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1.
Sources and flowpaths of dissolved organic carbon during storms in two forested watersheds of the Precambrian Shield 总被引:10,自引:4,他引:6
Dissolved organic carbon (DOC) concentrations and export were studied in two small catchments in central Ontario to examine DOC sources and to assess the hypothesis that organic matter adjacent to the stream is a significant contributor of DOC during storms. Different DOC dynamics and exports were observed according to the depth of the riparian water table. In Harp 4-21, riparian flowpaths were predominantly through A and upper B soil horizons and riparian soils contributed between 73 and 84% of the stream DOC export during an autumn storm. In Harp 3A, riparian flowpaths were predominantly through lower B horizons. Consequently, riparian soils were less important and hillslopes contributed more than 50% of the stream DOC export in subcatchments without wetlands during storms. Wetlands and adjacent soils contributed significantly to DOC export in Harp 3A; 8% of the total catchment area exported 32 to 46% of the storm runoff DOC. DOC export dynamics in wetlands and riparian soils were distinctly different. In wetlands, transport was affected by leaching and flushing of DOC at the wetland surface leading to lower DOC concentrations with successive storms. In riparian soils, groundwater flowpaths were more important and stronger positive relationships between discharge and DOC concentration were observed. Precipitation, throughfall and stemflow were minor sources of stream DOC during storms and contributed less than 20% of the total export. 相似文献
2.
The significance of storms for the concentration and export of dissolved organic carbon from two Precambrian Shield catchments 总被引:13,自引:6,他引:7
Dissolved organic carbon (DOC) concentrations and DOC export arestudied during storms to examine the relationship between DOCconcentration and stream discharge and to assess the importance of stormson DOC export. Storms were monitored in seven subcatchments within twosmall watersheds (Harp 4--21 and Harp 3A) on the Precambrian Shield inCentral Ontario, Canada. Stream DOC concentrations increase during stormsby as much as 100% and 410% in Harp3A and Harp 4--21 respectively. The seasonal regression between DOC andstream discharge is significant in subcatchments without wetlands(r2 > 0.7) but is not significant in thetwo subcatchments with small wetland areas (r2 <0.06). On average, regressions based on weekly data yield accurate estimatesof DOC export but the variation in regressions among individual storms andthe small number of high DOC samples result in uncertainties of more than30% in DOC export. The period-weighted calculation ofDOC export from weekly data underestimates export by 14%and 22% in Harp 3A and Harp 4--21 respectively. Stormswere responsible for 57% to 68% of theDOC export in the autumn and 29% to 40%of the DOC export in the spring. A single large storm accounted for31% of the autumn DOC export in Harp 3A. The importanceof individual storms for DOC export and the variation in the relationshipbetween DOC and stream discharge among storms make it difficult to predictthe effects of climate change on DOC export and DOC concentrations. 相似文献
3.
Nitrogen mineralization in upland Precambrian Shield catchments: Contrasting the role of lichen-covered bedrock and forested areas 总被引:1,自引:1,他引:0
Sébastien Lamontagne 《Biogeochemistry》1998,41(1):53-69
The upland boreal forest at the Experimental Lakes Area (northwestern Ontario, Canada) is characterized by treed soil islands interspersed within lichen and moss-covered bedrock outcrops. N mineralization was 2.5-fold and net nitrification was 13-fold higher on an areal basis over bedrock surfaces because of high mineralization rates under lichen and moss patches. The higher average soil temperature in lichen and moss patches could not account for the difference in mineralization rates. Lichens did not provide a significant additional source of N because they did not fix atmospheric N. A refractory conifer litter with a high C:N probably favours the immobilization of N in forest islands. Buried bag and in situ core incubations yielded similar net N mineralization rates but core incubations underestimated net nitrification rates. Both methods did not adequately measure dissolved organic N (DON) production rates because soil disturbance caused high initial DON concentrations. The higher export of mineral N from bedrock surfaces is probably a combination of the lower retention of N in precipitation and leaching of mineralized N from lichen and moss patches. 相似文献
4.
The objective of this study was to examine the chemical structure of the organic matter (SOM) of Oxisols soils in slash and
burn agriculture, in relation to its biological properties and soil fertility. The CP/MAS 13C technique was used to identify the main structural groups in litter and fine roots as SOM precursors; to identify the changes
on the nature of the SOM upon cultivation and the proportion of labile and stable components; and to identify the nature of
the organics present in water extracts (DOC).
