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1.
Data are presented regarding the establishment of the pH (designated pH*) of a standard buffer solution suitable as a pH reference in 50 mass% glycerol/water mixtures at temperatures ranging from -20 to 25 degrees C. The buffer material selected was the ampholyte Mops [(3-N-morpholino)-propane sulfonic acid], and the reference standard consists of equal molal amounts of Mops and its sodium salt. The assignment of pH* values is based on measurements of the electromotive force (emf) of cells without liquid junction of the type: Pt;H2(g, 1 atm) / Mops, Na Mopsate, NaCl / AgCl;Ag and the pH* was derived from a determination of K2, the equilibrium constant for the dissociation process (Mops) +/- in equilibrium with (Mopsate)- + H+. The standard emf of the silver-silver chloride electrode in 30, 40, and 50 mass% glycerol/water mixtures was determined from emf measurements of the cell at subzero temperatures with HCl solutions replacing the buffer-chloride mixtures. 相似文献
2.
Nitrogen budget of a shortgrass prairie ecosystem 总被引:3,自引:0,他引:3
Summary A N budget is presented for a shortgrass prairie ecosystem. The grassland was ungrazed by domestic herbivores. The quantities of N in various plant, animal, microorganism, and soil components of the ecosystem are estimated for the date when aboveground living biomass was at its maximum for the growing season of 1973. Annual transfers of N between the various compartments were also estimated.Of the total N, 99.5% was in organic forms. The relatively inert heteropolycondensate fraction of the organic matter in the soils contained 88.8% of the N. Living organisms contained 4.2% and dead but recognizable organisms or part thereof contained 6.5% of the total N. Belowground animals contained more than 10 times as much N as abovegroud animals, but combined, animals contained less than 0.1% of the total in the system. Living plant material contained 2.5% of the total N. Seventy-two percent of the living plant N was below ground. Microorganisms contained 1.4% of the total N.Total N uptake by plants from soil solution was 2.9 g·m-2·yr-1. Aerial portions of plants were allocated 1.9 N·m-2·yr-1 although apparently 26% of this amount came from internally recycled sources. The heteropolycondensate fraction of the soil contributed 0.7 g N·m-2·yr-1 to mineral forms, but these components of the system were assumed to be in steady state; thus an equal amount of mineral N was allocated back to the source. Mineralization of N from plant residues was sufficient to account for all of the N taken up by plants from soil solution. Soil animals immobilized about 0.4 g N·m-2·yr-1 while the amount shunted to aboveground animals was trivial. 相似文献
3.
Plasminogen activator and collagenase production by cultured capillary endothelial cells 总被引:33,自引:17,他引:16
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Cultured bovine capillary endothelial (BCE) cells produce low levels of collagenolytic activity and significant amounts of the serine protease plasminogen activator (PA). When grown in the presence of nanomolar quantities of the tumor promoter 12-O-tetradecanoyl phorbol-13-acetate (TPA), BCE cells produced 5-15 times more collagenolytic activity and 2-10 times more PA than untreated cells. The enhanced production of these enzymes was dependent on the dose of TPA used, with maximal response at 10(-7) to 10(-8) M. Phorbol didecanoate (PDD), an analog of TPA which is an active tumor promoter, also increased protease production. 4-O-methyl-TPA and 4α-PDD, two analogs of TPA which are inactive as tumor promoters, had no effect on protease production. Increased PA and collagenase activities were detected within 7.5 and 19 h, respectively, after the addition of TPA. The TPA-stimulated BCE cells synthesized a urokinase-type PA and a typical vertebrate collagenase. BCE cells were compared with bovine aortic endothelial (BAE) cells and bovine embryonic skin (BES) fibroblasts with respect to their production of protease in response to TPA. Under normal growth conditions, low levels of collagenolyic activity were detected in the culture fluids from BCE, BAE, and BES cells. BCE cells produced 5-13 times the basal levels of collagenolytic activity in response to TPA, whereas BAE cells and BES fibroblasts showed a minimal response to TPA. Both BCE and BAE cells exhibited relatively high basal levels of PA, the production of which was stimulated approximately threefold by the addition of TPA. The observation that BCE cells and not BAE cells produced high levels of both PA and collagenase activities in response to TPA demonstrates a significant difference between these two types of endothelial cells and suggests that the enhanced detectable activities are a property unique to bovine capillary and microvessel and endothelial cells. 相似文献
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5.
Tully DC Liu H Alper PB Chatterjee AK Epple R Roberts MJ Williams JA Nguyen KT Woodmansee DH Tumanut C Li J Spraggon G Chang J Tuntland T Harris JL Karanewsky DS 《Bioorganic & medicinal chemistry letters》2006,16(7):1975-1980
A series of N(alpha)-2-benzoxazolyl-alpha-amino acid-(arylaminoethyl)amides were identified as potent, selective, and noncovalent inhibitors of cathepsin S. Structure-activity relationships including strategies for modulating the selectivities among cathepsins S, K, and L, and in vivo pharmacokinetics are discussed. A X-ray structure of compound 3 bound to the active site of cathepsin S is also reported. 相似文献
6.
