Atypical properties of several classes of antipsychotic drugs on the basis of differential induction of Fos-like immunoreactivity in the rat brain

Acute administration of typical and atypical antipsychotics has been reported to induce regionally distinct patterns of c-Fos expression in the rat forebrain. Furthermore, atypical index, the difference in the extent of increased Fos-like immunoreactivity (Fos-LI) in the nucleus accumbens (NAc) shell versus the dorsolateral striatum (DLSt), has been proposed to classify antipsychotics into typical or atypical antipsychotics. The present study was conducted to investigate the atypical properties of 24 antipsychotics that are used in Japan and blonanserin, a novel 5-HT2A and D2 receptor antagonist. We systematically examined the effects of the drugs on Fos-LI in the NAc and DLSt in the rat brain using immunohistochemistry and calculated the atypical index, comparing with those of haloperidol and clozapine. Floropipamide, oxypertine, nemonapride, pimozide and mosapramine, as well as clozapine, olanzapine, quetiapine and risperidone, showed high positive atypical index. Zotepine, perospirone, sulpiride, moperone, sultopride, thioridazine, carpipramine, clocapramine and blonanserin showed moderate ones. In contrast, fluphenazine, bromperidol, timiperone, spiperone, propericiazine, perphenazine, chlorpromazine and levomepromazine had negative atypical index like haloperidol. These results suggest that not only so-called atypical antipsychotics, but also several conventional drugs, possess atypical properties.     

Novel anticancer agents, kayeassamins A and B from the flower of Kayea assamica of Myanmar

The CHCl(3)-soluble fraction of 70% EtOH extract of the flower of Kayea assamica completely killed human pancreatic PANC-1 cancer cells preferentially under nutrient-deprived conditions at 1 microg/mL. Bioassay-guided fractionation and isolation afforded two novel compounds, kayeassamins A (1) and B (2). Their structures were elucidated using extensive spectroscopic methods and the modified Mosher method. Each compound showed 100% preferential cytotoxicity (PC(100)) against PANC-1 cells under nutrient-deprived conditions at 1 microM. Furthermore, both compounds inhibited the migration of PANC-1 cells in the wound closure assay.     

Structural dynamics of proximal heme pocket in HemAT-Bs associated with oxygen dissociation

HemAT from Bacillus subtilis (HemAT-Bs) is a heme-containing O₂ sensor protein that acts as a chemotactic signal transducer. Binding of O₂ to the heme in the sensor domain of HemAT-Bs induces a conformational change in the protein matrix, and this is transmitted to a signaling domain. To characterize the specific mechanism of O₂-dependent conformational changes in HemAT-Bs, we investigated time-resolved resonance Raman spectra of the truncated sensor domain and the full-length HemAT-Bs upon O₂ and CO dissociation. A comparison between the O₂ and CO complexes provides insights on O₂/CO discrimination in HemAT-Bs. While no spectral changes upon CO dissociation were observed in our experimental time window between 10 ns and 100 μs, the band position of the stretching mode between the heme iron and the proximal histidine, ν(Fe–His), for the O₂-dissociated HemAT-Bs was lower than that for the deoxy form on time-resolved resonance Raman spectra. This spectral change specific to O₂ dissociation would be associated with the O₂/CO discrimination in HemAT-Bs. We also compared the results obtained for the truncated sensor domain and the full-length HemAT-Bs, which showed that the structural dynamics related to O₂ dissociation for the full-length HemAT-Bs are faster than those for the sensor domain HemAT-Bs. This indicates that the heme proximal structural dynamics upon O₂ dissociation are coupled with signal transduction in HemAT-Bs.     

Glibenclamide blocks volume-sensitive Cl- channels by dual mechanisms

To study the mechanisms of glibenclamide actions onvolume-sensitive Clchannels, whole cell patch-clamp studies were performed at various pHlevels in human epithelial Intestine 407 cells. Extracellular application of glibenclamide reversibly suppressed volume-sensitive Cl currents in the entirerange of voltage examined (100 to +100 mV) and accelerated thedepolarization-induced inactivation at pH 7.5. When glibenclamide wasapplied from the intracellular side, in contrast, no effect wasobserved. At acidic pH, at which the weak acid glibenclamide existslargely in the uncharged form, the instantaneous current was, in avoltage-independent manner, suppressed by the extracellular drug atmicromolar concentrations without significantly affecting thedepolarization-induced inactivation. At alkaline pH, at which almostall of the drug is in the charged form, glibenclamide speeded theinactivation time course and induced a leftward shift of thesteady-state inactivation curve at much higher concentrations. Thus itis concluded that glibenclamide exerts inhibiting actions onswelling-activated Clchannels from the extracellular side and that the uncharged form ismainly responsible for voltage-independent inhibition of instantaneous currents, whereas the anionic form facilitates voltage-dependent channel inactivation in human epithelial Intestine 407 cells.

