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Biomedical subjects

N S Gray

Publications and source records attributed to N S Gray.

At least 19 recordsLinked to original sources
PubMed2001

Synthesis and biological evaluation of myoseverin derivatives: microtubule assembly inhibitors.

Myoseverin, a trisubstituted purine, inhibits microtubule assembly in vitro, interferes with normal mitotic spindle assembly, and arrests the cell cycle in mitosis in U937 cells. We synthesized a variety of myoseverin derivatives and screened them for inhibition of spindle assembly in Xenopus egg extracts and for microtubule disassembly in vitro. Selected compounds were tested against 60 cancer cell lines at the National Cancer Institute as possible anticancer drug candidates.

Animals↗
PubMed2001

Solid-phase synthesis of 2,3,5-trisubstituted indoles.

2,3,5-Trisubstituted indoles are synthesized in three steps starting from resin-bound aniline 2. R1 is introduced by a palladium-mediated coupling of the aryl iodide with terminal alkynes followed by intramolecular cyclization to form the indole core. Acylation at C-3 with an acid chloride in the presence of AlCl(3) catalyst introduces R2. The indole C-5 position is then diversified either by Sonagashira or Suzuki couplings with the aryl bromide. Finally, indole N-1 can be modified by post-cleavage methylation. [reaction: see text]

Journal Article↗
PubMed2001

Design of allele-specific protein methyltransferase inhibitors.

Protein arginine methyltransferases, which catalyze the transfer of methyl groups from S-adenosylmethionine (SAM) to arginine side chains in target proteins, regulate transcription, RNA processing, and receptor-mediated signaling. To specifically address the functional role of the individual members of this family, we took a "bump-and-hole" approach and designed a series of N(6)-substituted S-adenosylhomocysteine (SAH) analogues that are targeted toward a yeast protein methyltransferase RMT1. A point mutation was identified (E117G) in Rmt1 that renders the enzyme susceptible to selective inhibition by the SAH analogues. A mass spectrometry based enzymatic assay revealed that two compounds, N(6)-benzyl- and N(6)-naphthylmethyl-SAH, can inhibit the mutant enzyme over the wild-type with the selectivity greater than 20. When the E117G mutation was introduced into the Saccharomyces cerevisiae chromosome, the methylation of Npl3p, a known in vivo Rmt1 substrate, could be moderately reduced by N(6)-naphthylmethyl-SAH in the resulting allele. In addition, an N(6)-benzyl-SAM analogue was found to serve as an orthogonal SAM cofactor. This analogue is preferentially utilized by the mutant methyltransferase relative to the wild-type enzyme with a selectivity greater than 67. This specific enzyme/inhibitor and enzyme/substrate design should be applicable to other members of this protein family and facilitate the characterization of protein methyltransferase function in vivo when combined with RNA expression analysis.

Alleles↗
PubMed2001

Combinatorial libraries and biological discovery.

Combinatorial chemistry has become a popular tool for the preparation of collections of compounds that can be used to find inhibitors and substrates for different protein targets. It has evolved to provide small molecule libraries, which, with the concomittant use of affinity chromatography, gene expression profiling and complementation, can be used to identify compounds and their protein targets in biological systems, including the neurological system.

Animals↗
PubMed2001

Context dependent latent inhibition in adult humans.

Learning the association between one stimulus (a condition stimulus, CS) and another (unconditioned stimulus, US) can be impaired by prior exposure to the CS alone--latent inhibition (LI). Current theories attempting to elucidate the cognitive deficit in schizophrenia have used the abolition of LI in schizophrenia as an indicator of attentional dysfunction. However, it has always been unclear if human and animal LI are measuring the same psychological processes. It is obviously important to clarify this relationship so that theoretical and experimental developments in the rat do not mislead the investigation of brain-behaviour relationships in schizophrenia. LI in the rat is strongly dependent upon context. Our aim was to examine the context specificity of LI in humans and specifically to: (1) investigate whether participants' belief that they are in a different context is sufficient to abolish LI, even though there is no physical change in the environment; (2) produce a context manipulation that is immune to alternative interpretation in terms of stimulus generalization decrement; and (3) investigate whether a "tonic" change of context reduces or abolishes human LI, thus complementing previous reports using a "phasic" change of context. In two experiments we manipulated context in either the real world or a virtual world, and showed that LI is abolished by a change of context in adult humans.

