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Stephen Martin

Publications and source records attributed to Stephen Martin.

27 records · Page 2Linked to original sources
PubMed2003

Time-resolved fluorescence anisotropy studies show domain-specific interactions of calmodulin with IQ target sequences of myosin V.

Single cysteine mutants of calmodulin, Cam(S38C) and Cam(N111C), have been specifically labelled with Alexa488 maleimide to study the effects of calcium on the structural dynamics of calmodulin complexed with IQ3, IQ4 and IQ34 target peptide motifs of mouse unconventional myosin-V. Using phase fluorometry, the time-resolved anisotropy shows well-separated global and segmental correlation times. The calcium-sensitive global motion of either calmodulin domain can be independently monitored in domain-specific interactions of either apo- or Ca(4).calmodulin with IQ3 or IQ4 peptides. C-domain interactions predominate, and apo-N-domain interactions are unexpectedly weak. The 1:1 complex of Ca(4).calmodulin with IQ34 behaves as a compact globular species. The results demonstrate novel dynamic aspects of calmodulin-IQ interactions relating to the calcium regulation of motility of unconventional myosin.

Amino Acid Sequence↗
PubMed2003

Mirtazapine orally disintegrating tablet versus sertraline: a prospective onset of action study.

This multinational, randomized, double-blind study was specifically designed to prospectively compare the onset of antidepressant efficacy of mirtazapine orally disintegrating tablets and sertraline at dosages commonly used in clinical practice. A total of 345 patients with major depressive episode (DSM-IV) received mirtazapine (30-45 mg/d) or sertraline (50-150 mg/d) for 8 weeks. Mirtazapine was administered in the newly developed fast dissolving, orally disintegrating tablet formulation. Assessments were performed at baseline and on days 4, 7, 10, 14, 28, 42, and 56. The primary efficacy variable (mean absolute change from baseline in the Hamilton Depression Rating Scale [HAMD] total score [17 items]) showed that mirtazapine was significantly (P < 0.05) more effective than sertraline at all assessments during the first 2 weeks of the study. After this time, HAMD total scores were similar in both groups. These findings were supported by analysis of the HAMD response rate (ie, > or =50% reduction in HAMD total score from baseline), HAMD remission rate (HAMD total score of < or =7), and the Montgomery-Asberg Depression Rating Scale (MADRS). Both treatments were well tolerated. In addition, mirtazapine had a greater effect than sertraline on sexual functioning. In conclusion, this first prospective onset of action study using the orally disintegrating tablet indicates that mirtazapine has a faster onset of therapeutic effect than sertraline. The orally disintegrating tablet formulation of mirtazapine used in this study is known to enhance the convenience and compliance by the patient.

Adolescent↗
PubMed2003

Treatment of schizophrenia with long-acting injectable risperidone: a 12-month open-label trial of the first long-acting second-generation antipsychotic.

BACKGROUND: The long-term safety and efficacy of long-acting injectable risperidone, the first long-acting second-generation antipsychotic, were evaluated in stable patients with schizophrenia. METHOD: After a 2-week run-in period during which patients with DSM-IV schizophrenia received flexible doses of 1 to 6 mg of oral risperidone, patients received injections of 25 mg, 50 mg, or 75 mg of long-acting risperidone every 2 weeks for 12 months. