Abstract 2780: Unique pharmacodynamic properties conferred by differential binding to BTK, pirtobrutinib vs covalent inhibitors

Covalent Bruton tyrosine kinase inhibitors (cBTKi) have transformed the treatment of B cell malignancies. Despite the efficacy of cBTKi, treatment failure often occurs through development of resistance or intolerance. Pirtobrutinib, a highly selective, non-covalent BTKi, potently inhibits both WT and C481 mutant BTK. Pirtobrutinib has favorable oral pharmacology, is well tolerated, and has shown promising efficacy in patients with poor prognosis B cell malignancies following prior therapy, including prior cBTKi. Here we report in vitro BTK binding, conformation, and activation differences between cBTKi and pirtobrutinib. Cellular studies showed pirtobrutinib inhibited BTK phosphorylation at both Y223 and Y551 in REC-1 and Ramos A1 human lymphoma cell lines. In contrast, despite inhibition of Y223 phosphorylation, both cell lines treated with cBTKi, ibrutinib, acalabrutinib or zanubrutinib, retained Y551 phosphorylation. The differential effects on Y551 were also observed in PBMC isolated from treatment naïve human CLL donors treated in vitro with pirtobrutinib or ibrutinib. To investigate the binding effects of cBTKi and pirtobrutinib on BTK stability and conformation, a series of biophysical and structural studies were performed. In a hydrogen/deuterium exchange mass spectrometry study using full length BTK, all compounds significantly inhibited exchange in regions surrounding the ATP binding site in the kinase domain. While cBTKi induced significantly increased exchange for peptides in the SH3 and SH2 domains, pirtobrutinib significantly reduced exchange in a portion of the SH3 domain, nearly the entire SH2 domain, and SH2 linker, suggesting that pirtobrutinib uniquely stabilizes BTK in a closed/inactive conformation. Consistent with this proposed model, crosslinking mass spectrometry results of inhibitor bound BTK showed that pirtobrutinib promoted different interactions between the SH2 domain and kinase domain than cBTKi. To confirm that pirtobrutinib promotes greater stabilization of BTK, a mass spectrometry based cellular thermal shift assay was performed in both Ramos and BTK overexpressing HEK293 cells. In both cell lines, pirtobrutinib showed significantly greater stabilization of BTK compared to cBTKi. In addition, crystallographic studies of BTK in complex with pirtobrutinib revealed domain organization consistent with stabilized SH2-SH3 interactions with the kinase domain. These data suggest pirtobrutinib may differentially impact BTK stability and conformation compared to cBTKi. The cellular and biophysical data are consistent with a model in which cBTKi shift BTK toward an open conformation, whereas pirtobrutinib allosterically stabilizes a closed BTK conformation, preventing activation by upstream kinases. Additional studies are underway to further characterize the differential effects of pirtobrutinib on BTK conformation.

Citation Format: Joshua A. Ballard, Kevin Ebata, Hetal S. Randeria, Garrett Tinline, Thomas Lee, Lauren M. Hanson, John A. Latham, E. Peder Cedervall, Jenny Chong, Kyle B. Del Valle, Bernard C. Collins, Tony H. Morales, Thomas C. Benedict, Marc A. Schureck, Ethan T. Bender, Christopher Mendoza, David Molina, Meagan Nakamoto, Hsiao-Chiao Shiah, Hao Xu, Alfonso Espada, Leticia Cano, Charles K. Allerston, Paul Schnier, Barbara J. Brandhuber. Unique pharmacodynamic properties conferred by differential binding to BTK, pirtobrutinib vs covalent inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2780.

Health-related quality of life of adolescents living with HIV treated at the HIV Clinic at the National Institute of Pediatrics at Mexico City

Introduction

ATR for children has successfully increase survival to adolescence. Health-related quality of life (HRQoL) is relevant to evaluate the impact of the disease on well-being in adolescents living with HIV (ALH). Kidscreen-52 questionnaire is validated in mexican adolescents to measure HRQoL

Objectives

To evaluate health related quality of life in a sample of 22 mexican ALH

Methods

A sample of ALH in treatment at the HIV Clinic during 2021, were evaluated with Kidscreen-52 by a child psychiatrist. Statistics included non parametric tests and Cohen “d” and “r” size effect to compare T means between ALH and Kidscreen-52 standardized scores.

