Calibration Test of PET Scanners in a Multi-Centre Clinical Trial on Breast Cancer Therapy Monitoring Using 18F-FLT

A multi-centre trial using PET requires the analysis of images acquired on different systems We designed a multi-centre trial to estimate the value of 18F-FLT-PET to predict response to neoadjuvant chemotherapy in patients with newly diagnosed breast cancer. A calibration check of each PET-CT and of its peripheral devices was performed to evaluate the reliability of the results.

Material and Methods

11 centres were investigated. Dose calibrators were assessed by repeated measurements of a 68Ge certified source. The differences between the clocks associated with the dose calibrators and inherent to the PET systems were registered. The calibration of PET-CT was assessed with an homogeneous cylindrical phantom by comparing the activities per unit of volume calculated from the dose calibrator measurements with that measured on 15 Regions of Interest (ROIs) drawn on 15 consecutive slices of reconstructed filtered back-projection (FBP) images. Both repeatability of activity concentration based upon the 15 ROIs (ANOVA-test) and its accuracy were evaluated.

Results

There was no significant difference for dose calibrator measurements (median of difference −0.04%; min = −4.65%; max = +5.63%). Mismatches between the clocks were less than 2 min in all sites and thus did not require any correction, regarding the half life of 18F. For all the PET systems, ANOVA revealed no significant difference between the activity concentrations estimated from the 15 ROIs (median of difference −0.69%; min = −9.97%; max = +9.60%).

Conclusion

No major difference between the 11 centres with respect to calibration and cross-calibration was observed. The reliability of our 18F-FLT multi-centre clinical trial was therefore confirmed from the physical point of view. This type of procedure may be useful for any clinical trial involving different PET systems.     

Aggressive and neutral interventions in conflicts in captive groups of brown lemurs (Eulemur fulvus fulvus)

Third-party interventions in conflicts have revealed complexity in primate social relationships. This type of intervention has seldom been analyzed in prosimians, although many of these species exhibit complex (multimale/multifemale) social organizations. The present study on captive brown lemurs (Eulemur fulvus fulvus) shows that dominant individuals were more likely to intervene in conflicts. Both males and females intervened aggressively in conflicts. Female aggressive interventions occurred mainly on behalf of close kin, whereas males mainly intervened on behalf of juveniles. This study also provides the first record of neutral or peaceful interventions in lemurs. Although females intervened neutrally, almost all neutral interventions were by dominant males. Dominant males intervened in conflicts neutrally more often than aggressively, principally in conflicts between adults and juveniles or between juveniles. Neutral interventions by males always ended the conflicts and were often followed by affiliative contacts between participants (intervenors and opponents). In lemurs, female interventions can be explained by kin selection, while the nature of dominant males' interventions suggests a control role. Interventions by males on behalf of juveniles may increase the formers' fitness.     

Engineering Escherichia coli to improve culture performance and reduce formation of by-products during recombinant protein production under transient intermittent anaerobic conditions

Three E. coli strains, named VAL22, VAL23, and VAL24, were engineered at the level of mixed-acid fermentation pathways to improve culture performance under transient anaerobic conditions. VAL22 is a single mutant with an inactivated poxB gene that codes for pyruvate oxidase which converts pyruvate to acetate. VAL23 is a double mutant unable to produce lactate and formate due to deletions of the ldhA and pflB genes that code for lactate dehydrogenase and pyruvate-formate lyase, respectively. VAL24 is a triple mutant with ldhA and pflB deleted and poxB inactivated. Engineered strains were cultured under oscillating dissolved oxygen tension (DOT) in a scale-down system, to simulate gradients occurring in large-scale bioreactors. Kinetic and stoichiometric parameters of constant (10%) and oscillating DOT cultures of the engineered strains were compared with those of the parental strain, W3110. All strains expressed recombinant green fluorescent protein (GFP) as a protein model. Mutant strains showed improved specific growth rate, reduced by-product formation, and reduced specific glucose uptake rate compared to the parental strain, when cultured under oscillating DOT. In particular, lactate and formate production was abolished and acetate accumulation was reduced by 9-12%s. VAL24 showed the best performance, as specific growth and GFP production rates, and maximum GFP concentration were not affected by DOT gradients and were at least twofold higher than those of W3110 under constant DOT. Under oscillating DOT, VAL24 wasted about 40% less carbon into fermentation by-products than W3110. It was demonstrated that, although E. coli responds rapidly to DOT fluctuations by deviating to fermentative metabolism, such pathways can be eliminated as they are not necessary for bacterial survival during the short circulation times typical of large-scale cultures. The approach shown here opens new possibilities for designing metabolically engineered strains, with reduced sensitivity to DOT gradients and improved performance under typical conditions of large-scale cultures.     

