Pharmacological Targeting of Interferon-Related DNA Damage Resistant Signature (IRDS) and XRCC4-Mediated DNA Repair Pathways ss a Novel Therapeutic Approach to DIPG Radio-Sensitization

PURPOSE/OBJECTIVE(S)

Despite significant efforts to improve the outcomes of pediatric diffuse midline gliomas, such as diffuse intrinsic pontine glioma (DIPG), prognosis remains dismal with a 5-year survival of <1%. The standard of care treatment for DIPG is fractionated radiation, but the disease inevitably progresses in 6 months or less. There is a significant unmet need to improve the clinical outcomes for pediatric DIPG patients. Approximately 70-80% of DIPG tumors contain mutations in TP53 tumor suppressor protein. These TP53 mutations are associated with resistance to radiation treatments in DIPG patients. The mechanisms of increased radio-resistance of p53-mutant DIPG are poorly understood. The objective of this study was to identify novel pharmacological agents that would augment radiation sensitivity of p53 mutant DIPG cell lines, and to establish their molecular mechanism of action.

MATERIALS/METHODS

SF8628 pediatric DIPG cell line harboring p53 mutation was obtained from MilliporeSigma. CellRad benchtop X-ray irradiator (Precision X-Ray) was used for radiation sensitization experiments. Vi-CELL BLU cell viability analyzer was used for high-throughput screening of small molecule compound libraries with and without radiation treatments. Proteomics Core facility was utilized for mass spec analysis of protein targets of Compound-X.

RESULTS

To identify novel drug candidates that would sensitize DIPG to therapeutic radiation, we carried out an unbiased screen of curated libraries of small molecules with diverse scaffolds in p53 mutant DIPG cells. This radio-sensitization screen yielded a single molecule, Compound-X, that was found to have profound growth-inhibitory and radiation-sensitizing effects in DIPG cells. Compound-X was found to induce a robust cell cycle arrest of DIPG cells in G2/M, the most radio-sensitive phase of the cell cycle. Furthermore, Compound-X elicited a massive apoptotic cell death of DIPG cells. An unbiased RNA sequencing approach revealed that Compound-X inhibits expression of the Interferon-related DNA damage Resistant Signature (IRDS), a sub-group of interferon-stimulated genes (ISGs) known to promote radiation and chemotherapy resistance in high-grade gliomas. To identify the target of Compound-X, we carried out affinity purification of Compound-X associated complexes from p53 mutant DIPG cell lysates. Mass spectrometry analysis of Compound-X-purified protein complexes identified XRCC4 as a protein that uniquely associated with Compound-X. RNAi knock-down experiments revealed that XRCC4 is required for cytotoxic effects of Compound-X. Importantly, Compound-X-mediated XRCC4 targeting caused a delay in DNA DSBs repair after radiation treatment.

CONCLUSION

An unbiased screen of small molecule drug candidates identified a novel XRCC4-targeting agent, Compound-X, as potent radiation sensitizer in p53 mutant DIPG cells. This work may lead to clinical trials investigating novel XRCC4-targeting agent in pediatric patients with DIPG.

Trial in Progress: Adaptive RADiation Therapy with Concurrent Sacituzumab Govitecan (SG) for Bladder Preservation in Patients with MIBC (RAD-SG)

PURPOSE/OBJECTIVE(S)

A substantial proportion of patients with muscle invasive bladder cancer do not receive curative intent therapy, especially if unfit for or refuse radical cystectomy. Concurrent chemoradiation is an effective alternative to radical cystectomy, however systemic radio-sensitizing chemotherapy may have off target side effects. A Phase I study is accruing which will investigate the concurrent administration of a bladder cancer targeted antibody drug conjugate (Sacituzumab Govitecan) with radiotherapy.

MATERIALS/METHODS

This trial in progress is a Phase I study of Adaptive RADiation therapy with concurrent Sacituzumab Govitecan (SG) for bladder preservation in patients with muscle invasive bladder cancer (MIBC). Eligible patients will have localized muscle invasive bladder cancer (MIBC) confined to the bladder. The initial cohort is expected to accrue 20 patients. The primary endpoint is to establish the safety, tolerability, and feasibility of bladder preservation therapy treatment with concurrent SG and adaptive image-guided radiation therapy for patients with localized MIBC. The secondary endpoints are to determine the bladder intact event-free survival (BI-EFS) with concurrent SG and radiation therapy for MIBC and compare to historical controls with other concurrent chemoradiation regimens. BI-EFS is defined as the time from treatment to the first documented occurrence of residual/recurrent MIBC, nodal or distant metastases on imaging, radical cystectomy, or death from any cause. Sacituzumab Govitecan targets TROP-2, a surface protein expressed in urothelial cancers of the bladder. SG will be delivered IV, 10 mg/kg, 21-day cycles for 1 loading cycle prior to radiation and two subsequent cycles with concurrent adaptive radiotherapy over a period of 6 weeks (64 Gy). Correlative objectives (Supported by NCI/NIH U54) and will involve 1) elucidation of the genetic and microenvironmental mechanisms that drive efficacy and resistance to combined ADC plus radiation therapy and 2) characterization of tumor clonal dynamics, immune repertoire editing, and imaging changes following treatment with SG plus radiation.

RESULTS

To be determined.

CONCLUSION

To be determined.

