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Biomedical subjects

E E Uzgiris

Publications and source records attributed to E E Uzgiris.

At least 19 recordsLinked to original sources
PubMed1998

Gadolinium determination in tissue samples by inductively coupled plasma mass spectrometry and inductively coupled plasma atomic emission spectrometry in evaluation of the action of magnetic resonance imaging contrast agents.

The quantitative determination of Gd-containing magnetic resonance imaging (MRI) contrast agents in animal tissues is performed by both ICP-AES and ICP-MS. While ICP-AES has been used to determine Gd-containing contrast agents by other workers, no published methodology has been found. An accurate and precise method using nitric acid and microwave digestion for sample preparation is described. Dosed rat tissue, blood and plasma were measured by both ICP-AES and ICP-MS. The ICP-AES method is excellent for screening Gd levels and quantitative determination of concentrations above 400 ng ml-1, but it lacks the sensitivity to measure agent concentrations in low dose MRI studies. This work demonstrates that ICP-MS has the needed sensitivity to replace radiotracer methods currently used for low dose studies, while maintaining the accuracy and precision of results obtained by ICP-AES. Gadolinium detection limits in tissue were 0.04 mumol of Gd per kg of tissue, an order of magnitude lower than studies using radiotracer techniques.

Animals↗
PubMed1995

Methane-induced haemolysis of human erythrocytes.

Human erythrocytes were exposed to high concentrations of methane and nitrogen through the application of elevated partial pressures of these gas molecules. Cell leakage (haemolysis) was measured for cells exposed to these gases under a wide range of experimental conditions. Application of methane produces haemolysis at pressures far below the hydrostatic pressures known to disrupt membrane or protein structure. The effects of changes in buffer, temperature, diffusion rate and detergents were studied. Methane acts co-operatively with detergents to produce haemolysis at much lower detergent concentration than is required in the absence of methane or in the presence of nitrogen. At sufficiently high concentrations of methane, all cells are haemolysed. Increased temperature enhances the effect. Methane produces 50% haemolysis at a concentration of about 0.33 M compared with about 7.5 M methanol required for the same degree of haemolysis.

Buffers↗
PubMed1995

Tumor imaging with a macromolecular paramagnetic contrast agent: gadopentetate dimeglumine-polylysine.

RATIONALE AND OBJECTIVES: We evaluated magnetic resonance (MR) contrast enhancement of tumor tissue following injection of the macromolecular conjugate, gadopentetate dimeglumine-polylysine. METHODS: T1-weighted MR imaging scans were performed on female Fisher-344 rats with subcutaneously implanted mammary adenocarcinoma tumors. Following the baseline scan, gadopentetate dimeglumine-polylysine or gadopentetate dimeglumine was injected at a dose of 0.1 mmol gadolinium per kilogram. RESULTS: Gadopentetate dimeglumine-polylysine injection resulted in a maximum enhancement of tumor contrast of 310 +/- 60% (n = 7). Tumor tissue remained enhanced and well defined for several days after gadopentetate dimeglumine-polylysine injection. Gadopentetate dimeglumine injection at the same dose resulted in a 70 +/- 25% (n = 4) maximal tumor enhancement and a corresponding 25 +/- 4% muscle enhancement. CONCLUSION: Gadopentetate dimeglumine-polylysine provides higher, more sustained tumor contrast than does gadopentetate dimeglumine for the same dosage of gadolinium.

Adenocarcinoma↗
PubMed1990

Antibody organization on lipid films. Influence of pH and interchain disulphide reduction.

Two distinct lattice structures are observed for two-dimensional (2-D) antibody organization on phospholipid films. A low-order, small-unit-cell, square lattice is obtained at pH 7 and below for mouse IgE, mouse IgG2a and IgG2b and rabbit IgG. At pH 7.5 and above, the observed lattice structure switches to a large-unit-cell, hexagonal type for rabbit IgG and mouse IgE. Interchain disulphide reduction by exposure to 2 mM-dithiothreitol results in the formation of the compact 2-D lattice for all cases and for all pH conditions.

