共查询到20条相似文献,搜索用时 46 毫秒
1.
Anne Lorrain Yves-Marie PauletLaurent Chauvaud Nicolas SavoyeAnne Donval Christelle Saout 《Journal of experimental marine biology and ecology》2002,275(1):47-61
There have been several studies where the isotopic composition of organisms has been determined seasonally, but fewer have examined separate organs. In this context, separate organs (e.g. gonad, digestive gland and muscle) of a suspension-feeder, the scallop Pecten maximus, were used to assess seasonal changes of both stable isotopes and biochemical components. Our study used multiple indicators [stable carbon and nitrogen isotope ratios, biochemical components and seston chlorophyll-a (chl a)] to track nutritive activity and energy allocation in P. maximus from the Bay of Brest (France). In addition to seasonal variation in the isotopic composition of P. maximus tissues, we found strong differences in the mean isotopic signatures of different organs. This has serious implications for interpretation of animal diets and potential use in animal physiology. Furthermore, we present evidence that seasonal variations of metabolism will cause changes in the isotopic composition not related to changes in the diet. Interpretation of isotopic data may require consideration of values from several separate organs. Finally, δ15N appears powerful to track metabolite fates in the scallop P. maximus. 相似文献
2.
Bing-You Yang Yong-Gang Xia Juan Pan Yan Liu Qiu-Hong Wang Hai-Xue Kuang 《Phytochemistry Reviews》2016,15(5):771-797
Withanolides are highly oxygenated natural products. These C28 steroids with ergostane-based skeletons functionalized at C-22 and C-26 form six-membered δ-lactone rings. Withanolides containing a δ-lactone side chain often occur in Solanaceae and have a variety of biological activities because of their complicated structures. Characteristic spectroscopic behaviors and biosynthesis of withanolides are conducive to their structural elucidation and “biomimetic synthesis”, respectively. However, the last review to summarize their spectroscopic features and biosynthesis was in 1996. Since then, many withanolides with novel structures have been described by their spectra with biosynthesis investigated with many bioassays. This review surveys δ-lactone withanolides and emphasizes their spectral features, configurations and biosynthetic genes. The period reviewed includes through January 2014. We also include phytochemical species. 相似文献
3.
? Accurate phenotyping remains a bottleneck in breeding for salinity and drought resistance. Here the combined use of stable isotope compositions of carbon (δ13C), oxygen (δ1?O) and nitrogen (δ1?N) in dry matter is aimed at assessing genotypic responses of durum wheat under different combinations of these stresses. ? Two tolerant and two susceptible genotypes to salinity were grown under five combinations of salinity and irrigation regimes. Plant biomass, δ13C, δ1?O and δ1?N, gas-exchange parameters, ion and N concentrations, and nitrate reductase (NR) and glutamine synthetase (GS) activities were measured. ? Stresses significantly affected all traits studied. However, only δ13C, δ1?O, δ1?N, GS and NR activities, and N concentration allowed for clear differentiation between tolerant and susceptible genotypes. Further, a conceptual model explaining differences in biomass based on such traits was developed for each growing condition. ? Differences in acclimation responses among durum wheat genotypes under different stress treatments were associated with δ13C. However, except for the most severe stress, δ13C did not have a direct (negative) relationship to biomass, being mediated through factors affecting δ1?O or N metabolism. Based upon these results, the key role of N metabolism in durum wheat adaptation to salinity and water stress is highlighted. 相似文献
4.
Nader G. Ibrahim Naomi R. Gruenspecht Michael L. Freedman 《Biochemical and biophysical research communications》1978,80(4):722-728
Addition of hemin (5–200 μM) to a rabbit reticulocyte iron-free incubation medium, resulted in a progressive inhibition of heme synthesis as measured by incorporation of (14C)-glycine. In contrast when (14C) δ-aminolevulinic acid incorporation into heme was studied, significant inhibition below that of the (14C)-glycine control only occurred with hemin concentrations greater than 100 μM. Hemin progressively inhibited cellular and mitochondrialδ-aminolevulinic acid synthetase activity, as well as cellular δ-aminolevulinic acid dehydratase activity. The results indicated that elevated levels of hemin initially control heme synthesis by feedback inhibition at the rate-limiting enzyme of heme synthesis, δ-aminolevulinic acid synthetase. Hemin inhibition of δ-aminolevulinic acid dehydratase is only significant for the entrire heme synthetic pathway when greater than one-third of this enzyme's activity is inhibited. 相似文献
5.
