Screening an In-House Isoquinoline Alkaloids Library for New Blockers of Voltage-Gated Na+ Channels Using Voltage Sensor Fluorescent Probes: Hits and Biases

Voltage-gated Na⁺ (Na_V) channels are significant therapeutic targets for the treatment of cardiac and neurological disorders, thus promoting the search for novel Na_V channel ligands. With the objective of discovering new blockers of Na_V channel ligands, we screened an In-House vegetal alkaloid library using fluorescence cell-based assays. We screened 62 isoquinoline alkaloids (IA) for their ability to decrease the FRET signal of voltage sensor probes (VSP), which were induced by the activation of Na_V channels with batrachotoxin (BTX) in GH3b6 cells. This led to the selection of five IA: liriodenine, oxostephanine, thalmiculine, protopine, and bebeerine, inhibiting the BTX-induced VSP signal with micromolar IC₅₀. These five alkaloids were then assayed using the Na⁺ fluorescent probe ANG-2 and the patch-clamp technique. Only oxostephanine and liriodenine were able to inhibit the BTX-induced ANG-2 signal in HEK293-hNa_V1.3 cells. Indeed, liriodenine and oxostephanine decreased the effects of BTX on Na⁺ currents elicited by the hNa_V1.3 channel, suggesting that conformation change induced by BTX binding could induce a bias in fluorescent assays. However, among the five IA selected in the VSP assay, only bebeerine exhibited strong inhibitory effects against Na⁺ currents elicited by the hNav1.2 and hNav1.6 channels, with IC₅₀ values below 10 µM. So far, bebeerine is the first BBIQ to have been reported to block Na_V channels, with promising therapeutical applications.     

Albatrellus confluens (Alb. & Schwein.) Kotl. & Pouz.: Natural Fungal Compounds and Synthetic Derivatives with In Vitro Anthelmintic Activities and Antiproliferative Effects against Two Human Cancer Cell Lines

Neglected tropical diseases affect the world’s poorest populations with soil-transmitted helminthiasis and schistosomiasis being among the most prevalent ones. Mass drug administration is currently the most important control measure, but the use of the few available drugs is giving rise to increased resistance of the parasites to the drugs. Different approaches are needed to come up with new therapeutic agents against these helminths. Fungi are a source of secondary metabolites, but most fungi remain largely uninvestigated as anthelmintics. In this report, the anthelmintic activity of Albatrellus confluens against Caenorhabditis elegans was investigated using bio-assay guided isolation. Grifolin (1) and neogrifolin (2) were identified as responsible for the anthelmintic activity. Derivatives 4–6 were synthesized to investigate the effect of varying the prenyl chain length on anthelmintic activity. The isolated compounds 1 and 2 and synthetic derivatives 4–6, as well as their educts 7–10, were tested against Schistosoma mansoni (adult and newly transformed schistosomula), Strongyloides ratti, Heligmosomoides polygyrus, Necator americanus, and Ancylostoma ceylanicum. Prenyl-2-orcinol (4) and geranylgeranyl-2-orcinol (6) showed promising activity against newly transformed schistosomula. The compounds 1, 2, 4, 5, and 6 were also screened for antiproliferative or cytotoxic activity against two human cancer lines, viz. prostate adenocarcinoma cells (PC-3) and colorectal adenocarcinoma cells (HT-29). Compound 6 was determined to be the most effective against both cell lines with IC₅₀ values of 16.1 µM in PC-3 prostate cells and 33.7 µM in HT-29 colorectal cells.     

Evaluation of aortic stenosis severity using 4D flow jet shear layer detection for the measurement of valve effective orifice area

Aims

The objective of this study was to evaluate the potential of 4D flow MRI to assess valve effective orifice area (EOA) in patients with aortic stenosis as determined by the jet shear layer detection (JSLD) method.

Methods and Results

An in-vitro stenosis phantom was used for validation and in-vivo imaging was performed in 10 healthy controls and 40 patients with aortic stenosis. EOA was calculated by the JSLD method using standard 2D phase contrast MRI (PC-MRI) and 4D flow MRI measurements (EOA_JSLD-2D and EOA_JSLD-4D, respectively). As a reference standard, the continuity equation was used to calculate EOA (EOA_CE) with the 2D PC-MRI velocity field and compared to the EOA_JSLD measurements. The in-vitro results exhibited excellent agreement between flow theory (EOA = 0.78 cm²) and experimental measurement (EOA_JSLD-4D = 0.78 ± 0.01 cm²) for peak velocities ranging from 0.9 to 3.7 m/s. In-vivo results showed good correlation and agreement between EOA_JSLD-2D and EOA_CE (r = 0.91, p < 0.001; bias: − 0.01 ± 0.38 cm²; agreement limits: 0.75 to − 0.77 cm²), and between EOA_JSLD-4D and EOA_CE (r = 0.95, p < 0.001; bias: − 0.09 ± 0.26 cm²; limits: 0.43 to − 0.62 cm²).

