PubMed · 5475437
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
1970. Drug interaction.. https://doi.org/10.1093/bja%2F42.10.809
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Explore the source record for details and available documents.
This report describes experiments designed to assess and illustrate the effectiveness of a new method for the measurement of cerebral interstitial pO2 in conscious rodents. It is based on the use of low frequency electron paramagnetic resonance (EPR) spectroscopy with lithium phthalocyanine as the oxygen sensitive probe. Magnetic resonance imaging was used to document placement of the probe in the brain, and to assess potential cerebral changes associated with the placement. The technique provided accurate and reproducible measurements of localized pO2 in the brains of conscious rodents under a variety of physiological conditions and for time periods of at least 2 weeks. Using this approach we quantitated the depressing effects on cerebral pO2 of three representative anesthetics, isoflurane, ketamine/xylazine, and sodium pentobarbital. The effects of changing the content of oxygen in the breathing gas was investigated and found to change the cerebral pO2. In experiments with gerbils, crystals of lithium phthalocyanine were implanted in each side of the brain and using a one-dimensional magnetic field gradient, simultaneous measurement of pO2 values from normal and ischemic (ischemia induced by unilateral ligation of a carotid artery) hemispheres of the brain were obtained. These results demonstrate that EPR oximetry with lithium phthalocyanine is a versatile and useful method in the measurement of cerebral pO2 under various physiological and pathophysiological conditions.
The translational and rotational electrokinetics of the anesthetic-induced spectral transitions bR568-->bR480-->bR380 of bacteriorhodopsin have been investigated. Formation of the bR480 form is associated with an increase of the purple membrane negative electrokinetic charge, while the transformation of bR480 into bR380 is accompanied by a decrease of the membrane negative charge as compared to that of the 480 nm-absorbing form. Removal of anesthetics leads to the back transitions bR480-->bR568 and (in part) bR380-->bR568; however, the electrokinetic charge of the native membranes is not restored. A strong decrease in the electric polarizability and the appearance of a slow polarizability component are also observed in anesthetic-treated membranes. Comparison with the electrokinetic behaviour of partially delipidated membranes and with that of liposomes composed of purple membrane total lipids suggests that: (i) anesthetic molecules partition mainly at the protein/lipid interface inducing irreversible rearrangement of the boundary lipid layer, and (ii) different mode(s) or site(s) of interaction are responsible for the spectral and surface charge effects. The data are compatible with the hypothesis of anesthetics acting through partial dehydration of the membrane surface.