Oxygen-sensitive contrast in blood for steady-state free precession imaging.

Steady-state free precession (SSFP) methods have gained widespread recognition for their ability to provide fast scans at high signal-to-noise ratio. This paper demonstrates that such methods are also capable of reflecting functional information, particularly blood oxygenation state. It is well known that SSFP signals show substantial sensitivity to small off-resonance frequency variations. However, that mechanism cannot explain the oxygen-sensitive contrast in blood that was observed with steady-state methods using phase-cycled radiofrequency pulses. From theoretical and experimental models it is demonstrated that the mechanism responsible for such contrast originates from the motion of spins through local field inhomogeneities in and around deoxygenated red blood cells. In addition, this work shows that it is critical to choose the scan parameters carefully for robust oxygen-sensitive contrast. Finally, it is demonstrated that it is possible to build a quantitative model that incorporates the Luz-Meiboom model, which had been used in the past to estimate quantitative measures of vascular blood oxygen levels. It is envisioned that this method could be instrumental in real-time imaging focused on detecting diseases where the oxygen state of blood is impaired.     

The pharmacokinetic and bactericidal characteristics of oral cefixime

The pharmacokinetics of cefixime (FK 027), a broad-spectrum cephalosporin, were assessed in 12 normal subjects after single oral doses of 50, 100, 200, and 400 mg. Mean peak serum concentrations were 1.02, 1.46, 2.63, and 3.85 micrograms/ml after the four respective doses. Respective mean serum levels at 12 hours were 0.16, 0.33, 0.72, and 1.13 micrograms/ml. Volumes of distribution averaged 0.1 L/kg body weight, and the elimination t1/2 was 3 hours for all doses. The AUC was 7.01, 11.4, 22.5, and 36.4 micrograms X hr/ml for the four doses, respectively. Serum clearance averaged 0.4 mg/min/kg and mean 24-hour urinary recovery was 21%, 19%, 20%, and 16% for the four respective doses. Serum bactericidal titers at 4 hours exceeded 1:16 for Streptococcus pneumoniae, S. pyogenes, Hemophilus influenzae, and Branhamella catarrhalis. Urine bactericidal titers exceeded 1:8 for Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae resistant to the available oral cephalosporins.     

Coronary Angiography with Magnetization-Prepared T2 Contrast

A magnetization-prepared, T₂-weighted sequence (T₂ Prep) is used to suppress muscle and venous structures. When combined with lipid suppression, this technique improves the visualization of the coronary arteries. T₂ Prep was designed to be robust in the presence of flow as well as B₀ and B₁ inho-mogeneities and may be combined with virtually any imaging technique. Here, it is implemented with both a single-slice spiral acquisition and a multi-slice spiral method that acquires up to 15 slices in a single breath-holding interval.     

Substituted 9-benzyladenines: Inhibitors of inflammation associated with the delayed hypersensitivity skin reaction

Members of a group of substituted 9-benzyladenines have been identified as effective inhibitors of inflammatory aspects of the delayed hypersensitivity skin reaction in the guinea-pig. Inhibitory activity was demonstrable in the efferent arc of the cell-mediated tuberculin and contact dermatitis (2,4-dinitrochlorobenzene) reactions. One of the compounds, 2-amino-9-benzyladenine, inhibited both turpentine-induced and histamine-induced inflammation in the skin. The toxicity and inhibitory activities of some of these compounds are discussed, and reference is made to the structurally related mercaptopurines.