Results

Mean age:14.4+2.5. Gender: 11(50%)boys, 11(50%)girls. ALH showed significantly lower scores in all domains. Girls reported lower scores in physical well-being(p=0.047) and autonomy (p=0.023). Orphan ALH had lower scores in mood and emotions (p=0.021)

KIDSCREEN-52	ALH MEAN/SD	KIDSCREEN-52 MEAN/SD	COHEN’S”d”	“r”
PYSICAL WELL-BEING	18.45+3.9	42.6+6.6	- 4.4	-0. 91
PSYCHOLOGICAL WELL-BEING	23.04+6.03	51.2+8.7	- 3.7	-0. 88
MOOD	25.3+6.13	44.8+7.5	- 2.8	-0. 81
SELF-PERCEPTION	20.27+3.22	47.3+7.6	- 4.6	-0. 91
AUTONOMY	18.09+4.9	46.6+9.4	- 3.8	-0. 88
SOCIAL SUPPORT AND PEERS	24+5.1	51.0+9.4	-3.5	-0. 87
PARENTS AND HOME LIFE	20.95+6.2	48.6+9.4	- 3.4	- 0.86
FINANCIAL RESOURCES	9.04+3.21	44.7+7.3	- 6.3	-0. 95
SCHOOL ENVIROMENT	19.73+7.13	53.3+7.9	- 4.46	-0. 91
SOCIAL ACCEPTANCE	12.91+2.11	46.3+9.6	- 4.8	- 0.92

Conclusions

- HRQoL were significantly lower in ALH. -Girls showed significantly lower scores in physical well-being and autonomy. - ALH orphans showed significantly lower scores in mood and emotions domain

Disclosure

No significant relationships.

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Pilot study of an Alzheimer's disease risk assessment program in a primary care setting

INTRODUCTION

The goal of this study was to pilot a referral-based cognitive screening and genetic testing program for Alzheimer's disease (AD) risk assessment in a primary care setting.

METHODS

Primary care providers (PCPs; N = 6) referred patients (N = 94; M = 63 years) to the Rhode Island Alzheimer's Disease Prevention Registry for apolipoprotein E (APOE) genotyping and cognitive screening. PCPs disclosed test results to patients and counseled them about risk factor modification.

RESULTS

Compared to the Registry as a whole, participants were younger, more likely to be non-White, and had lower cognitive screening scores. Mild cognitive impairment participants correctly reported a higher perceived risk of developing AD. Patients who recalled being counseled about modifiable risk factors were more likely to report positive health behavior changes.

DISCUSSION

A referral-based program for cognitive and genetic AD risk assessment in a primary care setting is feasible, acceptable to patients, and yielded a more demographically diverse sample than an AD prevention registry.

Irradiation dose does not affect male reproductive organ size, sperm storage, and female remating propensity in Ceratitis capitata

The Mediterranean fruit fly Ceratitis capitata is a globally invasive pest, often controlled with the sterile insect technique (SIT). For the SIT, mass-rearing of the target insect followed by irradiation are imperatives. Sterile males are often less able to inhibit female remating and transfer less number of sperm, and even irradiation could affect male reproductive organs, with consequences for their ability to inhibit female remating. On the other hand, male age could affect their ability to modulate female response after mating. Here, we evaluated the quality of the genetic sexing strain Vienna-8-tsl mass-reared in Bioplanta San Juan, Argentina, under laboratory conditions, with regard to: (i) the ability of sterile males irradiated at 100 or 140 Gy to inhibit female remating, in the same day and at 24 h of first copulation; (ii) the ability of 3, 4 or 5 day-old sterile males to inhibit female remating at 24 h of first copulation, and (iii) the effect of a reduction in irradiation doses on the number of sperm stored by females and reproductive organ size in virgin males. Sterile males were better able than wild males to inhibit female remating in the same day of first copulation and as able as wild males 1 day after first copulation. Male age did not affect their ability to inhibit female receptivity. Number of sperm stored by females, testes size and ectodermal accessory glands size were not affected by male identity, while sterile 100 Gy males had larger mesodermal accessory glands than control lab males. A reduction in irradiation dose does not impact any variable measured, except for percentage of sperm-depleted females: females mated with sterile 100 Gy males had lower probabilities to store sperm. The results showed here are very encouraging for tsl Vienna 8 strain reared in Argentina and are discussed in comparison with previous studies in C. capitata female remating with dissimilar results.

