75 research outputs found
Photometry and low resolution spectroscopy of hot post-AGB candidates
We have obtained Johnson U, B, V and Cousins R, I photometry and low
resolution spectra of a small sample of hot post-AGB candidates. Using the
present data in combination with JHK data from 2MASS, infrared data from the
MSX catalog and the IRAS fluxes, we have studied the spectral energy
distribution (SED) of these stars. Using the DUSTY code we have estimated the
dust temperatures, the distances to the stars, the mass-loss rates, angular
radii of the inner boundary of the dust envelopes and dynamical ages from the
tip of the AGB. These candidates have also been imaged through a narrow band
H-alpha filter, to search for nebulosity around the central stars. Our H-alpha
images revealed the bipolar morphology of the low excitation PN IRAS 17395-0841
with an angular extent of 2.8arcsec. The bipolar lobes of IRAS 17423-1755 in
H-alpha were found to have an angular extent of 3.5arcsec (south-east lobe) and
2.2arcsec (north-west lobe). The dust envelope characteristics, low resolution
spectrum and IRAS colors suggest that IRAS 18313-1738 is similar to the
proto-planetary nebula (PPN) HD 51585. The SED of IRAS 17423-1755, IRAS
18313-1738 and IRAS 19127+1717 show a warm dust component (in addition to the
cold dust) which may be due to recent and ongoing mass-loss.Comment: 20 pages, 6 figures, h-alpha figure compressed with XV, paper
accepted for publication in Astronomy & Astrophysic
Staggered Spin Order of Localized pi-electrons in the Insulating State of the Organic Conductor kappa-BETS)2Mn[N(CN)2]3
Magnetic properties of the conduction pi-electron system of
kappa-BETS)2Mn[N(CN)2]3 have been probed using 13C NMR. At ambient pressure,
the metal-insulator transition observed in the resistivity measurements below
T~23K is shown to be accompanied by ordering of the pi-spins in a long-range
staggered structure. As the metal-insulator transition is suppressed by
applying a small pressure of ~0.5 kbar, the pi-spin system maintains the
properties of the metallic state down to 5K.Comment: 13 pages, 4 figure
The Human Retinoblastoma Gene Is Imprinted
Genomic imprinting is an epigenetic process leading to parent-of-origin–specific DNA methylation and gene expression. To date, ∼60 imprinted human genes are known. Based on genome-wide methylation analysis of a patient with multiple imprinting defects, we have identified a differentially methylated CpG island in intron 2 of the retinoblastoma (RB1) gene on chromosome 13. The CpG island is part of a 5′-truncated, processed pseudogene derived from the KIAA0649 gene on chromosome 9 and corresponds to two small CpG islands in the open reading frame of the ancestral gene. It is methylated on the maternal chromosome 13 and acts as a weak promoter for an alternative RB1 transcript on the paternal chromosome 13. In four other KIAA0649 pseudogene copies, which are located on chromosome 22, the two CpG islands have deteriorated and the CpG dinucleotides are fully methylated. By analysing allelic RB1 transcript levels in blood cells, as well as in hypermethylated and 5-aza-2′-deoxycytidine–treated lymphoblastoid cells, we have found that differential methylation of the CpG island skews RB1 gene expression in favor of the maternal allele. Thus, RB1 is imprinted in the same direction as CDKN1C, which operates upstream of RB1. The imprinting of two components of the same pathway indicates that there has been strong evolutionary selection for maternal inhibition of cell proliferation
Normalisation to Blood Activity Is Required for the Accurate Quantification of Na/I Symporter Ectopic Expression by SPECT/CT in Individual Subjects
The utilisation of the Na/I symporter (NIS) and associated radiotracers as a reporter system for imaging gene expression is now reaching the clinical setting in cancer gene therapy applications. However, a formal assessment of the methodology in terms of normalisation of the data still remains to be performed, particularly in the context of the assessment of activities in individual subjects in longitudinal studies. In this context, we administered to mice a recombinant, replication-incompetent adenovirus encoding rat NIS, or a human colorectal carcinoma cell line (HT29) encoding mouse NIS. We used 99mTc pertechnetate as a radiotracer for SPECT/CT imaging to determine the pattern of ectopic NIS expression in longitudinal kinetic studies. Some animals of the cohort were culled and NIS expression was measured by quantitative RT-PCR and immunohistochemistry. The radioactive content of some liver biopsies was also measured ex vivo. Our results show that in longitudinal studies involving datasets taken from individual mice, the presentation of non-normalised data (activity expressed as %ID/g or %ID/cc) leads to ‘noisy’, and sometimes incoherent, results. This variability is due to the fact that the blood pertechnetate concentration can vary up to three-fold from day to day. Normalisation of these data with blood activities corrects for these inconsistencies. We advocate that, blood pertechnetate activity should be determined and used to normalise the activity measured in the organ/region of interest that expresses NIS ectopically. Considering that NIS imaging has already reached the clinical setting in the context of cancer gene therapy, this normalisation may be essential in order to obtain accurate and predictive information in future longitudinal clinical studies in biotherapy
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