479 research outputs found
Human oesophageal adenocarcinoma cell lines JROECL 47 and JROECL 50 are admixtures of the human colon carcinoma cell line HCT 116
In two recently described human oesophageal adenocarcinoma cell lines JROECL 47 and JROECL 50, derived from one tumour, we detected identical E-cadherin and ÎČ-catenin gene mutations as in colon carcinoma cell line HCT 116. We demonstrate by HLA-typing, mutation analysis and microsatellite analysis that cell lines JROECL 47 and JROECL 50 are admixtures of the human colon adenocarcinoma cell line HCT 116. © 2000 Cancer Research Campaig
Probing the Interstellar Medium using HI absorption and emission towards the W3 HII region
HI spectra towards the W3 HII complex are presented and used to probe the
Galactic structure and interstellar medium conditions between us and this
region. The overall shape of the spectra is consistent with the predictions of
the Two-Arm Spiral Shock model wherein the gas found in the -40 km/s to -50
km/s range has been accelerated by some 20 km/s from its rotation curve
velocity. Spin temperatures of ~100 K are derived for the Local Arm gas, lower
than found in a previous, similar study towards DR 7. For the interarm region,
values on the order of 300 K are found, implying a negligible filling factor
for the Cold Neutral Medium (<< 1%). Some of the absorbing gas at velocities
near -40 km/s is confirmed to be associated with the HII regions.Comment: 23 pages, 6 figures, accepted for publication in the Astronomical
Journa
High-Mass X-ray Binaries and the Spiral Structure of the Host Galaxy
We investigate the manifestation of the spiral structure in the distribution
of high-mass X-ray binaries (HMXBs) over the host galaxy. We construct the
simple kinematic model. It shows that the HMXBs should be displaced relative to
the spiral structure observed in such traditional star formation rate
indicators as the Halpha and FIR emissions because of their finite lifetimes.
Using Chandra observations of M51, we have studied the distribution of X-ray
sources relative to the spiral arms of this galaxy observed in Halpha. Based on
K-band data and background source number counts, we have separated the
contributions from high-mass and low-mass X-ray binaries and active galactic
nuclei. In agreement with model predictions, the distribution of HMXBs is wider
than that of bright HII regions concentrated in the region of ongoing star
formation. However, the statistical significance of this result is low, as is
the significance of the concentration of the total population of X-ray sources
to the spiral arms. We also predict the distribution of HMXBs in our Galaxy in
Galactic longitude. The distribution depends on the mean HMXB age and can
differ significantly from the distributions of such young objects as
ultracompact HII regions.Comment: 18 pages, 6 figures; Astronomy Letters, Vol. 33, No. 5, 2007, pp.
299-30
Biochemical basis of 5-aminolaevulinic acid-induced protoporphyrin IX accumulation: a study in patients with (pre)malignant lesions of the oesophagus.
Administration of 5-aminolaevulinic acid (ALA) leads to porphyrin accumulation in malignant and premalignant tissues, and ALA is used as a prodrug in photodynamic therapy (PDT). To understand the mechanism of porphyrin accumulation after the administration of ALA and to investigate whether ALA-induced protoporphyrin IX might be a suitable photosensitizer in Barrett's oesophagus and adenocarcinoma, we determined the activities of porphobilinogen deaminase (PBG-D) and ferrochelatase (FC) in various malignant and premalignant as well as in normal tissues of the human oesophagus. A PDT power index for ALA-induced porphyrin accumulation, the ratio of PBG-D to FC normalized for the normal squamous epithelium of the oesophagus, was calculated to evaluate intertissue variation in the ability to accumulate porphyrins. In malignant and premalignant tissue a twofold increased PBG-D activity and a marginally increased FC activity was seen compared with normal squamous epithelium. A significantly increased PDT power index in Barrett's epithelium and adenocarcinoma was found. Our results suggest that, after the administration of ALA, porphyrins will accumulate in a greater amount in Barrett's epithelium and adenocarcinoma of the oesophagus because of an imbalance between PBG-D and FC activities. The PDT power index here defined might be a useful indicative parameter for predicting the susceptibility of these tissues to ALA-PDT
Porphyrin biosynthesis in human Barrett's oesophagus and adenocarcinoma after ingestion of 5-aminolaevulinic acid
5-Aminolaevulinic acid (ALA)-induced porphyrin biosynthesis, which is used for ALA-based photodynamic therapy (ALA-PDT), was studied in tissues of 10 patients with Barrettâs oesophagus (BE) and adenocarcinoma of the oesophagus (AC) undergoing oesophagectomy at a mean time interval of 6.7 h after the ingestion of ALA (60 mg kgâ1). In BE, AC, squamous epithelium (SQ) and gastric cardia, the activities of the haem biosynthetic enzymes porphobilinogen deaminase (PBG-D) and ferrochelatase (FC) and the PDT power index â the ratio between PBG-D and FC in BE and AC in comparison with SQ â were determined before ALA ingestion. Following ALA administration, ALA, porphobilinogen, uroporphyrin I and PPIX were determined in tissues and plasma. The PDT power index did not predict the level of intracellular accumulation of PPIX found at 6.7 h. In BE, there was no selectivity of PPIX accumulation compared to SQ, whereas in half of patients with AC selectivity was found. Higher haem biosynthetic enzyme activities (i.e. PBG-D) and lower PPIX precursor concentrations were found in BE and AC compared to SQ. It is therefore possible that PPIX levels will peak at earlier time intervals in BE and AC compared to SQ. © 2000 Cancer Research Campaig
Star Formation Thresholds in Galactic Disks
We report the first results of a detailed study of the star formation law in
a sample of 32 nearby spiral galaxies with well-measured rotation curves, HI
and H (as traced by CO) surface density profiles, and new \Ha CCD
photometry. Our results strongly support the view that the formation of
gravitationally bound interstellar clouds regulates the onset of widespread
star formation -- at least in the outer regions of galactic disks.Comment: Will appear in July 1 ApJ. Abbreviated abstract. Postscript version
available at http://www.astro.caltech.edu/~clm
The LBT Panoramic View on the Recent Star-Formation Activity in IC2574
We present deep imaging of the star-forming dwarf galaxy IC2574 in the M81
group taken with the Large Binocular Telescope in order to study in detail the
recent star-formation history of this galaxy and to constrain the stellar
feedback on its HI gas. We identify the star-forming areas in the galaxy by
removing a smooth disk component from the optical images. We construct
pixel-by-pixel maps of stellar age and stellar mass surface density in these
regions by comparing their observed colors with simple stellar populations
synthesized with STARBURST99. We find that an older burst occurred about 100
Myr ago within the inner 4 kpc and that a younger burst happened in the last 10
Myr mostly at galactocentric radii between 4 and 8 kpc. We analyze the stellar
populations residing in the known HI holes of IC2574. Our results indicate
that, even at the remarkable photometric depth of the LBT data, there is no
clear one-to-one association between the observed HI holes and the most recent
bursts of star formation in IC2574. The stellar populations formed during the
younger burst are usually located at the periphery of the HI holes and are seen
to be younger than the holes dynamical age. The kinetic energy of the holes
expansion is found to be on average 10% of the total stellar energy released by
the stellar winds and supernova explosions of the young stellar populations
within the holes. With the help of control apertures distributed across the
galaxy we estimate that the kinetic energy stored in the HI gas in the form of
its local velocity dispersion is about 35% of the total stellar energy.Comment: 16 pages, 14 figures, accepted for publication in Ap
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