Intrinsic polarization of Wolf-Rayet stars due to the rotational modulation of the stellar wind

Context. Fast rotating Wolf-Rayet stars are expected to be progenitors of long duration gamma-ray bursts. However, the observational test of this model is problematic. Spectral lines of Wolf-Rayet stars originate in expanding stellar wind, therefore a reliable spectroscopical determination of their rotational velocities is difficult. Intrinsic polarization of Wolf-Rayet stars due to the rotational modulation of the stellar wind may provide an indirect way to determine the rotational velocities of these stars. However, detailed wind models are required for this purpose. Aims. We determine the intrinsic polarization of Wolf-Rayet stars from hydrodynamical wind models as a function of rotational velocity. Methods. We used 2.5D hydrodynamical simulations to calculate the structure of rotating winds of Wolf-Rayet stars. The simulations account for the deformation of the stellar surface due to rotation, gravity darkening, and nonradial forces. From the derived models, we calculated the intrinsic stellar polarization. The mass loss rate was scaled to take realistic wind densities of Wolf-Rayet stars into account. Results. The hydrodynamical wind models predict a prolate wind structure, which leads to a relatively low level of polarization. Even relatively large rotational velocities are allowed by observational constrains. The obtained wind structure is similar to that obtained previously for rotating optically thin winds. Conclusions. Derived upper limits of rotational velocities of studied Wolf-Rayet stars are not in conflict with the model of long duration gamma-ray bursts

Multicenter assessment of animal-free collagenase AF-1 for human islet isolation

Animal-free (AF) SERVA Collagenase AF-1 and Neutral Protease (NP) AF GMP Grade have recently become available for human islet isolation. This report describes the initial experiences of 3 different islet transplant centers. Thirty-four human pancreases were digested using 1 vial of the 6 different lots of Collagenase AF-1 (2,000-2,583 PZ-U/vial) supplemented with 4 different lots of NP AF in a range of 50 to 160 DMC-U per pancreas. Isolation, culture, and quality assessment were performed using standard techniques as previously described. All data are presented as mean ± standard error of the mean (SEM). Variability of pancreas weight was associated with a wide range of collagenase and NP activities, ranging from 12.7 to 46.6 PZ-U/g (26.0 ± 1.5 PZ-U/g) and 0.4 to 3.0 DMC-U/g (1.5 ± 0.1 DMC-U/g), respectively. Postpurification islet yield was 296,494 ± 33,620 islet equivalents (IEQ) equivalent to 3,274 ± 450 IEQ/g with a purity of 55.9% ± 3.2%. Quality assessment performed after 2 to 4 d of culture demonstrated a viability of 88.1% ± 1.5% and a stimulation index of 3.7 ± 0.7. Eighteen of the 34 preparations were transplanted into type 1 diabetic patients equivalent to a transplantation rate of 52.9%. Six preparations, which were infused into patients as first transplant, could be analyzed and increased the fasting C-peptide level from 0.11 ± 0.08 pretransplant to 1.23 ± 0.24 and 2.27 ± 0.31 ng/mL 3 and 6 mo posttransplant ( P < 0.05), respectively. Insulin requirements were simultaneously reduced at the same time from 39.2 ± 3.8 IU/d before transplantation to 10.8 ± 4.1 and 4.0 ± 2.3 IU/d, after 3 and 6 mo posttransplant ( P < 0.05), respectively. This study demonstrates the efficiency of AF SERVA Collagenase AF-1 and NP AF for clinical islet isolation and transplantation. The new plant-based production process makes these products a safe new option for the islet field