Three-dimensional quantitative muscle ultrasound in patients with facioscapulohumeral dystrophy and myotonic dystrophy

INTRODUCTION/AIMS

Ultrasound imaging of muscle tissue conventionally results in two-dimensional sampling of tissue. For heterogeneously affected muscles, a sampling error using two-dimensional (2D) ultrasound can therefore be expected. In this study, we aimed to quantify and extend ultrasound imaging findings in neuromuscular disorders by using three-dimensional quantitative muscle ultrasound (3D QMUS).

METHODS

Patients with facioscapulohumeral dystrophy (n = 31) and myotonic dystrophy type 1 (n = 16) were included in this study. After physical examination, including Medical Research Council (MRC) scores, the tibialis anterior muscle was scanned with automated ultrasound. QMUS parameters were calculated over 15 cm of the length of the tibialis anterior muscle and were compared with a healthy reference data set.

RESULTS

With 3D QMUS local deviations from the healthy reference could be detected. Significant Pearson correlations (P < .01) between MRC score and QMUS parameters in male patients (n = 23) included the mean echo intensity (EI) (0.684), the standard deviation of EI (0.737), and the residual attenuation (0.841). In 91% of all patients, mean EI deviated by more than 1 standard deviation from the healthy reference. In general, the proportion of muscle tissue with a Z score >1 was about 50%.

DISCUSSION

In addition to mean EI, multiple QMUS parameters reported in this study are potential biomarkers for pathology. Besides a moderate correlation of mean EI with muscle weakness, two other parameters showed strong correlations: standard deviation of EI and residual attenuation. Local detection of abnormalities makes 3D QMUS a promising method that can be used in research and potentially for clinical evaluation.

An Open-Source Framework for Automated High-Throughput Cell Biology Experiments

Modern data analysis methods, such as optimization algorithms or deep learning have been successfully applied to a number of biotechnological and medical questions. For these methods to be efficient, a large number of high-quality and reproducible experiments needs to be conducted, requiring a high degree of automation. Here, we present an open-source hardware and low-cost framework that allows for automatic high-throughput generation of large amounts of cell biology data. Our design consists of an epifluorescent microscope with automated XY stage for moving a multiwell plate containing cells and a perfusion manifold allowing programmed application of up to eight different solutions. Our system is very flexible and can be adapted easily for individual experimental needs. To demonstrate the utility of the system, we have used it to perform high-throughput Ca2+ imaging and large-scale fluorescent labeling experiments.

Three-dimensional quantitative muscle ultrasound in a healthy population

INTRODUCTION/AIMS

Quantitative muscle ultrasound offers biomarkers that aid in the diagnosis, detection, and follow-up of neuromuscular disorders. At present, quantitative muscle ultrasound methods are 2D and are often operator and device dependent. The aim of this study was to combine an existing device independent method with an automated ultrasound machine and perform 3D quantitative muscle ultrasound, providing new normative data of healthy controls.

METHODS

In total, 123 healthy volunteers were included. After physical examination, 3D ultrasound scans of the tibialis anterior muscle were acquired using an automated ultrasound scanner. Image postprocessing was performed to obtain calibrated echo intensity values based on a phantom reference.

RESULTS

Tibialis anterior muscle volumes of 61.2 ± 24.1 mL and 53.7 ± 22.7 mL were scanned in males and females, respectively. Echo intensity correlated with gender**, age**, fat fraction*, histogram kurtosis**, skewness* and standard deviation** (*P < .05, **P < .01). Outcome measures did not differ significantly for different acquisition presets. The 3D quantitative muscle ultrasound revealed the non-uniformity of echo intensity values over the length of the tibialis anterior muscle.

DISCUSSION

Our method extended 2D measurements and confirmed previous findings. Our method and reported normative data of (potential) biomarkers can be used to study neuromuscular disorders.

Electrocatalytic evidence of the diversity of the oxygen reaction in the bacterial bd oxidase from different organisms

Cytochrome bd oxidase is a bacterial terminal oxygen reductase that was suggested to enable adaptation to different environments and to confer resistance to stress conditions. An electrocatalytic study of the cyt bd oxidases from Escherichia coli, Corynebacterium glutamicum and Geobacillus thermodenitrificans gives evidence for a different reactivity towards oxygen. An inversion of the redox potential values of the three hemes is found when comparing the enzymes from different bacteria. This inversion can be correlated with different protonated glutamic acids as evidenced by reaction induced FTIR spectroscopy. The influence of the microenvironment of the hemes on the reactivity towards oxygen is discussed.

[ACTUAL STRATEGY OF TREATMENT VARICOSE VEINS RECURRENCE AFTER ENDOVENOUS INTERVENTIONS]

The aim of the study is to substantiate the surgical treatment tactics of recurrence varicose veins after endovenous interventions. Early and long-term results of the treatment, quality of life of patients with recurrence of varicose veins were studied. Among the admitted patients, there were 55 (65.5%) women and 29 (34.5%) men, the age of patients varied from 19 to 76 years. Of these, 9 patients underwent crossectomy, endovenous laser coagulation - 22, various stripping options - 4, echosclerotherapy - 20, intraoperative catheter sclerobliteration - 1, ligation of perforating veins - 28 patients. The choice of the treatment method depends on the data of duplex angioscanning, the source of recurrence, the diameter and length of the varicose veins. In the early postoperative period 18 (22.6%) patients had complications and side effects. Most often hyperpigmentation and neurological disorders developed, which were observed in 8 (9.5%) and 7 (8.3%) cases. 2 (2.4%) patients had a slightly painful dense cord after endovenous laser coagulation. 1 (1.2%) patient had a lymphocele in the inguinal incision area. This complication was eliminated by use of the puncture treatment method. Long-term results in terms of 1 to 3 years were studied in 82 (97.6%) patients. In the long-term period, 1 (1.2%) patient noted the varicose veins recurrence due to neovasculogenesis in the groin. The patient underwent micro-foam echosclerotherapy. Patient`s quality of life was studied by using the CIVIQ2 questionnaire before and 1 year after treatment. It was found that 4 main indicators of the quality of life in the long-term period improved by 35.6-48.8% of the preoperative values. At the same time, the most significant positive dynamics of psychological (48.8%) and pain (47.1%) factors was observed. The results justify the need for a differentiated approach, taking into account the individual characteristics of the disease, as well as the expediency of using minimally invasive techniques in patients with varicose veins recurrence.

