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Biomedical subjects

A B Smith

Publications and source records attributed to A B Smith.

At least 37 records · Page 2Linked to original sources
PubMed2001

Design and synthesis of novel scaffolds for drug discovery: hybrids of beta-D-glucose with 1,2,3,4-tetrahydrobenzo[e][1,4]diazepin-5-one, the corresponding 1-oxazepine, and 2- and 4-pyridyldiazepines.

[structure: see text]. We describe the syntheses of novel tricyclic scaffolds that incorporate a fusion of a substituted pyranose ring with the seven-membered rings of 1,2,3,4-tetrahydrobenzo[e][1,4]diazepin-5-one and the corresponding oxazepine and pyridyldiazepine to generate the benzodiazepines, and the related heterocycles. In each instance, the pyranose rings contain three protected hydroxyls, suitable for selective derivatization.

Benzodiazepines↗
PubMed2001

Self-reported quality of life of individual cancer patients: concordance of results with disease course and medical records.

PURPOSE: To investigate the applicability of a standard quality of life (QL) questionnaire to individual cancer patients and to explore the potential for impact of QL information on the process of care by comparing at group level the QL results with the medical records. PATIENTS AND METHODS: One hundred fourteen consecutive patients at the oncology clinics at St James's Hospital, Leeds, United Kingdom, completed the European Organization for the Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire (QLQ)-C30 on a touch-screen computer over a 6-month period. The QL results were compared with the corresponding medical records at individual and group level. RESULTS: For individual patients, the serial measurement of QL allowed recognition of patterns over time corresponding to disease course. At group level, a higher proportion of patients reported problems on EORTC QLQ-C30 than were mentioned in the medical records (McNemar paired test, P <.01). Most often clinicians mentioned pain (22% to 39%), and at the initial visit role (66%), and social issues (77%). For the rest of the symptoms and functions, the problems were recorded in between 1% and 25% of the notes, but 20% to 76% of the patients reported QL impairment. Problems that were not recorded in the medical notes tended to be of low severity, with a significant trend observed for pain, fatigue, nausea/vomiting, dyspnea, loss of appetite, and physical function scale (chi(2) test, 11.55 to 34.42, df = 1, P <.001). CONCLUSION: The QL data on individual patients was consistent with the clinical records, thus providing evidence for the validity of these measures in assessment of the individual. The QL profiles had more information on symptoms and particularly on functional issues, such as emotional distress and physical performance.

Disease Progression↗
PubMed2001

Large-scale heterogeneity of the fossil record: implications for Phanerozoic biodiversity studies.

Patterns of origination, extinction and standing diversity through time have been inferred from tallies of taxa preserved in the fossil record. This approach assumes that sampling of the fossil record is effectively uniform over time. Although recent evidence suggests that our sampling of the available rock record has indeed been very thorough and effective, there is also overwhelming evidence that the rock record available for sampling is itself distorted by major systematic biases. Data on rock outcrop area compiled for post-Palaeozoic sediments from Western Europe at stage level are presented. These show a strongly cyclical pattern corresponding to first- and second-order sequence stratigraphical depositional cycles. Standing diversity increases over time and, at the coarsest scale, is decoupled from surface outcrop area. This increasing trend can therefore be considered a real pattern. Changes in standing diversity and origination rates over time-scales measured in tens of millions of years, however, are strongly correlated with surface outcrop area. Extinction peaks conform to a random-walk model, but larger peaks occur at just two positions with respect to second-order stratigraphical sequences, towards the culmination of stacked transgressive system tracts and close to system bases, precisely the positions where taxonomic last occurrences are predicted to cluster under a random distribution model. Many of the taxonomic patterns that have been described from the fossil record conform to a species-area effect. Whether this arises primarily from sampling bias, or from changing surface area of marine shelf seas through time and its effect on biodiversity, remains problematic.

Animals↗
PubMed2001

Design and synthesis of novel 2,3-dihydro-1H-isoindoles with high affinity and selectivity for the dopamine D3 receptor.

Starting from the tetrahydroisoquinoline SB-277011 1, a novel series of 5-substituted-2,3-dihydro-1H-isoindoles has been designed. Subsequent optimisation resulted in identification of 19, which has high affinity for the dopamine D3 receptor (pKi 8.3) and > or = 100-fold selectivity over other aminergic receptors. In rat studies 19 was brain penetrant with an excellent pharmacokinetic profile (oral bioavailability 77%, t1/2 5.2h).

Animals↗
PubMed2001

Solution structure of (+)-discodermolide.

