Uptake Rate of Tracer MetalIons by a?Lycium barbaruma?Somatic Embryogenesis

The callus of medical plant Lycium barbarum L. in Ningxia was used as the materials for inducing somatic embryogenesis, and multitracer technique and γ-ray energy spectrum analysis were used for studying the rates of uptake of several tracer metal ions during embryogenesis. The results were: 1) Of 23 radionuclides, only 16 (Mn-52, Zn-65, Co-56, Co-60, As-74, Se-75, mTc-95, Rh-99, V-48, Rb-83, Rb-84, Sr-85, Y-87, Y-88, Zr-88 and Zr-89) were selectively absorbed, the other 7 (Be-7, Tc-96, Ru-97, mRh-101, Sc-46, Ga-67 and Cr-51) were not absorbed. 2) The rates of absorption of different metal ions were different at the same developmental stage. In 10 day culture, the rates of uptake of most metal ions were 5%/g, but that of Se-75, Ab-83, Sr-85 and Zr-89 were 10%-30%/g. The rates of absorption of the same metal ion were different at the same developmental stage, e.g. the rates of uptake of Se-75 were increasing in the course of development, two peaks of absorption appeared in the 5-7th and 15-20th days, being 14%/g and 20%/g. But, around 10th, the uptake rate decreased somewhat. The maximum uptake rate was 20%/g in 20th days. The uptake rates of some metal ions were with the somtimes keeping pace differentiation of embryonic cells. But sometimes not and division. The tendencies of the uptake rates of Se-75, Rb-83, Sr-85, Co-56 and V-48 were similar, indicating that the metal ions were accumulated in the callus during somatic embryogenesis. The uptake rate of Mn-52 was not only similar to other elements, but the variation was like normal distribution.     

Fate of nitrogen applied as Azolla and blue-green algae (Cyanobacteria) in waterlogged rice soils—a15N tracer study

Summary ¹⁵N tracer was used to detect the extent to which nitrogen of appliedAzolla caroliniana, Anabaena variabilis andNostoc muscorum was available for assimilation by the growing rice plants in pots under 4 cm flood water for 60 days. The rate of release of nitrogen from the above biofertilizers, the amount of nitrogen remaining in the soils and the amount that was lost from the soils during this period were also examined. Previously¹⁵N-labelled biomass of Azolla, Anabaena and Nostoc to provide 40 mg N was mixed thoroughly with 0.5 kg silt loam Bangladesh soil (Sonatola series) in each of three pots used for a single treatment. Each pot received four 16 days old IR8 rice seedlings. A parallet set of experiments was conducted without rice plants.It was found that nitrogen uptake in the rice plants was increased by 91, 176 and 215% on using Azolla, Anabaena and Nostoc which resulted in increased total dry matter yields (shoot plus root) of 74, 105 and 125%, respectively. Of the total¹⁵N applied at the start, 26, 49 and 53% was released from Azolla, Anabaena and Nostoc; about 7, 14 and 13% was lost by denitrification and 74, 51 and 47% remained in the soils as the undecomposed part of the biofertilizers, respeciively, after 60 days. Of 15.76, 22.72 and 25.92 mg N assimilated by the rice plants, 48, 61 and 62% was supplied by Azolla, Anabaena and Nostoc, respectively. The rest was obtained from the soil used.In the absence of the rice plants 30, 43 and 45% of applied¹⁵N of Azolla, Anabaena and Nostoc was released, respectively, in 60 days of which 93–96% was lost as N₂ through denitrification.     

不同种类氮素对苋菜硝酸盐积累及分配的影响

应用¹⁵N核素示踪技术,研究了不同氮肥种类对苋菜硝酸盐积累与分配的关系及氮素的去向。结果表明:（1）苋菜可食部分中茎较叶更易富集硝酸盐,茎中硝酸盐含量为叶中的1.5倍左右,施用硝态氮肥苋菜叶与茎中的硝酸盐含量都偏高。（2）苋菜硝酸盐主要来源于土壤,达到80%以上,而来自肥料部分不足20%。（3）苋菜施用尿素其肥料利用率达到46.27%,土壤残留氮素达到17.01%,均高于硫铵与硝酸钠,尿素损失率为40.32%,远低于硫铵与硝酸钠,表明施用尿素有利于土壤氮素储量的保持和提高。     

Synthesis of an acromelic acid A analog-based 11C-labeled PET tracer for exploration of the site of action of acromelic acid A in allodynia induction

A novel ¹¹C-labeled PET (positron emission tomography) tracer, which was designed based on the (phenylthio)pyrrolidine derivative that can competitively block the acromelic acid A-induced allodynia, was synthesized. A protocol in which methylation by palladium-mediated coupling of the boronate derivative with [¹¹C]CH₃I and deprotection of the protected amino acid moiety are successively performed in one-pot within 5 min was established for the synthesis of the tracer. The tracer is potentially useful as a tool to investigate the mode of action of acromelic acid A in the induction of allodynia.     

