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71.
As flavonoids have beneficial health effects on humans, they are gaining increasing interest from pharmaceutical and health industries. However, current production methods, such as plant extraction and chemical synthesis, are inadequate to meet the demand. Therefore, microbial production might offer a promising alternative. During recent years, microbial strains able to produce flavonoids to a certain extent have been developed. However production titers are limited to the mg l?1 range, hampering the industrial exploitation of these strains. The latter will not be achieved by simply introducing the heterologous pathway in the production host and optimizing the fermentation process, but will depend on the interaction of different aspects of metabolic engineering and process engineering to overcome the current limitations. Next to engineering the production strain to optimize the availability of precursors, the pathway itself also requires intensive engineering. Currently utilized strategies result in a wide variety of different production strains, requiring high-throughput screening methods to identify optimal performing strains. As more and more organisms are being characterized, each with their own specific properties which might be beneficial for the heterologous production of flavonoids, the choice of the production host is another important aspect. Finally, the use of co-cultures might offer an alternative in which different parts of the process are performed by different organisms. This review aims to provide an overview of the research that has been done on these separate aspects. The work presented here could be used as a framework for further research. 相似文献
72.
Methanol Extracts of 28 Hieracium Species from the Balkan Peninsula – Comparative LC–MS Analysis,Chemosystematic Evaluation of their Flavonoid and Phenolic Acid Profiles and Antioxidant Potentials
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Violeta Milutinović Marjan Niketić Ljuboš Ušjak Dejan Nikolić Aleksej Krunić Christian Zidorn Silvana Petrović 《Phytochemical analysis : PCA》2018,29(1):30-47
Introduction
Hieracium s. str. represents one of the largest and most complex genera of flowering plants. As molecular genetics seems unlikely to disentangle intricate relationships within this reticulate species complex, analysis of flavonoids and phenolic acids, known as good chemosystematic markers, promise to be more reliable. Data about pharmacological activity of Hieracium species are scarce.Objective
Evaluation of the chemosystematic significance of flavonoids and phenolic acids of methanol extracts of aerial flowering parts of 28 Hieracium species from the Balkans. Additionally, investigation of antioxidant potentials of the extracts.Methods
Comparative qualitative and quantitative analysis of flavonoids and phenolic acids was performed by LC–MS. Multivariate statistical data analysis included non‐metric multidimensional scaling (nMDS), unweighted pair‐group arithmetic averages (UPGMA) and principal component analysis (PCA). Antioxidant activity was evaluated using three colorimetric tests.Results
Dominant phenolics in almost all species were luteolin type flavonoids, followed by phenolic acids. Although the investigated Hieracium species share many compounds, the current classification of the genus was supported by nMDS and UPGMA analyses with a good resolution to the group level. Hieracium naegelianum was clearly separated from the other investigated species. Spatial and ecological distances of the samples were likely to influence unexpected differentiation of some groups within H. sect. Pannosa. The vast majority of dominant compounds significantly contributed to differences between taxa. The antioxidant potential of the extracts was satisfactory and in accordance with their phenolics composition.Conclusions
Comparative LC–MS analysis demonstrated that flavonoids and phenolic acids are good indicators of chemosystematic relationships within Hieracium, particularly between non‐hybrid species and groups from the same location. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献73.
Marjan Kostowiecki 《Cell and tissue research》1963,59(6):790-803
Summary This study reports the normal thymus of a 3 year old girl in which four germinal centers have been found in different lobules. They are located in the medulla, three of them in the cortico-medullary junction. Reticular cells, medium-sized and occasionally large lymphocytes, reticular macrophages and a large number of immature and mature thymocytes occupy the germinal centers. The medium-sized lymphocytes divide and give rise to smaller cells which appear to move to the peripheral zone to become thymocytes. 相似文献
74.
75.
Tetranychus urticae Koch (Acari: Tetranychidae) and Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) are major pests in greenhouse crops. Recently, Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) was shown to be an effective biological control agent of both pests. Therefore, the prey preference of A. swirskii was determined using immature stages of T. urticae and B. tabaci in three various treatments based on Manly's β preference index (β). These treatments consisted of immature stages of two prey species (egg, first and second instar nymphs) with densities 12:12, 6:6 and 3:3, respectively, and with 13 replicates. After 24?h starvation, same-aged females of A. swirskii were added to the leaf discs. All experiments were done on bean leaf discs in Petri dishes (8?cm in diameter) in laboratory conditions with 25?±?2°C, 70?±?5% relative humidity and the photoperiod of 16L:8D hours. Comparing the preference indices using t-tests indicates a significant preference of the predator on eggs (t?=?10.80, df?=?24, P?0.0001) and second instar nymphs (t?=?8.17, df?=?24, P?0.0001) of T. urticae than B. tabaci. Our findings suggest that developmental stages of prey have effect on the prey selection by A. swirskii. 相似文献
76.
