Diversity of ethnic and racial VNTR RFLP fixed-bin frequency distributions.

To examine the impact that intra- and interracial genetic diversities have on VNTR RFLP-fragment-size distributions, a multiracial (East Asian, African American, U.S. Southwest Hispanic, and European Caucasian) and multiethnic (Chinese, Japanese, Korean, and Vietnamese) database has been constructed for the following loci: D1S7, D2S44, D4S139, and D10S28. Homogeneity between samples was examined using the Komologorov-Smirnov two-sample test for RFLP fragment sizes and a log-likelihood test for fixed-bin frequencies with theoretical and Monte Carlo empirical significance levels. Small but significant differences between theoretical and empirical significance-level distributions were observed with both procedures, particularly with the latter. The significance levels of the two types of tests were poorly correlated. Statistically significant differences in fragment-size and fixed-bin distributions were found within and between races, with greater differences occurring between races. Cluster analysis and principal components analysis, using different similarity measures, did not support the hypothesis of greater intra- than interracial diversity, which suggests that ethnic variation can be conservatively estimated by racial variation.     

Mode of action of recombinant Azotobacter vinelandii mannuronan C-5 epimerases AlgE2 and AlgE4.

The enzymes mannuronan C-5 epimerases catalyze conversion of beta-D-mannuronic acid to alpha-L-guluronic acid in alginates at the polymer level and thereby introduce sequences that have functional properties relevant to gelation. The enzymatic conversion by recombinant mannuronan C-5 epimerases AlgE4 and AlgE2 on alginate type substrates with different degree of polymerization and initial low fraction of alpha-L-guluronic acid was investigated. Essentially no enzymatic activity was found for fractionated mannuronan oligomer substrates with an average degree of polymerization, DP(n), less than or equal 6, whereas increasing the DP(n) yielded increased epimerization activity. This indicates that these enzymes have an active site consisting of binding domains for consecutive residues that requires interaction with 7 or more consecutive residues to show enzymatic activity. The experimentally determined kinetics of the reaction, and the residue sequence arrangement introduced by the epimerization, were modeled using Monte Carlo simulation accounting for the various competing intrachain substrates and assuming either a processive mode of action or preferred attack. The comparison between experimental data and simulation results suggests that epimerization by AlgE4 is best described by a processive mode of action, whereas the mode of action of AlgE2 appears to be more difficult to determine.     

Role of phospholamban in NO/EDRF-induced relaxation in rat aorta.

The role of endothelium-derived nitric oxide (NO) to cause smooth muscle phospholamban (PLB) phosphorylation was studied in the isolated perfused rat aorta precontracted with norepinephrine using a back-phosphorylation technique. NO-induced relaxation was associated with increased PLB-phosphorylation while norepinephrine as such was ineffective. Removal of endothelium significantly reduced PLB-phosphorylation in indomethacin treated vessels. Stimulation of NO-formation by ATP augmented PLB-phosphorylation in intact vessels but was ineffective in denuded aortas. The results indicate that PLB-phosphorylation of vascular smooth muscle plays an important role in mediating NO-dependent relaxation by enhancing Ca(++)-uptake into sarcoplasmic reticulum.     

Autoradiographische Untersuchungen über das Wachstum des Reissnerschen Fadens von Cyprinus carpio (L.)

Summary The incorporation of³⁵S-l-cysteine into the hypothalamic-hypophyseal neurosecretory system was studied in normal male albino rats and in similar rats which had received thiouracil or excess thyroxine during 18 days. The study was performed by autoradiography. Labelled cysteine was administered by intraperitoneal injections. The animals were sacrificed 30 min, 3 and 24 hours after injection. From the autoradiographs the grain counts were determined in the supraoptic nucleus, paraventricular nucleus, median eminence and infundibular process. The thyroxine-treated rats in the 30 minute group displayed a statistically almost significantly higher grain count in the supraoptic nucleus than the corresponding controls; the same was observed in the 3 hour group in the median eminence and infundibular process. In the 24 hour group, however, the grain count was clearly lower at all sites examined than in the controls. With the rats that had been under thiouracil treatment statistically significant differences were only established in the 24 hour group. Their grain count was higher at all sites than that of the corresponding controls. From the results the inference is drawn that thyroxine accelerates the protein synthesis in the ganglion cells of the supraoptic nucleus and accelerates the flow of NSM to the infundibular process and its release there into the blood flow. Thiouracil, again, retards the flow and the release.This work was supported by a grant from the Sigrid Jusélius Foundation, Helsinki.