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31.
Tristan J. Iseli Nigel Turner Xiao-Yi Zeng Gregory J. Cooney Edward W. Kraegen Sheng Yao Yang Ye David E. James Ji-Ming Ye 《PloS one》2013,8(4)
We recently showed that bitter melon-derived triterpenoids (BMTs) activate AMPK and increase GLUT4 translocation to the plasma membrane in vitro, and improve glucose disposal in insulin resistant models in vivo. Here we interrogated the mechanism by which these novel compounds activate AMPK, a leading anti-diabetic drug target. BMTs did not activate AMPK directly in an allosteric manner as AMP or the Abbott compound (A-769662) does, nor did they activate AMPK by inhibiting cellular respiration like many commonly used anti-diabetic medications. BMTs increased AMPK activity in both L6 myotubes and LKB1-deficient HeLa cells by 20–35%. Incubation with the CaMKKβ inhibitor, STO-609, completely attenuated this effect suggesting a key role for CaMKKβ in this activation. Incubation of L6 myotubes with the calcium chelator EGTA-AM did not alter this activation suggesting that the BMT-dependent activation was Ca2+-independent. We therefore propose that CaMKKβ is a key upstream kinase for BMT-induced activation of AMPK. 相似文献
32.
33.
Carbonmonoxyhemoglobin prepared from protein isolated from rabbits maintained on a diet supplemented with 4-fluorophenylalanine (Phe (4F)) has been studied by fluorine NMR spectroscopy. Substitution of Phe(4F) appears to take place randomly at the sixteen nonequivalent phenylalanine positions of the globins; examination of hybrid hemoglobins in which only one type of globin chain contained the fluorinated amino acid, as well as changes in the spectrum upon exposure to oxygen, aided in the assignment of fluorine resonances from the alpha- or beta-globin chains. The effects of modification of Cys-beta-93 with a spin label and variation of pH and sample temperature on the spectrum were also examined. These data in association with theoretical estimates of aromatic ring current and van der Waals effects on chemical shifts were used to support tentative assignments of several signals observed to specific amino acid residues. Evidence suggesting the presence of two conformational forms of the protein, possibly due to disorder of the heme groups, is described. 相似文献
34.
Cross-comparisons of nectar production data are complicated because different workers use bags made of various materials to exclude animal visitors. Using clonal populations of Asclepias syriaca and A. exaltata in northern Virginia, we carefully measured the effects of four bagging treatments (bridal veil, pellon, paper, plastic) on microenvironment (temperature, relative humidity) and nectar production (volume, concentration, sucrose amount) over the course of a day. In general, bridal veil bags changed the microenvironment least relative to unbagged controls. Plastic bags resulted in higher temperatures and constantly higher relative humidities. Temperature and relative humidity were also elevated, though less dramatically, in paper and pellon bags. Under more humid conditions, flowers contained larger volumes of more dilute nectar. Therefore, researchers who wish to obtain nectar production data that reflect natural field conditions should use bridal veil, or a material with similar properties, to bag inflorescences. We also performed a watering experiment, involving the addition of the equivalent of a 10-cm rain to the A. syriaca plot. After watering, nectar volumes and sucrose amounts were increased approximately twofold. 相似文献
35.
36.
Photocopying was found to be a rapid method of making a permanent record of a root sample. The method used produced a copy
with white roots against a black background.
Manual estimates of root length were made from photocopies using a light box. The number of intersections visible when laid
over a copy of a white on black regular square grid was counted. Automated estimates of root length were made by scanning
a photocopy with a bar code reader in place of a pen in a computer-driven graph plotter. Roots >0.2 mm diameter were resolved
with precision and speed. 相似文献
37.
The potential for radioprotection of growing cartilage by the thiophosphate WR2721 was evaluated in weanling rats using single fractions of irradiation. Protection of acute skin toxicity was monitored simultaneously. Single doses of 600, 1200, 1800, or 2400 cGy were administered to the left tibia of CrL:CD(SD)BR female rats in groups of 12. Identically treated groups were injected with 310 mg/kg WR2721 (2/3 the determined LD50/30) in a concentration of 26 mg/ml intraperitoneally 15 min prior to irradiation. Rats untreated or given WR2721 without radiation served as control groups. Radiographs of the irradiated and unirradiated tibiae for each animal were obtained weekly to the date of sacrifice at 80 days following the initial treatment. Skin toxicity was assessed weekly starting on the second week using Moulder's scale (J.E. Moulder, J.J. Fischer, and A. Casey, Radiology 115, 465-470 (1975]. No significant difference in bone growth as measured by tibial lengths for the WR2721-treated or untreated animals was observed. Skin toxicity including moist desquamation occurred in irradiated limbs and was substantially less in rats treated with WR2721. As opposed to previous work with cysteamine, WR2721 as administered had no significant radioprotective effect on tibial growth in weanling rats but substantially reduced the accompanying skin toxicity. 相似文献
38.
Hadar Kless Yaron Sitrit Ilan Chet Amos B. Oppenheim 《Molecular & general genetics : MGG》1989,217(2-3):471-473
Summary A λ phage DNA library ofSerratia marcescens was constructed and a clone carrying the gene coding for chitobiase (E.C.3.2.1.29) was isolated and characterized. Deletion
analysis limited the cloned region to 4.5 kb that is capable of efficient expression of chitobiase.Escherichia coli cells harboring a plasmid carrying the cloned gene express chitobiase constitutively. The molecular weight of the protein
is about 95000 daltons. In exponentially growingE. coli cells the chitobiase enzyme was found to be secreted into the periplasm. 相似文献
39.
Timothy J. Strabala Sebastian Y. Bednarek Gregory Bertoni Richard M. Amasino 《Molecular & general genetics : MGG》1989,216(2-3):388-394
Summary A 1.9 kb clone of the T-DNA region of the Agrobacterium tumefaciens Ti plasmid Bo542 which exhibited homology to the isopentenyl transferase (ipt) locus of pTiA6 was identified by low stringency DNA hybridization. Introduction of this segment of pTiBo542 DNA into cells of Nicotiana tabacum or N. glauca caused tumor formation in vivo, and allowed hormone independent growth in vitro. Furthermore, this DNA segment complemented ipt mutant strains of A. tumefaciens, restoring their ability to cause tumors on Kalanchöe leaves and tomato stems. The complete DNA sequence of this segment has been determined, revealing an open reading frame homologous to other known Agrobacterium ipt genes. 相似文献
40.
Biotransformation of mercury by bacteria isolated from a river collecting cinnabar mine waters 总被引:1,自引:0,他引:1
One hundred six strains of aerobic bacteria were isolated from the Fiora River which drains an area of cinnabar deposits in southern Tuscany, Italy. Thirty-seven of the strains grew on an agar medium containing 10g/ml Hg (as HgCl2) with all of these strains producing elemental mercury. Seven of the 37 strains also degraded methylmercury. None of 106 sensitive and resistant strains produced detectable monomethylmercury although 15 strains produced a benzene-soluble mercury species. Two strains of alkylmercury (methyl-, ethyl- and phenylmercury) degrading bacteria were tested for the ability to degrade several other analogous organometals and organic compounds, but no activity was detected toward these compounds. Mercury methylation is not a mechanism of Hg resistance in aerobic bacteria from this environment. Growth of bacteria on the agar medium containing 10g/ml HgCl2 was diagnostic for Hg detoxification based on reduction. 相似文献