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排序方式: 共有833条查询结果,搜索用时 15 毫秒
91.
Novel omega-conotoxins from Conus catus discriminate among neuronal calcium channel subtypes 总被引:1,自引:0,他引:1
Lewis RJ Nielsen KJ Craik DJ Loughnan ML Adams DA Sharpe IA Luchian T Adams DJ Bond T Thomas L Jones A Matheson JL Drinkwater R Andrews PR Alewood PF 《The Journal of biological chemistry》2000,275(45):35335-35344
omega-Conotoxins selective for N-type calcium channels are useful in the management of severe pain. In an attempt to expand the therapeutic potential of this class, four new omega-conotoxins (CVIA-D) have been discovered in the venom of the piscivorous cone snail, Conus catus, using assay-guided fractionation and gene cloning. Compared with other omega-conotoxins, CVID has a novel loop 4 sequence and the highest selectivity for N-type over P/Q-type calcium channels in radioligand binding assays. CVIA-D also inhibited contractions of electrically stimulated rat vas deferens. In electrophysiological studies, omega-conotoxins CVID and MVIIA had similar potencies to inhibit current through central (alpha(1B-d)) and peripheral (alpha(1B-b)) splice variants of the rat N-type calcium channels when coexpressed with rat beta(3) in Xenopus oocytes. However, the potency of CVID and MVIIA increased when alpha(1B-d) and alpha(1B-b) were expressed in the absence of rat beta(3), an effect most pronounced for CVID at alpha(1B-d) (up to 540-fold) and least pronounced for MVIIA at alpha(1B-d) (3-fold). The novel selectivity of CVID may have therapeutic implications. (1)H NMR studies reveal that CVID possesses a combination of unique structural features, including two hydrogen bonds that stabilize loop 2 and place loop 2 proximal to loop 4, creating a globular surface that is rigid and well defined. 相似文献
92.
L. C. Emebiri M. E. Devey A. C. Matheson M. U. Slee 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,97(7):1062-1068
NESTUR (needle-to-stem unit rate) is a stem growth index of conifer seedlings that measures the efficiency of stemwood production
per unit of needle growth, and is related to other seedling traits such as height, stem diameter, stem volume and needle volume.
Quantitative trait loci (QTLs) affecting the expression of stem growth efficiency in radiata pine seedlings were investigated
using a RAPD linkage map constructed from markers scored on haploid, megagametophytic DNA. Four putative QTLs were detected
which accounted for 8.5–36.4% of the population variance. A search for evidence of epistasis, using both complete pairwise
and conditional interactions, did not yield any statistically significant result. Over a 3-year period, seedlings with high-NESTUR
marker alleles showed a superior growth performance of 17–40% for height, diameter and volume over those with low-NESTUR marker
alleles.
Received: 10 July 1997 / Accepted: 31 March 1998 相似文献
93.
Matheson Melissa; Rynell Ann-Christine; McClean Melissa; Berend Norbert 《Journal of applied physiology》1998,84(1):77-81
Matheson, Melissa, Ann-Christine Rynell, Melissa McClean,and Norbert Berend. Relationship between airway microvascular leakage, edema, and baseline airway functions. J. Appl. Physiol. 84(1): 77-81, 1998.This study wasdesigned to examine the relationship among microvascular leakage,edema, and baseline airway function. Microvascular leakage was inducedin the airways of anesthetized, tracheostomized New Zealand Whiterabbits (n = 22) by using nebulized N-formyl-methionyl-leucyl-phenylalanine(10 mg) and was measured in the trachea by using the Evans blue dyetechnique. Airway wall thickness was assessed morphometrically in theright main bronchus after Formalin fixation at a pressure of 25 cmH2O. Areas calculated includedthe mucosal wall area, the adventitial wall area, the total wall area,and the percentage of total wall area consisting of blood vessels. Aneutrophil count was also performed by analyzing numbers of cells inboth the mucosal wall area and the adventitial wall area. Airwayfunction was assessed before and 30 min after challenge withN-formyl-methionyl-leucyl-phenylalanineby determining airway resistance, functional residual capacity,specific airway resistance, and flow-volume and pressure-volume curves(after paralysis of the animals with suxamethonium). The concentration of Evans blue dye in tracheal tissue ranged from 31.3 to 131.2 µg.There was a significant correlation between this concentration and boththe adventitial wall area (P < 0.01)and mucosal neutrophil numbers (P < 0.005). There was no correlation between Evans blue concentration andeither blood vessel area or changes in respiratory physiologyparameters before and after challenge. There was no significantdifference between any respiratory physiology measurements before andafter challenge. We conclude that an increase in microvascular leakagecorrelates with airway edema in the adventitia; however, these airwaychanges have no significant effect on airway elastic or resistiveproperties. 相似文献
94.
Cypermethrin, a synthetic pyrethroid insecticide is shown to exert carcinogenic effects in rodents; however, its underlying mechanism remains elusive. Here, we showed the effect of cypermethrin on protein expression involved in neoplastic transformation in mouse skin. Comparative protein expression profiles between untreated control and cypermethrin-treated mouse skin were explored using 2-DE. A total of 27 spots that were statistically significant (p<0.05) and differentially expressed in response to cypermethrin exposure were identified by MALDI-TOF/TOF and LC-MS/MS. Among them, six up-regulated proteins (carbonic anhydrase 3 (Ca 3), Hsp-27, S100A6, galectin-7, S100A9, S100A11) and one down-regulated protein (superoxide dismutase [Cu-Zn] (Sod 1)) are associated with cancer-related key processes. These selected dysregulated proteins were further validated in 2-DE gels of mouse skin treated with known tumorigens (benzo-[a]-pyrene, 12-O-tetradecanoyl-phorbol-13-acetate and mezerein), respectively. Comparative studies showed that Ca 3, S100A6, S100A9, S100A11 and Sod 1 are specific for stages of development and progression of tumors whereas Hsp-27 and galectin-7 are specific for tumor promotion stage by cypermethrin in mouse skin. Furthermore, these chosen proteins confirmed by Western blotting and immunofluorescence staining were consistent with changes in 2-DE check. This proteomic investigation for the first time provides key proteins that will contribute in understanding the mechanism behind cypermethrin-induced neoplastic transformation. 相似文献
95.
