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51.
Paradis E 《Proceedings. Biological sciences / The Royal Society》2003,270(1532):2499-2505
The estimation of diversification rates using phylogenetic data has attracted a lot of attention in the past decade. In this context, the analysis of incomplete phylogenies (e.g. phylogenies resolved at the family level but unresolved at the species level) has remained difficult. I present here a likelihood-based method to combine partly resolved phylogenies with taxonomic (species-richness) data to estimate speciation and extinction rates. This method is based on fitting a birth-and-death model to both phylogenetic and taxonomic data. Some examples of the method are presented with data on birds and on mammals. The method is compared with existing approaches that deal with incomplete phylogenies. Some applications and generalizations of the approach introduced in this paper are further discussed. 相似文献
52.
The lack of a reliable and innocuous mark-recapture method has limited studies that would provide essential information for the management of commercial sea cucumbers. Tagging sea cucumbers is notoriously difficult because of their plastic nature and autolysis capacities. The markers that have so far been tested, mainly on or through the body wall, were either lost rapidly or had major drawbacks (e.g. suitable only for batch identification, requiring complex analysis, causing infections, necrosis, behavioural changes and mortality). The present study explored the efficacy of passive integrated transponder (PIT) tags for individually marking sea cucumbers by assessing retention rates and long-term side effects of tags inserted in previously unstudied tissues/organs. Individuals of the species Cucumaria frondosa were tagged in the body wall, aquapharyngeal bulb and at the base of the oral tentacles. They were monitored closely for evidence of stress, infection, change in feeding and spawning behaviour and tag retention rate. Implanting the tag in an oral tentacle to reach the hydrovascular system of the aquapharyngeal bulb achieved the best retention rates in full-size individuals: from a maximum of 92% after 30 days to 68% at the end of the experimental period (300 days). Efficacy was lower in smaller individuals (84% after 30 d and 42% after 300 d). Following a slight increase in cloacal movements for 15 h post tagging, no side effect was noted in sea cucumbers tagged in the aquapharyngeal bulb via the tentacles. Feeding and spawning behaviours were not affected and no signs of infections or abnormal cell development in the vicinity of the tags were observed. This study indicates that marking sea cucumbers with 8.2 mm long PIT tags implanted via the oral tentacle is an effective technique, yielding relatively high retention rates over long periods without any detectable physiological or behavioural effects. 相似文献
53.
Lithocholic acid decreases expression of bile salt export pump through farnesoid X receptor antagonist activity 总被引:6,自引:0,他引:6
Yu J Lo JL Huang L Zhao A Metzger E Adams A Meinke PT Wright SD Cui J 《The Journal of biological chemistry》2002,277(35):31441-31447
Bile salt export pump (BSEP) is a major bile acid transporter in the liver. Mutations in BSEP result in progressive intrahepatic cholestasis, a severe liver disease that impairs bile flow and causes irreversible liver damage. BSEP is a target for inhibition and down-regulation by drugs and abnormal bile salt metabolites, and such inhibition and down-regulation may result in bile acid retention and intrahepatic cholestasis. In this study, we quantitatively analyzed the regulation of BSEP expression by FXR ligands in primary human hepatocytes and HepG2 cells. We demonstrate that BSEP expression is dramatically regulated by ligands of the nuclear receptor farnesoid X receptor (FXR). Both the endogenous FXR agonist chenodeoxycholate (CDCA) and synthetic FXR ligand GW4064 effectively increased BSEP mRNA in both cell types. This up-regulation was readily detectable at as early as 3 h, and the ligand potency for BSEP regulation correlates with the intrinsic activity on FXR. These results suggest BSEP as a direct target of FXR and support the recent report that the BSEP promoter is transactivated by FXR. In contrast to CDCA and GW4064, lithocholate (LCA), a hydrophobic bile acid and a potent inducer of cholestasis, strongly decreased BSEP expression. Previous studies did not identify LCA as an FXR antagonist ligand in cells, but we show here that LCA is an FXR antagonist with partial agonist activity in cells. In an in vitro co-activator association assay, LCA decreased CDCA- and GW4064-induced FXR activation with an IC(50) of 1 microm. In HepG2 cells, LCA also effectively antagonized GW4064-enhanced FXR transactivation. These data suggest that the toxic and cholestatic effect of LCA in animals may result from its down-regulation of BSEP through FXR. Taken together, these observations indicate that FXR plays an important role in BSEP gene expression and that FXR ligands may be potential therapeutic drugs for intrahepatic cholestasis. 相似文献
54.