Adolescent↗
PubMed2000

A chemical switch for inhibitor-sensitive alleles of any protein kinase.

Protein kinases have proved to be largely resistant to the design of highly specific inhibitors, even with the aid of combinatorial chemistry. The lack of these reagents has complicated efforts to assign specific signalling roles to individual kinases. Here we describe a chemical genetic strategy for sensitizing protein kinases to cell-permeable molecules that do not inhibit wild-type kinases. From two inhibitor scaffolds, we have identified potent and selective inhibitors for sensitized kinases from five distinct subfamilies. Tyrosine and serine/threonine kinases are equally amenable to this approach. We have analysed a budding yeast strain carrying an inhibitor-sensitive form of the cyclin-dependent kinase Cdc28 (CDK1) in place of the wild-type protein. Specific inhibition of Cdc28 in vivo caused a pre-mitotic cell-cycle arrest that is distinct from the G1 arrest typically observed in temperature-sensitive cdc28 mutants. The mutation that confers inhibitor-sensitivity is easily identifiable from primary sequence alignments. Thus, this approach can be used to systematically generate conditional alleles of protein kinases, allowing for rapid functional characterization of members of this important gene family.

Alleles↗
PubMed2000

Behavioral treatment of PTSD in a perpetrator of manslaughter: a single case study.

Studies of posttraumatic stress disorder (PTSD) have predominantly focused on victims of trauma. Some studies have examined the after-effects of a person's own violent actions in combat or police situations. However, there is a sparsity of literature examining the development of PTSD in convicted perpetrators of violent crime, and there is no literature concerning the treatment of PTSD in such perpetrators. This single-case study presents the outcome of behavioral treatment in one case in which the patient had PTSD consequential to being a perpetrator of manslaughter. The theoretical implications of this case are briefly discussed.

Female↗
PubMed1999

Methylphenidate treatment for bulimia nervosa associated with a cluster B personality disorder.

OBJECTIVES: Psychotherapy and antidepressant medication are helpful to many patients with bulimia nervosa (BN). However, a substantial number of bulimics respond poorly to such treatments. Recent studies suggest that many of the poor responders have cluster B personality disorders. In some ways, the symptomatology of bulimics who have a comorbid cluster B disorder resembles that of patients with attention deficit hyperactivity disorder (ADHD). In particular, individuals in both groups frequently have a high level of impulsivity. Such a resemblance raised the question of whether administration of methylphenidate (MPH), a drug used to treat ADHD, would have therapeutic effects in this subgroup of BN patients. METHODS: In a pilot study, we administered MPH to 2 patients with BN and cluster B traits and found beneficial effects. These patients had not responded to adequate trials of psychotherapy and selective serotonin reuptake inhibitors (SSRIs). RESULTS: MPH treatment was effective. Both Patients had decreased binging and purging. DISCUSSION: MPH may be useful for bulimics with cluster B personality disorder who respond poorly to conventional treatment. Further studies of MPH administration may be worthwhile. Due to the potential risks, however, clinical treatment with this agent is not recommended at this time.

Adult↗
PubMed1999

Synthesis and application of functionally diverse 2,6,9-trisubstituted purine libraries as CDK inhibitors.

BACKGROUND: Purines constitute a structural class of protein ligands involved in mediating an astonishing array of metabolic processes and signal pathways in all living organisms. Synthesis of purine derivatives targeting specific purine-binding proteins in vivo could lead to versatile lead compounds for use as biological probes or drug candidates. RESULTS: We synthesized several libraries of 2,6, 9-trisubstituted purines using both solution- and solid-phase chemistry, and screened the compounds for inhibition of cyclin-dependent kinase (CDK) activity and human leukemic cell growth. Lead compounds were optimized by iterative synthesis based on structure-activity relationships (SARs), as well as analysis of several CDK-inhibitor cocrystal structures, to afford several interesting compounds including one of the most potent CDK inhibitors known to date. Unexpectedly, some compounds with similar CDK inhibitory activity arrested cellular proliferation at distinctly different phases of the cell cycle and another inhibitor directly induced apoptosis, bypassing cell-cycle arrest. Some of these compounds selectively inhibited growth of cells derived from specific tumors. CONCLUSIONS: 2,6,9-Trisubstituted purines have various and potent biological activities, despite high concentrations of competing endogenous purine ligands in living cells. Purine libraries constitute a versatile source of small molecules that affect distinct biochemical pathways mediating different cellular functions.

