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91.
The biochemical mechanisms underlying thidiazuron (TDZ)-induced regeneration in plant cells have not been clearly elucidated.
Exposure of leaf explants of Echinacea purpurea to a medium containing TDZ results in undifferentiated cell proliferation and differentiated growth as mixed shoot organogenesis
and somatic embryogenesis. The current studies were undertaken to determine the potential roles of auxin, indoleamines, and
ion signaling in the dedifferentiation and redifferentiation of plant cells. E. purpurea leaf explants were found to contain auxin and the related indoleamine neurotransmitters, melatonin, and serotonin. The levels
of these endogenous indoleamines were increased by exposure to TDZ associated with the induction of regeneration. The auxin-transport
inhibitor 2,3,5-triiodobenzoic acid and auxin action inhibitor, p-chlorophenoxyisobutyric acid decreased the TDZ-induced regeneration but increased concentrations of endogenous serotonin
and melatonin. As well, inhibitors of calcium and sodium transport significantly reduced TDZ-induced morphogenesis while increasing
endogenous indoleamine content. These data indicate that TDZ-induced regeneration is the manifestation of a metabolic cascade
that includes an initial signaling event, accumulation, and transport of endogenous plant signals such as auxin and melatonin,
a system of secondary messengers, and a concurrent stress response. 相似文献
92.
93.
Xi Jiang Jingyin Yue Huimei Lu Neil Campbell Qifeng Yang Shijie Lan Bruce G. Haffty Changji Yuan Zhiyuan Shen 《International journal of biological sciences》2013,9(1):67-77
Filamin-A cross-links actin filaments into dynamic orthogonal networks, and interacts with an array of proteins of diverse cellular functions. Because several filamin-A interaction partners are implicated in signaling of cell mobility regulation, we tested the hypothesis that filamin-A plays a role in cancer metastasis. Using four pairs of filamin-A proficient and deficient isogenic cell lines, we found that filamin-A deficiency in cancer cells significantly reduces their migration and invasion. Using a xenograft tumor model with subcutaneous and intracardiac injections of tumor cells, we found that the filamin-A deficiency causes significant reduction of lung, splenic and systemic metastasis in nude mice. We evaluated the expression of filamin-A in breast cancer tissues by immunohistochemical staining, and found that low levels of filamin-A expression in cancer cells of the tumor tissues are associated with a better distant metastasis-free survival than those with normal levels of filamin-A. These data not only validate filamin-A as a prognostic marker for cancer metastasis, but also suggest that inhibition of filamin-A in cancer cells may reduce metastasis and that filamin-A can be used as a therapeutic target for filamin-A positive cancer. 相似文献
94.
Nadiah Pardede Kristensen Jacob Johansson Niclas Jonzén Henrik G. Smith 《Evolutionary ecology》2018,32(5):509-528
It is generally expected that, in environments with pronounced seasonal resource peaks, birds’ reproductive success will be maximised when nestlings’ peak food demand coincides with the timing of high food availability. However in certain birds that stay resident over winter, earlier breeding leads juveniles to join the winter flock earlier, which by the prior residence effect increases their success in breeding territory competition. This trade-off between reproduction and competition may explain why, in certain species, breeding phenology is earlier and asynchronous with the resource. This study extends a previous model of the evolution of breeding phenology in a single habitat type to a landscape with two habitat types: ‘early’ and ‘late’ resource phenology. The offspring’s natal habitat type has a carryover effect upon their competitive ability regardless of which habitat type they settle in to potentially breed. We find that, when the difference in resource phenology between habitats is small (weak carryover effect), breeding phenology in the late habitat evolves to occur earlier and more asynchronously than in the early habitat, to compensate for the competitive disadvantage to juveniles raised there. However if the difference is large (strong carryover effect), then the reproductive cost of earlier breeding outweighs the benefit of the compensation, so instead breeding phenology in the late habitat evolves to become more synchronous with the resource. Recruitment is generally asymmetric, from early to late habitat type. However if the early habitat is less frequent in the landscape or produces fewer offspring, then the asymmetry is reduced, and if there is some natal habitat-type fidelity, then recruitment can have an insular pattern, i.e. most recruits to each habitat type come from that same habitat type. We detail the different scenarios in which the different recruitment patterns are predicted, and we propose that they have implications for local adaptation. 相似文献
95.
Riboprinting was used to determine the relationships among strains belonging to 15 species of the genusKluyveromyces. The small subunit ribosomal RNA gene (SSU rDNA) was amplified using the Polymerase Chain Reaction (PCR) and subjected to a battery of nine restriction enzymes. Similarity coefficients between strains were calculated based on shared and unique restriction fragments. Cluster analysis revealed three major groups that generally correlated with previously reported relationships based on other molecular data. Variations in SSU rDNA restriction fragments may be used for differentiation of theKluyveromyces strains included in this study.The U.S. Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged. 相似文献
96.
Kuvalekar Aniket Pawar Pankaj Khare Ankita Gandhe Kanchanganga Harsulkar Abhay 《Plant Cell, Tissue and Organ Culture》2008,94(1):101-104
Ravenelia esculenta Naras. and Thirum. is a rust, pathogenic to Acacia eburnea Willd. The infection leads to hypertrophy changing the morphology with bizarre shapes of plant organs. Healthy and infected
tissues were subjected to extraction of IAA and indole derivatives and were estimated by spectrophotometric methods. The hypertrophy
produced was presumed to be due to increase in the indole-3-acetic acid (IAA) content in the infected tissue, however, the
amount of IAA in infected tissues decreased with the progression of disease. Concomitantly, the infected tissue showed the
presence of a novel, slow migrating, indole derivative on TLC. Cultured shoot tips of Withania somnifera were dosed with the methanolic extract of the infected hypertrophied tissue (MEHT) (0.25, 0.5, 0.75, 1.00 and 1.25 mg/l).
