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排序方式: 共有139条查询结果,搜索用时 500 毫秒
131.
Bacteria with greatly elevated mutation rates (mutators) are frequently found in natural and laboratory populations, and are often associated with clinical infections. Although mutators may increase adaptability to novel environmental conditions, they are also prone to the accumulation of deleterious mutations. The long-term maintenance of high bacterial mutation rates is therefore likely to be driven by rapidly changing selection pressures, in addition to the possible slow transition rate by point mutation from mutators to non-mutators. One of the most likely causes of rapidly changing selection pressures is antagonistic coevolution with parasites. Here we show whether coevolution with viral parasites could drive the evolution of bacterial mutation rates in laboratory populations of the bacterium Pseudomonas fluorescens. After fewer than 200 bacterial generations, 25% of the populations coevolving with phages had evolved 10- to 100-fold increases in mutation rates owing to mutations in mismatch-repair genes; no populations evolving in the absence of phages showed any significant change in mutation rate. Furthermore, mutator populations had a higher probability of driving their phage populations extinct, strongly suggesting that mutators have an advantage against phages in the coevolutionary arms race. Given their ubiquity, bacteriophages may play an important role in the evolution of bacterial mutation rates. 相似文献
132.
Money demand functions have long been known to be frequently subject to structural change. Since their use for optimal monetary policy design is basically a forecasting exercise, it is crucial to analyse the effect of time instability on the quality of their forecasts. We discuss in this paper whether instability of demand for money functions precludes their use for policy experiments, analysing a 1963–84 sample for the UK which has been widely used in the literature. © 1998 John Wiley & Sons, Ltd. 相似文献
133.
Roman Goetzke Antonio Sechi Laura De Laporte Sabine Neuss Wolfgang Wagner 《Cellular and molecular life sciences : CMLS》2018,75(18):3297-3312
Mechanical stimulation affects growth and differentiation of stem cells. This may be used to guide lineage-specific cell fate decisions and therefore opens fascinating opportunities for stem cell biology and regenerative medicine. Several studies demonstrated functional and molecular effects of mechanical stimulation but on first sight these results often appear to be inconsistent. Comparison of such studies is hampered by a multitude of relevant parameters that act in concert. There are notorious differences between species, cell types, and culture conditions. Furthermore, the utilized culture substrates have complex features, such as surface chemistry, elasticity, and topography. Cell culture substrates can vary from simple, flat materials to complex 3D scaffolds. Last but not least, mechanical forces can be applied with different frequency, amplitude, and strength. It is therefore a prerequisite to take all these parameters into consideration when ascribing their specific functional relevance—and to only modulate one parameter at the time if the relevance of this parameter is addressed. Such research questions can only be investigated by interdisciplinary cooperation. In this review, we focus particularly on mesenchymal stem cells and pluripotent stem cells to discuss relevant parameters that contribute to the kaleidoscope of mechanical stimulation of stem cells. 相似文献
134.
Mireia Pérez-Verdaguer Jesusa Capera María Ortego-Domínguez Joanna Bielanska Núria Comes Rafael J. Montoro Marta Camps Antonio Felipe 《Cellular and molecular life sciences : CMLS》2018,75(21):4059-4075
The voltage-dependent potassium channel Kv1.3 participates in peripheral insulin sensitivity. Genetic ablation of Kv1.3 triggers resistance to diet-induced weight gain, thereby pointing to this protein as a pharmacological target for obesity and associated type II diabetes. However, this role is under intense debate because Kv1.3 expression in adipose tissue raises controversy. We demonstrated that Kv1.3 is expressed in white adipose tissue from humans and rodents. Moreover, other channels, such as Kv1.1, Kv1.2, Kv1.4 and especially Kv1.5, from the same Shaker family are also present. Although elevated insulin levels and adipogenesis remodel the Kv phenotype, which could lead to multiple heteromeric complexes, Kv1.3 markedly participates in the insulin-dependent regulation of glucose uptake in mature adipocytes. Adipocyte differentiation increased the expression of Kv1.3, which is targeted to caveolae by molecular interactions with caveolin 1. Using a caveolin 1-deficient 3T3-L1 adipocyte cell line, we demonstrated that the localization of Kv1.3 in caveolar raft structures is important for proper insulin signaling. Insulin-dependent phosphorylation of the channel occurs at the onset of insulin-mediated signaling. However, when Kv1.3 was spatially outside of these lipid microdomains, impaired phosphorylation was exhibited. Our data shed light on the putative role of Kv1.3 in weight gain and insulin-dependent responses contributing to knowledge about adipocyte physiology. 相似文献
135.
Jose Maria Aguilar-Camacho Jose Luis Carballo Jose Antonio Cruz-Barraza 《Journal of Natural History》2018,52(19-20):1311-1332
Two new species of Tedania (Porifera: Demospongiae: Poecilosclerida) are described from the Mexican Pacific. Tedania (Tedania) tropicalis sp. nov. is an encrusting to massive sponge having ectosomal tylotes with microspined heads, choanosomal styles and onychaetes. Tedania (Tedania) fulvum sp. nov. is a thinly encrusting sponge having ectosomal tylotes with smooth heads, choanosomal styles and onychaetes. Tables for all the Tedania (subgenera Tedania and Tedaniopsis) and Trachytedania species described worldwide are included. We suggest that species of Tedania and Trachytedania bearing ectosomal diactinal spicules (excluding Tedania (Stylotedania)) can be separated in two main groups: those having choanosomal monactinal spicules and those with choanosomal diactinal spicules.
www.zoobank.org/urn:lsid:zoobank.org:pub:5B212DC3-3827-44D5-8E63-3E652BCB29E6 相似文献
136.
