3,635 research outputs found
HST Snapshot Survey of Post-AGB Objects
The results from a Hubble Space Telescope (HST) snapshot survey of post-AGB
objects are shown. The aim of the survey is to complement existing HST images
of PPN and to connect various types of nebulosities with physical and chemical
properties of their central stars. Nebulosities are detected in 15 of 33
sources. Images and photometric and geometric measurements are presented. For
sources with nebulosities we see a morphological bifurcation into two groups,
DUPLEX and SOLE, as previous studies have found. We find further support to the
previous results suggesting that this dichotomy is caused by a difference in
optical thickness of the dust shell. The remaining 18 sources are classified as
stellar post-AGB objects, because our observations indicate a lack of
nebulosity. We show that some stellar sources may in fact be DUPLEX or SOLE
based on their infrared colors. The cause of the differences among the groups
are investigated. We discuss some evidence suggesting that high progenitor-mass
AGB stars tend to become DUPLEX post-AGB objects. Intermediate progenitor-mass
AGB stars tend to be SOLE post-AGB objects. Most of the stellar sources
probably have low mass progenitors and do not seem to develop nebulosities
during the post-AGB phase and therefore do not become planetary nebulae.Comment: 21 pages, 11 figure
Revealing the mid-infrared emission structure of IRAS 16594-4656 and IRAS 07027-7934
TIMMI2 diffraction-limited mid-infrared images of a multipolar
proto-planetary nebula IRAS 16594-4656 and a young [WC] elliptical planetary
nebula IRAS 07027-7934 are presented. Their dust shells are for the first time
resolved (only marginally in the case of IRAS 07027-7934) by applying the
Lucy-Richardson deconvolution algorithm to the data, taken under exceptionally
good seeing conditions (<0.5"). IRAS 16594-4656 exhibits a two-peaked
morphology at 8.6, 11.5 and 11.7 microns which is mainly attributed to emission
from PAHs. Our observations suggest that the central star is surrounded by a
toroidal structure observed edge-on with a radius of 0.4" (~640 AU at an
assumed distance of 1.6 kpc) with its polar axis at P.A.~80 degrees, coincident
with the orientation defined by only one of the bipolar outflows identified in
the HST optical images. We suggest that the material expelled from the central
source is currently being collimated in this direction and that the multiple
outflow formation has not been coeval. IRAS 07027-7934 shows a bright,
marginally extended emission (FWHM=0.3") in the mid-infrared with a slightly
elongated shape along the N-S direction, consistent with the morphology
detected by HST in the near-infrared. The mid-infrared emission is interpreted
as the result of the combined contribution of small, highly ionized PAHs and
relatively hot dust continuum. We propose that IRAS 07027-7934 may have
recently experienced a thermal pulse (likely at the end of the AGB) which has
produced a radical change in the chemistry of its central star.Comment: 35 pages, 8 figures (figures 1, 2, 4 and 6 are in low resolution)
accepted for publication in Ap
Water maser detections in southern candidates to post-AGB stars and Planetary Nebulae
We intended to study the incidence and characteristics of water masers in the
envelopes of stars in the post-AGB and PN evolutionary stages.
We have used the 64-m antenna in Parkes (Australia) to search for water maser
emission at 22 GHz, towards a sample of 74 sources with IRAS colours
characteristic of post-AGB stars and PNe, at declination . In our
sample, 39% of the sources are PNe or PNe candidates, and 50% are post-AGB
stars or post-AGB candidates.
We have detected four new water masers, all of them in optically obscured
sources: three in PNe candidates (IRAS 12405-6219, IRAS 15103-5754, and IRAS
16333-4807); and one in a post-AGB candidate (IRAS 13500-6106). The PN
candidate IRAS 15103-5754 has water fountain characteristics, and it could be
the first PN of this class found.