The δ18O and δD composition of water pools (leaf, root, standing water and soil water) and fluxes [transpiration (T), evaporation (E)] were used to understand ecohydrological processes in a managed Typha latifolia L. freshwater marsh. We observed isotopic steady‐state T and deep rooting in Typha. The isotopic mass balance of marsh standing water showed that E accounted for 3% of the total water loss, T accounted for 17% and subsurface drainage (D) accounted for the majority (80%). There was a vertical gradient in water vapour content and isotopic composition within and above the canopy sufficient for constructing an isotopic mass balance of water vapour during some sampling periods. During these periods, the proportion of T in evapotranspiration (T/ET) was between 56 ± 17% and 96 ± 67%, and the estimated error was relatively high (>37%) because of non‐local, background sources in vapour. Independent estimates of T/ET using eddy covariance measurements yielded similar mean values during the Typha growing season. The various T/ET estimates agreed that T was the dominant source of marsh vapour loss in the growing season. The isotopic mass balance of water vapour yielded reasonable results, but the mass balance of standing water provided more definitive estimates of water losses. 相似文献
6.
W. H. Elliott 《The Biochemical journal》1960,74(1):90-94
7.
Birgit Geueke Milena E. Miska Thomas Poiger Daniel Rentsch Rup Lal Christof Holliger Hans-Peter E. Kohler 《Applied and environmental microbiology》2013,79(19):6180-6183
δ-Hexachlorocyclohexane (δ-HCH), one of the prevalent isomers of technical HCH, was enantioselectively dehydrochlorinated by the dehydrochlorinases LinA1 and LinA2 from Sphingobium indicum B90A to the very same δ-pentachlorocyclohexene enantiomer. Racemic δ-pentachlorocyclohexene, however, was transformed with opposite enantioselectivities by the two enzymes. A transformation pathway based on an anti-1,2-elimination, followed by a syn-1,4-elimination and a subsequent syn-1,2-elimination is postulated. 相似文献
8.
Nada Horvatin?i? Ines Krajcar Broni?Bogomil Obeli? 《Palaeogeography, Palaeoclimatology, Palaeoecology》2003,193(1):139-157
We studied Holocene speleothems and tufa samples collected in numerous caves and rivers in the Dinaric Karst of Croatia, Slovenia, Bosnia and Herzegovina, as well as Serbia and Montenegro. Differences in the formation process of tufa and speleothems are discussed in the context of their isotopic composition (14C, 13C and 18O), as well as the chemistry of surface water (rivers, lakes) and drip water (in caves). The physical and chemical parameters monitored in the surface water (tufa precipitation) and drip water (speleothem precipitation) show that more stable conditions accompany speleothem rather than tufa formation. This is particularly obvious in the water temperature variations (2-22°C in surface water and 7-12°C in drip water) and in saturation index variation (3-11 in surface water and 1-6 in drip water). The range of 14C ages recorded by Holocene speleothems (∼12?000 yr) is wider by several thousands years than that of Holocene tufa samples (∼6000 yr). δ13C values for tufa samples range from −12‰ to −6‰ and for speleothem samples from −12‰ to +3‰ reflecting higher soil carbon and/or vegetation impact on the process of tufa than on speleothem formation. The differences in δ18O values of tufa and speleothem samples from different areas reflect different temperature conditions and differing isotopic composition in the water. The study shows that speleothems from the Dinaric Karst can be used as global palaeoclimatic records, whereas tufa records changes in the local palaeoenvironment. 相似文献
9.
We tested the reliability of herbivore faecal δ13C and δ15N values for reconstructing diet through review of an extensive database derived from a 3-year study of ungulates in South Africa's Kruger National Park. Faeces are a useful material for stable isotope studies of diet because they record dietary turnover at very short time scales, and because sampling is non-invasive. However, the validity of faecal isotope proxies may be questioned because they represent only undigested food remains. Results from Kruger Park confirm that free-ranging browsers have faecal δ13C consistent with C3 feeding, grazer faeces are C4, and mixed-feeder faeces intermediate. Although the respective ranges do not overlap, there is significant variation in faecal δ13C of browsers and grazers (~2.0–4.0‰) across space and through time. We demonstrate that most (~70%) of this variation can be ascribed to corresponding patterns of variation in the δ13C of C3 and C4 plants, respectively, re-enforcing the fidelity of faecal isotope proxies for diet but highlighting a need for mixing models that control for variations in plant δ13C in order to achieve accurate diet reconstructions. Predictions for the effects of climate (rainfall) and ecophysiology on 15N-abundance variations in mammals do not persist in faeces. Rather, faecal δ15N tracks changes in plant δ15N, with further fractionation occurring primarily due to variations in dietary protein (reflected by %N). Controlling for these effects, we show that a dual-isotope multiple source mixing model (Isosource) can extend diet reconstructions for African savanna herbivores beyond simplified C3/C4 distinctions, although further understanding of variations in mammal δ15N are needed for greater confidence in this approach. 相似文献
10.
