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D F Wallach

Publications and source records attributed to D F Wallach.

At least 55 records · Page 3Linked to original sources
PubMed1979

Fractionation of Plasmodium knowlesi-induced antigens of rhesus monkey erythrocyte membranes.

In order to characterize parasite-induced host cell membrane antigens, the plasma membranes of Plasmodium knowlesi-infected rhesus erythrocytes have been compared with those of normal red cells and purified schizonts by immunochemical and biochemical techniques. Host cell membranes and schizonts were separated by differential centrifugation following nitrogen decompression. Isolated schizonts were further fractionated into several subcellular compartments. Crossed-immune electrophoresis, against monkey anti-schizont serum, of Triton X-100-solubilized material identified 7 P. knowlesi-specific antigens, of which 4 could be detected only in the host cell membranes. These membranes also contained 3 proteins, with relative molecular masses of 55 000, 65 000 and 90 000 and isoelectric points at pH 4.5, 4.5 and 5.2, respectively, which are lacking in normal membranes. Pulse-chase experiments with ((14)C)-glucosamine showed that these parasite-induced host cell membrane components are glycoproteins.

Animals↗
PubMed1978

Plasmodium knowlesi-induced antigens in membranes of parasitized rhesus monkey erythrocytes.

Highly purified Plasmodium knowlesi schizonts were used to produce a hyperimmune anti-parasite serum in a rhesus monkey. Proteins of membranes from normal and P. knowlesi-infected erythrocytes, as well as purified schizonts, were solubilized in 1% Triton X-100 and analyzed by bidimensional electrophoretic techniques. Of seven parasite-specific antigens identified in membranes of parasitized erythrocytes by crossed immune electrophoresis against monkey anti-parasite serum, only three could be detected in the purified schizonts. Bidimensional focusing-dodecyl sulfate/polyacrylamide gel electrophoresis of membranes from parasitized cells revealed three proteins, in the 55,000-90,000 molecular weight region, with isoelectric points between pH 4.5 and pH 5.2, that could not be detected in normal membranes or purified schizonts. Membranes of normal erythrocytes and uninfected erythrocytes that had been incubated with sera from monkeys with 25-50% parasitemia did not react with the monkey anti-parasite serum.

Animals↗
PubMed1978

Effect of transmembrane ion gradients on Raman spectra of sealed, hemoglobin-free erythrocyte membrane vesicles.

Sealed hemoglobin-free erythrocyte vesicles have been isolated. Imposition of transmembrane cation gradients increases the intensity of Raman scattering in the CH3-stretching region as observed with unsealed ghosts at temperatures greater than 38 degrees C and pH less than 7.0 [Verma, S. P. & Wallach, D. F. H. (1976) Proc. Natl. Acad. Sci. USA 73, 3358--3561]. Modifications in the amide I and amide III frequencies consistent with increased helicity of membrane proteins are observed upon imposition of a cation gradient. Spectrin-free vesicles also demonstrate cation gradient-sensitive intensity changes in the CH3-stretching region. However, no evidence for cation gradient-related protein conformation changes is found with these vesicles. The transmembrane potential of these vesicles has been altered by variations in anion composition and the electrogenic activity of Na+,K+-ATPase. The membrane potential was monitored by cyanine dye fluorescence. Imposition of a membrane potential (negative inside) also increased the intensity of Raman scattering in the CH3-stretching region. These results suggest that a transmembrane potential (negative inside) and/or cation gradient can energize membranes by compression of the apolar region and transfer of protein methyl residues into polar regions.

Erythrocyte Membrane↗
PubMed1978

Modification of rat thymocyte membrane properties by hyperthermia and ionizing radiation.

Thymocytes are one the most widely used cell models for the study of radiation-induced interphase death. This cell-type was chosen for the study of hyperthermic and radiation effects on two membrane-related processes implicated in the interphase death of cells: Na+-dependent 2-aminoisobutyric acid (AIB) transport and cyclic 3'-5' adenosine monophsophate formation. The response of AIB transport to heat is dose-dependent, but the biphasic thermal response curve (AIB uptake versus time) differs fom the sigmoidal radiation response curve. Heating thymocytes for 20-30 min at 43 degrees C stimulates AIB uptake. Additional heating at 43 degrees C, however, markedly reduces AIB uptake. Despite the immediate stimulating effect of heat (30 min at 43 degrees C), the thymocyte has already developed irrepairable impairments, as demonstrated by the fractionated heating experiments. The heat-induced impairment of AIB uptake is mainly on the Na+-dependent component of neutral amino-acid transport, affecting primarily the maximal rate of uptake, i.e. Vmax. Additional evidence for heat-induced plasma membrane damage is the alteration in cAMP levels. Heating thymocytes for 30 min or longer at 43 degrees C causes a massive rise in cAMP level within the cell. This differs from thymocytes exposed to radiation where no rise in cAMP is observed.

