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排序方式: 共有283条查询结果,搜索用时 17 毫秒
101.
Y Deng J Zhao D Sakurai KM Kaufman JC Edberg RP Kimberly DL Kamen GS Gilkeson CO Jacob RH Scofield CD Langefeld JA Kelly ME Alarcón-Riquelme BIOLUPUS GENLES Networks JB Harley TJ Vyse BI Freedman PM Gaffney KM Sivils JA James TB Niewold RM Cantor W Chen BH Hahn EE Brown PROFILE BP Tsao 《Arthritis research & therapy》2012,14(Z3):A5
102.
103.
Insulin-like growth factor I receptor signaling is required for exercise-induced cardiac hypertrophy 总被引:1,自引:0,他引:1
Kim J Wende AR Sena S Theobald HA Soto J Sloan C Wayment BE Litwin SE Holzenberger M LeRoith D Abel ED 《Molecular endocrinology (Baltimore, Md.)》2008,22(11):2531-2543
The receptors for IGF-I (IGF-IR) and insulin (IR) have been implicated in physiological cardiac growth, but it is unknown whether IGF-IR or IR signaling are critically required. We generated mice with cardiomyocyte-specific knockout of IGF-IR (CIGF1RKO) and compared them with cardiomyocyte-specific insulin receptor knockout (CIRKO) mice in response to 5 wk exercise swim training. Cardiac development was normal in CIGF1RKO mice, but the hypertrophic response to exercise was prevented. In contrast, despite reduced baseline heart size, the hypertrophic response of CIRKO hearts to exercise was preserved. Exercise increased IGF-IR content in control and CIRKO hearts. Akt phosphorylation increased in exercise-trained control and CIRKO hearts and, surprisingly, in CIGF1RKO hearts as well. In exercise-trained control and CIRKO mice, expression of peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha) and glycogen content were both increased but were unchanged in trained CIGF1RKO mice. Activation of AMP-activated protein kinase (AMPK) and its downstream target eukaryotic elongation factor-2 was increased in exercise-trained CIGF1RKO but not in CIRKO or control hearts. In cultured neonatal rat cardiomyocytes, activation of AMPK with 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR) prevented IGF-I/insulin-induced cardiomyocyte hypertrophy. These studies identify an essential role for IGF-IR in mediating physiological cardiomyocyte hypertrophy. IGF-IR deficiency promotes energetic stress in response to exercise, thereby activating AMPK, which leads to phosphorylation of eukaryotic elongation factor-2. These signaling events antagonize Akt signaling, which although necessary for mediating physiological cardiac hypertrophy, is insufficient to promote cardiac hypertrophy in the absence of myocardial IGF-I signaling. 相似文献
104.
Maize (Zea mays L.) tortilla is the major staple food for the Mexican population. Nine tropical maize genotypes were evaluated. All samples had white grains, a common characteristic in tropical maize, and therefore they were appropriate for nixtamalized flour industry. Grain, flour, masa and tortilla characteristics of each maize genotype were evaluated. Length, width, thickness, weight of 1000 grains and hardness of grain were determined. Moisture content, proteins, fat, ash, mean particle size, water absorption index, enthalpy, and flour temperature were also evaluated. Adhesiveness and cohesiveness were evaluated in masa. Moisture content, protein, capacity to puff up, roll making, tension and cutting strength were determined in tortillas. There were significant differences (p≤0.05) in most of the evaluated characteristics. Grain length values varied between 9.26 and 11.02 mm for populations 23 and 22, respectively. Grain hardness oscillated between 11.17 (population 32) and 14.75 (landrace Mejen). According to the weight of 1000 grains most genotypes had small grains. The minimum and maximum moisture values of flour and tortillas were 8.33-9.99% and 46.20-50.36%, respectively. The texture of tortillas elaborated from population 32 and landrace Mejen had the lowest tension and cutting strength, resulting the best genotypes for making tortilla. 相似文献
105.
