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排序方式: 共有107条查询结果,搜索用时 31 毫秒
1.
Inactivation of the nitrate-reducing system in whole cells of Chlorella vulgaris Bejerinck by darkening, nitrogen starvation, ammonium, or cycloheximide brings cells into a state with a high yield of the millisecond-delayed fluorescence of chlorophyll. Activation of this system by illumination, by adding glucose to dark-adapted cells or nitrate to nitrogen-starved cells brings the cells into a low-yield state. The transitions between the lowand high-yield state induced by alternating light and dark periods are suppressed by tungstate and restored by subsequent molybdate addition. The drop in the delayed-fluorescence yield upon activation of the nitrate-reducing system is associated with the decrease of the amplitude of the electrochemical proton gradient across the thylakoid membrane of the chloroplast, as evidenced by the kinetics of the light-induced adsorption changes at 520 nm. The decrease of the proton gradient may be caused by the electron flow diverting from the cyclic path in photosystem I as a result of the activation of the electron transfer from ferredoxin to nitrite.Abbreviation DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea 相似文献
2.
Natalia Trayanova 《Mathematical biosciences》1994,120(2)
An approximate, computationally tractable solution is proposed for the potentials in the bidomain model with periodic intracellular junctions (the periodic bidomain model). This new approach is based on the one-dimensional rigorous spectral method described previously by Trayanova and Pilkington (IEEE Trans. Biomed. Eng., May 1993). The total solution to the one-dimensional periodic bidomain problem is decomposed in the spectral domain into solutions to (1) the single-fiber classical bidomain problem in which the intracellular conductivity value incorporates the average contribution from cytoplasm and junction and (2) the “junctional” potential problem due to the presence of junctions at discrete locations alone. Solving for the junctional term rigorously requires most of the numerical effort in the solution for the periodic bidomain potentials. Here the junctional potential is found approximately with little numerical effort. A comparison between the rigorous and the approximate solutions serves as a justification for the proposed approximate solution procedure. The procedure outlined in this paper is applicable to higher spatial dimensions where both tissue anisotropy and junctional inhomogeneities play a role in establishing the transmembrane potential distribution. 相似文献
3.
Antoaneta Trendafilova Victoria Ivanova Miroslav Rangelov Milka Todorova Gulmira Ozek Suleyman Yur Temel Ozek Ina Aneva Ralitza Veleva Veselina Moskova‐Doumanova Jordan Doumanov Tanya Topouzova‐Hristova 《化学与生物多样性》2020,17(4)
Chlorogenic (5‐CQA), 1,5‐, 3,5‐, 4,5‐ and 3,4‐dicaffeoylquinic (DCQA) acids were identified and quantified in the methanol extracts of Inula oculus‐christi L., I. bifrons L., I. aschersoniana Janka var. aschersoniana, I. ensifolia L., I. conyza (Griess .) DC. and I. germanica L. by HPLC analysis. The amount of 5‐CQA varied from 5.48 to 28.44 mg/g DE and the highest content was detected in I. ensifolia. 1,5‐DCQA (4.05–55.25 mg/g DE) was the most abundant dicaffeoyl ester of quinic acid followed by 3,5‐DCQA, 4,5‐DCQA and 3,4‐DCQA. The extract of I. ensifolia showed the highest total phenolic content (119.92±0.95 mg GAE/g DE) and exhibited the strongest DPPH radical scavenging activity (69.41±0.55 %). I. bifrons extract was found to be the most active sample against ABTS.+ (TEAC 0.257±0.012 mg/mL) and the best tyrosinase inhibitor. The studied extracts demonstrated a low inhibitory effect towards acetylcholinesterase and possessed low cytotoxicity in concentration range from 10 to 300 μg/mL toward non‐cancer (MDCK II) and cancer (A 549) cells. 相似文献
4.