Stabilization of the Highly Hydrophobic Membrane Protein, Cytochrome bd Oxidase, on Metallic Surfaces for Direct Electrochemical Studies

The cytochrome bd oxidase catalyzes the reduction of oxygen to water in bacteria and it is thus an interesting target for electrocatalytic studies and biosensor applications. The bd oxidase is completely embedded in the phospholipid membrane. In this study, the variation of the surface charge of thiol-modified gold nanoparticles, the length of the thiols and the other crucial parameters including optimal phospholipid content and type, have been performed, giving insight into the role of these factors for the optimal interaction and direct electron transfer of an integral membrane protein. Importantly, all three tested factors, the lipid type, the electrode surface charge and the thiol length mutually influenced the stability of films of the cytochrome bd oxidase. The best electrocatalytic responses were obtained on the neutral gold surface when the negatively charged phosphatidylglycerol (PG) was used and on the charged gold surface when the zwitterionic phosphatidylethanolamine (PE) was used. The advantages of the covalent binding of the membrane protein to the electrode surface over the non-covalent binding are also discussed.

Coordinated Ras and Rac Activity Shapes Macropinocytic Cups and Enables Phagocytosis of Geometrically Diverse Bacteria

Engulfment of extracellular material by phagocytosis or macropinocytosis depends on the ability of cells to generate specialized cup-shaped protrusions. To effectively capture and internalize their targets, these cups are organized into a ring or ruffle of actin-driven protrusion encircling a non-protrusive interior domain. These functional domains depend on the combined activities of multiple Ras and Rho family small GTPases, but how their activities are integrated and differentially regulated over space and time is unknown. Here, we show that the amoeba Dictyostelium discoideum coordinates Ras and Rac activity using the multidomain protein RGBARG (RCC1, RhoGEF, BAR, and RasGAP-containing protein). We find RGBARG uses a tripartite mechanism of Ras, Rac, and phospholipid interactions to localize at the protruding edge and interface with the interior of both macropinocytic and phagocytic cups. There, we propose RGBARG shapes the protrusion by expanding Rac activation at the rim while suppressing expansion of the active Ras interior domain. Consequently, cells lacking RGBARG form enlarged, flat interior domains unable to generate large macropinosomes. During phagocytosis, we find that disruption of RGBARG causes a geometry-specific defect in engulfing rod-shaped bacteria and ellipsoidal beads. This demonstrates the importance of coordinating small GTPase activities during engulfment of more complex shapes and thus the full physiological range of microbes, and how this is achieved in a model professional phagocyte.

•

We identify a new regulator that shapes macropinocytic and phagocytic cups

•

Shaping protrusions into cups requires differential regulation of Ras and Rac

•

Cups are organized by integrating interactions with phospholipids and multiple GTPases

•

Defective cup formation causes a target shape-specific defect in phagocytosis

Impact of two of the world's largest protected areas on longline fishery catch rates

Two of the largest protected areas on earth are U.S. National Monuments in the Pacific Ocean. Numerous claims have been made about the impacts of these protected areas on the fishing industry, but there has been no ex post empirical evaluation of their effects. We use administrative data documenting individual fishing events to evaluate the economic impact of the expansion of these two monuments on the Hawaii longline fishing fleet. Surprisingly, catch and catch-per-unit-effort are higher since the expansions began. To disentangle the causal effect of the expansions from confounding factors, we use unaffected control fisheries to perform a difference-in-differences analysis. We find that the monument expansions had little, if any, negative impacts on the fishing industry, corroborating ecological models that have predicted minimal impacts from closing large parts of the Pacific Ocean to fishing.

Active site rearrangement and structural divergence in prokaryotic respiratory oxidases

Cytochrome bd–type quinol oxidases catalyze the reduction of molecular oxygen to water in the respiratory chain of many human-pathogenic bacteria. They are structurally unrelated to mitochondrial cytochrome c oxidases and are therefore a prime target for the development of antimicrobial drugs. We determined the structure of theEscherichia colicytochrome bd-I oxidase by single-particle cryo–electron microscopy to a resolution of 2.7 angstroms. Our structure contains a previously unknown accessory subunit CydH, the L-subfamily–specific Q-loop domain, a structural ubiquinone-8 cofactor, an active-site density interpreted as dioxygen, distinct water-filled proton channels, and an oxygen-conducting pathway. Comparison with another cytochrome bd oxidase reveals structural divergence in the family, including rearrangement of high-spin hemes and conformational adaption of a transmembrane helix to generate a distinct oxygen-binding site.

