Assessing low laser damage densities of fused silica optics by means of a functional raster scan protocol

The knowledge of the laser damage resistance of fused silica optics for their use in high-power lasers is of primary importance for the operation and maintenance of these facilities. Among the control procedures developed, one of the most relevant to date is the raster scan procedure [Lamaignère et al., Rev. Sci. Instrum. 78, 103105 (2007)]. This procedure is used to determine the damage density of optical components as a function of fluence. To date, this procedure takes into account all triggered damage sites, regardless of their size and/or morphology. We have added a step to this procedure, which consists in irradiating again all the damage sites with a series of shots to ascertain their ability to grow. This allows us to estimate the densities of growing damage sites, which are most critical for the safe operation of lasers. This pragmatic approach can be considered a functional test procedure. By applying this procedure to large optical areas, we were then able to measure extremely low damage densities (∼10-4 damage cm-2) over a wide range of fluences [0-18 J cm-2], corresponding to fluences to which the optics are irradiated during the operation of high-power lasers. We can then determine the damage law of a given set of optical components. This reference law makes it possible, on the one hand, to predict the lifetime of the optics. On the other hand, any deviation can then be analyzed with regard to this reference law. Thanks to the determination of confidence intervals, this functional procedure can also be used to delimit the reference law by upper and lower bounds.

Desmopressin Has No Beneficial Effect on Excessive Postoperative Bleeding or Blood Product Requirements Associated with Cardiopulmonary Bypass

Cardiopulmonary bypass during open-heart surgery is sometimes associated with excessive perioperative bleeding. Following a non-randomized study suggesting that desmopressin acetate (desmopressin) reduced blood product requirements in these patients, we conducted a double-blind, placebo-controlled randomized trial of desmopressin (0.3 µg/kg, i. v.) in 92 patients with overt bleeding and a prolonged bleeding time.

Mean blood loss during the first 24 h post-treatment was similar in the desmopressin and placebo groups (582 vs 465 ml, respectively; p = 0.15). Red-cell (p = 0.76), fresh frozen plasma (r = 0.66) and platelet unit (p = 0.74) requirements were also similar.

The haemostatic effect of desmopressin has been attributed to the release of von Willebrand factor (vWF) and a reduced bleeding time. In our study, vWF and factor VIII :C levels increased while the bleeding time decreased significantly at 90 min and 24 h in both groups and, although vWF and factor VIII: C levels were slightly higher in desmopressin-treated patients at 90 min, the difference was not significant. Thrombin-antithrombin III complex, fibrinogen degradation product and tissue plasminogen activator levels, reflecting activation of the coagulation and fibrinolytic systems, respectively, decreased uniformely in both groups.

We conclude that desmopressin is not useful in reducing blood loss or blood product requirements in patients with excessive immediate postoperative bleeding.

High mTORC1 activity drives glycolysis addiction and sensitivity to G6PD inhibition in acute myeloid leukemia cells

Alterations in metabolic activities are cancer hallmarks that offer a wide range of new therapeutic opportunities. Here we decipher the interplay between mTORC1 activity and glucose metabolism in acute myeloid leukemia (AML). We show that mTORC1 signaling that is constantly overactivated in AML cells promotes glycolysis and leads to glucose addiction. The level of mTORC1 activity determines the sensitivity of AML cells to glycolysis inhibition as switch-off mTORC1 activity leads to glucose-independent cell survival that is sustained by an increase in mitochondrial oxidative phosphorylation. Metabolic analysis identified the pentose phosphate pathway (PPP) as an important pro-survival pathway for glucose metabolism in AML cells with high mTORC1 activity and provided a clear rational for targeting glucose-6-phosphate dehydrogenase (G6PD) in AML. Indeed, our analysis of the cancer genome atlas AML database pinpointed G6PD as a new biomarker in AML, as its overexpression correlated with an adverse prognosis in this cohort. Targeting the PPP using the G6PD inhibitor 6-aminonicotinamide induces in vitro and in vivo cytotoxicity against AML cells and synergistically sensitizes leukemic cells to chemotherapy. Our results demonstrate that high mTORC1 activity creates a specific vulnerability to G6PD inhibition that may work as a new AML therapy.

Anti-Legionella activity of staphylococcal hemolytic peptides

A collection of various Staphylococci was screened for their anti-Legionella activity. Nine of the tested strains were found to secrete anti-Legionella compounds. The culture supernatants of the strains, described in the literature to produce hemolytic peptides, were successfully submitted to a two step purification process. All the purified compounds, except one, corresponded to previously described hemolytic peptides and were not known for their anti-Legionella activity. By comparison of the minimal inhibitory concentrations, minimal permeabilization concentrations, decrease in the number of cultivable bacteria, hemolytic activity and selectivity, the purified peptides could be separated in two groups. First group, with warnericin RK as a leader, corresponds to the more hemolytic and bactericidal peptides. The peptides of the second group, represented by the PSMα from Staphylococcus epidermidis, appeared bacteriostatic and poorly hemolytic.

