28 research outputs found
Theta-gamma phase-amplitude coupling: physiological basics, analysis methods, and perspectives of translation into clinical practice
Studying rhythmic neural synchronization (cross-frequency coupling in various ranges) is an emerging topic in present-day neurophysiology. One of the best-studied cross-frequency couplings is theta-gamma phase-amplitude coupling that contributes to the cognitive function and may vary in patients with several conditions associated with cognitive impairment. Changes in theta-gamma coupling can be registered in a wide range of diseases associated with cognitive decline.
The review covers the physiological basics of theta-gamma coupling, its registration and calculation, correlation with cognitive test results in healthy volunteers, and changes in patients. We have discussed the results of the preliminary studies of frequency-dependent non-invasive brain stimulation based on theta-gamma coupling
Influence of novel GPR119 agonist in combination with metformin and sitagliptin on glycemia, body weight and food intake in rats fed a high-fat diet
BACKGROUND: Metabolic syndrome and obesity are often precursors of type 2 diabetes mellitus (DM), and current recommendations indicate the advisability of early initiation of drug therapy at the stage of prediabetes. Drugs with incretin activity are one of the priority groups for monotherapy of type 2 diabetes in the onset of the disease, and certain drugs are used to treat obesity. GPR119 agonists increase the secretion of endogenous incretins, and their effectiveness in the treatment of type 2 diabetes and obesity in mono- and combination therapy is currently being actively studied. AIM. To evaluate of the effect of administration of a GPR119 receptor agonist, its combination with metformin or sitagliptin on body weight, food intake and glycemia in rats under a high-calorie diet. MATERIALS AND METHODS: The study was conducted on 56 outbred female rats aged 7–8 months and an initial weight of 305–320 g. Compound ZB-16 is a highly active GPR119 receptor agonist (EC50 = 7 nM). For 12 weeks, the animals were kept on a high-fat and carbohydrate diet and at the same time received the compound ZB-16, metformin and sitagliptin, or its combination (ZB-16 + metformin and ZB-16 + sitagliptin). During the experiment, the weight of the animals, the mass of feed eaten, as well as the level of glycemia after 6 hours of fasting and with an oral glucose load were assessed. RESULTS: In animals of the control group that were on a high-calorie and fatty diet for 12 weeks, an increase in body weight, glycemia and a decrease in the rate of glucose utilization were observed. The introduction of the GPR119 agonist (ZB-16) for 12 weeks led to a significant reduction in the amount of food consumed, limited weight gain and prevented the development of carbohydrate metabolism disorders. The addition of sitagliptin and especially metformin to therapy with the GPR119 agonist significantly increased the effectiveness of therapy compared to the control group, which was expressed in the normalization of animal body weight and glycemia (p <0.05). CONCLUSIONS: The introduction of a combination of the GPR119 agonist (compound ZB-16) with metformin and sitagliptin is more effective than monotherapy in terms of weight gain, food intake, and also prevents the development of carbohydrate metabolism disorders in animals when kept on a high-fat and carbohydrate diet
Interplay Between Mixed and Pure Exciton States Controls Singlet Fission in Rubrene Single Crystals
Singlet fission (SF) is a multielectron process in which one singlet exciton
S converts into a pair of triplet excitons T+T. SF is widely studied as it may
help overcome the Shockley-Queisser efficiency limit for semiconductor
photovoltaic cells. To elucidate and control the SF mechanism, great attention
has been given to the identification of intermediate states in SF materials,
which often appear elusive due to the complexity and fast timescales of the SF
process. Here, we apply 10fs-1ms transient absorption techniques to high-purity
rubrene single crystals to disentangle the intrinsic fission dynamics from the
effects of defects and grain boundaries and to identify reliably the fission
intermediates. We show that above-gap excitation directly generates a hybrid
vibronically assisted mixture of singlet state and triplet-pair multiexciton
[S:TT], which rapidly (<100fs) and coherently branches into pure singlet or
triplet excitations. The relaxation of [S:TT] to S is followed by a relatively
slow and temperature-activated (48 meV activation energy) incoherent fission
process. The SF competing pathways and intermediates revealed here unify the
observations and models presented in previous studies of SF in rubrene and
propose alternative strategies for the development of SF-enhanced photovoltaic
materials
Chemistry and Hypoglycemic Activity of GPR119 Agonist ZB-16
This article is to highlight the chemical properties and primary pharmacology of novel GPR119 agonist ZB-16 and its analogs, which were rejected during the screening. Experiments were performed in vitro (specific activity, metabolism and cell toxicity) and in vivo (hypoglycemic activity and pharmacokinetics). ZB-16 exhibits nanomolar activity (EC50 = 7.3–9.7 nM) on target receptor GPR119 in vitro associated with hypoglycemic activity in vivo. In animals with streptozotocin-nicotinamide induced type 2 diabetes mellitus (STZ-NA T2D) daily oral dose of ZB-16 (1 mg/kg) or sitagliptin (10 mg/kg) for 28 days resulted in the reduction of blood glucose levels. The effects of ZB-16 were comparable to the hypoglycemic action of sitagliptin. ZB-16 demonstrated relatively low plasma exposition, high distribution volume, mild clearance and a prolonged half-life (more than 12 h). The present study demonstrates that the targeted search for selective GPR119 receptor agonists is a well-founded approach for developing novel drugs for the therapy of T2D. Based on the combination of high in vitro activity (compared to competitor standards), a useful ADME profile, distinct hypoglycemic activity which is comparable to the efficacy of sitagliptin in rats with experimental T2D, and the acceptable pharmacokinetic profile, we recommend the ZB-16 compound for further research
