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231.
Shibin Gao Carlos Martinez Debra J. Skinner Alan F. Krivanek Jonathan H. Crouch Yunbi Xu 《Molecular breeding : new strategies in plant improvement》2008,22(3):477-494
Leaf collection from the field, labeling and tracking back to the source plants after genotyping are rate limiting steps in
leaf DNA-based genotyping. In this study, an optimized genotyping method using endosperm DNA sampled from single maize seeds
was developed, which can be used to replace leaf DNA-based genotyping for both genetic studies and breeding applications.
A similar approach is likely to be suitable for all plants with relatively large seeds. Part of the endosperm was excised
from imbibed maize seeds and DNA extracted in 96-tube plates using individuals from eight F2 populations and seven inbreds. The quality of the resultant DNA was functionally comparable to DNA extracted from leaf tissue.
Extraction from 30 mg of endosperm yields 3–10 μg DNA, which is sufficient for analysis of 200–400 agarose-gel PCR-based markers,
with the potential for several million chip-based SNP marker analyses. By comparing endosperm DNA and leaf DNA for individuals
from an F2 population, genotyping errors caused by pericarp contamination and hetero-fertilization were found to average 3.8 and 0.6%,
respectively. Endosperm sampling did not affect germination rates under controlled conditions, although under normal field
conditions the germination rate, seedling establishment, and growth vigor were significantly lower than that of non-sampled
controls for some genotypes. However, careful field management can compensate for these effects. Seed DNA-based genotyping
lowered costs by 24.6% compared to leaf DNA-based genotyping due to reduced field plantings and labor costs. A substantial
advantage of this approach is that it can be used to select desirable genotypes before planting. As such it provides an opportunity
for dramatic improvements in the efficiency and selective gain of breeding systems based on optimum combinations of marker-assisted
selection and phenotypic selection within and between generations. 相似文献
232.
Luis Giménez-Benavides Raúl García-Camacho José María Iriondo Adrián Escudero 《Evolutionary ecology》2011,25(4):777-794
Under climate warming, plants will undergo novel selective pressures to adjust reproductive timing. Adjustment between reproductive
phenology and environment is expected to be higher in arctic and alpine habitats because the growing season is considerably
short. As early- and late-flowering species reproduce under very different environmental conditions, selective pressures on
flowering phenology and potential effects of climate change are likely to differ between them. However, there is no agreement
on the magnitude of the benefits and costs of early- vs. late-flowering species under a global warming scenario. In spite
of its relevance, phenotypic selection on flowering phenology has rarely been explored in alpine plants and never in Mediterranean
high mountain species, where selective pressures are very different due to the summer drought imposed over the short growth
season. We hypothesized that late-flowering plants in Mediterranean mountains should present stronger selective pressures
towards early onset of reproduction than early-flowering species, because less water is available in the soil as growing season
progresses. We performed selection analyses on flowering onset and duration in two high mountain species of contrasting phenology.
Since phenotypic selection can be highly context-dependent, we studied several populations of each species for 2 years, covering
their local altitudinal ranges and their different microhabitats. Surrogates of biotic selective agents, like fruitset for
pollinators and flower and fruit loss for flower and seed predators, were included in the analysis. Differences between the
early- and the late-flowering species were less than expected. A consistent negative correlational selection of flowering
onset and duration was found affecting plant fitness, i.e., plants that bloomed earlier flowered for longer periods improving
plant fitness. Nevertheless, the late-flowering species may experience higher risks under climate warming because in extremely
warm and dry years the earlier season does not bring about a longer flowering duration due to summer drought. 相似文献
233.
