Introduction
Uveal melanoma (UM) cells and neurohormone-producing cells both originate from the neural crest. Somatostatin receptors subtype 2 (SSTR2) are over-expressed in several tumors, often from ...neuroendocrine origin, and synthetic antagonists like octreotide and octreotate are being used as diagnostic or therapeutic agents. We investigated the SSTR2 expression in UM, and determined whether this expression was related to prognosis of the disease.
Materials and methods
UM cell lines and fresh primary UM samples were tested for SSTR2 expression by autoradiography (AR) using 125I-Tyr3-octreotate. Furthermore, UM cell lines were analyzed for SSTR2 mRNA expression with quantitative real-time RT-PCR.
Results
Using AR, cell-surface SSTR2 expression was demonstrated in two UM metastatic cell lines, but no expression was detected in three cell lines derived from primary UM. However, all primary and metastatic UM cell lines showed mRNA expression levels for SSTR2 using quantitative real-time RT-PCR. Only three of 14 primary UM demonstrated moderate SSTR2 expression, and this expression was not significantly associated with tumor-free survival or any tested prognostic factor.
Conclusions
Based on the rare and low expression of SSTR2 found in primary UM specimens and in UM cell lines, we conclude that SSTR2 is not widely expressed in UM. Furthermore, SSTR2 expression was not associated with tumor-free survival and prognostic factors. Therefore SSTR2 is not suited as prognostic marker or therapeutic target in UM.
Aims.
We aim to probe the magnetic field geometry and particle acceleration mechanism in the relativistic jets of supermassive black holes.
Methods.
We conducted a polarimetry campaign from radio to ...X-ray wavelengths of the high-synchrotron-peak (HSP) blazar Mrk 421, including Imaging X-ray Polarimetry Explorer (IXPE) measurements from 2022 December 6–8. During the IXPE observation, we also monitored Mrk 421 using
Swift
-XRT and obtained a single observation with
XMM-Newton
to improve the X-ray spectral analysis. The time-averaged X-ray polarization was determined consistently using the event-by-event Stokes parameter analysis, spectropolarimetric fit, and maximum likelihood methods. We examined the polarization variability over both time and energy, the former via analysis of IXPE data obtained over a time span of 7 months.
Results.
We detected X-ray polarization of Mrk 421 with a degree of Π
X
= 14 ± 1% and an electric-vector position angle
ψ
X
= 107 ± 3° in the 2–8 keV band. From the time variability analysis, we find a significant episodic variation in
ψ
X
. During the 7 months from the first IXPE pointing of Mrk 421 in 2022 May,
ψ
X
varied in the range 0° to 180°, while Π
X
remained relatively constant within ∼10–15%. Furthermore, a swing in
ψ
X
in 2022 June was accompanied by simultaneous spectral variations. The results of the multiwavelength polarimetry show that Π
X
was generally ∼2–3 times greater than Π at longer wavelengths, while
ψ
fluctuated. Additionally, based on radio, infrared, and optical polarimetry, we find that the rotation of
ψ
occurred in the opposite direction with respect to the rotation of
ψ
X
and over longer timescales at similar epochs.
Conclusions.
The polarization behavior observed across multiple wavelengths is consistent with previous IXPE findings for HSP blazars. This result favors the energy-stratified shock model developed to explain variable emission in relativistic jets. We considered two versions of the model, one with linear and the other with radial stratification geometry, to explain the rotation of
ψ
X
. The accompanying spectral variation during the
ψ
X
rotation can be explained by a fluctuation in the physical conditions, for example in the energy distribution of relativistic electrons. The opposite rotation direction of
ψ
between the X-ray and longer wavelength polarization accentuates the conclusion that the X-ray emitting region is spatially separated from that at longer wavelengths. Moreover, we identify a highly polarized knot of radio emission moving down the parsec-scale jet during the episode of
ψ
X
rotation, although it is unclear whether there is any connection between the two events.
