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51.
Benoit Cousineau Fabrice Leclerc Robert Cedergren 《Journal of molecular evolution》1997,45(6):661-670
Sequence similarity has given rise to the proposal that IF-2, EF-G, and EF-Tu are related through a common ancestor. We evaluate
this proposition and whether the relationship can be extended to other factors of protein synthesis. Analysis of amino acid
sequence similarity gives statistical support for an evolutionary affiliation among IF-1, IF-2, IF-3, EF-Tu, EF-Ts, and EF-G
and suggests further that this association is a result of gene duplication/fusion events. In support of this mechanism, the
three-dimensional structures of IF-3, EF-Tu, and EF-G display a predictable domain structure and overall conformational similarity.
The model that we propose consists of three consecutives duplication/fusion events which would have taken place before the
divergence of the three superkingdoms: eubacteria, archaea, and eukaryotes. The root of this protein superfamily tree would
be an ancestor of the modern IF-1 gene sequence. The repeated fundamental motif of this protein superfamily is a small RNA
binding domain composed of two α-helices packed along side of an antiparallel β-sheet.
Received: 17 October 1996 / Accepted: 10 June 1997 相似文献
52.
Freeman Bradley D.; Quezado Zenaide; Zeni Fabrice; Natanson Charles; Danner Robert L.; Banks Steven; Quezado Marcello; Fitz Yvonne; Bacher John; Eichacker Peter Q. 《Journal of applied physiology》1997,83(5):1467-1475
Freeman, Bradley D., Zenaide Quezado, Fabrice Zeni, CharlesNatanson, Robert L. Danner, Steven Banks, Marcello Quezado, YvonneFitz, John Bacher, and Peter Q. Eichacker. rG-CSF reduces endotoxemia and improves survival during E. coli pneumonia. J. Appl.Physiol. 83(5): 1467-1475, 1997.We investigatedthe effects of recombinant granulocyte colony-stimulating factor(rG-CSF) during canine bacterial pneumonia. Beagles with chronictracheostomies received daily subcutaneous rG-CSF (5 µg/kg body wt)or placebo for 14 days, beginning 9 days before intrabronchialinoculation with E. coli. Animalsreceived antibiotics and fluid support; a subset received humidifiedoxygen (fractional inspired O20.40). Compared with controls, rG-CSF increased circulating neutrophil counts (57.4 vs. 11.0 × 103/mm3,day 1 after infection;P = 0.0001), decreased plasmaendotoxin (7.5 vs. 1.1 EU/ml at 8 h; P < 0.01) and serum tumor necrosis factor- (3,402 vs.729 pg/ml at 2 h; P = 0.01) levels,and prolonged survival (relative risk of death = 0.45, 95% confidenceinterval 0.21-0.97; P = 0.038).Also, rG-CSF attenuated sepsis-associated myocardial dysfunction(P < 0.001). rG-CSF had no effect onpulmonary function or on blood and lung bacteria counts (allP = not significant). Other animalschallenged with endotoxin (4 mg/kg iv) after similar treatment withrG-CSF had lower serum endotoxin levels (7.62 vs. 5.81 log EU/ml at 6 h; P < 0.01) and less cardiovasculardysfunction (P < 0.05 to < 0.002)but similar tumor necrosis factor- levels (P = not significant) compared withcontrols. Thus prophylactic rG-CSF sufficient to increase circulatingneutrophils during bacterial pneumonia may improve cardiovascularfunction and survival by mechanisms that in part enhance the clearanceof bacterial toxins but do not improve lung function. 相似文献
53.
Dr. Edward B. Blanchard Guy C. McCoy Frank Andrasik Maryrose Acerra Thomas P. Pallmeyer Robert Gerardi Mindy Halpern Alison Musso 《Applied psychophysiology and biofeedback》1984,9(4):471-495
In a controlled trial, thermal biofeedback (n=20) and abbreviated progressive relaxation (n=22) were compared in the treatment of mild to moderate hypertensive patients whose blood pressures (BP) were initially controlled on two medications. For the clinical end point of maintaining control of BP on a single drug after treatment, biofeedback was superior to relaxation training (at 3 months, 47% success for biofeedback versus 23% for relaxation). This same result tended to be true for patient-measured home BPs. BPs from laboratory psychophysiological testing showed no consistent advantage for one treatment over the other.This research was supported by a grant from NHLB1, HL-27622. 相似文献
54.
55.
Jiann-Shin Chen D.K. Blanchard 《Biochemical and biophysical research communications》1984,122(1):9-16
Clostridium pasteurianum has two distinct hydrogenases, the bidirectional hydrogenase and the H2-oxidizing (uptake) hydrogenase. The H2-oxidizing hydrogenase has been purified (up to 970-fold) to a specific activity of 17,600 μmol H2 oxidized/min·mg protein (5 mM methylene blue) or 3.5 μmol H2 produced/min·mg protein (1 mM methyl viologen). The uptake hydrogenase has a Mr of 53,000 (one polypeptide chain). Depending upon how protein was measured, the Fe and S= contents (gatom/mol) were 4.7 and 5.2 (by the dye-binding assay) or 7.2 and 8.0 (by the Lowry method). Both reduced and oxidized forms of the enzyme gave electron paramagnetic resonance signals. The activation energy for H2-production and H2-oxidation by the uptake hydrogenase was 59.1 and 31.2 kJ/mol, respectively. In the exponential phase of growth, the ratio of uptake hydrogenase/bidirectional hydrogenase in NH3-grown cells was much lower than that in N2-fixing cells. 相似文献
56.