This proof-of-concept study explores the feasibility of using a drug-loaded hydrophilic polymeric layer sandwiched between two hydrophobic layers for improving film drug load while achieving sustained release of poorly water-soluble drug. Such films having total thickness in range ~?146–250 μm were prepared by slurry-based casting using hydrophilic hydroxypropyl methylcellulose (HPMC) as matrix layer containing fenofibrate (FNB) as the model drug, encased between two very thin rate-limiting layers of 10 μm each of hydrophobic poly-?-caprolactone (PCL). Film precursor slurry consisted of HPMC with plasticizer and water along with micronized FNB powders, which were dry-coated with hydrophilic silica. Characterization techniques demonstrated the presence of homogeneously dispersed crystalline FNB in films. The films are very thin and hence two-dimensional; hence, average drug load per unit area in range ~?5 to ~?9 mg/cm2 could be achieved by altering the thickness of the drug matrix layer. Drug amount and drug content uniformity were measured through assay of ten circular samples ~?0.712 cm2 in area punched out using a circular-shaped punch tool. Drug release rate was investigated using USP IV flow-through cell and surface dissolution imaging system. Thinner films followed Fickian diffusion, and thicker films followed non-Fickian anomalous diffusion. Overall, the application of middle layer thickness could be used as a tool to manipulate drug load without the need for altering its formulation or precursor preparation by changing its thickness, hence achieving relatively high drug loading yet having sustained release of drug. 相似文献
234.
235.
Zhong L Guo XN Zhang XH Wu ZX Luo XM Jiang HL Lin LP Zhang XW Ding J 《Biochimica et biophysica acta》2005,1722(3):254-261
Vascular endothelial growth factor (VEGF), an endothelial cell-specific mitogen, can act in tumor-induced angiogenesis by binding to specific receptors on the surface of endothelial cells. One such receptor, VEGFR-2/KDR, plays a key role in VEGF-induced angiogenesis. Here, we expressed the catalytic domain of VEGFR-2 as a soluble active kinase using Bac-to-Bac expression system, and investigated correlations between VEGFR-2 activity and enzyme concentration, ATP concentration, substrate concentration and divalent cation type. We used these data to establish a convenient, effective and non-radioactive ELISA screening technique for the identification and evaluation of potential inhibitors for VEGFR-2 kinase. We screened 200 RTK target-based compounds and identified one (TKI-31) that potently inhibited VEGFR-2 kinase activity (IC50=0.596 microM). Treatment of NIH3T3/KDR cells with TKI-31 blocked VEGF-induced phosphorylation of KDR in a dose-dependent manner. Moreover, TKI-31 dose-dependently suppressed HUVEC tube formation. Thus, we herein report a novel, efficient method for identifying VEGFR-2 kinase inhibitors and introduce one, TKI-31, that may prove to be a useful new angiogenesis inhibitor. 相似文献
236.
绵羊肌肉中FAS基因和HSL基因的发育性变化及其对肌内脂肪含量的影响 总被引:4,自引:0,他引:4
选取不同日龄的雄性哈萨克羊和新疆细毛羊共54只,屠宰后取背最长肌,用索氏抽提法检测肌内脂肪(intramuscular fat,IMF)含量,用荧光实时定量PCR法检测肌肉脂肪酸合成酶(fatty acid synthase,FAS)和激素敏感脂肪酶(hormone-sensitive lipase,HSL)基因表达的发育性变化,并分析基因表达对肌内脂肪沉积的影响。结果表明:1)随着日龄的增加,雄性哈萨克羊的IMF含量持续上升,各生长时期差异显著(P<0.05),而新疆细毛羊的IMF含量在各生长时期无显著差异(P>0.05)。雄性哈萨克羊的IMF含量30~90日龄期间极显著高于新疆细毛羊(P<0.01)。2)FAS基因mRNA水平在哈萨克羊肌肉中初生时最高(P<0.05),然后随日龄的增加呈下降趋势;在新疆细毛羊肌肉中,FAS mRNA水平表现出"下降-上升-下降-上升"的发育模式,其中60日龄显著高于90日龄(P<0.05),其余日龄之间差异不显著。HSL基因在2品种绵羊肌肉中的表达模式基本类似,在哈萨克羊肌肉中随年龄的增加而下降,初生时的水平显著高于60~90日龄(P<0.05);在新疆细毛羊中30日龄时达到最高(P<0.01),到60日龄时下降到最低(P<0.05),随后保持这种低表达水平。3)FAS和HSL基因mRNA的表达量均与哈萨克羊IMF含量呈负相关,相关系数分别为:r=-0.485(P=0.02),r=-0.423(P=0.05);在哈萨克羊中两基因表达量水平比值(FAS:HSL)与IMF呈极显著负相关r=-0.552(P=0.01)。在新疆细毛羊中两基因的表达水平及比值均与IMF无显著相关性(P>0.05)。 相似文献
237.
