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At least 973 records · Page 54Linked to original sources
PubMed1995

Dorsal hippocampal lesions impair blocking but not latent inhibition of taste aversion learning in rats.

The aim of the present experiments was to study the effect of nonselective electrolytic lesions of the rat dorsal hippocampus on 2 learning phenomena: the L.J. Kamin (1969) blocking effect and latent inhibition of taste aversion learning. Bilateral dorsal hippocampal lesions selectively impaired blocking induced by 1 saccharin-lithium chloride pairing previous to 1 serial compound (saccharin-cider vinegar)-lithium pairing, but lesions had no effect on latent inhibition of a saline aversion, induced by 6 saline preexposures, in the same group of animals. Moreover, dorsal hippocampal lesions did not affect latent inhibition of saccharin-conditioned aversion induced by 1 or 6 preexposures. It is argued that blocking and latent inhibition of taste aversion learning do not share a common neural mechanism.

Animals↗
PubMed2007

Dehalogenation of 1,3-diiodotricyclo[3.3.0.0(3,7)]octane: generation of 1,3-dehydrotricyclo[3.3.0.0(3,7)]octane, a 2,5-methano-bridged [2.2.1]propellane.

Compounds isolated from the reaction of (+/-)-1,3-diiodotricyclo[3.3.0.0(3,7)]octane with molten sodium or tBuLi suggest the intermediate formation of (+/-)-1,3-dehydrotricyclo[3.3.0.0(3,7)]octane. Worthy of note is the formation of stereoisomeric bi(5-methylenebicyclo[2.2.1]hept-2-ylidene) derivatives, probably by coupling of two units of (+/-)-1,3-dehydrotricyclo[3.3.0.0(3,7)]octane of the same or different absolute configuration followed by fragmentation, processes that have been studied by theoretical calculations.

Algorithms↗
PubMed2003

No-carrier-added synthesis of aliphatic and aromatic radioselenoethers via selenocyanates.

Various aliphatic and aromatic [(75)Se]selenoethers were prepared at the no-carrier-added (n.c.a.) level using a new radiosynthetic pathway, based on the formation of alkyl[(75)Se]selenocyanates as intermediates. Using one-pot model reactions of elemental (75)Se, sodium cyanide and various alkylbromides in ethanol, the preparation of alkyl[(75)Se]selenocyanates was examined and optimized. Purification of these (75)Se-labeled intermediates and subsequent conversion with alkyl and aryl lithium or Grignard compounds in anhydrous diethyl ether yielded radioselenoethers with radiochemical yields of up to 55% (related to (75)Se(0)) within an overall reaction time of 20 min. This is the first method described to obtain n.c.a. arylselenoethers.

Cyanates↗
PubMed2005

Neuropeptide Y and corticotropin-releasing hormone in CSF mark response to antidepressive treatment with citalopram.

Neuropeptides appear to play a role in the pathophysiology of depression and electroconvulsive treatment and lithium affect these compounds in human cerebrospinal fluid (CSF) and rodent brain. Consequently, we investigated whether long-term treatment with the selective serotonin reuptake inhibitor (SSRI) citalopram (Cit) would also affect neuropeptides in CSF of depressed patients. Changes in CSF monoamine metabolites were also explored. CSF concentrations of corticotropin-releasing hormone (CRH)-like immunoreactivity (-LI), neuropeptide Y (NPY)-LI, and Cit were determined in 21 patients with major depression. Lumbar puncture was performed in the morning at baseline and was repeated after at least 4 wk of Cit treatment (40 mg/d). The severity of depression was assessed by the Hamilton Rating Scale for Depression (HAMD). Cit treatment was associated with a significant increase in NPY-LI and decrease in CRH-LI. An evaluation of the relationship between changes in concentrations of NPY-LI, CRH-LI, and the clinical response showed significant correlations between these parameters. Significant NPY and CRH changes in CSF following treatment as well as correlations to changes in HAMD support the hypothesis that these two peptides play a role in affective disorders and are markers of therapeutic response.

Adult↗
PubMed2004

Carbolithiation for the generation of cyclooctadienyl anions and tandem electrocyclization/alkylation to functionalized cis-bicyclo[3.3.0]octenes.

A powerful cascade reaction process for the construction of functionalized cis-bicyclo[3.3.0]octenes has been developed. Carbolithiation of 3-methylene-1,4-cyclooctadiene with 1 degrees , 2 degrees , or 3 degrees alkyllithium reagents leads to cyclooctadienyl anions, which undergo disrotatory electrocyclization and subsequent trapping with carbon, oxygen, sulfur, or silicon electrophiles to provide functionalized cis-bicyclo[3.3.0]octenes. Transmetalation of the allyllithium intermediates allowed access to the cuprate manifold of reactivity. The rapid construction of a linear triquinane using this methodology demonstrates the potential for synthetic applications.