Conclusion

This study demonstrates the feasibility of measuring EOA_JSLD using 4D flow MRI. The technique allows for optimization of the EOA measurement position by visualizing the 3D vena contracta, and avoids potential sources of EOA_CE measurement variability.     

Controlling the early stages of pentacene growth by supersonic molecular beam deposition

The key role of the pentacene kinetic energy (Ek) in the early stages of growth on SiOx/Si is demonstrated: islands with smooth borders and increased coalescence differ remarkably from fractal-like thermal growth. Increasing Ek to 6.4 eV, the morphology evolves towards higher density of smaller islands. At higher coverage, coalescence grows with Ek up to a much more uniform, less defected monolayer. The growth, interpreted by the diffusion mediated model, shows the critical nucleus changing from 3 to 2 pentacene for Ek>5-6 eV. Optimal conditions to produce single crystalline films are envisaged.     

Renormalization group treatment of phase transitions in ferromagnetic superconductors

We investigate the nature of the phase transition from the superconducting to the uniformly ordered magnetic phase in ferromagnetic superconductors by renormalization group methods. For this purpose Halperin, Lubensky, Ma's application of the-expansion to pure superconductors is extended to include the influence of magnetic order as well. Our treatment shows that in the vicinity of the ferromagnetic to superconducting phase-boundary critical fluctuations of the magnetization are absorbed into fluctuations of the magnetic field. As a consequence the transition always is first order. An additional indication to the dominance of electromagnetic effects is the irrelevance of the coupling corresponding to spin flip scattering.     

On the fundamental solutions of the operators of S. Timoshenko and R. D. Mindlin

Our recent paper about some new fundamental solutions is complemented by a representation of the fundamental solution of certain evolution operators of fourth order in terms of a family of fundamental solutions of operators of second order. By applying this to the operators of vibrating beams and plates we deduce representations of their fundamental solutions as simple definite integrals over tabulated functions.     

Symmetries and correlation inequalities for classicaln-vector models

We describe a new class of single spin measures on then-dimensional sphereS _r ⁿ of radiusr (n 4) for which Lebowitz-type [J. Lebowitz,J. Stat. Phys. 16:463 (1977)] inequalities hold. This is achieved by an appropriate parametrization ofS _r ⁿ . The above class includes the uniform measures onxs Rⁿ ¦x¦ r for any 0 p r. The second topic of this paper is an abstract formulation of the first Griffiths inequality [R. B. Griffiths,J. Math. Phys. 8:478 (1967)] and the underlying symmetry property.     

Minimax theorems for infinite graphs with the ends as ideal points

For a set of pairwise disjoint sets of ends of an infinite graph, we define the concepts of -paths and of -separators, and we determine the maximum number of pairwise disjoint -path.     

Influence of surroundings on photorefractive effect in lithium niobate crystals

In the paper results of the investigation of the influence of electric properties of the environment surrounding LiNbO₃ crystals on photorefractive effect induced in these crystals by Gaussian Ar⁺ laser beam with various intensities are presented. We show spatial and temporal dependences of changes of the refractive index obtained experimentally in LiNbO₃: Fe and LiNbO₃: Fe:Mn samples surrounded by media with different electric conductivities and different permittivities (water, air, water solution of CaCl₂). The space and time dependences of the refractive index changes induced by the Ar⁺ laser beam are observed by means of the Mach–Zehnder interferometer using light from HeNe laser. The experimentally obtained results are in a good agreement with those following from numerical calculations using the manifold mirroring method. The agreement between calculated and experimental results indicates that the polarization charge at the photorefractive crystal/surrounding medium boundary significantly influences the photorefractive process in the crystal. The experimentally observed slow spontaneous decrease of the refractive index change in a sample placed into a slightly conducting medium (air) after switching off the beam also indicates that the polarization charge in the sample's surroundings affects the photorefraction.