Interaction of technetium 99m-labeled teboroxime with red blood cells reduces the compound's extraction and increases apparent cardiac washout

BACKGROUND: 99mTc-labeled teboroxime shows high myocardial extraction in both in vivo animal and in vitro cell culture and isolated heart studies. Whereas in vivo studies show rapid myocardial clearance of teboroxime, in vitro cell culture and isolated heart studies show slower washout comparable to that of 201Tl. Binding of teboroxime to blood components may contribute to these conflicting results. METHODS AND RESULTS: We measured teboroxime extraction in the isolated blood-perfused rabbit heart after injection in saline solution, brief incubation in red blood cell perfusate, or 4-hour incubation with human red blood cells. Teboroxime in saline solution showed high extraction (Emax = 0.89 +/- 0.02; Enet = 0.69 +/- 0.02), whereas brief incubation in perfusate (Emax = 0.60 +/- 0.06; Enet = 0.48 +/- 0.05) or prolonged incubation with human red blood cells (Emax = 0.43 +/- 0.09; Enet = 0.38 +/- 0.07) resulted in reduced extraction. Teboroxime clearance was similar for all groups and was slower than 201Tl clearance. Analysis of total residual cardiac teboroxime (comparable to external imaging) showed that teboroxime clearance was biexponential. Reduced extraction of teboroxime in red blood cells resulted in an increased size of the rapidly clearing (unextracted) fraction, giving the appearance of rapid myocardial washout. CONCLUSIONS: Teboroxime has a high myocardial extraction. Binding to blood components reduces teboroxime extraction and increases the rate of cardiac teboroxime clearance.     

Steroid hormone regulation of cytokine secretion by proteolipid protein-specific CD4+ T cell clones isolated from multiple sclerosis patients and normal control subjects

Steroid hormones have long been known to modulate immune function, and recent studies indicate that one of the means by which they do so involves effects on the secretion of immunoregulatory cytokines. Our laboratory has found recently that estradiol (E2) selectively modifies cytokine secretion in proteolipid protein (PLP)-specific, CD4+ T cell clones isolated from patients with the demyelinating disease, multiple sclerosis, and from normal control subjects. The data suggest that E2 may play a role in regulating the balance between pro- and antiinflammatory conditions, especially at concentrations typical of pregnancy. To determine whether other pregnancy-associated steroid hormones are capable of similar activity, we expanded our testing to include estrone (E1), estriol (E3), progesterone, and dexamethasone. The results indicate that E1 and E3 enhance secretion of Ag- or anti-CD3-stimulated IL-10 and IFN-gamma in dose-dependent fashion, almost identical to that of E2. The effect on IL-10 was more potent than occurred with IFN-gamma. In addition, E1 and E3, like E2, had a biphasic effect on TNF-alphabeta secretion, with low concentrations stimulatory, and high doses inhibitory. None of the estrogens influenced IL-4 or TGF-beta secretion. Progesterone enhanced secretion of IL-4, without affecting any other tested cytokine. Finally, dexamethasone induced TGF-beta secretion, but inhibited IFN-gamma and TNF-alphabeta. This differential effect of steroid hormones on the secretion of cytokines by CD4+ human T cell clones is consistent with the possibility that, collectively, they promote antiinflammatory conditions at high concentrations typical of pregnancy.     

Electromagnetic scattering by an inhomogeneous penetrable material with an embedded resistive sheet

This paper presents the method of moments (mom) formulation for the electromagnetic scattering by an inhomogeneous penetrable material with an embedded resistive sheet. Triangular surface facets and tetrahedral volume cells are used to discretize the scatterer allowing for greater flexibility in the geometric modeling of the material body. The formulation is very general in that it allows for a variety of material configurations : open or closed conducting surfaces, open or closed resistive (thin dielectric) surfaces, solid dielectric/ferrite material volumes, embedded conducting/resistive surfaces in material volumes, and partially embedded conducting/resistive surfaces (cladded materials). Results for a material coated resistive spherical shell and a material propeller blade are presented.     

Molecular epidemiology of Staphylococcus aureus and Enterococcus faecalis in endophthalmitis

Genomic DNA fingerprint analysis was performed on 39 Staphylococcus aureus and 28 Enterococcus faecalis endophthalmitis isolates collected from multiple clinical centers. Among 21 S. aureus genomic DNA fingerprint patterns identified, five clonotypes were recovered from multiple unrelated patients and accounted for 58.9% (23 of 39) of the isolates analyzed. Compared with strains having unique genomic DNA fingerprint patterns, the S. aureus clonotypes occurring more than once were more likely to result in visual acuities of 20/200 or worse (P = 0.036 [chi2 test]). In contrast to the S. aureus isolates, the E. faecalis endophthalmitis isolates were a clonally diverse population, enriched for the expression of a known toxin, cytolysin, which is plasmid encoded.     

Molecular mechanisms for focal adhesion assembly through regulation of protein-protein interactions

Focal adhesions provide a useful model for studying cell/extracellular matrix interactions and the subsequent cytoskeletal reorganization. Recent advances have suggested potential mechanisms by which cells may regulate focal adhesion assembly following integrin-mediated cell adhesion.     

Materials science progress and challenges in superconductors

Some of the accomplishments and problems remaining for the fabrication of superconductors into useful configurations are discussed. The high current densities that will be needed in many applications have only been achieved in epitaxial thin films grown on oxides of SrTiO₃ and MgO. It is very difficult to grow superconductors with a high current density on other insulators, semiconductors or metals. It will be necessary for us to do this in order to integrate superconductors into microelectronic circuits. The critical current density J_c in sintered polycrystalline bulk Y-Ba-Cu-O is very low, and considerable work is needed to eliminate defects at the grain boundaries before a significant improvement in J_c can be expected in sintered bulk solids. A significant improvement in J_c has been achieved in bulk materials with melt texturing. Ribbon-type wires have been produced which have a moderate J_c. In general, however, we are just beginning to learn to fabricate the new high T_c materials into the configurations that will be necessary for commercial applications.