Alkenes↗
PubMed2006

Studies of the generation and pericyclic behavior of cyclic pentadienyl carbanions. Alkylation reactions as an efficient route to functionalized cis-bicyclo[3.3.0]octenes.

Carbolithiation has been studied with alkyllithium reagents in a series of six- through nine-membered 3-methylene-1,4-cycloalkadienes, efficiently producing the corresponding cyclic pentadienyl carbanions. These pentadienyl anions display unique reactivity, depending on ring size. Cyclooctadienyl anions readily undergo disrotatory electrocyclization to cis-bicyclo[3.3.0]octenyl systems, which are trapped with a variety of electrophiles to stereoselectively provide functionalized cis-bicyclo[3.3.0]octenes. The carbolithiation and electrocyclization processes are examined using low-temperature (1)H NMR experiments. An expedient synthesis of a linear triquinane illustrates this methodology. Electrocyclization of the corresponding cyclononadienyl anion requires unusually high temperatures (120 degrees C), and computational studies provide insights into this change in reactivity. Cycloheptadienyl and cyclohexadienyl anions, generated via carbolithiation, provide functionalized cycloheptadienes and cyclohexadienes upon electrophilic capture. Trapping experiments reveal that the cycloheptadienyl anions are transformed to heptatrienyl anions. A series of experiments have been designed to explore evidence for the feasibility of equilibration of open and closed anionic systems, and these studies report the first isolation of a cis-bicyclo[3.1.0]hexene derived from electrocyclization of a cyclohexadienyl carbanion.

Alkadienes↗
PubMed1987

Synthesis and evaluation of mono-, di-, and trifluoroethenyl-GABA derivatives as GABA-T inhibitors.

The syntheses of four derivatives of gamma-vinyl-GABA, in which vinylic hydrogen atoms were replaced by fluorine, are described. With use of 5-ethenyl-2-pyrrolidinone as starting material, the E and Z isomers of 4-amino-6-fluoro-5-hexenoic acid were prepared. The 6,6-difluoro and 5,6,6-trifluoro analogues could be synthesized from 4-oxobutanoic acid tert-butyl ester and (2,2-difluoroethenyl)- and (trifluoroethenyl)lithium correspondingly. The compounds were tested as inhibitors of GABA-T, and their in vitro and in vivo biochemistry is reported. The most active derivative was (Z)-4-amino-6-fluoro-5-hexenoic acid; the structure-activity relationship in the series is discussed.

4-Aminobutyrate Transaminase↗
PubMed2005

Experimental and computational study of the electronic structural changes in LiTi2O4 spinel compounds upon electrochemical Li insertion reactions.

Electronic structural changes in LiTi(2)O(4) spinel compounds upon electrochemical lithium insertions were investigated by X-ray absorption spectroscopy (XAS) measurements and first principles calculations based on spin-polarized density functional theory. Ti K-edge, O K-edge XAS spectra and theoretical calculations indicate that oxide ions as well as titanium ions are involved in electronic structural changes caused by electrochemical lithium ion insertions. The considerable effect of the oxide ions in the early 3d transition metal (titanium) oxide system is discussed in this article.

Computer Simulation↗
PubMed1967

Preparation, properties and metabolism of 5,6-monoepoxyretinoic acid.

1. Methyl retinoate has been converted into methyl 5,6-monoepoxyretinoate by reaction with monoperphthalic acid. The epoxy acid ester on alkaline hydrolysis gave 5,6-monoepoxyretinoic acid. 2. Treatment of the 5,6-monoepoxy compounds with ethanolic hydrochloric acid gave the corresponding 5,8-epoxy (furanoid) compounds. 3. With lithium aluminium hydride, the acid and the ester groups were selectively reduced to primary alcohols. 4. Administration of methyl 5,6-monoepoxyretinoate intraperitoneally and subcutaneously had good growth response in vitamin A-deficient rats. 5. 5,6-Monoepoxyretinoic acid, when given intraperitoneally as the sodium salt, was 157% as active as all-trans-retinyl acetate. 6. Methyl 5,6-monoepoxyretinoate was hydrolysed to the epoxy acid by rat-liver homogenate. It had 35% of the biological activity of all-trans-retinyl acetate in the rat when given orally.

Acetates↗
PubMed1991

Pharmacokinetic interactions with calcium channel antagonists (Part I).