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Ultrafast vibrational control of organohalide perovskite optoelectronic devices using vibrationally promoted electronic resonance
Vibrational control (VC) of photochemistry through the optical stimulation of structural dynamics is a nascent concept only recently demonstrated for model molecules in solution. Extending VC to state-of-the-art materials may lead to new applications and improved performance for optoelectronic devices. Metal halide perovskites are promising targets for VC due to their mechanical softness and the rich array of vibrational motions of both their inorganic and organic sublattices. Here, we demonstrate the ultrafast VC of FAPbBr3 perovskite solar cells via intramolecular vibrations of the formamidinium cation using spectroscopic techniques based on vibrationally promoted electronic resonance. The observed short (~300 fs) time window of VC highlights the fast dynamics of coupling between the cation and inorganic sublattice. First-principles modelling reveals that this coupling is mediated by hydrogen bonds that modulate both lead halide lattice and electronic states. Cation dynamics modulating this coupling may suppress non-radiative recombination in perovskites, leading to photovoltaics with reduced voltage losses
Effectiveness of empirical <i>Helicobacter pylori</i> eradication therapy with furazolidone in Russia: results from the European Registry on <i>Helicobacter pylori</i> Management (Hp-EuReg)
Background. First-line therapy does not always provide a high level of Helicobacter pylori eradication due to the increase of H. pylori resistance to antibiotics; therefore, it remains necessary to identify the most effective rescue treatments. The purpose of this study was to evaluate the efficacy and safety of empirical H. pylori furazolidone-containing regimens.
Materials and methods. Adult H. pylori infected patients empirically treated with furazolidone-containing eradication regimens were registered in an international, prospective, multicenter non-intervention European registry on H. pylori management (Hp-EuReg). Data were collected at AEG-REDCap e-CRF from 2013 to 2021 and the quality was reviewed. Modified intention-to-treat (mITT) effectiveness analyses were performed.
Results. Overall 106 patients received empirical furazolidone-containing therapy in Russia. Furazolidone was prescribed in a sequential scheme along with amoxicillin, clarithromycin and a proton pump inhibitor in 68 (64%) cases, triple regimens were prescribed in 28 (26%) patients and quadruple regimens in 10 (9.4%). Treatment duration of 7 days was assigned to 2 (1.9%) patients, 10-day eradication therapy in case of 80 (75%) and 14 days in 24 (23%) patients. Furazolidone was mainly used in first- (79%) and second-line (21%) regimens. The methods used to diagnose H. pylori infection were: histology (81%), stool antigen test (64%), 13C-urea breath test (6.6%), and rapid urease test (1.9%). The mITT effectiveness of sequential therapy was 100%; 93% with the triple therapy and 75.5% with quadruple therapy. Compliance was reported in 98% of cases. Adverse events were revealed in 5.7% of patients, mostly nausea (3.8%). No serious adverse events were reported.
Conclusion. Furazolidone containing eradication regimens appear to be an effective and safe empirical therapy in Russia
Charge-transfer complexes of conjugated polymers as intermediates in charge photogeneration for organic photovoltaics
Ultrafast visible-pump/IR-probe spectroscopy is applied to study the wavelength dependence of charge photogeneration in materials based on donor–acceptor charge-transfer complexes (CTCs) of the conjugated polymer MEH-PPV. In binary polymer–acceptor blends, photoexcitation in the absorption band of either CTC or polymer results in similar dynamics of the charge-associated transient absorption. Likewise, in polymer/CTC–acceptor/fullerene ternary blends, where charge separation occurs via a two-step pathway, the photophysics is also independent of excitation wavelength. These similarities in charge dynamics indicate that CTC excited states serve as an intermediate for charge photogeneration. The conclusions of the ultrafast study are supported by photocurrent spectroscopy.
Ultrafast Charge Photogeneration Dynamics in Ground-State Charge-Transfer Complexes Based on Conjugated Polymers
The charge photogeneration and early recombination in MEH-PPV-based charge-transfer complexes (CTCs) and in MEH-PPV/PCBM blend as a reference are studied by ultrafast visible-pump-IR-probe spectroscopy. After excitation of the CTC band, an immediate (<100 fs) electron transfer is observed from the polymer chain to the acceptor with the same yield as in the MEH-PPV/PCBM blend. The forward charge transfer in the CTCs is followed by an efficient (~95%) and fast (<30 ps) geminate recombination. For comparison, the recombination efficiency obtained in the MEH-PPV/PCBM blend does not exceed a mere 50%. Polarization-sensitive experiments demonstrate high (~0.3) values of transient anisotropy for the CTCs polaron band. In contrast, in the MEH-PPV/PCBM blend the dipole moment orientation of the charge-induced transition is less correlated with the polarization of the excitation photon. According to these data, photogeneration and recombination of charges in the CTCs take place locally (i.e., within a single pair of a polymer conjugation segment and an acceptor) while in the MEH-PPV/PCBM blend exciton migration precedes the separation of charges. Results of the ultrafast experiments are supported by photocurrent measurements on the corresponding MEH-PPV/acceptor photodiodes.