Physicochemical characterization of human cardiovascular deposits

Detailed crystal chemical characterization of human pathological cardiovascular deposits (PCD) was conducted applying wide set of the instrumental methods (XRD, FTIR, Raman, SEM, different chemical analyses). There was some progress achieved in the understanding of it formation mechanism. The obtained data evidence that pathological cardiovascular deposits are presented by non-stoichiometric water-bearing B-type carbonated hydroxyapatite just like other apatites of the human body. But PCD apatite is characterized by higher concentration of B-type carbonate ion (up to ~ 6 wt%) which leads to the increasing influence of the carbonate-ion on the unit cell parameters in comparison with water and other substitutes. Another difference between PCD apatite and other pathogenic apatites of the human body is the smaller variations of the unit cell parameters, caused by smaller variations of the blood chemical composition. It was shown that apatite on the surface of PCD is characterized by the more non-stoichiometric composition compared to apatite inside these deposits. It is assumed that the formation mechanisms of the PCD apatite and the bone apatite may be similar.

Ca2+-Activated K+ Channels Reduce Network Excitability, Improving Adaptability and Energetics for Transmitting and Perceiving Sensory Information

Ca2+-activated K+ channels (BK and SK) are ubiquitous in synaptic circuits, but their role in network adaptation and sensory perception remains largely unknown. Using electrophysiological and behavioral assays and biophysical modeling, we discover how visual information transfer in mutants lacking the BK channel (dSlo- ), SK channel (dSK- ), or both (dSK- ;; dSlo- ) is shaped in the female fruit fly (Drosophila melanogaster) R1-R6 photoreceptor-LMC circuits (R-LMC-R system) through synaptic feedforward-feedback interactions and reduced R1-R6 Shaker and Shab K+ conductances. This homeostatic compensation is specific for each mutant, leading to distinctive adaptive dynamics. We show how these dynamics inescapably increase the energy cost of information and promote the mutants' distorted motion perception, determining the true price and limits of chronic homeostatic compensation in an in vivo genetic animal model. These results reveal why Ca2+-activated K+ channels reduce network excitability (energetics), improving neural adaptability for transmitting and perceiving sensory information.SIGNIFICANCE STATEMENT In this study, we directly link in vivo and ex vivo experiments with detailed stochastically operating biophysical models to extract new mechanistic knowledge of how Drosophila photoreceptor-interneuron-photoreceptor (R-LMC-R) circuitry homeostatically retains its information sampling and transmission capacity against chronic perturbations in its ion-channel composition, and what is the cost of this compensation and its impact on optomotor behavior. We anticipate that this novel approach will provide a useful template to other model organisms and computational neuroscience, in general, in dissecting fundamental mechanisms of homeostatic compensation and deepening our understanding of how biological neural networks work.

Intestinal insulin/IGF1 signalling through FoxO1 regulates epithelial integrity and susceptibility to colon cancer

Obesity promotes the development of insulin resistance and increases the incidence of colitis-associated cancer (CAC), but whether a blunted insulin action specifically in intestinal epithelial cells (IECs) affects CAC is unknown. Here, we show that obesity impairs insulin sensitivity in IECs and that mice with IEC-specific inactivation of the insulin and IGF1 receptors exhibit enhanced CAC development as a consequence of impaired restoration of gut barrier function. Blunted insulin signalling retains the transcription factor FOXO1 in the nucleus to inhibit expression of Dsc3, thereby impairing desmosome formation and epithelial integrity. Both IEC-specific nuclear FoxO1ADA expression and IEC-specific Dsc3 inactivation recapitulate the impaired intestinal integrity and increased CAC burden. Spontaneous colonic tumour formation and compromised intestinal integrity are also observed upon IEC-specific coexpression of FoxO1ADA and a stable Myc variant, thus suggesting a molecular mechanism through which impaired insulin action and nuclear FOXO1 in IECs promotes CAC.

Long-term imaging of calcium dynamics using genetically encoded calcium indicators and automatic tracking of cultured cells

Calcium dynamics is crucial for many signaling pathways and cell functions. Understanding how calcium regulates cell function often requires long-term imaging of calcium dynamics. Here we report a methodological approach of long-term (5-10 h) imaging of calcium dynamics in cultured cells. The approach links calcium imaging using genetically encoded calcium indicators and semi-automatic tracking of individual cells. It can be used in a large variety of situations, ranging from the role of calcium in biological processes to cell heterogeneity and screening of drugs modifying signaling pathways.

Lattice Study of QCD Phase Structure by Canonical Approach

The canonical approach is a powerful tool to circumvent sign problem in LQCD. Although it has its own difficulties it provides opportunity to determine QCD phase transition line. Using improved Wilson fermions we calculated number density at nonzero imaginary chemical potential for confinement and deconfinement phases, restored canonical partition functions Zn and did extrapolation into the real chemical potential region. We computed the higher moments of the baryon number including the kurtosis, and compared our results with information from relativistic heavy ion collision experiments.

Restoring canonical partition functions from imaginary chemical potential

Using GPGPU techniques and multi-precision calculation we developed the code to study QCD phase transition line in the canonical approach. The canonical approach is a powerful tool to investigate sign problem in Lattice QCD. The central part of the canonical approach is the fugacity expansion of the grand canonical partition functions. Canonical partition functions Zn(T) are coefficients of this expansion. Using various methods we study properties of Zn(T). At the last step we perform cubic spline for temperature dependence of Zn(T) at fixed n and compute baryon number susceptibility χB/T2 as function of temperature. After that we compute numerically ∂χ/∂T and restore crossover line in QCD phase diagram. We use improved Wilson fermions and Iwasaki gauge action on the 163 × 4 lattice with mπ/mρ = 0.8 as a sandbox to check the canonical approach. In this framework we obtain coefficient in parametrization of crossover line Tc(µ2B) = Tc(C−ĸµ2B/T2c) with ĸ = −0.0453 ± 0.0099.