Pluripotent Pericycle Cells Trigger Different Growth Outputs by Integrating Developmental Cues into Distinct Regulatory Modules

During post-embryonic development, the pericycle specifies the stem cells that give rise to both lateral roots (LRs) and the periderm, a suberized barrier that protects the plant against biotic and abiotic stresses. Comparable auxin-mediated signaling hubs regulate meristem establishment in many developmental contexts; however, it is unknown how specific outputs are achieved. Using the Arabidopsis root as a model, we show that while LR formation is the main auxin-induced program after de-etiolation, plants with age become competent to form a periderm in response to auxin. The establishment of the vascular cambium acts as the developmental switch required to trigger auxin-mediated periderm initiation. Moreover, distinct auxin signaling components and targets control LR versus periderm formation. Among the periderm-specific-promoting transcription factors, WUSCHEL-RELATED HOMEOBOX 4 (WOX4) and KNAT1/BREVIPEDICELLUS (BP) stand out as their specific overexpression in the periderm results in an increased number of periderm layers, a trait of agronomical importance in breeding programs targeting stress tolerance. These findings reveal that specificity in pericycle stem cell fate is achieved by the integration of developmental cues into distinct regulatory modules.

Remote monitoring of Molten Core-Concrete Interaction experiment with Optical Fibre Sensors & perspectives to improve nuclear safety – DISCOMS project

The DISCOMS project (Distributed Sensing for Corium Monitoring and Safety) aimed at providing innovative solutions not requiring local electrical power supplies, for remote monitoring of a severe nuclear accident. The solutions are based on both long length SPNDs (Self Powered Neutron Detectors) and on distributed OFSs (Optical Fibre Sensors) capable to detect the onset of a severe accident, the corium pouring on the containment building concrete basemat, and its interaction with the concrete floor under the reactor vessel, until it spreads in the core catcher (EPR case). This paper mainly focuses on these last three detection targets achievable with distributed OFSs. It is based on the results of a Molten Core & Concrete Interaction (MCCI) experiment, namely VULCANO, held in June 2018 with a concrete crucible equipped with overall ~ 180 m long optical fibre sensing cables. This small scale experiment (50 kg of prototypical corium) has demonstrated the ability of distributed OFSs to remotely provide useful data during the MCCI run: i) temperature profiles images up to about 580°C (single wavelength Raman DTS reflectometer) until cooling down to room temperature, ii) high spatial-resolution frequency shifts profiles, due to combined (non-selective) strain and temperature influences (Rayleigh OFDR and Brillouin reflectometers), and iii) cables lengths ablated by the corium on sections weakened by the temperature (Raman DTS, Rayleigh OFDR, telecom and photon counting reflectometers).

Predictive and prognostic potential of volume-based metabolic variables obtained by a baseline 18F-FDG PET/CT in breast cancer with neoadjuvant chemotherapy indication

AIM

To investigate the usefulness of metabolic variables using ¹⁸F-FDG PET/CT in the prediction of neoadjuvant chemotherapy (NC) response and the prognosis in locally advanced breast cancer (LABC).