Carbohydrates were the main structural components in litter whereas components such as carbonyl C, carboxyl C,O-alkyl C and
alkyl C were more common in SOM. Phenolic C and the degree of aromaticity were similar in litter and SOM. Cultivation resulted
in a small decrease in the relative proportion of carbohydrates in SOM, little change in the levels of O-alkyl C and carbonyl
C, but an increase in carboxyl C, phenolic C and aromaticity of the SOM. The level of alkyl C in soil was higher than the
level of O-alkyl C, indicating the importance of long-chain aliphatics along with lignins in the stabilization of the SOM
in Oxisols. The SOM of Mollisols from the Canadian Prairies differed from the Oxisol, with a generally stronger expression
of aromatic structures, particularly in a cultivated soil in relation to a native equivalent. Carbohydrate components were
the predominant structures in the DOC, indicating their importance in nutrient cycling and vertical translocations in the
Oxisol. 相似文献
5.
Soil organic carbon dynamics: variability with depth in forested and deforested soils under pasture in Costa Rica 总被引:5,自引:2,他引:5
Dynamics of soil organic carbon (SOC) inchronosequences of soils below forests that had beenreplaced by grazed pastures 3–25 years ago, wereinvestigated for two contrasting soil types (AndicHumitropept and Eutric Hapludand) in the Atlantic Zoneof Costa Rica. By forest clearing and subsequentestablishment of pastures, photosynthesis changes froma C-3 to a C-4 pathway. The accompanying changes inC-input and its 13C and 14Csignals, were used to quantify SOC dynamics. C-input from rootturnover at a pasture site was measured by sequentialharvesting and 14C-pulse labelling. With aspatial resolution of 5 cm, data on total SOC,13C and 14C of soil profileswere interpreted with a model that distinguishes threepools of SOC: active C, slow C and passive C,each with a 1-st order decomposition rate(ka, ks and kp). The modelincludes carbon isotope fractionation and depth-dependentdecomposition rates. Transport of C between soillayers was described as a diffusion process, whichaccounts for physical and biotic mixing processes.Calibrated diffusion coefficients were 0.42 cm2yr-1 for the Humitropept and 3.97 cm2yr-1 for the Hapludand chronosequence.Diffusional transport alone was insufficient foroptimal simulation; it had to be augmented bydepth-dependent decomposition rates to explain thedynamics of SOC, 13C and14C. Decomposition rates decreasedstrongly with depth. Upon increased diffusion,differences between calibrated decomposition rates ofSOC fractions between surface soils and subsoilsdiminished, but the concept of depth-dependentdecomposition had to be retained, to obtain smallresiduals between observed and simulated data. At areference depth of 15–20 cm ks was 90 yr-1in the Humitropept and 146 yr-1 in the Hapludand.Slow C contributed most to total organic C in surfacesoils, whereas passive C contributed most below 40 cmdepth. After 18–25 years of pasture, net loss of C was2180 g C m-2 for the Hapludand and 150 g m-2for the Humitropept soil. 相似文献
6.
Despite intensive biogeochemical research during the last thirty years, the relative importance of biological S turnover for the overall SO
4
2–
budget of forested catchments remains uncertain. The objective of the present study was (i) to gain new insight into the S cycle of theLehstenbach catchment (Northeastern Bavaria, Germany) through the analysis of stable isotopes of S and (ii) to differentiate between sites which are hot spots for SO
4
2–
reduction and sites where mineralization and adsorption/desorption processes are more important. The 34S values and SO
4
2–
concentrations of soil solutions, throughfall and groundwater at four different sites as well as runoff of the catchment were measured. The relatively low variability of 34S in throughfall and bulk precipitation was in contrast to the high temporal and spatial variability of 34S in the soil solution. Sulfate in the soil solution of upland sites was slightly depleted in34S compared to input values. This was most likely due to S mineralization. Sulfate in the soil solution from wetland soils was clearly enriched in34S, indicating dissimilatory SO
4
2–
reduction. The observed spatial and temporal patterns of34S turnover and SO
4
2–
concentrations might explain the overall balanced S budget of the catchment. At a time of decreasing anthropogenic deposition SO
4
2–
is currently released from upland soils. Furthermore, mineralization of organic S may contribute to SO
4
2–
release. Wetland soils in the catchment represent a sink for SO
4
2–
due to dissimilatory SO
4
2–
reduction. 相似文献
7.
