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991.
992.
Chater S Abdelmelek H Pequignot JM Sakly M Rhouma KB 《Electromagnetic biology and medicine》2006,25(3):135-144
This study investigated the effects of a static magnetic field (SMF) on hematopoiesis and biochemical parameters in female rats. Pregnant rats were exposed to SMF (128 mT-1 hour/day from day 6 to day 19 of pregnancy). At 25 degrees C, the exposure of rats 1 hour/day for 13 consecutive days to SMF induced an increase in hematocrit (Ht) level (+6%, p < 0.05), hemoglobin (Hb) concentration (+12%, p < 0.05) and LDH levels (67%, p < 0.05 ), suggesting an hypoxia-like state. Moreover, exposure to SMF increased blood glucose and decreased insulin release, leading to a diabetic-like state in pregnant rats. 相似文献
993.
Speers-Roesch B Robinson JW Ballantyne JS 《Journal of experimental zoology. Part A, Comparative experimental biology》2006,305(8):631-644
The metabolic organization of a holocephalan, the spotted ratfish (Hydrolagus colliei), was assessed using measurements of key enzymes of several metabolic pathways in four tissues and plasma concentrations of free amino acids (FAA) and non-esterified fatty acids (NEFA) to ascertain if the Holocephali differ metabolically from the Elasmobranchii since these groups diverged ca. 400 Mya. Activities of carnitine palmitoyl transferase indicate that fatty acid oxidation occurs in liver and kidney but not in heart or white muscle. This result mirrors the well-established absence of lipid oxidation in elasmobranch muscle, and more recent studies showing that elasmobranch kidney possesses a capacity for lipid oxidation. High activities in oxidative tissues of enzymes of ketone body metabolism, including D-beta-hydroxybutyrate dehydrogenase, indicate that, like elasmobranchs, ketone bodies are of central importance in spotted ratfish. Like many carnivorous fishes, enzyme activities demonstrate that amino acids are metabolically important, although the concentration of plasma FAA was relatively low. NEFA concentrations are lower than in teleosts, but higher than in most elasmobranchs and similar to that in some "primitive" ray-finned fishes. NEFA composition is comparable to other marine temperate fishes, including high levels of n-6 and especially n-3 polyunsaturated fatty acids. The metabolic organization of the spotted ratfish is similar to that of elasmobranchs: a reduced capacity for lipid oxidation in muscle, lower plasma NEFA levels, and an emphasis on ketone bodies as oxidative fuel. This metabolic strategy was likely present in the common chondrichthyan ancestor, and may be similar to the ancestral metabolic state of fishes. 相似文献
994.
Atze T. Das Ben Berkhout 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2010,365(1548):1965-1973
Replication of HIV-1 under selective pressure frequently results in the evolution of virus variants that replicate more efficiently under the applied conditions. For example, in patients on antiretroviral therapy, such evolution can result in variants that are resistant to the HIV-1 inhibitors, thus frustrating the therapy. On the other hand, virus evolution can help us to understand the molecular mechanisms that underlie HIV-1 replication. For example, evolution of a defective virus mutant can result in variants that overcome the introduced defect by restoration of the original sequence or by the introduction of additional mutations in the viral genome. Analysis of the evolution pathway can reveal the requirements of the element under study and help to understand its function. Analysis of the escape routes may generate new insight in the viral life cycle and result in the identification of unexpected biological mechanisms. We have developed in vitro HIV-1 evolution into a systematic research tool that allows the study of different aspects of the viral replication cycle. We will briefly review this method of forced virus evolution and provide several examples that illustrate the power of this approach. 相似文献
995.
996.
Gaye F. White Sonya M. Schermann Justin Bradley Andrew Roberts Nicholas P. Greene Ben C. Berks Andrew J. Thomson 《The Journal of biological chemistry》2010,285(4):2294-2301
The Tat system is used to transport folded proteins across the cytoplasmic membrane in bacteria and archaea and across the thylakoid membrane of plant chloroplasts. Multimers of the integral membrane TatA protein are thought to form the protein-conducting element of the Tat pathway. Nitroxide radicals were introduced at selected positions within the transmembrane helix of Escherichia coli TatA and used to probe the structure of detergent-solubilized TatA complexes by EPR spectroscopy. A comparison of spin label mobilities allowed classification of individual residues as buried within the TatA complex or exposed at the surface and suggested that residues Ile12 and Val14 are involved in interactions between helices. Analysis of inter-spin distances suggested that the transmembrane helices of TatA subunits are arranged as a single-walled ring containing a contact interface between Ile12 on one subunit and Val14 on an adjacent subunit. Experiments in which labeled and unlabeled TatA samples were mixed demonstrate that TatA subunits are exchanged between TatA complexes. This observation is consistent with the TatA dynamic polymerization model for the mechanism of Tat transport. 相似文献
997.