MATERIAL AND METHODS

Prospective study including 67 patients with LABC, NC indication and a baseline ¹⁸F-FDG PET/CT. After breast tumor segmentation, SUV variables (SUVmax, SUVmean and SUVpeak) and volume-based variables, such as metabolic tumor volume (MTV) and total lesion glycolysis (TLG), were obtained. Tumors were grouped into molecular phenotypes, and classified as responders or non-responders after completion of NC. Disease-free status (DFs), disease-free survival (DFS), and overall survival (OS) were assessed. A univariate and multivariate analysis was performed to study the potential of all variables to predict DFs, DFS, and OS.

RESULTS

Fourteen patients were classified as responders. Median±SD of DFS and OS was 43±15 and 46±13 months, respectively. SUV and TLG showed a significant correlation (p<0.005) with the histological response, with higher values in responders compared to non-responders. MTV and TLG showed a significant association with DFs (p=0.015 and p=0.038 respectively). Median, mean and SD of MTV and TLG for patients with DFs were: 8.90, 13.73, 15.10 and 33.78, and 90.54 and 144.64, respectively. Median, mean and SD of MTV and TLG for patients with non-DFs were: 16.72, 29.70 and 31.09 and 90.89, 210.98 and 382.80, respectively. No significant relationships were observed with SUV variables and DFs. Volume-based variables were significantly associated with OS and DFS, although in multivariate analysis only MTV was related to OS. No SUV variables showed an association with the prognosis.

CONCLUSION

Volume-based metabolic variables obtained with ¹⁸F-FDG PET/CT, unlike SUV based variables, were good predictors of both neoadjuvant chemotherapy response and prognosis.

1 μs broadband frequency sweeping reflectometry for plasma density and fluctuation profile measurements

Frequency swept reflectometry has reached the symbolic value of 1 μs sweeping time; this performance has been made possible, thanks to an improved control of the ramp voltage driving the frequency source. In parallel, the memory depth of the acquisition system has been upgraded and can provide up to 200 000 signals during a plasma discharge. Additional improvements regarding the trigger delay determination of the acquisition and the voltage ramp linearity required by this ultra-fast technique have been set. While this diagnostic is traditionally dedicated to the plasma electron density profile measurement, such a fast sweeping rate can provide the study of fast plasma events and turbulence with unprecedented time and radial resolution from the edge to the core. Experimental results obtained on ASDEX Upgrade plasmas are presented to demonstrate the performances of the diagnostic.

Lack of robustness of textural measures obtained from 3D brain tumor MRIs impose a need for standardization

Purpose

Textural measures have been widely explored as imaging biomarkers in cancer. However, their robustness under dynamic range and spatial resolution changes in brain 3D magnetic resonance images (MRI) has not been assessed. The aim of this work was to study potential variations of textural measures due to changes in MRI protocols.

Materials and methods

Twenty patients harboring glioblastoma with pretreatment 3D T1-weighted MRIs were included in the study. Four different spatial resolution combinations and three dynamic ranges were studied for each patient. Sixteen three-dimensional textural heterogeneity measures were computed for each patient and configuration including co-occurrence matrices (CM) features and run-length matrices (RLM) features. The coefficient of variation was used to assess the robustness of the measures in two series of experiments corresponding to (i) changing the dynamic range and (ii) changing the matrix size.

Results

No textural measures were robust under dynamic range changes. Entropy was the only textural feature robust under spatial resolution changes (coefficient of variation under 10% in all cases).

Conclusion

Textural measures of three-dimensional brain tumor images are not robust neither under dynamic range nor under matrix size changes. Standards should be harmonized to use textural features as imaging biomarkers in radiomic-based studies. The implications of this work go beyond the specific tumor type studied here and pose the need for standardization in textural feature calculation of oncological images.

Geometrical Measures Obtained from Pretreatment Postcontrast T1 Weighted MRIs Predict Survival Benefits from Bevacizumab in Glioblastoma Patients

Background

Antiangiogenic therapies for glioblastoma (GBM) such as bevacizumab (BVZ), have been unable to extend survival in large patient cohorts. However, a subset of patients having angiogenesis-dependent tumors might benefit from these therapies. Currently, there are no biomarkers allowing to discriminate responders from non-responders before the start of the therapy.

