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991.
Long-range negative correlation of glucose dynamics in humans and its breakdown in diabetes mellitus
Ogata H Tokuyama K Nagasaka S Ando A Kusaka I Sato N Goto A Ishibashi S Kiyono K Struzik ZR Yamamoto Y 《American journal of physiology. Regulatory, integrative and comparative physiology》2006,291(6):R1638-R1643
Diurnal fluctuations in glucose levels continuously monitored during normal daily life are investigated using an extended random walk analysis, referred to as detrended fluctuation analysis (DFA), in 12 nondiabetic subjects and 15 diabetic patients. The DFA exponent alpha = 1.25 +/- 0.29 for healthy individuals in the "long-range" (>2 h) regime is shown to be significantly (P < 0.01) smaller than the reference "uncorrelated" value of alpha = 1.5, suggesting that the instantaneous net effects of the dynamical balance of glucose flux and reflux, causing temporal changes in glucose concentration, are long-range negatively correlated. By contrast, in diabetic patients, the DFA exponent alpha = 1.65 +/- 0.30 is significantly (P < 0.05) higher than that in nondiabetic subjects, evidencing a breakdown of the long-range negative correlation. It is suggested that the emergence of such positive long-range glucose correlations in diabetic patients-indicating that the net effects of the flux and reflux persist for many hours-likely reflects pathogenic mechanisms of diabetes, i.e., the lack of long-term stability of blood glucose and that the long-range negatively correlated glucose dynamics are functional in maintaining normal glucose homeostasis. 相似文献
992.
Koprowska-Ratajska M Kluczyk A Stefanowicz P Bartosz-Bechowski H Szewczuk Z 《Amino acids》2009,36(2):309-315
A direct solid-phase synthesis of a series of substituted benzimidazole-containing peptides is described. The method involves
on-resin formation of new amino acids containing benzimidazole derivatives in the side chain. The heterocycle conjugates were
obtained by reaction between aldehydes and peptides containing β-(3,4-diaminophenyl)alanine residue, immobilized on a polymeric
solid support. 相似文献
993.
994.
Gorodkiewicz E Sankiewicz A Figaszewski ZA 《Folia histochemica et cytobiologica / Polish Academy of Sciences, Polish Histochemical and Cytochemical Society》2010,48(4):687-692
Abciximab (Abci) and eptifibatide (Epti) are antiaggregate drugs which may reduce thrombotic complications in acute coronary syndromes. The aim of this work was the investigation of the interaction between the phospholipid-GPIIb/IIIa glycoprotein complex and Abci or Epti, and the influence of these drugs on the phospholipid ratio in the platelet membrane. The interaction between the phospholipid-GPIIb/IIIa glycoprotein complex and antiaggregate drugs were investigated using the Surface Plasmon Resonance Imaging technique (SPRI). Phospholipids phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylethanolamine (PE), phosphatidylcholine (PC) and sphingomyelin (SM) were first immobilized onto the gold chip surface. The phospholipid ratio in the platelet membrane was determined by the HPLC. Only PI, PS, PE and PC were determined. Human platelets treated 'in vitro' with Abci or Epti exhibit changes in the phospholipid ratio in the platelet membrane. The ratio of PS decreases and PC rises. The SPRI distinctly shows interactions between phospholipids and glycoprotein GPIIb/IIIa, and between the phospholipid-glycoprotein GPIIb/IIIa complex and Abci or Epti. The interaction between phospholipids and glycoprotein GPIIb/IIIa is growing in the sequence: PI相似文献
995.
