Tilly Bakker-Grunwald

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(1) The occurrence of volume-regulatory responses in isolated rat hepatocytes was investigated. After hypotonic shock, cells were able to shrink back to their normal volume within 15 min. By contrast, after hypertonic shock cells kept their shrunken volume for at least 15 min. (2) Na+-alanine cotransport increases K+ permeability in rat hepatocytes(More)
The bumetanide-sensitive (K+ + Na+ + 2Cl-)-cotransport system in turkey erythrocytes is activated by either of two treatments: addition of epinephrine or an increase in osmolarity. At elevated (20 mM) K+ concentration, cotransport activity induced by epinephrine slowly (within 90 min) declines to background level again. This time-dependent inactivation has(More)
To screen for high molecular weight proteases in Entamoeba histolytica, we subjected a soluble amebal extract to density gradient centrifugation and tested the fractions for activity against the chymotryptic peptide substrate, Suc-leucyl-leucyl-valyl-tyrosyl-4-methylcoumaryl-7-amide. Two peaks of activity, of approximately 11 and 20 S, were clearly(More)
Many parasitic protozoa go through complex life cycles in the course of which they adapt to widely different environments; ion transport processes are expected to play a role both in pathogenicity and in adaptation. So far, studies on ion transport have been virtually limited to Leishmania, Plasmodium and Entamoeba. The distribution of ion pumps in the(More)
In turkey erythrocytes, the hormone-induced, diuretic-sensitive components of both unidirectional K+ influx and net salt uptake were Cl- dependent, with Br- partially able, and NO3(-) and SO42(-) unable to substitute as the main anion. Since the measured fluxes involve involve Na+/+ cotransport, these observations indicate that the unifying concept of an(More)
The movement of thallous ion (Tl+ across the ascites cell membrane has been characterized. Analogous to previous findings for86Rb+ (used as a tracer for K+),204Tl+-influx could be resolved into three components: a ouabain-inhibitable “pump” flux, a passive flux, and a furosemide- or NO 3 − -sensitive “exchange” flux. Although Tl+ moved approximately nine(More)
The amino acid sequence of ubiquitin from Entamoeba histolytica, as deduced from a cDNA nucleotide sequence, deviated at six positions from the consensus of all other known ubiquitins (ranging from Trypanosoma cruzi to Homo sapiens). The corresponding residues were scattered over the primary sequence, but came close together on the surface of the folded(More)
Pore-forming activity in planar lipid bilayers and liposomes of extracts from differentially pathogenic Entamoeba and the capacity of trophozoites and subcellular fractions to lyse human red blood cells (hrbc) were investigated. In all amebas studied, the two activities paralleled each other. They were high in E. histolytica irrespective of the virulence of(More)
Unidirectional potassium influx in simian virus-transformed 3T3 cells was dissected into a ouabain-inhibitable "pump' component, a bumetanide-sensitive and chloride-dependent "cotransport' component, and a residual "leak' flux. The bumetanide-sensitive component was stimulated 2-3-fold by a 60-min preincubation with ouabain. Subsequent washing of the cells(More)