Tu Z Aird KM Bitler BG Nicodemus JP Beeharry N Xia B Yen TJ Zhang R 《Developmental cell》2011,21(6):1077-1091
Here, we report a cell-intrinsic mechanism by which oncogenic RAS promotes senescence while predisposing cells to senescence bypass by allowing for secondary hits. We show that oncogenic RAS inactivates the BRCA1 DNA repair complex by dissociating BRCA1 from chromatin. This event precedes senescence-associated cell cycle exit and coincides with the accumulation of DNA damage. Downregulation of BRIP1, a physiological partner of BRCA1 in the DNA repair pathway, triggers BRCA1 chromatin dissociation. Conversely, ectopic BRIP1 rescues BRCA1 chromatin dissociation and suppresses RAS-induced senescence and the DNA damage response. Significantly, cells undergoing senescence do not exhibit a BRCA1-dependent DNA repair response when exposed to DNA damage. Overall, our study provides a molecular basis by which oncogenic RAS promotes senescence. Because DNA damage has the potential to produce additional "hits" that promote senescence bypass, our findings may also suggest one way a small minority of cells might bypass senescence and contribute to cancer development. 相似文献
96.
Acetone extract of Elephantopus scaber, an ethnomedicnal plant, reduced the blood glucose levels in streptozotocin-induced diabetic rats significantly. Acute toxicity studies revealed the non-toxic nature of the crude extract. Fractionation of the acetone extract yielded a new steroid, 28Nor-22(R)Witha 2,6,23-trienolide. Biological testing of the compound demonstrated a significant antidiabetic activity by reducing the elevated blood glucose levels and restoring the insulin levels in streptozotocin-induced diabetic rats. This compound can be a useful candidate to treat diabetes. 相似文献
97.
Subularia aquatica is a small annual aquatic plant in the family Brassicaceae with unique leaf morphology. Its anatomical features were studied using light microscopy. We show that the leaves of S. aquatica are bifacial dorsiventral phyllodes, having adaxial-abaxial polarity, rather than the alternative unifacial type. This morphology is also manifested in the collaterally arranged vascular bundles, which are clearly bifacial. The roots exhibit typical anatomical features of an aquatic plant, including prominent aerenchyma. Although unique within the Brassicaceae, S. aquatica displays many of the same morphological characteristics as other Isoetid life-forms. 相似文献
98.
Brooks ES Greer CL Romero-Calderón R Serway CN Grygoruk A Haimovitz JM Nguyen BT Najibi R Tabone CJ de Belle JS Krantz DE 《Neuron》2011,72(2):316-329
Vesicular transporters are required for the storage of?all classical and amino acid neurotransmitters in synaptic vesicles. Some neurons lack known vesicular transporters, suggesting additional neurotransmitter systems remain unidentified. Insect mushroom bodies (MBs) are critical for several behaviors, including learning, but the neurotransmitters released by the intrinsic Kenyon cells (KCs) remain unknown. Likewise, KCs do not express a known vesicular transporter. We report the identification of a novel Drosophila gene portabella (prt) that is structurally similar to known vesicular transporters. Both larval and adult brains express PRT in the KCs of the MBs. Additional PRT cells project to the central complex and optic ganglia. prt mutation causes an olfactory learning deficit and an unusual defect in the male's position during copulation that is rescued by expression in KCs. Because prt is expressed in neurons that lack other known vesicular transporters or neurotransmitters, it may define a previously unknown neurotransmitter system responsible for sexual behavior and a component of olfactory learning. 相似文献
99.
100.
Warming and free-air CO2 enrichment alter demographics in four co-occurring grassland species 总被引:2,自引:2,他引:0
Williams AL Wills KE Janes JK Vander Schoor JK Newton PC Hovenden MJ 《The New phytologist》2007,176(2):365-374
Species differ in their responses to global changes such as rising CO(2) and temperature, meaning that global changes are likely to change the structure of plant communities. Such alterations in community composition must be underlain by changes in the population dynamics of component species. Here, the impact of elevated CO(2) (550 micromol mol(-1)) and warming (+2 degrees C) on the population growth of four plant species important in Australian temperate grasslands is reported. Data collected from the Tasmanian free-air CO(2) enrichment (TasFACE) experiment between 2003 and 2006 were analysed using population matrix models. Population growth of Themeda triandra, a perennial C(4) grass, was largely unaffected by either factor but population growth of Austrodanthonia caespitosa, a perennial C(3) grass, was reduced substantially in elevated CO(2) plots. Warming and elevated CO(2) had antagonistic effects on population growth of two invasive weeds, Hypochaeris radicata and Leontodon taraxacoides, with warming causing population decline. Analysis of life cycle stages showed that seed production, seedling emergence and establishment were important factors in the responses of the species to global changes. These results show that the demographic approach is very useful in understanding the variable responses of plants to global changes and in elucidating the life cycle stages that are most responsive. 相似文献