Messung des Energieumsatzes in biologischen Systemen mit stabilen Isotopen

Abstract

Effects of millipedes and earthworms on the decomposition of ¹⁵N-labelled litter of winter oilseed rape were investigated in a microcosm field experiment over a period of 264 days on an oat field near Göttingen managed by integrated farming.

A total of 32 microcosms were filled with defaunated soil. ¹⁵N-labelled rape litter was placed either on top of the soil or buried into the soil simulating mulching and ploughing, respectively. To the microcosms nine adult individuals of Blaniulus guttulatus (Diplopoda) and two of Aporrectodea caliginosa (Lumbricidae) were added separately or in combination.

In general, the presence of the animals accelerated the decomposition rate of the litter material. The effects were most pronounced in the presence of Aporrectodea caliginosa. The total amount of nitrate, ammonium and the amount of ¹⁵N leached from the microcosms was increased in the presence of earthworms or of both earthworms and millipedes. Both species proved to be important members of the detritus food web of the agricultural system studied.     

Influence of earthworms on the sulfur turnover in the soil

Abstract The effects of earthworm activity on the concentration and isotopic composition of total sulfur in soils was investigated using batch experiments. Two ecologically different lumbricid species, the anecic Lumbricus terrestris and the endogeic Aporrectodea caliginosa, were used. The earthworms were fed birch leaves, beech leaves, cattle manure or mixed plant litter. All food sources differed isotopically (δ(34)S) from the soil (Parabraunerde). As a reference, one experiment was carried out without additional food. The experimental results show, that both earthworm species influence the total S-content and the δ(34)S-values in the soil by digestion of the different food sources. The differences in the total S-content of the earthworm tissues and in the S-isotopic composition of the casts can be attributed to the ecological differences between the earthworm species.     

Influence of Earthworms on the Sulfur Turnover in the Soil

Abstract

The effects of earthworm activity on the concentration and isotopic composition of total sulfur in soils was investigated using batch experiments. Two ecologically different lumbricid species, the anecic Lumbricus terrestris and the endogeic Aporrectodea caliginosa, were used. The earthworms were fed birch leaves, beech leaves, cattle manure or mixed plant litter. All food sources differed isotopically (δ³⁴S) from the soil (Parabraunerde). As a reference, one experiment was carried out without additional food.

The experimental results show, that both earthworm species influence the total S-content and the δ³⁴S-values in the soil by digestion of the different food sources. The differences in the total S-content of the earthworm tissues and in the S-isotopic composition of the casts can be attributed to the ecological differences between the earthworm species.     

Isotopic discrimination during litter decomposition and delta13C and delta15N soil profiles in a young artificial stand and in an old floodplain forest

In the present study, rates of litter decomposition and microbial biomass nitrogen were monitored over an 8-month period in a young broadleaf plantation (18 y) and in an old floodplain forest. Moreover, delta13C and delta15N temporal variations within soil profiles were evaluated at both sites. Rates of litter decomposition were higher in spring and autumn than in summer, in both forests. At the end of the observation period the percentage of original litter remaining was not statistically different between the young and the old forest and accounted for 60-70% of the original amount. Microbial biomass nitrogen in the remaining litter and the percentage of litter mass lost during decomposition were positively correlated. The difference in litter quality affected the decomposition rate and also the changes in carbon isotopic composition during the decomposition process. In contrast, 15N isotopic signatures showed a similar trend in the litter of the two forests irrespective of the litter quality. Although delta13Csoil and delta15Nsoil showed considerable temporal variation they increased with depth in the soils of both sites but their seasonal changes did not reflect those of the decomposing litter. Within the same soil horizon, both delta13C and delta15N showed similar seasonal trends in the soils of the two forests, suggesting the involvement of environmental factors acting at regional level, such as soil temperature and rainfall variations, in regulating seasonal delta13C and delta15N soil variations.     

