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551.
Burdette JE Chen SN Lu ZZ Xu H White BE Fabricant DS Liu J Fong HH Farnsworth NR Constantinou AI Van Breemen RB Pezzuto JM Bolton JL 《Journal of agricultural and food chemistry》2002,50(24):7022-7028
The roots/rhizomes of Cimicifuga racemosa L. (Nutt.) (black cohosh) have traditionally been used to treat menopausal symptoms through an unknown mechanism of action. In an effort to determine if black cohosh had additional health benefits, methanol extracts were investigated for their potential to scavenge reactive oxygen species and to protect against menadione-induced DNA damage. These extracts effectively scavenged 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals. In addition, the extracts showed dose-dependent decreases in DNA single-strand breaks and oxidized bases induced by the quinone menadione using the comet (single-cell gel electrophoresis assay) and fragment length associated repair enzyme assays, respectively. Bioassay-directed fractionation of the methanolic extracts using the DPPH assay as a monitor led to the isolation of nine antioxidant active compounds: caffeic acid (1), methyl caffeate (2), ferulic acid (3), isoferulic acid (4), fukinolic acid (5), cimicifugic acid A (6), cimicifugic acid B (7), cimicifugic acid F (8), cimiracemate A (9), and cimiracemate B (10). Six of these antioxidants were found to reduce menadione-induced DNA damage in cultured S30 breast cancer cells with the following order of potency: methyl caffeate (2) > caffeic acid (1) > ferulic acid (3) > cimiracemate A (9) > cimiracemate B (10) > fukinolic acid (5). These data suggest that black cohosh can protect against cellular DNA damage caused by reactive oxygen species by acting as antioxidants. 相似文献
552.
Micropatterning of single crystals for technological applications is a complex, multistep process. Nature provides alternative fabrication strategies, when crystals with exquisite micro-ornamentation directly develop within preorganized frameworks. We report a bio-inspired approach to growing large micropatterned single crystals. Micropatterned templates organically modified to induce the formation of metastable amorphous calcium carbonate were imprinted with calcite nucleation sites. The template-directed deposition and crystallization of the amorphous phase resulted in the fabrication of millimeter-sized single calcite crystals with sub-10-micron patterns and controlled crystallographic orientation. We suggest that in addition to regulating the shape, micropatterned frameworks act as sites for stress and impurity release during the amorphous-to-crystalline transition. The proposed mechanisms may have direct biological relevance and broad implications in materials synthesis. 相似文献
553.
van de Koppel J Gascoigne JC Theraulaz G Rietkerk M Mooij WM Herman PM 《Science (New York, N.Y.)》2008,322(5902):739-742
Spatial self-organization is the main theoretical explanation for the global occurrence of regular or otherwise coherent spatial patterns in ecosystems. Using mussel beds as a model ecosystem, we provide an experimental demonstration of spatial self-organization. Under homogeneous laboratory conditions, mussels developed regular patterns, similar to those in the field. An individual-based model derived from our experiments showed that interactions between individuals explained the observed patterns. Furthermore, a field study showed that pattern formation affected ecosystem-level processes in terms of improved growth and resistance to wave action. Our results imply that spatial self-organization is an important determinant of the structure and functioning of ecosystems, and it needs to be considered in their conservation. 相似文献
554.
The intracellular distribution of fluorine has been delineated in human platelets incubated with 4,6-difluoroserotonin, utilizing a scanning-transmission electron microscope equipped with an energy-loss spectrometer. Discrete intracellular structures corresponding in location to dense bodies contained high concentrations of fluorine. Electron energy-loss spectroscopy, which apparently can detect less than 10(-20) gram of fluorine in an area of 10 square nonometers, can thus localize fluorinated tracer molecules with biological activity. 相似文献
555.
Climate change is predicted to become a major threat to biodiversity in the 21st century, but accurate predictions and effective solutions have proved difficult to formulate. Alarming predictions have come from a rather narrow methodological base, but a new, integrated science of climate-change biodiversity assessment is emerging, based on multiple sources and approaches. Drawing on evidence from paleoecological observations, recent phenological and microevolutionary responses, experiments, and computational models, we review the insights that different approaches bring to anticipating and managing the biodiversity consequences of climate change, including the extent of species' natural resilience. We introduce a framework that uses information from different sources to identify vulnerability and to support the design of conservation responses. Although much of the information reviewed is on species, our framework and conclusions are also applicable to ecosystems, habitats, ecological communities, and genetic diversity, whether terrestrial, marine, or fresh water. 相似文献
556.
557.
Harris RG Herzog EL Bruscia EM Grove JE Van Arnam JS Krause DS 《Science (New York, N.Y.)》2004,305(5680):90-93
Analysis of developmental plasticity of bone marrow-derived cells (BMDCs) is complicated by the possibility of cell-cell fusion. Here we demonstrate that epithelial cells can develop from BMDCs without cell-cell fusion. We use the Cre/lox system together with beta-galactosidase and enhanced green fluorescent protein expression in transgenic mice to identify epithelial cells in the lung, liver, and skin that develop from BMDCs without cell fusion. 相似文献
558.
Michalak J Gujska E Klepacka J 《Plant foods for human nutrition (Dordrecht, Netherlands)》2011,66(4):307-312
The influence that food heating has on the concentration of acrylamide in home-cooked potato dishes prepared by high-temperature,
such as pan-frying, deep-frying, roasting and microwave heating was analyzed. The experiment was performed with commercially
available deep-frozen par-fried French fries and deep-frozen par-fried potato products other than French fries (cubes, wedges,
noisettes, pancakes). Acrylamide was found in all deep-frozen par-fried French fries and other deep-frozen par-fried potato
products before domestic preparation. The mean level of acrylamide content in all frozen potato products before preparation
was found to be 322 μg/kg. Potato products were then prepared at 180 °C for 3 min and at 220 °C for 10 min. After domestic
preparation (roasting, pan-frying, deep-frying and microwave heating) it was found that the level of acrylamide in all products
increased. Acrylamide content in the analyzed samples significantly increased as the temperature and time of processing increased.
The statistical analysis showed significant differences (P < 0.05) for acrylamide content as a function of food preparation. The level of acrylamide increased with the increased heating
temperature and heating time. Additionally, the preparation method of roasting was significantly lower in acrylamide content
(P < 0.05) than the preparation method of microwaving although both preparation methods used the same conditions (time and temperature).
These results suggest that microwaving might be more favourable to the formation of acrylamide than conventional heating methods,
such as roasting. 相似文献
559.
560.
Klepacka J Gujska E Michalak J 《Plant foods for human nutrition (Dordrecht, Netherlands)》2011,66(1):64-69
The aim of the study was to determine whether phenolic compounds in some varieties of buckwheat, winter and spring barley
and peas can be used as factors which distinguish selected cultivars and varieties of plant material. It was observed that
the content of total phenolics might be useful as a cultivar-distinguishing factor for all the plant materials analyzed, but
it was a distinguishing factor for only some varieties. Individual cultivars and varieties were best distinguished by the
content of syringic acid. The levels of syringic and vanillic acids were in reverse proportion to the total amount of phenolics
soluble in methanol and a positive correlation between syringic and ferulic acid was observed. Moreover, the protein content
of plant material was analyzed and a significant (p ≤ 0.05) correlation between this component and ferulic and vanillic acids was noted. 相似文献