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131.
rac-Isradipine is a dihydropyridine type calcium antagonist. Its calcium entry blocking effect is due primarily to the (+)-(S)-enantiomer. This study describes a sensitive enantioselective method for the determination of isradipine in human serum. Following alkaline extraction into hexane, the enantiomers of isradipine are separated quantitatively by high-performance liquid chromatography on a Chiralcel OJ column at 39°C. The collected fractions were evaporated and assayed using capillary gas chromatography on a HP 50+ column with nitrogen selective detection. Using 2.0 ml of serum, 0.7 nmol/1 (0.26 ng/ml) of each enantiomer could be determined with acceptable precision. The method has successfully been used to measure (+)-(S)- and (−)-(R)-isradipine concentrations in samples from volunteers after intravenous and oral administration of isradipine. Chirality 10:808–812, 1998. © 1998 Wiley-Liss, Inc. 相似文献
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134.
Can the agricultural AquaCrop model simulate water use and yield of a poplar short‐rotation coppice? 下载免费PDF全文
Joanna A. Horemans Hanne Van Gaelen Dirk Raes Terenzio Zenone Reinhart Ceulemans 《Global Change Biology Bioenergy》2017,9(6):1151-1164
We calibrated and evaluated the agricultural model AquaCrop for the simulation of water use and yield of a short‐rotation coppice (SRC) plantation with poplar (Populus) in East Flanders (Belgium) during the second and the third rotation (first 2 years only). Differences in crop development and growth during the course of the rotations were taken into account during the model calibration. Overall, the AquaCrop model showed good performance for the daily simulation of soil water content (R2 of 0.57–0.85), of green canopy cover (R2 > 0.87), of evapotranspiration (ET; R2 > 0.76), and of potential yield. The simulated, total yearly water use of the SRC ranged between 55% and 85% of the water use of a reference grass ecosystem calculated under the same environmental conditions. Crop transpiration was between 67% and 93% of total ET, with lower percentages in the first than in the second year of each rotation. The observed (dry mass) yield ranged from 6.61 to 14.76 Mg ha?1 yr?1. A yield gap of around 30% was observed between the second and the third rotation, as well as between simulated and observed yield during the third rotation. This could possibly be explained by the expansion of the understory (weed) layer; the relative cover of understory weeds was 22% in the third year of the third rotation. The agricultural AquaCrop model simulated total water use and potential yield of the operational SRC in a reliable way. As the plantation was extensively managed, potential effects of irrigation and/or fertilization on ET and on yield were not considered in this study. 相似文献
135.
Increased Adipocyte Size,Macrophage Infiltration,and Adverse Local Adipokine Profile in Perirenal Fat in Cushing's Syndrome 下载免费PDF全文
136.
The HtrA Protease of Campylobacter jejuni Is Required for Heat and Oxygen Tolerance and for Optimal Interaction with Human Epithelial Cells 总被引:1,自引:0,他引:1 下载免费PDF全文
Lone Br?ndsted Marianne Thorup Andersen Mary Parker Kirsten J?rgensen Hanne Ingmer 《Applied microbiology》2005,71(6):3205-3212
Campylobacter jejuni is a predominant cause of food-borne bacterial gastroenteritis in the developed world. We have investigated the importance of a homologue of the periplasmic HtrA protease in C. jejuni stress tolerance. A C. jejuni htrA mutant was constructed and compared to the parental strain, and we found that growth of the mutant was severely impaired both at 44°C and in the presence of the tRNA analogue puromycin. Under both conditions, the level of misfolded protein is known to increase, and we propose that the heat-sensitive phenotype of the htrA mutant is caused by an accumulation of misfolded protein in the periplasm. Interestingly, we observed that the level of the molecular chaperones DnaK and ClpB was increased in the htrA mutant, suggesting that accumulation of nonnative proteins in the periplasm induces the expression of cytoplasmic chaperones. While lack of HtrA reduces the oxygen tolerance of C. jejuni, the htrA mutant was not sensitive to compounds that increase the formation of oxygen radicals, such as paraquat, cumene hydroperoxide, and H2O2. Using tissue cultures of human epithelial cells (INT407), we found that the htrA mutant adhered to and invaded human epithelial cells with a decreased frequency compared to the wild-type strain. This defect may be a consequence of the observed altered morphology of the htrA mutant. Thus, our results suggest that in C. jejuni, HtrA is important for growth during stressful conditions and has an impact on virulence. 相似文献
137.
