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311.
Wenxiu Wei Shida Li Hongmei Xu Feilong Zhou Yi Wen Zhimei Song Sijia Feng Runliang Feng 《AAPS PharmSciTech》2018,19(5):2041-2047
Macrolide antibiotics are lipophilic drugs with some limitations including low solubility, limited cellular permeation, patients discomfort, etc. With amphiphilic methoxy poly(ethylene glycol)-b-poly(ε-caprolactone) (MPEG-PCL) copolymer and azithromycin (AZT) as drug carrier and model drug, AZT-loaded micelles were prepared via thin-membrane hydration method in order to overcome these limitations. Encapsulation efficiency of AZT-loaded micelles was 94.40% with good storage stability for 28 days, and AZT’s water solubility was enhanced to 944 μg/mL. Fourier transform infrared spectrum and x-ray diffraction analysis indicated that AZT was enveloped into the micelles in amorphous form due to its interaction with the copolymer. AZT’s in vitro release from the AZT-loaded micelles demonstrated a slow and continuous behavior when compared with raw AZT. The release dynamics was accorded with Weibull equation, meaning that release amount of AZT lowered with time and was proportional to remaining amount of drug in the AZT-loaded micelles. Korsmeyer-Peppas fitting result suggested that drug release process was a classical Fickian diffusion-controlled manner. With Staphylococcus aureus as bacterial strain, antibacterial activity of the AZT-loaded micelles displayed was comparable with raw AZT. In conclusion, MPEG-PCL should be a promising carrier for macrolide antibiotic delivery in treatment of bacterial infections. 相似文献
312.
Jie Dai Jun Zhou Hongmei Liu Kaixun Huang 《Journal of biological inorganic chemistry》2016,21(8):1037-1046
Selenite and ebselen supplementation has been shown to possess anti-cataract potential in some experimental animal models of cataract, however, the underlying mechanisms remain unclear. The present study was designed to evaluate the anti-cataract effects and the underlying mechanisms of selenite and ebselen supplementation on galactose induced cataract in rats, a common animal model of sugar cataract. Transmission electron microscopy images of lens fiber cells (LFC) and lens epithelial cells (LEC) were observed in d-galactose-induced experimental cataractous rats treated with or without selenite and ebselen, also redox homeostasis and expression of proteins such as selenoprotein R (SELR), 15kD selenoprotein (SEP15), superoxide dismutase 1 (SOD1), catalase (CAT), β-crystallin protein, aldose reductase (AR) and glucose-regulated protein 78 (GRP78) were estimated in the lenses. The results showed that d-galactose injection injured rat lens and resulted in cataract formation; however, selenite and ebselen supplementation markedly alleviated ultrastructural injury of LFC and LEC. Moreover, selenite and ebselen supplementation could mitigate the oxidative damage in rat lens and increase the protein expressions of SELR, SEP15, SOD1, CAT and β-crystallin, as well as decrease the protein expressions of AR and GRP78. Taken together, these findings for the first time reveal the anti-cataract potential of selenite and ebselen in galactosemic cataract, and provide important new insights into the anti-cataract mechanisms of selenite and ebselen in sugar cataract. 相似文献
313.
Sedimentary Factors are Key Predictors of Carbon Storage in SE Australian Saltmarshes 总被引:1,自引:0,他引:1
Although coastal vegetated ecosystems are widely recognised as important sites of long-term carbon (C) storage, substantial spatial variability exists in quantifications of these ‘blue C’ stocks. To better understand the factors behind this variability we investigate the relative importance of geomorphic and vegetation attributes to variability in the belowground C stocks of saltmarshes in New South Wales (NSW), southeast Australia. Based on the analysis of over 140 sediment cores, we report mean C stocks in the surface metre of sediments (mean ± SE = 164.45 ± 8.74 Mg C ha?1) comparable to global datasets. Depth-integrated stocks (0–100 cm) were more than two times higher in fluvial (226.09 ± 12.37 Mg C ha?1) relative to marine (104.54 ± 7.11) geomorphic sites, but did not vary overall between rush and non-rush vegetation structures. More specifically, sediment grain size was a key predictor of C density, which we attribute to the enhanced C preservation capacity of fine sediments and/or the input of stable allochthonous C to predominantly fine-grained, fluvial sites. Although C density decreased significantly with sediment depth in both geomorphic settings, the importance of deep C varied substantially between study sites. Despite modest spatial coverage, NSW saltmarshes currently hold approximately 1.2 million tonnes of C in the surface metre of sediment, although more C may have been returned to the atmosphere through habitat loss over the past approximately 200 years. Our findings highlight the suitability of using sedimentary classification to predict blue C hotspots for targeted conservation and management activities to reverse this trend. 相似文献
314.