Sea lion and seal populations in Alaskan waters underwent various degrees of decline during the latter half of the twentieth century and the cause(s) for the declines remain uncertain. The stable carbon (13C/12C) and nitrogen (15N/14N) isotope ratios in bone collagen from wild Steller sea lions (Eumetopias jubatus), northern fur seals (Callorhinus ursinus) and harbor seals (Phoca vitulina) from the Bering Sea and Gulf of Alaska were measured for the period 1951-1997 to test the hypothesis that a change in trophic level may have occurred during this interval and contributed to the population declines. A significant change in '15N in pinniped tissues over time would imply a marked change in trophic level. No significant change in bone collagen '15N was found for any of the three species during the past 47 years in either the Bering Sea or the Gulf of Alaska. However, the 15N in the Steller sea lion collagen was significantly higher than both northern fur seals and harbor seals. A significant decline in '13C (almost 2 over the 47 years) was evident in Steller sea lions, while a declining trend, though not significant, was evident in harbor seals and northern fur seals. Changes in foraging location, in combination with a trophic shift, may offer one possible explanation. Nevertheless, a decrease in '13C over time with no accompanying change in '15N suggests an environmental change affecting the base of the foodweb rather than a trophic level change due to prey switching. A decline in the seasonal primary production in the region, possibly resulting from decreased phytoplankton growth rates, would exhibit itself as a decline in '13C. Declining production could be an indication of a reduced carrying capacity in the North Pacific Ocean. Sufficient quantities of optimal prey species may have fallen below threshold sustaining densities for these pinnipeds, particularly for yearlings and subadults who have not yet developed adequate foraging skills. 相似文献
11.
Regional food web studies that fail to account for small-scale isotopic variability can lead to a mismatch between an organism’s
inferred and true trophic position. Misinterpretation of trophic status may result, substantially limiting spatial and temporal
comparability of food web studies. We sampled several carbon sources and consumers in a nested design to assess the variability
of food web members across small spatial scales (100 s of m to several km) in regions around the Windmill Islands and Vestfold
Hills in East Antarctica. For carbon sources, δ13C in sea ice POM was particularly variable between locations (km apart) and between sites (100 s of m apart) with replicate
samples varying by up to 16‰. Macroalgae δ13C was less variable (replicate samples ranging up to 6.9‰ for the red alga Iridaea cordata), yet still differed between locations. Sediment POM and pelagic POM were the least variable, displaying minimal differences
between locations or sites for δ13C and δ15N. Three out of eight consumers were significantly different between locations for δ13C, and five out of eight for δ15N, with the fish Trematomus bernacchii the most variable for both δ13C and δ15N. At smaller scales, the amphipod Paramorea walkeri showed significant variation between sites in δ13C but not in δ15N. We attribute small-scale variability to the dynamic physical environment for carbon sources in coastal systems and a close
coupling of diet to habitat for consumers. We highlight the need to account for small-scale spatial variation in sampling
designs for regional food web studies. 相似文献
12.
A. Hope Jahren Monica C. Byrne Heather V. Graham Leonel S.L. Sternberg Roger E. Summons 《Palaeogeography, Palaeoclimatology, Palaeoecology》2009,271(1-2):96-103
The extensive vertical exposure (> 150 m) of terrestrial sediments on Axel Heiberg Island, which contain thick fossiliferous lignites, presents an exceptional opportunity to follow the establishment and re-establishment of Arctic Metasequoia forests during the middle Eocene. We compared δD values in n-alkanes of chain length 23, 25, 27 and 29 with δ18O values in phenylglucosazone (P-G) derived from α-cellulose; we also analyzed %-abundance of ferns, gymnosperms and angiosperms using pollen and spores isolated from each lignite. Our results showed that forest composition was altered upon uplift, as gymnosperms became more abundant within the relatively well-drained upland sediments. This was also reflected in the small (1‰), but significant, increase in the δ13C value of TOM from lowland to upland environments. However, neither the δD values of n-alkanes nor the δ18O in P-G were statistically different in the upland sediments, as compared to the lowland sediments; from this we inferred that the oxygen isotope signature of environmental water available to the forests for plant growth was relatively uniform throughout the time of the fossil forests. The δD value of environmental water implied by both n-alkanes and P-G ranged from ? 168 to ? 131% and was considerably enriched compared to all environmental water samples available from the modern Arctic region (< ? 180%). In addition to indicating a warmer Eocene Arctic, subject to meteoric transport patterns different from today's, these results argue against the presence of an Eocene polar ice cap. 相似文献
13.