[structure: see text]. The solution structure of (+)-discodermolide (1) has been determined via 1- and 2-D NMR techniques in conjunction with Monte Carlo conformational analysis. Taken together, the results demonstrate that in solution (+)-discodermolide occupies a helical conformation remarkably similar to the solid state conformation.

Alkanes↗
PubMed2001

Pre- and postsynaptic actions of ATP on neurotransmission in rat submandibular ganglia.

The pre- and postsynaptic actions of exogenously applied ATP were investigated in intact and dissociated parasympathetic neurones of rat submandibular ganglia. Nerve-evoked excitatory postsynaptic potentials (EPSPs) were not inhibited by the purinergic receptor antagonists, suramin and pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS), or the desensitising agonist, alpha,beta-methylene ATP. In contrast, EPSPs were abolished by the nicotinic acetylcholine receptor antagonists, hexamethonium and mecamylamine. Focal application of ATP (100 microM) had no effect on membrane potential of the postsynaptic neurone or on the amplitude of spontaneous EPSPs. Taken together, these results suggest the absence of functional purinergic (P2) receptors on the postganglionic neurone in situ. In contrast, focally applied ATP (100 microM) reversibly inhibited nerve-evoked EPSPs. Similarly, bath application of the non-hydrolysable analogue of ATP, ATP gamma S, reversibly depressed EPSPs amplitude. The inhibitory effects of ATP and ATP gamma S on nerve-evoked transmitter release were antagonised by bath application of either PPADS or suramin, suggesting ATP activates a presynaptic P2 purinoceptor to inhibit acetylcholine release from preganglionic nerves in the submandibular ganglia. In acutely dissociated postganglionic neurones from rat submandibular ganglia, focal application of ATP (100 microM) evoked an inward current and subsequent excitatory response and action potential firing, which was reversibly inhibited by PPADS (10 microM). The expression of P2X purinoceptors in wholemount and dissociated submandibular ganglion neurones was examined using polyclonal antibodies raised against the extracellular domain of six P2X purinoceptor subtypes (P2X(1-6)). In intact wholemount preparations, only the P2X(5) purinoceptor subtype was found to be expressed in the submandibular ganglion neurones and no P2X immunoreactivity was detected in the nerve fibres innervating the ganglion. Surprisingly, in dissociated submandibular ganglion neurones, high levels of P2X(2) and P2X(4) purinoceptors immunoreactivity were found on the cell surface. This increase in expression of P2X(2) and P2X(4) purinoceptors in dissociated submandibular neurones could explain the increased responsiveness of the neurones to exogenous ATP. We conclude that disruption of ganglionic transmission in vivo by either nerve damage or synaptic blockade may up-regulate P2X expression or availability and alter neuronal excitability.

Acetylcholine↗
PubMed2001

The relationship between Taxol and (+)-discodermolide: synthetic analogs and modeling studies.

BACKGROUND: During the past decade, Taxol has assumed an important role in cancer chemotherapy. The search for novel compounds with a mechanism of action similar to that of Taxol, but with greater efficacy particularly in Taxol-resistant cells, has led to the isolation of new natural products. One such compound, (+)-discodermolide, although structurally distinct from Taxol, has a similar ability to stabilize microtubules. In addition, (+)-discodermolide is active in Taxol-resistant cell lines that overexpress P-glycoprotein, the multidrug-resistant transporter. Interestingly, (+)-discodermolide demonstrates a profound enhancement of the initiation process of microtubule polymerization compared to Taxol. RESULTS: The synthesis of (+)-discodermolide analogs exploiting our highly efficient, triply convergent approach has permitted structure-activity relationship (SAR) studies. Small changes to the (+)-discodermolide structure resulted in a dramatic decrease in the ability of all four discodermolide analogs to initiate tubulin polymerization. Two of the analogs also demonstrated a decrease in total tubulin polymerization, while a change in the olefin geometry at the C8 position produced a significant decrease in cytotoxic activity. CONCLUSIONS: The availability of (+)-discodermolide and the analogs, and the resultant SAR analysis, have permitted an exploration of the similarities and differences between (+)-discodermolide and Taxol. Docking of the X-ray/solution structure of (+)-discodermolide into the Taxol binding site of beta-tubulin revealed two possible binding modes (models I and II). The preferred pharmacophore model (I), in which the C19 side chain of (+)-discodermolide matches with the C2 benzoyl group of Taxol and the delta-lactone ring of (+)-discodermolide overlays with the C13 side chain of Taxol, concurred with the results of the SAR analysis.

Alkanes↗
PubMed2001

Neuropsychological analyses of impulsiveness in childhood hyperactivity.