Aminoisobutyric Acids↗
PubMed1978

Impairment of Na+-dependent amino acid transport in a cultured human T-cell line by hyperthermia and irradiation.

We have examined the effects of hyperthermia and radiation on the ability of a human T-leukemic lymphocyte line (Molt-4) to transport the Na+-dependent amino acid, 2-aminoisobutyrate (AIB). Heating Molt-4 at 43 degrees for 1 to 4 hr damages the ability of these cells to accumulate AIB. The damage to the transport system at 43 degrees impairs only the maximal rate of AIB uptake, i.e., Vmax. The thermal effect on AIB transport parallels the radiation effects observed for this system. Preliminary data indicate that heat and radiation may induce irreversible transitions in the tertiary or quaternary structure of a plasma membrane protein involved in regulating Na+-dependent amino acid transport. However, the mechanism by which heat and radiation damage this protein is different.

Aminoisobutyric Acids↗
PubMed1977

Raman spectra of some saturated, unsaturated and deuterated C18 fatty acids in the HCH-deformation and CH-stretching regions.

We have analyzed the Raman spectra of stearic acid and two deuterated derivatives thereof, 2,2-dideutero stearic acid and 18,18,18-trideutero stearic acid, as well as of four unsaturated, C18 acids, (cis,-9; cis, cis-9,12, cis, cis, cis-9,12,15; and trans, trans-9,12) in their solid and liquid states. The different spectra of stearic acid and the two deuterated derivatives exhibit distinctive HCH-deformation and CH-stretching features for CH2 residues adjacent to CO2H or CH3 residues. Unsaturated hydrocarbon chains reveal additional features attributed to CH2 residues adjacent to one or two HC=CH groups. The spectra of the various fatty acids in their solic or liquid states show that both the HCH-deformation and CH-stretching regions are very sensitive to chain architecture, the CH-stretching region most dramatically so. Evaluation of the spectral features in the two regions indicates that the detailed structure of the CH-stretching region depends strongly upon interaction, enhanced by Fermiresonance, between CH-stretching fundamentals and HCH-deformation overtones. The data further suggest that the differences between HCH-deformation, in the solid and liquid states, and the resulting altered interactions between CH-stretching fundamentals and HCH-deformation overtones, produce the large modifications of the CH-stretching region that accompany solid-liquid transitions. The results thus provide a basis for the changes in the CH-stretching region, that accompany order-disorder transitions in model and biological membranes.

Deuterium↗
PubMed1977

Temperature sensitivity of the erythrocyte membrane potential as determined by cyanine dye fluorescence.

We have used the cyanine dye fluorescence technique to measure the membrane potential of human erythrocytes as a function of temperature. With erythrocytes starved of glucose, there is an abrupt decrease in membrane potential centered at 38 degrees which is reversible up to 41 degrees, and irreversible at higher temperatures. With erythrocytes supplemented with glucose, the thermally induced transition is centered at 41 degrees and is reversible up to the highest temperature measured, 45 degrees. These results extend previous spectroscopic studies with erythrocyte membranes which demonstrated a thermally induced transition in protein tertiary or quaternary structure that is irreversible above 42 degrees.

Diffusion↗
PubMed1977

Periodate induced cross-linking of concanavalin A-reactive membrane proteins of rabbit thymocytes.

Purified plasma membranes of rabbit thymocytes are exposed to sodium periodate and galactose oxidase at conditions similar to those used to induce mitogenic transformation of lymphocytes. The membrane proteins are then fractionated by dodecyl sulfate poly-acrylamide gel electrophoresis. At concentrations of 0.005 M, Na IO4 cross-links 55,000 D and 110,000 D glycoproteins which are known to specifically bind concanavalin A. Galactose oxidase has a similar cross-linking effect, but, at the same time causes proteolytic degradation of membrane proteins. Our data indicate that oxidizing agents, like NaIO4 and galactose oxidase, can indeed cross-link receptors of the thymocyte plasma membrane as has often been proposed as a possible mechanism of their action.

Animals↗