Methods

40 patients from the randomized GENOM009 study complied the inclusion criteria (quality of images, clinical data available). Of those, 23 patients received first line temozolomide (TMZ) for eight weeks and then concomitant radiotherapy and TMZ. 17 patients received BVZ+TMZ for seven weeks and then added radiotherapy to the treatment. Clinical variables were collected, tumors segmented and several geometrical measures computed including: Contrast enhancing (CE), necrotic, and total volumes; equivalent spherical CE width; several geometric measures of the CE ‘rim’ geometry and a set of image texture measures. The significance of the results was studied using Kaplan-Meier and Cox proportional hazards analysis. Correlations were assessed using Spearman correlation coefficients.

Results

Kaplan-Meier and Cox proportional hazards analysis showed that total, CE and inner volume (p = 0.019, HR = 4.258) and geometric heterogeneity of the CE areas (p = 0.011, HR = 3.931) were significant parameters identifying response to BVZ. The group of patients with either regular CE areas (small geometric heterogeneity, median difference survival 15.88 months, p = 0.011) or those with small necrotic volume (median survival difference 14.50 months, p = 0.047) benefited substantially from BVZ.

Conclusion

Imaging biomarkers related to the irregularity of contrast enhancing areas and the necrotic volume were able to discriminate GBM patients with a substantial survival benefit from BVZ. A prospective study is needed to validate our results.

Glioblastoma: does the pre-treatment geometry matter? A postcontrast T1 MRI-based study

BACKGROUND

The potential of a tumour's volumetric measures obtained from pretreatment MRI sequences of glioblastoma (GBM) patients as predictors of clinical outcome has been controversial. Mathematical models of GBM growth have suggested a relation between a tumour's geometry and its aggressiveness.

METHODS

A multicenter retrospective clinical study was designed to study volumetric and geometrical measures on pretreatment postcontrast T1 MRIs of 117 GBM patients. Clinical variables were collected, tumours segmented, and measures computed including: contrast enhancing (CE), necrotic, and total volumes; maximal tumour diameter; equivalent spherical CE width and several geometric measures of the CE "rim". The significance of the measures was studied using proportional hazards analysis and Kaplan-Meier curves.

RESULTS

Kaplan-Meier and univariate Cox survival analysis showed that total volume [p = 0.034, Hazard ratio (HR) = 1.574], CE volume (p = 0.017, HR = 1.659), spherical rim width (p = 0.007, HR = 1.749), and geometric heterogeneity (p = 0.015, HR = 1.646) were significant parameters in terms of overall survival (OS). Multivariable Cox analysis for OS provided the later two parameters as age-adjusted predictors of OS (p = 0.043, HR = 1.536 and p = 0.032, HR = 1.570, respectively).

CONCLUSION

Patients with tumours having small geometric heterogeneity and/or spherical rim widths had significantly better prognosis. These novel imaging biomarkers have a strong individual and combined prognostic value for GBM patients.

KEY POINTS

• Three-dimensional segmentation on magnetic resonance images allows the study of geometric measures. • Patients with small width of contrast enhancing areas have better prognosis. • The irregularity of contrast enhancing areas predicts survival in glioblastoma patients.

Tumour heterogeneity in glioblastoma assessed by MRI texture analysis: a potential marker of survival

OBJECTIVE:

The main objective of this retrospective work was the study of three-dimensional (3D) heterogeneity measures of post-contrast pre-operative MR images acquired with T₁ weighted sequences of patients with glioblastoma (GBM) as predictors of clinical outcome.

METHODS:

79 patients from 3 hospitals were included in the study. 16 3D textural heterogeneity measures were computed including run-length matrix (RLM) features (regional heterogeneity) and co-occurrence matrix (CM) features (local heterogeneity). The significance of the results was studied using Kaplan-Meier curves and Cox proportional hazards analysis. Correlation between the variables of the study was assessed using the Spearman's correlation coefficient.