Hanne J?rgensen Espen Fj?rvik Sigrid Hakv?g Per Bruheim Harald Bredholt Geir Klinkenberg Trond E. Ellingsen Sergey B. Zotchev 《Applied and environmental microbiology》2009,75(10):3296-3303
A large number of Streptomyces bacteria with antifungal activity isolated from samples collected in the Trondheim fjord (Norway) were found to produce polyene compounds. Investigation of polyene-containing extracts revealed that most of the isolates produced the same compound, which had an atomic mass and UV spectrum corresponding to those of candicidin D. The morphological diversity of these isolates prompted us to speculate about the involvement of a mobile genetic element in dissemination of the candicidin biosynthesis gene cluster (can). Eight candicidin-producing isolates were analyzed by performing a 16S rRNA gene-based taxonomic analysis, pulsed-field gel electrophoresis, PCR, and Southern blot hybridization with can-specific probes. These analyses revealed that most of the isolates were related, although they were morphologically diverse, and that all of them contained can genes. The majority of the isolates studied contained large plasmids, and two can-specific probes hybridized to a 250-kb plasmid in one isolate. Incubation of the latter isolate at a high temperature resulted in loss of the can genes and candicidin production, while mating of the “cured” strain with a plasmid-containing donor restored candicidin production. The latter result suggested that the 250-kb plasmid contains the complete can gene cluster and could be responsible for conjugative transfer of this cluster to other streptomycetes.Actinomycete bacteria, especially those belonging to the family Streptomycetaceae, are well-known producers of secondary metabolites with diverse biological activities. Representatives of the genus Streptomyces produce a variety of antibiotics with antibacterial, antifungal, and antitumor activities. The majority of antibiotic-producing streptomycetes have been isolated from terrestrial environments, while antibiotic-producing streptomycetes from the marine sources remain largely unexplored. Therefore, studies of streptomycetes from the marine environment are important for unraveling their potential for antibiotic production. In addition, such studies might reveal the means by which antibiotic biosynthesis and resistance genes are spread in nature.It is widely acknowledged that plasmids play an important role in genetic exchange between bacterial species. Conjugative plasmids are quite common in Streptomyces strains (13), and a number of these mobile genetic elements have been characterized in detail. The characterized mobile genetic elements include both circular plasmids, such as pIJ101 from Streptomyces lividans (14) and SCP2 from Streptomyces coelicolor (2, 35), and linear plasmids, such as SLP2 from S. lividans (6) and SCP1 from S. coelicolor (38, 39). The presence of a linear plasmid in Streptomyces was first reported in 1979, and the plasmid was the 17-kb pSLA2 plasmid of Streptomyces rochei (11). SCP1 of S. coelicolor was discovered in the early 1970s (38, 39), but because of its large size (356 kb), isolation of this plasmid with conventional techniques was not possible and therefore it was not recognized as a linear plasmid until pulsed-field gel electrophoresis (PFGE) was invented. Later, SCP1 was shown to harbor a complete set of genes for biosynthesis of the antibiotic methylenomycin (21; K. F. Chater, C. J. Bruton, S. J. O''Rouke, and A. W. Wietzorrek, 5 July 2001, Patent Cooperation Treaty international application WO/2001/048228), while another linear plasmid, found in S. rochei, has been shown to contain genes for biosynthesis of both lankamycin and lankacidin (16, 19, 28, 36). Other examples of plasmids include pPZG103 carrying oxytetracycline biosynthesis genes acquired from the chromosome of Streptomyces rimosus (10) and pKSL from Streptomyces lasaliensis, which might be involved in the production of lasalocid and/or echinomycin (17, 20).Linear plasmids can be transferred between Streptomyces strains by means of conjugation, and SCP1 is an example of a conjugative linear plasmid as it is easily transferred from an SCP1+ strain to an SCP1− strain (39). Interspecific transfer to S. lividans and