Measurements of double-polarized compton scattering asymmetries and extraction of the proton spin polarizabilities

The spin polarizabilities of the nucleon describe how the spin of the nucleon responds to an incident polarized photon. The most model-independent way to extract the nucleon spin polarizabilities is through polarized Compton scattering. Double-polarized Compton scattering asymmetries on the proton were measured in the Δ(1232) region using circularly polarized incident photons and a transversely polarized proton target at the Mainz Microtron. Fits to asymmetry data were performed using a dispersion model calculation and a baryon chiral perturbation theory calculation, and a separation of all four proton spin polarizabilities in the multipole basis was achieved. The analysis based on a dispersion model calculation yields γ(E1E1)=-3.5±1.2, γ(M1M1)=3.16±0.85, γ(E1M2)=-0.7±1.2, and γ(M1E2)=1.99±0.29, in units of 10(-4)  fm(4).

[Candidatus "Jettenia moscovienalis" sp. nov., a New Species of Bacteria Carrying out Anaerobic Ammonium Oxidation]

A new species of bacteria oxidizing ammonium with nitrite under anoxic conditions was isolated from the activated sludge of a semi-industrial bioreactor treating digested sludge of the Kuryanovo wastewater treatment plant (Moscow, Russia). Physiological, morphological, and molecular genetic characterization of the isolate was carried out. The cells were ovoid (-0.5 x 0.8 μm), with the intracellular membrane structures characteristic of anammox bacteria (anammoxosome and paryphoplasm); unlike other anammox bacteria, it possessed extensive intracellular membrane structures located in layers parallel to the cytoplasmic membrane, but never close to the anammoxosome. The cells formed aggregates 5-28 μm in diameter and readily attached to solid surfaces. The cells were morphologically labile, easily plasmolyzed, and lost their content. Doubling time was 28 days, μ(max) = 0.025 day(-1); optimal temperature and pH for growth were 20-45 degrees C and 8.0, respectively. Phylogenetic analysis of the 16S rRNA gene sequences suggested its classification as a new species of the candidate genus Jettenia (order Planctomycetales). The name Candidatus "Jettenia moscovienalis" sp. nov. was proposed for the new bacterium.

Measurement of the transverse target and beam-target asymmetries in η meson photoproduction at MAMI

We present new data for the transverse target asymmetry T and the very first data for the beam-target asymmetry F in the γ[over →]p[over →]→ηp reaction up to a center-of-mass energy of W=1.9  GeV. The data were obtained with the Crystal-Ball/TAPS detector setup at the Glasgow tagged photon facility of the Mainz Microtron MAMI. All existing model predictions fail to reproduce the new data indicating a significant impact on our understanding of the underlying dynamics of η meson photoproduction. The peculiar nodal structure observed in existing T data close to threshold is not confirmed.

Neutron skin of (208)pb from coherent pion photoproduction

Information on the size and shape of the neutron skin on (208)Pb is extracted from coherent pion photoproduction cross sections measured using the Crystal Ball detector together with the Glasgow tagger at the MAMI electron beam facility. On exploitation of an interpolated fit of a theoretical model to the measured cross sections, the half-height radius and diffuseness of the neutron distribution are found to be c(n)=6.70±0.03(stat.)  fm and a(n)=0.55±0.01(stat.)(-0.03)(+0.02)(sys.)  fm, respectively, corresponding to a neutron skin thickness Δr(np)=0.15±0.03(stat.)(-0.03)(+0.01)(sys.)  fm. The results give the first successful extraction of a neutron skin thickness with an electromagnetic probe and indicate that the skin of (208)Pb has a halo character. The measurement provides valuable new constraints on both the structure of nuclei and the equation of state for neutron-rich matter.

Photoproduction of π0 mesons off neutrons in the nucleon resonance region

Precise angular distributions have been measured for the first time for the photoproduction of π0 mesons off neutrons bound in the deuteron. The effects from nuclear Fermi motion have been eliminated by a complete kinematic reconstruction of the final state. The influence of final-state-interaction effects has been estimated by a comparison of the reaction cross section for quasifree protons bound in the deuteron to the results for free protons and then applied as a correction to the quasifree neutron data. The experiment was performed at the tagged photon facility of the Mainz Microtron MAMI with the Crystal Ball and TAPS detector setup for incident photon energies between 0.45 and 1.4 GeV. The results are compared to the predictions from reaction models and partial-wave analyses based on data from other isospin channels. The model predictions show large discrepancies among each other and the present data will provide much tighter constraints. This is demonstrated by the results of a new analysis in the framework of the Bonn-Gatchina coupled-channel analysis which included the present data.

Measurement of the 1H(γ, p)π0 reaction using a novel nucleon spin polarimeter

We report the first large-acceptance measurement of polarization transfer from a polarized photon beam to a recoiling nucleon. The measurement pioneers a novel polarimetry technique, which can be applied to many other nuclear and hadron physics experiments. The commissioning reaction of 1H(γ, p)π0 in the range 0.4<Eγ<1.4  GeV validates the technique and provides essential new data to constrain the excitation spectrum of the nucleon.

