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141.
Seemab Mukhtar Naseem Ahmad Md Imran Khan Mohammad Anis Ibrahim M. Aref 《Physiology and Molecular Biology of Plants》2012,18(4):381-386
A comparative performance of two explants types (CN and Nodal) for their
efficiency to induce multiple shoot regeneration in Clitoria
ternatea has been carried out. Thidiazuron (TDZ) in different
concentrations (0.05–2.5 μM) was used as a supplement to the Murashige and Skoog’s
(MS) basal media. Explant type apart, two factors viz. concentration and exposure
duration to TDZ played an important role in affecting multiple shoot regeneration.
Cotyledonary node explants produced the best results at 0.1 μM TDZ, while in nodal
explants the highest rate of shoot formation was achieved on MS medium supplemented
with 1.0 μM TDZ. In both the explants, shoot multiplication increased when the
regenerated shoots were subcultured on hormone free MS medium after 4 weeks of
exposure to TDZ. Among the two, cotyledonary node explants produced considerably
higher number of shoots at a comparatively lower concentration of TDZ than nodal
explants. The regenerated shoots rooted best on MS medium containing 1.0 μM
indole-3-butyric acid (IBA) and were successfully established in pots containing
garden soil with 88 % survival rate. All the regenerated plants showed normal
morphology and growth characteristics. 相似文献
142.
Ritu Ranjan Naseem Ahmed Rajesh Khanna B. N. Mishra 《Biotechnology and Bioprocess Engineering》2009,14(1):38-45
In this study, we designed a strategy for selecting the operating conditions of a mist reactor for the growth of hairy roots.
This was accomplished by developing a mathematical model to optimize the ON/OFF mist duty cycle for the specified growth of
hairy roots. The availability and rate of transport of nutrients to the roots are important parameters in the design and operation
of the reactor. The thin liquid film over the root surface, which continuously builds up during the ON cycle, is a major factor
that limits mass transfer. The same film also acts as a finite reservoir of nutrients in the absence of any replenishment
during the OFF cycle. This reservoir gets depleted as growing roots continue to consume the nutrients. As a result of this
depletion the duration of the OFF cycle must be limited such that the nutrient concentration does not go below the critical
value required for the specified growth rate. The depleted reservoir is then replenished during the next ON cycle to an extent
that depends on feed concentration and duration of the next ON cycle. It was shown that the use of increasing feed concentrations
in the fed-batch mode of operation could maintain a specified growth rate in the reactor. Interestingly, this also resulted
in the efficient operation of the reactor whereby the reactor operated at slightly above the required concentration and close
to the point of minimum mass transfer resistance. 相似文献
143.
E. Brad Thompson Rheem D. Medh Feng Zhou Sylvette Ayala-Torres Naseem Ansari Weiping Zhang Betty H. Johnson 《The Journal of steroid biochemistry and molecular biology》1999,69(1-6):453-461
In clones of the CEM human acute lyumphoblastic leukemic cell line, glucocorticoids, oxysterols and activators of the cAMP pathway acting synergistically with glucocorticoids, each can cause apoptotic cell death. Morphologically and kinetically, these deaths resemble one another. The kinetics are striking: in each case, after addition of the lethal compound(s), an interval of approximately 24 h follows, during which cell growth continues unabated. During this “prodromal” period, removal of the apoptotic agent leaves the cells fully viable. We hypothesize that a sequence of biochemical events occurs during the prodrome which eventually results in the triggering of the full apoptotic response as evidenced by the activation of caspases and DNA fragmentation. At some point, the process is irreversible and proceeds relatively rapidly to cell death. Suppression of c-Myc seems a universal early event evoked by each of these lethal compounds or combinations, and we conclude that the negative regulation of this proto-oncogene is an important aspect of the critical pre-apoptotic events in these cells. 相似文献
144.
145.
146.
The fungal pathogen Candida albicans causes lethal systemic infections in humans. To better define how pathogens resist oxidative attack by the immune system, we examined a family of four Flavodoxin-Like Proteins (FLPs) in C. albicans. In agreement with previous studies showing that FLPs in bacteria and plants act as NAD(P)H quinone oxidoreductases, a C. albicans quadruple mutant lacking all four FLPs (pst1Δ, pst2Δ, pst3Δ, ycp4Δ) was more sensitive to benzoquinone. Interestingly, the quadruple mutant was also more sensitive to a variety of oxidants. Quinone reductase activity confers important antioxidant effects because resistance to oxidation was restored in the quadruple mutant by expressing either Escherichia coli wrbA or mammalian NQO1, two distinct types of quinone reductases. FLPs were detected at the plasma membrane in C. albicans, and the quadruple mutant was more sensitive to linolenic acid, a polyunsaturated fatty acid that can auto-oxidize and promote lipid peroxidation. These observations suggested that FLPs reduce ubiquinone (coenzyme Q), enabling it to serve as an antioxidant in the membrane. In support of this, a C. albicans coq3Δ mutant that fails to synthesize ubiquinone was also highly sensitive to oxidative stress. FLPs are critical for survival in the host, as the quadruple mutant was avirulent in a mouse model of systemic candidiasis under conditions where infection with wild type C. albicans was lethal. The quadruple mutant cells initially grew well in kidneys, the major site of C. albicans growth in mice, but then declined after the influx of neutrophils and by day 4 post-infection 33% of the mice cleared the infection. Thus, FLPs and ubiquinone are important new antioxidant mechanisms that are critical for fungal virulence. The potential of FLPs as novel targets for antifungal therapy is further underscored by their absence in mammalian cells. 相似文献
147.
148.
Phytohormones signal and combine to maintain the physiological equilibrium in the plant. Pathogens enhance host susceptibility by modulating the hormonal balance of the plant cell. Unlike other plant hormones, the detailed role of cytokinin in plant immunity remains to be fully elucidated. Here, extensive data mining, including of pathogenicity factors, host regulatory proteins, enzymes of hormone biosynthesis, and signaling components, established an integrated signaling network of 105 nodes and 163 edges. Dynamic modeling and system analysis identified multiple cytokinin-mediated regulatory interactions in plant disease networks. This includes specific synergism between cytokinin and salicylic acid pathways and previously undiscovered aspects of antagonism between cytokinin and auxin in plant immunity. Predicted interactions and hormonal effects on plant immunity are confirmed in subsequent experiments with Pseudomonas syringae pv tomato DC3000 and Arabidopsis thaliana. Our dynamic simulation is instrumental in predicting system effects of individual components in complex hormone disease networks and synergism or antagonism between pathways. 相似文献
149.
150.
Ahmed N Dubuc C Rousseau J Bénard F van Lier JE 《Bioorganic & medicinal chemistry letters》2007,17(11):3212-3216
Different flavone-, indole-, and furan-17beta-estradiol conjugates, linked via alkyl spacer chains extending from the 17alpha-position of the estradiol moiety, were synthesized by Pd-catalyzed cross-coupling reactions. Structures were assigned based on spectroscopic data. In vitro competitive binding assays for the estrogen receptor (alpha-ER), using [(3)H]estradiol (RBA=100) as a competitor, revealed that a two-carbon alkyl linker combined with a flavone conjugate provided the highest binding affinity (RBA approximately 9), warranting further studies on their potential use as selective estrogen-receptor modulators (SERMs) for hormone-replacement therapies. 相似文献