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991.
Joyce Johnson Diwan Jyoti Srivastava Charlest Moore Teresa Haley 《Journal of bioenergetics and biomembranes》1986,18(2):123-134
The dithiol-reactive reagent phenylarsine oxide causes a pH-dependent stimulation of unidirectional K+ flux into respiring rat liver mitochondria. This stimulation is diminished by subsequent addition of either the dithiol 2,3-dimercaptopropanol or the monothiol 2-mercaptoethanol. In contrast, uncoupling by phenylarsine oxide is reversed by 2,3-dimercaptopropanol but not by 2-mercaptoethanol. The data suggest separate sites of interaction of phenylarsine oxide with mechanisms of K+ entry and ATP synthesis. Stimulatory effects of mersalyl and phenylarsine oxide on K+ influx are not additive. Thus PheASO and mersalyl may affect K+ influx at a common site. Pretreatment of the mitochondria with DCCD, which inhibits K+ influx, fails to alter sensitivity to PheAsO or mersalyl. Thus the DCCD binding site associated with the K+ influx mechanism appears to be separate from and independent of the sulfhydryl group(s) which mediate stimulation of K+ influx by PheAsO and mersalyl.PheAsO, like mersalyl, also increases the rate of unidirectional K+ efflux from respiring mitochondria. The combined presence of PheAsO plus mersalyl causes a greater stimulation of K+ efflux than is observed with either reagent alone.Abbreviations used: BAL, British AntilLewisite or 2,3-dimercaptopropanol; DCCD, dicyclohexylcarbodiimide; DBCT, dibutylchloromethyltin chloride; 2-ME, 2-mercaptoethanol; PheAsO, phenylarsine oxide. 相似文献
992.
Teresa Lama Susan E. Del Valle Nicolas Genest William D. Lubell 《International journal of peptide research and therapeutics》2007,13(1-2):355-366
Pro-Aib hydroxyethylene isosteres (S,R)- and (S,S)-7 were synthesized by cascade addition of 2-methyl-1-propenylmagnesium bromide to Boc-Pro-OMe in the presence of CuCN, followed
by ketone reduction and olefin oxidation. By protecting the amine and hydroxyl groups in an oxazolidinone ring, hydroxyethylene
isosteres 7 were successfully incorporated into Boc-Phe-Pro- ψ -[CH-(OH)-CH2]-Aib-NHBn(α -Me) (S,R)-and (S,S)-11, which were characterized by 1H NMR and IR spectroscopy. Examination of the NOESY spectra and the influence of solvent changes on the chemical shifts of
the amide and carbamate proton signals for (S,R)-and (S,S)-11 indicated that both hydroxyethylene isosteres could adopt compact turn structures. The alcohol appears to act as a hydrogen
donor in a seven-membered ring intramolecular hydrogen bond. In addition, analysis of the respective peptide (S,S)-16, in which the hydroxyl group was masked as a methyl ether, showed that the turn conformation was disrupted, and indicated
the importance of the alcohol as a hydrogen-bond donor for turn stability.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
993.
The effect of temperature on Agrobacterium tumefaciens-mediated gene transfer to plants 总被引:10,自引:0,他引:10
Willy Dillen Janniek De Clercq Jyoti Kapila Mukund Zambre Marc Van Montagu Geert Angenon 《The Plant journal : for cell and molecular biology》1997,12(6):1459-1463
Agrobacterium tumefaciens is generally used to achieve genetic transformation of plants. The temperatures that have been used for infection with Agrobacterium in published transformation protocols differ widely and, to our knowledge, the effect of temperature on the efficiency of T-DNA transfer to plants has not been investigated systematically. Agrobacterium tumefaciens strains harbouring a binary vector with the β-glucuronidase ( uidA ) gene and either a nopaline-, an octopine- or an agropine/ succinamopine-type helper plasmid were tested in two transformation systems at temperatures between 15 and 29°C. One system involved cocultivation of Phaseolus acutifolius callus whereas in the other system Nicotiana tabacum leaves were vacuum-infiltrated. In both situations, irrespective of the type of helper plasmid, the levels of transient uidA expression decreased notably when the temperature was raised above 22°C. Expression was low at 27°C and undetectable at 29°C. We anticipate that the efficiency of many published transformation protocols can be improved by reconsidering the factor of temperature. 相似文献
994.
Lama Alzamil Konstantina Nikolakopoulou Margherita Y. Turco 《Cell death and differentiation》2021,28(1):35
Both the proper functioning of the female reproductive tract (FRT) and normal placental development are essential for women’s health, wellbeing, and pregnancy outcome. The study of the FRT in humans has been challenging due to limitations in the in vitro and in vivo tools available. Recent developments in 3D organoid technology that model the different regions of the FRT include organoids of the ovaries, fallopian tubes, endometrium and cervix, as well as placental trophoblast. These models are opening up new avenues to investigate the normal biology and pathology of the FRT. In this review, we discuss the advances, potential, and limitations of organoid cultures of the human FRT.Subject terms: Cell biology, Physiology, Diseases■. 相似文献
995.
996.
