Mechanisms and therapeutic targets for neuropathic itch

Neuropathic pruritus conditions arise from structural and/or functional damage of the peripheral or central nervous system. Novel findings of pruritus specific mediators and pathways strengthen the specificity theory of pruritus transmission, however electrophysiological studies suggest that focal activation of nociceptors and distinct discharge patterns of primary afferents also contribute to the development of the sensation of pruritus. A complex interplay between excitatory and inhibitory interneurons at spinal level, non-neuronal cells and descending modulation from upper centers contributes to neuronal sensitization and clinically to the chronicity of pruritus, as well as accompanying phenomena such as alloknesis and hyperknesis. Several topical, systemic and non-pharmacological therapeutic approaches directed at distinct targets are currently available.     

Contrast-enhancement cardiac magnetic resonance imaging beyond the scope of viability

The clinical applications of cardiovascular magnetic resonance imaging with contrast enhancement are expanding. Besides the direct visualisation of viable and non-viable myocardium, this technique is increasingly used in a variety of cardiac disorders to determine the exact aetiology, guide proper treatment, and predict outcome and prognosis. In this review, we discuss the value of cardiovascular magnetic resonance imaging with contrast enhancement in a range of cardiac disorders, in which this technique may provide insights beyond the scope of myocardial viability.     

NMR studies of electron carrier proteins from sulphate reducing bacteria.

The sulphate-reducing bacteria have a complex electron transfer system which leads to the reduction of sulphate by oxidation of either organic substrates or molecular hydrogen. These bacteria can either produce or consume molecular hydrogen. The central part of this electron pathway for Desulovibrio gigas is constituted by hydrogenase (3 X (4Fe-4S)). cytochrome c3 (4 haems with different redox potentials) and a one (4Fe-4S) cluster ferredoxin. This ferredoxin is isolated in different oligomeric forms, which stabilize different oxidation states and have different physiological roles; the trimer FdI being involved in the production of H2 and the tetramer FdII being more efficient for the consumption of H2. The presence of intrinsic probes (the iron ions) in these proteins is particularly helpful for structural studies using NMR spectroscopy. These studies allowed a characterization of the oxidation states used by the different oligomers of the ferredoxin and obtaintion of structural information on multi-haem cytochromes (c3 and c7). NMR is also suitable to study protein-protein interaction. The study of the complex formed between FdII and cytochrome c3 has shown that there is an alteration of the kinetics of electron transfer upon complexation.     

Morphology of the procarboxypeptidase A-S6 complex

Bovine pancreatic procarboxypeptidase A is secreted as a non-covalent association of three different proteins (pro CPA-S6). The free native subunits can be obtained by dissociation of the complex by dimethylmaleylation. Moreover, two specific binary complexes resulting from the high affinity of procarboxypeptidase A (subunit I) for its other two partners (subunits II and III) can also be obtained.In order to better understand the function of the association, an investigation of the morphology of the ternary complex by solution X-ray scattering has been carried out. The radii of gyration of all the molecular species have been obtained and the experimental results have been interpreted in terms of compact objects of simple shape. The various components correspond to globular particles as shown by the value of the ratio Rg/M^1/3. This is confirmed by the moderate anisotropy of the simple geometric shapes determined using an assumed value of 0.3 g H₂O/g protein for the hydration. The distances between the centres of gravity of pairs of species strongly suggest that the components are in the closest distance configuration or close to it. However, the binary complex I–III appears to be more open than the complex I–II. Finally, a model of the interaction between carboxpeptidase A and its activation peptide has been constructed by comparing the hypothetical geometric model of subunit I to the crystallographically determined structure of carboxypeptidase A.Abbreviations pro CPA procarboxypeptidase A - pro CPA-S6 (or T.C.) ternary complex with a sedimentation coefficient of 6S - CPA carboxypeptidase A     

Effects of benzyl alcohol on phosphatidylcholine lamellar phase with different water contents

Effects of benzyl alcohol (BA) on the bilayer thickness d₁ and the fluidity of egg phosphatidylcholine (PC) lamellar phase with various water contents have been studied by X-ray diffraction and the proton spin-lattice relaxation rate. At lower water contents; BA causes d₁ to decrease and the rate of molecular motions to increase. By contrast, with increasing BA at excess water, d₁ remains nearly unchanged, though the rate of motions increases. Hydration experiment for egg phosphatidylcholine lamellae with BA at a 1:1 molar ratio shows that in the range from 15% to 30% water, d₁ decreases to the value of the fully hydrated sample without BA and is nearly constant above 30% water. The value at full hydration is suggested to be a lower limit of the bilayer thickness, the chain is in the unperturbed state. It is in an extended structure at lower water contents. This leads to the difference in the effect of BA on the bilayer thickness at different water contents.     

