FOLIAR APPLICATION OF 15N-UREA AND ALLOCATION INTO GLUTEN OF DIFFERENT WHEAT CULTIVARS

Assessment of fertilizer nitrogen uptake into wheat grains and proteins is an important issue for selec-tion of N efficient cultivars. The 15N dilution technique is the most reliable way to follow the flow and fate of N for studies examining the path of N into wheat grains. Studies on wheat cultivar responses to late-season urea application in terms of grain quality traits are scarce. To assess the effect of a late N fertilization, known as quality effective, classified German spring wheat cultivars and two cultivars from the Mediterranean territory were examined in a field experiment in northeast Germany. At flag leaf sheath opening, 20 kg N ha-1 were given as foliar application (urea solution; to which 15N labelled urea was added; 10 atom-% 15N enrichment; correspond to 8.3 mg 15N m-2). At maturity, 35 days after 15N labelling, the gluten protein content, the 15N-recovery, and the 15N content of grains and of gluten were determined. Forty (Gönen) to 58% (Picolo) of the applied 15N was recovered in the grains per m2, which means an effective translocation of the late applied N, however no significant differences between the cultivars occurred. The 15N content in grains was markedly higher in Thasos, Melissos, Taifun, Picolo, Triso (mean 14.7 μg 15N g-1 dry matter-1) compared to Tybalt, Monsun, Golia and Gönen (mean 11.6 μg 15N g-1 dry matter-1). The 15N content of the gluten fraction was not influenced by cultivar and lies in the range between 14.7 and 19.4 μg 15N g-1 dry matter-1. The applied 15N is after 35 days at harvest to 16% involved in the gluten synthesis, and this independently of the spring wheat cultivars and classification

IN-VITRO RETENTION OF DIFFERENT 15N SOURCES AT BIOCHAR

Biochar, which can be used for improving soil fertility, is a carbon rich, heterogeneous, and chemically complex material. It is known that biochar ab/adsorbs nutrients, but there is still a lack of knowledge regarding these effects. To investigate the ability of biochar to adhere nitrogen an in-vitro experiment was conducted. Different inorganic (ammonium, nitrate, and ammonium nitrate) and organic 15N sources (urea; valine, phenylalanine, isoleucine, and glutamic acid; also yeast protein as a high molecular weight compound) were added to Pyro-biochar and to HTC-biochar to estimate retention after 15 and 30 days, and also to examine the effect of washing on 15N. The 15N in-vitro retention (%) of 15N-inorganic and 15N-organic substances at Pyro-BC and HTC-BC, at days 15 and 30, was less than 10% for both biochar’s. This amount could substance specific clearly reduced by washing. The high molecular weight 15N yeast protein adhered to 30% for HTC-biochar, which was 3-fold higher than for Pyro-biochar. Therefore, the manufacturing process of the two biochar’s had a significant impact on in-vitro retention. The functional groups, and therefore Van-der-Waals-interactions, chemical reaction, the affiliation of amino acids and the molecular size of compounds, such as yeast protein, can affect the 15N retention of these substances

Isotope-labelled urea to test colon drug delivery devices in vivo:principles, calculations and interpretations

<p>This paper describes various methodological aspects that were encountered during the development of a system to monitor the in vivo behaviour of a newly developed colon delivery device that enables oral drug treatment of inflammatory bowel diseases. [C-13]urea was chosen as the marker substance. Release of [C-13]urea in the ileocolonic region is proven by the exhalation of (CO2)-C-13 in breath due to bacterial fermentation of [C-13]urea. The (CO2)-C-13 exhalation kinetics allows the calculation of a lag time as marker for delay of release, a pulse time as marker for the speed of drug release and the fraction of the dose that is fermented. To determine the total bioavailability, also the fraction of the dose absorbed from the intestine must be quantified. Initially, this was done by calculating the time-dependent [C-13]urea appearance in the body urea pool via measurement of C-13 abundance and concentration of plasma urea. Thereafter, a new methodology was successfully developed to obtain the bioavailability data by measurement of the urinary excretion rate of [C-13]urea. These techniques required two experimental days, one to test the coated device, another to test the uncoated device to obtain reference values for the situation that 100 % of [C-13]urea is absorbed. This is hampered by large day-to-day variations in urea metabolism. Finally, a completely non-invasive, one-day test was worked out based on a dual isotope approach applying a simultaneous administration of [C-13]urea in a coated device and [N-15(2)]urea in an uncoated device. All aspects of isotope-related analytical methodologies and required calculation and correction systems are described.</p>