Geoffrey J. Osgood Brian Timmer Kieran Cox Francis Juanes Julia K. Baum 《Journal of fish biology》2020,96(4):1060-1064
Stable nitrogen (δ15N) and carbon (δ13C) isotope ratios from muscle, liver and yolk were analysed from the mother and embryos of an ovoviviparous shark, Hexanchus griseus. Embryonic liver and muscle had similar δ15N and δ13C ratios or were depleted in heavy isotopes, compared to the same maternal somatic and reproductive yolk tissues, but no relationship existed between δ15N or δ13C and embryo length, as expected, because a switch to placental nourishment is lacking in this species. This study expands the understanding of maternal nourishment and embryonic stable isotope differences in ovoviviparous sharks. 相似文献
14.
Stable isotope analyses are often used to calculate relative contributions of multiple food sources in an animals diet. One prerequisite for a precise calculation is the determination of the diet-tissue fractionation factor. Isotopic ratios in animals are not only affected by the composition of the diet, but also by the amount of food consumed. Previous findings regarding the latter point are controversial. As stable isotope analyses have often been used to investigate aquatic food webs, an experiment with carp (Cyprinus carpio L.) was carried out to test the influence of the feeding level and individual metabolic rate on 13C and 15N values of the whole body. After an initial phase, 49 carp were assigned randomly to four groups and fed the same diet at different levels for 8 weeks. For 15 fish, the energy budget was determined by indirect calorimetry. Feed and individual fish were analysed for their proximate composition, gross energy content and 13C and 15N values. 13C and 15N values differed significantly at different feeding levels. While 13C values of the lipids and 15N values decreased with increasing feeding rate, 13C values of the lipid-free matter showed a non-linear pattern. Data obtained from fish held in the respirometric system revealed a relationship between 13C values and the percentage retention of metabolizable energy. Our results show that reconstructing the diets of fish from the isotopic ratios when the feeding level and individual metabolic rates are unknown would introduce an error into the data used for back-calculation of up to 1 for both 13C and 15N values and may have substantial effects on the results of calculated diets. As other workers have pointed out, the development and application of stable isotopes to nutritional ecology studies is a field in its infancy and gives rise to erroneous, misleading results without nutritional, physiological and ecological knowledge. 相似文献
15.
1. delta-Tocotrienol (8-methyltocotrienol) was isolated from the latex of Hevea brasiliensis. This new member of the tocopherol family is a pale-yellow oil at room temperature. 2. The properties of delta-tocotrienol are very similar to those of delta-tocopherol and the small differences can be explained by the change in side chain. 3. The ultraviolet and infrared spectra of delta-tocotrienol were determined and a conversion factor for use with the Emmerie-Engel reaction was worked out. Details are given for the chromatography of delta-tocotrienol on thin layers (adsorption and partition) and reversed-phase paper, and the nitroso derivatives were formed. 4. An ethyl carbonate ester of delta-tocotrienol was prepared and compared with a similar ester of delta-tocopherol. 5. Hydroxymethylation of delta-tocotrienol followed by reduction gave beta-tocotrienol as a major product. 相似文献
16.
Reviews in Fish Biology and Fisheries - Stable isotope analysis (SIA) is widely used to assess animal diet and movements, requiring accurate estimates of trophic discrimination factors (TDFs).... 相似文献
17.
Joram Piatigorsky Barbara Norman Raymond E. Jones 《Journal of molecular evolution》1987,25(4):308-317
A cloned chicken delta-crystallin cDNA was used to identify two putative delta-crystallin genes in the duck by Southern blot hybridization. A DNA fragment containing most of one of these genes was isolated from a library made in bacteriophage lambda Charon 28A containing genomic DNA from 14-day-old embryonic ducks. Electron microscopy, partial gene sequencing, primer extension analysis using duck mRNA, and comparison with the well-characterized chicken delta-crystallin genes suggest that our cloned duck delta-crystallin gene, like the chicken delta-crystallin genes, is 8-10 kb long and contains 17 exons. Hybridization and sequencing data show great similarity between the homologous 5' untranslated and coding exons of the duck and chicken delta-crystallin genes. Overall, the homologous introns also appear to have approximately 30% sequence similarity, and have been subject to deletion/insertion events. Our partial characterization of duck delta-crystallin gene sequences suggests that this avian and reptilian crystallin family has been conserved during evolution, as have the other crystallin gene families that are expressed in the eye lens. 相似文献
18.
