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1.
Emile CL. Marnette Harm Houweling Herman Van Dam Jan Willem Erisman 《Biogeochemistry》1993,23(2):119-144
The chemical composition of surface waters of two Dutch moorland pools and of incident precipitation, was monitored from 1982
to 1990. For this period, sulfur and water budgets were calculated using a hydrochemical model developed for well-mixed non-stratifying
lakes. Total atmospheric deposition of S decreased significantly after 1986 at both locations. A model describing the sulfur
budget in terms of input, output and reduction/oxidation processes predicted a fast decrease of pool water SO4
2− concentrations after a decrease of atmospheric input. However, SO4
2− concentrations in the surface water was lowered only slightly or remained constant. Apparently a source within the lake caused
the unexpectedly high SO4
2− concentrations. The possible supply of SO4
2− from the sediment through regulation by (K-)Al-SO4 containing minerals or desorption of SO4
2− from positively charged surfaces in the sediment was evaluated. Solubility calculations of pore water with respect to alunite,
basaluminite and jurbanite indicated that SO4
2− concentration was not regulated by these minerals. It is suggested here (1) that desorption of SO4
2− from peaty sediments may account for the estimated SO4
2− supply provided that the adsorption complex is periodically recharged by partial oxidation of the upper bottom sediments
and (2) that because of exposure of a part of the pool bottom to the atmosphere during dry summers and subsequent oxidation
of reduced S, the amount of SO4
2− may be provided which complements the decreasing depositional SO4
2− input. In future research these two mechanisms need to be investigated. 相似文献
2.
Sulfate reduction and S-oxidation in a moorland pool sediment 总被引:3,自引:2,他引:1
In an oligotrophic moorland pool in The Netherlands, S cycling near the sediment/water boundary was investigated by measuring (1) SO4
2– reduction rates in the sediment, (2) depletion of SO4
2– in the overlying water column and (3) release of35S from the sediment into the water column. Two locations differing in sediment type (highly organic and sandy) were compared, with respect to reduction rates and depletion of SO4
2– in the overlying water.Sulfate reduction rates in sediments of an oligotrophic moorland pool were estimated by diagenetic modelling and whole core35SO4
2– injection. Rates of SO4
2– consumption in the overlying water were estimated by changes in SO4
2– concentration over time in in situ enclosures. Reduction rates ranged from 0.27–11.2 mmol m–2 d–1. Rates of SO4
2– uptake from the enclosed water column varied from –0.5, –0.3 mmol m–2 d–1 (November) to 0.43–1.81 mmol m–2 d–1 (July, August and April). Maximum rates of oxidation to SO4
2– in July 1990 estimated by combination of SO4
2– reduction rates and rates of in situ SO4
2– uptake in the enclosed water column were 10.3 and 10.5 mmol m–2 d–1 at an organic rich and at a sandy site respectively.Experiments with35S2– and35SO4
2– tracer suggested (1) a rapid formation of organically bound S from dissimilatory reduced SO4
2– and (2) the presence of mainly non SO4
2–-S derived from reduced S transported from the sediment into the overlying water. A35S2– tracer experiment showed that about 7% of35S2– injected at 1 cm depth in a sediment core was recovered in the overlying water column.Sulfate reduction rates in sediments with higher volumetric mass fraction of organic matter did not significantly differ from those in sediments with a lower mass fraction of organic matter.Corresponding author 相似文献
3.
MARTIN CLÉMENT CAROLINE CHAMBERLAND JACQUELINE PÉRODIN RICHARD LEDUC GAÉTAN GUILLEMETTE EMANUEL ESCHER 《Journal of receptor and signal transduction research》2013,33(5-6):417-433
Several models of activation mechanisms were proposed for G protein-coupled receptors (GPCRs), yet no direct methods exist for their elucidation. The availability of constitutively active mutants has given an opportunity to study active receptor conformations within acceptable limits using models such as the angiotensin II type 1 (AT1)1 receptor mutant N111G-hAT1 which displays an important constitutive activity. Recently, by using methionine proximity assay, we showed for the hAT1 receptor that TMD III, VI, and VII form the ligand-binding pocket of the C-terminal amino acid of an antagonistic AngII analogue. In the present contribution, we investigated whether the same residues would also constitute the ligand-binding contacts in constitutively activated mutant (CAM) receptors. For this purpose, the same Met mutagenesis strategy was carried out on the N111G double mutants. Analysis of 43 receptors mutants in the N111G-hAT1 series, photolabeled and CNBr digested, showed that there were only subtle structural changes between the wt-receptor and its constitutively active form. 相似文献
4.
Oylum Erkus Victor CL de Jager Maciej Spus Ingrid J van Alen-Boerrigter Irma MH van Rijswijck Lucie Hazelwood Patrick WM Janssen Sacha AFT van Hijum Michiel Kleerebezem Eddy J Smid 《The ISME journal》2013,7(11):2126-2136
Maintenance of a high degree of biodiversity in homogeneous environments is poorly understood. A complex cheese starter culture with a long history of use was characterized as a model system to study simple microbial communities. Eight distinct genetic lineages were identified, encompassing two species: Lactococcus lactis and Leuconostoc mesenteroides. The genetic lineages were found to be collections of strains with variable plasmid content and phage sensitivities. Kill-the-winner hypothesis explaining the suppression of the fittest strains by density-dependent phage predation was operational at the strain level. This prevents the eradication of entire genetic lineages from the community during propagation regimes (back-slopping), stabilizing the genetic heterogeneity in the starter culture against environmental uncertainty. 相似文献
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6.