Streptomyces parvulus has also been reported for this plasmid, and it was demonstrated that the recipient strains had acquired the ability to produce and be resistant to methylenomycin (12, 21). Transfer of intact linear plasmids containing mercury resistance genes from two Streptomyces strains isolated from the marine environment to S. lividans, conferring mercury resistance to the initially mercury-sensitive recipient, has been reported by Ravel et al. (32). It has also been shown that interspecific transfer of linear plasmids is possible in sterile amended soil microcosms, suggesting that mercury resistance might be spread by plasmid transfer in polluted environments (31).We report here isolation and screening of several thousand actinobacterial strains from the Trondheim fjord (Norway), which resulted in identification of producers of both known and potentially new polyene macrolides with antifungal activity. The ability to produce the polyene macrolide candicidin D was found to be widespread among the Trondheim fjord Streptomyces isolates. We also report that the candicidin biosynthesis genes (can) are present on a linear plasmid identified in one of these isolates, suggesting that the can genes might be spread by means of conjugation. 相似文献
138.
Hanne N. Rasmussen Bjarke Veierskov Jens Hansen-Møller Rikke Nørbæk Ulrik Bräuner Nielsen 《Journal of Plant Growth Regulation》2009,28(2):154-166
Conifer trees are routinely manipulated hormonally to increase flowering, branching, or adjust crown shape for production
purposes. This survey of internal cytokinin levels provides a background for such treatments in Abies nordmanniana, a tree of great economic interest. Reference points in the crown and root system were sampled destructively in 4- and 6-year-old
trees and analyzed for a range of cytokinins by LC-MS/MS. No seasonal patterns were detected in the root samples, and a major
portion of cytokinin was in conjugated forms. Dramatic and consistent seasonal changes occurred in the crown, at levels 17–65 times
higher than in the root. Predominant among crown cytokinins was ZR, except in the needles where IPR was also prominent. Within
the crown, cytokinin profiles in different organs differed consistently. The leader bud showed a pronounced mid-June minimum,
and a maximum later in summer. Subapical buds showed the same June minimum but peaked in mid autumn at a much lower level.
Maxima in these buds were preceded by peaks in the subapical stem. Parallel patterns were observed in homologous tissues on
branches.This pattern is consistent with two surges beginning in the uppermost stem tissues leading to subsequent accumulation
or stimulated production within the buds. Strong differential hormonal profiles between adjacent buds with different fates
agree with recent evidence of localized cytokinin production. The data suggest a reduced role of root-derived cytokinins in
crown development. Practical cytokinin treatments for crown-shape regulation require close attention to dosage as well as
precise timing and positioning. 相似文献
139.
Genetic diversity, especially at genes important for immune functioning within the Major Histocompatibility Complex (MHC), has been associated with fitness-related traits, including disease resistance, in many species. Recently, genetic diversity has been associated with mate preferences in humans. Here we asked whether these preferences are adaptive in terms of obtaining healthier mates. We investigated whether genetic diversity (heterozygosity and standardized mean d2) at MHC and nonMHC microsatellite loci, predicted health in 153 individuals. Individuals with greater allelic diversity (d2) at nonMHC loci and at one MHC locus, linked to HLA-DRB1, reported fewer symptoms over a four-month period than individuals with lower d2. In contrast, there were no associations between MHC or nonMHC heterozygosity and health. NonMHC-d2 has previously been found to predict male preferences for female faces. Thus, the current findings suggest that nonMHC diversity may play a role in both natural and sexual selection acting on human populations. 相似文献
140.
Tore Lier Gunnar S. Simonsen Tianping Wang Dabing Lu Hanne H. Haukland Birgitte J. Vennervald Maria V. Johansen 《PLoS neglected tropical diseases》2009,3(2)