RESULTS:

Kaplan-Meyer survival analysis showed that 4 of the 11 RLM features and 4 of the 5 CM features considered were robust predictors of survival. The median survival differences in the most significant cases were of over 6 months.

CONCLUSION:

Heterogeneity measures computed on the post-contrast pre-operative T₁ weighted MR images of patients with GBM are predictors of survival.

ADVANCES IN KNOWLEDGE:

Texture analysis to assess tumour heterogeneity has been widely studied. However, most works develop a two-dimensional analysis, focusing only on one MRI slice to state tumour heterogeneity. The study of fully 3D heterogeneity textural features as predictors of clinical outcome is more robust and is not dependent on the selected slice of the tumour.

Prevalence of in vitro susceptibility to carbapenems among clinical isolates of the Bacteroides fragilis group from a Colombian tertiary hospital

Clinical isolates of the Bacteroides fragilis group (n=29) were collected from patients attending a tertiary care hospital in Medellin, Colombia, during 2012 and were tested for susceptibility to four carbapenems using the Clinical and Laboratory Standards Institute (CLSI) Etest method. Overall rates of percent susceptibility were as follows: meropenem, 93.1%; imipenem, 100%; ertapenem, 96.6%; and doripenem, 93.1%. This is the first study to show rates of resistance of Bacteroides spp. to carbapenems in Colombia among a species formerly thought to be fully susceptible to this type of antimicrobial.

Urinary neutrophil gelatinase-associated lipocalin after kidney transplantation: is it a good biomarker to assess delayed graft function?

Delayed graft function (DGF) is a common complication after transplantation. Its incidence is increased among patients receiving a graft from an expanded-criteria donor. Urinary neutrophil gelatinase-associated lipocalin (uNGAL), an acute kidney injury marker, could in the first days after transplantation be an early marker of DGF. We collected urine samples from 38 renal transplant recipients on days 1, 3, 6, and 10 post-transplantation, and months 1 and 6 creatinine to determine uNGAL, serum creatinine, Cystatin C, and albumin/creatinine ratio. We divided the patients into 2 groups, based on whether they developed DGF. We observed that mean uNGAL concentrations, Cystatin C, serum creatinine, and albumin/creatinine ratio were significantly lower in the non-DGF cohort on all measured days. uNGAL at day 3 showed a positive correlation with serum creatinine at day 10 (R = 0.58; P < .00) and day 30 (R = 0.57; P = .016) as well as with the length of hospital stay (r = 0.47; P < .00). Receiver operating characteristic analyses performed to assess the potential of uNGAL to predict DGF showed an area under the curve for day 3 of uNGAL of 0.917 (confidence interval [CI], 0.79-1.00; P = .00), with an optimal cutoff level of 124 ng/mL, sensitivity of 80% (CI, 62%-97%), and specificity of 83% (62%-104%; P = .001). In the first days after transplantation, uNGAL could be an early marker of DGF, providing additional information to standard biomarkers and potentially helping clinicians to take early measures to mitigate DGF.

Relationship of cellular topoisomerase IIα inhibition to cytotoxicity and published genotoxicity of fluoroquinolone antibiotics in V79 cells

Fluoroquinolone (FQ) antibiotics are bacteriocidal through inhibition of the bacterial gyrase and at sufficient concentrations in vitro, they can inhibit the homologous eukaryotic topoisomerase (TOPO) II enzyme. FQ exert a variety of genotoxic effects in mammalian systems through mechanisms not yet established, but which are postulated to involve inhibition of TOPO II enzymes. To assess the relationship of inhibition of cell nuclear TOPO II to cytotoxicity and reported genotoxicity, two FQ, clinafloxacin (CLFX) and lomefloxacin (LOFX), having available genotoxicity data showing substantial differences with CLFX being more potent than LOFX, were selected for study. The relative inhibitory activities of these FQ on nuclear TOPO IIα in cultured Chinese hamster lung fibroblasts (V79 cells) over dose ranges and at equimolar concentrations were assessed by measuring nuclear stabilized cleavage complexes of TOPO IIα-DNA. Cytotoxicity was measured by relative cell counts. Both FQ inhibited V79 cell nuclear TOPO IIα. The lowest-observed-adverse-effect levels for TOPO IIα inhibition were 55 μM for CLFX, and 516 μM for LOFX. The no-observed-adverse-effect-levels were 41 μM for CLFX, and 258 μM for LOFX. At equimolar concentrations (175 μM), CLFX was more potent than LOFX. Likewise, CLFX was more cytotoxic than LOFX. Thus, the two FQ, inhibited TOPO IIα in intact V79 cells, differed in their potencies and exhibited no-observed-adverse-effect levels. These findings are in concordance with published genotoxicity data and observed cytotoxicity.