The stimulation in shoot growth along with profuse rooting was observed in a dose dependent manner with maximum at 1.00 and
1.25 mg/l concentration. 相似文献
97.
Precipitation is a key factor in the water cycle. At the same time, precipitation is the focus of study in meteorology and
climatology, ecological environmental assessment, non-point source pollution and so on. Understanding the temporal-spatial
variation and the corresponding factors of precipitation has become the object of hydrology and environmentology. Based on
the annual precipitation data, we analyzed the spatial distribution of precipitation in Sichuan Province in China as well
as the temporal-spatial variation and the corresponding influence factors involved. The results show that the amount of precipitation
was abundant, but the spatial distribution was not consistent with it and the amount of precipitation gradually declined from
the south-east to the north-west in Sichuan Province, China. Moreover, the spatial distribution was different throughout the
years. The result of correlation analysis indicated that elevation, temperature and air pressure were three key factors affecting
the amount and distribution of precipitation, and the correlation coefficients were −0.56, 0.38 and 0.45 respectively. Notably,
the relationship between the slope of topography and precipitation were significantly negative and the average correlation
coefficient was −0.28. 相似文献
98.
Proctor David N.; Shen Peter H.; Dietz Niki M.; Eickhoff Tamara J.; Lawler Lori A.; Ebersold Ethan J.; Loeffler Darrell L.; Joyner Michael J. 《Journal of applied physiology》1998,85(1):68-75
It is currentlyunclear whether aging alters the perfusion of active muscles duringlarge-muscle dynamic exercise in humans. To study this issue, directmeasurements of leg blood flow (femoral vein thermodilution) andsystemic arterial pressure during submaximal cycle ergometry (70, 140, and 210 W) were compared between six younger (Y; 22-30 yr) and sixolder (O; 55-68 yr) chronically endurance-trainedmen. Whole body O2uptake, ventilation, and arterial and femoral venous samples forblood-gas, catecholamine, and lactate determinations were alsoobtained. Training duration (min/day), estimated leg muscle mass(dual-energy X-ray absorptiometry; Y, 21.5 ± 1.2 vs. O, 19.9 ± 0.9 kg), and blood hemoglobin concentration (Y, 14.9 ± 0.4 vs. O, 14.7 ± 0.2 g/dl) did not significantly differ (P > 0.05) between groups. Leg bloodflow, leg vascular conductance, and femoral venousO2 saturation were ~20-30%lower in the older men at each work rate (allP < 0.05), despite similarlevels of whole body O2 uptake. At210 W, leg norepinephrine spillover rates and femoral venous lactateconcentrations were more than twofold higher in the older men.Pulmonary ventilation was also higher in the older men at 140 (+24%)and 210 (+39%) W. These results indicate that leg blood flow andvascular conductance during cycle ergometer exercise are significantlylower in older endurance-trained men in comparison to their youngercounterparts. The mechanisms responsible for this phenomenon and theextent to which they operate in other groups of older subjects deservefurther attention. 相似文献
99.
Spatio-temporal tumour model for analysis and mechanism of action of intracellular drug accumulation
We have developed a one-dimensional tumour simulator to describe the biodistribution of chemotherapeutic drugs to a tumoral
lesion and the tumour cell’s response to therapy. A three-compartment model is used for drug dynamics within the tumour. The
first compartment represents the extracellular space in which cells move, the second corresponds to the intracellular fluid
space (including cell membrane) which is in direct equilibrium with the extracellular space, and the third is a non-exchangeable
compartment that represents sequestered drug which is trapped in the nucleus to damage the cellular DNA, directly triggering
cell death. Analytical and numerical techniques (Finite Element Method) are used to describe the tumour’s response to therapy
and the effect of parameter variation on the drug concentration profiles in the three compartments. 相似文献
100.
Diversity of halophilic microorganisms: Environments,phylogeny, physiology,and applications 总被引:13,自引:0,他引:13
Oren A 《Journal of industrial microbiology & biotechnology》2002,28(1):56-63
The phylogenetic diversity of microorganisms living at high salt concentrations is surprising. Halophiles are found in each
of the three domains: Archaea, Bacteria, and Eucarya. The metabolic diversity of halophiles is great as well: they include
oxygenic and anoxygenic phototrophs, aerobic heterotrophs, fermenters, denitrifiers, sulfate reducers, and methanogens. The
diversity of metabolic types encountered decreases with salinity. The upper salinity limit at which each dissimilatory process
takes place is correlated with the amount of energy generated and the energetic cost of osmotic adaptation. Our understanding
of the biodiversity in salt-saturated environments has increased greatly in recent years. Using a combination of culture techniques,
molecular biological methods, and chemotaxonomic studies, we have obtained information on the nature of the halophilic Archaea
as well as the halophilic Bacteria that inhabit saltern crystallizer ponds. Several halophilic microorganisms are being exploited
in biotechnology. In some cases, such as the production of ectoine, the product is directly related to the halophilic behavior
of the producing microorganism. In other cases, such as the extraction of β-carotene from Dunaliella or the potential use of Haloferax species for the production of poly-β-hydroxyalkanoate or extracellular polysaccharides, similar products can be obtained
from non-halophiles, but halophilic microorganisms may present advantages over the use of non-halophilic counterparts. Journal of Industrial Microbiology & Biotechnology (2002) 28, 56–63 DOI: 10.1038/sj/jim/7000176
Received 20 May 2001/ Accepted in revised form 20 June 2001 相似文献