Samuel T. Wilson Sasha Tozzi Rachel A. Foster Irina Ilikchyan Zbigniew S. Kolber Jonathan P. Zehr David M. Karl 《Applied and environmental microbiology》2010,76(20):6797-6803
The hydrogen (H2) cycle associated with the dinitrogen (N2) fixation process was studied in laboratory cultures of the marine cyanobacterium Crocosphaera watsonii. The rates of H2 production and acetylene (C2H2) reduction were continuously measured over the diel cycle with simultaneous measurements of fast repetition rate fluorometry and dissolved oxygen. The maximum rate of H2 production was coincident with the maximum rates of C2H2 reduction. Theoretical stoichiometry for N2 fixation predicts an equimolar ratio of H2 produced to N2 fixed. However, the maximum rate of net H2 production observed was 0.09 nmol H2 μg chlorophyll a (chl a)−1 h−1 compared to the N2 fixation rate of 5.5 nmol N2 μg chl a−1 h−1, with an H2 production/N2 fixation ratio of 0.02. The 50-fold discrepancy between expected and observed rates of H2 production was hypothesized to be a result of H2 reassimilation by uptake hydrogenase. This was confirmed by the addition of carbon monoxide (CO), a potent inhibitor of hydrogenase, which increased net H2 production rates ∼40-fold to a maximum rate of 3.5 nmol H2 μg chl a−1 h−1. We conclude that the reassimilation of H2 by C. watsonii is highly efficient (>98%) and hypothesize that the tight coupling between H2 production and consumption is a consequence of fixing N2 at nighttime using a finite pool of respiratory carbon and electrons acquired from daytime solar energy capture. The H2 cycle provides unique insight into N2 fixation and associated metabolic processes in C. watsonii.The biological production of hydrogen (H2) can occur as a by-product of photosynthesis, fermentation, and N2 fixation (22). Of these three metabolic pathways, N2 fixation remains a particularly enigmatic process, and to date there is no clear explanation for why H2 evolves during the reduction of N2 (11). The unfavorable energy cost of N2 fixation can be mitigated by reassimilating the released H2 via uptake hydrogenase enzyme activity (30). The coupled production and consumption of H2 during cellular nitrogenase activity creates a H2 cycle that can be hidden from measurements of ambient environmental H2 concentrations and fluxes, depending upon the overall efficiency of H2 assimilation (Fig. (Fig.11).Open in a separate windowFIG. 1.H2 is formed during N2 fixation by the binding of a N2 molecule to the molybdenum-iron protein of the nitrogenase enzyme complex, prior to the reduction of N2 to ammonia (11, 15). The most energetically favorable theoretical in vivo stoichiometry predicts that one mole of H2 is produced for every mole of N2 reduced: N2 + 8H+ + 8e− + 16ATP → 2NH3 + H2 + 16ADP + 16Pi. The production of H2 consumes 25% of the electron flux through nitrogenase and diazotrophs mitigate this loss of potential energy by reassimilating the H2 via uptake hydrogenase (21, 30). The electrons produced by uptake hydrogenase either generate reductant or ATP with simultaneous consumption of O2 (3). (Adapted from reference 32a.)For most cultures of phototrophic marine diazotrophs grown under optimal conditions, complete reassimilation of H2 is not achieved, and the excess H2 is lost to the surrounding environment. This excess H2 equates to the net production of H2 and is expressed as the ratio of H2 formed to N2 fixed or the H2/N2 ratio. To date, H2/N2 ratios have mainly been measured on filamentous, colony-forming diazotrophs such as Anabaena spp. and Trichodesmium spp. with H2 production rates of up to 20 nmol H2 μg chlorophyll a (chl a)−1 h−1 and H2/N2 ratios ranging from 0.01 to 0.48 (3, 20, 24). H2 production has also been quantified in unicellular diazotrophs (12, 16, 17, 32), although the H2 measurements have rarely been performed in conjunction with rates of N2 fixation. However, recent H2 measurements of two N2-fixing unicellular cyanobacteria species reached a maximum of 1.38 nmol H2 μg chl a−1 h−1, with H2/N2 ratios ranging from 0.003 to 0.05, indicating an effective reassimilation of H2 can occur under certain conditions (34).H2 cycling in marine diazotrophs has important ecological implications both for the cell and for the marine H2 cycle. Surface waters of low-latitude oceans are typically 200 to 300% supersaturated in dissolved H2 with respect to atmospheric concentrations (25), implying a sustained localized production of H2. The source of the dissolved H2 is thought to be biological N2 fixation (7); however, the relative contributions of diverse diazotrophic communities and in situ controls on H2/N2 ratios are not well constrained. N2 fixation is performed by a suite of diazotrophs typically identified by their nitrogenase gene (nifH) sequences amplified directly from oceanic water samples (35). The importance of unicellular diazotrophs, including Crocosphaera spp., in marine N2 fixation has recently become widely recognized (36). Size-fractionated rates of N2 fixation indicate that in the oligotrophic ocean, <10-μm microorganisms, which include the unicellular cyanobacteria, make a substantial contribution to the daily N2 fixation (9, 18). Correlating the species-specific production of H2 with the activity and biomass of diazotrophs will help elucidate dissolved H2 cycling in the upper ocean.We examined the cycling of H2 in cultures of Crocosphaera watsonii strain WH8501, a marine unicellular diazotroph, and correlated it with other metabolic parameters, including N2 fixation measured via acetylene (C2H2) reduction, O2 production and consumption, and photosynthetic efficiency. Carbon monoxide (CO) was used as an inhibitor of intracellular H2 reassimilation to reveal the H2 cycling that can occur in conjunction with nitrogenase activity. H2 reassimilation by C. watsonii was shown to be very efficient in our laboratory experiments, which is considered to be a consequence of the temporal separation between daytime photosynthetic activity and nighttime N2 fixation. Therefore, the present study not only reveals the cell''s H2 cycle but also provides insight into the metabolism of nitrogenase in C. watsonii. 相似文献
996.
