Foraging across the life span: is there a reduction in exploration with aging?

Does foraging change across the life span, and in particular, with aging? We report data from two foraging tasks used to investigate age differences in search in external environments as well as internal search in memory. Overall, the evidence suggests that foraging behavior may undergo significant changes across the life span across internal and external search. In particular, we find evidence of a trend toward reduced exploration with increased age.

Mechanisms of age-related decline in memory search across the adult life span.

Three alternative mechanisms for age-related decline in memory search have been proposed, which result from either reduced processing speed (global slowing hypothesis), overpersistence on categories (cluster-switching hypothesis), or the inability to maintain focus on local cues related to a decline in working memory (cue-maintenance hypothesis). We investigated these 3 hypotheses by formally modeling the semantic recall patterns of 185 adults between 27 to 99 years of age in the animal fluency task (Thurstone, 1938). The results indicate that people switch between global frequency-based retrieval cues and local item-based retrieval cues to navigate their semantic memory.

Calmodulin inhibitors from Aspergillus stromatoides.

An organic extract was prepared from the culture medium and mycelia of the marine fungus Aspergillus stromatoides RAPER & FENNELL. The extract was fractionated via column chromatography, and the resulting fractions were tested for their abilities to quench the fluorescence of the calmodulin (CaM) biosensor hCaM M124C-mBBr. From the active fraction, emodin (1) and ω-hydroxyemodin (2) were isolated as CaM inhibitors.

Large Density-Functional and Basis-Set Effects for the DMSO Reductase Catalyzed Oxo-Transfer Reaction.

The oxygen-atom transfer reaction catalyzed by the mononuclear molybdenum enzyme dimethyl sulfoxide reductase (DMSOR) has attracted considerable attention through both experimental and theoretical studies. We show here that this reaction is more sensitive to details of quantum mechanical calculations than what has previously been appreciated. Basis sets of at least triple-ζ quality are needed to obtain qualitatively correct results.

Importance of the interaction protein-protein of the CaM-PDE1A and CaM-MLCK complexes in the development of new anti-CaM drugs.

Protein-protein interactions play central roles in physiological and pathological processes. The bases of the mechanisms of drug action are relevant to the discovery of new therapeutic targets. This work focuses on understanding the interactions in protein-protein-ligands complexes, using proteins calmodulin (CaM), human calcium/calmodulin-dependent 3',5'-cyclic nucleotide phosphodiesterase 1A active human (PDE1A), and myosin light chain kinase (MLCK) and ligands αII-spectrin peptide (αII-spec), and two inhibitors of CaM (chlorpromazine (CPZ) and malbrancheamide (MBC)).

Mexican antidiabetic herbs: valuable sources of inhibitors of α-glucosidases.

Type II-diabetes mellitus (TII-DM) has been regarded as one of the most important public health problems in all nations in the 21st century. Although allopathic therapies remain the most important for the initial management of TII-DM, herbal remedies have gained wide acceptance for treating this condition. These alternative therapies are particularly valued in countries such as Mexico, rich in medicinal plants strongly attached to the cultural values of the population.

Reaction of N-heterocyclic silylenes with thioketone: formation of silicon-sulfur three (Si-C-S)- and five (Si-C-C-C-S)-membered ring systems.

Three- and five-membered rings that bear the (Si-C-S) and (Si-C-C-C-S) unit have been synthesized by the reactions of LSiCl (1; L=PhC(NtBu)2 ) and L'Si (2; L'=CH{(CCH2 )(CMe)(2,6-iPr2 C6 H3 N)2 }) with the thioketone 4,4'-bis(dimethylamino)thiobenzophenone. Treatment of 4,4'-bis(dimethylamino)thiobenzophenone with LSiCl at room temperature furnished the [1+2]-cycloaddition product silathiacyclopropane 3. However, reaction of 4,4'-bis(dimethylamino)thiobenzophenone with L'Si at low temperature afforded a [1+4]-cycloaddition to yield the five-membered ring product 4.

Gastroprotective effect of Hintonia latiflora and Hintonia standleyana aqueous extracts and compounds.