Federica Corallini Paola Secchiero Antonio Paolo Beltrami Daniela Cesselli Elisa Puppato Roberto Ferrari Carlo Alberto Beltrami Giorgio Zauli 《Cellular and molecular life sciences : CMLS》2010,67(8):1307-1314
The number of circulating mesenchymal stem cells (MSC), analyzed after acute myocardial infarction (AMI), was lower in AMI
patients who developed heart failure (HF) in the follow-up. Conversely, the circulating levels of tumor necrosis factor (TNF)-α,
and osteoprotegerin (OPG) were higher in AMI patients who developed HF with respect to the patients who did not develop HF.
In vitro exposure to TNF-α enhanced the migration of MSC in response to TNF-related apoptosis-inducing ligand (TRAIL) and
significantly increased the release of OPG by endothelial cells. On the contrary, OPG dose-dependently neutralized the in
vitro pro-migratory activity of TRAIL. Thus, TNF-α exhibits opposite effects on MSC migration driven by TRAIL: it is capable
of potentiating MSC migration as well as of inhibiting MSC migration as an indirect consequence of OPG induction, which might
result in a suboptimal recruitment of circulating MSC after AMI in those patients who develop HF in the follow-up. 相似文献
137.
Donadi EA Castelli EC Arnaiz-Villena A Roger M Rey D Moreau P 《Cellular and molecular life sciences : CMLS》2011,68(3):369-395
The HLA-G gene displays several peculiarities that are distinct from those of classical HLA class I genes. The unique structure of
the HLA-G molecule permits a restricted peptide presentation and allows the modulation of the cells of the immune system.
Although polymorphic sites may potentially influence all biological functions of HLA-G, those present at the promoter and
3′ untranslated regions have been particularly studied in experimental and pathological conditions. The relatively low polymorphism
observed in the MHC-G coding region both in humans and apes may represent a strong selective pressure for invariance, whereas,
in regulatory regions several lines of evidence support the role of balancing selection. Since HLA-G has immunomodulatory
properties, the understanding of gene regulation and the role of polymorphic sites on gene function may permit an individualized
approach for the future use of HLA-G for therapeutic purposes. 相似文献
138.
Hashibe M McKay JD Curado MP Oliveira JC Koifman S Koifman R Zaridze D Shangina O Wünsch-Filho V Eluf-Neto J Levi JE Matos E Lagiou P Lagiou A Benhamou S Bouchardy C Szeszenia-Dabrowska N Menezes A Dall'Agnol MM Merletti F Richiardi L Fernandez L Lence J Talamini R Barzan L Mates D Mates IN Kjaerheim K Macfarlane GJ Macfarlane TV Simonato L Canova C Holcátová I Agudo A Castellsagué X Lowry R Janout V Kollarova H Conway DI McKinney PA Znaor A Fabianova E Bencko V Lissowska J Chabrier A Hung RJ 《Nature genetics》2008,40(6):707-709
Alcohol is an important risk factor for upper aerodigestive cancers and is principally metabolized by alcohol dehydrogenase (ADH) enzymes. We have investigated six ADH genetic variants in over 3,800 aerodigestive cancer cases and 5,200 controls from three individual studies. Gene variants rs1229984 (ADH1B) and rs1573496 (ADH7) were significantly protective against aerodigestive cancer in each individual study and overall (P = 10(-10) and 10(-9), respectively). These effects became more apparent with increasing alcohol consumption (P for trend = 0.0002 and 0.065, respectively). Both gene effects were independent of each other, implying that multiple ADH genes may be involved in upper aerodigestive cancer etiology. 相似文献
139.
Moreno-Loshuertos R Acín-Pérez R Fernández-Silva P Movilla N Pérez-Martos A Rodriguez de Cordoba S Gallardo ME Enríquez JA 《Nature genetics》2006,38(11):1261-1268
Common mitochondrial DNA (mtDNA) haplotypes in humans and mice have been associated with various phenotypes, including learning performance and disease penetrance. Notably, no influence of mtDNA haplotype in cell respiration has been demonstrated. Here, using cell lines carrying four different common mouse mtDNA haplotypes in an identical nuclear background, we show that the similar level of respiration among the cell lines is only apparent and is a consequence of compensatory mechanisms triggered by different production of reactive oxygen species. We observe that the respiration capacity per molecule of mtDNA in cells with the NIH3T3 or NZB mtDNA is lower than in those with the C57BL/6J, CBA/J or BALB/cJ mtDNA. In addition, we have determined the genetic element underlying these differences. Our data provide insight into the molecular basis of the complex phenotypes associated with common mtDNA variants and anticipate a relevant contribution of mtDNA single nucleotide polymorphisms to phenotypic variability in humans. 相似文献