Abstract. V838 Mon is marking one of the most mysterious stellar outbursts on record. The spectral energy distribution of the progenitor resembles an under-luminous F main sequence star (at V =15.6 mag), that erupted into a cool supergiant following a complex and multi-maxima lightcurve (peaking at V =6.7 mag). The outburst spectrum show BaII, LiI and lines of several s−elements, with wide P-Cyg profiles and a moderate and retracing emission in the Balmer lines. A light-echo discovered expanding around the object helped to constrain the distance (d=790±30 pc), providing MV = +4.45 in quiescence and MV = −4.35 at optical maximum (somewhat dependent on the still uncertain EB−V =0.5 reddening). The general outburst trend is toward lower temperatures and larger luminosities, and continuing so at the time of writing. The object properties conflict with a classification within already existing categories: the progenitor was not on a post-AGB track and thus the similarities with the bornagain AGB stars FG Sge, V605 Aql and Sakurai's object are limited to the cool giant spectrum at maximum; the cool spectrum, the moderate wind velocity (500 km sec −1 and progressively reducing) and the monotonic decreasing of the low ionization condition argues against a classical nova scenario. The closest similarity is with a star that erupted into an M-type supergiant discovered in M31 by Rich et al. (1989), that became however much brighter by peaking at MV = −9.95, and with V4332 Sgr that too erupted into an M-type giant (Martini et al. 1999) and that attained a lower luminosity, closer to that of V838 Mon. M31-RedVar, V4332 Sgr and V838 Mon could be all manifestations of a new class of astronomical objects.

In this paper, we showed that Cerenkov radiation (CR) escaping from the surface of small living animals injected with (18)F-FDG can be detected with optical imaging techniques. (18)F decays by emitting positrons with a maximum energy of 0.635 MeV; such positrons, when travelling into tissues faster than the speed of light in the same medium, are responsible of CR emission. A detailed model of the CR spectrum considering the positron energy spectrum was developed in order to quantify the amount of light emission. The results presented in this work were obtained using a commercial optical imager equipped with charged coupled detectors (CCD). Our data open the door to optical imaging (OI) in vivo of the glucose metabolism, at least in pre-clinical research. We found that the heart and bladder can be clearly identified in the animal body reflecting the accumulation of the (18)F-FDG. Moreover, we describe two different methods based on the spectral analysis of the CR that can be used to estimate the depth of the source inside the animal. We conclude that (18)F-FDG can be employed as it is as a bimodal tracer for positron emission tomography (PET) and OI techniques. Our results are encouraging, suggesting that it could be possible to apply the proposed approach not only to beta(+) but also to pure beta(-) emitters.

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Quite recently Cerenkov luminescence imaging (CLI) has been introduced as a novel pre-clinical imaging for the in vivo imaging of small animals such as mice. The CLI method is based on the detection of Cerenkov radiation (CR) generated by beta particles as they travel into the animal tissues with an energy such that Cerenkov emission condition is satisfied. This paper describes an image reconstruction method called multi spectral diffuse Cerenkov luminescence tomography (msCLT) in order to obtain 3D images from the detection of CR. The multispectral approach is based on a set of 2D planar images acquired using a number of narrow bandpass filters, and the distinctive information content at each wavelength is used in the 3D image reconstruction process. The proposed msCLT method was tested both in vitro and in vivo using 32P-ATP and all the images were acquired by using the IVIS 200 small animal optical imager (Caliper Life Sciences, Alameda USA). Source depth estimation and spatial resolution measurements were performed using a small capillary source placed between several slices of chicken breast. The theoretical Cerenkov emission spectrum and optical properties of chicken breast were used in the modelling of photon propagation. In vivo imaging was performed by injecting control nude mice with 10 MBq of 32P-ATP and the 3D tracer bio-distribution was reconstructed. Whole body MRI was acquired to provide an anatomical localization of the Cerenkov emission. The spatial resolution obtained from the msCLT reconstructed images of the capillary source showed that the FWHM is about 1.5 mm for a 6 mm depth. Co-registered MRI images showed that the Cerenkov emission regions matches fairly well with anatomical regions, such as the brain, heart and abdomen. Ex vivo imaging of the different organs such as intestine, brain, heart and ribs further confirms these findings. We conclude that in vivo 3D bio-distribution of a pure beta-minus emitting radiopharmaceutical such as 32P-ATP can be obtained using the msCLT reconstruction approach.

Tumor microenvironment in carcinomas recruits mesenchymal cells with an abnormal proangiogenic and invasive phenotype. It is not clear whether mesenchymal tumor cells (MTCs) derive from the activation of mature fibroblasts or from their stem cell precursors. However, stromal cell activation in tumors resembles in several aspects the mesenchymal rearrangement which normally occurs during reparative processes such as wound healing. Mesenchymal stem cells (MSCs) play a crucial role in developmental and reparative processes and have extraordinary proangiogenic potential, on the basis of which they are thought to show great promise for the treatment of ischemic disorders. Here, we show that MTCs have proangiogenic potential and that they share the transcriptional expression of the best-known proangiogenic factors with MSCs. We also found that MTCs and MSCs have the same molecular signature for stemness-related genes, and that when co-implanted with cancer cells in syngeneic animals MSCs determine early tumor appearance, probably by favoring the angiogenic switch. Our data (1) reveal crucial aspects of the proangiogenic phenotype of MTCs, (2) strongly suggest their stem origin and (3) signal the risk of therapeutic use of MSCs in tumorpromoting conditions.

These results will allow the use of conventional OI devices for the in vivo study of glucose metabolism in cancer and the assessment, for example, of anti-cancer drugs. Moreover, this demonstrates that (18)F-FDG can be employed as it is a bimodal tracer for PET and OI techniques.

Near-infrared (NIR) fluorescence light has been applied to monitor several biological events in vivo since it penetrates tissues more efficiently than visible light. Dyes exhibiting NIR fluorescence and having large Stokes shift are key elements for this promising optical imaging technology. Here, we report the synthesis of a novel conjugate between a near-infrared indocyanine dye and an organic polyamine polymer (polyethylenimine, PEI) (IR820-PEI) with high chemical stability and good optical properties. IR820-PEI absorbs at 665 nm, emits at 780 nm, and displays a large Stokes shift (115 nm). Moreover, the reported conjugate is able to bind DNA, and the delivery process can be monitored in vivo with noninvasive optical imaging techniques. These characteristics make IR820-PEI one of the most effective and versatile indocyanine dye polymeric-conjugate reported so far.