title: [Effect of repeated thawing of body samples and of the storage time of excrements on the changes of N-metabolites].
abstract: Frozen samples of blood plasma and corpuscular blood constituents from 10 layers were thawed two times at intervals of 36 days (during which they were stored at -30 degrees C) and analysed for changes of the trichloroacetic acid (TCA)-soluble proportion in the total nitrogen. Samples of muscle tissue, liver, and intestine were frozen in liquid nitrogen, stored at -30 degrees C, thawed three times at 36-day intervals and also analysed for TCA-soluble nitrogen. In spite of the low storage temperature, the TCA-soluble proportion in the blood fractions had significantly increased. Proteolysis could hardly be evidenced in muscle protein stored for 108 days and thawed three times. The liver and intestine samples showed significant increases of the TCA-soluble fraction after thawing, repeated freezing in liquid nitrogen and storage at -3o degrees C. In urine samples from colostomized hens, a non-linear increase of the amount of NH3 and a non-linear decrease of the amount of urea were observed after storage for 3, 6 and 12 days at 0 degrees C. The proportion of uric acid-N in the urine N was unaffected by the time of storage. The content of NH3-N in the faeces increased significantly with increasing storage time, whereas that of urea-N decreased. The use of such repeatedly thawed samples for determining N-metabolites is commented upon.
mesh_terms: D004355:Drug Stability; D005243:Feces / Q000032:analysis*; D005615:Freezing; D006801:Humans; D007422:Intestines / Q000032:analysis; D008099:Liver / Q000032:analysis; D009132:Muscles / Q000032:analysis; D009584:Nitrogen / Q000032:analysis* / Q000097:blood; D013048:Specimen Handling; D014508:Urea / Q000032:analysis; D014527:Uric Acid / Q000032:analysis
chemical_list: D014527:Uric Acid; D014508:Urea; D009584:Nitrogen
vernacular_title: Der Einfluss des mehrmaligen Auftauens von Körperproben sowie der Lagerungszeit von Exkrementen aug die Veränderung von N-Metaboliten.