal concentrations of IP(3) were quantal and IP(3)-evoked Ca(2+) release was biphasically regulated by cytosolic Ca(2+). Using rapid superfusion to examine the kinetics of IP(3)-evoked Ca(2+) release from S2 cells, we established that IP(3) (10 microM) maximally activated Drosophila IP(3) receptors within 400 ms. The activity of the receptors then slowly decayed (t(1/2)=2.03+/-0.07 s) to a stable state which had 47+/-1% of the activity of the maximally active state. We conclude that the single subtype of IP(3) receptor expressed in Drosophila has similar functional properties to mammalian IP(3) receptors and that analyses of IP(3) receptor function in this genetically tractable organism are therefore likely to contribute to understanding the roles of mammalian IP(3) receptors.

Rapid activation and partial inactivation of inositol trisphosphate receptors by adenophostin A.

Adenophostin A, the most potent known agonist of inositol 1,4, 5-trisphosphate (InsP(3)) receptors, stimulated (45)Ca(2+) release from the intracellular stores of permeabilized hepatocytes. The concentration of adenophostin A causing the half-maximal effect (EC(50)) was 7.1+/-0.5 nM, whereas the EC(50) for InsP(3) was 177+/-26 nM; both responses were positively co-operative. In rapid superfusion analyses of (45)Ca(2+) release from the intracellular stores of immobilized hepatocytes, maximal concentrations of adenophostin A or InsP(3) evoked indistinguishable patterns of Ca(2+) release. The Ca(2+) release evoked by both agonists peaked at the same maximal rate after about 375 ms and the activity of the receptors then decayed to a stable, partially (60%) inactivated state with a half-time (t(1/2)) of 318+/-29 ms for adenophostin A and 321+/-22 ms for InsP(3). Dissociation rates were measured by recording rates of InsP(3)-receptor channel closure after rapid removal of agonist. The rate of adenophostin A dissociation (t(1/2), 840+/-195 ms) was only 2-fold slower than that of InsP(3) (t(1/2), 436+/-48 ms). We conclude that slow dissociation of adenophostin A from InsP(3) receptors does not underlie either its high-affinity binding or the reported differences in the Ca(2+) signals evoked by InsP(3) and adenophostin A in intact cells.

Vacuolar chloride transport in Mesembryanthemum crystallinum L. measured using the fluorescent dye lucigenin.

To study vacuolar chloride (Cl(-)) transport in the halophilic plant Mesembryanthemum crystallinum L., Cl(-) uptake into isolated tonoplast vesicles was measured using the Cl(-)-sensitive fluorescent dye lucigenin (N,N'-dimethyl-9,9'-bisacridinium dinitrate). Lucigenin was used at excitation and emission wavelengths of 433 nm and 506 nm, respectively, and showed a high sensitivity towards Cl(-), with a Stern-Volmer constant of 173 m(-1) in standard assay buffer. While lucigenin fluorescence was strongly quenched by all halides, it was only weakly quenched, if at all, by other anions. However, the fluorescence intensity and Cl(-)-sensitivity of lucigenin was shown to be strongly affected by alkaline pH and was dependent on the conjugate base used as the buffering ion. Chloride transport into tonoplast vesicles of M. crystallinum loaded with 10 mm lucigenin showed saturation-type kinetics with an apparent K(m) of 17.2 mm and a V(max) of 4.8 mm min(-1). Vacuolar Cl(-) transport was not affected by sulfate, malate, or nitrate. In the presence of 250 microm p-chloromercuribenzene sulfonate, a known anion-transport inhibitor, vacuolar Cl(-) transport was actually significantly increased by 24%. To determine absolute fluxes of Cl(-) using this method, the average surface to volume ratio of the tonoplast vesicles was measured by electron microscopy to be 1.13 x 10(7) m(-1). After correcting for a 4.4-fold lower apparent Stern-Volmer constant for intravesicular lucigenin, a maximum rate of Cl(-) transport of 31 nmol m(-2) sec(-1) was calculated, in good agreement with values obtained for the plant vacuolar membrane using other techniques.

Characterisation of the voltage-activated calcium current in the marine ciliate Euplotes vannus.

We have isolated the early Ca current (ICa) from the whole cell current that activates upon depolarisations in the marine ciliate Euplotes vannus. The peak of ICa activated within 4.2 ms at depolarisations to 5 mV with an amplitude of 2.5 +/- 0.35 nA and was reduced to 1.0 +/- 0.14 nA (n = 5) when the extracellular Ca concentration was changed from 10 to 1 mM. The voltage-dependent activation curve was steeper and shifted to more negative values when external Ca2+ was replaced by Ba2+. The early inward current inactivated with a double-exponential time course including a fast and a slow component, and no inactivation was recorded with Ba2+. The time constants for the recovery from inactivation varied between 44 and 153 ms according to the depolarisation-dependent Ca influx. At the common resting potential of -25 mV, ICa was not steady-state inactivated; ICa half-inactivated at -14.5 mV, and totally inactivated at -5 mV. ICa was inhibited by 10 mM extracellular Cd2+. The peptides omega-conotoxin-GVIA (20 microM), omega-conotoxin-MVIIC (600 nM), omega-agatoxin-IVA (60 nM) and calciseptine (900 nM) did not block ICa. The benzothiazepine-derivative diltiazem (100 microM) and the dihydropiridine nifedipine (100 microM) inhibited 51% and 33% of ICa, respectively. The naphthalene sulfonamide W7 reduced ICa with an inhibition coefficient of 33 microM.

Cyanide production from glycine by a homogenate from a Pseudomonas species.

A cell-free preparation with cyanide-producing activity was obtained from a bacterium, strain C, of the genus Pseudomonas. To preserve activity, an oxidizing agent, e.g., phenazine methosulphage (PMS), had to be added to the cell suspension before disruption by sonic treatment. By the procedure described, a total homogenate made from a 15% (wet weight) bacterial suspension in tris(hydroxymethyl)aminomethane-hydrochloride buffer (0.05 M, pH 8.2) and with PMS (0.4mM) exhibited about 8% of the activity obtained from a suspension of untreated bacteria. In the presence of flavine-adenine dinucleotide (0.3 mM) and PMS (0.4mM), the activity was augmented to about 16% of that of the intact cells. By gradient centrifugation the homogenate was separated into three fractions. The main enzyme activity was associated with those fractions which by electron microscopy were found to consist of membranous structures.

Cyanide formation from oxidation of glycine of Pseudomonas species.

With whole cells of a hydrogen cyanide-producing bacterium strain C, of the genus Pseudomonas, it was found that the oxygen necessary for the oxidation of glycine to cyanide could be replaced by various artificial electron acceptors. The order of reactivity was: oxygen > phenazine methosulphate > methylene blue > 2,6-dichlorophenolindophenol > ferricyanide. Cyanide production was inhibited by pyrrolnitrin, a well-known inhibitor of many flavine enzymes. The molar ratio of added glycine to cyanide produced was found to be 1.09. With whole bacteria the apparent K(m) (glycine) for the cyanide production was found to be 5.0 x 10(-4) M.