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151.
The benzenoid ester, methylbenzoate is one of the most abundant scent compounds detected in the majority of snapdragon (Antirrhinum majus) varieties. It is produced in upper and lower lobes of petals by enzymatic methylation of benzoic acid in the reaction catalyzed by S-adenosyl-L-methionine:benzoic acid carboxyl methyltransferase (BAMT). To identify the location of methylbenzoate biosynthesis, we conducted an extensive immunolocalization study by light and electron microscopy at cellular and subcellular levels using antibodies against BAMT protein. BAMT was immunolocalized predominantly in the conical cells of the inner epidermal layer and, to a much lesser extent, in the cells of the outer epidermis of snapdragon flower petal lobes. It was also located in the inner epidermis of the corolla tube with little BAMT protein detected in the outer epidermis and in the yellow hairs within the tube on the bee's way to the nectar. These results strongly suggest that scent biosynthetic genes are expressed almost exclusively in the epidermal cells of floral organs. Immunogold labeling studies reveal that BAMT is a cytosolic enzyme, suggesting cytosolic location of methylbenzoate biosynthesis. The concentration of scent production on flower surfaces that face the pollinators during landing may increase pollination efficiency and also help to minimize the biosynthetic cost of advertising for pollinators. 相似文献
152.
Godhe Anna; Noren Fredrik; Kuylenstierna Mats; Ekberg Christian; Karlson Bengt 《Journal of plankton research》2001,23(9):923-938
In order to study the relationship between planktonic dinoflagellates,cyst production and environmental factors, a sediment trap studywas conducted in the Gullmar Fjord, Swedish west coast, during21 days in MayJune 1998. Five locations for sedimenttraps were randomly selected every third day. The traps weremoored at the five locations and moved to new locations after3 days. At every location, a CTD depth profile was obtainedand water samples were collected for plankton, chlorophyll aand nutrient analysis. Meteorological and hydrographic datafor the period were obtained from continuous monitoring. Threedinoflagellate species, which have not previously been recordedfrom the Kattegat or the Skagerrak (Scrippsiella crystallina,Scrippsiella lachrymosa and Scrippsiella trifida), were encounteredduring the analysis of cysts from the sediment traps. The abundanceof the different species in the motile form encountered in thewater column and cyst form encountered in the sediment trapsvaried greatly. The discrepancy between the number and speciesencountered in traps and water samples is discussed. No density-dependentrelationship between the abundance of planktonic cyst-formingdinoflagellates and the number of cysts recovered could be observed.A multiple regression showed that the variation in cyst yieldfrom the traps for the most abundant species was correlatedwith water surface temperature, ambient light radiation andthe depth of the halocline. The nutrient concentrations (NH4+,NO2, NO3 and PO43), which are known toplay a crucial role in induction of sexuality and cyst formationunder laboratory conditions, correlated poorly with the numberof dinoflagellate cysts encountered in the traps. 相似文献
153.
154.
Rheumatoid arthritis is a systemic autoimmune disease characterized by chronic, destructive, debilitating arthritis. Its etiology
is unknown; it is presumed that environmental factors trigger development in the genetically predisposed. Epstein–Barr virus,
a nearly ubiquitous virus in the human population, has generated great interest as a potential trigger. This virus stimulates
polyclonal lymphocyte expansion and persists within B lymphocytes for the host's life, inhibited from reactivating by the
immune response. In latent and replicating forms, it has immunomodulating actions that could play a role in the development
of this autoimmune disease. The evidence linking Epstein–Barr virus and rheumatoid arthritis is reviewed. 相似文献
155.
Isolation and taxonomic affiliation of N-heterocyclic aromatic hydrocarbon-transforming bacteria 总被引:4,自引:0,他引:4
Willumsen PA Johansen JE Karlson U Hansen BM 《Applied microbiology and biotechnology》2005,67(3):420-428
The azaarenes (nitrogen-containing heterocyclic aromatic hydrocarbons) are products of incomplete combustion processes and thus are widely distributed with tar and oil products in the environment. Despite their adverse organoleptic, toxic, and carcinogenic characteristics, the biodegradability and fate of multi-ring azaarenes have received little attention. This work demonstrates the presence of genetically diverse azaarene-degrading bacteria in coal tar-contaminated soils. Thirty-eight bacterial strains able to transform the three-ring azaarenes, 5,6- and 7,8-benzoquinoline, phenanthridine, phenazine, or acridine, were isolated. Only seven of these strains grew in liquid medium on the specific azaarene compounds on which they were isolated using plates; and the rest transformed the azaarenes without growth. Taxonomic characterization by 16S ribosomal DNA sequencing revealed that our enrichment technique provided a diversity of 18 different azaarene-transforming bacterial species. Only a few strains were able to mineralize the homocyclic analogue, phenanthrene. Several of the isolates, e.g., Dyadobacter fermentans, Methylopila capsulata, and Agrobacterium tumefaciens, were related to genera relatively unknown with respect to the biodegradation of xenobiotic compounds. These strains can provide further information on the fate of azaarenes in the environment. 相似文献
156.