We report the X-ray polarization properties of the high-synchrotron-peaked (HSP) blazar PKS 2155$-$304 based on observations with the Imaging X-ray Polarimetry Explorer (IXPE). We observed the source ...between Oct 27 and Nov 7, 2023. We also conducted an extensive contemporaneous multiwavelength (MW) campaign. We find that during the first half ($T_1$) of the IXPE pointing, the source exhibited the highest X-ray polarization degree detected for an HSP blazar thus far, (30.7pm 2.0)<!PCT!>; this dropped to (15.3pm 2.1)<!PCT!> during the second half ($T_2$). The X-ray polarization angle remained stable during the IXPE pointing at 129.4 and 125.4 during $T_1$ and $T_2$, respectively. Meanwhile, the optical polarization degree remained stable during the IXPE pointing, with average host-galaxy-corrected values of (4.3pm 0.7)<!PCT!> and (3.8pm 0.9)<!PCT!> during the $T_1$ and $T_2$, respectively. During the IXPE pointing, the optical polarization angle changed achromatically from sim 140 to sim 90 and back to sim 130 Despite several attempts, we only detected (99.7<!PCT!> conf.) the radio polarization once (during $T_2$, at 225.5 GHz): with degree (1.7pm 0.4)<!PCT!> and angle 112.5 The direction of the broad pc-scale jet is rather ambiguous and has been found to point to the east and south at different epochs; however, on larger scales (> 1.5 pc) the jet points toward the southeast (sim 135 similarly to all of the MW polarization angles. Moreover, the X-ray-to-optical polarization degree ratios of sim 7 and sim 4 during $T_1$ and $T_2$, respectively, are similar to previous IXPE results for several HSP blazars. These findings, combined with the lack of correlation of temporal variability between the MW polarization properties, agree with an energy-stratified shock-acceleration scenario in HSP blazars.
The Lorentz Invariance Violation (LIV), a proposed consequence of certain quantum gravity (QG) scenarios, could instigate an energy-dependent group velocity for ultra-relativistic particles. This ...energy dependence, although suppressed by the massive QG energy scale \(E_\mathrm{QG}\), expected to be on the level of the Planck energy \(1.22 \times 10^{19}\) GeV, is potentially detectable in astrophysical observations. In this scenario, the cosmological distances traversed by photons act as an amplifier for this effect. By leveraging the observation of a remarkable flare from the blazar Mrk\,421, recorded at energies above 100 GeV by the MAGIC telescopes on the night of April 25 to 26, 2014, we look for time delays scaling linearly and quadratically with the photon energies. Using for the first time in LIV studies a binned-likelihood approach we set constraints on the QG energy scale. For the linear scenario, we set \(95\%\) lower limits \(E_\mathrm{QG}>2.7\times10^{17}\) GeV for the subluminal case and \(E_\mathrm{QG}> 3.6 \times10^{17}\) GeV for the superluminal case. For the quadratic scenario, the \(95\%\) lower limits for the subluminal and superluminal cases are \(E_\mathrm{QG}>2.6 \times10^{10}\) GeV and \(E_\mathrm{QG}>2.5\times10^{10}\) GeV, respectively.
In recent years, a new generation of optical intensity interferometers has emerged, leveraging the existing infrastructure of Imaging Atmospheric Cherenkov Telescopes (IACTs). The MAGIC telescopes ...host the MAGIC-SII system (Stellar Intensity Interferometer), implemented to investigate the feasibility and potential of this technique on IACTs. After the first successful measurements in 2019, the system was upgraded and now features a real-time, dead-time-free, 4-channel, GPU-based correlator. These hardware modifications allow seamless transitions between MAGIC's standard very-high-energy gamma-ray observations and optical interferometry measurements within seconds. We establish the feasibility and potential of employing IACTs as competitive optical Intensity Interferometers with minimal hardware adjustments. The measurement of a total of 22 stellar diameters are reported, 9 corresponding to reference stars with previous comparable measurements, and 13 with no prior measurements. A prospective implementation involving telescopes from the forthcoming Cherenkov Telescope Array Observatory's northern hemisphere array, such as the first prototype of its Large-Sized Telescopes, LST-1, is technically viable. This integration would significantly enhance the sensitivity of the current system and broaden the UV-plane coverage. This advancement would enable the system to achieve competitive sensitivity with the current generation of long-baseline optical interferometers over blue wavelengths.
