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991.
Stephane C. Lefebvre Ina Benner Jonathon H. Stillman Alexander E. Parker Michelle K. Drake Pascale E. Rossignol Kristine M. Okimura Tomoko Komada Edward J. Carpenter 《Global Change Biology》2012,18(2):493-503
Coccolithophores are unicellular phytoplankton that produce calcium carbonate coccoliths as an exoskeleton. Emiliania huxleyi, the most abundant coccolithophore in the world's ocean, plays a major role in the global carbon cycle by regulating the exchange of CO2 across the ocean‐atmosphere interface through photosynthesis and calcium carbonate precipitation. As CO2 concentration is rising in the atmosphere, the ocean is acidifying and ammonium (NH4+) concentration of future ocean water is expected to rise. The latter is attributed to increasing anthropogenic nitrogen (N) deposition, increasing rates of cyanobacterial N2 fixation due to warmer and more stratified oceans, and decreased rates of nitrification due to ocean acidification. Thus, future global climate change will cause oceanic phytoplankton to experience changes in multiple environmental parameters including CO2, pH, temperature and nitrogen source. This study reports on the combined effect of elevated pCO2 and increased NH4+ to nitrate (NO3?) ratio (NH4+/NO3?) on E. huxleyi, maintained in continuous cultures for more than 200 generations under two pCO2 levels and two different N sources. Herein, we show that NH4+ assimilation under N‐replete conditions depresses calcification at both low and high pCO2, alters coccolith morphology, and increases primary production. We observed that N source and pCO2 synergistically drive growth rates, cell size, and the ratio of inorganic to organic carbon. These responses to N source suggest that, compared to increasing CO2 alone, a greater disruption of the organic carbon pump could be expected in response to the combined effect of increased NH4+/NO3? ratio and CO2 level in the future acidified ocean. Additional experiments conducted under lower nutrient conditions are needed prior to extrapolating our findings to the global oceans. Nonetheless, our results emphasize the need to assess combined effects of multiple environmental parameters on phytoplankton biology to develop accurate predictions of phytoplankton responses to ocean acidification. 相似文献
992.
Gerbault P Liebert A Itan Y Powell A Currat M Burger J Swallow DM Thomas MG 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2011,366(1566):863-877
Niche construction is the process by which organisms construct important components of their local environment in ways that introduce novel selection pressures. Lactase persistence is one of the clearest examples of niche construction in humans. Lactase is the enzyme responsible for the digestion of the milk sugar lactose and its production decreases after the weaning phase in most mammals, including most humans. Some humans, however, continue to produce lactase throughout adulthood, a trait known as lactase persistence. In European populations, a single mutation (-13910*T) explains the distribution of the phenotype, whereas several mutations are associated with it in Africa and the Middle East. Current estimates for the age of lactase persistence-associated alleles bracket those for the origins of animal domestication and the culturally transmitted practice of dairying. We report new data on the distribution of -13910*T and summarize genetic studies on the diversity of lactase persistence worldwide. We review relevant archaeological data and describe three simulation studies that have shed light on the evolution of this trait in Europe. These studies illustrate how genetic and archaeological information can be integrated to bring new insights to the origins and spread of lactase persistence. Finally, we discuss possible improvements to these models. 相似文献
993.
Charbonnier LM van Duivenvoorde LM Apparailly F Cantos C Han WG Noël D Duperray C Huizinga TW Toes RE Jorgensen C Louis-Plence P 《Journal of immunology (Baltimore, Md. : 1950)》2006,177(6):3806-3813
Dendritic cells (DCs) are specialized APCs with an important role in the initiation and regulation of immune responses. Immature DCs (iDCs) reportedly mediate tolerance in the absence of maturation/inflammatory stimuli, presumably by the induction of regulatory T cells. In this study, we show for the first time that repetitive iDC injections trigger the expansion of a novel regulatory population with high immunomodulatory properties, able to protect mice from collagen-induced arthritis. These regulatory T cells are characterized by the expression of the CD49b molecule and correspond to a CD4+ alpha-galactosylceramide/CD1d-nonrestricted T cell population producing IL-10. Adoptive transfer of < 10(5) TCRbeta+ CD49b+ cells isolated from the liver of iDCs-vaccinated mice, conferred a complete protection against arthritis. This protection was associated with an attenuation of the B and T cell response associated with a local secretion of IL-10. Thus, together these data demonstrate that iDCs can expand and activate a novel regulatory population of CD49b+ T cells, with high immunosuppressive potential able to mediate protection against a systemic autoimmune disease. 相似文献
994.