Multivariate metabolic profiling using 1H nuclear magnetic resonance spectroscopy of freeze-tolerant and freeze-intolerant earthworms exposed to frost

Individuals of the freeze-tolerant earthworm, Dendrobaena octaedra, and four freeze-intolerant earthworm species (Dendrodrilus rubidus, Aporrectodea icterica, A. caliginosa, and A. longa) were frozen at -2 degree C. Control earthworms were exposed to +2 degree C. 1H nuclear magnetic resonance spectroscopy-based metabolic profiling in combination with multivariate pattern recognition methods (metabonomics) was used to produce a cross-species comparison. Several biochemical changes were detected as a result of freezing in all worm species, including an increase in relative free alanine concentrations, and an apparent conversion of adenosine to inosine. It was also possible to determine a number of biochemical changes that were unique to the freeze-tolerant species, D. octaedra. The most obvious difference was that, although all species showed an increase in glucose concentrations, the increase was largest in D. octaedra, and was coupled with a concomitant decrease in glycogen. This confirms that--like previously studied freeze-tolerant earthworm species--tolerance is effected by rapid glucose production from glycogen reserves. An additional difference noted was that succinate increased in all species on freezing, but the increase was least in D. octaedra. Furthermore there was no lactate accumulation in D. octaedra, whereas three of the other four species accumulated lactate. This indicates that anoxic metabolism was lowest in the freeze-tolerant species.     

Use of 13C and 15N mass spectrometry to study the decomposition of Calamagrostis epigeios in soil column experiments with and without ash additions

The dynamics of C and N in terrestrial ecosystems are not completely understood and the use of stable isotopes may be useful to gain further insight in the pathways of CO2 emissions and leaching of dissolved organic carbon (DOC) and nitrogen (DON) during decomposition of litter. Objectives were (i) to study the decomposition dynamics of Calamagrostis epigeios, a common grass species in forests, using 13C-depleted and 15N-enriched plants and (ii) to quantify the effect wood ash addition on the decomposition and leaching of DOC and DON. Decomposition was studied for 128 days under aerobic conditions at 8 degrees C and moisture close to field capacity in a spodic dystric Cambisol with mor-moder layer. Variants included control plots and additions of (i) Calamagrostis litter and (ii) Calamagrostis litter plus 4 kg ash m-2. (i) Decomposition of Calamagrostis resulted in a CO2 production of 76.2 g CO2-C m-2 (10% of added C) after 128 days and cumulative DOC production was 14.0 g C m-2 out of which 0.9 g C m-2 was Calamagrostis-derived (0.1% of added C). The specific CO2 formation and specific DOC production from Calamagrostis were 6 times higher (CO2) and 4 times smaller (DOC) than those from the organic layer. The amount of Calamagrostis-derived total N (NH4+, NO3-, DON) leached was 0.7 g N m-2 (4.8% of added N). Cumulative DON production was 0.8 g N m-2 which was slightly higher than for the control. During soil passage, much of the DOC and DON was removed due to sorption or decomposition. DOC and DON releases from the mineral soil (17 cm depth) were 6.3 g C m-2 and 0.5 g N m-2. (ii) Addition of ash resulted in a complete fixing of CO2 for 40 days due to carbonatisation. Afterwards, the CO2 production rates were similar to the variant without ash addition. Production of DOC (98.6 g C m-2) and DON (2.5 g N m-2) was marked, mainly owing to humus decay. However, Calamagrostis-derived DOC and Calamagrostis-derived total N were only 3.9 g C m-2 (0.5% of added C) and 0.5 g N m-2 (3.4% of added N). The specific DOC production rate from the organic layer was 6 times higher than that from Calamagrostis. The results suggest that with increasing humification from fresh plant residues to more decomposed material (OF and OH layers) the production ratio of DOC/CO2-C increases. Addition of alkaline substances to the forest floor can lead to a manifold increase in DOC production.     

15N-Dynamics of Cucumber (Cucumis sativus L.) in Field Trials on Sandy Loam in Brandenburg (Germany)

Abstract

Field experiments were conducted to study the ¹⁵N-utilization of cucumbers (Cucumis sativus L.) grown on sandy loam under black mulch film. With the progress of the ontogenetic development the plants took up rising ¹⁵N-amounts, which were increasingly transferred to the fruits after the beginning of flowering. At the end of the vegetation period more than 55% of the applied ¹⁵N-labelled fertilizer was found in the plants, and from this portion more than 70% in the fruits. Up to 13% of the total plant nitrogen were derived from the fertilizer. In the top soil layer (0–30 cm) the ¹⁵N-content was strongly reduced during plant growth. Though most of the ¹⁵N was taken up by the plants, a ¹⁵N transfer to deeper soil layers (30–60 cm, 60–90 cm) was observed. Balancing the amount of applied ¹⁵N-fertilizer indicates a loss of 11% during the experimental period.     

