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At least 1,009 records · Page 56Linked to original sources
PubMed2005

Organic crystal engineering with 1,4-piperazine-2,5-diones. 6. Studies of the hydrogen-bond association of cyclo[(2-methylamino-4,7-dimethoxyindan-2-carboxylic acid)(2-amino-4,7-dimethoxyindan-2-carboxylic acid)].

[structure: see text] The title 1,4-piperazine-2,5-dione was synthesized in 23% yield over six steps from ethyl 2-amino-4,7-dimethoxyindan-2-carboxylate. Crystallization by slow diffusion of ether into a chloroform solution and by slow evaporation of an ethanol-chloroform-benzene solution produced polymorphic crystalline forms as determined by single-crystal X-ray analysis. The polymorphs exhibited different hydrogen-bonding networks. The association of this piperazinedione in solution was studied using mass spectrometric and nuclear magnetic resonance spectroscopic techniques. The MS and NMR data were interpreted using the solid-state structures as models for solution aggregation. Association constants extracted from the NMR data are in line with those of other cyclic cis amides in chloroform solvent.

Carboxylic Acids↗
PubMed1996

Development of Molecular Mechanics Torsion Parameters for alpha,beta-Cyclopropyl Ketones and Conformational Analysis of Bicyclo[m.1.0]alkan-2-ones.

Conformations of cyclopropyl methyl ketone have been studied using ab initio methods in an effort to quantify the effects of conjugative overlap between the cyclopropane ring and an adjacent ketone carbonyl. Results were comparable with previous experimental and theoretical studies. Cyclopropyl methyl ketone exhibits a global energy minimum in the s-cis conformer and a local energy minimum near the s-trans conformer. The potential energy curve obtained was used to derive torsion parameters which were employed in molecular mechanics studies of the conformations of the set of bicyclo[m.1.0]alkan-2-ones having larger ring sizes from five- to 16-membered. Similar conformations for the cyclopropyl ketone substructure are observed for all the medium and large ring systems examined. Possible synthetic ramifications of local conformational anchoring by this functional group array are discussed.

Journal Article↗
PubMed1996

Diastereoselective Manipulations of Bicyclo[m.1.0]alkane Derivatives. 2. Nucleophilic Additions to the Carbonyl Carbons of Bicyclo[m.1.0]alkan-2-ones(1).

Enantiomerically enriched bicyclo[m.1.0]alkan-2-ones having larger ring sizes between five and 16 members were prepared and subjected to additions of nucleophiles to the carbonyl carbon. Such additions were efficient and highly diastereoselective for all nucleophiles for bicycles with ring sizes greater than seven. Diastereoselectivity for these additions is rationalized by assuming early transition states and exposure of the same carbonyl face to the ring exterior in the vast majority of populated conformers for each bicyclic ketone.

Journal Article↗
PubMed1997

Diastereoselective Manipulations of Bicyclo[m.1.0]alkane Derivatives. 4. Reactions of Nucleophiles with Bicyclo[m.1.0]alk-3-en-2-ones.

Enantiomerically enriched bicyclo[m.1.0]alk-3-en-2-ones possessing 8-, 12-, and 15-membered rings were prepared and subjected to additions of nucleophiles. 1,2-Additions of n-butyllithium were highly diastereoselective for all cyclopropyl enones examined. Reactions of (Z)-bicyclo[6.1.0]non-3-en-2-one and (E)-bicyclo[13.1.0]hexadec-3-en-2-one with dimethyloxosulfonium methylide were highly diastereoselective, while reaction of (E)-bicyclo[10.1.0]tridec-3-en-2-one with this reagent was not diastereoselective. In contrast, 1,4-additions of lithium diorganocuprates were highly diastereoselective for the 8- and 12-membered enones but were not diastereoselective for the 15-membered enone. All reactions were chemically efficient. The diastereoselectivities observed for 1,2-additions, which are thought to involve early transition states, can be rationalized by consideration of the low-energy conformations of each cyclopropyl enone. The diastereoselectivities observed for 1,4-additions, which may involve late transition states, do not correlate simply with the lowest energy conformations of these enones.

Journal Article↗
PubMed2003

Crystal engineering of a liquid crystalline piperazinedione.

[structure: see text] A molecule designed to self-assemble via hydrogen bonding, arene-arene, and van der Waals interactions and expected to possess thermotropic liquid crystalline properties has been synthesized and characterized. Results support the validity of an assembly paradigm based on incorporation of chemically orthogonal and spatially independent recognition elements in the molecular building blocks.

Journal Article↗
PubMed2001

Monomethylarsonous acid (MMA(III)) and arsenite: LD(50) in hamsters and in vitro inhibition of pyruvate dehydrogenase.