Failure of silicone gel breast implants: is the mechanical weakening due to shell swelling a significant cause of prostheses rupture?

Silicone gel-filled breast implants nowadays are commonly used in breast surgery. Despite the improvements carried out during the years in the device design and manufacturing technologies, the long-term reliability of such prostheses is still doubted and the phenomena involved in the prostheses failure not yet clearly defined. This study investigates rupture causes by analysing the mechanical properties of failed and intact implants in the recent generation of silicon gel breast implants. The main scope is to assess whether mechanical weakness of the shells should be considered as a major cause of breast implant rupture or, on the contrary, the prosthesis shell damage is likely due to other random factors. Some tests were performed on the shells of a wide number of explanted prostheses, to evaluate the mechanical properties as a function of prostheses status at explantation (intact/ruptured) and variable degree of swelling. A weakening of the shell mechanical properties, so as a significant difference in the ultimate strength and stiffness of intact versus ruptured prostheses, was found. This attenuation of the properties may be justified as a consequence of the shell swelling phenomenon during implantation and has to be considered as a significant mechanism for silicone gel breast implant failure.

Fast sweeping reflectometry upgrade on Tore Supra

In order to study the temporal dynamics of turbulence, the sweep time of our reflectometry has been shortened from 20 to 2 μs with 1 μs dead time. Detailed technical aspects of the upgrade are given, namely, about the stability of the ramp generation, the detection setup, and the fast acquisition module. A review of studies (velocity measurement of the turbulence, modifications of the wavenumber spectrum, radial mapping of correlation time, etc.) offered by such improvements is presented.

Redistribution of suprathermal electrons due to fishbone frequency jumps

MHD instabilities driven by fast electrons identified as fishbonelike modes have been detected on Tore Supra during lower hybrid current drive discharges. Direct experimental evidence is reported of a novel feature: the regular redistribution of suprathermal electrons toward external tokamak regions which are correlated to periodic mode frequency jumps. Sharp drops of the electron temperature time trace are factually linked to the cyclical deterioration of the fast electron confinement.

Demonstration of effective control of fast-ion-stabilized sawteeth by electron-cyclotron current drive

In a tokamak plasma, sawtooth oscillations in the central temperature, caused by a magnetohydrodynamic instability, can be partially stabilized by fast ions. The resulting less frequent sawtooth crashes can trigger unwanted magnetohydrodynamic activity. This Letter reports on experiments showing that modest electron-cyclotron current drive power, with the deposition positioned by feedback control of the injection angle, can reliably shorten the sawtooth period in the presence of ions with energies >or=0.5 MeV. Certain surprising elements of the results are evaluated qualitatively in terms of existing theory.

