Labeling Human Mesenchymal Stem Cells with Fluorescent Contrast Agents: the Biological Impact

Purpose  

This study aims to determine the effect of human mesenchymal stem cell (hMSC) labeling with the fluorescent dye DiD and the iron oxide nanoparticle ferucarbotran on chondrogenesis.     

Bacterial translation elongation factor EF-Tu interacts and colocalizes with actin-like MreB protein

We show that translation initiation factor EF-Tu plays a second important role in cell shape maintenance in the bacterium Bacillus subtilis. EF-Tu localizes in a helical pattern underneath the cell membrane and colocalizes with MreB, an actin-like cytoskeletal element setting up rod cell shape. The localization of MreB and of EF-Tu is interdependent, but in contrast to the dynamic MreB filaments, EF-Tu structures are more static and may serve as tracks for MreB filaments. In agreement with this idea, EF-Tu and MreB interact in vivo and in vitro. Lowering of the EF-Tu levels had a minor effect on translation but a strong effect on cell shape and on the localization of MreB, and blocking of the function of EF-Tu in translation did not interfere with the localization of MreB, showing that, directly or indirectly, EF-Tu affects the cytoskeletal MreB structure and thus serves two important functions in a bacterium.     

Vimentin cleavage in end-stage renal disease is not related to apoptosis

Anti-vimentin auto-antibodies contribute to chronic allograft nephropathy. They exist in sera of end-stage renal disease patients on hemodialysis (ESRD) already before renal transplantation. We found recently that a 49 kDa vimentin fragment is increased in lymphocytes of ESRD patients which is presented on the cell surface. In vitro studies showed that such a fragment is formed during apoptosis by active caspase-3. We hypothesized that vimentin degradation in leukocytes of ESRD patients correlates to caspase-3 activation in vivo. Lymphocytes and monocytes were isolated from ESRD patients and from healthy volunteers and analyzed for vimentin expression and caspase-3 activation. In addition, apoptosis was induced in vitro and quantified by flow cytometry. ESRD monocytes have shown only the full length 60 kDa vimentin isoform. ESRD lymphocytes, however, showed in addition a strongly increased expression of the 49 kDa vimentin in all samples. Caspase-3 activation was found in 60% of ESRD lymphocytes and 66% of ESRD monocytes but not in healthy volunteers. UV-mediated induction of apoptosis was not associated with vimentin degradation. These experiments could confirm increased vimentin degradation in ESRD lymphocytes. However, we could not validate any correlation to apoptosis.     

Continuously moving table time‐of‐flight angiography of the peripheral veins

Time‐of‐flight (TOF) MR angiography allows for noninvasive vessel imaging. To overcome the limited volumetric coverage of standard TOF techniques, the aim of this study was to investigate the combination of TOF and continuously moving table (CMT) acquisitions for peripheral vein imaging based on image subtraction. Two acquisition strategies are presented: a simple two‐step method based on 2‐fold CMT acquisition and an advanced one‐step method requiring only one continuous scan. Image quality of both CMT TOF techniques was evaluated by semiquantitative image grading and by signal‐to‐noise ratio and contrast‐to‐noise ratio analysis for veins of the upper and lower leg in 10 healthy volunteers. Results were compared to a standard stationary two‐dimensional (2D) TOF multistation acquisition. Image grading revealed good image quality for both CMT TOF methods, thereby confirming the feasibility of axial 2D CMT TOF to assess the veins of the lower extremities during a single scan. Quantitative evaluation showed no significant difference in signal‐to‐noise ratio and contrast‐to‐noise ratio compared to the stationary experiment. Additional measurements in three patients with postthrombotic changes and varicosities demonstrated the clinical applicability of the presented methods. CMT TOF provides promising results and permits the detection of various pathologic changes of the venous system. Magn Reson Med 63:1219–1229, 2010. © 2010 Wiley‐Liss, Inc.     