Parallel screening and optimization of protein constructs for structural studies

A major challenge in structural biology remains the identification of protein constructs amenable to structural characterization. Here, we present a simple method for parallel expression, labeling, and purification of protein constructs (up to 80 kDa) combined with rapid evaluation by NMR spectroscopy. Our approach, which is equally applicable for manual or automated implementation, offers an efficient way to identify and optimize protein constructs for NMR or X‐ray crystallographic investigations.     

Effects of nutritional antioxidants on AAPH- or AGEs-induced oxidative stress in human SW872 liposarcoma cells

High levels of oxidative stress were reported in obesity-linked type 2 diabetes and were associated with elevated formation of advanced glycation end products (AGEs). Many studies have focused on the effect of antioxidants on vascular and circulating cells such as macrophages. However, despite the major role of adipocytes in the etiology of diabetes, little is known about the effect of natural antioxidants on adipocyte response to oxidative stress. The present study reports the differential protective effects of plant nutrients toward adipose cells subjected to oxidative stress. Caffeic acid, quercetin, l-ascorbic acid, and α-tocopherol were tested on SW872 liposarcoma cells subjected to a free radical generator or to AGEs. Proliferation, viability, free radical formation, and superoxide dismutase expression were assessed in treated cells. Caffeic acid and quercetin appeared as the most potent antioxidant nutrients. Our findings clearly show a novel antioxidant role for caffeic acid and quercetin at the adipose tissue level. These new data confirm the beneficial role of phytotherapy as an interesting alternative mean for the development of novel therapeutical and nutritional strategy to prevent metabolic disorders inherent to obesity-linked diabetes.     

Specific ethanol production rate in ethanologenic Escherichia coli strain KO11 Is limited by pyruvate decarboxylase

Modification of ethanol productivity and yield, using mineral medium supplemented with glucose or xylose as carbon sources, was studied in ethanologenic Escherichia coli KO11 by increasing the activity of five key carbon metabolism enzymes. KO11 efficiently converted glucose or xylose to ethanol with a yield close to 100% of the theoretical maximum when growing in rich medium. However, when KO11 ferments glucose or xylose in mineral medium, the ethanol yields decreased to only 70 and 60%, respectively. An increase in GALP(Ec) (permease of galactose-glucose-xylose) or PGK(Ec) (phosphoglycerate kinase) activities did not change xylose or glucose and ethanol flux. However, when PDC(Zm) (pyruvate decarboxylase from Zymomonas mobilis) activity was increased 7-fold, the yields of ethanol from glucose or xylose were increased to 85 and 75%, respectively, and organic acid formation rates were reduced. Furthermore, as a response to a reduction in acetate and ATP yield, and a limited PDC(Zm) activity, an increase in PFK(Ec) (phosphofructokinase) or PYK(Bs) (pyruvate kinase from Bacillus stearothermophilus) activity drastically reduced glucose or xylose consumption and ethanol formation flux. This experimental metabolic control analysis showed that ethanol flux in KO11 is negatively controlled by phosphofructokinase and pyruvate kinase, and positively influenced by the PDC(Zm) activity level.     

Peroxisome proliferator-activated receptor gamma activators inhibit interleukin-12 production in murine dendritic cells

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear receptor superfamily. They are divided into three subtypes (alpha, beta or delta, and gamma) and are involved in lipid and glucose homeostasis and in the control of inflammation. In this study, we analyzed the expression of PPARs in murine dendritic cells (DCs), the most potent antigen presenting cells. We find that immature as well as mature spleen-derived DCs express PPARgamma, but not PPARalpha, mRNA and protein. We also show that the PPARgamma activator rosiglitazone does not interfere with the maturation of DCs in vitro nor modifies their ability to activate naive T lymphocytes in vivo. Finally, we present evidence that PPARgamma activators down-modulate the CD40-induced secretion of interleukin-12, a potent Th1-driving factor. These data suggest a possible role for PPARgamma in the regulation of immune responses.