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排序方式: 共有224条查询结果,搜索用时 46 毫秒
191.
Marcus G?rge Ullisch Jürgen Johann Scheins Christoph Weirich Elena Rota Kops Abdullah Celik Lutz Tellmann Tony St?cker Hans Herzog Nadim Jon Shah 《PloS one》2012,7(11)
Positron Emission Tomography (PET) images are prone to motion artefacts due to the long acquisition time of PET measurements. Recently, simultaneous magnetic resonance imaging (MRI) and PET have become available in the first generation of Hybrid MR-PET scanners. In this work, the elimination of artefacts due to head motion in PET neuroimages is achieved by a new approach utilising MR-based motion tracking in combination with PET list mode data motion correction for simultaneous MR-PET acquisitions. The method comprises accurate MR-based motion measurements, an intra-frame motion minimising and reconstruction time reducing temporal framing algorithm, and a list mode based PET reconstruction which utilises the Ordinary Poisson Algorithm and avoids axial and transaxial compression. Compared to images uncorrected for motion, an increased image quality is shown in phantom as well as in vivo images. In vivo motion corrected images show an evident increase of contrast at the basal ganglia and a good visibility of uptake in tiny structures such as superior colliculi. 相似文献
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193.
Embryo transfer (ET) in the donkey resulted in a very low recipient pregnancy rates. The aim of these studies was to investigate if nonsurgical transfer techniques or donkey embryo quality affect donkey recipient pregnancy failure. In Study 1, the impact of transfer technique was investigated by evaluating if cervical catheterization is associated with prostaglandin release and suppression of luteal function and if donkey recipients would become pregnant after nonsurgical transfer of horse embryos. Four jennies, from 5 to 8 d after ovulation, were submitted to a sham transcervical ET and to evaluation of PGFM and progesterone plasma concentrations. Five 8 d horse embryos were nonsurgically transferred into synchronized donkey recipients (HD). Cervical stimulation caused a transient PGF2α release in two of four jennies in the absence of a significant decrease in progesterone plasma concentration. All transferred horse embryos resulted in pregnancies in the jenny recipients. In Study 2, donkey embryo viability was investigated by 1.2 meters, 6-diamidino-2-phenylindole (DAPI) staining of 10 embryos and by the transfer of 6 and 12 donkey embryos in synchronized mare (DH) and donkey (DD) recipients, respectively, of known fertility. The estimated proportion of dead cells in DAPI stained embryos was 0.9% (range 0-3.9%) and below what is considered normal (20%) for horse embryos. Three of six and six of 12 of the DH and DD ETs, respectively resulted in pregnancies at 14 and 25 d (50%), a higher pregnancy rate than previously reported after DD ET. The overall results of this study suggest that the transcervical technique for ET and donkey embryo viability are not the reasons for the low pregnancy rates that have previously been described in donkey recipients, and that nonsurgical ET in donkeys can result in acceptable results. 相似文献
194.
Sabrina Duranti Gabriele Andrea Lugli Christian Milani Kieran James Leonardo Mancabelli Francesca Turroni Giulia Alessandri Marta Mangifesta Walter Mancino Maria Cristina Ossiprandi Alexandra Iori Claudio Rota Giancarlo Gargano Sergio Bernasconi Francesco Di Pierro Douwe van Sinderen Marco Ventura 《Environmental microbiology》2019,21(10):3683-3695
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196.
Yi Qiao Aaron R Quinlan Amir A Jazaeri Roeland GW Verhaak David A Wheeler Gabor T Marth 《Genome biology》2014,15(8)
Many tumors are composed of genetically divergent cell subpopulations. We report SubcloneSeeker, a package capable of exhaustive identification of subclone structures and evolutionary histories with bulk somatic variant allele frequency measurements from tumor biopsies. We present a statistical framework to elucidate whether specific sets of mutations are present within the same subclones, and the order in which they occur. We demonstrate how subclone reconstruction provides crucial information about tumorigenesis and relapse mechanisms; guides functional study by variant prioritization, and has the potential as a rational basis for informed therapeutic strategies for the patient. SubcloneSeeker is available at: https://github.com/yiq/SubcloneSeeker.
Electronic supplementary material
The online version of this article (doi:10.1186/s13059-014-0443-x) contains supplementary material, which is available to authorized users. 相似文献197.