Monomethylarsonous acid (MMA(III)), a metabolite of inorganic arsenic, has received very little attention from investigators of arsenic metabolism in humans. MMA(III), like sodium arsenite, contains arsenic in the +3 oxidation state. Although we have previously demonstrated that it is more toxic than arsenite in cultured Chang human hepatocytes, there are no data showing in vivo toxicity of MMA(III). When MMA(III) or sodium arsenite was administered intraperitoneally to hamsters, the LD(50)s were 29.3 and 112.0 micromol/kg of body wt, respectively. In addition, inhibition of hamster kidney or purified porcine heart pyruvate dehydrogenase (PDH) activity by MMA(III) or arsenite was determined. To inhibit hamster kidney PDH activity by 50%, the concentrations (mean +/- SE) of MMA(III) as methylarsine oxide, MMA(III) as diiodomethylarsine, and arsenite were 59.9 +/- 6.5, 62.0 +/- 1.8, and 115.7 +/- 2.3 microM, respectively. To inhibit activity of purified porcine heart PDH activity by 50%, the concentrations (mean +/- SE) of MMA(III) as methylarsine oxide and arsenite were 17.6 +/- 4.1 and 106.1 +/- 19.8 microM, respectively. These data demonstrate that MMA(III) is more toxic than inorganic arsenite, both in vivo and in vitro, and call into question the hypothesis that methylation of inorganic arsenic is a detoxication process.

Animals↗
PubMed1999

2,2',3,3',6,6'-hexachlorobiphenyl hydroxylation by active site mutants of cytochrome P450 2B1 and 2B11.

The structural basis of species differences in cytochrome P450 2B-mediated hydroxylation of 2,2',3,3',6,6'-hexachlorobiphenyl (236HCB) was evaluated by using 14 site-directed mutants of cytochrome P450 2B1 and three point mutants of 2B11 expressed in Escherichia coli. To facilitate metabolite identification, seven possible products, including three hydroxylated and four dihydroxylated hexachlorobiphenyls, were synthesized by direct functionalization of precursors and Ullmann and crossed Ullmann reactions. HPLC and GC/MS analysis and comparison with authentic standards revealed that 2B1, 2B11, and all their mutants produced 4, 5-dihydroxy-236HCB and 5-hydroxy-236HCB, while 2B11 L363V and 2B1 I114V mutants also catalyzed hydroxylation at the 4-position. The amount of products formed by 2B1 mutants I114V, F206L, L209A, T302S, V363A, V363L, V367A, I477A, I477L, G478S, I480A, and I480L was smaller than that of the wild type. I477V exhibited unaltered 236HCB metabolism, and I480V produced twice as much dihydroxy product as the wild type. For 2B11, substitution of Val-114 or Asp-290 with Ile decreased the product yields. Replacement of Leu-363 with Val dramatically altered the profile of 236HCB metabolites. In addition to an increase in the overall level of hydroxylation, the mutant mainly catalyzed hydroxylation at the 4-position. Incubation of P450 2B1 with 5-hydroxy-236HCB produced 4,5-dihydroxy-236HCB, which indicates that 4,5-dihydroxy-236HCB may be formed by a direct hydroxylation of 5-hydroxy-236HCB. The findings from this study demonstrate the importance of residues 114, 206, 209, 302, 363, 367, 477, 478, and 480 in 2B1 and 114, 290, and 363 in 2B11 for 236HCB metabolism.

Aryl Hydrocarbon Hydroxylases↗
PubMed2002

Rhythmicity of specific and nonspecific resistance in adult women.

We studied biological rhythms of immunological parameters and absorption and digestive activities of neutrophils and monocytes in women during the menstrual cycle. Circadian rhythms of phagocytosis were evaluated. The phagocytic system was characterized by highest activity during ovulation and early luteal phase of the menstrual cycle accompanied by physiological immunosuppression. It was shown that macrophages determine the spatial and temporal organization of specific and nonspecific resistance in women. We evaluated phases of the menstrual cycle optimal for studying rhythms of the immune system and phagocytosis.

Adult↗
PubMed2002

Biorhythms of functional activity of phagocytes in iron deficiency.

Biorhythms of absorption capacity of neutrophils and monocytes were studied in women with latent iron deficiency. We revealed disorders in circadian organization of the mononuclear phagocyte system and decreased reserve capacity of nonspecific organism's resistance against the background of tissue iron deficiency. Informative value of desynchronosis in circadian structure of the phagocyte absorption capacity as the early marker of prelatent iron deficiency was established.

Adult↗
PubMed2001

Families of children with attention-deficit/hyperactivity disorder: review and recommendations for future research.

