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1.
LARSSON MARIE; LARSSON CARL-MAGNUS; GUERRERO MIGUEL G. 《Journal of experimental botany》1985,36(9):1373-1386
Larsson, M., Larsson, C.-M. and Guerrero, M. G. 1985. Photosyntheticnitrogen metabolism in high and low CO2-adapted Scenedesmus.I. Inorganic carbon-dependent O2 evolution, nitrate utilizationand nitrogen recycling.J. exp Bot. 36: 13731386 Scenedesmus obtusiusculus Chod. was grown on an inorganic mediumflushed with either air or air supplemented with 3% CO2. Inair-grown cells, O2 evolution dependent on low, but not high,HCO3 concentrations was strongly inhibited by the carbonicanhydrase inhibitor acetazolamide. Cells grown with 3% CO2 exhibitedlow rates of O2 evolution at low external inorganic C; however,after 30 min in air O2 evolution rates at low inorganic C approachedthose of air-grown cells. These results are compatible withthe view that Scenedesmus develops a CO2 concentratingmechanism in air, with carbonic anhydrase as an importantconstituent When 3% CO2-grown cells were subjected to air-level of CO2,just a transient decline in NO3 utilization was observed,but in the presence of acetazolamide the rate of the processdecreased drastically in response to the decrease in the CO2level. In CO2-free air NO3 was taken up at high ratesbut in a deregulated manner, leading to release of NH4+. A portionof the NO3 taken up in the absence of CO2 was apparentlyassimilated Cellular nitrate reductase (NR) activity initially decreasedbut subsequently recovered after a transition from 3% CO2 toair. In the presence of acetazolamide, a persistent decreasein NR activity was observed. Cellular glutamine synthetase (GS)activity increased after transition from 3% CO2 to air, theactivity increase being unaffected by acetazolamide. NH4+ releaseto the medium in the presence of L-methionine-D, L-sulphoximine(MSO) transiently increased in 3% CO2-grown cells in responseto a transfer to air. MSO-induced NH4+ release was in fact higherin air-grown cells than in 3% CO2-grown cells. Glycollate wasinitially released after transition from 3% CO2 to air, butthere was no difference in glycollate release between MSO-treatedand untreated cells. In air-adapted Scenedesmus, N recyclingseems to be of minor importance in comparison to primary N assimilation Key words: CO2-fixation, N recycling, nitrate uptake, Scenedesmus 相似文献
2.
LARSSON CARL-MAGNUS; LARSSON MARIE; GUERRERO MIGUEL G. 《Journal of experimental botany》1985,36(9):1387-1395
Larsson, C.-M., Larsson, M. and Guerrero, M. G. 1985. Photosyntheticnitrogen metabolism in high and low CO2-adapted Scenedesmus.II. Effect of ammonium and methionine sulphoximine on nitrateutilization.J. exp. Bot. 36: 13871395 In 3% CO2-grown Scenedesmus obtusiusculus Chod. utilizing NO3J as the N source, NH4+ addition caused a prompt inhibitionof NO3 utilization. Nitrate reductase (NR) activity declinedrapidly in response to the presence of NO4+, but the cessationof NO3 utilization was too rapid to be accounted forby the loss in NR activity. The first site of NO4+ inhibitionin these cells seems to be the entrance of NO3 into thecells. Upon exhaustion of NO4+ from the medium, NO3 utilizationwas rapidly restored and NR activity increased. Air-grown cellswere much less sensitive to the effect of NO4+, more than 30min being required for added NO4+ to cause complete inhibitionof NO3 utilization. In these cells, NO3 uptakeand NR activity decreased in parallel in response to NO4+ addition.In 3% CO2-grown cells simultaneously subjected to NO4+ and air-levelof CO2, NO4+ initially inhibited NO3 utilization completely,but a slight recovery took place after approximately 20 min The glutamine synthetase (GS) inhibitor L-methionine D, L-sulphoximine(MSO) behaved as a potent inhibitor of NO3 uptake in3% CO2-grown cells, but had considerably less effect in air-growncells, although the time-course of the MSO-induced inhibitionof GS was the same in both cases Key words: Ammonium, nitrate utilization, Scenedesmus 相似文献
3.
Antigens of the Ii System on Lymphocytes 总被引:8,自引:0,他引:8
K. H. SHUMAK ROSE A. RACHKEWICH MARIE C. CROOKSTON J. H. CROOKSTON 《Nature: New biology》1971,231(22):148-149
USUALLY Ii specificity is assigned to cold agglutinins on the basis of their reactions with the red cells of human adults (adult red cells) and newborn infants (cord red cells). Those which react more strongly with adult red cells are said to detect I antigen and are designated anti-I; those which react more strongly with cord red cells are said to detect i antigen and are designated anti-i1,2. We have now found that I and i antigens can be easily detected on lymphocytes. 相似文献
4.
5.
LAGUEUX MARIE; SALL CATHERINE; HOFFMANN JULES A. 《Integrative and comparative biology》1981,21(3):715-726
SYNOPSIS. Ovaries of Locusta migratoria synthesize large amountsof ecdysteroids at the end of oöcyte maturation. The predominantecdysteroids in mature ovaries are conjugated 2-deoxyecdysone(100 µM) and conjugated ecdysone (50 µM) which outnumberthe corresponding free compounds by 50100 fold. Thesevarious ecdysteroids persist during ovulation and are recoveredfrom newly-laid eggs. The conjugated maternal ecdysteroids aregradually metabolized as embryonic development proceeds; theyhave disappeared as such on day 6 after oviposition, that isafter blastokinesis and shortly after dorsal closure. Concomitantlyto this metabolism of the maternal conjugated ecdysteroids,other ecdysteroid conjugates appear in the eggs which have differentchromatographic behaviors and some of which are conjugates ofecdysone metabolites formed by the embryo. The data availableso far are compatible with the hypothesis that the maternalconjugates are hydrolysed to free 2-deoxyecdysone and ecdysoneby the embryo during early stages of development and subsequentlyconjugated to inactivation compounds. During the later stagesof embryonic development however, a de novo synthesis of ecdysoneis probable, the maternal conjugates having been metabolizedduring the earlier stages. 相似文献
6.
