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121.
A second canon. Functions and mechanisms of beta-catenin-independent Wnt signaling 总被引:12,自引:0,他引:12
More is becoming known about so-called noncanonical Wnt pathways that signal independently of beta-catenin. Here we review recent developments in both the functions and mechanisms of noncanonical Wnt signaling. We also discuss some unresolved and vexing questions. How many noncanonical Wnt pathways are there? How extensive are the parallels between Drosophila planar polarization and vertebrate convergence and extension? Last, we will outline some challenges and difficulties we foresee for this exciting but still very young field. 相似文献
122.
123.
We studied the effects of two structurally unrelated inhibitors of the fatty acid cyclooxygenase and of alpha and beta adrenergic blockade on the elevated plasma levels of 13,14-dihydro-15-keto-prostaglandin (PG)E2, 6-keto-PGF1α and thromboxane(TX)B2, the stable derivatives of PGE2, PGI2 (prostacyclin) and TXA2, respectively, in rats with streptozotocin-induced diabetic ketoacidosis (DKA). Meclofenamic acid and indomethacin each produced a significant decrease in the elevated plasma levels of 13,14-dihydro-15-keto-PGE2, 6-keto-PGF1α and TXB2. Phentolamine significantly reduced the plasma level of TXB2 but had no effect on the elevated circulating levels of glucose, free fatty acids, total ketones, 13,14,-dihydro-15-keto-PGE2 or 6-keto-PGF1α. Propranolol significantly reduced the elevated circulating levels of glucose, free fatty acids and total ketones but had no effect on the levels of the three prostaglandin derivatives. The ability of meclofenamic acid and indomethacin to reduce the plasma levels of 13,14-dihydro-15-keto-PGE2, 6-keto-PGF1α and TXB2 confirms that the plasma levels of these three derivatives are elevated in rats with DKA. Since abnormalities in the production of PGI2 and perhaps other cyclooxygenase derivatives may contribute to the pathogenesis of certain important hemodynamic and gastrointestinal features of DKA, cyclooxygenase inhibitors may play a role in the management of selected patients with this disorder. Alpha adrenergic activity is essential for the maintenance of the elevated plasma TXB2 level in rats with DKA. The fall in the plasma TXB2 level during alpha adrenergic blockade appears to reflect inhibition of platelet aggregation and platelet TXA2 production, but other sources of the elevated plasma TXB2 level in DKA are not excluded. Beta adrenergic activity contributes to the maintenance of elevated circulating levels of glucose, free fatty acids and total ketones in experimental DKA but not to the elevated plasma levels of the prostaglandin derivatives. 相似文献
124.
W J Strittmatter F Hirata J Axelrod 《Biochemical and biophysical research communications》1979,88(1):147-153
Ca2+-ATPase activity in human erythrocytes is increased by the enzymatic methylation of membrane phospholipids. Erythrocyte membranes incubated in the presence of the methyl donor, S-adenosyl-L-methionine, demonstrate increased Ca2+ stimulated ATP hydrolysis, increased [45Ca2+] efflux from erythrocyte ghosts and synthesis of phosphatidyl-N-monomethylethanolamine. The increase in Ca2+-ATPase activity is due to an increase in Vmax, and not due to changes in affinity for ATP or Ca2+. The concentration of S-adenosyl-L-methionine needed to stimulate Ca2+-ATPase closely matches that needed for the methylation of phosphatidylethanolamine. Both the stimulation of Ca2+-ATPase and the methylation of phospholipids are inhibited by the methyltransferase inhibitor, S-adenosyl-L-homocysteine. Membrane fluidity is increased by phospholipid methylation, which may be the mechanism for Ca2+-ATPase stimulation. 相似文献
125.