A multiple enzyme and multisubstrate cycling system is described for the radiometric determination of cholineacetyltransferase (ChAT) activity in crude tissue homogenates. The methods employs [14C]acetate coupled with the enzymes acetate kinase (AK) and phosphotransacetylase (PTA) for the generation of [14C]acetyl CoA. By recycling it was possible to avoid product inhibition of ChAT by CoA, ATP was maintained constant by rephosphorylation of ADP. Kinetics of the individual enzyme reactions were studied and the parameters obtained were used to select appropriate conditions to maintain linearity of varying amounts ChAT activity over a sixty minute time course. The sensitivity of the method is limited only by the specific activity of commercially available isotope labeled acetate.Special issue dedicated to Dr. O. H. Lowry. 相似文献
8.
Coupling 13C natural abundance and 14C pulse labelling enabled us to investigate the dependence of 13C fractionation on assimilate partitioning between shoots, roots, exudates, and CO2 respired by maize roots. The amount of recently assimilated C in these four pools was controlled by three levels of nutrient
supply: full nutrient supply (NS), 10 times diluted nutrient supply (DNS), and deionised water (DW). After pulse labelling
of maize shoots in a 14CO2 atmosphere, 14C was traced to determine the amounts of recently assimilated C in the four pools and the δ13C values of the four pools were measured. Increasing amounts of recently assimilated C in the roots (from 8% to 10% of recovered
14C in NS and DNS treatments) led to a 0.3‰ 13C enrichment from NS to DNS treatments. A further increase of C allocation in the roots (from 10% to 13% of recovered 14C in DNS and DW treatments) resulted in an additional enrichment of the roots from DNS to DW treatments by 0.3‰. These findings
support the hypothesis that 13C enrichment in a pool increases with an increasing amount of C transferred into that pool. δ13C of CO2 evolved by root respiration was similar to that of the roots in DNS and DW treatments. However, if the amount of recently
assimilated C in root respiration was reduced (NS treatment), the respired CO2 became 0.7‰ 13C depleted compared to roots. Increasing amounts of recently assimilated C in the CO2 from NS via DNS to DW treatments resulted in a 1.6‰ δ13C increase of root respired CO2 from NS to DW treatments. Thus, for both pools, i.e. roots and root respiration, increasing amounts of recently assimilated
C in the pool led to a δ13C increase. In DW and DNS plants there was no 13C fractionation between roots and exudates. However, high nutrient supply decreased the amount of recently assimilated C in
exudates compared to the other two treatments and led to a 5.3‰ 13C enrichment in exudates compared to roots. We conclude that 13C discrimination between plant pools and within processes such as exudation and root respiration is not constant but strongly
depends on the amount of C in the respective pool and on partitioning of recently assimilated C between plant pools.
Section Editor: H. Lambers 相似文献
9.
A14C labeling apparatus was developed to permit the labeling of four-year-old Ponderosa pine with14CO2 in the field. The labeling system is a completely closed canopy system with14CO2 monitored by a GM tube ratemeter apparatus. The level of14CO2 corresponding to ambient levels is monitored by a microloggercomputer which controls a14CO2 generating system. The generated14CO2 is mixed in the canopy by circulating the atmosphere with 12V diaphram pumps. The portable system requires little operator
attention.
At approximately monthly intervals over a one-year period two four-year-old Ponderosa pine trees were labeled for three to
five days using this labeling apparatus. After an assimilate distribution period, one tree was excavated and analyzed for14C distribution. During late spring and early summer most of the carbon assimilated (>60%) was found in the active growing
tips and new needles, with little being allocated to the roots (<10%) or woody material (<20%). During mid to late fall there
was an increase in root labeling along with an increase in carbon going to woody material. Over the winter period, most of
the fixed carbon (65%) resided in the older leaves. The early spring labeling period showed another pulse of root labeling
along with some labeling of woody tissues. 相似文献
10.
Organic carbon (C) in lakes originates from two distinct sources—primary production from within the lake itself (autochthonous
supply) and importation of organic matter from the terrestrial watershed (allochthonous supply). By manipulating the 13C of dissolved inorganic C, thereby labeling within-lake primary production, we examined the relative importance of autochthonous
and allochthonous C in supporting bacterial production. For 35 days, NaH13CO3 was added daily to two small, forested lakes. One of the lakes (Peter) was fertilized so that primary production exceeded
total respiration in the epilimnion. The other lake (Tuesday), in contrast, was low in productivity and had high levels of
colored dissolved organic C (DOC). To obtain bacterial C isotopes, bacteria were regrown in situ in particle-free lake water
in dialysis tubes. The contribution of allochthonous C to bacterial biomass was calculated by applying a two-member mixing
model. In the absence of a direct measurement, the isotopic signature of the autochthonous end-member was estimated indirectly
by three different approaches. Although there was excess primary production in Peter Lake, bacterial biomass consisted of
43–46% allochthonous C. In Tuesday Lake more than 75% of bacterial growth was supported by allochthonous C. Although bacteria
used autochthonous C preferentially over allochthonous C, DOC from the watershed contributed significantly to bacterial production.