Antoaneta B. Trendafilova Milka N. Todorova Ljuba N. Evstatieva Daniela V. Antonova 《化学与生物多样性》2013,10(3):484-492
The essential‐oil composition of six native populations of Sideritis scardica from Bulgaria was studied by GC‐FID and GC/MS analyses. Altogether, 37 components, representing 73.1 to 79.2% of the total oil content were identified. Among them, α‐pinene (4.4–25.1%), β‐pinene (2.8–18.0%), oct‐1‐en‐3‐ol (2.3–8.0%), phenylacetaldehyde (0.5–9.5%), β‐bisabolene (1.3–11.0%), benzyl benzoate (1.1–14.3%), and m‐camphorene ( 1 ; 0.3–12.4%) were the main compounds. All samples were characterized by low contents of oxygenated mono‐ and sesquiterpenes (≤1.6 and 2.3%, resp.). Principal component analysis (PCA) and cluster analysis (CA) showed a significant variability in the chemical composition of the studied samples as well as a correlation between the oil profiles and the ecological conditions of the natural habitats of S. scardica. 相似文献
5.
Antoaneta B. M. Kroumova Dipak K. Sahoo Sumita Raha Michael Goodin Indu B. Maiti George J. Wagner 《Plant cell reports》2013,32(11):1771-1782
Key message
Phylloplanins are plant-derived, antifungal glycoproteins produced by leaf trichomes. Expression of phylloplanin-GFP fusion gene to the apoplast of a blue mold susceptible tobacco resulted in increased resistance to this pathogen.Abstract
Tobaccos and certain other plants secrete phylloplanin glycoproteins to aerial surfaces where they appear to provide first-point-of-contact resistance against fungi/fungi-like pathogens. These proteins can be collected by water washing of aerial plant surfaces, and as shown for tobacco and a sunflower phylloplanins, spraying concentrated washes onto, e.g., turf grass aerial surfaces can provide resistance against various fungi/fungi-like pathogens, in the laboratory. These results suggest that natural-product, phylloplanins may be useful as broad-selectivity fungicides. An obvious question now is can a tobacco phylloplanin gene be introduced into a disease-susceptible plant to confer endogenous resistance. Here we demonstrate that introduction of a tobacco phylloplanin gene—as a fusion with the GFP gene—targeted to the apoplasm can increase resistance to blue mold disease in a susceptible host tobacco. 相似文献6.
Benjamin Maasoumy Kerstin Port Antoaneta Angelova Markova Beatriz Calle Serrano Magdalena Rogalska-Taranta Lisa Sollik Carola Mix Janina Kirschner Michael P. Manns Heiner Wedemeyer Markus Cornberg 《PloS one》2013,8(2)
Background
HCV protease inhibitors (PIs) boceprevir and telaprevir in combination with PEG-Interferon alfa and Ribavirin (P/R) is the new standard of care in the treatment of chronic HCV genotype 1 (GT1) infection. However, not every HCV GT1 infected patient is eligible for P/R/PI therapy. Furthermore phase III studies did not necessarily reflect real world as patients with advanced liver disease or comorbidities were underrepresented. The aim of our study was to analyze the eligibility and safety of P/R/PI treatment in a real world setting of a tertiary referral center.Methods
All consecutive HCV GT1 infected patients who were referred to our hepatitis treatment unit between June and November 2011 were included. Patients were evaluated for P/R/PI according to their individual risk/benefit ratio based on 4 factors: Treatment-associated safety concerns, chance for SVR, treatment urgency and nonmedical patient related reasons. On treatment data were analyzed until week 12.Results
208 patients were included (F3/F4 64%, mean platelet count 169/nl, 40% treatment-naïve). Treatment was not initiated in 103 patients most frequently due to safety concerns. 19 patients were treated in phase II/III trials or by local centers and a triple therapy concept was initiated at our unit in 86 patients. Hospitalization was required in 16 patients; one patient died due to a gastrointestinal infection possibly related to treatment. A platelet count of <110/nl was associated with hospitalization as well as treatment failure. Overall, 128 patients were either not eligible for therapy or experienced a treatment failure at week 12.Conclusions
P/R/PI therapies are complex, time-consuming and sometimes dangerous in a real world setting, especially in patients with advanced liver disease. A careful patient selection plays a crucial role to improve safety of PI based therapies. A significant number of patients are not eligible for P/R/PI, emphasizing the need for alternative therapeutic options. 相似文献7.
