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31.
Pierluigi Gariboldi Francesca Pelizzoni Marco Tat Luisella Verotta Nadia El-Sebakhy Aya M. Asaad Rokia M. Abdallah Soad M. Toaima 《Phytochemistry》1995,40(6):1755-1760
Three new cycloartane glycosides, trigonoside I, II and III, and the known astragalosides I and II were isolated from the roots of Astragalus trigonus. The structures of the new glycosides were totally elucidated by high field (600 MHz) NMR analyses as cycloastragenol-6-O-β-xylopyranoside, cycloastragenol-3-O-[-l-arabinopyranosyl(1 → 2)-β-d-xylopyranosyl]-6-O-β- d-xylopyranoside and cycloastragenol-3-O-[-l-arabinopyranosyl(1 → 2)-β-d-(3-O-acetyl)-xylopyranosyl]-6-O-β-d-xylopyranoside. 相似文献
32.
Aminophylline, an inhibitor of cyclic nucleotide phosphodiesterase (EC 3.1.4.17), inhibits elongation and correlated H+ and K+ transport in embryos of Haplopappus gracilis and in pea internode segments. Moreover, the drug strongly inhibits the stimulation of these processes by fusicoccin and indole-3-acetic acid and reduces passive permeability of the membrane. The possible mechanisms of action of aminophylline are discussed.Abbreviations cAMP
adenosine 3:5-cyclic monophosphate
- FC
fusicoccin
- IAA
indole-3-acetic acid
- MES
2-N-morpholinoethanesulfonic acid
- PDE
cyclic nucleotide phosphodiesterase 相似文献
33.
Francesca Clementi Jone Rossi Lucia Costamagna Jolanda Rosi 《Antonie van Leeuwenhoek》1980,46(4):399-405
Schwanniomyces castellii and Endomycopsis fibuligera Produced extracellular amylase(s) when grown on various carbon sources and at different pH values. Both yeast species showed significant amylase synthesis in the presence of either maltose or soluble starch. On the other substrates tested (glucose, cellobiose, sucrose, trehalose, melezitose, raffinose, ethanol, glycerol) differences were found regarding growth and amylase production. Free glucose in the culture medium apparently inhibited enzyme synthesis. The pH range allowing maximal growth and amylase production was 4.5–6.0 for E. fibuligera and 5.5–7.0 for S. castellii. 相似文献
34.
D.J. Back A.M. Breckenridge Francesca E. Crawford M.LE. Orme P.H. Rowe T.P. Sloan Eileen Smith 《Steroids》1978,32(4):423-433
The disappearance of ethinylestradiol from the blood of rabbits has been studied, following the intravenous administration of this steroid. The disappearance followed two exponentials, the first having a half life () of 5.5 min and the second, apparently terminal exponential was also rapid (). The plasma clearance was 150 ml/min which suggests almost total clearance of this steroid during a single passage through the liver. Bile contained a significant concentration of EE conjugates and thus this steroid could undergo enterohepatic recirculations. A large oral dose of unlabelled EE, given prior to intravenous administra tion of tritiated EE, considerably altered the pharmacokinetics of the latter by saturating both phase one metabolism (changes of the steroid nucleus) and the secretion of conjugates into bile. It was not clear whether phase two metabolism (conjugation) was also saturated. 相似文献
35.
Theophylline, an inhibitor of cyclic nucleotide phosphodiesterase, induced a block of the cell cycle in G1, a temporary arrest in G2 and 70% decrease in the uptake of labelled thymidine in roots of Haplopappus. These effects are compared to those previously found with aminophylline and discussed in view of the possible involvement of cAMP in the regulation of the cell cycle in plants. 相似文献
36.
Alessandro Zuddas Germano Oberto Francesca Vaglini Flavia Fascetti Francesco Fornai Giovanni U. Corsini 《Journal of neurochemistry》1992,59(2):733-739
In cynomologus monkeys, systemic administration of MK-801, a noncompetitive antagonist for the N-methyl-D-aspartate receptor, prevented the development of the parkinsonian syndrome induced by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). MK-801 also attenuated dopamine depletion in the caudate and putamen and protected dopaminergic neurons in the substantia nigra from the degeneration induced by the neurotoxin. Nevertheless, 7 days after MPTP administration in the caudate and putamen of monkeys also receiving MK-801, the levels of toxic 1-methyl-4-phenylpyridinium were even higher than those measured in monkeys receiving MPTP alone. This indicates that the protective action of MK-801 is not related to MPTP metabolism and strongly suggests that, in primates, the excitatory amino acids could play a crucial role in the mechanism of the selective neuronal death induced by MPTP. 相似文献
37.