Independence of alpine meadow plants from soil organic matter for nitrogen supply: evidence from stable nitrogen isotopes

Stable nitrogen isotope signatures of major sources of mineral nitrogen (mineralization of soil organic nitrogen, biological N(2) fixation by legumes, annual precipitation and plant litter decomposition) were measured to relatively define their individual contribution to grass assimilation at the Haibei Alpine Meadow Ecosystem, Qinghai, China. The results indicated that delta(15)N values (-2.40 per thousand to 0.97 per thousand) of all grasses were much lower than those of soil organic matter (3.4+/-0.18 per thousand) and mineral nitrogen (ammonium and nitrate together, 7.8+/-0.57 per thousand). Based on the patterns of stable nitrogen isotopes, soil organic matter (3.4+/-0.18 per thousand), biological N(2) fixation (0 per thousand), and precipitation (-6.34+/-0.24 per thousand) only contributed to a small fraction of nitrogen requirements of grasses, but plant litter decomposition (-1.31+/-1.01 per thousand) accounted for 67 %.     

Stable isotopic studies of earthworm feeding ecology in tropical ecosystems of Puerto Rico

Feeding strategies of earthworms and their influence on soil processes are often inferred from morphological, behavioral and physiological traits. We used (13)C and (15)N natural abundance in earthworms, soils and plants to explore patterns of resource utilization by different species of earthworms in three tropical ecosystems in Puerto Rico. In a high altitude dwarf forest, native earthworms Trigaster longissimus and Estherella sp. showed less (15)N enrichment ((15)N = 3-6 per thousand) than exotic Pontoscolex corethrurus ((15)N =7-9 per thousand) indicating different food sources or stronger isotopic discrimination by the latter. Conversely, in a lower altitude tabonuco forest, Estherella sp. and P. corethrurus overlapped completely in (15)N enrichment ((15)N = 6-9 per thousand), suggesting the potential for interspecific competition for N resources. A tabonuco forest converted to pasture contained only P. corethrurus which were less enriched in (15)N than those in the forest sites, but more highly enriched in (13)C suggesting assimilation of C from the predominant C(4) grass. These results support the utility of stable isotopes to delineate resource partitioning and potential competitive interactions among earthworm species. Copyright 1999 John Wiley & Sons, Ltd.     

黄土丘陵区林草地枯落层盖度遥感估算研究

枯落层盖度的定量估算对于植被防蚀功效的评价具有重要作用。在陕北黄土丘陵沟壑区选取典型落叶林和退耕草地作为光谱测试样地,通过室内和野外实验分析枯落层—土壤混合场景的光谱变化规律,研究高光谱指数NDLI(normalized difference lignin index)和CAI(cellulose absorption index)估算枯落层盖度的有效性。结果表明,受颜色及含水量等因素的影响,不同盖度枯落层—土壤混合场景的光谱反射率呈现不同的变化规律。干和湿状态下,随着枯落层盖度的增加混合场景的NDLI、CAI指数值均呈现增大的趋势,CAI与枯落层盖度的相关性高于NDLI,R2最高为0.98(阔叶林和退耕草地干的混合场景),CAI能够更有效地估算枯落层盖度。野外实测验证了室内实验结果,退耕草地混合场景的CAI值与枯落层盖度相关性最高(R2=0.90),野外条件下两种高光谱指数估算枯落层盖度的有效性均有一定程度的降低。该研究为枯落层盖度的遥感定量反演提供了基础与依据。     

The effect of soil temperature and moisture on organic matter decomposition and plant growth

The effect of soil temperature and moisture on plant growth and mineralisation of organic residues was investigated using 15N-labelled soybean residues and temperature-controlled tanks in the glasshouse. Treatments were arranged in a factorial design with: three soil temperatures (20, 26 and 30 degrees C), two soil moisture regimes (8% (-800 Kpa) or 12% (-100 Kpa)), soybean residues added (enriched at 1.82 atom % 15N excess) or no residues; and either sown with ryegrass or not sown. Pots were sampled six weeks after planting and 15N-enrichment and delta13C of the plant and soil fractions were determined. Soil inorganic N was also periodically measured. Available inorganic N increased significantly with addition of residues and generally decreased with increasing temperature. Plant dry matter decreased significantly with increase in soil temperature and increased with increasing moisture. Root-to-shoot ratio declined with increased temperature and moisture. Percentage nitrogen derived from residues (%Ndfr) increased linearly with increased temperature and moisture. Delta13C decreased linearly with increasing temperature and decreasing moisture status. There was a significant correlation between transpiration and dry matter production, but there was no correlation between water use efficiency and delta13C. The results suggest that C: N ratio of the root material effects the root turnover and in turn the water supply capacity of the root system.     