Biochemical characterization of recombinant hepatitis C virus nonstructural protein 4B: evidence for ATP/GTP hydrolysis and adenylate kinase activity

While nonstructural protein 4B (NS4B) from hepatitis C virus (HCV) is absolutely required for viral propagation, a full understanding of the enzymatic properties of this protein is lacking. Previous studies suggest that NS4B is located at the endoplasmic reticulum and that the protein structure consists of four central transmembrane domains with the N- and C-termini located in the cytoplasm of the host cell. To characterize the enzymatic activity of NS4B, the full-length protein with a C-terminal His tag was expressed in Sf9 insect cells and stabilized with nonionic detergents during purification. Chemical cross-linking experiments using GTP-gamma-azidoanilide and ATP-gamma-azidoanilide and equilibrium binding analyses with GTPgammaS and ATPgammaS show that both GTP and ATP are bound by NS4B, with ATP displaying a higher affinity. Analyses of enzymatic reactions catalyzed by NS4B indicate that the terminal phosphate groups of ATP, GTP, and GDP are removed to produce ADP, GDP, and GMP, respectively. The k(cat) for hydrolysis of GTP by purified NS4B compared favorably with the k(cat) for hydrolysis of GTP by Ras-p21 in the absence of GTPase activating proteins (GAPs). In addition to the hydrolysis of NTP and NDP substrates, adenylate kinase activity was detected in purified preparations of NS4B with the reverse reaction 2ADP --> ATP + ADP, yielding a larger k(cat) compared to that of the forward reaction ATP + AMP --> 2ADP. These studies suggest that HCV NS4B possesses both adenylate kinase activity and nucleotide hydrolase activity. Mutation of amino acids in the Walker A and B motifs of NS4B resulted in decreased affinity for both GTPgammaS and ATPgammaS as well as decreased ATP hydrolysis and AK activity.

Self-Assembly of Methacrylic Nanostructured Copolymers Containing Polyhedral Oligomeric Silsesquioxanes

Two hybrid copolymer series obtained by free-radical copolymerization of methacrylcyclohexyl Polyhedral oligomeric silsesquioxane (POSS) with butyl methacrylate or 2-ethylhexylmethacrylate were characterized by 1H-NMR spectroscopy, gel permeation chromatography (GPC), X-rays Diffraction (XRD), differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). Reactivity ratios were calculated by low yield composition data suggesting the formation of random copolymers with low probability of poly-POSS sequences. XRD studies showed the crystallization behaviour of the inorganic phase independently on the POSS content; however sample processing by solvent casting effectively hindered the copolymer self-assembling ability. DSC suggests the formation of polyphasic structures with Tg increasing with POSS content, and with endothermal peaks occurring at higher temperature. Finally TGA shows an improved thermal stability of hybrid copolymers with char yield correlated to the level of inorganic phase.

Dipyridamole promotes changes in calbindin-D28k and tyrosine hydroxylase expression in neonatal rats

BACKGROUND

Perinatal hypoxia alters the concentration of many neurochemicals in the brain, including adenosine, and promotes central nervous system (CNS) disorders in human infants such as periventricular leukomalacia or encephalopathy.

OBJECTIVE

Using the postnatal rat as a model of perinatal human development, we examined the effects of sustained increases in brain adenosine on CNS regions thought to be involved with both planning and execution of motor activity.

METHODS

To simulate hypoxia-induced changes in adenosine, Sprague-Dawley rats were injected twice daily from postnatal day (P) 3 to P14, with the adenosine uptake inhibitor dipyridamole (DIP) or the A(1) adenosine receptor agonist N(6)-cyclopentyladenosine (CPA). Vehicle-injected animals served as controls. Immunohistochemical and morphological analyses were then performed to examine the expression of calbindin D-28k (CB) and the thickness of the external granule cell layer (eGL) in the cerebellum. Additionally tyrosine hydroxylase (TH) expression in the caudate putamen and ventricular size were also examined.

RESULTS

In the cerebellum, both DIP and CPA reduced the number of CB-positive Purkinje cells as well as decreased the thickness of the eGL compared to vehicle. In the caudate putamen we found that DIP but not CPA decreased TH expression when compared to vehicle. Neither agent significantly altered ventricular size when compared to vehicle.

CONCLUSIONS

These observations suggest that elevations in brain adenosine, which can occur following hypoxia, leads to both neurochemical and cellular changes in regions of the brain which control the planning and execution of motor activity. Thus, therapeutic strategies that target brain regions most sensitive to adenosine may prevent or control at least some of the CNS damage observed following perinatal hypoxia.