Summary We examine the statistical and other considerations which determine the validity and reproducibility of stereospecific hydrogen NMR assignments obtained by the floating prochirality method. In this method, the assignment of a prochiral configuration of hydrogens at selected centers is allowed to float during the structure refinement, and the distribution of prochiral orientations in highly refined structures is subjected to statistical analysis. The underlying statistical basis for this approach is examined and potential limitations of current approaches are identified. As an example, approximately 1300 distance constraints obtained from NOESY spectra of oxidized horse cytochrome c have been used to examine several computational strategies. Repeated calculations were done by several different methods on both the whole molecule (104 residues plus heme) and on a 23-residue fragment containing two helices, a turn, and flanking residues. The results show that, even with NOE constraints alone, one third of the centers may be reproducibly assigned, provided appropriate precautions are taken. These precautions include adjustments for multiple statistical comparisons and characterization of statistical interactions between prochiral centers. The analysis demonstrates that inadequately constrained systems, such as fragments from a larger molecule, may produce misleading results, raising concerns about methods which rely solely on intraresidue and sequential interresidue contraints. A mathematical model describing interactions among prochiral centers is described and validated, and protocols for assignment and statistical validation are presented. 相似文献
106.
Kuzoff RK; Sweere JA; Soltis DE; Soltis PS; Zimmer EA 《Molecular biology and evolution》1998,15(3):251-263
18S ribosomal RNA genes are the most widely used nuclear sequences for
phylogeny reconstruction at higher taxonomic levels in plants. However, due
to a conservative rate of evolution, 18S rDNA alone sometimes provides too
few phylogenetically informative characters to resolve relationships
adequately. Previous studies using partial sequences have suggested the
potential of 26S or large-subunit (LSU) rDNA for phylogeny retrieval at
taxonomic levels comparable to those investigated with 18S rDNA. Here we
explore the patterns of molecular evolution of entire 26S rDNA sequences
and their impact on phylogeny retrieval. We present a protocol for PCR
amplification and sequencing of entire (approximately 3.4 kb) 26S rDNA
sequences as single amplicons, as well as primers that can be used for
amplification and sequencing. These primers proved useful in angiosperms
and Gnetales and likely have broader applicability. With these protocols
and primers, entire 26S rDNA sequences were generated for a diverse array
of 15 seed plants, including basal eudicots, monocots, and higher eudicots,
plus two representatives of Gnetales. Comparisons of sequence dissimilarity
indicate that expansion segments (or divergence domains) evolve 6.4 to 10.2
times as fast as conserved core regions of 26S rDNA sequences in plants.
Additional comparisons indicate that 26S rDNA evolves 1.6 to 2.2 times as
fast as and provides 3.3 times as many phylogenetically informative
characters as 18S rDNA; compared to the chloroplast gene rbcL, 26S rDNA
evolves at 0.44 to 1.0 times its rate and provides 2.0 times as many
phylogenetically informative characters. Expansion segment sequences
analyzed here evolve 1.2 to 3.0 times faster than rbcL, providing 1.5 times
the number of informative characters. Plant expansion segments have a
pattern of evolution distinct from that found in animals, exhibiting less
cryptic sequence simplicity, a lower frequency of insertion and deletion,
and greater phylogenetic potential.
相似文献
107.
Human immunodeficiency virus type 1 membrane fusion mediated by a laboratory-adapted strain and a primary isolate analyzed by resonance energy transfer. 总被引:1,自引:0,他引:1
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V Litwin K A Nagashima A M Ryder C H Chang J M Carver W C Olson M Alizon K W Hasel P J Maddon G P Allaway 《Journal of virology》1996,70(9):6437-6441
Previous studies of human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein-mediated membrane fusion have focused on laboratory-adapted T-lymphotropic strains of the virus. The goal of this study was to characterize membrane fusion mediated by a primary HIV-1 isolate in comparison with a laboratory-adapted strain. To this end, a new fusion assay was developed on the basis of the principle of resonance energy transfer, using HeLa cells stably transfected with gp120/gp41 from the T-lymphotropic isolate HIV-1LA1 or the macrophage-tropic primary isolate HIV-1JR-FL. These cells fused with CD4+ target cell lines with a tropism mirroring that of infection by the two viruses. Of particular note, HeLa cells expressing HIV-1JR-FL gp120/gp41 fused only with PM1 cells, a clonal derivative of HUT 78, and not with other T-cell or macrophage cell lines. These results demonstrate that the envelope glycoproteins of these strains play a major role in mediating viral tropism. Despite significant differences exhibited by HIV-1JR-FL and HIV-1LAI in terms of tropism and sensitivity to neutralization by CD4-based proteins, the present study found that membrane fusion mediated by the envelope glycoproteins of these viruses had remarkably similar properties. In particular, the degree and kinetics of membrane fusion were similar, fusion occurred at neutral pH and was dependent on the presence of divalent cations. Inhibition of HIV-1JR-FL envelope glycoprotein-mediated membrane fusion by soluble CD4 and CD4-IgG2 occurred at concentrations similar to those required to neutralize this virus. Interestingly, higher concentrations of these agents were required to inhibit HIV-1LAI envelope glycoprotein-mediated membrane fusion, in contrast to the greater sensitivity of HIV-1LAI virions to neutralization by soluble CD4 and CD4-IgG2. This finding suggests that the mechanisms of fusion inhibition and neutralization of HIV-1 are distinct. 相似文献
108.