Use of 13C and 15N Mass Spectrometry to Study the Decomposition of Calamagrostis epigeios in Soil Column Experiments with and Without Ash Additions

Abstract

The dynamics of C and N in terrestrial ecosystems are not completely understood and the use of stable isotopes may be useful to gain further insight in the pathways of CO₂ emissions and leaching of dissolved organic carbon (DOC) and nitrogen (DON) during decomposition of litter. Objectives were (i) to study the decomposition dynamics of Calamagrostis epigeios, a common grass species in forests, using ¹³C-depleted and ¹⁵N-enriched plants and (ii) to quantify the effect wood ash addition on the decomposition and leaching of DOC and DON. Decomposition was studied for 128 days under aerobic conditions at 8°C and moisture close to field capacity in a spodic dystric Cambisol with mor-moder layer. Variants included control plots and additions of (i) Calamagrostis litter and (ii) Calamagrostis litter plus 4 kg ash m^?2.

• Decomposition of Calamagrostis resulted in a CO₂ production of 76.2 g CO₂–C m^?2 (10% of added C) after 128 days and cumulative DOC production was 14.0 g C m^?2 out of which 0.9g C m^?2 was Calamagrostis-derived (0.1% of added C). The specific CO₂ formation and specific DOC production from Calamagrostis were 6 times higher (CO₂) and 4 times smaller (DOC) than those from the organic layer. The amount of Calamagrostis-derived total N (NH₄ ⁺, NO₃ ^?, DON) leached was 0.7g N m^?2 (4.8% of added N). Cumulative DON production was 0.8g N m^?2 which was slightly higher than for the control. During soil passage, much of the DOC and DON was removed due to sorption or decomposition. DOC and DON releases from the mineral soil (17cm depth) were 6.3g C m^?2 and 0.5g N m^?2.

  Addition of ash resulted in a complete fixing of CO₂ for 40 days due to carbonatisation. Afterwards, the CO₂ production rates were similar to the variant without ash addition. Production of DOC (98.6g C m^?2) and DON (2.5g N m^?2) was marked, mainly owing to humus decay. However, Calamagrostis-derived DOC and Culamagrostis-derived total N were only 3.9g C m^?2 (0.5 YO of added C) and 0.5g N m^?2 (3.4% of added N). The specific DOC production rate from the organic layer was 6 times higher than that from Cularnagrostis. The results suggest that with increasing humification from fresh plant residues to more decomposed material (O_F and O_H layers) the production ratio of DOC/CO₂-C increases. Addition of alkaline substances to the forest floor can lead to a manifold increase in DOC production.

     

Lysimeter Investigations on the Effect of Winter Catch Crops and Weeded Fallow on the N-Dynamics in a Sandy Treposol Soil of Northeast Germany

Abstract

Lysimeter experiments (soil: sandy treposol, from the region “Havelländisches Luch”, Brandenburg, Germany) with application of ¹⁵N labelled fertilizer (80 kg N per ha as ¹⁵NH₄ ¹⁵NO₃, 10 at.-%¹⁵N exc.; for simulating mineralization in the early autumn period) were carried out to determine to what extent the amount of mineral- N was temporary conserved by winter catch crops, taken up subsequently in the vegetation periods by following crops, taken by subsequently in the vegetation periods by following crops, or percolated in the leaching water, respectively. The results were as follows:

1) Until winter or spring respectively, the catch crop uptake rates of applied mineral-N were 32% for phacelia (Phacelia tanacetifolia BENTH.), 25% for winter rape (Brassica napus L. cv. ‘AKELA’), and 16% for white mustard (Sinapis alba L.).

2) In the year after, following maize incorporated from 2.1 to 4.5% of the fertilizerborne N. The following plant community of fallow took up from 0.2 to 0.5% N originating from the fertilizer-N.

3) In comparison with the catch crops, N-leaching losses under fallow conditions were highest and equivalent to 17% of the applied fertilizer-N amount. In contrast to 3% of white mustard, phacelia and winter rape reduced N-leaching losses to 0.2 and 0.3% of the applied fertilizer-N amount.

4) In spring of the first year after the beginning of investigations, N-leaching losses were highest under fallow conditions and white mustard cultivation. Thus, the amounts of nitrate losses would exceed the EU limit for drinking water.

5) Three years after the investigations had been started, 10% (white mustard) and 20% (fallow) of the applied fertilizer-N was still found in th lysimeter soil.     