Animals↗
PubMed1987

UV immobilized phospholipid bilayers.

Dinitrophenyl phosphotidylethanolamine-containing bilayers have been immobilized on carbon-shadowed support films by UV irradiation of the first monolayer transferred to the support film. The immobilized bilayer is capable of allowing bound protein (anti-DNP antibody) to organize into 2-D arrays in the presence of organic solvents such as acetonitrile and dilute concentrations of detergents such as beta-octyl glucoside. The ability of the bilayers to remain attached to supports under various conditions that include organic solvents and detergents as well as divalent ions is of potential interest in the study of protein crystallization and particularly in the study of membrane proteins.

Dinitrophenols↗
PubMed1987

Self-organization of IgE immunoglobulins on phospholipid films.

Mouse monoclonal IgE anti-2,6-dinitrophenyl antibody (clone SPE-7) crystallizes in two dimensions when bound to a phospholipid monolayer or bilayer that has been combined with the hapten 2,6-dinitrophenyl groups. The two-dimensional lattice exhibits considerable local disorder, but long-range order is maintained over many unit cells of the lattice. The crystallization of IgE on the films is sensitive to IgE concentration in bulk solution. The optimum appears to be in the range 100-200 micrograms/ml. The crystallization tendency is diminished at pH lower than pH 6.5, and the crystals 'melt out' at a rather low temperature; no crystals were observed for 37 degrees C and above. The crystal growth rate is very much lower than was observed for monoclonal IgG1 anti-2,6-dinitrophenyl antibody. Finally, the IgE lattice is very different from the two-dimensional lattice formed by IgG1: the hexagonal lattice unit cell is smaller and has an open structure.

Crystallization↗
PubMed1986

Supported phospholipid bilayers for two-dimensional protein crystallization.

Phospholipid bilayers, supported on UV irradiated carbon shadowed nitrocellulose electron microscope grids, have been used to induce two-dimensional crystal growth of IgE and IgG anti-DNP monoclonal antibodies. The UV irradiation renders the grids hydrophilic in a very uniform fashion and allows for the transfer of phospholipid monolayers from an air/water interface in a sequential dipping procedure. The surface coverage achieved was nearly 100% as measured by antibody binding and by the formation of protein arrays on the bilayer covered grids. The supported bilayers appear to be stably held and are appropriate for slow binding conditions and long incubation times with low concentrations of binding protein.

Animals↗
PubMed1985

Antibody crystallization on phospholipid films: dynamics and the effects of antibody conformation.

Monoclonal antibodies from two-dimensional (2-D) crystals when bound to haptenated phospholipid monolayers in physiological conditions and at ambient temperatures. IgG1 forms two crystal phases: a linear strand phase and a high-order hexagonal phase. The relative distribution of these two phases is dependent on temperature, pH, and salt concentration. This dependence is one that is associated with protein intramolecular interactions rather than lipid-lipid or lipid-protein interactions for a number of reasons: 1) Polyclonal antibodies against the hapten DNP do not organize into any crystal structure for any of the experimental conditions used. 2) Slightly denatured IgG (through storage at 4 degrees C, for example) does not readily crystallize and a shift in the temperature dependence for forming the hexagonal phase is observed. 3) There is no pH driven transition in crystallization tendency for IgE anti-DNP but a transition to disorder is observed at above 30 degrees C. No such transition exists for IgG1. Observation of the dynamics of crystal growth shows a clear and marked dependence on pH and temperature that is in accord with the results of long-term incubations. It is found that high pH retards crystal growth very significantly for IgG1 but not for IgE. Also, the crystal growth rate of 4 degrees C-stored IgG1 is greatly reduced over fresh IgG1 (-80 degrees C stored). Furthermore, it is found that the linear phase of IgG1 is an extremely rapidly forming phase but one that is metastable against the hexagonal phase.

Animals↗
PubMed1984

Laser photobleaching of human serum: application to fluorescence immunoassays.