Yanming Sun Ruofeng Yan Charles I. Muleke Guangwei Zhao lixin Xu Xiangrui Li 《International journal of peptide research and therapeutics》2007,13(3):387-392
The effect of Haemonchus contortus galectin peptides rHco-gal-m/f to induce apoptosis in the peripheral blood lymphocytes (PBLCs) of goats was investigated. Analysis of apoptosis was
carried out with agarose gel electrophoresis, flow cytometry and transmission electron microscopy. The results indicated that
there were visible apoptosis bodies and typical DNA ladders by genomic DNA fragmentation. The quantitative analysis of apoptosis
by flow cytometry indicated that rHco-gal-m/f peptides induced apoptosis was time and dose dependent. Ultrastructural studies of the PBLCs revealed that a large
number of apoptotic cells were present in galectin-treated cells, which had the typical morphologic changes of apoptosis such
as reduction of the cytoplasmic volume, loss of cell surface microvilli, chromatin condensation and fragmentation of the apoptotic
cells into small apoptotic bodies. 相似文献
238.
Background
Profile hidden Markov models (profile-HMMs) are sensitive tools for remote protein homology detection, but the main scoring algorithms, Viterbi or Forward, require considerable time to search large sequence databases. 相似文献239.
In this study, an aqueous extract of leaves from Melothria maderaspatana was tested for in vitro antioxidant activity. Free radical scavenging assays, such as hydroxyl radical, hydrogen peroxide, superoxide anion radical
and 2,2-diphenyl-1-picryl hydrazyl (DPPH), 2,2’-azinobis-(3-ethyl-enzothiazoline-6-sulfonic acid) (ABTS) radical scavenging,
and reducing power assay, were studied. The extract effectively scavenged hydroxyl radical, hydrogen peroxide and superoxide
anion radicals. It also scavenged DPPH and ABTS radicals. Furthermore, it was found to have reducing power. All concentrations
of leaf extract exhibited free radical scavenging and antioxidant power, and the preventive effects were in a dose-dependent
manner. The antioxidant activities of the above were compared to standard antioxidants such as butylated hydroxytoluene (BHT),
ascorbic acid, and α-tocopherol. The results obtained in the present study indicate that the M. maderaspatana extract could be considered a potential source of natural antioxidant. 相似文献
240.
Osamu Nunobiki Daisuke Sano Kyoko Akashi Taro Higashida Toshitada Ogasawara Hikari Akise Shinji Izuma Kiyo Torii Yoshiaki Okamoto Ichiro Tanaka Masatsugu Ueda 《Human cell》2016,29(2):91-95
To investigate the clinical significance of ALDH2 genetic polymorphisms in cervical carcinogenesis. ALDH2 polymorphisms together with human papillomavirus (HPV) types were examined in a total of 195 cervical smear in exfoliated cervical cell samples using Real-Time polymerase chain reaction (PCR) System. The frequency for the AG+AA genotype was seven in the normal group (70.0 %), 16 in the LSIL group (57.1 %), and 27 in the HSIL group (90.0 %). A significant difference was found between the LSIL and HSIL groups (P = 0.0064). Patients with HSIL lesions frequently had high-risk HPV infections and concurrently belonged to the AG+AA group. ALDH2 genotype in cervical cell samples may be associated with more severe precancerous lesions of the cervix in a Japanese population. 相似文献