We confirm the tendency suggested in Paper I that the presence of water
masers in the post-AGB phase is favoured in obscured sources with massive
envelopes. We propose an evolutionary scenario for water masers in the post-AGB
and PNe stages, in which ``water fountain'' masers could develop during
post-AGB and early PN stages. Later PNe would show lower velocity maser
emission, both along jets and close to the central objects, with only the
central masers remaining in more evolved PNe.Comment: 11 pages, 5 figures. Accepted by Astronomy and Astrophysic
Maternal color‐consciousness is related to more positive and less negative attitudes toward ethnic‐racial outgroups in children in White Dutch families
NWO453-16-008Global Challenges (FGGA
Molecular Imaging of PD-L1 Expression and Dynamics with the Adnectin-Based PET Tracer F-18-BMS-986192
F-18-BMS-986192, an adnectin-based human programmed cell death ligand 1 (PD-L1) tracer, was developed to noninvasively determine whole-body PD-L1 expression by PET. We evaluated the usability of F-18-BMS-986192 PET to detect different PD-L1 expression levels and therapy-induced changes in PD-L1 expression in tumors. Methods: In vitro binding assays with F-18-BMS-986192 were performed on human tumor cell lines with different total cellular and membrane PD-L1 protein expression levels. Subsequently, PET imaging was performed on immunodeficient mice xenografted with these cell lines. The mice were treated with interferon gamma (IFN gamma) intraperitoneally for 3 d or with the mitogen-activated protein kinase kinase inhibitor selumetinib by oral gavage for 24 h. Afterward, F-18-BMS-986192 was administered intravenously, followed by a 60-min dynamic PET scan. Tracer uptake was expressed as percentage injected dose per gram of tissue. Tissues were collected to evaluate ex vivo tracer biodistribution and to perform flow cytometric, Western blot, and immunohistochemical tumor analyses. Results: F-18-BMS-986192 uptake reflected PD-L1 membrane levels in tumor cell lines, and tumor tracer uptake in mice was associated with PD-L1 expression measured immunohistochemically. In vitro IFN gamma treatment increased PD-L1 expression in the tumor cell lines and caused up to a 12-fold increase in tracer binding. In vivo, IFN gamma affected neither PD-L1 tumor expression measured immunohistochemically nor F-18-BMS-986192 tumor uptake. In vitro, selumetinib downregulated cellular and membrane levels of PD-L1 in tumor cells by 50% as measured by Western blotting and flow cytometry. In mice, selumetinib lowered cellular, but not membrane, PD-L1 levels of tumors, and consequently, no treatment-induced change in F-18-BMS-986192 tumor uptake was observed. Conclusion: F-18-BMS-986192 PET imaging allows detection of membrane-expressed PD-L1 as soon as 60 min after tracer injection. The tracer can discriminate a range of tumor cell PD-L1 membrane expression levels
Development and evaluation of interleukin-2 derived radiotracers for PET imaging of T-cells in mice
Recently, N-(4-18F-fluorobenzoyl)-interleukin-2 (18F-FB-IL2) was introduced as a PET tracer for T cell imaging. However, production is complex and time-consuming. Therefore, we developed 2 radiolabeled IL2 variants, namely aluminum 18F-fluoride-(restrained complexing agent)-IL2 (18F-AlF-RESCA-IL2) and 68Ga-gallium-(1,4,7-triazacyclononane-4,7-diacetic acid-1-glutaric acid)-IL2 (68Ga-Ga-NODAGA-IL2), and compared their in vitro and in vivo characteristics with 18F-FB-IL2. Methods: Radiolabeling of 18F-AlF-RESCA-IL2 and 68Ga-Ga-NODAGA-IL2 was optimized, and stability was evaluated in human serum. Receptor binding was studied with activated human peripheral blood mononuclear cells (hPBMCs). Ex vivo tracer biodistribution in immunocompetent BALB/cOlaHsd (BALB/c) mice was performed at 15, 60, and 90 min after tracer injection. In vivo binding characteristics were studied in severe combined immunodeficient (SCID) mice inoculated with activated hPBMCs in Matrigel. Tracer was injected 15 min after hPBMC inoculation, and a 60-min dynamic PET scan was acquired, followed by ex vivo biodistribution studies. Specific uptake was determined by coinjection of tracer with unlabeled IL2 and by evaluating uptake in a control group inoculated with Matrigel only. Results:68Ga-Ga-NODAGA-IL2 and 18F-AlF-RESCA-IL2 were produced with radiochemical purity of more than 95% and radiochemical yield of 13.1% ± 4.7% and 2.4% ± 1.6% within 60 and 90 min, respectively. Both tracers were stable in serum, with more than 90% being intact tracer after 1 h. In vitro, both tracers displayed preferential binding to activated hPBMCs. Ex vivo biodistribution studies on BALB/c mice showed higher uptake of 18F-AlF-RESCA-IL2 than of 18F-FB-IL2 in liver, kidney, spleen, bone, and bone marrow. 68Ga-Ga-NODAGA-IL2 uptake in liver and kidney was higher than 18F-FB-IL2 uptake. In vivo, all tracers revealed uptake in activated hPBMCs in SCID mice. Low uptake was seen after a blocking dose of IL2 and in the Matrigel control group. In addition, 18F-AlF-RESCA-IL2 yielded the highest-contrast PET images of target lymph nodes. Conclusion: Production of 18F-AlF-RESCA-IL2 and 68Ga-Ga-NODAGA-IL2 is simpler and faster than that of 18F-FB-IL2. Both tracers showed good in vitro and in vivo characteristics, with high uptake in lymphoid tissue and hPBMC xenografts