Narrow structure in the excitation function of η photoproduction off the neutron

The photoproduction of η mesons off nucleons bound in 2H and 3He has been measured in coincidence with recoil protons and recoil neutrons for incident photon energies from threshold up to 1.4 GeV. The experiments were performed at the Mainz MAMI accelerator, using the Glasgow tagged photon facility. Decay photons from the η→2γ and η→3π0 decays and the recoil nucleons were detected with an almost 4π electromagnetic calorimeter combining the Crystal Ball and TAPS detectors. The data from both targets are of excellent statistical quality and show a narrow structure in the excitation function of γn→nη. The results from the two measurements are consistent, taking into account the expected effects from nuclear Fermi motion. The best estimates for position and intrinsic width of the structure are W=(1670±5)  MeV and Γ=(30±15)  MeV. For the first time precise results for the angular dependence of this structure have been extracted.

Synaptic mechanisms of adaptation and sensitization in the retina

Sensory systems continually adjust the way stimuli are processed. What are the circuit mechanisms underlying this plasticity? We investigated how synapses in the retina of zebrafish adjust to changes in the temporal contrast of a visual stimulus by imaging activity in vivo. Following an increase in contrast, bipolar cell synapses with strong initial responses depressed, whereas synapses with weak initial responses facilitated. Depression and facilitation predominated in different strata of the inner retina, where bipolar cell output was anticorrelated with the activity of amacrine cell synapses providing inhibitory feedback. Pharmacological block of GABAergic feedback converted facilitating bipolar cell synapses into depressing ones. These results indicate that depression intrinsic to bipolar cell synapses causes adaptation of the ganglion cell response to contrast, whereas depression in amacrine cell synapses causes sensitization. Distinct microcircuits segregating to different layers of the retina can cause simultaneous increases or decreases in the gain of neural responses.

Spikes in retinal bipolar cells phase-lock to visual stimuli with millisecond precision

Background

The conversion of an analog stimulus into the digital form of spikes is a fundamental step in encoding sensory information. Here, we investigate this transformation in the visual system of fish by in vivo calcium imaging and electrophysiology of retinal bipolar cells, which have been assumed to be purely graded neurons.

Results

Synapses of all major classes of retinal bipolar cell encode visual information by using a combination of spikes and graded signals. Spikes are triggered within the synaptic terminal and, although sparse, phase-lock to a stimulus with a jitter as low as 2–3 ms. Spikes in bipolar cells encode a visual stimulus less reliably than spikes in ganglion cells but with similar temporal precision. The spike-generating mechanism does not alter the temporal filtering of a stimulus compared with the generator potential. The amplitude of the graded component of the presynaptic calcium signal can vary in time, and small fluctuations in resting membrane potential alter spike frequency and even switch spiking on and off.

Conclusions

In the retina of fish, the millisecond precision of spike coding begins in the synaptic terminal of bipolar cells. This neural compartment regulates the frequency of digital signals transmitted to the inner retina as well as the strength of graded signals.

Properties of Free-Standing GaN Bulk Crystals Grown by HVPE

GaN wafers 200 μm thick and 30 mm diameter were fabricated. GaN was grown by hydride vapor phase epitaxy on SiC substrates and removed from the substrate by reactive ion etching. Lateral size of the GaN wafers was equal to the size of the initial SiC substrates. GaN wafers were cleaved in pieces and these pieces were characterised. It was found that after the fabrication, GaN crystals were slightly deformed and strained. An anneal at 830°C in nitrogen ambient eliminated the residual strains. The FWHM of ω-scan (0002) x-ray rocking curve for annealed crystals was less than 140 arcsec for both sides of the best GaN crystals. The lattice constants measured from both sides of the crystals were c =5.1853±0.0003 Å and a = 3.1889±0.0001 Å. The Nd – Na concentration determined by a mercury probe was about 2×1017cm−3 for as-grown GaN surface and about 2×1019cm−3 for former interface surface. Photoluminescence spectrum taken at 17 K revealed an edge peak at 3.472 eV with the FWHM value of 2.3 meV. A ratio of the edge peak intensity to the intensity of yellow band was higher than 1000. Initial TEM experiments were performed.

Beam-helicity asymmetries in double-pion photoproduction off the proton

Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz in the three isospin channels gamma[over -->]p-->pi(+)pi(0)n, gamma[over -->]p-->pi(0)pi(0)p, and gamma[over -->]p-->pi(+)pi(-)p. The circularly polarized photons, produced from bremsstrahlung of longitudinally polarized electrons, were tagged with the Glasgow magnetic spectrometer. Charged pions and the decay photons of pi(0) mesons were detected in a 4pi electromagnetic calorimeter which combined the Crystal Ball detector with the TAPS detector. The precisely measured asymmetries are very sensitive to details of the production processes and are thus key observables in the modeling of the reaction dynamics.

Network adaptation improves temporal representation of naturalistic stimuli in Drosophila eye: II mechanisms

Retinal networks must adapt constantly to best present the ever changing visual world to the brain. Here we test the hypothesis that adaptation is a result of different mechanisms at several synaptic connections within the network. In a companion paper (Part I), we showed that adaptation in the photoreceptors (R1-R6) and large monopolar cells (LMC) of the Drosophila eye improves sensitivity to under-represented signals in seconds by enhancing both the amplitude and frequency distribution of LMCs' voltage responses to repeated naturalistic contrast series. In this paper, we show that such adaptation needs both the light-mediated conductance and feedback-mediated synaptic conductance. A faulty feedforward pathway in histamine receptor mutant flies speeds up the LMC output, mimicking extreme light adaptation. A faulty feedback pathway from L2 LMCs to photoreceptors slows down the LMC output, mimicking dark adaptation. These results underline the importance of network adaptation for efficient coding, and as a mechanism for selectively regulating the size and speed of signals in neurons. We suggest that concert action of many different mechanisms and neural connections are responsible for adaptation to visual stimuli. Further, our results demonstrate the need for detailed circuit reconstructions like that of the Drosophila lamina, to understand how networks process information.