Adenine↗
PubMed1999

Elective combined electroconvulsive and clozapine therapy.

Clozapine therapy does not produce the rapid response that may be required in severely disturbed patients. The latter, not uncommonly, obstruct treatment by refusing to give blood for haematological monitoring or refusing to swallow tablets. Whereas electroconvulsive therapy (ECT) may be used for rapid behavioural control, the effects wane once the treatment course comes to an end. This paper reports an alternative strategy in such patients--combined jointly initiated therapy with clozapine and ECT. Six disturbed patients with treatment resistant schizophrenia were given a course of 12 ECT over 6 weeks. Blood was drawn for clozapine monitoring during the first anaesthetic, allowing the introduction of clozapine on day 6. There was a mean 32% improvement in Brief Psychiatric Rating Scale scores at week 6. This improvement persisted after the cessation of ECT, by which time all patients were compliant with blood testing and tablet taking. There were no adverse reactions apparent in the combination of the two therapies. Elective combined ECT and clozapine therapy may be useful in treatment-resistant schizophrenics where the clinical state necessitates a rapid therapeutic response and where blood tests are refused. A possible synergistic reaction between clozapine and ECT is worthy of further investigation.

Adult↗
PubMed1999

Effects of d-amphetamine and haloperidol on latent inhibition in healthy male volunteers.

Latent inhibition (LI) refers to a retardation of learning about the consequences of a stimulus when that stimulus has been passively presented a number of times without reinforcement. Acute positive-symptom schizophrenics, normal volunteers who score high on questionnaire measures of schizotypy and non-patients or animals treated with dopamine agonists show reduced LI. Neuroleptic drugs, such as haloperidol, administered at low doses, potentiate LI and effectively reverse disruption of LI induced by dopamine agonists in animals. However, a high dose of haloperidol, administered on its own, has been found to reduce LI. We examined the effects on LI of acute oral administration of an indirect dopamine-agonist, d-amphetamine (5 mg), and a nonselective dopamine receptor antagonist, haloperidol (5 mg), in normal male volunteers, using an associative learning task. Replicating previous reports, we found that d-amphetamine reduced LI; haloperidol also reduced LI, but only in subjects who scored low on the Psychoticism scale of the Eysenck Personality Questionnaire. In a subsequent study, no effect was found of 2 mg oral haloperidol administration on LI. The effect of 5 mg haloperidol on LI is interpreted as similar to that observed with a high dose of haloperidol in rats.

Adrenergic Agents↗
PubMed1998

Exploiting chemical libraries, structure, and genomics in the search for kinase inhibitors.

Selective protein kinase inhibitors were developed on the basis of the unexpected binding mode of 2,6,9-trisubstituted purines to the adenosine triphosphate-binding site of the human cyclin-dependent kinase 2 (CDK2). By iterating chemical library synthesis and biological screening, potent inhibitors of the human CDK2-cyclin A kinase complex and of Saccharomyces cerevisiae Cdc28p were identified. The structural basis for the binding affinity and selectivity was determined by analysis of a three-dimensional crystal structure of a CDK2-inhibitor complex. The cellular effects of these compounds were characterized in mammalian cells and yeast. In the latter case the effects were characterized on a genome-wide scale by monitoring changes in messenger RNA levels in treated cells with high-density oligonucleotide probe arrays. Purine libraries could provide useful tools for analyzing a variety of signaling and regulatory pathways and may lead to the development of new therapeutics.