In combination with results from similar experiments in different lakes, our findings suggest that the contribution of allochthonous
C to bacterial production can be predicted from ratios of chromophoric dissolved organic matter (a surrogate for allochthonous
supply) and chlorophyll a (a surrogate for autochthonous supply). 相似文献
11.
N. V. Pimenov A. M. Zyakun T. S. Prusakova O. N. Lunina M. V. Ivanov 《Microbiology》2008,77(2):224-227
The possibility of measuring the rates of light and dark CO2 assimilation using 13C carbonate was demonstrated on Lake Kichier (Marii El). The application of methods utilizing the stable 13C and the radioactive 14C isotopes resulted in comparable values of the rates of light and dark CO2 fixation. Due to its absolute environmental safety, the method with 13C mineral carbon can be recommended as an alternative to radioisotope methods for qualitative measurements of CO2 fixation rates in aquatic ecosystems. 相似文献
12.
Nathalie Fenner Nicholas J. Ostle Niall McNamara Timothy Sparks Harry Harmens Brian Reynolds Christopher Freeman 《Ecosystems》2007,10(4):635-647
Northern peatlands are important stores of carbon and reservoirs of biodiversity that are vulnerable to global change. However,
the carbon dynamics of individual peatland plant species is poorly understood, despite the potential for rising atmospheric
CO2 to affect the vegetation’s contribution to overall ecosystem carbon function. Here, we examined the effects of 3 years exposure
to elevated CO2 (eCO2) on (a) peatland plant community composition and biomass, and (b) plant carbon dynamics and the production of dissolved organic
carbon (DOC) using a 13CO2 pulse–chase approach. Results showed that under eCO2, Sphagnum spp. cover declined by 39% (P < 0.05) and Juncus effusus L. cover increased by 40% (P < 0.001). There was a concurrent increase in above- and belowground plant biomass of 115% (P < 0.01) and 96% (P < 0.01), respectively. Vascular species assimilated and turned over more 13CO2-derived carbon than Sphagnum spp. (49% greater turnover of assimilated 13C in J. effusus and F. ovina L. leaf tissues compared with Sphagnum, P < 0.01). Elevated CO2 also produced a 66% rise in DOC concentrations (P < 0.001) and an order of magnitude more ‘new’ exudate 13DOC than control samples (24 h after 13CO2 pulse-labelling 2.5 ± 0.5 and 0.2 ± 0.1% in eCO2 and control leachate, respectively, P < 0.05). We attribute the observed increase in DOC concentrations under eCO2 to the switch from predominantly Sphagnum spp. to vascular species (namely J. effusus), leading to enhanced exudation and decomposition (litter and peat). The potential for reduced peatland carbon accretion,
increased DOC exports and positive feedback to climate change are discussed. 相似文献
13.
Weixin Cheng 《Plant and Soil》1996,183(2):263-268
Due to the limitations in methodology it has been a difficult task to measure rhizosphere respiration and original soil carbon decomposition under the influence of living roots. 14C-labeling has been widely used for this purpose in spite of numerous problems associated with the labeling method. In this paper, a natural 13C method was used to measure rhizosphere respiration and original soil carbon decomposition in a short-term growth chamber experiment. The main objective of the experiment was to validate a key assumption of this method: the 13C value of the roots represents the 13C value of the rhizosphere respired CO2. Results from plants grown in inoculated carbon-free medium indicated that this assumption was valid. This natural 13C method was demonstrated to be advantageous for studying rhizosphere respiration and the effects of living roots on original soil carbon decomposition. 相似文献
14.