A phosphorylation-dependent intramolecular interaction regulates the membrane association and activity of the tumor suppressor PTEN

The PI 3-phosphatase PTEN (phosphatase and tensin homologue deleted on chromosome 10), one of the most important tumor suppressors, must associate with the plasma membrane to maintain appropriate steady-state levels of phosphatidylinositol 3,4,5-triphosphate. Yet the mechanism of membrane binding has received little attention and the key determinants that regulate localization, a phosphatidylinositol 4,5-bisphosphate (PIP₂) binding motif and a cluster of phosphorylated C-terminal residues, were not included in the crystal structure. We report that membrane binding requires PIP₂ and show that phosphorylation regulates an intramolecular interaction. A truncated version of the enzyme, PTEN_1–351, bound strongly to the membrane, an effect that was reversed by co-expression of the remainder of the molecule, PTEN_352–403. The separate fragments associated in vitro, an interaction dependent on phosphorylation of the C-terminal cluster, a portion of the PIP₂ binding motif, integrity of the phosphatase domain, and the CBR3 loop. Our investigation provides direct evidence for a model in which PTEN switches between open and closed states and phosphorylation favors the closed conformation, thereby regulating localization and function. Small molecules targeting these interactions could potentially serve as therapeutic agents in antagonizing Ras or PI3K-driven tumors. The study also stresses the importance of determining the structure of the native enzyme.     

Behandlungsassoziierte Spätfolgen nach Strahlentherapie maligner Erkrankungen im Kindes- und Jugendalter

BACKGROUND AND PURPOSE: Radiogenic late effects in children and adolescents have been evaluated retrospectively in most analyses, with small patient numbers. The German Group of Pediatric Radiation Oncology (APRO) has generated a concept for a prospective evaluation of radiation-associated late effects in childhood. The aim of this study was to evaluate the feasibility of a nationwide central database for the documentation of radiation parameters and side effects of all children treated within therapy protocols of the German Society of Pediatric Oncology and Hematology (GPOH). PATIENTS AND METHODS: A study center has been implemented in Muenster, the documentation has started in July 2001 in few centers in a pilot phase. Since February 2004 the documentation is done countrywide. Detailed documentation forms have been designed for treatment parameters and for doses applied at organs at risk. Furthermore, a uniform toxicity documentation, according to the RTOG/EORTC criteria, was chosen. Patients were reported from the study centers of the GPOH to the study center. All information was collected and analyzed in the study center. RESULTS: Till July 31, 2005, 438 documentations of radiation and 579 toxicity documentations of side effects have been collected in the study center. 46 centers for radiotherapy in Germany and one center each in Austria and in Switzerland took part in the documentation. The quality of documentation regarding completeness and plausibility fulfilled the expected criteria in most cases. This feasibility analysis showed that important information about organ dose levels and side effects was documented in a large number of patients (Figures 1 and 2). CONCLUSION: This prospective evaluation of radiotherapy and radiogenic side effects in children and adolescents will allow correlating doses at organs at risk and the incidence of acute and late sequelae in Germany. Further documentations and a longer follow-up are necessary to obtain powerful results.     

Social position affects bone mass in childhood through opposing actions on height and weight.

We studied relationships between social position of the mother in pregnancy and bone mass of the child at age 9.9 years. The tendency for social position to increase bone area and bone mass through a positive influence on height was opposed by a negative effect of social position on weight and fat mass. INTRODUCTION: Evidence that social factors influence skeletal growth raises the possibility that bone mass acquisition in childhood is socially determined. MATERIALS AND METHODS: To clarify the role of social factors in bone mass acquisition in childhood, we studied relationships between these variables in the Avon Longitudinal Study of Parents and Children (ALSPAC). Measures of the mother's social position during pregnancy were linked to DXA results obtained at age 9.9 years in 6,702 children. Linear regression analyses were carried out after adjusting for age and gender. Because social position may affect height and weight of the child, analyses were repeated after adjusting for these additional variables. RESULTS: Measures of social position in pregnancy were unrelated to total body BMC in analyses adjusted for age and gender alone. However, after adjusting for height, which was positively related to social position, a strong negative association was observed between BMC and housing tenure (p < 0.001), maternal education (p < 0.001), paternal education (p < 0.001), and social class (p < 0.001). Similar results were obtained for bone area. After adjusting for weight as well as height, an association between social position and BMC and bone area was no longer observed. Hence, social position seems to exert opposing height- and weight-dependent effects on BMC and bone area in childhood. In further analyses, we found that adjusting for fat mass of the child led to similar results to those obtained with weight. CONCLUSIONS: Social position in childhood seems to be positively related to bone mass acquisition in childhood as a consequence of enhanced gain in height (i.e., longitudinal growth). However, this influence is counteracted by the tendency for increased fat deposition in those from a lower social position to increase bone area, presumably reflecting the stimulation of appositional bone growth.