A large variety of RNA-based mechanisms have been uncovered in all living organisms to regulate gene expression in response to internal and external changes, and to rapidly adapt cell growth in response to these signals. In bacteria, structural elements in the 5' leader regions of mRNAs have direct effects on translation initiation of the downstream coding sequences. The docking and unfolding of these mRNAs on the 30S subunit are critical steps in the initiation process directly modulating and timing translation. Structural elements can also undergo conformational changes in response to environmental cues (i.e., temperature sensors) or upon binding of a variety of trans-acting factors, such as metabolites, non-coding RNAs or regulatory proteins. These RNA switches can temporally regulate translation, leading either to repression or to activation of protein synthesis. 相似文献
995.
Fortier M Wang SP Mauriège P Semache M Mfuma L Li H Levy E Richard D Mitchell GA 《American journal of physiology. Endocrinology and metabolism》2004,287(2):E282-E288
In white adipose tissue, lipolysis can occur by hormone-sensitive lipase (HSL)-dependent or HSL-independent pathways. To study HSL-independent lipolysis, we placed HSL-deficient mice in conditions of increased fatty acid flux: beta-adrenergic stimulation, fasting, and dietary fat loading. Intraperitoneal administration of the beta(3)-adrenergic agonist CL-316243 caused a greater increase in nonesterified fatty acid level in controls (0.33 +/- 0.05 mmol/l) than in HSL(-/-) mice (0.12 +/- 0.01 mmol/l, P < 0.01). Similarly, in isolated adipocytes, lipolytic response to CL-316243 was greatly reduced in HSL(-/-) mice compared with controls. Fasting for 相似文献
996.
Binding of ATP to heat shock protein 90: evidence for an ATP-binding site in the C-terminal domain. 总被引:4,自引:0,他引:4
Cyrille Garnier Daniel Lafitte Philipp O Tsvetkov Pascale Barbier Jocelyne Leclerc-Devin Jean-Marc Millot Claudette Briand Alexander A Makarov Maria G Catelli Vincent Peyrot 《The Journal of biological chemistry》2002,277(14):12208-12214
The presence of a nucleotide binding site on hsp90 was very controversial until x-ray structure of the hsp90 N-terminal domain, showing a nonconventional nucleotide binding site, appeared. A recent study suggested that the hsp90 C-terminal domain also binds ATP (Marcu, M. G., Chadli, A., Bouhouche, I., Catelli, M. G., and Neckers, L. M. (2000) J. Biol. Chem. 275, 37181-37186). In this paper, the interactions of ATP with native hsp90 and its recombinant N-terminal (positions 1-221) and C-terminal (positions 446-728) domains were studied by isothermal titration calorimetry, scanning differential calorimetry, and fluorescence spectroscopy. Results clearly demonstrate that hsp90 possesses a second ATP-binding site located on the C-terminal part of the protein. The association constant between this domain of hsp90 and ATP-Mg and a comparison with the binding constant on the full-length protein are reported for the first time. Secondary structure prediction revealed motifs compatible with a Rossmann fold in the C-terminal part of hsp90. It is proposed that this potential Rossmann fold may constitute the C-terminal ATP-binding site. This work also suggests allosteric interaction between N- and C-terminal domains of hsp90. 相似文献
997.
Fine needle aspiration cytology of thyroid gland diseases 总被引:3,自引:0,他引:3
From 1982 to 1987, 2,433 lesions of the thyroid gland in 1,796 patients were examined by fine needle aspiration (FNA). Cytopathology classified 66.91% of the aspirates as benign, 10.76% as thyroiditis, 4.89% as suspected (unspecified) neoplasia, 1.31% as positive for malignancy and 16.11% (392) as unsatisfactory. The histologic diagnoses in 257 cases were compared with cytologic diagnoses to determine the accuracy of FNA cytology of thyroid lesions, yielding a sensitivity of 71.43%, a specificity of 100% and an accuracy of 95.09%. This data strongly supports thyroid FNA as an important preoperative diagnostic tool. Follicular carcinomas were difficult to cytologically differentiate from nonmalignant follicular neoplasms, and papillary thyroid carcinomas less than 2 cm in diameter in elderly patients were frequently misdiagnosed or diagnosed only as "suspect lesion." 相似文献
998.