Farnesyl pyrophosphate (FPP) is a common substrate for a variety of prenyltransferases for synthesizing isoprenoid compounds. In this study, (2E,6E)-8-O-(N-methyl-2-aminobenzoyl)-3,7-dimethyl-2,6-octandien-1-pyrophosphate (MANT-O-GPP), a fluorescent analog of FPP, was synthesized and demonstrated as a satisfactory substrate for Escherichia coli undecaprenyl pyrophosphate synthase (UPPS) with a Km of 1.5 μM and a kcat of 1.2 s−1 based on [14C]IPP consumption. Interesting, we found that its emission fluorescence intensity at 420 nm increased remarkably during chain elongation, thereby useful for real-time monitoring kinetics of UPPS to yield a Km of 1.1 μM and a kcat of 1.0 s−1, consistent with those measured using radiolabeled substrate. Using this assay, the IC50 of a known UPPS inhibitor farnesyl thiopyrophosphate (FsPP) was confirmed. Our studies provide a convenient and environmentally friendly alternative for kinetics and inhibition studies on UPPS drug target. 相似文献
55.
56.
Mitochondrial Group II Introns, Cytochrome c Oxidase, and Senescence in Podospora anserina 下载免费PDF全文
Odile Begel Jocelyne Boulay Beatrice Albert Eric Dufour Annie Sainsard-Chanet 《Molecular and cellular biology》1999,19(6):4093-4100
Podospora anserina is a filamentous fungus with a limited life span. It expresses a degenerative syndrome called senescence, which is always associated with the accumulation of circular molecules (senDNAs) containing specific regions of the mitochondrial chromosome. A mobile group II intron (alpha) has been thought to play a prominent role in this syndrome. Intron alpha is the first intron of the cytochrome c oxidase subunit I gene (COX1). Mitochondrial mutants that escape the senescence process are missing this intron, as well as the first exon of the COX1 gene. We describe here the first mutant of P. anserina that has the alpha sequence precisely deleted and whose cytochrome c oxidase activity is identical to that of wild-type cells. The integration site of the intron is slightly modified, and this change prevents efficient homing of intron alpha. We show here that this mutant displays a senescence syndrome similar to that of the wild type and that its life span is increased about twofold. The introduction of a related group II intron into the mitochondrial genome of the mutant does not restore the wild-type life span. These data clearly demonstrate that intron alpha is not the specific senescence factor but rather an accelerator or amplifier of the senescence process. They emphasize the role that intron alpha plays in the instability of the mitochondrial chromosome and the link between this instability and longevity. Our results strongly support the idea that in Podospora, "immortality" can be acquired not by the absence of intron alpha but rather by the lack of active cytochrome c oxidase. 相似文献
57.
