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41.
42.
Towards optimization of cyanobacteria as biotechnologically relevant producers of molecular hydrogen, a clean and renewable energy source 总被引:15,自引:0,他引:15
In discussions about alternatives to our current fossil energy sources, basic and applied research leading to biological
production of molecular hydrogen utilizing cyanobacteria deserves serious attention. In these oxygenic phototrophic bacteria,
hydrogen can be produced by the activity of either nitrogenases or reversible/bidirectional hydrogenases. Knowledge of the
physiological and molecular basis of some of the processes involved in hydrogen metabolism in these peculiar microorganisms
has increased during the last decade. However, further efforts are required in basic as well as applied research in order
to obtain a clear impression of these processes and their regulation. This information might then constitute the basis for
optimizing the efficiency of hydrogen evolution by cyanobacteria. Progress might be achieved by screening more cyanobacterial
strains for their ability to produce and evolve hydrogen, by genetically manipulating specific strains as well as by improving
the conditions for cultivation in bioreactors.
Received: 17 February 1998 / Received revision: 24 April 1998 / Accepted: 27 April 1998 相似文献
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This study was designed to establish a sensitive bioassay for bovine platelet-activating factor (PAF), to determine if the bovine embryo secretes PAF in vitro and if PAF release is correlated with the embryo's potential to establish a pregnancy. Using an equine platelet aggregation assay, lipid extracted culture media from 33 Day-7 embryos (individually cultured for 18 hours in 1 ml of Ham's F10 containing 0.4% BSA at 37 degrees C in an air: CO2 mixture of 95:5 prior to their transfer to recipient heifers) and from control media (n=15, Ham's F10+0.4% BSA incubated simultaneously without embryos) were investigated. In addition, culture media from Day-6 (n=6) and Day-1 (2-cell, n=12) bovine embryos that were cultured for 4 hours but not transferred were examined. The aggregation assay proved to be sensitive to 5 pg of PAF. The assay proved to be specific, since the PAF receptor antagonist SRI 63-441 inhibited platelet aggregation induced by culture media in dosages comparable to aggregation induced by synthetic PAF18. From the 15 Day-7 embryos that established a pregnancy 2 contained measurable amounts of PAF in their culture media. No PAF was detected in the culture media from 13 embryos that succeeded, in the 18 embryos that failed to establish a pregnancy, or in the control media. One of 6 Day-6 embryos and 3 of 12 Day-1 (2-cell) embryos secreted detectable amounts of PAF into the culture media. Although the results indicate that some bovine embryos release PAF or a PAF-like substance in vitro, PAF measurements in the culture medium seem not to be a suitable method for the evaluation of bovine embryos prior to transfer. 相似文献
45.
Timothy J. Brickman Jan-Gerd Hansel Marvin J. Miller Sandra K. Armstrong 《Biometals》1996,9(2):191-203
Hydroxamate siderophores of virulent Bordetella pertussis and Bordetella bronchiseptica strains were purified using a simple large-scale isolation procedure, and identified by various spectroscopic techniques as the macrocyclic dihydroxamate siderophore trivially known as alcaligin, 1,8(S),11,18(S)-tetrahydroxy-1,6,11,16-tetraazacycloeicosane-2,5,12,15-tetrone, which was previously isolated from the taxonomically-related bacterial species Alcaligenes denitrificans subsp. xylosoxydans. Alcaligin purified from iron-depleted cultures of B. pertussis and B. bronchiseptica exhibited specific growth-promoting activity under iron-restricted conditions for Bordetella indicator strains, and were active in [55Fe]ferric alcaligin transport assays. Evidence suggests that several C
2-symmetric conformations of alcaligin exist simultaneously in both methanolic and aqueous solution. 相似文献
46.