Fluxes of dissolved inorganic carbon and oxygen at the water-sediment interface were measured at eight coral reef stations (Indian Ocean) in summer and winter. The dark fluxes provided the community respiratory quotient (CRQ = dissolved inorganic carbon release / oxygen uptake) and the diurnal fluxes corrected from the dark fluxes gave the community photosynthetic quotient (CPQ = oxygen gross release / dissolved inorganic carbon gross uptake). The CRQ and the winter CPQ were not significantly different from 1. Summer CPQ (0.79; SD 0.02) was significantly lower than 1 due to the combined effect of the daily evolution of the community respiration and the discrepancy between the daily evolution in community oxygen respiration and community carbon respiration. These results highlight the importance of measuring simultaneously the benthic community production and respiration for long term integrated data sets, instead of the traditional daily or seasonal budget calculations from limited measures of community respiration. To cite this article: D. Taddei et al., C. R. Biologies 331 (2008). 相似文献
999.
Andrée-Anne Clément Eléonor Riesco Sébastien Tessier Michel Lacaille Francine Pérusse Mélanie Coté Jean-Pierre Després John Weisnagel Jean Doré Denis R. Joanisse Pascale Mauriège 《Journal of physiology and biochemistry》2018,74(4):591-601
The contribution of adiposopathy to glucose-insulin homeostasis remains unclear. This longitudinal study examined the potential relationship between the adiponectin/leptin ratio (A/L, a marker of adiposopathy) and insulin resistance (IR: homeostasis model assessment (HOMA)), insulin sensitivity (IS: Matsuda), and insulin response to an oral glucose tolerance test before and after a 16-week walking program, in 29 physically inactive pre- and postmenopausal women with obesity (BMI, 29–35 kg/m2; age, 47–54 years). Anthropometry, body composition, VO2max, and fasting lipid-lipoprotein and inflammatory profiles were assessed. A/L was unchanged after training (p =?0.15), despite decreased leptin levels (p <?0.05). While the Matsuda index tended to increase (p =?0.07), HOMA decreased (p <?0.05) and fasting insulin was reduced (p <?0.01) but insulin area under the curve (AUC) remained unchanged (p =?0.18) after training. Body fatness and VO2max were improved (p <?0.05) while triacylglycerols increased and HDL-CHOL levels decreased after training (p <?0.05). At baseline, A/L was positively associated with VO2max, HDL-CHOL levels, and Matsuda (0.37?< ρ <?0.56; p <?0.05) but negatively with body fatness, HOMA, insulin AUC, IL-6, and hs-CRP levels (??0.41?< ρ <???0.66; p <?0.05). After training, associations with fitness, HOMA, and inflammation were lost. Multiple regression analysis revealed A/L as an independent predictor of IR and IS, before training (partial R2 =?0.10 and 0.22), although A/L did not predict the insulin AUC pre- or post-intervention. A significant correlation was found between training-induced changes to A/L and IS (r =?0.38; p <?0.05) but not with IR or insulin AUC. Although changes in the A/L ratio could not explain improvements to glucose-insulin homeostasis indices following training, a relationship with insulin sensitivity was revealed in healthy women with obesity. 相似文献
1000.
Marianne Leger Anne Quiedeville Eleni Paizanis Sharuja Natkunarajah Thomas Freret Michel Boulouard Pascale Schumann-Bard 《PloS one》2012,7(10)
Although environmental enrichment is well known to improve learning and memory in rodents, the underlying neuronal networks'' plasticity remains poorly described. Modifications of the brain activation pattern by enriched condition (EC), especially in the frontal cortex and the baso-lateral amygdala, have been reported during an aversive memory task in rodents. The aims of our study were to examine 1) whether EC modulates episodic-like memory in an object recognition task and 2) whether EC modulates the task-induced neuronal networks. To this end, adult male mice were housed either in standard condition (SC) or in EC for three weeks before behavioral experiments (n = 12/group). Memory performances were examined in an object recognition task performed in a Y-maze with a 2-hour or 24-hour delay between presentation and test (inter-session intervals, ISI). To characterize the mechanisms underlying the promnesiant effect of EC, the brain activation profile was assessed after either the presentation or the test sessions using immunohistochemical techniques with c-Fos as a neuronal activation marker. EC did not modulate memory performances after a 2 h-ISI, but extended object recognition memory to a 24 h-ISI. In contrast, SC mice did not discriminate the novel object at this ISI. Compared to SC mice, no activation related to the presentation session was found in selected brain regions of EC mice (in particular, no effect was found in the hippocampus and the perirhinal cortex and a reduced activation was found in the baso-lateral amygdala). On the other hand, an activation of the hippocampus and the infralimbic cortex was observed after the test session for EC, but not SC mice. These results suggest that the persistence of object recognition memory in EC could be related to a reorganization of neuronal networks occurring as early as the memory encoding. 相似文献