Rodolfo Jaffé Antonio Castilla Nathaniel Pope Vera Lucia Imperatriz-Fonseca Jean Paul Metzger Maria Cristina Arias Shalene Jha 《Conservation Genetics》2016,17(2):267-278
Pollination services are increasingly threatened by the loss and modification of natural habitats, posing a risk to the maintenance of both native plant biodiversity and agricultural production. In order to safeguard pollination services, it is essential to examine the impacts of habitat degradation on the population dynamics of key pollinators and identify potential “rescue pollinators” capable of persisting in these human-altered landscapes. Using a landscape genetic approach, we assessed the impact of landscape structure on genetic differentiation in the widely-distributed tropical stingless bee Trigona spinipes (Apidae: Meliponini) across agricultural landscape mosaics composed of coffee plantations and Atlantic forest fragments in southeastern Brazil. We genotyped 115 bees at 16 specific and highly polymorphic microsatellite loci, developed using next-generation sequencing. Our results reveal that T. spinipes is capable of dispersing across remarkably long distances, as we did not find genetic differentiation across a 200 km range, nor fine-scale spatial genetic structure. Furthermore, gene flow was not affected by forest cover, land cover, or elevation, indicating that reproductive individuals are able to disperse well through agricultural landscapes and across altitudinal gradients. We also found evidence of a recent population expansion, suggesting that this opportunistic stingless bee is capable of colonizing degraded habitats. Our results thus suggest that T. spinipes can persist in heavily-altered landscapes and can be regarded as a rescue pollinator, potentially compensating for the decline of other native pollinators in degraded tropical landscapes. 相似文献
315.
Lee CH 《Applied microbiology and biotechnology》2012,93(2):517-523
One of the primary limitations of cancer therapy is lack of selectivity of therapeutic agents to tumor cells. Current efforts
are focused on discovering and developing anticancer agents that selectively target only tumor cells and spare normal cells
to improve the therapeutic index. The use of preferentially replicating bacteria as an oncolytic agent is one of the innovative
approaches for the treatment of cancer. This is based on the observation that some obligate or facultative anaerobic bacteria
are capable of multiplying selectively in tumors and inhibiting their growth. Meanwhile, bacteria have been demonstrated to
colonize and destroy tumor, and have emerged as biological gene vectors to tumor microenvironment. To improve the efficacy
and safety of the bacterial therapy, a further understanding of bacteria between with immune system is required. Furthermore,
we want to evaluate how bacterial infection facilitates the “bystander effect” of chemotherapeutic agent and assess if it
can be used for additional antitumor effect when combined with chemotherapy. This study may not only evaluate therapeutic
efficacy of bacteria for the treatment of cancer but also elucidate the mechanisms underlying antitumor activities mediated
by bacteria, which involve host immune responses and the cellular molecular responses. 相似文献
316.
Immune suppression remains a consistent obstacle to successful anti-tumor immune responses. As tumors develop, they create
a microenvironment that not only supports tumor growth and metastasis but also reduces potential adaptive immunity to tumor
antigens. Among the many components of this tumor microenvironment is a population of dendritic cells which exert profound
immune suppressive effects on T cells. In this review, we discuss our recent findings related to these tumor-associated dendritic
cells and how targeting them may serve to generate more durable anti-tumor immune responses. 相似文献
317.
In contrast to many studies on the habitat quality of road verges for butterflies in relation to management regimes, little
is known about whether road verges also function as corridors linking fragmented grassland habitats. We experimentally compared
movements of four model species, two small blues and two medium browns, with one habitat specialist and one habitat generalist
in each size and phylogenetic category. A total of 425 individual butterflies were caught and translocated to an experimental
arena with three 2 × 30 m grassland strips that approximated road verges; one with adult feeding resources, one sheltered
from the wind, and one without food and shelter. Movements in grassland strips were compared to movements in continuous grassland
habitat. Results indicated that (1) individuals did not use the low-quality strip, (2) only specialists used strips but not
in the same way according to their size and phylogenic category, and (3) strip use could not be predicted from habitat selection.