GUILLAUME TCHERKEZ RUDI SCHÄUFELE SALVADOR NOGUÉS CLÉMENT PIEL ARNOUD BOOM GARY LANIGAN CÉCILE BARBAROUX CATARINA MATA SLIMAN ELHANI DEBBIE HEMMING CHRISTINA MAGUAS DAN YAKIR FRANZ W. BADECK HOWARD GRIFFITHS HANS SCHNYDER JALEH GHASHGHAIE 《Plant, cell & environment》2010,33(6):900-913
While there is currently intense effort to examine the 13C signal of CO2 evolved in the dark, less is known on the isotope composition of day‐respired CO2. This lack of knowledge stems from technical difficulties to measure the pure respiratory isotopic signal: day respiration is mixed up with photorespiration, and there is no obvious way to separate photosynthetic fractionation (pure ci/ca effect) from respiratory effect (production of CO2 with a different δ13C value from that of net‐fixed CO2) at the ecosystem level. Here, we took advantage of new simple equations, and applied them to sunflower canopies grown under low and high [CO2]. We show that whole mesocosm‐respired CO2 is slightly 13C depleted in the light at the mesocosm level (by 0.2–0.8‰), while it is slightly 13C enriched in darkness (by 1.5–3.2‰). The turnover of the respiratory carbon pool after labelling appears similar in the light and in the dark, and accordingly, a hierarchical clustering analysis shows a close correlation between the 13C abundance in day‐ and night‐evolved CO2. We conclude that the carbon source for respiration is similar in the dark and in the light, but the metabolic pathways associated with CO2 production may change, thereby explaining the different 12C/13C respiratory fractionations in the light and in the dark. 相似文献
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8.
MORAIS PAULO AMORIM ANTÓNIO VIEIRA DA SILVA CLÁUDIA RIBEIRO TERESA COSTA SANTOS JORGE AFONSO COSTA HELOÍSA 《Journal of genetics》2015,94(3):509-512
Journal of Genetics - 相似文献
9.
Axons receive guidance information from extrinsic cues in their environment in order to reach their targets. In the frog Xenopus laevis, retinal ganglion cell (RGC) axons make three key guidance decisions en route through the brain. First, they cross to the contralateral side of the brain at the optic chiasm. Second, they turn caudally in the mid-diencephalon. Finally, they must recognize the optic tectum as their target. The matrix metalloproteinase (MMP) and a disintegrin and metalloproteinase (ADAM) families are zinc (Zn)-dependent proteolytic enzymes. The latter functions in axon guidance, but a similar role has not yet been identified for the MMP family. Our previous work implicated metalloproteinases in the guidance decisions made by Xenopus RGC axons. To test specifically the importance of MMPs, we used two different in vivo exposed brain preparations in which RGC axons were exposed to an MMP-specific pharmacological inhibitor (SB-3CT), either as they reached the optic chiasm or as they extended through the diencephalon en route to the optic tectum. Interestingly, SB-3CT affected only two of the guidance decisions, with misrouting defects at the optic chiasm and tectum. Only at higher concentrations was RGC axon extension also impaired. These data implicate MMPs in the guidance of vertebrate axons, and suggest that different metalloproteinases function to regulate axon behaviour at distinct choice points: an MMP is important in guidance at the optic chiasm and the target, while either a different MMP or an ADAM is required for axons to make the turn in the mid-diencephalon. 相似文献
10.
Lines MA Huang L Schwartzentruber J Douglas SL Lynch DC Beaulieu C Guion-Almeida ML Zechi-Ceide RM Gener B Gillessen-Kaesbach G Nava C Baujat G Horn D Kini U Caliebe A Alanay Y Utine GE Lev D Kohlhase J Grix AW Lohmann DR Hehr U Böhm D;FORGE Canada Consortium Majewski J Bulman DE Wieczorek D Boycott KM 《American journal of human genetics》2012,90(2):369-377
Mandibulofacial dysostosis with microcephaly (MFDM) is a rare sporadic syndrome comprising craniofacial malformations, microcephaly, developmental delay, and a recognizable dysmorphic appearance. Major sequelae, including choanal atresia, sensorineural hearing loss, and cleft palate, each occur in a significant proportion of affected individuals. We present detailed clinical findings in 12 unrelated individuals with MFDM; these 12 individuals compose the largest reported cohort to date. To define the etiology of MFDM, we employed whole-exome sequencing of four unrelated affected individuals and identified heterozygous mutations or deletions of EFTUD2 in all four. Validation studies of eight additional individuals with MFDM demonstrated causative EFTUD2 mutations in all affected individuals tested. A range of EFTUD2-mutation types, including null alleles and frameshifts, is seen in MFDM, consistent with haploinsufficiency; segregation is de novo in all cases assessed to date. U5-116kD, the protein encoded by EFTUD2, is a highly conserved spliceosomal GTPase with a central regulatory role in catalytic splicing and post-splicing-complex disassembly. MFDM is the first multiple-malformation syndrome attributed to a defect of the major spliceosome. Our findings significantly extend the range of reported spliceosomal phenotypes in humans and pave the way for further investigation in related conditions such as Treacher Collins syndrome. 相似文献