Clinical-grade N-(4-[18F]fluorobenzoyl)-interleukin-2 for PET imaging of activated T-cells in humans
BACKGROUND: Molecular imaging of immune cells might be a potential tool for response prediction, treatment evaluation and patient selection in inflammatory diseases as well as oncology. Targeting interleukin-2 (IL2) receptors on activated T-cells using positron emission tomography (PET) with N-(4-[18F]fluorobenzoyl)-interleukin-2 ([18F]FB-IL2) could be such a strategy. This paper describes the challenging translation of the partly manual labeling of [18F]FB-IL2 for preclinical studies into an automated procedure following Good Manufacturing Practices (GMP), resulting in a radiopharmaceutical suitable for clinical use. METHODS: The preclinical synthesis of [18F]FB-IL2 was the starting point for translation to a clinical production method. To overcome several challenges, major adaptations in the production process were executed. The final analytical methods and production method were validated and documented. All data with regards to the quality and safety of the final drug product were documented in an investigational medicinal product dossier. RESULTS: Restrictions in the [18F]FB-IL2 production were imposed by hardware configuration of the automated synthesis equipment and by use of disposable cassettes. Critical steps in the [18F]FB-IL2 production comprised the purification method, stability of recombinant human IL2 and the final formulation. With the GMP compliant production method, [18F]FB-IL2 could reliably be produced with consistent quality complying to all specifications. CONCLUSIONS: To enable the use of [18F]FB-IL2 in clinical studies, a fully automated GMP compliant production process was developed. [18F]FB-IL2 is now produced consistently for use in clinical studies
Ethylene augments root hypoxia tolerance via growth cessation and reactive oxygen species amelioration
Flooded plants experience impaired gas diffusion underwater, leading to oxygen deprivation (hypoxia). The volatile plant hormone ethylene is rapidly trapped in submerged plant cells and is instrumental for enhanced hypoxia acclimation. However, the precise mechanisms underpinning ethylene-enhanced hypoxia survival remain unclear. We studied the effect of ethylene pretreatment on hypoxia survival of Arabidopsis (Arabidopsis thaliana) primary root tips. Both hypoxia itself and re-oxygenation following hypoxia are highly damaging to root tip cells, and ethylene pretreatments reduced this damage. Ethylene pretreatment alone altered the abundance of transcripts and proteins involved in hypoxia responses, root growth, translation, and reactive oxygen species (ROS) homeostasis. Through imaging and manipulating ROS abundance in planta, we demonstrated that ethylene limited excessive ROS formation during hypoxia and subsequent re-oxygenation and improved oxidative stress survival in a PHYTOGLOBIN1-dependent manner. In addition, we showed that root growth cessation via ethylene and auxin occurred rapidly and that this quiescence behavior contributed to enhanced hypoxia tolerance. Collectively, our results show that the early flooding signal ethylene modulates a variety of processes that all contribute to hypoxia surviva
Ethylene augments root hypoxia tolerance through amelioration of reactive oxygen species and growth cessation
Flooded plants experience impaired gas diffusion underwater, leading to oxygen deprivation (hypoxia). The volatile plant hormone ethylene is rapidly trapped in submerged plant cells and is instrumental for enhanced hypoxia acclimation. However, the precise mechanisms underpinning ethylene-enhanced hypoxia survival remain unclear. We studied the effect of ethylene pre-treatment on hypoxia survival of primary Arabidopsis thaliana root tips. Both hypoxia itself and re-oxygenation following hypoxia are highly damaging to root tip cells and ethylene pre-treatments reduced this damage. Ethylene pre-treatment alone altered the available abundance of transcripts and proteins involved in hypoxia responses, root growth, translation and reactive oxygen species (ROS) homeostasis. Through imaging and manipulating ROS abundance in planta, we demonstrate that ethylene limits excessive ROS formation during hypoxia and subsequent re-oxygenation and improves oxidative stress survival. In addition, we show that ethylene leads to rapid root growth cessation and this quiescence behaviour contributes to enhanced hypoxia tolerance. Collectively, our results show that the early flooding signal ethylene modulates a variety of processes that all contribute to hypoxia survival
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