Axion-like particles (ALPs) are pseudo-Nambu-Goldstone bosons that emerge in various theories beyond the standard model. These particles can interact with high-energy photons in external magnetic ...fields, influencing the observed gamma-ray spectrum. This study analyzes 41.3 hrs of observational data from the Perseus Galaxy Cluster collected with the MAGIC telescopes. We focused on the spectra the radio galaxy in the center of the cluster: NGC 1275. By modeling the magnetic field surrounding this target, we searched for spectral indications of ALP presence. Despite finding no statistical evidence of ALP signatures, we were able to exclude ALP models in the sub-micro electronvolt range. Our analysis improved upon previous work by calculating the full likelihood and statistical coverage for all considered models across the parameter space. Consequently, we achieved the most stringent limits to date for ALP masses around 50 neV, with cross sections down to \(g_{a\gamma} = 3 \times 10^{-12}\) GeV\(^{-1}\).
Purpose Uveal melanoma patients that present a tumor with monosomy 3 have a high propensity to develop metastases. Based on the two‐hit hypothesis, one might expect that the remaining copy of ...chromosome 3 contains a genetically‐modified gene and that loss of this gene is responsible for malignant progression. Identification of the gene and the genetic or epigenetic mechanisms that influence genes on chromosome 3 will enlighten the pathway(s) that determine uveal melanoma progression. In addition, studying epigenetics may result in useful molecular markers: whereas analysis of monosomy 3 is useful in primary tumors, it is useless in the detection of spreading tumor cells in the blood. We propose that a molecular marker in the form of a (tumor specific) genetic or epigenetic modification will be more helpful in this respect.
Methods We have analyzed genes on chromosome 3 for epigenetic regulation that may suffice in non‐invasive testing for spreading tumor cells.
Results We have identified RASSF1a methylation as a predictor of metastasis in uveal melanoma based on analysis of uveal melanoma tissues. In order to detect disseminating tumor cells in the bloodstream of uveal melanoma patients we have developed a very sensitive assay for methylation of RASSF1a. The detection limit of RASSF1a methylation exceeds 1/10,000 and in combination with isolation cell‐free DNA we are able to detect tumor DNA in the background of a vast excess of normal blood cells. With this assay we will test patient blood and validate the prognostic and diagnostic value of this marker.
Conclusion With this assay we will test patient blood and validate the prognostic and diagnostic value of this marker.
Gamma-ray bursts (GRBs) are explosive transient events occurring at cosmological distances, releasing a large amount of energy as electromagnetic radiation over several energy bands. We report the ...detection of the long GRB~201216C by the MAGIC telescopes. The source is located at \(z=1.1\) and thus it is the farthest one detected at very high energies. The emission above \SI{70}{\GeV} of GRB~201216C is modelled together with multi-wavelength data within a synchrotron and synchrotron-self Compton (SSC) scenario. We find that SSC can explain the broadband data well from the optical to the very-high-energy band. For the late-time radio data, a different component is needed to account for the observed emission. Differently from previous GRBs detected in the very-high-energy range, the model for GRB~201216C strongly favors a wind-like medium. The model parameters have values similar to those found in past studies of the afterglows of GRBs detected up to GeV energies.
The tissue concentration of an extravascularly distributed MRI contrast agent required to achieve a 20% change in the MRI signal intensity (SI) of skeletal muscle was determined using radiolabeled ...gadoteridol administered to nephrectomized mice. This minimal change in the quantified SI was reliably detected qualitatively in the MR muscle images. MR images of muscle were acquired following each intravenous injection of six sequential doses of 0.8 μmol of
153Gd-labeled gadoteridol. A 2.0 T imaging spectrometer and a T
1-weighted spin-echo pulse sequence were used to acquire the MR images. After imaging, the injected
153Gd in muscle was measured, and the
153Gd assay results were used to determine the gadoteridol concentration in muscle following each injection. The muscle concentrations of gadoteridol were then correlated to the quantified enhanced MR SI of muscle. Using the 20% factor, it was concluded that the amount of gadoteridol necessary to achieve a reliable change in the SI of muscle was 33 ± 10 nmol/g-skeletal muscle.
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