Johan C. Sanders M. Francesca Ottaviani Arie van Hoek Antonie J. W. G. Visser Marcus A. Hemminga 《European biophysics journal : EBJ》1992,21(5):305-311
Model membranes with unsaturated lipid chains containing various amounts of M13 coat protein in the -helical form were studied using time-resolved fluorescence and ESR spectroscopy. The lipid-to-protein (L/P) ratios used were > 12 to avoid protein-protein contacts and irreversible aggregation leading to -polymeric coat protein. In the ESR spectra of the 12-SASL probe in dioleoyl phosphatidylcholine (DOPC) bilayers no second protein induced component is observed upon incorporation of M13 coat protein. However, strong effects are detected on the ESR lineshapes upon changing the protein concentration. The ESR lineshapes are simulated by assuming a fixed ratio between the parallel (D) and perpendicular (D) diffusion coefficients of 4, and an order parameter equal to zero. It is found that increasing the protein concentration from L/P to L/P 15 results in a decrease of the rotational diffusion coefficient D from 3.4 × 107 to 1.9 × 107 s–1. In the time-resolved fluorescence experiments with DPH-propionic acid as a probe, it is observed that increasing the M13 coat protein concentration causes an increase of the two fluorescent lifetimes, indicating an increase in bilayer order. Analysis of the time-resolved fluorescence anisotropy decay allows one to quantitatively determine the order parameters P2 and P4, and the rotational diffusion coefficient D of the fluorescent probe. The order parameters P2 and P4 increase from 0.34 to 0.55 and from 0.59 to 0.77, respectively, upon adding M13 coat protein to DOPC bilayers with an L/P ratio of 35. The rotational diffusion coefficient D of the DPH-propionic acid probe decreases on incorporating M13 coat protein, in accordance with the ESR results. It is concluded that M13 coat protein in the -monomeric state is not able to produce a long living lipid boundary shell and consequently an immobilization of the lipids. An overall effect on the lipids is induced, resulting in a reduction in the dynamics and an increase in average lipid order. The hydrophobic region of M13 coat protein is proposed to perfectly match the lipid bilayer, resulting in a relatively small distortion of the bilayer structure of the lipid system. 相似文献
38.
Long single-stranded DNA molecules have been observed at electron microscope in DNA preparations from synchronized Chinese hamster cells. The amount of single strandedness in parental DNA increases following a prolonged block of DNA synthesis by hydroxyurea as judged by the results obtained using an improved hydroxyapatite chromatography (Hanania et al., 1975). As far as newly replicated DNA is concerned, an increase of the single strand amount has been observed in DNA preparations from cells actively synthesizing DNA. 相似文献
39.
Impaired carotenogenesis can affect organization and functionality of etioplast membranes 总被引:1,自引:0,他引:1
Isabella Moro Francesca Dalla Vecchia Nicoletta La Rocca Flavia Navari-Izzo Mike Frank Quartacci Daniela Di Baccio Wolfhart Rüdiger Nicoletta Rascio 《Physiologia plantarum》2004,122(1):123-132
The effects of impaired carotenogenesis on plastid membrane organization, functionality and stability were studied in etiolated barley plants grown at 20 and 30°C. The plants were treated with norflurazon or amitrole, two herbicides affecting phytoene desaturation and lycopene cyclization, respectively. At 20°C, the amitrole-treated etioplasts, which accumulated lycopene in their inner membranes, exhibited disorganized prolamellar bodies, containing a prevalent form of non-phototransformable protochlorophyllide (Pchlide). They also showed a certain difficulty in reducing the phototransformable pigment to chlorophyllide when exposed to light, and were unable to reform the active ternary complex [protochlorophyllide–oxidoreductase (POR)–Pchlide–NADPH] when placed back in darkness. No ultrastructural alterations were found in norflurazon-treated etioplasts, with carotenogenesis inhibited at the phytoene desaturation step. In these latter organelles, Pchlide, whose forms were comparable with those of the control etioplasts, was photoreduced quickly after illumination and the ternary complex was reformed during a subsequent dark period. Thus, the impaired carotenogenesis leading to the accumulation of lycopene showed greater interference with the etioplast membrane arrangement and functionality than did the earlier interruption of the biosynthetic pathway at the phytoene level. This might be due to the different interactions of the distinct carotenoid precursors with other membrane components. However, in etioplasts of norflurazon-treated plants, a rise in growth temperature caused a partial demolition of prolamellar bodies, showing a lowered thermostability of the carotenoid-deficient membranes. This latter effect strengthens the concept that a correct and complete carotenogenesis pathway, leading to the synthesis of polar carotenoids (i.e. xanthophylls), is required for the maintenance of stable plastid membranes. 相似文献
40.
Summary Studies on ragweed have been carried out in the province of Trieste (Northern Italy) in which it is becoming widespread. The floristic records, the increasing amount of airborne pollen monitored and the relevant skin reactivity are reported. This phenomenon, though still at the beginning, is actually showing an upward trend due to man's intervention over wider and wider areas which as a consequence become suitable for the settlement of these anthropophitic species. The aerobiological data are compared to the skin reactivities of allergic subjects. 相似文献