S Le Vu A Velter L Meyer G Peytavin J Guinard J Pillonel F Barin C Semaille 《PloS one》2012,7(6):e39872
BACKGROUND: Population-based estimates of HIV incidence in France have revealed that men who have sex with men (MSM) are the most affected population and contribute to nearly half of new infections each year. We sought to estimate HIV incidence among sexually active MSM in Paris gay community social venues. METHODOLOGY/ PRINCIPAL FINDINGS: A cross-sectional survey was conducted in 2009 in a sample of commercial venues such as bars, saunas and backrooms. We collected a behavioural questionnaire and blood sample. Specimens were tested for HIV infection and positive specimens then tested for recent infection by the enzyme immunoassay for recent HIV-1 infection (EIA-RI). We assessed the presence of antiretroviral therapy among infected individuals to rule out treated patients in the algorithm that determined recent infection. Biomarker-based cross-sectional incidence estimates were calculated. We enrolled 886 MSM participants among which 157 (18%) tested HIV positive. In positive individuals who knew they were infected, 75% of EIA-RI positive results were due to ART. Of 157 HIV positive specimens, 15 were deemed to be recently infected. The overall HIV incidence was estimated at 3.8% person-years (py) [95%CI: 1.5-6.2]. Although differences were not significant, incidence was estimated to be 3.5% py [0.1-6.1] in men having had a negative HIV test in previous year and 4.8% py [0.1-10.6] in men having had their last HIV test more than one year before the survey, or never tested. Incidence was estimated at 4.1% py [0-8.3] in men under 35 years and 2.5% py [0-5.4] in older men. CONCLUSIONS/ SIGNIFICANCE: This is the first community-based survey to estimate HIV incidence among MSM in France. It includes ART detection and reveals a high level of HIV transmission in sexually active individuals, despite a high uptake of HIV testing. These data call for effective prevention programs targeting MSM engaged in high-risk behaviours. 相似文献
58.
Giraud A Dicristofaro J De Micco C Lejeune PJ Barbaria J Mallet B 《Biochemical and biophysical research communications》2005,338(2):1000-1004
The prothyroid hormone, thyroglobulin (Tg), is stored at high concentrations in the thyroid follicular lumen as a soluble 19S homo-dimer and as heavier soluble (27S and 37S) and insoluble (Tgm) forms. Follicular degradation of Tg may contribute to maintaining Tg concentrations compatible with follicle integrity. Here, we report on the presence of a plasminogen-like protein in the follicular lumen of normal human thyroids and its synthesis and apical secretion by cultured epithelial thyroid cells. Since all the main luminal forms of Tg are cleaved by this plasminogen-like protein, we suggest that it contributes to Tg degradation in the follicular lumen. 相似文献
59.
Ormenese S de Almeida Engler J De Groodt R De Veylder L Inzé D Jacqmard A 《Annals of botany》2004,93(5):575-580
BACKGROUND AND AIMS: Kip-related-proteins (KRPs), negative regulators of cell division, have recently been discovered in plants but their in planta function is as yet unclear. In this study the spatial expression of all seven KRP genes in shoot apices of Arabidopsis thaliana were compared. METHODS: In situ hybridization analyses were performed on longitudinal sections of shoot apices from 2-month-old Arabidopsis plants. KEY RESULTS: The study provides evidence for different expression pattern groups. KRP1 and KRP2 expression is restricted to the endoreduplicating tissues. In contrast, KRP4 and KRP5 expression is mainly restricted to mitotically dividing cells. KRP3, KRP6 and KRP7 can be found in both mitotically dividing and endoreduplicating cells. CONCLUSION: The results suggest differential roles for the distinct KRPs. KRP1 and KRP2 might specifically be involved in the establishment of polyploidy. In contrast, KRP4 and KRP5 might be involved in regulating the progression through the mitotic cell cycle. KRP3, KRP6 and KRP7 might have a function in both types of cell cycle. 相似文献
60.
We report the integration of single male crowned guenons (Cercopithecus pogonias) into troops of black colobus (Colobus satanas). We observed one male Cercopithecus pogonias in three troops of Colobus satanas on 30% of observation days (n = 231). Activities of single males guenons did not differ significantly from those of the colobus with which they associated. Moreover, both species performed simultaneously the same activities more often than expected by chance. Interspecific grooming occurred on several occasions. Furthermore, single male guenons spent as much in time social activities when part of a colobus troop, as they typically do when part of a conspecific group. Unlike solitary male crowned guenons, which are silent, a male that is integrated into a troop of colobus is vocal and emits social alarm calls to which colobus monkeys respond. During the single file movements of colobus troops, single male crowned guenons were integrated in the core of the troop and used the same branches at the same height with the colobus. Thus, the life of a single male crowned guenon with black colobus was social. We suggest that the main benefits that he gained is the possibility to live in a social context. Social interactions could be the key element to explain why single males Cercopithecus pogonias join troops of monkeys so different from their natal groups. 相似文献