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Mitochondrial (dys)function - a factor underlying the variability of efavirenz-induced hepatotoxicity?

2015

Background and Purpose The non-nucleoside analogue reverse transcriptase inhibitor efavirenz is associated with hepatic toxicity and metabolic disturbances. Although the mechanisms involved are not clear, recent evidence has pinpointed a specific mitochondrial action of efavirenz accompanied by the induction of an endoplasmic reticulum (ER) stress/unfolded protein response in human hepatic cells. The aim of this study was to further investigate the involvement of this organelle by evaluating efavirenz's effects in cells lacking functional mitochondria (rho°) and comparing them with those of the typical mitotoxic agent rotenone, a standard complex I inhibitor, and the ER stress inducer thaps…

Metabolites from Combretum dolichopetalum and its associated endophytic fungus Nigrospora oryzae--Evidence for a metabolic partnership.

2015

Abstract A new altersolanol derivative, 4-dehydroxyaltersolanol A ( 9 ), along with two known sesquiterpenoids, ( S )-7′-hydroxyabscisic acid ( 7 ) and ( S )-abscisic acid ( 8 ) were obtained from the endophytic fungus, Nigrospora oryzae , isolated from leaves of Combretum dolichopetalum . The host plant yielded six known compounds including ellagic acid ( 1 ), 3, 3′, 4-tri-O-methylellagic acid ( 2 ), arjunolic acid ( 3 ), 4′-dihydrophaseic acid ( 4 ), echinulin ( 5 ) and arestrictin B ( 6 ). Close structural similarities with regard to compounds 4 , 7 and 8 were observed between the metabolites from the host plant and those of the endophytic fungus. Furthermore compounds 5 and 6 are relate…

Severe Brochostenosis by Oral Propafenone Immediately After Commencing Treatment

2011

Propafenone is a membrane-stabilizing agent belonging to a subgroup of the Vaughan Williams class I antidysrhythmic agents, structurally resembling propranolol and characterized by weaker beta-blocking activity. Despite respiratory complications having been reported as examples of side effects, very few reports have been published in the literature.We describe the case of an elderly woman with a history of hypertension and allergy to Parietaria, grass, olive, mites, and with periodic asthmatic manifestations, for whom the administration of oral propafenone for recurrent supraventricular dysrhythmia was associated with the sudden onset of severe bronchostenosis.A 78-year-old woman was freque…

Antiasthmatic acetophenones - an in vivo study on structure activity relationship.

1994

The recently isolated acetophenone glucoside androsin, as the major antiasthmatic principle of Picrorhiza kurroa Royle ex Benth. (Scrophulariaceae), was used as a lead compound for detailed structure-activity relationship studies. More than 25 synthesized or commercially available acetophenones with modified substitution patterns were screened in the Plethysmographic guinea pig model using PAF and/or ovalbumin as challenging agents for the generation of bronchial constriction. Whereas the aglycones in most cases were more effective than the corresponding glycosides, substitution patterns in position 3 and 4 of the phenyl ring and the keto function attached to the phenyl ring were found to b…

Chemically Fueled Volume Phase Transition of Polyacid Microgels

2021

Abstract Microgels are soft colloids that show responsive behavior and are easy to functionalize for applications. They are considered key components for future smart colloidal material systems. However, so far microgel systems have almost exclusively been studied in classical responsive switching settings using external triggers, while internally organized, autonomous control mechanisms as found in supramolecular chemistry and DNA nanotechnology relying on fuel‐driven out‐of‐equilibrium concepts have not been implemented into microgel systems. Here, we introduce chemically fueled transient volume phase transitions (VPTs) for poly(methacrylic acid) (PMAA) microgels, where the collapsed hydr…

Ultrafast electron transfer in photosynthesis: reduced pheophytin and quinone interaction mediated by conical intersections.

2006

The mechanism of electron transfer (ET) from reduced pheophytin (Pheo(-)) to the primary stable photosynthetic acceptor, a quinone (Q) molecule, is addressed by using high-level ab initio computations and realistic molecular models. The results reveal that the ET process involving the (Pheo(-) + Q) and (Pheo + Q(-)) oxidation states can be essentially seen as an ultrafast radiationless transition between the two hypersurfaces taking place via conical intersections (CIs). According to the present findings, an efficient ultrafast ET implies that the Pheo- and Q move toward each other in a given preferential parallel orientation, reaching the most effective arrangement for ET at intermolecular…

IS MEANING WITHOUT ACTUALLY EXISTING REFERENCE NATURALIZABLE?

1995

Intramolecular Interactions in the Triplet Excited States of Benzophenone–Thymine Dyads

2005

Time-resolved and product studies on the synthesized dyads 1 and 2 have provided evidence that the benzophenone-to-thymine orientation strongly influences intramolecular photophysical and photochemical processes. The prevailing reaction mechanism has been established as a Paterno-Büchi cycloaddition to give oxetanes 3-6; however, the ability of benzophenone to achieve a formal hydrogen abstraction from the methyl group of thymidine has also been evidenced by the formation of photoproducts 7 and 8. These processes have been observed only in the case of the cisoid dyad 1. Adiabatic photochemical cycloreversion of the oxetane ring is achieved upon direct photolysis to give the starting dyad 1 …

On the photoelectron spectrum ofp-benzoquinone

2001

A high-resolution photoelectron spectrum of p-benzoquinone in the low energy (9.5–11.5 eV) region is reported and analyzed with the aid of simulations based on high-level ab initio calculations. The results generally support the notion that the two prominent spectral features in this region are each due to a pair of final ion states. The lower energy feature beginning near 10 eV is due to oxygen lone-pair ionizations, while that beginning near 11 eV comes from π electron removal. Contrary to previous interpretations of the spectrum, however, the results of this study indicate that the two π states are nearly degenerate, with the strongest peak in the photoelectron spectrum representing a co…

Fluorescence induction kinetics as a tool to detect a chlororespiratory activity in the prasinophycean alga, Mantoniella squamata

1990

Abstract Pulse-modulated fluorescence measuring systems were used to study the fluorescence induction kinetics of the primitive prasinophycean alga, Mantoniella squamata . DCMU-treated cells show a very strong non-photochemical quenching which is insensitive to uncouplers and can not be attributed to state transitions or photoinhibition. In order to analyze the origin for this quenching, different inhibitors of the photosynthetic electron flow were applied. It was found that DCCD, an inhibitor of the ATP-synthase as well as of the cytochrome- c oxidase, enhances the fluorescence quenching, whereas antimycin A, which blocks the cyclic electron flow around PS I, stimulates it. The effect of b…