High-performance liquid chromatographic methods for the determination of a new carbapenem antibiotic, L-749,345, in human plasma and urine

A column-switching, reversed-phase high-performance liquid chromatographic (HPLC) method for the determination of a new carbapenem antibiotic assay using ultraviolet detection has been developed for a new carbapenem antibiotic L-749,345 in human plasma and urine. A plasma sample is centrifuged and then injected onto an extraction column using 25 mM phosphate buffer, pH 6.5. After 3 min, using a column-switching valve, the analyte is back-flushed with 10.5% methanol–phosphate buffer for 3 min onto a Hypersil 5 μm C₁₈ BDS 100×4.6 mm analytical column and then detected by absorbance at 300 nm. The sample preparation and HPLC conditions for the urine assay are similar, except for a longer analytical column 150×4.6 mm. The plasma assay is specific and linear from 0.125 to 50 μg/ml; the urine assay is linear from 1.25 to 100 μg/ml.     

The role of Eh, pH and iron in the bactericidal power of human plasma

The bactericidal power of fresh human plasma against Klebsiella pneumoniae and Escherichia coli was extremely sensitive to changes in Eh and pH. At a high Eh (approx. +200 mV) the bacteria were destroyed, but rapid regrowth occurred when the Eh was lowered to approx. -400 mV. Abolition of the bactericidal effect was also produced by adding ferric iron at a high Eh (approx. +200 mV). Lowering the pH to 6.50 reduced or prevented the bactericidal effect. These results are probably related to the availability of iron for bacterial growth, and could be important for understanding the development of infection in injured or diseased tissue.     

Ethidium bromide inhibits mitochondrial phosphorylating oxidation.

Ethidium bromide, in addition to combination with mitochondrial nucleic acids, is a phosphorylation inhibitor during glutamate and succinate respiration by mitochondria. Exhaustive washing of ethidium bromide-treated mitochondria did not relieve the inhibition nor significantly decrease the amount of bound dye. Dialysis against a cation exchange resin at 3 degrees for 17 hr removed about 97% of bound dye. This restored phosphorylating capacity to that of untreated mitochondria which had also been dialyzed against the resin. Since state 3 respiration was diminished and state 4 was unaffected by the presence of the acridine dye, and since neither swelling of mitochondria nor release of latent ATPase was observed, then ethidium bromide was not an electron transport inhibitor nor an uncoupler of oxidative phosphorylation. Inhibition of metabolic processes by ethidium bromide may be due in part to depressed generation of mitochondrial ATP.     

Partitioning of mercury in aqueous biphasic systems and on ABEC™ resins

Poly(ethylene glycol)-based aqueous biphasic systems (PEG-ABS) can be utilized to separate and recover metal ions in environmental and hydrometallurgical applications. A concurrent study was conducted comparing the partitioning of mercury between aqueous layers in an ABS [Me-PEG-5000/(NH₄)₂SO₄] and partitioning of mercury from aqueous solutions to aqueous biphasic extraction chromatographic (ABEC-5000) resins. In ammonium sulfate solutions, mercury partitions to the salt-rich phase in ABS, but by using halide ion extractants, mercury will partition to the PEG-rich phase after formation of a chloro, bromo or iodo complex. The efficacy of the extractant increases in the order Cl⁻<Br⁻<I⁻. This behavior is also observed using the ABEC resins where halo complexes of mercury will adsorb to the resin from (NH₄)₂SO₄ solutions with retention following the same order. The onset of mercury extraction or adsorption is different for the three extractants, occurring at the lowest extractant concentration for I⁻, followed by Br⁻, and then Cl⁻. Fluoride does not extract mercury. Extraction or adsorption of mercury is improved at the lowest halide concentrations in the presence of sulfuric acid. The addition of sulfuric acid to (NH₄)₂SO₄ solution results in ABEC retention of mercury even in the absence of halide extractant.     

The distribution of centrosomes in endothelial cells of non-wounded and wounded aortic organ cultures

Summary The distribution of centrosomes in porcine vascular endothelial cells of the thoracic aorta maintained in organ culture was determined in en face preparations using immunofluorescence. Rectangular pieces of aorta that had the distal half (with respect to the heart) of their endothelial surface gently denuded with a scalpel blade and pieces with intact endothelium were cultured for up to 96 h. At time 0, centrosomes were found to be preferentially oriented toward the heart, both in the cells of intact monolayers and in cells at the wound edge. This distribution was maintained in the intact monolayers for at least 24 h, but by 72 h the number of centrosomes in the center of the cells exceeded the number oriented toward the heart as the cells changed from a fusiform to a polygonal shape. The centrosomes of most endothelial cells at the wound edge began to redistribute themselves within the first 24 h in culture, moving from a position toward the heart to a position either in the center of the cell or away from the heart. By 72 h, the majority of centrosomes in endothelial cells at the wound edge were oriented away from the heart toward the denuded region. It is concluded that the centrosomes in the endothelial cells maintained in organ culture respond to injury in a manner similar to those grown in monolayer cell culture except that the reorientation of centrosomes occurs more slowly.