Der [15N]Methacetin-Leberfunktionstest zum Nachweis von Arzneimittelnebenwirkungen. Antibiotika-Therapie mit Amplicillin und mit Gefotaxime bei Neugeborenen

Abstract

The effect of soil temperature and moisture on plant growth and mineralisation of organic residues was investigated using ¹⁵N-labelled soybean residues and temperature-controlled tanks in the glasshouse. Treatments were arranged in a factorial design with: three soil temperatures (20, 26 and 30°C), two soil moisture regimes (8% (–800 Kpa) or 12% (–100 Kpa)), soybean residues added (enriched at 1.82 atom % ¹⁵N excess) or no residues; and either sown with ryegrass or not sown. Pots were sampled six weeks after planting and ¹⁵N-enrichment and δ¹³C of the plant and soil fractions were determined. Soil inorganic N was also periodically measured.

Available inorganic N increased significantly with addition of residues and generally decreased with increasing temperature. Plant dry matter decreased significantly with increase in soil temperature and increased with increasing moisture. Root-to-shoot ratio declined with increased temperature and moisture. Percentage nitrogen derived from residues (%Ndfr) increased linearly with increased temperature and moisture. Δ¹³C decreased linearly with increasing temperature and decreasing moisture status. There was a significant correlation between transpiration and dry matter production, but there was no correlation between water use efficiency and Δ¹³C.

The results suggest that C: N ratio of the root material effects the root turnover and in turn the water supply capacity of the root system.     

直接测汞仪测定土壤中的总汞

建立了直接测汞仪快速测定土壤中总汞的方法。通过实验对干燥温度、干燥时间、分解温度、分解时间等条件进行了优化,并进行了线性关系、精密度等实验。结果表明,本法线性范围0—500ng,相关系数≥0.9995,检出限为0.0032ng,相对标准偏差为0.56%。方法灵敏度高,简便、快速、准确,适用于对土壤中的总汞的测定。     

基于光谱特征的雅鲁藏布大峡谷森林枯落物水源涵养能力反演研究

水源涵养是生态系统重要的服务功能，森林作为一种复杂的生态系统，其组成部分对于水源涵养的贡献率各不相同；森林枯落物直接覆盖于地表，既来自于林冠层也抑制土壤层的水分蒸散，因此枯落物层在水源涵养功能中发挥了重要作用。遥感和高光谱技术为远距离识别面状区域的水源涵养能力提供了解决方案，特别在高原地区，遥感是获取地表信息的快速手段。以雅鲁藏布大峡谷为研究区，用ASD(便携式地物)光谱仪测定主要树种(高山松、林芝云杉和川滇高山栎)的叶片高光谱数据并构建植被指数，同时，通过样地采样获取枯落物样本并计算样本的持水拦蓄性能，然后建立植被指数与有效拦蓄量的多元回归模型。在此基础上，基于Sentinel-2影像反演大峡谷主要树种枯落物的水源涵养能力分布情况，最后结合验证点对反演模型进行精度评价。结果显示：（1）三类树种的叶片反射率趋势相似，川滇高山栎的反射率最高，高山松次之，林芝云杉最低；（2）枯落物的有效拦蓄量从大到小排序为：林芝云杉(48.36 t·ha-1)>川滇高山栎(39.24 t·ha-1)>高山松(32.32 t·ha-1)。林芝云杉枯落物的分解程度和蓄积量均最高，因此持水拦蓄能力最强；川滇高山栎的革质叶片不利于分解堆积，进而限制蓄水能力；高山松含有较多油脂，不易被水浸湿，导致持水能力较弱。（3）通过Person相关系数分析和多元线性回归模型得知，叶片蜡质参数和衰减程度越高，枯落物的水源涵养能力越弱；植被生长态势越好、色素和叶片水分含量越高，其水源涵养能力越强。（4）枯落物水源涵养能力反演模型的精度评价结果良好，高山松、林芝云杉和川滇高山栎的样本检验点拟合优度R2分别为0.943，0.815和0.812，均方根误差RMSE分别为1.597，2.270和1.953，表明模型可以用于大峡谷森林枯落物水源涵养能力的预测分布研究。     

蚯蚓诱导-黑麦草吸收土壤Cd的相关性研究

利用石墨炉(GF-990)原子吸收法,对蚯蚓诱导条件下黑麦草对土壤Cd吸收规律进行了研究.结果表明:(1)在3～6 mg·kg-1的Cd浓度范围内,黑麦草地下部分Cd含量与蚯蚓数量呈极显著正相关(γ=0.8832*～0.9862**),黑麦草地上部分Cd含量与蚯蚓数量的正相关性不显著(γ=0.3455～0.325 4);而土壤Cd含最与蚯蚓数量之间呈显著的负相关性(r=-0.5887～-0.6784*).(2)在相等数最的蚯蚓条件下,随着土壤中Cd浓度增加,黑麦草地上、地下部分Cd的含量均升高.(3)在相同的土壤环境下,蚯蚓数量与蚯蚓体内Cd含量呈极显著负相关(r=-0.982 0**～-0.9916**).     