Deden Derajat Matra Roedhy Poerwanto Edi Santosa Sobir Hisao Higashio Hiroyuki Anzai Eiichi Inoue 《Tropical plant biology》2016,9(1):29-41
The genetic variation and relationships of the mangosteen (Garcinia mangostana L.) were observed across mangosteen populations in Java, Indonesia using newly identified microsatellite loci and morphological characters. In this study, we developed an improved protocol to isolate microsatellite loci, named Selective Repeats from AFLP Sequence, by using a hybridized membrane. Twenty microsatellite loci were evaluated using 78 individuals from five mangosteen populations, and we successfully amplified four closely related Garcinia species, including G. malaccensis, G. hombroniana, G. celebica, and G. porrecta. Eight loci were monomorphic and the others were polymorphic. Sixty-nine alleles were found, with 3.491 per locus on an average. Genetic diversity (H?) was calculated with an average across loci within population (H?S) as 0.39, an average loci across many populations (H?T) as 0.444, and genetic differentiation (F?ST) as 0.147. Furthermore, based on morphological characters, mangosteen individuals from four populations including Leuwiliang, Wanayasa, Puspahiang, and Kaligesing also had morphologically distinct fruit weight, rind weight, and rind thickness among populations. The study also elucidated the dispersal pattern of mangosteen in Java; the source of the genotype mangosteen in Java population was the Wanayasa population. In addition, we found evidence of tetraploidy in mangosteen. These results have potential applications in future breeding, conservation studies, and genetic assessment of mangosteen and their closely related species. 相似文献
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This study was conducted to characterize bovine platelets with respect to serotonin (5-HT) concentration and platelet-activating factor (PAF)-activation and to examine the in vitro effects of PAF and platelet-derived compounds on bovine luteal progesterone (P4) production. The concentration of 5-HT in platelets, as determined by high-performance liquid chromatography, was 538.8 +/- 40.83 ng/1 x 10(8) platelets. Based on a circulating platelet concentration range of 2.3 x 10(8) 5.8 x 10(8) platelets/ml, the circulating concentration of 5-HT would be approximately 1239-3125 ng/ml of blood. Bovine platelets were found to aggregate in response to PAF (1-40 ng/0.5 ml), with maximal aggregation occurring at 20-40 ng/0.5 ml. Coincubation of luteal cells with platelets (1 x 10(7)-4 x 10(8] enhanced luteal P4 production (p less than 0.05). Addition of the 5-HT receptor antagonist mianserin blocked the platelet-induced increases in P4 (p less than 0.05). Preincubation of platelets with indomethacin did not alter the production of P4 (p greater than 0.05), nor did the addition of propranolol (p greater than 0.05). Platelet-derived growth factor at 8 and 16 ng/ml enhanced basal P4 production (p less than 0.05) but had no effect on the responsiveness of luteal cells to luteinizing hormone (LH) (p greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
48.
Prostacyclin, prostaglandin F2 alpha and progesterone production by bovine luteal cells during the estrous cycle 总被引:1,自引:0,他引:1
Corpora lutea (CL) were collected from Holstein heifers on Days 5, 10, 15 and 18 (5/day) of the estrous cycle. Dispersed luteal cell preparations were made and 10(6) viable luteal cells were incubated with bovine luteinizing hormone (LH) and different amounts of arachidonic acid in the presence and absence of the prostaglandin (PG) synthetase inhibitor indomethacin. The concentrations of progesterone, PGF2 alpha and 6-keto-PGF1 alpha, the stable inactive metabolite of prostacyclin (PGI2), were measured. Day 5 CL had the greatest initial content of 6-keto-PGF1 alpha (1.01 +/- 0.16 ng/10(6) cells), and synthesized more 6-keto-PGF1 alpha (2.55 +/- 0.43) than CL collected on Days 10 (0.57 +/- 0.11), 15 (0.08 +/- 0.05) and 18 (0.19 +/- 0.03) during a 2-h incubation period. Arachidonic acid stimulated the production of 6-keto-PGF1 alpha by Days 10, 15 and 18 luteal tissue. PGF2 alpha was produced at a greater rate on Day 5 (0.69 +/- 0.17 ng/10(6) cells) than on Days 10 (0.06 +/- 0.01), 15 (0.04 +/- 0.02) and 18 (0.08 +/- 0.01). Arachidonic acid stimulated and indomethacin inhibited the production of PGF2 alpha, in most cases. The initial content of 6-keto-PGF1 alpha was higher than that of PGF2 alpha on all days of the cycle and more 6-keto-PGF1 alpha was synthesized in response to arachidonic acid addition. The ratio of 6-keto-PGF1 alpha content to PGF2 alpha content was 4.39, 2.30, 1.25 and 1.13 on Days 5, 10, 15 and 18, respectively.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
49.
Metabolism of phospholipids and the characterization of fatty acids in bovine corpus luteum 总被引:2,自引:2,他引:0 下载免费PDF全文
1. Phosphatidylcholine was the predominant phospholipid in bovine corpora lutea; it accounted for about 50% of the total phospholipid phosphorus. Phosphatidylethanolamine (13%) and ethanolamine plasmalogen (8-9%) were the next two major components. 2. After incubation of the tissue with [(32)P]orthophosphate the total radioactivity and specific radioactivity of phosphatidylinositol were higher than those of any other lipid. 3. Luteinizing hormone failed to increase significantly the incorporation of [(32)P]orthophosphate into total phospholipids from luteal tissue slices, but did stimulate progesterone synthesis and lactate production. 4. The proportion of oleate (18:1) in the neutral lipids and phospholipids was higher than that of any other fatty acid. 5. The proportion of unsaturated fatty acid in the tissue lipids exceeded 60%, and almost half of this was polyunsaturated. Arachidonate (20:4), docosatetraenoate (22:4) and docosapentaenoate (22:5) were the principal polyunsaturated fatty acids. 6. After incubation of luteal tissue with [1-(14)C]acetate, the greatest proportion of radioactivity in the fatty acids isolated from the total lipid fraction was in palmitate (16:0) and docosatetraenoate (22:4). Polyunsaturated fatty acids accounted for almost 50% of the (14)C radioactivity incorporated and this pattern was observed in phospholipids, triglycerides and free fatty acids. 相似文献
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