Jonathan J. Derbridge Jerod A. Merkle Melanie E. Bucci Peggy Callahan John L. Koprowski Jean L. Polfus Paul R. Krausman 《PloS one》2015,10(3)
Stable isotope analysis of diet has become a common tool in conservation research. However, the multiple sources of uncertainty inherent in this analysis framework involve consequences that have not been thoroughly addressed. Uncertainty arises from the choice of trophic discrimination factors, and for Bayesian stable isotope mixing models (SIMMs), the specification of prior information; the combined effect of these aspects has not been explicitly tested. We used a captive feeding study of gray wolves (Canis lupus) to determine the first experimentally-derived trophic discrimination factors of C and N for this large carnivore of broad conservation interest. Using the estimated diet in our controlled system and data from a published study on wild wolves and their prey in Montana, USA, we then investigated the simultaneous effect of discrimination factors and prior information on diet reconstruction with Bayesian SIMMs. Discrimination factors for gray wolves and their prey were 1.97‰ for δ13C and 3.04‰ for δ15N. Specifying wolf discrimination factors, as opposed to the commonly used red fox (Vulpes vulpes) factors, made little practical difference to estimates of wolf diet, but prior information had a strong effect on bias, precision, and accuracy of posterior estimates. Without specifying prior information in our Bayesian SIMM, it was not possible to produce SIMM posteriors statistically similar to the estimated diet in our controlled study or the diet of wild wolves. Our study demonstrates the critical effect of prior information on estimates of animal diets using Bayesian SIMMs, and suggests species-specific trophic discrimination factors are of secondary importance. When using stable isotope analysis to inform conservation decisions researchers should understand the limits of their data. It may be difficult to obtain useful information from SIMMs if informative priors are omitted and species-specific discrimination factors are unavailable. 相似文献
19.
Rinku Pandey Del Lucent Kirti Kumari Pooja Sharma Rup Lal John G. Oakeshott Gunjan Pandey 《PloS one》2014,9(7)
Organochlorine insecticide hexachlorocyclohexane (HCH) has recently been classified as a ‘Persistent Organic pollutant’ by the Stockholm Convention. The LinB haloalkane dehalogenase is a key upstream enzyme in the recently evolved Lin pathway for the catabolism of HCH in bacteria. Here we report a sequence-structure-function analysis of ten naturally occurring and thirteen synthetic mutants of LinB. One of the synthetic mutants was found to have ∼80 fold more activity for β- and δ-hexachlorocyclohexane. Based on detailed biophysical calculations, molecular dynamics and ensemble docking calculations, we propose that the latter variant is more active because of alterations to the shape of its active site and increased conformational plasticity. 相似文献
20.
《Life sciences》1994,55(4):PL79-PL84
The selective δ2 receptor antagonist Naltriben (NTB) has played an important role in the identification of subtypes of the δ opioid receptor, termed δ1 and δ2, and their role in antinociception. However, the majority of these studies have been conducted in the mouse. The present study determined the opioid receptor selectivity of subcutaneously (s.c.) administered NTB in the rat. Five minute pretreatment with 1 mg/kg s.c. NTB antagonized the increase in TFL produced by i.t. administration of equieffective doses of the δ2 receptor agonist [D-Ala2, Glu4]deltorphin (DELT) or the δ1 receptor agonist [D-Pen2, D-Pen5]enkephalin (DPDPE), but did not antagonize the μ receptor agonist [D-Ala2, MePhe4, Gly-ol5]enkephalin (DAMGO). These data confirm previous reports that NTB is a selective δ opioid receptor antagonist. However, this dose of NTB antagonized DELT and DPDPE to an equivalent extent, suggesting that its selectivity for the δ2 receptor is not maintained after s.c. administration in the rat. A lower dose of NTB (0.56 mg/kg s.c.) was ineffective. When the dose of NTB was increased to 3 mg/kg s.c. the antagonism of DELT and of DPDPE was unexpectedly lost. Pretreatment with the κ receptor antagonist nor-binaltorphimine (nor-BNI) partially restored the antagonism of DELT, but not DPDPE by this dose of NTB and did not modify the antagonism of DAMGO by NTB. These data suggest that high doses of NTB have κ receptor agonist-like activity and support the proposal that κ opioid agonists diminish the actions of δ receptor antagonists. They also suggest that nor-BNI-sensitive κ opioid receptors interact with δ2, but not δ1 opioid receptors in the spinal cord. 相似文献