镉在不同质地水稻土剖面中的分布特征及与作物吸收的关系

通过野外定点采集土壤和作物植株、籽粒样品, 利用石墨炉(novAA400)原子吸收法, 研究了成都平原稻麦轮作下水稻土剖面中镉的分布特征及其与水稻、小麦吸收镉的相关性。结果表明,土壤剖面中的镉主要集中在0～15 cm的耕层土壤,总体表现为“向根层富集”的特征,土壤全镉和有效态镉均随土层深度的增加而逐渐降低,30～45 cm土层的全镉和有效态镉含量平均值分别为表层的47.60%和39.49%。不同质地土壤中的镉向下迁移量大小顺序为砂壤>重壤>中壤,以15～30 cm土层的迁移量差异最大。土壤pH与0～15 cm土层的有效态镉含量间相关性不显著(r=-0.46),与15～30 cm和30～45 cm土层有效态镉含量间呈显著的负相关(r=-0.78*～-0.86**)。水稻、小麦秸秆和籽粒镉含量与0～15 cm和30～45 cm土层的全镉含量间相关性不大(r=-0.092～-0.383, 0.174～0.424),但与0～15 cm和15～30 cm土层的有效态镉含量呈显著正相关(r=0.766*～0.953**),与30～45 cm土层的有效态镉含量相关性不显著(r=0.526～0.584)。因此,土壤有效态镉含量比全镉含量更适合作为农作物产品安全的土壤镉污染评价指标。     

Evaluation of 15N Methods for the measurement of Denitrification in Soils

The precision of the ¹⁵N-emission and that of the ¹⁵N-balance methods was evaluated and both methods were compared in a denitrification experiment. ¹⁵N-analysis was performed with an isotope ratio mass spectrometer which was coupled to an elemental analyzer. The measuring sensitivity in soil and gas analysis was tested by analyzing ¹⁵N-standards. The detection limit for gas samples with two different procedures of ¹⁵N-gas analysis was δ¹⁵N = (4.5 ± 1.0)‰ and (0.5 ± 0.05)‰, respectively. The error in measurement was 19% and 12% respectively. ¹⁵N-analysis of a ¹⁵N-labelled soil (4.15 ppm ¹⁵N) resulted in a CV of 1.32%. The measurements had to be calibrated with soil standards because the ¹⁵N-values showed a continuous downward fluctuation in a range of 10–20% within several days, when only acetanilid was used for calibration. Mean ¹⁵N-losses which were determined with both methods during the denitrification experiment were in good agreement. The precision of the ¹⁵N-emission method was adequate in all variants of the experiment. The precision of the ¹⁵N-balance method however was unsatisfactory at low ¹⁵N-losses (0.2–2% of added ¹⁵N).     

Development and application of 15N-tracer substances for measuring the whole-body protein turnover rates in the human, especially in neonates: a review

Our research group of the Children's Hospital of the University of Rostock (Rostock group) has long-time experience in (15)N-labelling and in using yeast protein and its hydrolysates for tracer kinetic studies to evaluate parameters of the whole-body protein metabolism in premature infants. The particular advantage of applying an economically convenient, highly (15)N-enriched, and completely labelled yeast protein for evaluating protein turnover rates is the fact that the (15)N dose is spread among all proteinogenic amino acids. The absorption has been improved by hydrolysing [(15)N]yeast protein with thermitase into a mixture of amino acids, dipeptides and tripeptides so that faecal analysis becomes unnecessary when determining turnover rates. The review shows that, in contrast to the application of single (15)N-labelled amino acids with resulting overestimation of protein turnover rates, the (15)N-labelled yeast protein thermitase hydrolysate represents the amino acid metabolism more closely without causing amino acid imbalances. The (15)N-labelled yeast protein thermitase hydrolysate leads to the estimation of reliable protein turnover rates, particularly in premature infants.