997.
Kula D Kalemba M Jurecka-Lubieniecka B Puch Z Kowalska M Tyszkiewicz T Kowal M Handkiewicz-Junak D 《Endokrynologia Polska》2010,61(5):486-489
Approximately 5% of differentiated thyroid cancers are hereditary. Hereditary non-medullary thyroid cancer may occur as a minor component of familial cancer syndromes (e.g. familial adenomatous polyposis) or as a primary feature (familial non-medullary thyroid cancer [FNMTC]). Among FNMTC, PTC is the most common. Although a hereditary predisposition to non-medullary thyroid cancer is well established, the susceptibility genes are poorly known. Up to now, by linkage analysis using microsatellite markers, several putative loci have been described - 1q21, 6q22, 8p23.1-p22, and 8q24; however, validation studies have been unsuccessful. In the present review we discuss the results of linkage analysis and the most recent results of genome wide association studies (GWAS) with high resolution SNP (single nucleotide polymorphism) arrays. 相似文献
998.
Michal Koblížek Jarmila Mlčoušková Zbigniew Kolber Jiří Kopecký 《Archives of microbiology》2010,192(1):41-49
Aerobic anoxygenic phototrophs (AAPs) are prokaryotic microorganisms capable of harvesting light using bacteriochlorophyll-based
reaction centres. Marine AAP communities are generally dominated by species belonging to the Roseobacter clade. For this reason, we used marine Roseobacter-related strain COL2P as a model organism to characterize its photosynthetic apparatus, level of pigmentation and expression
of photosynthetic complexes. This strain contained functional photosynthetic reaction centres with bacteriochlorophyll a and spheroidenone as the main light-harvesting pigments, but the expression of the photosynthetic apparatus was significantly
reduced when compared to truly photoautotrophic species. Moreover, the absence of peripheral light-harvesting complexes largely
reduced its light-harvesting capacity. The size of the photosynthetic unit was limited to 35.4 ± 1.0 BChl a molecules supplemented by the same number of spheroidenone molecules. The contribution of oxidative phosphorylation and photophosphorylation
was analysed by respiration and fluorometric measurements. Our results indicate that even with a such reduced photosynthetic
apparatus, photophosphorylation provides up to three times higher electron fluxes than aerobic respiration. These results
suggest that light-derived energy can provide a substantial fraction of COL2P metabolic needs. 相似文献
999.
1000.
Filek M Keskinen R Hartikainen H Szarejko I Janiak A Miszalski Z Golda A 《Journal of plant physiology》2008,165(8):833-844
The effect of selenium (Se) on rape (Brassica napus) seedlings subjected to cadmium (Cd) stress was studied in vitro by investigating plant growth and changes in fatty acid composition, activity of antioxidative enzymes and DNA methylation pattern. Physiological experiments were carried out on seedlings cultured for 2 weeks on Murashige-Scoog (MS) media with Cd concentrations of 0, 400 and 600 μM, and on corresponding media supplied with Se (2 μM). Exposure to increasing Cd concentrations reduced the fresh weight of the upper part (hypocotyls+cotyledons) of the seedlings more strongly than that of the root system, which was accompanied by higher Cd accumulation in these tissues. In the upper part, Cd exposure led to significant changes in the biochemical parameters: fatty acid unsaturation of plasmalemma decreased, the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPOX) diminished and that of ascorbate peroxidase (APX) increased. In contrast, the roots showed an increase in fatty acid unsaturation and in the activity of antioxidative enzymes. In both parts of rape seedlings H2O2 level and lipid peroxidation increased. Se addition to medium considerably reversed the Cd-induced decrease in fresh mass as well as the changes in lipid unsaturation and peroxidation. Se applied separately or in combination with Cd did not significantly affect the activity of antioxidative enzymes in the roots, but diminished it in the upper part. Moreover, the presence of Se in medium prevented changes in the DNA methylation pattern triggered in rape seedlings by high Cd concentrations. Two possible mechanisms for the action of Se were considered: (1) removal of Cd from metabolically active cellular sites, and (2) reduction of oxygen radicals. 相似文献