Background fluorescence from serum chromophores is substantially reduced by a laser photobleaching method. Human and bovine serum samples were illuminated with 337-nm light from a pulsed N2 laser for a short period of time. The serum emission in the region of 440 to 550 nm was reduced by an order of magnitude with no evident damage to serum proteins as judged by the unchanged activity of alkaline phosphatase and aspartate aminotransferase.

Alkaline Phosphatase↗
PubMed1983

Two-dimensional crystallization technique for imaging macromolecules, with application to antigen--antibody--complement complexes.

Two-dimensional crystals are formed from macromolecules bound on the surface of a lipid monolayer. A ligand linked to the lipid orientates the binding, and lateral diffusion of the lipids facilitates crystallization. The crystals are suitable for structural analysis by image processing of electron micrographs. An example is the formation of ordered arrays of antibodies on a monolayer of a lipid hapten, and subsequent decoration of these arrays with the first component of complement. Image processing indicates the arrangement of antibodies and the site of complement binding. This approach should be widely applicable to molecular complexes, such as those in replication, protein synthesis, hormone-receptor interaction and metabolic processes.

Antigen-Antibody Complex↗
PubMed1982

Oscillation of cell surface charge of human peripheral blood lymphocytes after stimulation with concanavalin A.

Lymphocytes isolated from human peripheral blood were incubated with concanavalin A (Con A), and relative changes in cell surface charge were monitored by measuring cell electrophoretic mobility. Kinetic studies showed a time lag of 2.5 hr between exposure to Con A and development of a significant change in cell surface charge. The possible involvement of de novo synthesis of a factor was suggested by the following observations: 1) addition of the protein synthesis inhibitor, puromycin, abrogated the change in electrophoretic mobility; 2) supernatants obtained from cells incubated with Con A caused a mobility change in a separate group of lymphocytes not previously incubated with this mitogen; 3) supernatants obtained from cell suspensions treated with puromycin were inactive. The mobility response showed an oscillation of membrane charge ranging from a 1- to 1.5-hr period, which eventually disappeared after 8 hr at 37 degrees C. Cells at the minimum of the mobility oscillation were refractory to addition of active supernatants. This suggests the involvement at the lymphocyte surface of some cyclic metabolic process, or perhaps formation of receptor-factor complexes followed by endocytosis of these complexes with subsequent regeneration of the receptors on the cell surface.

Cell Membrane↗
PubMed1981

Activation of human lymphocytes by concanavalin A or purified protein derivative results in no alteration of fluorescence polarization of lipid probes although the electrophoretic mobility of the cells is changed.

Upon stimulation with either concanavalin A or the tuberculin antigen, purified protein derivative, human peripheral blood lymphocytes, purified on Ficoll-Hypaque, did not exhibit a concomitant lipid fluidity alteration as measured by fluorescence polarization (P) of the lipid probe, 1,6-diphenyl-1,3-5-hexatriene (DPH). This result was independent of the incubation period, ranging from 10 min to 72 h. However, a general reduction in polarization value, from P = 0.287 (maintained for up to 2 h of incubation) to P = 0.225 after 20 h was observed for both experimental and control samples. Moreover, fluorescence polarization studies of the nonpenetrating modified DPH cationic lipid probe, 1-[4'-trimethylaminophenyl]-6-phenyl-1,3-5-hexatriene (TMA-DPH), also failed to show any change in lipid fluidity subsequent to a 1-3 h incubation of lymphocytes with concanavalin A. Cell electrophoretic mobility, however, was altered (mean cell mobility increased by 10-15%) in a fast response to stimulation and was observed within several hours of in vitro application of concanavalin A and purified protein derivative. This initial response disappeared with further incubation at 37 degrees C (greater than 3 h) and was followed by a decline of cellular mobility of the concanavalin A-exposed cells after 48 and 72 h of incubation. The unstimulated control cells did not change in mobility as a function of incubation time. The slow decline in mean cell mobility of the experimental cells is believed to be associated with blastogenesis. It is concluded that neither blastogenic transformation nor short term membrane alterations associated with human lymphocyte activation lead to lipid fluidity changes as measured in steady state by the fluorescence polarization of both DPH and TMA-DPH.

Antigens, Bacterial↗