The use of stable-isotopically labeled oleic acid to interrogate lipid assembly in vivo: assessing pharmacological effects in preclinical species

The use of stable isotopically labeled substrates and analysis by mass spectrometry have provided substantial insight into rates of synthesis, disposition, and utilization of lipids in vivo. The information to be gained from such studies is of particular benefit to therapeutic research where the underlying causes of disease may be related to the production and utilization of lipids. When studying biology through the use of isotope tracers, care must be exercised in interpreting the data to ensure that any response observed can truly be interpreted as biological and not as an artifact of the experimental design or a dilutional effect on the isotope. We studied the effects of dosing route and tracer concentration on the mass isotopomer distribution profile as well as the action of selective inhibitors of microsomal tri-glyceride transfer protein (MTP) in mice and diacylglycerol acyltransferase 1 (DGAT1) in nonhuman primates, using a stable-isotopically labeled approach. Subjects were treated with inhibitor and subsequently given a dose of uniformly 13C-labeled oleic acid. Samples were analyzed using a rapid LC-MS technique, allowing the effects of the intervention on the assembly and disposition of triglycerides, cholesteryl esters, and phospholipids to be determined in a single 3 min run from just 10 μl of plasma.     

15N stable isotope labelling of slugs (Gastropoda: Pulmonata)

Stable isotope tracers are a promising tool for investigating the ecology of terrestrial slugs, including predator‐prey relationships, migration behaviour, nutrient turnover and dietary routing. The objective of the present feasibility study was to label two economically important slug groups, Deroceras reticulatum and keeled slugs (families Limacidae and Milacidae, respectively), with the stable isotope ¹⁵N under controlled laboratory conditions. Significant isotopic enrichment in slug tissue was detected after 4 days and persisted for at least 10 days after slugs had been fed on ¹⁵N enriched food for a period of 15 days. The time course of ¹⁵N uptake into slug tissues and its relation to food consumption were well described mathematically. Estimated mean ¹⁵N assimilation efficiencies from labelled maize mixed with unlabelled wheat bran were 30% and 38%, respectively, for the species groups studied. These findings suggest that slugs can be readily and efficiently labelled and that it is feasible to devise protocols for producing large numbers of isotopically labelled slugs for use in ecological studies. A simple method is described for the collection and analysis of cutaneous mucus from individual slugs which can be used to test uniformity of isotopic labelling.     

施肥和秸秆还田对黑土农田土壤剖面养分分布的影响

以东北黑土区玉米田为对象,利用田间原位小区试验,结合亮蓝染色示踪技术,研究不施肥(CK)、常量化肥(T1)、化肥减施秸秆还田(T2)、化肥减施秸秆还田配施有机肥(T3)条件下,土壤剖面的养分分布特征及其对施肥措施和秸秆还田的响应机理.结果 表明:与CK相比,各施肥处理均显著增加了玉米产量,但不同处理之间耕层土壤全量养分...     

Spring time production of bottom ice algae in the landfast sea ice zone at Barrow, Alaska

The primary production of bottom ice algae is an important food source for sympagic, pelagic and benthic organisms in the Arctic Ocean as well as Antarctic Ocean. Using ¹³C-¹⁵N isotope tracers, the recent ice algal production at Barrow during the spring season was lower in 2003 than three decades ago, although the maximum chlorophyll-a concentration for the bottom ice algae was similar to the values from previous studies. Estimated recent new and total production rates of the ice algae were 0.8 g C m^- 2 yr^- 1 and 2.0 g C m^- 2 yr^- 1 respectively, while the rates of water column phytoplankton were 0.2 g C m^- 2 yr^- 1 and 0.7 g C m^- 2 yr^- 1 for the spring sampling period in 2003. The ice algae contributed 74% of the pelagic primary production under the landfast sea ice at Barrow before the phytoplankton spring bloom. At the end of the season in 2003, a high carbon allocation of lipids in the ice algae was found. Three possible explanations- nutrient depletion, increasing light, and/or changes in species composition- were suggested for the high carbon incorporation into lipids. This high lipid synthesis of the bottom ice algae might be significant to zooplankton and benthic fauna grazers because lipids are the most energy dense biomolecules.     

Al-toxicity studies in yeast using gallium as an aluminum analogue

Aluminum (Al) is normally present in soils as the insoluble, harmless Al2O3. The highly toxic Al3+ and AlOH2+ monomeric cations are formed in acid soils but there is little consensus on the physiological basis of Al toxicity in plants. A major factor that has retarded progress in understanding aluminum toxicity in vascular plants is the lack of a convenient radioisotope for Al. Yeast and vascular plants share similar membrane transport mechanisms and so yeast (Saccharomyces cerevisiae) provides a convenient model system for studies of Al-toxicity. Al and gallium (Ga) have closely similar toxic effects on the yeast cells (Ki approximately 100 mmol m-3) and Ga3+ and Al3+, respond similarly to pH and are both reversible by a chelation agent (citric acid). We tested the feasibility of using 67Ga radioisotope as a tracer for Al transport with the view of using it to investigate the mechanism of Al uptake and toxicity in plants. The clinically available 67Ga citrate is unsuitable to use as an aluminum analogue because the chelated form is not toxic. Arrangements need to be made for it to be supplied as 67GaCl3. Large amounts of 67Ga rapidly bind to the cell wall of yeasts with a t 1/2 of approximately 1 s. There is a very slow net uptake of 67Ga into a second phase, presumably the cytoplasm. Uptake into the slow phase has a Vmax of only approximately 16 +/- 4 pmol m(-2) s(-1) (n = 16). The Km of 67Ga uptake could not be precisely determined but is below 100 mmol m(-3) (45 +/- 42 mmol m(-3), n = 16).