Attack and defensive behaviour in the albino rat 总被引:3,自引:0,他引:3
Attack of dominant colony males of an albino rat (Rattus norvegicus) strain, on introduced strangers, produced a non-random distribution of bites, with ventral trunk virtually never bitten. Also, vibrissae-contact of attacker and defender interfered with bites to the defender's head and upper back. The specific agonistic reactions of attacking and defending rats appeared to involve strategies based on these limitation on attack: defenders utilized 'boxing' and lying 'on-the-back' behaviour, which interposed ventral trunk and vibrissae between attacker and defender. In turn, the 'lateral display' permitted attackers to circumvent the defender's behaviour. Limitations on attack therefore appeared to underlie the specific agonistic behaviour of both attacking and defending rats. 相似文献
57.
The association of [3H] [D-Ala2, D-Leu5] enkephalin ([3H]DADLE]) with mouse neuroblastoma cells (N4TG1) was investigated. Under identical conditions the time course, dose response curve and temperature dependence for ligand uptake were similar to those for ligand-induced receptor loss (down regulation). Uptake of [3H]DADLE was inhibited by opiate ligands as well as by the metabolic inhibitors sodium azide and 2,4 dinitrophenol. Comparison of the effects of these inhibitors on receptor binding, ligand uptake and receptor loss indicated that these cells accumulate [3H]DADLE in excess of their surface receptor number. The data suggest that receptor recycling occurs and that ligand is internalized via receptor mediated endocytosis. 相似文献
58.
Ferredoxin or flavodoxin mediates electron flow from H2-hydrogenase to metronidazole[1-(2-hydroxyethyl)-2-methyl-5-nitroimidazole] to cause the reduction of the latter compound. The reduction of metronidazole in solution is irreversible because the reduced compound further decomposes. Since metronidazole loses its absorption peak at 320 nm upon reduction, the rate of reduction can be monitored spectrophotometrically. When a solution of metronidazole at 0.1 to 0.5 mm is supplemented with ferredoxin- andflavodoxin-free hydrogenase and placed under H2, the rate of metronidazole reduction is proportional to the amount of ferredoxin or flavodoxin added. This forms the basis for an assay that can measure 10 to 1000 ng of ferredoxin or 100–1000 ng of flavodoxin/ml of assay mixture. 相似文献
59.
Fabrice Rebeille Richard Bligny Roland Douce 《Archives of biochemistry and biophysics》1982,219(2):371-378
In view of the importance of Pi in the control of cell metabolism, it was of interest to study the mechanism and regulation of Pi uptake by Acer pseudoplatanus cells grown as cell suspensions. At low external Pi concentrations up to 10 mm, sycamore cells incorporate phosphate against a concentration gradient, by a process which is energy dependent. Under these conditions the intracellular Pi concentration is maintained constant (2–3 mm). On the contrary at high external Pi concentrations, higher than that which counterpoises the cytoplasmic Pi concentration (approximately 10 mm), Pi enters the cell by slow diffusion and the intracellular Pi concentration increases continuously as the extracellular Pi concentration increases from 15 to 50 mm. When sycamore cells are transferred to a phosphate-deficient medium, growth slows down considerably and ceases after 4–5 days. During this time, intracellular Pi concentration falls from 3 to 0.1 mm and phosphate esters from 8 to 2 mm. Phosphate starvation stimulates the uptake indicating that phosphate uptake depends on the intracellular phosphate and/or cytoplasmic ester-P pool. Pi uptake by Pi-starved cells is strongly dependent on the pH of the medium. 相似文献
60.
Preparation of spermatogenic cell populations at specific stages of differentiation in the human. 总被引:1,自引:0,他引:1
Y Blanchard M T Lavault D Quernee D Le Lannou B Lobel D Lescoat 《Molecular reproduction and development》1991,30(3):275-282
Studying biochemical events in human spermatogenesis requires separated populations of spermatogenic cells. Dissociation of these cells was performed by a Trypsin-DNAse method adapted from the technique used for rodents. Cell separation was performed by centrifugal elutriation. Seven populations were collected, one further purified by Percoll gradient centrifugation, giving nine different cell populations. The efficiency of the cell separation was evaluated by phase contrast microscopy, flow cytometric DNA analysis, and electron microscopy. Five populations were enriched in spermatids: two in round spermatids (87% and 73%), another in round (52%) and elongating (44%) spermatids, another constituted by 80% elongating spermatids, and the last by 90% elongated spermatids. Two of the four remaining populations were enriched in primary spermatocytes (74% and 54%); another population was the upper part of the Percoll gradient and constituted cytoplasmic lobes and residual bodies (89%); the last population was made up of various cells, with no specific enrichment. Electron microscopic observations revealed good preservation of the separated cells; only the flagella from elongated spermatids were lost. Furthermore, an unusual pattern of nucleoplasm distribution during stages 2-4 of spermatid differentiation was observed and its signification is discussed with regard to the shape of the human spermatozoon. 相似文献