Calcium channel antagonists are a diverse class of drugs widely used in combination with other therapeutic agents. The potential exists for many clinically significant pharmacokinetic interactions between these and other concurrently administered drugs. The mechanisms of calcium channel antagonist-induced changes in drug metabolism include altered hepatic blood flow and impaired hepatic enzyme metabolising activity. Increases in serum concentrations and/or reductions in clearance have been reported for several drugs used with a number of calcium channel antagonists. A number of reports and studies of calcium channel antagonist interactions have yielded contradictory results and the clinical significance of pharmacokinetic changes seen with these agents is ill-defined. The first part of this article deals with interactions between calcium antagonists and marker compounds, theophylline, midazolam, lithium, doxorubicin, oral hypoglycaemics and cardiac drugs.

Anti-Arrhythmia Agents↗
PubMed1991

Pharmacokinetic interactions with calcium channel antagonists (Part II).

Since calcium channel antagonists are a diverse class of drugs frequently administered in combination with other agents, the potential for clinically significant pharmacokinetic drug interactions exists. These interactions occur most frequently via altered hepatic blood flow and impaired hepatic enzyme activity. Part I of the article, which appeared in the previous issue of the Journal, dealt with interactions between calcium antagonists and marker compounds, theophylline, midazolam, lithium, doxorubicin, oral hypoglycaemics and cardiac drugs. Part II examines interactions with cyclosporin, anaesthetics, carbamazepine and cardiovascular agents.

Anesthetics↗
PubMed1988

The structures of katanosins A and B.

1H and 13C NMR studies on katanosin A confirmed the presence of eight usual amino acid residues which were previously deduced by amino acid analysis and suggested the presence of beta-hydroxyaspartic acid, beta-hydroxyleucine and beta-phenylserine residues. These amino acids were isolated and confirmed, including their stereochemistries, by comparison with the respective authentic specimens. Stereochemistries of the usual amino acids were determined by comparing the L-leucylated amino acids with reference compounds by HPLC. Lithium borohydride reduction and chromic acid oxidation of katanosin A and alkali-treated katanosin A elucidated a lactone linkage between the C-terminal Ser and phenylserine residues. Edman degradation on alkali-treated katanosin A clarified the total amino acid sequence. The difference in katanosins A and B was determined to be replacement of Val in A by Ile in B. Thus, the structures of katanosins A and B were elucidated.

Amino Acid Sequence↗
PubMed2004

[Bipolarity: from manic-depressive disease to bipolar disorder].

Until recently, bipolar disorder was viewed as a relatively rare condition characterized by periods of euphoric excitement and depressive retardation which was easy to diagnose, and easy to treat thanks with lithium and new prophylactic treatments. In fact, bipolar disorder encompasses a variety of conditions, whose overall lifetime prevalence in the general population may be between 5 and 8%. Long term with lithium and other compounds are very effective but must be combined with non pharmacological therapies. Over the past two decades, advances in genetic, brain imagings, and biochemical have improved our knowledge on the pathophysiological mechanisms underlying these disorders.

Bipolar Disorder↗
PubMed2005

[Study on microwave-templated synthesis mechanism of LiMn2O4 by infrared spectroscopy].

In this paper, LiMn2O4 was synthesized by the microwave-template method, and the synthesis mechanism was studied by the in-situ FTIR. It was confirmed by the FTIR that polyacrylamide was decomposed gradually during the spinel LiMn2O4 preparation, and there was some chemical bond between the reactants and polyacrylamide in the precursors. Polyacrylamide acted as template in the course of the preparation of precursors and forming of spinel lithium manganese oxide compound. As a result of the certain chemical bond, the controlling and adjusting of the LiMn2O4 crystalline were realized, so that agglomeration and lacunae framework of the spinel was adjusted.

English Abstract↗
PubMedDate not supplied

Structure and ionic interactions of organic-inorganic composite polymer electrolytes studied by solid-state NMR and Raman spectroscopy.

Solid-state NMR studies of composite polymer electrolytes are reported. The materials consist of polyethylene oxide and an organic inorganic composite, together with a lithium salt, and are candidates for electrolytes in solid-state lithium ion batteries. Silicon and aluminum MAS and multiple quantum MAS are used to characterize the network character of the organic-inorganic composite, and spin diffusion measurements are used to determine the nanostructure of the polymer/composite blending. Multiple quantum spin counting is used to measure the ion aggregation. The NMR results are supported by Raman spectra, calorimetry, and impedance spectroscopy. From these experiments it is concluded that the composite suppresses polymer crystallization without suppressing its local mobility, and also suppresses the tendency for the ions to aggregate. This polymer composite thus appears very promising for application in lithium ion batteries.

Aluminum↗