Title page
Absorption of organic anions (phenol red, bromphenol blue and bromosulphonphthalein) has been studied after their application to rat liver surface in-vivo, employing a cylindrical glass cell (i.d. 9 mm, area 0.64 cm2). Every drug appeared gradually in the blood with the peak level at about 1 h, after which its concentration declined slowly. Absorbed model drug was efficiently excreted into the bile. These observations appear to indicate the possibility of drug absorption from liver surface membrane. Absorption ratios of model drugs were estimated to be more than 59 % in 6 h. As to phenol red, its biliary recovery and metabolism ratio did not change as compared with that of i.v. administration.
PHYSIOLOGICAL and BIOCHEMICAL ASPECTS
Thin-layer chromatography (TLC) of extracts from midribs and young bark of citrus exocortis virus-infected (CEV) citron showed one to three blue to violet fluorescent bands (2, 8), that were not found in extracts of tissue from healthy plants. The principal fluorescent substance (R, 0.40 to 0.45) consisted of scopoletin and umbelliferone, primarily as bound coumarins (about 90 per cent), plus small amounts of sinapic, ferulic, and coumaric acids (2, 7, 8). Even though the concentration of scopoletin and its ratio to umbelliferone (S/U ratio) in the principal fluorescent band varied with the kind of
The peculiar thermo-structural behavior of the anionic lipid DMPG.
Aqueous dispersions of the anionic phospholipid dimyristoyl phosphatidylglycerol (DMPG), around 100 mM ionic strength, are known to exhibit a thermal behavior similar to that of the largely studied lipid dimyristoyl phosphatidylcholine (DMPC), which undergoes a gel to liquid crystalline phase transition at 23 degrees C, well characterized by differential scanning calorimetry (DSC), and other methods. However, at low ionic strength, DMPG has been shown to present a large gel-fluid transition region, ranging from 18 to 35 degrees C. This intermediate phase is optically transparent and characterized by a continuous change in membrane packing. Structural properties of the DMPG gel-fluid transition region will be discussed, based on results obtained by several techniques: electron spin resonance (ESR) of spin labels at the membrane surface and intercalated at different depths in the bilayer; light scattering; DSC; small angle X-ray scattering (SAXS); and fluorescence spectroscopy of probes in the bilayer.