Ethnopharmacological Relevance: The stem-barks of Hintonia latiflora and Hintonia standleyana, locally known as "copalchi", are used for treating several maladies such as diabetes and gastrointestinal complaints, including gastric ulcers. Although the antidiabetic properties have been demonstrated, the gastroprotective action remains unexplored.

Aim Of The Study: The main goals of this study were to establish the potential acute toxicity and the gastroprotective activity of aqueous extracts and compounds from Hintonia latiflora and Hintonia standleyana in order to demonstrate their preclinical efficacy for the treatment of gastric ulcers in Mexican folk medicine.

The layered structure of [Na(NH3)4][Indenide] containing a square-planar Na(NH3)4(+) cation.

It's hip to be a square! The ammines [Li(NH(3))(4)][Ind] and [Na(NH(3))(4)][Ind] both contain a cation coordinated by four ammonia molecules. Whereas the first shows the anticipated tetrahedral coordination, in the second the metal coordination is unexpectedly square-planar. The solvent-separated ion pair forms a rippled layer structure of alternating planar Na(NH(3))(4)(+) cations and indenyl carbanions that is attributed to NH(3) ⋅⋅⋅π hydrogen bonds.

HPLC determination of the major active flavonoids and GC-MS analysis of volatile components of Dysphania graveolens (Amaranthaceae).

Introduction: Dysphania graveolens is used mainly in Mexican traditional medicine against gastrointestinal ailments. Previous investigations revealed that its flavonoids are important active principles; however, there is not a reliable and accurate analytical method for determining these compounds in the crude drug or preparations of the plant. In addition, its volatile chemical composition remains unknown.

Application of Local Second-Order Møller-Plesset Perturbation Theory to the Study of Structures in Solution.

In this work, we discuss the use of local second order Møller-Plesset perturbation theory (LMP2) in combination with the COSMO continuum solvation model for obtaining optimized geometries of molecules in solution. Density-fitting approximations, which reduce the computational cost relative to the basis set size, are also applied. We present results for small molecular systems, which show the same pattern observed in gas phase calculations.

(+)-Ascosalitoxin and vermelhotin, a calmodulin inhibitor, from an endophytic fungus isolated from Hintonia latiflora.

Chemical investigation of the endophytic MEXU 26343, isolated from the medicinal plant Hintonia latiflora, yielded the known polyketide vermelhotin (1) and a new salicylic aldehyde derivative, namely, 9S,11R-(+)-ascosalitoxin (2). The structure and absolute configuration of the new compound were established through extensive NMR spectroscopy and molecular modeling calculations at the DFT B3LYP/DGDZVP level, which included the comparison between theoretical and experimental optical rotation values. In addition, chemical transformations of 2 yielded suitable derivatives for NOESY and (1)H-(1)H NMR coupling constant analyses, which reinforce the stereochemical assignment.

A push-and-pull model for allosteric anion binding in cage complexes.

A series of electronic structure calculations has been carried out on an artificial anion binding host. The compound with four Pd(II) cations and a total of eight bis-monodentate pyridyl ligands forms by self-assembly an interpenetrated double cage with three binding pockets. Through the use of a simple push-and-pull model connecting the potentials of the different sites, we are able to explain the allosteric effect observed in anion binding.

The last globally stable extended alkane.

Mother of all folding: cold isolated linear alkanes C(n)H(2n+2) prefer an extended all-trans conformation before cohesive forces between the chain ends induce a folded hairpin structure for longer chains. It is shown by Raman spectroscopy at 100-150 K that the folded structure becomes more stable beyond n(C) = 17 or 18 carbon atoms. High-level quantum-chemical calculations yield n(C) = 17 ± 1 as the critical chain length.

DAT1 polymorphism is associated with risk taking in the Balloon Analogue Risk Task (BART).

Twin-studies suggest that a significant portion of individual differences in the propensity to take risks resides in people's genetic make-up and there is evidence that variability in dopaminergic systems relates to individual differences in risky choice. We examined the link between risk taking in a risk taking task (the Balloon Analogue Risk Task, BART) and a variable number tandem repeat (VNTR) polymorphism in the 3'UTR of the dopamine transporter gene (SLC6A3/DAT1). Behavior in BART is known to be associated with activity in striatal reward-processing regions, and DAT1 is assumed to modulate striatal dopamine levels.