Network adaptation improves temporal representation of naturalistic stimuli in Drosophila eye: I dynamics

Because of the limited processing capacity of eyes, retinal networks must adapt constantly to best present the ever changing visual world to the brain. However, we still know little about how adaptation in retinal networks shapes neural encoding of changing information. To study this question, we recorded voltage responses from photoreceptors (R1–R6) and their output neurons (LMCs) in the Drosophila eye to repeated patterns of contrast values, collected from natural scenes. By analyzing the continuous photoreceptor-to-LMC transformations of these graded-potential neurons, we show that the efficiency of coding is dynamically improved by adaptation. In particular, adaptation enhances both the frequency and amplitude distribution of LMC output by improving sensitivity to under-represented signals within seconds. Moreover, the signal-to-noise ratio of LMC output increases in the same time scale. We suggest that these coding properties can be used to study network adaptation using the genetic tools in Drosophila, as shown in a companion paper (Part II).

Incoherent neutral pion photoproduction on 12C

We present the first detailed measurement of incoherent photoproduction of neutral pions to a discrete state of a residual nucleus. The 12C(gamma,pi(0))(12)C*(4.4 MeV) reaction has been studied with the Glasgow photon tagger at MAMI employing a new technique which uses the large solid angle Crystal Ball detector both as a pi(0) spectrometer and to detect decay photons from the excited residual nucleus. The technique has potential applications to a broad range of future nuclear measurements with the Crystal Ball and similar detector systems elsewhere. Such data are sensitive to the propagation of the Delta in the nuclear medium and will give the first information on matter transition form factors from measurements with an electromagnetic probe. The incoherent cross sections are compared to two theoretical predictions including a Delta-hole model.

Transforming growth factor beta induced FoxP3+ regulatory T cells suppress Th1 mediated experimental colitis

BACKGROUND AND AIMS

The imbalance between effector and regulatory T cells plays a central role in the pathogenesis of inflammatory bowel diseases. In addition to the thymus, CD4+CD25+ regulatory T cells can be induced in the periphery from a population of CD25- T cells by treatment with transforming growth factor beta (TGF-beta). Here, we analysed the in vivo function of TGF-beta induced regulatory T (Ti-Treg) cells in experimental colitis.

METHODS

Ti-Treg cells were generated in cell culture in the presence or absence of TGF-beta and tested for their regulatory potential in experimental colitis using the CD4+CD62L+ T cell transfer model.

RESULTS

Ti-Treg cells significantly suppressed Th1 mediated colitis on CD4+CD62L+ T cell transfer in vivo, as shown by high resolution endoscopy, histology, immunohistochemistry, and cytokine analysis. Further analysis of in vivo and in vitro expanded Ti-Treg cells showed that exogenous interleukin 2 (IL-2) was crucial for survival and expansion of these cells.

CONCLUSION

Our data suggest that regulatory Ti-Treg cells expand by TGF-beta and exogenous IL-2 derived from effector T cells at the site of inflammation. In addition to Tr1 and thymic CD4+CD25+ T cells, peripheral Ti-Treg cells emerge as a class of regulatory T cells with therapeutic potential in T cell mediated chronic intestinal inflammation.

In vivo imaging of colitis and colon cancer development in mice using high resolution chromoendoscopy

BACKGROUND

Mouse models of colitis and cancer are indispensable for our understanding of the pathogenesis of these diseases. In the past, mice had to be sacrificed in order to analyse colitis activity and tumour development. We have developed a safe method for high resolution endoscopic monitoring of living mice.

METHODS

Mice developing colitis or colonic tumours were anaesthetised using avertine and repeatedly examined by endoscopy. A novel miniendoscope (1.9 mm outer diameter), denoted Coloview, was introduced via the anus and the colon was carefully insufflated with an air pump before analysis of the colonic mucosa. An extra working channel allowed the introduction of biopsy forceps or injection needles as well as surface staining with methylene blue in order to visualise the surface of the crypts and the pit pattern architecture.

RESULTS

Endoscopic pictures obtained were of high quality and allowed monitoring and grading of disease. Scoring of colitis activity as well as tumour size and growth was possible. In addition, pit pattern analysis using chromoendoscopy permitted discrimination between inflammatory and neoplastic changes. Biopsies yielded enough tissue for molecular and histopathological analyses.

CONCLUSIONS

In summary, chromoendoscopy in mice allows monitoring of the development of colitis and colon cancer with high resolution. Manipulations such as local injection of reagents or taking biopsies can be performed easily.