Perspectives on inhibiting mTOR as a future treatment strategy for hematological malignancies

Mammalian target of rapamycin (mTOR) is a protein kinase implicated in the regulation of various cellular processes, including those required for tumor development, such as the initiation of mRNA translation, cell-cycle progression and cellular proliferation. In a wide range of hematological malignancies, the mTORC1 signaling pathway has been found to be deregulated and has been designed as a major target for tumor therapy. Given that pre-clinical studies have clearly established the therapeutic value of mTORC1 inhibition, numerous clinical trials of rapamycin and its derivates (rapalogs) are ongoing for treatment of these diseases. At this time, although disease stabilization and tumor regression have been observed, objective responses in some tumor types have been modest. Nevertheless, some of the mechanisms underlying cancer-cell resistance to rapamycin have now been described, thereby leading to the development of new strategy to efficiently target mTOR signaling in these diseases. In this review, we discuss the rationale for using mTOR inhibitors as novel therapies for a variety of hematological, malignancies with a focus on promising new perspectives for these approaches.

[Diffusion-weighted MR imaging of liver pathology: principles and clinical applications]

Due to ongoing technological advances, the range of clinical applications for diffusion-weighted MR imaging has expanded to now include abdominal pathology. Current applications for liver pathology include two main directions. First, oncologic imaging with detection, characterization and follow-up of lesions. Second, evaluation of diffuse liver diseases, including hepatic fibrosis. The diagnostic impact and role of diffusion-weighted MR imaging remain under investigation, but appear promising. Because of its short acquisition time, sensitivity, and additional information it provides, diffusion-weighted MR imaging should be included in routine liver imaging protocols.

Universality of solar-wind turbulent spectrum from MHD to electron scales

To investigate the universality of magnetic turbulence in space plasmas, we analyze seven time periods in the free solar wind under different plasma conditions. Three instruments on Cluster spacecraft operating in different frequency ranges give us the possibility to resolve spectra up to 300 Hz. We show that the spectra form a quasiuniversal spectrum following the Kolmogorov's law approximately k(-5/3) at MHD scales, a approximately k(-2.8) power law at ion scales, and an exponential approximately exp[-sqrt[k(rho)e]] at scales k(rho)e approximately [0.1,1], where rho(e) is the electron gyroradius. This is the first observation of an exponential magnetic spectrum in space plasmas that may indicate the onset of dissipation. We distinguish for the first time between the role of different spatial kinetic plasma scales and show that the electron Larmor radius plays the role of a dissipation scale in space plasma turbulence.

Distinct sequences of the glycoprotein Ib-binding domain of von Willebrand factor involved in shear induced platelet aggregation

Shear-induced platelet aggregation (SIPA) requires von Willebrand factor (vWF) binding to the platelet receptors GPIb and alphaIIbbeta3. In order to determine the vW F sequences involved in SIPA at 4000/s, we studied the llb 3 effect of three monoclonal antibodies (mabs) 724, 713 and 328 to the A1 domain of vWF. We found that mab 724 induced an enhanced SIPA via a Fc gamma-receptor independent mechanism. In contrast, mab 713 and mab 328 could inhibit SIPA by 52 and 91% , respectively. Based on distinct effects on SIPA, we can propose the following working model for the interaction between vWF and GPIb: mabs 713 and 328, which block SIPA, may recognize an epitope that is involved in binding to GPIb, whereas mab 724, which increases SIPA in the presence of vWF, may mimic the effect of botrocetin when binding to vWF, by inducing an active conformation of vWF, which may be more sensitive to high shear rate.

Elevated thrombopoietin serum concentrations in myelodysplasias

Thrombopoietin (TPO) serum levels were quantified in patients with myelodysplastic syndromes using an ELISA test for TPO. We found that TPO levels were significantly elevated in the whole group of patients as compared with normal healthy donors (521.9 75.3 pg/ml vs 160.1 19.6 pg/ml; P = 0.011). TPO serum levels were inversely correlated with the megakaryocyte mass in both the RA/RARS and RAEB/RAEBt subgroups ( P = 0.012 and P = 0.031, respectively). Two subsets of patients with a possible dysregulation of TPO production were identified.

[Pineapple juice as a negative oral contrast agent in magnetic resonance cholangiopancreatography]

PURPOSE

The quality of magnetic resonance cholangiopancreatography (MRCP) images is frequently degraded by high signal from the gastrointestinal tract on heavily T2W images. The purpose of this study is to evaluate pineapple juice (PJ) as an oral negative contrast agent in MRCP.

MATERIALS AND METHODS

Results from MRCP in 50 patients with PJ and 50 patients with paramagnetic contrast (ferumoxsil-Lumirem) were compared. Reviewers were blinded to the type of contrast agent. Exam quality was recorded with regards to signal suppression in the stomach, duodenum and proximal small bowel and with regards to pancreatic duct and biliary ducts visualization. In vitro, the signal characteristics of several commercially available brands of PJ were assessed using T1W, T2W and MRCP sequences. Signal intensity was correlated with the manganese concentration measured using atomic absorption spectrometry. Finally, the reviewers compared the taste of PJ and ferumoxsil.