Adenine↗
PubMed1997

CVT-313, a specific and potent inhibitor of CDK2 that prevents neointimal proliferation.

The activity of cyclin-dependent kinase 2 (CDK2) is essential for progression of cells from G1 to the S phase of the mammalian cell cycle. CVT-313 is a potent CDK2 inhibitor, which was identified from a purine analog library with an IC50 of 0.5 microM in vitro. Inhibition was competitive with respect to ATP (Ki = 95 nM), and selective CVT-313 had no effect on other, nonrelated ATP-dependent serine/threonine kinases. When added to CDK1 or CDK4, a 8.5- and 430-fold higher concentration of CVT-313 was required for half-maximal inhibition of the enzyme activity. In cells exposed to CVT-313, hyperphosphorylation of the retinoblastoma gene product was inhibited, and progression through the cell cycle was arrested at the G1/S boundary. The growth of mouse, rat, and human cells in culture was also inhibited by CVT-313 with the IC50 for growth arrest ranging from 1.25 to 20 microM. To evaluate the effects of CVT-313 in vivo, we tested this agent in a rat carotid artery model of restenosis. A brief intraluminal exposure of CVT-313 to a denuded rat carotid artery resulted in more than 80% inhibition of neointima formation. These observations suggest that CVT-313 is a promising candidate for evaluation in other disease models related to aberrant cell proliferation.

Animals↗
PubMed1997

Case study: an infection-triggered, autoimmune subtype of anorexia nervosa.

OBJECTIVE: Certain cases of anorexia nervosa (AN) may be similar to the recently described subtype of childhood-onset obsessive-compulsive disorder hypothesized to be one of the pediatric infection-triggered autoimmune neuropsychiatric disorders (PITANDs). METHOD: Three clinical cases are reported. The first patient is a 12-year-old boy whose AN worsened acutely after a group A beta-hemolytic streptococcal (GABHS) infection. His symptoms were alleviated after antibiotic treatment. Two other patients with possible PITANDs-related AN are described. RESULTS: An infection-triggered process may contribute to the pathogenesis of a subtype of AN. CONCLUSIONS: Future research is needed to explore the nature of PITANDs and their relationship with AN.

Adolescent↗
PubMed1997

Kamin blocking is not disrupted by amphetamine in human subjects.

The effect of oral amphetamine administration on the Kamin-blocking effect in healthy volunteer subjects was investigated. Against predictions, Kamin blocking was not disrupted by either a high or low oral dose of D-amphetamine under conditions which have, in previous studies, led to disruption of a related learning phenomenon (latent inhibition). This lack of effect of amphetamine administration upon Kamin blocking weakens hypotheses that this cognitive process is mediated by the same changes in dopaminergic activity which affect latent inhibition. Currently, the only data which show strong comparative associations between Kamin blocking and latent inhibition are when they are applied to schizophrenic populations. These results may suggest that Kamin blocking and latent inhibition may be measuring different aspects of schizophrenic cognitive dysfunction.

Adult↗
PubMed1996

The immunological evolution of catalysis.

The germline genes used by the mouse to generate the esterolytic antibody 48G7 were cloned and expressed in an effort to increase our understanding of the detailed molecular mechanisms by which the immune system evolves catalytic function. The nine replacement mutations that were fixed during affinity maturation increased affinity for the transition state analogue by a factor of 10(4), primarily the result of a decrease in the dissociation rate of the hapten-antibody complex. There was a corresponding increase in the rate of reaction of antibody with substrate, k(cat)/k(m), from 1.7 x 10(2)M(-1) min(-1) to 1.4 x 10(4)M(-1) min(-1). The three-dimensional crystal structure of the 48G7-transition state analogue complex at 2.0 angstroms resolution indicates that one of the nine residues in which somatic mutations have been fixed directly contact the hapten. Thus, in the case of 48G7, affinity maturation appears to play a conformational role, either in reorganizing the active site geometry of limiting side-chain and backbone flexibility of the germline antibody. The crystal structure and analysis of somatic and directed active site mutants underscore the role of transition state stabilization in the evolution of this catalytic antibody.

Amino Acid Sequence↗