Bile acids induce a cationic current, depolarizing pancreatic acinar cells and increasing the intracellular Na+ concentration

Biliary disease is a major cause of acute pancreatitis. In this study we investigated the electrophysiological effects of bile acids on pancreatic acinar cells. In perforated patch clamp experiments we found that taurolithocholic acid 3-sulfate depolarized pancreatic acinar cells. At low bile acid concentrations this occurred without rise in the cytosolic calcium concentration. Measurements of the intracellular Na(+) concentration with the fluorescent probe Sodium Green revealed a substantial increase upon application of the bile acid. We found that bile acids induce Ca(2+)-dependent and Ca(2+)-independent components of the Na(+) concentration increase. The Ca(2+)-independent component was resolved in conditions when the cytosolic Ca(2+) level was buffered with a high concentration of the calcium chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). The Ca(2+)-dependent component of intracellular Na(+) increase was clearly seen during stimulation with the calcium-releasing agonist acetylcholine. During acetylcholine-induced Ca(2+) oscillations the recovery of cytosolic Na(+) was much slower than the recovery of Ca(2+), creating a possibility for the summation of Na(+) transients. The bile-induced Ca(2+)-independent current was found to be carried primarily by Na(+) and K(+), with only small Ca(2+) and Cl(-) contributions. Measurable activation of such a cationic current could be produced by a very low concentration of taurolithocholic acid 3-sulfate (10 microm). This bile acid induced a cationic current even when applied in sodium- and bicarbonate-free solution. Other bile acids, taurochenodeoxycholic acid, taurocholic acid, and bile itself also induced cationic currents. Bile-induced depolarization of acinar cells should have a profound effect on acinar fluid secretion and, consequently, on transport of secreted zymogens.     

Recent progress in heteronuclear long-range NMR of complex carbohydrates: 3D H2BC and clean HMBC

The new NMR experiments 3D H2BC and clean HMBC are explored for challenging applications to a complex carbohydrate at natural abundance of ¹³C. The 3D H2BC experiment is crucial for sequential assignment as it yields heteronuclear one- and two-bond together with COSY correlations for the ¹H spins, all in a single spectrum with good resolution and non-informative diagonal-type peaks suppressed. Clean HMBC is a remedy for the ubiquitous problem of strong coupling induced one-bond correlation artifacts in HMBC spectra of carbohydrates. Both experiments work well for one of the largest carbohydrates whose structure has been determined by NMR, not least due to the enhanced resolution offered by the third dimension in 3D H2BC and the improved spectral quality due to artifact suppression in clean HMBC. Hence these new experiments set the scene to take advantage of the sensitivity boost achieved by the latest generation of cold probes for NMR structure determination of even larger and more complex carbohydrates in solution.     

Tree fruiting phenology in Kalinzu Forest, Uganda

The spatial and temporal variations in species composition and abundance of trees that fruited in mechanically logged, intensively pit‐sawn and essentially undisturbed forest areas in Kalinzu Forest (0°17′S, 0°30′S and 30°00′, 30°07′E) were assessed. The duration and frequency of fruiting episodes of selected pioneer, understorey and canopy tree species were also determined. These phenology aspects were monitored for 18 months (between February 1997 and July 1998) in 99 plots, each 20 m × 20 m in size. Eighty species consisting of 1489 trees fruited during the study. Most of the species were recorded in the undisturbed forest area and least in the mechanically logged areas. Monthly number of individuals and species that fruited in each forest condition were significantly related to monthly rainfall. Two pioneer species (Musanga leo‐errerae and Trema orientalis), one sub‐canopy (Funtumia africana) and canopy (Parinari excelsa) species had extended fruiting phases (>5 months). Two understorey species (Oxyancius speciosus and Tabernaemontana spp.) had an extended phase while the third (Teclea nobilis) had a short (≤5 months) fruiting phase. Of the selected species, only Strombosia scheffleri (a sub‐canopy species) and P. excelsa had more than one fruiting episode.     

Characteristics of the immunological reactivity of the body in the streptococcal carrier state

The use of the discrete dynamic method for the treatment of data obtained in the survey of streptococcus carriers has made it possible to find out that their immune status is determined not so much by the quantitative changes in the results of individual immunological tests (for the bactericidal activity of the blood serum, lysozyme, IgG, IgM, IgA and the phagocytic activity of neutrophils), but, to a greater extent, by the interrelations of these characteristics. Significant differences in the interrelations of various humoral characteristics and in their relationship to the phagocytic process have been detected in the group of carriers as compared with the control group.