Chelation of hypocrellin B with zinc ions with electron paramagnetic resonance (EPR) evidence of the photodynamic activity of the resulting chelate

Hypocrellin B (HB), a perylenequinone derivative, is an efficient phototherapeutic agent. The chelation of HB with Zinc ions (Zn²⁺) results in a metal chelate (Zn-HB) which exhibits considerable absorption (λ_max = 612nm) in the phototherapeutic window. The structure of this chelate has been characterized by UV-Vis, IR and mass spectra. The redox potentials of the Zn-HB chelate were E_ox = +1.1V (vs. SCE) and E_re = -0.7V (vs. SCE) as measured using the circle volt curve. The quantum yield of singlet oxygen generated by the Zn-HB chelate was 0.86, which both the electron spin trap (EPR) method and the chemical trap method show to be about 0.1 higher than that of its parent compound HB. In irradiated oxygen-saturated solutions of Zn-HB chelate, superoxide radical anions and hydroxyl radicals were detected by EPR spectroscopy using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as the spin-trapping agent.     

A highly conserved glutamic acid in ALFY inhibits membrane binding to aid in aggregate clearance

Autophagy‐linked FYVE protein (ALFY) is a large, multidomain protein involved in the degradation of protein aggregates by selective autophagy. The C‐terminal FYVE domain of ALFY has been shown to bind phosphatidylinositol 3‐phosphate (PI(3)P); however, ALFY only partially colocalizes with other FYVE domains in cells. Thus, we asked if the FYVE domain of ALFY has distinct membrane binding properties compared to other FYVE domains and whether these properties might affect its function in vivo. We found that the FYVE domain of ALFY binds weakly to PI(3)P containing membranes in vitro. This weak binding is the result of a highly conserved glutamic acid within the membrane insertion loop in the FYVE domain of ALFY that is not present in any other human FYVE domain. In addition, not only does this glutamic acid reduce binding to membranes in vitro and inhibits its targeting to membranes in vivo, but it is also important for the ability of ALFY to clear protein aggregates.     

Efficient double-scattering proton therapy with a patient-specific bolus

PurposePassive scattering proton radiotherapy utilizes beam-specific compensators to shape the dose to the distal end of the tumor target. These compensators typically require therapists to enter the treatment room to mount between beams. This study investigates a novel approach that utilizes a single patient-specific bolus to accomplish the role of multi-field compensators to improve the efficiency of the treatment delivery.MethodsRay-tracing from the proton virtual source was used to convert the beam-specific compensators (mounted on the gantry nozzle) into an equivalent bolus thickness on the patient surface. The field bolus contours were combined to create a single bolus. A 3D acrylic bolus was milled for a head phantom. The dose distribution of the compensator plan was compared to the bolus plan using 3D Gamma analysis and film measurements. Boluses for two clinical patients were also designed.ResultsThe calculated phantom dose distribution of the original proton compensator plan was shown to be equivalent to the plan with the surface bolus. Film irradiations with the proton bolus also confirmed the dosimetric equivalence of the two techniques. The dose distribution equivalency of the bolus plans for the clinical patients were demonstrated.ConclusionsWe presented a novel approach that uses a single patient-specific bolus to replace patient compensators during passive scattering proton delivery. This approach has the potential to reduce the treatment time, the compensator manufacturing costs, the risk of potential collision between the compensator and the patient/couch, and the waste of compensator material.     

RNA Catalyst as a Reporter for Screening Drugs against RNA Editing in Trypanosomes

Substantial progress has been made in determining the mechanism of mitochondrial RNA editing in trypanosomes. Similarly, considerable progress has been made in identifying the components of the editosome complex that catalyze RNA editing. However, it is still not clear how those proteins work together. Chemical compounds obtained from a high-throughput screen against the editosome may block or affect one or more steps in the editing cycle. Therefore, the identification of new chemical compounds will generate valuable molecular probes for dissecting the editosome function and assembly. In previous studies, in vitro editing assays were carried out using radio-labeled RNA. These assays are time consuming, inefficient and unsuitable for high-throughput purposes. Here, a homogenous fluorescence-based “mix and measure” hammerhead ribozyme in vitro reporter assay to monitor RNA editing, is presented. Only as a consequence of RNA editing of the hammerhead ribozyme a fluorescence resonance energy transfer (FRET) oligoribonucleotide substrate undergoes cleavage. This in turn results in separation of the fluorophore from the quencher thereby producing a signal. In contrast, when the editosome function is inhibited, the fluorescence signal will be quenched. This is a highly sensitive and simple assay that should be generally applicable to monitor in vitro RNA editing or high throughput screening of chemicals that can inhibit the editosome function.     

Light gradients in shoots subjected to unilateral illumination—implications for phototropism

Abstract. When an organ is subject to unilateral illumination, light entering the organ is attenuated very efficiently and the irradiance at the 'shaded' surface is only a small percentage of that at the illuminated surface. The light gradient across the organ is approximately exponential, being steepest across the first few cell layers. The penetration of light into an organ was found to be similar with red or blue light and was largely independent of the pigmentation of the organ. Studies of light transmission in organs infiltrated with liquids of different refractive index showed that refraction and reflection were the main factors in establishing the light gradient in organs.
The implications of the measured light gradients are discussed briefly in relation to models of phototropism.