BACKGROUND: Neuropsychological analyses of impulsiveness are needed to refine assessment of attention-deficit hyperactivity disorder (ADHD). AIMS: To investigate specific impairments in hyperactive children in a neuropsychological task battery of impulsiveness, the Maudsley Attention and Response Suppression (MARS) task battery, and to identify the neural substrates. METHOD: Impulsiveness was assessed using different tasks of inhibitory control and time management (MARS) in 55 children with ADHD, other diagnoses and controls. Functional magnetic resonance images were obtained from adolescents with and without ADHD during three of the tasks. RESULTS: Children with ADHD, but not psychiatric controls, were impaired on tests of response inhibition, but not of motor timing. Reduced right prefrontal activation was observed in hyperactive adolescents during higher level inhibition and delay management, but not during simple sensorimotor coordination. CONCLUSIONS: Attention-deficit hyperactivity disorder is characterised by specific deficits in tasks of motor response inhibition, but not motor timing, and by dysfunction of frontostriatal brain regions.

Adolescent↗
PubMed2000

Development of an efficient, regio- and stereoselective route to libraries based on the beta-D-glucose scaffold.

The design and execution of an efficient synthetic route for the sequential functionalization of the five hydroxyl substituents of beta-D-glucose has been achieved. This strategy, based on the stereoselective glycosidation of thioglycosides, provides a new approach for the parallel construction of a wide variety of beta-D-glucose analogues and as such holds promise for solid-support library syntheses.

Carbamates↗
PubMed2000

Intramolecular hydrogen-bond participation in phosphonylammonium salt formation.

[reaction: see text] A series of phosphonochloridates and phosphonyl dichlorides were prepared, and their reactivity with triethylamine has been investigated using (31)P NMR spectroscopy. Taken together these studies provide evidence that an intramolecular hydrogen-bond is required for phosphonylammonium salt formation to render the phosphorus more electron-deficient.

Ethylamines↗
PubMed2000

No evidence for a parent-of-origin effect detected in the pattern of inheritance of schizophrenia.

BACKGROUND: Schizophrenia is a complex genetic disorder with no clear pattern of inheritance. Epigenetic modification of genes may thus play a role in its transmission. METHODS: In our study, 439 families with at least two ill siblings with schizophrenia (208 with unilineal transmission) were examined for evidence of a parent-of-origin effect (e.g., evidence of parental imprinting on the familial transmission of schizophrenia). RESULTS: No significant difference in the prevalence of maternal compared with paternal transmission was found. In addition, affected male subjects did not differ from affected female subjects in the proportion of their offspring diagnosed with schizophrenia. CONCLUSIONS: Although the transmission of schizophrenia may be influenced by epigenetic events, our study fails to find evidence that one epigenetic mechanism, a parent-of-origin imprinting effect, determines whether an individual expresses the illness.

Adult↗
PubMed2000

A second-generation synthesis of polypyrrolinone nonpeptidomimetics: prelude to the synthesis of polypyrrolinones on solid support.

[reaction: see text] A second-generation asymmetric synthesis of polypyrrolinones (3) has been achieved exploiting scalemic alpha-aminolactones (1) as building blocks. Imine formation between an appropriate lactone (1) and aldehyde (2), followed in turn by pyrrolinone ring construction promoted by KHMDS in the presence of 18-crown-6 and modified Swern oxidation furnished pyrrolinone aldehyde 3. This iterative, efficient three-step protocol paves the way for the synthesis of polypyrrolinones on solid support.

Aspartic Acid Endopeptidases↗
PubMed2000

Synthesis of polypyrrolinones on solid support.

[reaction: see text] An efficient, three-step iterative synthesis of polypyrrolinones has been achieved on solid support, setting the stage for the construction of a wide variety of libraries based on the pyrrolinone scaffold. Central to the approach is an effective end-game sequence featuring pyrrolinone ring construction with traceless release from the solid support.

Aldehydes↗
PubMed2000

Total synthesis of the ansamycin antibiotic (+)-thiazinotrienomycin E.

The first total synthesis of (+)-thiazinotrienomycin E (1), member of a novel class of cytotoxic ansamycin antibiotics, has been achieved. Key features of the synthetic strategy include (a) the efficient construction of sulfone 7 incorporating TBS protection of the aniline, (b) an improved synthesis of allyl chloride (-)-6, the advanced intermediate employed in our trienomycins A and F total syntheses, (c) application of the Kocienski modified Julia protocol to elaborate the E,E,E-triene subunit in a stereo-controlled fashion, (d) an efficient union of sulfone 7 with advanced iodide 62, and (e) Mukaiyama macrolactamization to access the thiazinotrienomycin macrocyclic ring.

Anti-Bacterial Agents↗