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81.
Anton C. Schoolwerth Aubrey R. Morrison Yesse Yates Saulo Klahr 《Biochimica et Biophysica Acta (BBA)/General Subjects》1976,444(3)
The metabolic effects of imidazole were tested in rat renal cortex. Imidazole enhanced the activity of renal cortical phosphodiesterase in vitro. Imidazole inhibited glucose production in a dose-dependent fashion from a variety of substrates in the gluconeogenic pathway proximal to the triose phosphates. The stimulation in renal gluconeogenesis resulting from isoproterenol and parathyroid hormone was inhibited by imidazole. These changes correlated with an inhibition of the augmented levels of renal cortical cyclic AMP levels produced by these hormones. These studies indicate that imidazole is an effective activator of phosphodiesterase in intact renal cells and lend further support to the suggestion that the stimulation of renal gluconeogenesis produced by isoproterenol and parathyroid hormone is mediated by a release of cyclic AMP. 相似文献
82.
The thermal dissipation technique is widely used to estimate transpiration of individual trees and forest stands, but there
are conflicting reports regarding its accuracy. We compared the rate of water uptake by stems of six tree species in potometers
with sap flow (F
S) estimates derived from thermal dissipation sensors to evaluate the accuracy of the technique. To include the full range
of xylem anatomies (i.e., diffuse-porous, ring-porous, and tracheid), we used saplings of sweetgum (Liquidambar styraciflua), eastern cottonwood (Populus deltoides), white oak (Quercus alba), American elm (Ulmus americana), shortleaf pine (Pinus echinata), and loblolly pine (Pinus taeda). In almost all instances, estimated F
S deviated substantially from actual F
S, with the discrepancy in cumulative F
S ranging from 9 to 55%. The thermal dissipation technique generally underestimated F
S. There were a number of potential causes of these errors, including species characteristics and probe construction and installation.
Species with the same xylem anatomy generally did not show similar relationships between estimated and actual F
S, and the largest errors were in species with diffuse-porous (Populus deltoides, 34%) and tracheid (Pinus taeda, 55%) xylem anatomies, rather than ring-porous species Quercus alba (9%) and Ulmus americana (15%) as we had predicted. New species-specific α and β parameter values only modestly improved the accuracy of F
S estimates. However, the relationship between the estimated and actual F
S was linear in all cases and a simple calibration based on the slope of this relationship reduced the error to 1–4% in five
of the species, and to 8% in Liquidambar styraciflua. Our calibration approach compensated simultaneously for variation in species characteristics and sensor construction and
use. We conclude that species-specific calibrations can substantially increase the accuracy of the thermal dissipation technique. 相似文献
83.
Chen L Necela BM Su W Yanagisawa M Anastasiadis PZ Fields AP Thompson EA 《The Journal of biological chemistry》2006,281(34):24575-24587
Peroxisome proliferator-activated receptor gamma (PPARgamma) causes epithelial to mesenchymal transformation (EMT) in intestinal epithelial cells, as evidenced by reorganization of the actin cytoskeleton, acquisition of a polarized, mesenchymal cellular morphology, increased cellular motility, and colony scattering. This response is due to activation of Cdc42, resulting in p21-activated kinase-dependent phosphorylation and activation of MEK1 Ser(298) and activation of ERK1/2. Dominant negative MEK1, MEK2, and ERK2 block PPARgamma-induced EMT, whereas constitutively active MEK1 and MEK2 induce a mesenchymal phenotype similar to that evoked by PPARgamma. PPARgamma also stimulates ERK1/2 phosphorylation in the intestinal epithelium in vivo. PPARgamma induces the p110alpha subunit of phosphoinositide 3-kinase (PI3K), and inhibition of PI3K blocks PPARgamma-dependent phosphorylation of MEK1 Ser(298), activation of ERK1/2, and EMT. We conclude that PPARgamma regulates the motility of intestinal epithelial cells through a mitogen-activated protein kinase cascade that involves PI3K, Cdc42, p21-activated kinase, MEK1, and ERK1/2. Regulation of cellular motility through Rho family GTPases has not been previously reported for nuclear receptors, and elucidation of the mechanism that accounts for the role of PPARgamma in regulating motility of intestinal epithelial cells provides fundamental new insight into the function of this receptor during renewal of the intestinal epithelium. 相似文献
84.
It has been proposed that one function of introns is to coordinate expression across/within networks of related genes. This same hypothesis also predicts that intronless genes will not be uniformly distributed among the functional categories of human genes, but will be found most frequently in those categories that have less need to communicate changes in their expression. Statistical analysis demonstrates significant clustering of single exon genes among those with binding or signal transduction/receptor activities and fewer than expected among those with catalytic function. 相似文献
85.
A. D. Aubrey H. J. Cleaves Jeffrey L. Bada 《Origins of life and evolution of the biosphere》2009,39(2):91-108
There is little consensus regarding the plausibility of organic synthesis in submarine hydrothermal systems (SHSs) and its
possible relevance to the origin of life. The primary reason for the persistence of this debate is that most experimental
high temperature and high-pressure organic synthesis studies have neglected important geochemical constraints with respect
to source material composition. We report here the results of experiments exploring the potential for amino acid synthesis
at high temperature from synthetic seawater solutions of varying composition. The synthesis of amino acids was examined as
a function of temperature, heating time, starting material composition and concentration. Using very favorable reactant conditions
(high concentrations of reactive, reduced species), small amounts of a limited set of amino acids are generated at moderate
temperature conditions (∼125–175°C) over short heating times of a few days, but even these products are significantly decomposed
after exposure times of approximately 1 week. The high concentration dependence observed for these synthetic reactions are
demonstrated by the fact that a 10-fold drop in concentration results in orders of magnitude lower yields of amino acids.