Ecosystem tracer-level additions would benefit from a stable isotope-labeled source of complex organic molecules. We tested
a method to label tree C with 13C and create a stable isotope tracer for stream dissolved organic carbon (DOC) using tulip poplar (Liriodendron tulipifera L.) seedlings. In 2000, seedlings were grown with 0.82 moles of 13CO2 to assess the distribution and level of 13C enrichment in the tree tissues. In 2001, seedlings were grown with 25 times more 13CO2 to generate tissues with a 13C signal strong enough for a 13C-DOC stream tracer addition. 13C enrichment in the trees varied in each year and by tissue age and type. Tissues formed during labeling (new) were more enriched
in 13C than tissues established prior to the 13CO2 injection (old). Stems were most enriched in 13C in both new and old tissues. A higher percentage of 13CO2 was incorporated into seedlings in 2000 (59% ±1) than 2001 (43% ±0). Percent 13C incorporation among tree tissue types paralleled biomass distributions. Although tree C and 13C were equally soluble in both years, a greater percentage of tree C went into solution in 2001 (30%) than 2000 (20%). The
water-soluble tree C accounted for approximately 12% of the injected 13CO2 and had both humic and polysaccharide components. Results from a whole-stream 13C-DOC tracer addition demonstrated that tree C could be sufficiently labeled with 13CO2 to create a stream DOC isotope tracer with some polymeric constituents. 相似文献
15.
A high yielding synthetic route for methyl 4'-O-methyl-beta-D-cellobioside starting from d-glucose was established. The reaction conditions optimized with nonlabeled materials were used for the synthesis of methyl 4'-O-methyl-13C12-beta-D-cellobioside, a compound having more than 99% 13C enrichment at each of the twelve pyranose carbon atoms. The labeled compound is required to study the hydrogen bond network of cellodextrins and cellulose by CPMAS NMR experiments. 相似文献
16.
Summary A simple technique for identifying protein secondary structures through the analysis of backbone 13C chemical shifts is described. It is based on the Chemical-Shift Index [Wishart et al. (1992) Biochemistry, 31, 1647–1651] which was originally developed for the analysis of 1H chemical shifts. By extending the Chemical-Shift Index to include 13C, 13C and carbonyl 13C chemical shifts, it is now possible to use four independent chemical-shift measurements to identify and locate protein secondary structures. It is shown that by combining both 1H and 13C chemical-shift indices to produce a consensus estimate of secondary structure, it is possible to achieve a predictive accuracy in excess of 92%. This suggests that the secondary structure of peptides and proteins can be accurately obtained from 1H and 13C chemical shifts, without recourse to NOE measurements.Supplementary material is available in the form of a 10-page table (Table S1) describing the exact location of secondary structures in all 20 proteins as determined using the methods described in this paper. Requests for Table S1 should be directed to the authors. 相似文献
17.
Translocation of carbon and nitrogen within a single source-sink unit, comprising a trifoliated leaf, the axillary pod and the subtending internode, and from this unit to the rest of the plant was examined in soybean (Glycine max L. cv. Akishirome) plant by feeding 13CO2 and 15NO3. The plants were grown at two levels of nitrogen in the basal medium, i.e. low-N (2 g N m–2) and high-N (35 g N m–2) and a treatment of depodding was imposed by removing all the pods from the plant, except the pod of the source sink unit, 13 days after flowering. The plants at high-N accumulated more biomass in its organs compared to low-N and pod removal increased the weight of the vegetative organs. When the terminal leaflet of the source-sink unit was fed with 13CO2, almost all of the radioactive materials were retained inside the source-sink unit and translocation to rest of the plants was insignificant under any of the treatments imposed. Out of the13C exported by the terminal leaflet, less than half went into the axillary pod, as the lateral leaflets claimed equal share and very little material was deposited in the petiole. Pod removal decreased 13C export at high-N , but not at low-N. Similar to 13C, the source-sink unit retained all the 15N fed to the terminal leaflet at high-N. At low-N, the major part of 15N partitioning occurred in favour of the rest of the plant outside the source-sink unit, but removal of the competitve sinks from the rest of the plants nullified any partitioning outside the unit. Unlike the situation in 13C, no partitioning of 15N occurred in favour of the lateral leaflets from the terminal leaflet inside the unit. It is concluded that sink demand influences partitioning of both C and N and the translocation of carbon is different from that of nitrogen within a source-sink unit. The translocation of the N is more adjustive to a demand from other sink units compared to the C. 相似文献
18.