N. Jon Shah Hans Herzog Christoph Weirich Lutz Tellmann Joachim Kaffanke Liliana Caldeira Elena Rota Kops Syed M. Qaim Heinz H. Coenen Hidehiro Iida 《PloS one》2014,9(4)
Simultaneous, hybrid MR-PET is expected to improve PET image resolution in the plane perpendicular to the static magnetic field of the scanner. Previous papers have reported this either by simulation or experiment with simple sources and detector arrangements. Here, we extend those studies using a realistic brain phantom in a recently installed MR-PET system comprising a 9.4 T MRI-scanner and an APD-based BrainPET insert in the magnet bore. Point and line sources and a 3D brain phantom were filled with 18F (low-energy positron emitter), 68Ga (medium energy positron emitter) or 120I, a non-standard positron emitter (high positron energies of up to 4.6 MeV). Using the BrainPET insert, emission scans of the phantoms were recorded at different positions inside and outside the magnet bore such that the magnetic field was 0 T, 3 T, 7 T or 9.4 T. Brain phantom images, with the ‘grey matter’ compartment filled with 18F, showed no obvious resolution improvement with increasing field. This is confirmed by practically unchanged transaxial FWHM and ‘grey/white matter’ ratio values between at 0T and 9.4T. Field-dependent improvements in the resolution and contrast of transaxial PET images were clearly evident when the brain phantom was filled with 68Ga or 120I. The grey/white matter ratio increased by 7.3% and 16.3%, respectively. The greater reduction of the FWTM compared to FWHM in 68Ga or 120I line-spread images was in agreement with the improved contrast of 68Ga or 120I images. Notwithstanding elongations seen in the z-direction of 68Ga or 120I point source images acquired in foam, brain phantom images show no comparable extension. Our experimental study confirms that integrated MR-PET delivers improved PET image resolution and contrast for medium- and high-energy positron emitters even though the positron range is reduced only in directions perpendicular to the magnetic field. 相似文献
198.
Infection risk dictates immunological divergence among populations in a Mediterranean lizard 下载免费PDF全文
K. Sagonas I. A. Rota O. E. Tsitsilonis P. Pafilis E. D. Valakos 《Journal of evolutionary biology》2016,29(9):1680-1688
The ability of vertebrates to evolve different defence strategies in response to varying parasitism regimes remains poorly understood. Hosts may adopt two different strategies to defend themselves against parasites: tolerance (hosts alleviate the negative fitness consequences of parasite infection) and resistance (hosts strengthen their immune response as parasite burden increases). Both strategies are effective, but fitness has been reported to decline faster in less‐tolerant individuals. Here, we assessed the number of splenocytes and the cell‐mediated response (proxies for resistance) and body condition (a proxy for tolerance) in four populations of a Greek endemic lizard (Podarcis gaigeae), each exposed to different infection risks (defined as the cumulative effect of parasite burden and duration of exposure). We anticipated that populations with heavy parasite burden would enhance the efficacy of their immune response (resistance) compared to lizards deriving from parasite‐poor habitats. We also predicted that populations with longer exposure to parasites would be adopted and be more tolerant. Each factor (duration of exposure and parasite burden) had a distinct effect on the immune response, and thus, our results were rather complicated. Lizards with heavy parasite burden and aperiodic exposure demonstrated resistance, whereas lizards with heavy parasite burden and chronic exposure were more tolerant. Populations with low parasite burden and minimal exposure were more resistant. Our results suggest that the development of some immunological strategies may be differentiated under different infection risks, even within the same species. 相似文献
199.
Duccio Panzani Alessandra Rota Paola Marmorini Iacopo Vannozzi Francesco Camillo 《Theriogenology》2014
In this study, 198 donor mares of different breeds, ages, and reproductive category were inseminated with fresh, cooled and frozen or frozen and cooled semen at the embryo transfer station or in private artificial insemination centers during 10 breeding seasons. The results of this activity were retrospectively analyzed by Pearson Chi-square test and logistic regression to evaluate factors affecting multiple ovulations, embryo recovery, embryo quality, and embryo diameter. Out of the 661 cycles, 937 ovulations were recorded (mean ovulations/cycle: 1.42 ± 0.58). Ovulation rate and incidence of multiple ovulations were significantly affected by age, breed, and reproductive category. Uterine flushings for embryo recovery were performed between 7 and 10 days after ovulation and resulted in the recovery of 338 embryos (51.1% embryos/cycle and 36.1% embryos/ovulation, respectively). At least one embryo was recovered in 298 flushings (45.1%). The factors affecting embryo recovery were age, breed, reproductive category, type of semen, number of ovulations, and location of artificial insemination. Flushing protocol and day of flushing had no effect on embryo recovery. Age, type of semen, number of ovulations, and day of flushing had a significant influence on embryo diameter (N = 215). None of the factors included in the model had an effect on embryo quality distribution. 相似文献
200.
Roel GW Verhaak Mathijs A Sanders Maarten A Bijl Ruud Delwel Sebastiaan Horsman Michael J Moorhouse Peter J van der Spek Bob Löwenberg Peter JM Valk 《BMC bioinformatics》2006,7(1):337-4