Structural diversity in sodium doped water trimers.

The structures of sodium doped water trimers are characterized on the basis of their infrared action spectra in the OH-stretching region and a global optimization approach to identify the lowest energy minima. The most stable structure is an open ring with two contacts of terminal water molecules to the Na atom. This structure explains the dominating feature in the IR depletion spectrum around 3410 cm(-1).

Study of specific ion-amino acid interactions through the use of local correlation methods.

Specific ion effects, related to the hydration of ions and ion-solute interactions, play a fundamental part in many processes in chemistry and biology. Although intensively studied since the seminal studies of Franz Hofmeister and co-workers, their molecular origin has only recently started to be unveiled. In this work, we have investigated the interaction between halide anions and a selected set of amino acid residues in an attempt to identify the forces behind ion specificity.

α-glucosidase inhibitors from Brickellia cavanillesii.

An aqueous extract from the aerial parts of Brickellia cavanillesii attenuated postprandial hyperglycemia in diabetic mice during oral glucose and sucrose tolerance tests. Experimental type-II DM was achieved by treating mice with streptozotocin (100 mg/kg) and β-nicotinamide adenine dinucleotide (40 mg/kg). These pharmacological results demonstrated that B.

Computation of induced dipoles in molecular mechanics simulations using graphics processors.

In this work, we present a tentative step toward the efficient implementation of polarizable molecular mechanics force fields with GPU acceleration. The computational bottleneck of such applications is found in the treatment of electrostatics, where higher-order multipoles and a self-consistent treatment of polarization effects are needed. We have implemented a GPU accelerated code, based on the Tinker program suite, for the computation of induced dipoles.

Monomeric Sn(II) and Ge(II) hydrides supported by a tridentate pincer-based ligand.

Herein we report the syntheses of terminal Sn(II) (3) and Ge(II) (4) hydrides from the corresponding chloride precursors [{2,6-iPr(2)C(6)H(3)NCMe}(2)C(6)H(3)MCl] (M = Sn (1), Ge (2)) using [K{B(sec-Bu)(3)}H] as a hydrogenating agent. Combination of steric shielding and intramolecular N → M interactions resulted in the protection of M(II)-H bonds.

Quantitative HPLC method for determining two of the major active phthalides from Ligusticum porteri roots.

Z-Ligustilide (1) and Z-6,6',7,3'-alpha-diligustilide (2), two of the major active phthalides of the medicinal plant Ligusticum porteri (osha), were chosen for the development and validation of an HPLC-diode array detection method suitable for QC of the crude drug. The method used gradient elution to achieve separation on a Hibar RT LiChrospher 100 C18 column. The LOD values were 29 and 45 microg/mL, and the LOQs were 89 and 125 microg/mL, respectively.

Losing a dime with a satisfied mind: positive affect predicts less search in sequential decision making.

We investigated the contribution of cognitive ability and affect to age differences in sequential decision making by asking younger and older adults to shop for items in a computerized sequential decision-making task. Older adults performed poorly compared to younger adults partly due to searching too few options. An analysis of the decision process with a formal model suggested that older adults set lower thresholds for accepting an option than younger participants.

Atomdroid: a computational chemistry tool for mobile platforms.

We present the implementation of a new molecular mechanics program designed for use in mobile platforms, the first specifically built for these devices. The software is designed to run on Android operating systems and is compatible with several modern tablet-PCs and smartphones available in the market. It includes molecular viewer/builder capabilities with integrated routines for geometry optimizations and Monte Carlo simulations.

Ecological rationality: a framework for understanding and aiding the aging decision maker.

The notion of ecological rationality sees human rationality as the result of the adaptive fit between the human mind and the environment. Ecological rationality focuses the study of decision making on two key questions: First, what are the environmental regularities to which people's decision strategies are matched, and how frequently do these regularities occur in natural environments? Second, how well can people adapt their use of specific strategies to particular environmental regularities? Research on aging suggests a number of changes in cognitive function, for instance, deficits in learning and memory that may impact decision-making skills. However, it has been shown that simple strategies can work well in many natural environments, which suggests that age-related deficits in strategy use may not necessarily translate into reduced decision quality.