This review integrates and critically evaluates what is known about family characteristics associated with childhood Attention-Deficit/Hyperactivity Disorder (ADHD). Evidence suggests that the presence of ADHD in children is associated to varying degrees with disturbances in family and marital functioning, disrupted parent-child relationships, specific patterns of parental cognitions about child behavior and reduced parenting self-efficacy, and increased levels of parenting stress and parental psychopathology, particularly when ADHD is comorbid with conduct problems. However, the review reveals that little is known about the developmental mechanisms that underlie these associations, or the pathways through which child and family characteristics transact to exert their influences over time. In addition, the influence of factors such as gender, culture, and ADHD subtype on the association between ADHD and family factors remains largely unknown. We conclude with recommendations regarding the necessity for research that will inform a developmental psychopathology perspective of ADHD.

Attention Deficit Disorder with Hyperactivity↗
PubMed2004

A test of the tripartite model of anxiety and depression in elementary and high school boys and girls.

The applicability of the tripartite model of emotion, which distinguishes the shared aspect of depression and anxiety, negative affect (NA), from their respective specific components of low positive affect (PA) and physiological hyperarousal (PH), was examined in 472 elementary and high school students. The relations among depression, anxiety, and the three tripartite dimensions were examined for the total sample and across four subgroups based on age and gender. High school girls reported more depression, anxiety, NA, and PH than the other groups, and lower PA as assessed by the PANAS-C, but not the AFARS. Using structural equation modeling, the tripartite model proved to be a reasonably good fit for the total sample. Among the subgroups, the best fit was found for high school girls. However, several findings for the total sample and for individual subgroups were not consistent with the tripartite model, raising issues related to the independence and specificity of the tripartite constructs and their measurement. Alternative age- and gender-specific models to better account for the shared and unique aspects of depression and anxiety in children need to be explored.

Adolescent↗
PubMed1999

Assessing social validity in clinical treatment research: issues and procedures.

Social validity is a term coined by behavior analysts to refer to the social importance and acceptability of treatment goals, procedures, and outcomes. This article discusses dimensions of social validity, methods used to evaluate various aspects of social validity, and the applicability of these concepts and methods in clinical treatment research.

Clinical Trials as Topic↗
PubMed2001

Exporting analogue behavioral observation from research to clinical practice: useful or cost-defective?

The special section on analogue behavioral observation (ABO) provided an in-depth review of various ABO assessment procedures. Despite their availability, however, these procedures are rarely used in clinical practice. This may result in part from the traditions on which most ABO assessments are based, from distinctions between clinical and research assessment environments, and from the need for more information about the cost-effectiveness of ABO strategies for meeting specific needs of clinicians in applied settings. Suggestions for bridging the research-clinical gap involve investigating more thoroughly when ABO does and does not provide useful information for various purposes in applied settings and increasing accessibility and cost-effectiveness of ABO procedures for practitioners.

Behavior↗
PubMed2006

What do two-year-olds understand about hidden-object events?

Preferential-looking studies suggest that by 2 months of age, infants may have knowledge about some object properties, such as solidity. Manual search studies of toddlers examining these same concepts, however, have failed to provide evidence for the same understanding. Investigators have recently attempted to reconcile this disparity but failed to control for the visual novelty of test outcomes. The current design corrected this problem and also tested toddlers' predictions of the object's location. The task involved the same events and apparatus that have been used in manual search tasks but used looking as the dependent measure. Children looked longer when an agent opened the correct door and found no ball than when an incorrect door was opened to reveal no ball. A 2nd experiment indicated that children's preferential-looking performance did not differ from that in manual search tasks simply because additional response time had been allowed to respond. Previous comparisons of looking versus reaching tested children's postdiction response to an object in an unexpected location, but these findings indicate that toddlers can predict where the object should be.

Child Development↗
PubMed2005

Introduction to the special section on developing guidelines for the evidence-based assessment (EBA) of adult disorders.

The goal of this special section is to encourage greater awareness of evidence-based assessment (EBA) in the development of a scientifically supported clinical psychology. In this introductory article, the authors describe the elements that authors in this special section were asked to consider in their focused reviews (including the scope of available psychometric evidence, advancements in psychopathology research, and evidence of attention to factors such as gender, age, and ethnicity in measure validation). The authors then present central issues evident in the articles that deal with anxiety, depression, personality disorders, and couple distress and in the accompanying commentaries. The authors conclude by presenting key themes emerging from the articles in this special section, including gaps in psychometric information, limited information about the utility of assessment, the discrepancy between recommended EBAs and current training and practice, and the need for further data on the process of clinical assessment.

Adult↗