scispace - formally typeset
Search or ask a question
Author

Donald F.H. Wallach

Bio: Donald F.H. Wallach is an academic researcher from Tufts Medical Center. The author has contributed to research in topics: Membrane & Membrane protein. The author has an hindex of 35, co-authored 83 publications receiving 2872 citations. Previous affiliations of Donald F.H. Wallach include University of California, San Diego & Max Planck Society.


Papers
More filters
Journal ArticleDOI
TL;DR: Results suggest that Ca2+ transport of intraerythrocytic parasites is coupled to a proton-motive force across the Plasmodia plasma membrane, suggesting that a DCCD- and CCCP-sensitive membrane potential in P. chabaudi-infected cells is suggested.
Abstract: The calcium content and transport processes of Plasmodium chabaudi-infected rat erythrocytes were analyzed by atomic absorption spectroscopy and 45Ca2+ flux measurements. Infected erythrocytes, after fractionation on metrizamide gradients according to stage of parasite development, exhibited progressively increasing levels of Ca2+ with schizont and gametocytes containing 10- to 20-fold greater calcium levels than normal cells (0.54 +/- 0.25 nmol/10(8) cells). 45Ca2+ flux experiments showed both increased influx and decreased efflux in infected erythrocytes. Tris/NH4Cl lysis of normal erythrocytes preloaded with 45Ca2+ with the Ca2+ ionophore A23187 released less than 90% of cell calcium after incubation in ethyleneglycol bis(aminoethylether) N,N'-tetraacetic acid containing buffer, whereas lysis of the infected erythrocyte membrane resulted in release of 10-20% cell Ca2+, with the remaining portion associated with the isolated parasite fraction. This information together with the effects of various metabolic inhibitors indicates the presence of a parasite Ca2+ compartment in P. chabaudi-infected erythrocytes. Dicyclohexylcarbodiimide (DCCD) an inhibitor of proton ATPases of chloroplasts, bacteria, yeast, and mitochondria, and the proton ionophore, carbonyl cyanide m-chlorophenylhydrazone (CCCP), inhibited Ca2+ influx and stimulated efflux from infected cells. These results combined with evidence for a DCCD- and CCCP-sensitive membrane potential in P. chabaudi-infected cells (Mikkelsen et al., accompanying manuscript) suggest that Ca2+ transport of intraerythrocytic parasites is coupled to a proton-motive force across the Plasmodia plasma membrane.

117 citations


Cited by
More filters
Journal ArticleDOI
TL;DR: A review of the use of the technique of solute fluorescence quenching to study the structure and dynamics of proteins and a number of factors are discussed that must be considered in analyzing such data.

1,644 citations

Journal ArticleDOI
09 Nov 1979-Science
TL;DR: Viability, as determined by trypan blue exclusion correlated well with other indices of viability such as plating efficiency and the hydrolysis of fluorescein diacetate, and it is concluded that the cells are killed by processes that involve at least two steps.
Abstract: Primary cultures of adult rat hepatocytes were treated in the presence or absence of extracellular calcium with ten different membrane-active toxins. In all cases more than half the cells were killed in 1 to 6 hours in the presence but not in the absence of extracellular calcium. An effect of calcium on the primary mechanism of membrane injury by any of the agents cannot be implicated. Viability, as determined by trypan blue exclusion correlated well with other indices of viability such as plating efficiency and the hydrolysis of fluorescein diacetate. It is concluded that the cells are killed by processes that involve at least two steps. In each type of injury, disruption of the integrity of the plasma membrane by widely differing mechanisms is followed by a common functional consequence involving extracellular calcium, and most likely representing an influx of calcium across the damaged plasma membrane and down a steep concentration gradient. This later step represents, or at least initiates, a final common pathway for the toxic death of these cells.

1,459 citations

Journal ArticleDOI
TL;DR: This article will focus on the localization and modes of association of individual major polypeptides within the human red cell membrane.
Abstract: The elucidation of the molecular architecture of cell membranes is a central goal for cell biology, as structure lies at the heart of function. The erythrocyte plasma membrane has long provided a favored testing ground for this inquiry. Human red blood cells are readily available, relatively homogeneous, and relevant to medicine. Their plasma membranes can be easily isolated intact and essentially free of contamination from other cells, organelles, and cytoplasmic contents. This membrane is complex enough to be interesting and, to some degree, representative, yet it is simple enough to be analyzed as a whole. These circumstances make it likely that the human red cell plasma membrane will be the first whose molecular anatomy is known in any degree of satisfying detail. The literature concerning the proteins of erythrocyte membranes and membranes in general has been the subject of repeated review (1 9). This article will focus on the localization and modes of association of individual major polypeptides within the human red cell membrane.

1,452 citations

Journal ArticleDOI
17 Feb 1984-Science
TL;DR: Results obtained with infrared spectroscopy indicate that trehalose and DPPC interact by hydrogen bonding between the OH groups in the carbohydrate and the polar head groups of DPPC, and this interaction is specific totrehalose.
Abstract: Trehalose is a nonreducing disaccharide of glucose commonly found at high concentrations in anhydrobiotic organisms. In the presence of trehalose, dry dipalmitoyl phosphatidylcholine (DPPC) had a transition temperature similar to that of the fully hydrated lipid, whereas DPPC dried without trehalose had a transition temperature about 30 degrees Kelvin higher. Results obtained with infrared spectroscopy indicate that trehalose and DPPC interact by hydrogen bonding between the OH groups in the carbohydrate and the polar head groups of DPPC. These and previous results show that this hydrogen bonding alters the spacing of the polar head groups and may thereby decrease van der Waals interactions in the hydrocarbon chains of the DPPC. This interaction between trehalose and DPPC is specific to trehalose. Hence this specificity may be an important factor in the ability of this molecule to stabilize dry membranes in anhydrobiotic organisms.

1,396 citations