The in vitro life span of murine spleen lymphocytes stimulated by endotoxin (LPS) was determined. Lymphocytes synthesizing DNA spontaneously in culture and those stimulated to DNA synthesis early (24 hr) and later (48 hr) in culture by LPS had half-lives of approximately 24 hr. The continuing presence of LPS in culture did not prolong cell longevity nor did free LPS have to be present to allow successive rounds of DNA synthesis in committed cells. Once activated to DNA synthesis, blast cells and lymphoblast-like cells did not revert to small lymphocytes. 相似文献
126.
There is a difference in the response of DNA from mycelial extracts of Aspergillus nidulans to hot acid hydrolysis depending upon the state of sporulation competence. The DNA in incompetent culture mycelia is not hydrolyzable while the DNA in competent culture is hydrolyzable. The inhibition of DNA hydrolysis is due to the presence of iron. Although the concentration of iron decreases in mycelia during growth, there is sufficient iron present in competent mycelia to inhibit DNA hydrolysis. The change in DNA hydrolyzability may be the result of a change in intracellular iron distribution, or a change in an iron binding component. We suggest that these changes are related to the altered capacity for gene expression which occurs at the time of acquisition of sporulation competence. 相似文献
127.
V D Axelrod R M Vartikyan V A Aivazashvili R S Beabealashvili 《Nucleic acids research》1978,5(10):3549-3563
Termination of RNA synthesis with 3'-O-Methylnucleoside 5'-triphosphates have been studied using E. coli RNA polymerase holoenzyme and poly [d(A-T)] as well as unfractionated T7 D delta III DNA as templates. It was shown that the termination can be used for DNA sequencing. A sequence of a part of RNA synthesized from AI promoter of the DNA have been determined. Syntheses of four 3'-O-Methylnucleoside 5'-triphosphates are described. 相似文献
128.
Abstract— An assay for 3,4-dihydroxyphenylacetic acid (DOPAC) capable of detecting as little as 1 pmole of DOPAC is described. The basis of the assay is the O -methylation of DOPAC utilizing S -[methyl-3 H]adenosyl-l-methionine and a partially purified catechol- O -methyl transferase to form [methyl-3 H]homovanillic acid. The [methyl-3 H]homovanillic acid is purified with ion exchange resin and either solvent partitions or TLC. Utilizing this assay, the effect of either chlorpromazine or reserpine upon the content of DOPAC both in the caudate nucleus and in the substantia nigra was determined. Both of these drugs increase the level of DOPAC in the caudate nucleus but have minimal effects upon the level of DOPAC in the substantia nigra. 相似文献
129.
A rapid and sensitive radioenzymatic assay for measuring catechol estrogens in tissue has been developed. This assay is based on converting the relatively labile catechol estrogens to stable O-methylated derivatives by the enzyme catechol-O-methyl-transferase. Using a radioactive methyl donor of high specific activity (3H-S-adenosylmethionine) and solvent extraction with non-polar solvents a sensitivity of 25 pg can be achieved. The specificity of this assay was confirmed by thin layer chromatography and mass spectral analysis of the reaction products. Catechol estrogens in rat liver are significantly decreased after ovariectomy and markedly increased by treatment with estrogen. 相似文献
130.
C Gagnon O H Viveros E J Diliberto J Axelrod 《The Journal of biological chemistry》1978,253(11):3778-3781
Carboxyl groups of membrane and soluble proteins from bovine adrenal medulla chromaffin granules were enzymatically methylated. The methylated peptides were resolved using gel electrophoresis under acidic conditions in the presence of N-cetylpyridinium chloride. There was a selective methylation of two groups of membrane peptides which did not correspond to any of the chromaffin granule soluble proteins. Dopamine beta-hydroxylase, an acidic protein accounting for up to 25% of the membrane proteins, was a poor substrate for protein carboxylmethylase. The methyl esters of membrane proteins were more labile than those of the chromaffin granule soluble proteins. At all pH values tested, membrane protein-methyl esters were hydrolyzed three times more rapidly than the soluble protein-methyl esters. 相似文献