In this study, we estimated whether changes in hydrological pathwaysduring storms could explain the large temporal variations of dissolvedorganic carbon (DOC) and nitrogen (DON) in the runoff of threecatchments: a forest and a grassland sub-catchment of 1600m2 delineated by trenches, and a headwater catchment of 0.7km2.The average annual DOC export from the sub-catchments was 185 kg DOCha–1 y–1 for the forest, 108 kg DOCha–1 y–1 for the grassland and 84 kgDOC ha–1 y–1 for the headwatercatchment. DON was the major form of the dissolved N in soil and streamwater. DON export from all catchments was approximately 6 kg Nha–1 y–1, which corresponded to 60% ofthe total N export and to 50% of the ambient wet N deposition. DOC andDON concentrations in weekly samples of stream water were positivelycorrelated with discharge. During individual storms, concentrations andproperties of DOC and DON changed drastically. In all catchments, DOCconcentrations increased by 6 to 7 mg DOC l–1 comparedto base flow, with the largest relative increment in the headwatercatchment (+350%). Concentrations of DON, hydrolysable amino acids, andphenolics showed comparable increases, whereas the proportion ofcarbohydrates in DOC decreased at peak flow. Prediction of DOC and DONconcentrations by an end-member mixing analysis (EMMA) on the base ofinorganic water chemistry showed that changes in water flow pathslargely explained these temporal variability. According to the EMMA, thecontribution of throughfall to the runoff peaked in the initial phase ofthe storm, while water from the subsoil dominated during base flow only.EMMA indicated that the contribution of the DOC and DON-rich topsoil washighest in the later stages of the storm, which explained the highestDOC and DON concentrations as the hydrograph receded. Discrepanciesbetween observed and predicted concentrations were largest for thereactive DOC compounds such as carbohydrates and phenolics. Theyoccurred at base flow and in the initial phase of storms. This suggeststhat other mechanisms such as in-stream processes or a time-variantrelease of DOC also played an important role. 相似文献
19.
D. Schwartz H. de Foresta A. Mariotti J. Balesdent J. P. Massimba C. Girardin 《Oecologia》1996,106(4):516-524
Isolated savannas enclosed by forest are especially abundant in the eastern part of the Congolese Mayombe. They are about 3000 years old, and were more extensive some centuries ago. The boundary between forest and savanna is very abrupt, as a consequence of the numerous savanna fires lit by hunters. Floristic composition and vegetation structure data, organic carbon ratios, 14C and 13C measurements presented here show that forest is spreading over savanna at the present time and suggest that the rate of forest encroachment is is currently between 14 and 75 m per century, and more probably about 20–50 m per century. As most savannas are less than 1 km across, such rates mean, assuming there are no changes in environmental conditions, that enclosed savannas could completely disappear in the Mayombe in about 1000–2000 years. 相似文献
20.
To clarify the unique characteristics of amino acid metabolism derived from glucose in the central nervous system (CNS), we injected [1-13C]glucose intraperitoneally to the rat, and extracted the free amino acids from several kinds of tissues and measured the amount of incorporation of13C derived from [1-13C]glucose into each amino acid using13C-magnetic resonance spectroscopy (NMR). In the adult rat brain, the intensities of resonances from13C-amino acids were observed in the following order: glutamate, glutamine, aspartate, -aminobutyrate (GABA) and alanine. There seemed no regional difference on this labeling pattern in the brain. However, only in the striatum and thalamus, the intensities of resonances from [2-13C]GABA were larger than that from [2,3-13C]aspartate. In the other tissues, such as heart, kidney, liver, spleen, muscle, lung and small intestine, the resonances from GABA were not detected and every intensity of resonances from13C-amino acids, except13C-alanine, was much smaller than those in the brain and spinal cord. In the serum,13C-amino acid was not detected at all. When the rats were decapitated, in the brain, the resonances from [1-13C]glucose greatly reduced and the intensities of resonances from [3-13C]lactate, [3-13C]alanine, [2, 3, 4-13C]GABA and [2-13C]glutamine became larger as compared with those in the case that the rats were sacrificed with microwave. In other tissues, the resonances from [1-13C]glucose were clearly detected even after the decapitation. In the glioma induced by nitrosoethylurea in the spinal cord, the large resonances from glutamine and alanine were observed; however, the intensities of resonances from glutamate were considerably reduced and the resonances from GABA and aspartate were not detected. These results show that the pattern of13C label incorporation into amino acids is unique in the central nervous tissues and also suggest that the metabolic compartmentalization could exist in the CNS through the metabolic trafficking between neurons and astroglia.Abbreviations NMR
nuclear magnetic resonance
- GABA
-aminobutyrate
- GFAP
glial fibrillary acidic protein
Special issue dedicated to Dr. Bernard W. Agranoff. 相似文献