Hamed Alborzinia Marjan Shaikhkarami Peter Hortschansky Stefan Wölfl 《Traffic (Copenhagen, Denmark)》2016,17(9):1042-1053
Morphogen gradients and concentration are critical features during early embryonic development and cellular differentiation. Previously we reported the preparation of biologically active, fluorescently labeled BMP2 and quantitatively analyzed their binding to the cell surface and followed BMP2 endocytosis over time on the level of single endosomes. Here we show that this internalized BMP2 can be transferred to neighboring cells and, moreover, also activates downstream BMP signaling in adjacent cells, indicated by Smad1/5/8 phosphorylation and activation of the downstream target gene id1. Using a 3D matrix to modulate cell–cell contacts in culture we could show that direct cell–cell contact significantly increased BMP2 transfer. Using inhibitors of vesicular transport, transfer was strongly inhibited. Interestingly, cotreatment with the physiological BMP inhibitor Noggin increased BMP2 uptake and transfer, albeit activation of Smad signaling in neighboring cells was completely suppressed. Our findings present a novel and interesting mechanism by which morphogens such as BMP2 can be transferred between cells and how this is modulated by BMP antagonists such as Noggin, and how this influences activation of Smad signaling by BMP2 in neighboring cells. 相似文献
77.
Robby Stoks Marjan De Block Hans Van Gossum Famke Valck Kris Lauwers Ron Verhagen Erik Matthysen Luc De Bruyn 《Oecologia》1999,120(1):87-91
We studied the costs of lamellae autotomy with respect to growth and survival of Lestes sponsa damselfly larvae in field experiments. We manipulated predation risk by Aeshna cyanea dragonfly larvae and lamellae status of L. sponsa larvae in field enclosures and compared differences in numbers, size and mass of survivors among treatments. In the absence
of a free-ranging A. cyanea larva, about 29% of the L. sponsa larvae died. This was probably due to cannibalism. The presence of a free-ranging A. cyanea reduced larval survival by 68% compared to treatments in which it was absent or not permitted to forage on L. sponsa damselflies. Across all predator treatments, lamellae autotomy reduced survival by about 20%. The mean head width and mass
of survivors was lower in the enclosures with a free-ranging A. cyanea compared to the other two predator treatments. This suggested that larvae grew less in the presence of a free-ranging predator,
indicating that increased antipredator behaviours were more important in shaping growth responses than reduced population
density. Mass, but not head width, of survivors was also reduced after autotomy. The fitness consequences of these effects
for the adults may be pronounced. In general, these field data strongly suggest that lamellae autotomy affects population
regulation of damselflies.
Received: 1 February 1999 / Accepted: 22 March 1999 相似文献
78.
Marjan J. Smeulders Jacquie Keer Richard A. Speight Huw D. Williams 《Journal of bacteriology》1999,181(1):270-283
Mycobacterium tuberculosis can persist for many years within host lung tissue without causing clinical disease. Little is known about the state in which the bacilli survive, although it is frequently referred to as dormancy. Some evidence suggests that cells survive in nutrient-deprived stationary phase. Therefore, we are studying stationary-phase survival of Mycobacterium smegmatis as a model for mycobacterial persistence. M. smegmatis cultures could survive 650 days of either carbon, nitrogen, or phosphorus starvation. In carbon-limited medium, cells entered stationary phase before the carbon source (glycerol) had been completely depleted and glycerol uptake from the medium continued during the early stages of stationary phase. These results suggest that the cells are able to sense when the glycerol is approaching limiting concentrations and initiate a shutdown into stationary phase, which involves the uptake of the remaining glycerol from the medium. During early stationary phase, cells underwent reductive cell division and became more resistant to osmotic and acid stress and pool mRNA stabilized. Stationary-phase cells were also more resistant to oxidative stress, but this resistance was induced during late exponential phase in a cell-density-dependent manner. Upon recovery in fresh medium, stationary-phase cultures showed an immediate increase in protein synthesis irrespective of culture age. Colony morphology variants accumulated in stationary-phase cultures. A flat colony variant was seen in 75% of all long-term-stationary-phase cultures and frequently took over the whole population. Cryo scanning electron microscopy showed that the colony organization was different in flat colony strains, flat colonies appearing less well organized than wild-type colonies. Competition experiments with an exponential-phase-adapted wild-type strain showed that the flat strain had a competitive advantage in stationary phase, as well a providing evidence that growth and cell division occur in stationary-phase cultures of M. smegmatis. These results argue against stationary-phase M. smegmatis cultures entering a quiescent state akin to dormancy but support the idea that they are a dynamic population of cells. 相似文献
79.
Cryptococcus neoformans and Cryptococcus gattii are closely related pathogenic basidiomycetous yeasts in which six haploid genotypic groups have been distinguished. The two haploid genotypic groups of C. neoformans have been described as variety grubii and variety neoformans. The four C. gattii genotypic groups have, however, not been described as separate taxa. One hundred and seventeen isolates representing all six haploid genotypic groups were selected for multi-locus sequence typing using six loci to investigate if the isolates consistently formed monophyletic lineages. Two monophyletic lineages, corresponding to varieties grubii and neoformans, were consistently present within C. neoformans, supporting the current classification. In addition, four monophyletic lineages corresponding to the previously described genotypic groups were consistently found within C. gattii, indicating that these lineages should be considered different taxa as well. 相似文献
80.
Wildenberg ME van Helden-Meeuwsen CG Drexhage HA Versnel MA 《Arthritis research & therapy》2008,10(3):R69-7