CA Istock JA Bell N Ferguson NL Istock 《Journal of industrial microbiology & biotechnology》1996,17(3-4):137-150
A discussion of the species problem in modern evolutionary biology serves as the point of departure for an exploration of how the basic science aspects of this problem relate to efforts to map bacterial diversity for practical pursuits—for prospecting among the bacteria for useful genes and gene-products. Out of a confusing array of species concepts, the Cohesion Species Concept seems the most appropriate and useful for analyzing bacterial diversity. Techniques of allozyme analysis and DNA fingerprinting can be used to put this concept into practice to map bacterial genetic diversity, though the concept requires minor modification to encompass cases of complete asexuality. Examples from studies of phenetically definedBacillus species provide very partial maps of genetic population structure. A major conclusion is that such maps frequently reveal deep genetic subdivision within the phenetically defined specles; divisions that in some cases are clearly distinct genetic species. Knowledge of such subdivisions is bound to make prospecting within bacterial diversity more effective. Under the general concept of genetic cohesion a hypothetical framework for thinking about the full range of species conditions that might exist among bacteria is developed and the consequences of each such model for species delineation, and species identification are discussed. Modes of bacterial evolution, and a theory of bacterial speciation with and without genetic recombination, are examined. The essay concludes with thoughts about prospects for very extensive mapping of bacterial diversity in the service of future efforts to find useful products. In this context, evolutionary biology becomes the handmaiden of important industrial activities. A few examples of past success in commercializing bacterial gene-products from species ofBacillus and a few other bacteria are reviewed. 相似文献
109.
Vessel diameters and branching angles are measured from a large number of arterial bifurcations in the retina of a normal human subject and in that of a rhesus monkey. The results are compared with each other and with theoretical results on this subject. 相似文献
110.
JW Mills ADC MacKnight JA Jarrell JM Dayer DA Ausiello 《The Journal of cell biology》1981,88(3):637-643
To determine the specificity and efficacy of [(3)H]ouabain binding as a quantitative measure of the Na(+) pump (Na(+), K(+)-ATPase) and as a marker for the localization of pumps involved in transepithelial Na(+)-transport, we analyzed the interaction of [(3)H]ouabain with its receptor in pig kidney epithelial (LLC-PK(1)) cells. When these epithelial cells are depleted of Na(+) and exposed to 2 muM [(3)H]ouabain in a Na(+)-free medium, binding is reduced by 90 percent. When depleted of K(+) and incubated in a K(+)- free medium, the ouabain binding rate is increase compared with that measured at 5 mM. This increase is only demonstable when Na(+) is present. The increased rate could be attributed to the predominance of the Na(+)-stimulated phosphorylated form of the pump, as K(+) is not readily available to stimulate dephosphorylation. However, some binding in the K(+)-free medium is attributable to pump turnover (and therefore, recycling of K(+)), because analysis of K(+)-washout kinetics demonstrated that addition of 2 muM ouabain to K(+)-depleted cells increased the rate of K(+) loss. These results indicate that in intact epithelial cells, unlike isolated membrane preparations, the most favorable condition for supporting ouabain binding occurs when the Na(+), K(+)-ATPase is operating in the Na(+)-pump mode or is phosphorylated in the presence of Na(+). When LLC-PK(1) cells were exposed to ouabain at 4 degrees C, binding was reduced by 97 percent. Upon rewarming, the rate of binding was greater than that obtained on cells kept at a constant 37 degrees C. However, even at this accelerated rate, the time to reach equilibrium was beyond what is required for cells, swollen by exposure to cold, to recover normal volume. Thus, results from studies that have attempted to use ouabain to eliminate the contribution of the conventional Na(+) pump to volume recovery must be reevaluated if the exposure to ouabain was done in the cold or under conditions in which the Na(+) pump is not operating. 相似文献