Functional properties of endogenous receptor- and store-operated calcium influx channels in HEK293 cells

Activation of phospholipase C (PLC)-mediated signaling pathways in non-excitable cells causes the release of calcium (Ca2+) from inositol 1,4,5-trisphosphate (InsP3)-sensitive intracellular Ca2+ stores and activation of Ca2+ influx via plasma membrane Ca2+ channels. The properties and molecular identity of plasma membrane Ca2+ influx channels in non-excitable cells is a focus of intense investigation. In the previous studies we used patch clamp electrophysiology to describe the properties of Ca2+ influx channels in human carcinoma A431 cell lines. Now we extend our studies to human embryonic kidney HEK293 cells. By using a combination of Ca2+ imaging and whole cell and single channel patch clamp recordings we discovered that: 1) HEK293 cells contain four types of plasma membrane Ca2+ influx channels: I(CRAC), Imin, Imax, and I(NS); 2) I(CRAC) channels are highly Ca2+-selective (P(Ca/Cs)>1000) and I(CRAC) single channel conductance is too small for single channel analysis; 3) Imin channels in HEK293 cells display functional properties identical to Imin channels in A431 cells, with single channel conductance of 1.2 pS for divalent cations, 10 pS for monovalent cations, and divalent cation selectivity P(Ba/K)=20; 4) Imin channels in HEK293 cells are activated by InsP3 and inhibited by phosphatidylinositol 4,5-bisphosphate, but store-independent; 5) when compared with Imin, Imax channels have higher conductance for divalent (17 pS) and monovalent (33 pS) cations, but less selective for divalent cations (P(Ba/K)=4), 6) Imax channels in HEK293 cells can be activated by InsP3 or by Ca2+ store depletion; 7) I(NS) channels are non-selective (P(Ba/K)=0.4) and display a single channel conductance of 5 pS; and 8) I(NS) channels are not gated by InsP3 but activated by depletion of intracellular Ca2+ stores. Our findings provide novel information about endogenous Ca2+ channels supporting receptor-operated and store-operated Ca2+ influx pathways in HEK293 cells.

IL-6 signaling promotes tumor growth in colorectal cancer

Recent investigations support an important role for TGF-beta in the development of colorectal cancer. However, the molecular consequences of TGF-beta signaling in the colon remains incompletely understood. In a recent study in Immunity, we analyzed the role of TGF-beta in a murine model of colon cancer. Using transgenic mice overexpressing TGF-beta or a dominant negative TGF-beta receptor II under control of the CD2 minigene, we show that TGF-beta signaling in tumor infiltrating T lymphocytes regulates the growth of dysplastic colon epithelial cells, as determined by histology and a novel system for high resolution chromoendoscopy in vivo. At the molecular level, TGF-beta signaling in T cells regulated STAT-3 activation in tumor cells via IL-6. IL-6 signaling required tumor cell derived soluble IL-6R rather than membrane bound IL-6R and suppression of such TGF-beta-dependent IL-6 trans-signaling prevented tumor progression in vivo. Similar to these observations in mice, here we show that human colon cancer tissue expressed only low amounts of membrane bound IL-6R. In contrast, expression and activity of the matrix metalloproteinase TACE were increased. In summary, our data provide novel insights into the role of TGF-beta signaling in colorectal cancer and suggest novel therapeutic approaches for colorectal cancer based on an inhibition of TGF-beta-dependent IL-6 trans-signaling.

IL-6 signaling promotes tumor growth in colorectal cancer

Recent investigations support an important role for TGF-beta in the development of colorectal cancer. However, the molecular consequences of TGF-beta signaling in the colon remains incompletely understood. In a recent study in Immunity, we analyzed the role of TGF-beta in a murine model of colon cancer. Using transgenic mice overexpressing TGF-beta or a dominant negative TGF-beta receptor II under control of the CD2 minigene, we show that TGF-beta signaling in tumor infiltrating T lymphocytes regulates the growth of dysplastic colon epithelial cells, as determined by histology and a novel system for high resolution chromoendoscopy in vivo. At the molecular level, TGF-beta signaling in T cells regulated STAT-3 activation in tumor cells via IL-6. IL-6 signaling required tumor cell derived soluble IL-6R rather than membrane bound IL-6R and suppression of such TGF-beta-dependent IL-6 trans-signaling prevented tumor progression in vivo. Similar to these observations in mice, here we show that human colon cancer tissue expressed only low amounts of membrane bound IL-6R. In contrast, expression and activity of the matrix metalloproteinase TACE were increased. In summary, our data provide novel insights into the role of TGF-beta signaling in colorectal cancer and suggest novel therapeutic approaches for colorectal cancer based on an inhibition of TGF-beta-dependent IL-6 trans-signaling.

Detection of abundantly transcribed genes and gene translocation in human immunodeficiency virus-associated non-Hodgkin's lymphoma

Several novel, differentially transcribed genes were identified in one centroblastic and one immunoblastic HIV-associated B-cell non-Hodgkin's lymphoma (B-NHL) by subtractive cloning. In both lymphomas, we detected an upregulated transcription of several mitochondrial genes. In the centroblastic B-NHL, we found a high level transcription of nuclear genes including the interferon-inducible gene (INF-ind), the immunoglobulin light chain gene (IgL), the set oncogene, and several unknown genes. The data obtained on upregulated expression of the genes in human B-NHL of HIV-infected patients considerably overlap with those obtained earlier for the B-NHL of simian immunodeficiency virus-infected monkeys. In the centroblastic lymphoma, one transcript revealed a fusion of the 3'-untranslated region of the set gene and the C-terminal region of the IgL gene. This chimeric sequence was confirmed by a site-directed polymerase chain reaction performed with total cDNA and genomic DNA. The expected amplification product was obtained in both cases pointing to a genomic rearrangement. The IgL-set fusion sequence was not found in cDNA preparations and genomic DNA of the immunoblastic HIV-associated B-NHL. Further studies are necessary to determine whether these genes contribute to lymphoma development or can be used as therapeutic targets.