There may be other synthetic mechanisms not studied herein that merit investigation, but the results are likely to be similar.
We conclude that although amino acids can be generated from simple likely environmentally available precursors under SHS conditions,
the equilibrium at high temperatures characteristic of SHSs favors net amino acid degradation rather than synthesis, and that
synthesis at lower temperatures may be more favorable. 相似文献
86.
Anton Montsant Andrew E. Allen Sacha Coesel Alessandra De Martino Angela Falciatore Manuela Mangogna Magali Siaut Marc Heijde Kamel Jabbari Uma Maheswari Edda Rayko Assaf Vardi Kirk E. Apt John A. Berges Anthony Chiovitti Aubrey K. Davis Kimberlee Thamatrakoln Masood Z. Hadi Todd W. Lane J. Casey Lippmeier Diego Martinez Micaela S. Parker Gregory J. Pazour Mak A. Saito Dan S. Rokhsar E. Virginia Armbrust Chris Bowler 《Journal of phycology》2007,43(3):585-604
87.
Spinocerebellar ataxia type 8: molecular genetic comparisons and haplotype analysis of 37 families with ataxia 下载免费PDF全文
Ikeda Y Dalton JC Moseley ML Gardner KL Bird TD Ashizawa T Seltzer WK Pandolfo M Milunsky A Potter NT Shoji M Vincent JB Day JW Ranum LP 《American journal of human genetics》2004,75(1):3-16
We reported elsewhere that an untranslated CTG expansion causes the dominantly inherited neurodegenerative disorder spinocerebellar ataxia type 8 (SCA8). SCA8 shows a complex inheritance pattern with extremes of incomplete penetrance, in which often only one or two affected individuals are found in a given family. SCA8 expansions have also been found in control chromosomes, indicating that separate genetic or environmental factors increase disease penetrance among SCA8-expansion-carrying patients with ataxia. We describe the molecular genetic features and disease penetrance of 37 different families with SCA8 ataxia from the United States, Canada, Japan, and Mexico. Haplotype analysis using 17 STR markers spanning an approximately 1-Mb region was performed on the families with ataxia, on a group of expansion carriers in the general population, and on psychiatric patients, to clarify the genetic basis of the reduced penetrance and to investigate whether CTG expansions among different populations share a common ancestral background. Two major ancestrally related haplotypes (A and A') were found among white families with ataxia, normal controls, and patients with major psychosis, indicating a common ancestral origin of both pathogenic and nonpathogenic SCA8 expansions among whites. Two additional and distinct haplotypes were found among a group of Japanese families with ataxia (haplotype B) and a Mexican family with ataxia (haplotype C). Our finding that SCA8 expansions on three independently arising haplotypes are found among patients with ataxia and cosegregate with ataxia when multiple family members are affected further supports the direct role of the CTG expansion in disease pathogenesis. 相似文献
88.
Vijayan KV Huang TC Liu Y Bernardo A Dong JF Goldschmidt-Clermont PJ Alevriadou BR Bray PF 《FEBS letters》2003,540(1-3):41-46
Adhesion of platelets to the exposed extracellular matrix proteins at sites of vascular injury is partly regulated by the local fluid shear stress. Because the Leu33Pro (PlA) polymorphism of integrin β3 confers only a modest increase in adhesion under static conditions, we used CHO and 293 cells expressing the Leu33 or Pro33 isoform of β3 in flow chamber experiments to test whether shear forces would alter the PlA adhesive phenotype. We found that shear force augmented the Pro33-mediated enhanced adhesion to fibrinogen. This Pro33-dependent enhancement was aspirin-sensitive and was also observed on immobilized von Willebrand factor and cryoprecipitate, but not fibronectin. Thus, shear stress enhances the adhesive phenotype of the Pro33 cells to multiple physiologic substrates. 相似文献
89.
90.
Functional genomics tools for the analysis of zebrafish pigment 总被引:3,自引:0,他引:3
Pickart MA Sivasubbu S Nielsen AL Shriram S King RA Ekker SC 《Pigment cell research / sponsored by the European Society for Pigment Cell Research and the International Pigment Cell Society》2004,17(5):461-470
Genetic model organisms are increasingly valuable in the post-genomics era to provide a basis for comparative analysis of the human genome. For higher order processes of vertebrate pigment cell biology and development, the mouse has historically been the model of choice. A complementary organism, the zebrafish (Danio rerio), shares many of the signaling and biological processes of vertebrates, e.g. neural crest development. The zebrafish has a number of characteristics that make it an especially valuable model for the study of pigment cell biology and disease. Large-scale genetic screens have identified a collection of pigmentation mutants that have already made valuable contributions to pigment research. An increasing repertoire of genomic resources such as an expressed sequence tag-based Gene Index (The Institute for Genomic Research) and improving methods of mutagenesis, transgenesis, and gene targeting make zebrafish a particularly attractive model. Morpholino phosphorodiamidate oligonucleotide (MO) 'knockdown' of pigment gene expression provides a non-conventional antisense tool for the analysis of genes involved in pigment cell biology and disease. In addition, an ongoing, reverse-genetic, MO-based screen for the rapid identification of gene function promises to be a valuable complement to other high-throughput microarray and proteomic approaches for understanding pigment cell biology. Novel reagents for zebrafish transgenesis, such as the Sleeping Beauty transposon system, continue to improve the capacity for genetic analysis in this system and ensure that the zebrafish will be a valuable genetic model for understanding a variety of biological processes and human diseases for years to come. 相似文献