This finding supports the idea that corridors of intermediate quality are the most efficient to promote dispersal rates in
fragmented landscapes. Road verges cover 250,000 ha in Sweden, which is nearly the total amount of seminatural grasslands.
Our results suggest that, to benefit butterfly dispersal among grassland patches, road verges should be managed to create
a more favourable microclimate (e.g. sheltered from wind, high temperatures). 相似文献
318.
Lynn S. Dahleen Muthusamy Manoharan 《In vitro cellular & developmental biology. Plant》2007,43(6):493-506
Barley, an important member of the cereals, has been successfully transformed through various methods such as particle bombardment,
Agrobacterium tumefaciens, DNA uptake, and electroporation. Initially, the transformation in barley concentrated on developing protocols using marker
genes such as gus, bar, and hpt. Immature embryos and callus derived from immature embryos were targeted for transformation. Subsequently, genes of agronomic
and malting importance have been deployed in barley. Particle bombardment appears to be the preferred choice for barley transformation
in the majority of the reports, although Agrobacterium-mediated transformation is being used more often. The current review focuses on the challenges encountered in barley transformation
such as somaclonal variation, development of transformation systems for commercial cultivars, gene expression, stability and
inheritance, and gene flow. Newer markers such as the green fluorescent protein (gfp), firefly luciferase, and phosphomannose isomerase were found to be useful in the selection of transgenic plants. Tissue-specific
promoters such as those for B1-hordein and D-hordein genes, and spike-specific promoters, are increasingly used to drive gene
expression. The review also describes recent research on gene-tagging through transformation, insertion of disease resistance,
and abiotic stress resistance genes, transformation with genes for improved malting quality, nutrient content, feed quality,
and the production of feed enzymes and pharmaceutical compounds. 相似文献
319.
The red king crab (Paralithodes camtschaticus) was introduced in the Barents Sea in the 1960s and soon established a viable population. Proper management and exploitation
of the Barents Sea king crab stock require better understanding of the spatial dynamics at different scales. This study examines
the small-scale movement patterns of seven adult male crabs tracked for a period of up to one month from mid July to mid August
at 150 m depth in a semi-enclosed fjord on the Russo-Norwegian border. The crabs were tagged with acoustic transmitters and
their movements monitored with an acoustic positioning system. Low walking speeds (<0.01 m s−1) were most frequent but the crabs could move at a maximum speed of 0.15 m s−1 and walk an actual distance of up to 270 m over a period of one hour. However, the crabs usually moved within a relatively
restricted area with mean hourly longest rectilinear distance varying from 26 to 64 m. The crabs alternated between periods
of low and high activity, which could reflect feeding in and movements between food patches. The lack of a diel activity rhythm
may be due to high light levels during the polar summer night, or a chemically mediated food search strategy. 相似文献
320.
Cindy Q. Tang Mei-Hua Zhao Xiao-Shuang Li Masahiko Ohsawa Xiao-Kun Ou 《Ecological Research》2010,25(1):149-161
Since 1985, originally forested mountainous areas of China have been allowed to return to their natural state after years
of exploitation including agriculture, development, and logging. The reforms began earlier in less accessible locations, so
that today the successional process is more advanced there. The vegetation in Luquan, Qiongzhusi, and Xishan near Kunming,
central Yunnan, exhibits, in a limited area, a range of stages of plant succession that are widely encountered throughout
the broader region, and thus affords a special opportunity for a comprehensive study. We analyzed the successional sequence
of these various plant communities. They ranged from pioneer coniferous and/or pioneer deciduous broad-leaved stands to pre-mature
semi-humid evergreen broad-leaved stands, through mixed coniferous and broad-leaved or mixed deciduous and evergreen broad-leaved
stands. The succession proceeded from pioneer coniferous Pinus and Keteleeria, and deciduous Platycarya and Alnus, to late-successional evergreen broad-leaved Cyclobalanopsis and Castanopsis. Two regeneration types of woody species in either the early successional (15–50 years), the mid-successional (40–80 years),
or the late-successional (80–180 years) stage were classified. Relatively high species diversity was found in the seral phase
at the three study sites. The late-successional stage was commonest where human disturbance was least evident. Poor soil chemical
properties under pioneer Pinus were seen as a limitation to plant growth, while the abundance of Alnus at the early stage led to an improved level of organic matter and nitrogen. 相似文献