RESULTS

On MRCP sequences, results were similar with regards to signal suppression in the stomach, duodenum and proximal small bowel with PJ and ferumoxsil. Visualization of the pancreatic duct, intrahgepatic bile ducts and CBD was similar with PJ and ferumoxsil. The signal intensity of commercially available brands of PJ on T2W and MRCP sequences correlated well with the measured manganese concentration on spectroscopy. Variations in manganese concentration were observed, with values ranging from 3.65 to 27.24 mg/L. The reviewers noted that PJ tasted "good" or "very good" and that ferumoxsil tasted "bad" or "very bad".

CONCLUSION

Ingestion of PJ provides effective signal suppression in the GI tract on MRCP, similar to paramagnetic contrast agents. Because manganese concentration is highly variable in commercially available PJ brands, a brand with high manganese concentration should be selected.

Imagerie des pathologies thoraciques chez le patient VIH au stade sida

The imaging features of infectious and non-infectious pathologies in HIV patients with AIDS (less than 200 CD4/mm3) are illustrated. Opportunistic infections, tumors and vascular pathologies have variable appearances based on the degree of immunosuppression and patient compliance with opportunistic infection prophylaxis. Because of advances in retroviral treatments and wider use of anti-infectious prophylaxis, thoracic pathologies in AIDS patients are less frequent but must nonetheless be recognized, and diagnosis should be suggested in patients with unknown serologic status.

Intrinsic flexibility and structural adaptability of Plasticins membrane-damaging peptides as a strategy for functional versatility

The Plasticins are a family of antimicrobial, 23-29-residue Gly-Leu-rich ortholog peptides from the frog skin that have very similar amino acid sequences, hydrophobicities, and amphipathicities but differ markedly in their conformational plasticity and spectrum of activity. The intrinsic flexibility and structural malleability of Plasticins modulate their ability to bind to and disrupt the bilayer membranes of prokaryotic and eukaryotic cells, and/or to reach intracellular targets, therefore, triggering functional versatility. The discussion is opened herein on several examples of other membrane-active peptides, like viral fusion peptides, cell-penetrating peptides, that are able to display antimicrobial activity. Hence, Plasticins could be regarded as models of multipotent membrane-active peptides guided by structural plasticity.

Structural malleability of plasticins: Preorganized conformations in solution and relevance for antimicrobial activity

Plasticins (23 long-residue glycine-leucine-rich dermaseptin-related peptides produced by the skin of South American hylids) have very similar amino acid sequences, hydrophobicities, and amphipathicities, but differ in their membrane-damaging properties and structurations (i.e. destabilized helix states, beta-hairpin, beta-sheet, and disordered states) at anionic and zwitterionic membrane interfaces. Structural malleability of plasticins in aqueous solutions together with parameters that may govern their ability to fold within beta-hairpin like structures were analyzed through circular dichroism and FTIR spectroscopic studies completed by molecular dynamics simulations in polar mimetic media. The goal of this study was to probe to which extent pre-existent peptide conformations, i.e. intrinsic "conformational landscape", may be responsible for variability in bioactive conformation and antimicrobial/hemolytic mechanisms of action of these peptides in relation with their various membrane disturbing properties. All plasticins present a turn region that does not always result in folding into a beta-hairpin shaped conformation. Residue at position 8 plays a major role in initiating the folding, while position 12 is not critical. Conformational stability has no major impact on antimicrobial efficacy. However, preformed beta-hairpin in solution may act as a conformational lock that prevents switch to alpha-helical structure. This lock lowers the antimicrobial efficiency and explains subtle differences in potencies of the most active antimicrobial plasticins.

MEFV analysis is of particularly weak diagnostic value for recurrent fevers in Western European Caucasian patients

OBJECTIVE

Familial Mediterranean fever (FMF) is an autosomal-recessive disorder characterized by recurrent attacks of fever, with abdominal, thoracic, or articular pain. FMF is particularly common in Mediterranean populations, while other populations are rarely affected. MEFV gene analysis provides the only objective diagnostic criterion for FMF. However, the spectrum of MEFV mutations, which was first established in classically affected populations, remains insufficiently studied in other populations. The purpose of this study was to assess involvement of MEFV in the phenotype of western European Caucasian patients with a clinical diagnosis of FMF.

METHODS

Mutation analysis was performed in 208 Caucasian patients from western Europe, by screening for the most common MEFV mutations in exons 2, 3, 5, and 10, and by sequencing the promoter region and the whole MEFV coding sequence in 21 of these patients.

RESULTS

None of the patients carried 2 mutated alleles. Only 2 patients carried 1 mutated allele.

CONCLUSION

FMF-like syndromes in western European Caucasian populations cannot be explained by MEFV mutations. These results should be helpful in avoiding laborious and costly MEFV molecular analyses that, at the population level, seem to be of poor diagnostic value in the case of western European Caucasian patients, and rather should prompt a search for other causes in those patients.