Isoperoxidases in Epidermal Layers of Tobacco and Changes during Organ Formation in vitro 总被引:1,自引:0,他引:1
The content and pattern of soluble isoperoxidases were determined in epidermal explants taken from different internodes of tobacco plants in the vegetative and floral states. There were qualitative and quantitative differences in the isoperoxidases, with a decrease in content and fewer bands being observed acropetally, i.e., in going from the base of the stem towards the apex. Epidermal explants from floral branches were grown in in vitro culture, with various media moditications, to form de novo floral or vegetative buds, roots or callus. Changes in soluble isoperoxidases were followed electrophoretically in relation to these varying morphogenetic pathways. In each of them, the number of bands increased on both the anodic and cathodic sides with time in culture. Compared to each other these four morphogenetic programmes were different in their peroxidase zymograms, mainly through varying kinetics in the development of activity of the isoenzymes. The changes observed during root and vegetative bud formation agree with previously published data, and the changes during floral bud formation agree with those observed in vivo. 相似文献
7.
NICOLAS FEAU MARIE‐JOSE BERGERON DAVID L. JOLY FABIEN ROUSSEL RICHARD C. HAMELIN 《Molecular ecology resources》2007,7(6):1222-1228
We report the discovery, characterization and validation of 118 single nucleotide polymorphisms (SNPs) for poplar leaf rust Melampsora medusae f. sp. deltoidae identified using a gene‐targeted approach in an expressed sequence tag (EST) library. We developed a genotyping assay using the iPLEX? primer extension method for two multiplex assays of 28 and 22 SNPs. 相似文献
8.
MARIA ALP IRENE KELLER ANJA MARIE WESTRAM CHRISTOPHER T. ROBINSON 《Freshwater Biology》2012,57(5):969-981
1. Determined by landscape structure as well as dispersal‐related traits of species, connectivity influences various key aspects of population biology, ranging from population persistence to genetic structure and diversity. Here, we investigated differences in small‐scale connectivity in terms of gene flow between populations of two ecologically important invertebrates with contrasting dispersal‐related traits: an amphipod (Gammarus fossarum) with a purely aquatic life cycle and a mayfly (Baetis rhodani) with a terrestrial adult stage. 2. We used highly polymorphic markers to estimate genetic differentiation between populations of both species within a Swiss pre‐alpine catchment and compared these results to the broader‐scale genetic structure within the Rhine drainage. Landscape genetic approaches were used to test for correlations of genetic and geographical structures and in‐stream barrier effects. 3. We found overall very weak genetic structure in populations of B. rhodani. In contrast, G. fossarum showed strong genetic differentiation, even at spatial scales of a few kilometres, and a clear pattern of isolation by distance. Genetic diversity decreased from downstream towards upstream populations of G. fossarum, suggesting asymmetric gene flow. Correlation of genetic structure with landscape topography was more pronounced in the amphipod. Our study also indicates that G. fossarum might be capable of dispersing overland in headwater regions and of crossing small in‐stream barriers. 4. We speculate that differences in dispersal capacity but also habitat specialisation and potentially the extent of local adaptation could be responsible for the differences in genetic differentiation found between the two species. These results highlight the importance of taking into account dispersal‐related traits when planning management and conservation strategies. 相似文献
9.
MAGALIE CASTELIN JOSIE LAMBOURDIERE MARIE‐CATHERINE BOISSELIER PIERRE LOZOUET ARNAUD COULOUX CORINNE CRUAUD SARAH SAMADI 《Biological journal of the Linnean Society. Linnean Society of London》2010,100(2):420-438
The seamounts chain offers a set of fragmented habitats in which species with poor dispersive ability may undergo divergence in allopatry. Such a scenario may explain the endemism often described on seamounts. In gastropods, it is possible to infer the mode of development of a species from the morphology of its larval shell. Accordingly, we examine the population genetics of several caenogastropods from the Norfolk and Lord Howe seamounts (south‐west Pacific) with contrasting modes of larval development. A prerequisite to our study was to clarify the taxonomic framework. The species delimitation was ruled using an integrative approach, based on both morphological and molecular evidence. Molecular data indicate an unexpected taxonomic diversity within the existing species names. Both the clarification of the taxonomic framework and the importance of the sampling effort allow us to confidently detect cryptic diversity and micro‐endemism. These results are discussed in relation to the dispersive capacities of the organisms. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 420–438. 相似文献
10.
MATILDE ALFONSO ERIC NEYRAUD OLIVIER BLANC MARIE AGNES PEYRON ERIC DRANSFIELD 《Journal of sensory studies》2002,17(2):193-206
The jaw movements and muscular activity of masticatory muscles of five assessors, having bitterness thresholds about 8 μM quinine in water, were monitored throughout chewing of similar strength gelatin gels containing 0, 40, 70 or 100 μM quinine. Gel bitterness ratings were not related to sensory texture which was 78kN/m2 by shear test. On average, 100 μM quinine gels were as bitter as 7 to 30 μM quinine in water, depending on the assessor. Chewing patterns were not affected by concentration of quinine in the gels. During mastication of acceptable gels, there appears to be no feedback from taste to the motor control of mastication. In gels of the same consistency and the same concentration of quinine, assessors who chewed more rated higher for bitterness. The implications for mimicking mastication by machine and the training of assessors for solid foods are discussed. 相似文献