Ryan K. Swenerton Giselle M. Knudsen Mohammed Sajid Ben L. Kelly James H. McKerrow 《The Journal of biological chemistry》2010,285(41):31120-31129
Proteases are a ubiquitous group of enzymes that play key roles in the life cycle of parasites, in the host-parasite relationship, and in the pathogenesis of parasitic diseases. Furthermore, proteases are druggable targets for the development of new anti-parasitic therapy. The subtilisin protease (SUB; Clan SB, family S8) of Leishmania donovani was cloned and found to possess a unique catalytic triad. This gene was then deleted by gene knock-out, which resulted in reduced ability by the parasite to undergo promastigote to amastigote differentiation in vitro. Electron microscopy of SUB knock-out amastigotes revealed abnormal membrane structures, retained flagella, and increased binucleation. SUB-deficient Leishmania displayed reduced virulence in both hamster and murine infection models. Histology of spleens from SUB knock-out-infected hamsters revealed the absence of psammoma body calcifications indicative of the granulomatous lesions that occur during Leishmania infection. To delineate the specific role of SUB in parasite physiology, two-dimensional gel electrophoresis was carried out on SUB−/− versus wild-type parasites. SUB knock-out parasites showed altered regulation of the terminal peroxidases of the trypanothione reductase system. Leishmania and other trypanosomatids lack glutathione reductase, and therefore rely on the novel trypanothione reductase system to detoxify reactive oxygen intermediates and to maintain redox homeostasis. The predominant tryparedoxin peroxidases were decreased in SUB−/− parasites, and higher molecular weight isoforms were present, indicating altered processing. In addition, knock-out parasites showed increased sensitivity to hydroperoxide. These data suggest that subtilisin is the maturase for tryparedoxin peroxidases and is necessary for full virulence. 相似文献
998.
Ming-xiu Hao Li-sheng Jiang Ning-yuan Fang Jun Pu Liu-hua Hu Ling-Hong Shen Wei Song Ben He 《Journal of lipid research》2010,51(8):2181-2190
The endocannabinoid system has recently been attracted interest for its anti-inflammatory and anti-oxidative properties. In this study, we investigated the role of the endocannabinoid system in regulating the oxidized low-density lipoprotein (oxLDL)-induced inflammatory response in macrophages. RAW264.7 mouse macrophages and peritoneal macrophages isolated from Sprague-Dawley (SD) rats were exposed to oxLDL with or without the synthetic cannabinoid WIN55,212-2. To assess the inflammatory response, reactive oxygen species (ROS) and tumor necrosis factor alpha (TNF- α) levels were determined, and activation of the mitogen-activated protein kinase (MAPK) and nuclear factor (NF)-kappa B signaling pathways were assessed. We observed that: i) oxLDL strongly induced ROS generation and TNF- α secretion in murine macrophages; ii) oxLDL-induced TNF- α and ROS levels could be lowered considerably by WIN55,212-2 via inhibition of MAPK (ERK1/2) signaling and NF-kappa B activity; and iii) the effects of WIN55212-2 were attenuated by the selective CB2 receptor antagonist AM630. These results demonstrate the involvement of the endocannabinoid system in regulating the oxLDL-induced inflammatory response in macrophages, and indicate that the CB2 receptor may offer a novel pharmaceutical target for treating atherosclerosis. 相似文献
999.
1000.
Bettaieb J Toumi A Leffondre K Ben Alaya N Boukthir A Chlif S Hajem S Ben Salah A 《Archives de l'Institut Pasteur de Tunis》2010,87(1-2):25-33
The influence of thermal stress on health is proved. In the light of the current climate change this relationship should be extensively investigated. This study aims to describe the relationship between temperature and total mortality in the city of Tunis over a period of three years, from 2005 to 2007 using time series analysis. The form of the relation (crude and adjusted) between mortality and temperatures was investigated using Poisson generalized additive models (GAM). Confounders included in the models were pollutant, trend, calendar month, day of the week, the period of Ramadan, and holidays. The adjusted relationship between mortality and temperature was "V" shaped with a steeper slope for low temperatures than for high temperatures. The impact of heat on mortality will be further analyzed to refine our findings and to contribute to the elaboration of guidelines for preventive strategies. 相似文献