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排序方式: 共有108条查询结果,搜索用时 31 毫秒
1.
R W Moni P G Parsons R J Quinn R J Willis 《Biochemical and biophysical research communications》1992,182(1):115-120
The marine natural product, halistanol trisulfate, has a relatively low critical micelle concentration of 0.001% m/v (14.5 microM) and strong hemolytic potency with an EC50 of 0.00046% m/v (6.67 microM). As expected of a detergent, it inhibits the growth of gram-positive but not gram-negative bacteria. The hemolytic activity of halistanol trisulfate and other detergents has been shown to correlate with critical micelle concentration. This correlation may have important implications in the mechanism of membranolytic bioactivity. 相似文献
2.
A highly conserved nuclear gene for low-level phylogenetics: elongation factor-1 alpha recovers morphology-based tree for heliothine moths 总被引:8,自引:2,他引:6
Cho S; Mitchell A; Regier JC; Mitter C; Poole RW; Friedlander TP; Zhao S 《Molecular biology and evolution》1995,12(4):650-656
Molecular systematists need increased access to nuclear genes. Highly
conserved, low copy number protein-encoding nuclear genes have attractive
features for phylogenetic inference but have heretofore been applied mostly
to very ancient divergences. By virtue of their synonymous substitutions,
such genes should contain a wealth of information about lower-level
taxonomic relationships as well, with the advantage that amino acid
conservatism makes both alignment and primer definition straightforward. We
tested this postulate for the elongation factor-1 alpha (EF-1 alpha) gene
in the noctuid moth subfamily Heliothinae, which has probably diversified
since the middle Tertiary. We sequenced 1,240 bp in 18 taxa representing
heliothine groupings strongly supported by previous morphological and
allozyme studies. The single most parsimonious gene tree and the
neighbor-joining tree for all nucleotides show almost complete concordance
with the morphological tree. Homoplasy and pairwise divergence levels are
low, transition/transversion ratios are high, and phylogenetic information
is spread evenly across gene regions. The EF-1 alpha gene and presumably
other highly conserved genes hold much promise for phylogenetics of
Tertiary age eukaryote groups.
相似文献
3.
Cultured chick embryo fibroblasts derived from skin and skeletal muscle exhibit hyaluronidase activity both associated with the cell layer and secreted into the medium. Although both forms of the enzyme have a number of similar characteristics (R.W. Orkin and B.P. Toole, 1980, J. Biol. CHem. 255), they differ in thermal stability at neutral pH and in behavior on ion-exchange chromatography. Both forms of the enzyme are equally stable at acidic pH for long intervals, but the cell-associated hyaluronidase is significantly less stable than the secreted froms at neutral pH and at temperatures more than or equal to 30 degrees C. Neither the presence of proteases nor inhibitors of hyaluronidase appear to be involved in the cell-asspcoated enzyme. Chromatography of the two forms of hyaluronidase on carboxymethyl cellulose reveals that most (60-90 percent) of the secreted form of the enzyme elutes at a lower ionic strength than the cell- associated enzyme. Treatment of the secreted form of hyaluronidase with neuraminidase shifts its elution profile on carboxymethyl cellulose toward that of the cell-associated form, and also decreases its thermal stability at neutral pH. In contrast, treatment of the secreted form of hyaluronidase with alkaline phosphatase has no detectable effect. These data suggest that the secreted hyaluronidase differs from the cellular form in possessing additional sialic acid residues which endow the former with increased stability in the extracellular milieu. 相似文献
4.
A PBX1 transcriptional network controls dopaminergic neuron development and is impaired in Parkinson's disease 下载免费PDF全文
J Carlos Villaescusa Bingsi Li Enrique M Toledo Pia Rivetti di Val Cervo Shanzheng Yang Simon RW Stott Karol Kaiser Saiful Islam Daniel Gyllborg Rocio Laguna‐Goya Michael Landreh Peter Lönnerberg Anna Falk Tomas Bergman Roger A Barker Sten Linnarsson Licia Selleri Ernest Arenas 《The EMBO journal》2016,35(18):1963-1978
5.
Responding to the concern from our faculty that undergraduate students do not have robust laboratory skills, we designed and implemented a strategy to individually teach and assess the manipulative skills of students in first-year laboratories. Five core laboratory skills were selected for the course entitled Human Biology, a large, first-year class of students, most of whom were enrolled in Bachelor of Pharmacy and Human Movement Studies. Here, we report details for the 365 students enrolled primarily in Pharmacy and Human Movement Studies bachelor degree programs in semester 1 of 2006. We designed a specific strategy to assess five core laboratory skills: 1) accurate and precise use of a micropipette, 2) calculation of dilutions and preparation of diluted samples of saline, 3) accurate representation of data using a graph, 4) use of a light microscope, and 5) acquisition of digital data by measuring the latent period for the Achilles reflex. Graduate tutors were trained to teach and assess each student on each skill. The development of competency was tracked for all students across all five skills. Most students demonstrated proficiency on their first attempt. The development of proficiency across the core skills depended on both the skill and degree program. In semester 2 of 2006, 854 students mostly enrolled in the Bachelor of Science degree program and were similarly taught and assessed on the same five core skills. This approach was an effective teaching and assessment strategy that, when applied beyond first year, should increase the level of laboratory skills across undergraduate programs in physiology. 相似文献
6.
