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F. Bairlein J. -D. Ludwigs H. -W. Helb G. Scheiffarth J. Haffer und M. Stock 《Journal of Ornithology》2001,142(3):367-373
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Krumbholz v. Berg Stubbe Barthelmehs J. Schwemmle Hackbarth Autoreferat Hassebrauk Hassebrauk v. Rathlef Ufer Schratz F. Schwanitz Ludwigs Hackbarth Scherz Schmidt Hülsbruch R. Schick 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1936,8(10):271-280
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Reaction of unsaturated uronic acid residues with mercuric salts. Cleavage of the hyaluronic acid disaccharide 2-acetamido-2-deoxy-3-O-(beta-D-gluco-4-enepyranosyluronic acid)-D-glucose. 总被引:2,自引:1,他引:2 下载免费PDF全文
Degradation of connective-tissue polysaccharides with bacterial or fungal eliminases and subsequent characterization of the reaction products are now part of standard methodology for the analysis of these compounds. However, the scope of preparative and analytical work based on the use of eliminases has been limited by the lack of procedures for specific removal of the unsaturated uronic acid residues generated in the eliminase reactions. In the present investigation, we have shown that these residues are cleaved by mercuric salts under mild conditions that are not likely to affect other structures in an oligo- or poly-saccharide molecule. Thus the disaccharide generated from hyaluronic acid by digestion with chondroitinase AC or ABC was cleaved into a keto acid and free N-acetylglucosamine within 10 min at room temperature upon exposure to 14 mM-mercuric acetate at pH 5. The reaction of the disaccharide with mercuric salts was used for ready determination of the distribution of radioactivity between the glucuronic acid and N-acetylglucosamine moieties in radioactive hyaluronic acid that had been synthesized by IMR-90 fibroblasts from 3H-labelled monosaccharides. When the precursor was [3H]galactose, over 95% of the incorporated radioactivity was found in the glucuronic acid moiety. In contrast, cells grown in the presence of [3H]glucosamine synthesized a polysaccharide in which almost all of the label was located in the N-acetylglucosamine units. It is apparent from these experiments that the reaction of unsaturated uronic acid residues with mercuric salts provides a new tool with potential for many applications in the study of the structure and metabolism of connective-tissue polysaccharides. 相似文献
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Jan-Dieter Ludwigs & Peter H. Becker 《Ethology : formerly Zeitschrift fur Tierpsychologie》2007,113(1):46-56
The probability of divorce in birds has been linked with age, breeding experience, reproductive output and synchrony in return. Here, we investigate the consequences of first breeding attempts in common terns for mating in the subsequent season. Nearly 20% of all first‐time breeders disappeared or skipped at least one season after recruitment. In 84 pairs, which consisted of at least one recruit and of which both partners returned to the colony, the divorce rate was 45%. We compared reproductive success, arrival dates, and asynchrony in arrival dates of pairs of the first breeding season against the second season, for both reunited and divorced pairs and males and females separately. First, in pairs of which both members came back to the colony, we found an increase of reproductive success most pronounced in males. In the second season reproductive success of divorced compared with reunited pairs was higher, as only divorced pairs significantly improved the number of fledglings, and again this relation was stronger in males. Secondly, females of reunited pairs arrived significantly earlier from the first to the second season and by far more days than their males. However, in divorced pairs former mates did not differ in the number of days they advance their arrivals. Finally, divorced males arrived on average 4 d earlier than their former mates, whereas divorced females arrived 5 d later compared with their former mates of the recruitment season. Contradictory to nearly all other divorce studies in birds so far, we found a clear fitness gain in divorced males. We suggest that the improvement in reproductive success of young males stems from a side‐effect of the birds’ quality and ability to reach the breeding site in appropriate time and earlier as potential competitors. In long‐lived bird species the heterogeneity among young individuals in the timing of arrival at the colony seems to explain why former recruit‐pairs reunite or split. For young males we suggest as best explanation of divorce that they profit from ‘pushing for an empty chair’, while females seem to profit from their choosiness and may actively decide between former and other mates. 相似文献
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J. -D. Ludwigs J. Haffer F. Bairlein K. -M. Exo J. Dierschke 《Journal of Ornithology》2003,144(3):367-373
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