     

Oscillations of cytoplasmic concentrations of Ca2+ and K+ in fused L cells

Summary Using Ca²⁺- and K⁺-selective microelectrodes, the cytosolic free Ca²⁺ and K⁺ concentrations were measured in mouse fibroblastic L cells. When the extracellular Ca²⁺ concentration exceeded several micromoles, spontaneous oscillations of the intracellular free Ca²⁺ concentration were observed in the submicromolar ranges. During the Ca²⁺ oscillations, the membrane potential was found to oscillate concomitantly. The peak of cyclic increases in the free Ca²⁺ level coincided in time with the peak of periodic hyperpolarizations. Both oscillations were abolished by reducing the extracellular Ca²⁺ concentration down to 10^–7 m or by applying a Ca²⁺ channel blocker, nifedipine (50 m). In the presence of 0.5mm quinine, an inhibitor of Ca²⁺-activated K⁺ channel, sizable Ca²⁺ oscillations still persisted, while the potential oscillations were markedly suppressed. Oscillations of the intracellular K⁺ concentration between about 145 and 140mm were often associated with the potential oscillations. The minimum phase of the K⁺ concentration was always 5 to 6 sec behind the peak hyperpolarization. Thus, it is concluded that the oscillation of membrane potential results from oscillatory increases in the intracellular Ca²⁺ level, which, in turn, periodically stimulate Ca²⁺-activated K⁺ channels.     

The synergic modeling for the binding of fluoroquinolone antibiotics to the hERG potassium channel

The fluoroquinolone antibiotic binding site in the hERG potassium channel was examined for the residues involved and their position in the tetrameric channel. The blocking effect of the two fluoroquinolones levofloxacin and sparfloxacin to tandem dimers of the hERG mutants were evaluated electrophysiologically. The results indicated that two Tyr652s in the neighboring subunits and one or two Phe656s in the diagonal subunits contributed to the blockade in the case of both compounds, and Ser624 was also involved. The docking studies suggested that the protonated carboxyl group in the compounds strongly interacts with Phe656 as a π acceptor.     

Functional characterization of betaine/proline transporters in betaine-accumulating mangrove

Betaine is an important osmoprotectant in many plants, but its transport activity has only been demonstrated using a proline transporter from tomato, a betaine-nonaccumulating plant. In this study, two full-length and one partial transporter genes were isolated from betaine-accumulating mangrove Avicennia marina. Their homologies to betaine transporters from bacteria and betaine/4-aminobutyrate transporters from mammalian cells were low but were high to proline transporters from Arabidopsis and tomato. Two full-length transporters could complement the Na(+)-sensitive phenotype of the Escherichia coli mutant deficient in betT, putPA, proP, and proU. Both transporters could efficiently take up betaine and proline with similar affinities (K(m), 0.32-0.43 mm) and maximum velocities (1.9-3.6 nmol/min/mg of protein). The uptakes of betaine and proline were significantly inhibited by mono- and dimethylglycine but only partially inhibited by betaine aldehyde, choline, and 4-aminobutyrate. Sodium and potassium chloride markedly enhanced betaine uptake rates with optimum concentrations at 0.5 m, whereas sucrose showed only modest activation. The change of amino acids Thr(290)-Thr-Ser(292) in a putative periplasmic loop to Arg(290)-Gly-Arg(292) yielded the active transporter independent of salts, suggesting the positive charge induced a conformational change to the active form. These data clearly indicate that the betaine-accumulating mangrove contains betaine/proline transporters whose properties are distinct from betaine transporters of bacteria and mammalian cells.     

Flavanone glycosides from viscum coloratum and their inhibitory effects on osteoclast formation

Two novel flavanone glycosides, homoeriodictyol 7‐O‐β‐D ‐[6‐(3‐hydroxybutanoyl)glucopyranoside] (viscumneoside IX; 1 ) and homoeriodictyol 7‐O‐β‐D ‐[6‐(3‐hydroxybutanoyl)glucopyranosyl](1→2)‐β‐D ‐glucopyranoside (viscumneoside X; 2 ), together with four known flavanoids, 2‐homoeriodictyol 7‐O‐β‐D ‐glucopyranoside ( 3 ), viscumneoside I ( 4 ), viscumneoside III ( 5 ), and 4′,5‐dihydroxy‐3′‐methoxy‐7‐(2‐O‐α‐L ‐rhamnopyranosyl‐β‐D ‐glucopyranosyloxy)flavanone ( 6 ) were isolated from stems and leaves of Viscum coloratum. Their structures were elucidated on the basis of their NMR spectra, HR‐FAB‐MS data, and acid hydrolysis. Inhibitory effects of the four compounds 1 – 4 on the formation of osteoclast‐like multinucleated cells were investigated. As a result, all the four flavanoids showed significant inhibitory effects on the formation of osteoclast‐like multinuclear cells even at a low concentration of 2 μg/ml. The activities of 1 – 4 at such a concentration exceeded or approximated to that of elcitonin, the positive control drug at a concentration of 2 U/ml, suggesting that they may be of interest for the development of new anti‐osteoporosis drugs.