A non-invasive, low-cost study design to determine the release profile of colon drug delivery systems:A feasibility study

PURPOSE: Conventional bioavailability testing of dosage forms based on plasma concentration-time graphs of two products in a two-period, crossover-design, is not applicable to topical treatment of intestinal segments. We introduce an isotope dual-label approach ((13)C- and (15)N(2)-urea) for colon drug delivery systems that can be performed in a one-day, non-invasive study-design. METHODS: Four healthy volunteers took an uncoated or a ColoPulse-capsule containing (13)C-urea and an uncoated capsule containing (15)N(2)-urea. In case of colon-release (13)C-urea is fermented and (13)C detected as breath (13)CO(2). Absorbed (13)C-urea and (15)N-urea are detected in urine. RESULTS: C and (15)N in urine released from uncoated capsules showed a ratio of 1.01 ± 0.06. The (13)C/(15)N-recovery ratio after intake of a ColoPulse-capsule was constant and lower >12 h post-dose (median 0.22, range 0.13-0.48). The (13)C/(15)N-ratio in a single urine sample at t ≥ 12 h predicted the 24 h non-fermented fraction (13)C of <26 %. Breath (13)CO(2) indicated delayed (>3 h) release and a fermented fraction (13)C >54 %. CONCLUSIONS: Breath and urine (13)C and (15)N data describe the release-profile and local bioavailability of a colon delivery device. This allows non-invasive bioavailability studies for evaluation of colon-specific drug delivery systems without radioactive exposure and with increased power and strongly reduced costs

Gastrointestinal pH and Transit Time Profiling in Healthy Volunteers Using the IntelliCap System Confirms Ileo-Colonic Release of ColoPulse Tablets

Introduction ColoPulse tablets are an innovative development in the field of oral dosage forms characterized by a distal ileum and colon-specific release. Previous studies in humans showed release in the ileo-colonic region, but the relationship between gastrointestinal pH and release was not experimentally proven in vivo. This information will complete the in vivo release-profile of ColoPulse tablets. Materials and Methods Release from ColoPulse tablets was studied in 16 healthy volunteers using the dual label isotope strategy. To determine gastrointestinal pH profiles and transit times the IntelliCap system was used. A ColoPulse tablet containing C-13-urea and an uncoated, immediate release tablet containing N-15(2)-urea were taken simultaneously followed by a standardized breakfast after three hours. Five minutes after intake of the tablets the IntelliCap capsule was swallowed and pH was measured until excretion in the feces. Breath and urine samples were collected for isotope analysis. Results Full analysis could be performed in 12 subjects. Median bioavailability of C-13-urea was 82% (95% CI 74-94%, range 61-114%). The median lag time (5% release of C-13) was 5: 42 h (95% CI 5: 18-6: 18 h, range 2: 36-6: 36 h,) There was no statistically significant difference between lag time based on isotope signal and colon arrival time (CAT) based on pH (median 5: 42 vs 5: 31 h p = 0.903). In all subjects an intestinal pH value of 7.0 was reached before release of C-13 from the ColoPulse tablet occurred. Discussion and Conclusions From the combined data from the IntelliCap system and the C-13-isotope signal it can be concluded that release from a ColoPulse tablet in vivo is not related to transit times but occurs in the ileo-colonic region after pH 7.0 is reached. This supports our earlier findings and confirms that the ColoPulse system is a promising delivery system for targeting the distal ileum and colon

Demographics of included subjects (healthy volunteers).

<p>Demographics of included subjects (healthy volunteers).</p