A predominant 24-kD dehydrin-like protein was previously found to fluctuate seasonally within red-osier dogwood (Cornus sericea L.) stems. The current study attempted to determine what environmental cues triggered the accumulation of the 24-kD protein and to assess its potential role in winter survival. Controlled photoperiod and field studies confirmed that photoperiod regulates a reduction of stem water content (SWC), freeze-tolerance enhancement and accumulation of the 24-kD protein. Diverse climatic ecotypes, which are known to respond to different critical photoperiods, displayed differential reduction of SWC and accumulation of the 24-kD protein. A time-course study confirmed that prolonged exposure to short days is essential for SWC reduction, 24-kD protein accumulation, and freeze-tolerance enhancement. Water deficit induced 24-kD protein accumulation and enhanced freeze-tolerance under long-day conditions. In all instances, freeze-tolerance enhancement and 24-kD protein accumulation was preceded by a reduction of SWC. These results are consistent with the hypothesis that C. sericea responds to decreasing photoperiod, which triggers a reduction in SWC. Reduced SWC in turn may trigger the accumulation of the 24-kD protein and a parallel increase in freeze-tolerance. 相似文献
157.
Heparin antagonists are potent inhibitors of mast cell tryptase 总被引:7,自引:0,他引:7
Tryptase may be a key mediator in mast cell-mediated inflammatory reactions. When mast cells are activated, they release large amounts of these tetrameric trypsin-like serine proteases. Tryptase is present in a macromolecular complex with heparin proteoglycan where the interaction with heparin is known to be essential for maintaining enzymatic activity. Recent investigations have shown that tryptase has potent proinflammatory activity, and inhibitors of tryptase have been shown to modulate allergic reactions in vivo. Many of the tryptase inhibitors investigated previously are directed against the active site. In the present study we have investigated an alternative approach for tryptase regulation. We show that the heparin antagonists Polybrene and protamine are potent inhibitors of both human lung tryptase and of recombinant mouse tryptase (mouse mast cell protease 6). Protamine inhibited tryptase in a competitive manner whereas Polybrene showed noncompetitive inhibition kinetics. Treatment of tetrameric, active tryptase with Polybrene caused dissociation into monomers, accompanied by complete loss of enzymatic activity. The present report thus suggests that heparin antagonists potentially may be used in treatment of mast cell-mediated diseases such as asthma. 相似文献
158.
Being an extreme environment, the atmosphere may act as a selective barrier for bacterial dispersal, where only most robust organisms survive. By remaining viable during atmospheric transport, these cells affect the patterns of microbial distribution and modify the chemical composition of the atmosphere. The species evenness and richness, and the community composition of a storm cloud were studied applying cultivation-dependent and cultivation-independent techniques to a collection of hailstones. In toto 231 OTUs were identified, and the total species richness was estimated to be about 1800 OTUs. The diversity indices - species richness and evenness - suggest a functionally stable community, capable of resisting environmental stress. A broad substrate spectrum of the isolates with epiphytic origin (genus Methylobacterium) implied opportunistic ecologic strategy with high growth rates and fast growth responses. These may grow in situ despite their short residence times in cloud droplets. In addition, epiphytic isolates utilized many atmospheric organic compounds, including a variety of carboxylic acids. In summary, the highly diverse bacterial community, within which the opportunistic bacteria may be particularly important in terms of atmospheric chemistry, is likely to remain functional under stressful conditions. Overall our study adds important details to the growing evidence of active microbial life in clouds. 相似文献
159.
160.
We examine changing ecological theory regarding the role of disturbance in natural communities and relate past and emerging paradigms to coral reefs. We explore the elements of this theory, including patterns (diversity, distribution, and abundance) and processes (competition, succession, and disturbance), using currently evolving notions concerning matters of scale (temporal and spatial), local versus regional species richness, and the equilibrium versus nonequilibrium controversy. We conclude that any attempt to categorize coral reef communities with respect to disturbance regimes will depend on the question being asked and the desired level of resolution: local assemblage versus regional species pool, successional versus geological time, and on the taxonomic and tropic affinities of species included in the study. As with many communities in nature, coral reefs will prove to be mosaics of species assemblages with equilibrial and nonequilibrial dynamics. 相似文献