Tully DC Liu H Chatterjee AK Alper PB Williams JA Roberts MJ Mutnick D Woodmansee DH Hollenbeck T Gordon P Chang J Tuntland T Tumanut C Li J Harris JL Karanewsky DS 《Bioorganic & medicinal chemistry letters》2006,16(19):5107-5111
We report a novel series of noncovalent inhibitors of cathepsin S. The synthesis of the peptidomimetic scaffold is described and structure-activity relationships of P3, P1, and P1' subunits are discussed. Lead optimization to a non-peptidic scaffold has resulted in a new class of potent, highly selective, and orally bioavailable cathepsin S inhibitors. 相似文献
7.
D. S. Schimel W. J. Parton F. J. Adamsen R. G. Woodmansee R. L. Senft M. A. Stillwell 《Biogeochemistry》1986,2(1):39-52
The cycling and volatile loss of N derived from cattle urine at upland and lowland sites within the shortgrass steppe of eastern Colorado was studied, using15N-labelled urea as an N source. Losses of NH
0
3
were determined by direct measurement and by difference. Losses were higher from coarse (27% summer, 12% winter) than from fine textured (0–2%) soils. Immobilization and plant uptake of N accounted for significant amounts of added N. Extrapolating our plot measurements to a typical pasture, using spatially and temporally stratified urine deposition data, losses from upland sites were calculated to be 0.016 g N · m-2 · y-1, while losses from lowland sites were negligible. This resulted in an average loss of 0.011 g N · m-2 · y-1 for a pasture divided 70:30 between uplands and lowlands. The loss of urine N calculated assuming no spatial stratification would be sevenfold higher (0.076 g N · m-2 · y-1). Losses of NH
0
3
from urine, animal biomass removal, and NH2O loss totaled only 0.07 g N · m-2 · y-1 , or about 25% of wet deposition input. We calculated a potential loss of NH
0
3
from senescing vegetation of 0.26 g N · m-2 · y-1, an order of magnitude larger than all other losses combined. 相似文献
8.
Tully DC Liu H Chatterjee AK Alper PB Epple R Williams JA Roberts MJ Woodmansee DH Masick BT Tumanut C Li J Spraggon G Hornsby M Chang J Tuntland T Hollenbeck T Gordon P Harris JL Karanewsky DS 《Bioorganic & medicinal chemistry letters》2006,16(19):5112-5117
The synthesis and structure-activity relationship of a series of arylaminoethyl amide cathepsin S inhibitors are reported. Optimization of P3 and P2 groups to improve overall physicochemical properties resulted in significant improvements in oral bioavailability over early lead compounds. An X-ray structure of compound 37 bound to the active site of cathepsin S is also reported. 相似文献
9.
A common polygenic basis for quinine and PROP avoidance in mice 总被引:3,自引:2,他引:1
Inbred strains of mice (Mus musculus) differ greatly in ability to taste
various bitter compounds. For some compounds, the differences result from
allelic variation at a single locus. However, segregation patterns
incompatible with monogenic inheritance have been found for quinine
avoidance. The Soa bitter sensitivity locus exerts some influence on this
phenotype, but an unknown number of other loci also contribute. Relative
avoidance patterns for quinine sulfate in panels of naive inbred strains
resembled avoidance patterns for 6-n-propyl-2- thiouracil (PROP),
suggesting a common genetic basis. In particular, C57BL/6J mice strongly
avoided both 0.1 mM quinine sulfate and 1 mM PROP in two-bottle preference
tests, whereas C3H/HeJ mice were indifferent to both. Therefore, 12 BXH/Ty
recombinant inbred strains, derived from these strains, were tested with
both solutions to begin identification of the unknown bitter loci. Naive
mice were tested for four consecutive days with each compound (order
counterbalanced). Some BXH/Ty strain means resembled those of the parent
strains, but others were intermediate. This indicated recombination among
loci affecting avoidance, and therefore polygenic inheritance. The strain
means were highly correlated across compounds (r = 0.98), suggesting that
the same polygenes controlled both phenotypes. The BXH/Ty means for both
compounds were then compared with the strain genotypes at 212 chromosome
position markers distributed throughout the genome. Eight markers on five
chromosomes (3, 6, 7, 8 and 9) yielded significant correlations. Six of the
markers were correlated with both phenotypes, again suggesting common
polygenic inheritance. The marker with the highest correlation was Prp,
tightly linked to Soa on chromosome 6. The correlated marker regions likely
contain quantitative trait loci affecting bitter avoidance. The phenotypic
similarity of PROP to quinine, rather than to phenylthiourea, apparently
stemming from a common polygenic basis, indicates a difference between mice
and humans in gustatory organization related to bitters.
相似文献
10.
Carla DB Fernandez Fernanda F Bellentani Glaura SA Fernandes Juliana E Perobelli Ana Paula A Favareto André F Nascimento Antonio C Cicogna Wilma DG Kempinas 《Reproductive biology and endocrinology : RB&E》2011,9(1):32