Jyoti K. Singh Brett A. Chromy Michael J. Boyers Glyn Dawson Probal Banerjee 《Journal of neurochemistry》1996,66(6):2361-2372
Abstract: Neuronal migration in brain is followed by differentiation of committed neurons and simultaneous apoptosis of uncommitted preneuronal cells due to a limiting supply of trophic factors and nutrients. We have dissected differentiation and apoptosis by designing a simple in vitro model for this nutrient deprivation using engineered neuronal cell lines stably transfected with a promoterless segment (G-21) of the intronless human serotonin1A receptor (5-HT1A -R) gene. Despite the use of widely different heterologous promoters (cytomegalovirus and Rous sarcoma virus) for the stable expression of G-21, a dramatic increase in expression of the 5-HT1A -R (five- to 15-fold) and its mRNA was always observed during degeneration and apoptosis of nutrient-deprived neuronal cells. Involvement in this induction of a 170-bp 5'-end untranslated sequence (5'-UT) (tail end of the 500-bp natural promoter) of G-21 was confirmed by stable transfection of neuronal cells with an SV-40 promoter-driven construct harboring the 5'-UT and the reporter chloramphenicol acetyltransferase (CAT) cDNA. Presence of the 5'-UT resulted in a threefold increase in CAT expression during nutrient deprivation in randomly chosen clones. The induction was also observed in the endogenous 5-HT1A -R, expressed by embryonic day 16 mouse hippocampal neurons, subsequent to nutrient deprivation and onset of degeneration. A trophic role of the 5-HT1A -R has been suggested in earlier studies. Considering the example of protective heat shock proteins, which are induced during various types of stress, our results suggest that stressed neuronal cells undergoing degeneration and apoptosis synthesize increased levels of 5-HT1A -R as a final attempt to survive. 相似文献
997.
Yingjie Yu Shailender S Kanwar Bhaumik B Patel Jyoti Nautiyal Fazlul H Sarkar Adhip PN Majumdar 《Translational oncology》2009,2(4):321-328
5-Fluorouracil (5-FU) or 5-FU plus oxaliplatin (FOLFOX) remains the backbone of colorectal cancer chemotherapeutics but with limited success. This could partly be due to the enrichment of cancer stem cells (CSCs) that are resistant to conventional chemotherapy. Therefore, validation of a nontoxic agent that can either cause reversal of chemoresistance or promote the killing of CSCs would be highly desirable. The current study examines whether curcumin, the major active ingredient of turmeric, either alone or together with FOLFOX, would be an effective strategy to eliminate colon CSCs. Exposure of colon cancer HCT-116 or HT-29 cells to FOLFOX that inhibited their growth led to the enrichment of CSC phenotype as evidenced by increased proportion of CD133-, CD44-, and/or CD166-positive cells and epidermal growth factor receptor (EGFR) levels. Treatment of FOLFOX-surviving colon cancer cells with either curcumin alone or together with FOLFOX resulted in a marked reduction in CSCs, as evidenced by the decreased expression of CD44 and CD166 as well as EGFR and by their ability to form anchorage-dependent colonies. They also caused disintegration of colonospheres. Increased expression of EGFR in FOLFOX-surviving cells could be attributed to hypomethylation of the EGFR promoter, whereas an opposite phenomenon was observed when the FOLFOX-surviving cells were treated with curcumin and/or FOLFOX. These changes were accompanied by parallel alterations in the levels of DNA methyltransferase 1. In conclusion, our data suggest that curcumin by itself or together with the conventional chemotherapeutic could be an effective treatment strategy for preventing the emergence of chemoresistant colon cancer cells by reducing/eliminating CSCs. 相似文献
998.
The poliovirus nonstructural protein-encoding genes have been cloned and expressed in Escherichia coli using the inducible system described by Studier and Moffat [J. Mol. Biol. 189 (1986) 113-130] and Studier [J. Mol. Biol. 219 (1991) 37-44]. The two genes encoding the poliovirus proteases, 2Apro and 3Cpro, were cloned together with their flanking regions in order to test the ability of the polyprotein precursors synthesized to cause proteolytic cleavage and generate mature forms. Both proteases were synthesized and showed activity upon induction in this system. Previously, it had not been possible to produce the three poliovirus nonstructural proteins, 2B, 2C and 3A, and some of their precursors, 2C3AB, 2C3A and 3AB, at high levels in E. coli cells. We report the cloning of their genes using PCR techniques and their efficient expression from pET vectors upon induction with IPTG (isopropyl-beta-D-thiogalactopyranoside). Moreover, some of these proteins, e.g., 3AB, 3A and 2B, are quite toxic for E. coli cells and lysed them upon production. Our results demonstrate the usefulness of this inducible system using the pET vectors to express these toxic poliovirus proteins. 相似文献
999.
Valeria Calandrelli Agata Gambacorta Ida Romano Vito Carratore Licia Lama 《World journal of microbiology & biotechnology》2008,24(10):2269-2275
A novel thermo-alkali-stable catalase–peroxidase from Oceanobacillus oncorhynchi subsp. incaldaniensis subsp. nov., strain 20AG, was purified and characterized. The protein purified from the cells resulted in 110-fold purification
with a specific activity of 35,000 U/mg. The enzyme consisted of four identical subunits of 72 kDa as determined by SDS-PAGE
and the total molecular mass measured by gel filtration was 280 kDa. The heme content was determined to be 1 heme per homodimer.
The enzyme showed a Soret peak at 406 nm in the oxidized form and was easily reduced by dithionite. The enzyme showed an appreciable
peroxidase activity in addition to high catalase activity. The behaviour of this heme-enzyme was typical of the class of prokaryotic
catalase–peroxidases, which are sensitive to cyanide and insensitive to the eukaryotic catalase inhibitor 3-amino-1,2,4-triazole.
The enzyme was active over a temperature range from 30 to 60°C and a pH range from 5 to 10, with an optimum pH about 9.0 and
an optimum temperature of 40°C. The enzyme was stable in the pH range of 5.0 to 10.0 after 1 h of treatment at 40°C. The enzyme
was stable for 24 h at 40°C with a half-life of 4 h 60°C. The enzyme had a K
m of 24 mM for hydrogen peroxide. The amino terminal amino acid sequence of the catalase–peroxidase from strain 20AG was SEKRKMTTAFGA
and it showed no homology with other catalases. 相似文献
1000.