Regioselective synthesis of novel steroidal anti-inflammatory ante drug analogues, viz., [16alpha,17alpha-d]-isoxazolines 1(a-h) and 2(a-h) prepared in a single step in good yield by the reaction of 16-dehydropregnenolone acetate (16-DPA) 1 or related 21-chloro-20-oxopregnane 2 with various aldoximes (a-h) in presence of chloramine-T in refluxing ethanol. 相似文献
7.
8.
Interactions of multiple signaling pathways in neuropeptide Y-mediated bimodal vascular smooth muscle cell growth 总被引:2,自引:0,他引:2
Pons J Kitlinska J Jacques D Perreault C Nader M Everhart L Zhang Y Zukowska Z 《Canadian journal of physiology and pharmacology》2008,86(7):438-448
Neuropeptide Y (NPY), a sympathetic cotransmitter, acts via G protein-coupled receptors to stimulate constriction and vascular smooth muscle cell (VSMC) proliferation through interactions with its Y1 receptors. However, VSMC proliferation appears bimodal, with high- and low-affinity peaks differentially blocked by antagonists of both Y1 and Y5 receptors. Here, we sought to determine the signaling mechanisms of NPY-mediated bimodal mitogenesis. In rat aortic VSMCs, NPY's mitogenic effect at all concentrations was blocked by pertussis toxin and was associated with decreased forskolin-stimulated cAMP levels. NPY also increased intracellular calcium levels; in contrast to mitogenesis, this effect was dose dependent. The rise in intracellular Ca2+ depended on extracellular Ca2+ and was mediated via activation of Y1 receptors, but not Y5 receptors. Despite differences in calcium, the signaling pathways activated at low and high NPY concentrations were similar. The mitogenic effect of the peptide at all doses was completely blocked by inhibitors of calcium/calmodulin-dependent kinase II (CaMKII), protein kinase C (PKC), and mitogen-activated protein kinase kinase, MEK1/2. Thus, in VSMCs, NPY-mediated mitogenesis signals primarily via Y1 receptors activating 2 Ca2+-dependent, growth-promoting pathways -- PKC and CaMKII. At the high-affinity peak, these 2 pathways are amplified by Y5 receptor-mediated, calcium-independent inhibition of the adenylyl cyclase - protein kinase A (PKA) pathway. All 3 mechanisms converge to the extracellular signal-regulated kinases (ERK1/2) signaling cascade and lead to VSMC proliferation. 相似文献
9.
RW Horobin 《Biotechnic & histochemistry》2002,77(1):3-13
New staining techniques continue to be introduced, and older ones continue to be used and improved. Several factors control specificity, selectivity and visibility of the end product in any procedure using dyes, fluorochromes, inorganic reagents or histochemical reactions applied to sections or similar preparations. Local concentration of the tissue target often determines the intensity of the observed color, as does the fine structure within the object being stained, which may facilitate or impede diffusion of dyes and other reagents. Several contributions to affinity control the specificity of staining. These include electrical forces, which result in accumulation of dye ions in regions of oppositely charged tissue polyions. Weaker short-range attractions (hydrogen bonding, van der Waals forces or hydrophobic bonding, depending on the solvent) hold dyes ions and histochemical end products in contact with their macromolecular substrates. Nonionic forces can also increase visibility of stained sites by causing aggregation of dye molecules. Covalent bonds between dye and tissue result in the strongest binding, such as in methods using Schiff's reagent and possibly also some mordant dyes. The rate at which a reagent gains access to or is removed from targets in a section or other specimen affect what is stained, especially when more then one dye is used, together or sequentially. Rate-controlled staining is greatly influenced by the presence and type of embedding medium, such as a resin, that infiltrates the tissue. The rates of chemical reactions are major determinants of outcome in many histochemical techniques. Selective staining of different organelles within living cells is accomplished mainly with fluorochromes and is controlled by mechanisms different from those that apply to fixed tissues. Quantitative structure-activity relations (QSAR) of such reagents can be derived from such molecular properties as hydrophilic-hydrophobic balance, extent of conjugated bond systems, acid-base properties and ionic charge. The QSAR correlates with staining of endoplasmic reticulum, lysosomes, mitochondria, DNA, or the plasma membranes of living cells. 相似文献
10.
By incorporating annotation information into the analysis of next-generation sequencing DNA methylation data, we provide an improvement in performance over current testing procedures. Methylation analysis using genome information (MAGI) is applicable for both unreplicated and replicated data, and provides an effective analysis for studies with low sequencing depth. When compared with current tests, the annotation-informed tests provide an increase in statistical power and offer a significance-based interpretation of differential methylation. 相似文献