Developmental and Environmental Effects on Sesquiterpene Lactones in Cultivated Arnica montana L.
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Milka Todorova Antoaneta Trendafilova Antonina Vitkova Maria Petrova Ely Zayova Daniela Antonova 《化学与生物多样性》2016,13(8):976-981
The amount of sesquiterpene lactones and the lactone profile of Arnica montana L. in flowering and seed formation stages in vitro and in vivo propagated from seeds of German, Ukrainian, and Austrian origin and grown in two experimental fields were studied. It was found that in vitro propagated 2‐year plants in full flowering stage accumulated higher amount of lactones in comparison to in vivo propagated 3‐year plants and to the seed formation stage, respectively. Helenalins predominated in in vivo propagated 2‐year or in vitro propagated 3‐year plants. 2‐Methylbutyrate (2MeBu) was the principal ester in the samples with prevalence of helenalins, while isobutyrate (iBu) was the major one in the samples with predominance of 11,13‐dihydrohelenalins. The results revealed that the environmental conditions on Vitosha Mt. are more suitable for cultivation of A. montana giving higher content of lactones. 相似文献
8.
Hillebrenner MG Eason JC Trayanova NA 《American journal of physiology. Heart and circulatory physiology》2004,286(3):H909-H917
Energy requirements for successful antiarrhythmia shocks are arrhythmia specific. However, it remains unclear why the probability of shock success decreases with increasing arrhythmia complexity. The goal of this research was to determine whether a diminished probability of shock success results from an increased number of functional reentrant circuits in the myocardium, and if so, to identify the responsible mechanisms. To achieve this goal, we assessed shock efficacy in a bidomain defibrillation model of a 4-mm-thick slice of canine ventricles. Shocks were applied between a right ventricular cathode and a distant anode to terminate either a single scroll wave (SSW) or multiple scroll waves (MSWs). From the 160 simulations conducted, dose-response curves were constructed for shocks given to SSWs and MSWs. The shock strength that yielded a 50% probability of success (ED(50)) for SSWs was found to be 13% less than that for MSWs, which indicates that a larger number of functional reentries results in an increased defibrillation threshold. The results also demonstrate that an isoelectric window exists after both failed and successful shocks; however, shocks of strength near the ED(50) value that were given to SSWs resulted in 16.3% longer isoelectric window durations than the same shocks delivered to MSWs. Mechanistic inquiry into these findings reveals that the two main factors underlying the observed relationships are 1) smaller virtual electrode polarizations in the tissue depth, and 2) differences in preshock tissue state. As a result of these factors, intramural excitable pathways leading to delayed breakthrough on the surface were formed earlier after shocks given to MSWs compared with SSWs and thus resulted in a lower defibrillation threshold for shocks given to SSWs. 相似文献
9.
Kostova I Dinchev D Rentsch GH Dimitrov V Ivanova A 《Zeitschrift für Naturforschung. C, Journal of biosciences》2002,57(1-2):33-38
The known furostanol saponins methylprotodioscin and protodioscin and two new sulfated saponins, sodium salt of 26-O-beta-glucopyranosyl-22alpha-methoxy-(25R)-furost-5-ene-3beta,26-diol-3-O-alpha-rhamnopyranosyl-(1-->2)-beta-4-O-sulfo-glucopyranoside (methylprototribestin) and sodium salt of 26-O-beta-glucopyranosyl-22alpha-hydroxy-(25R)-furost-5-ene-3beta,26-diol-3-O-alpha-rhamnopyranosyl-(1-->2)-beta-4-O-sulfo-glucopyranoside (prototribestin) have been isolated from the aerial parts of Tribulus terrestris L. growing in Bulgaria. The structures of the new compounds were elucidated on the basis of 1D and 2D (DQF-COSY, TOCSY, HSQC-TOCSY, HSQC, HMBC, ROESY) NMR data, ESI mass spectra and chemical transformation. 相似文献
10.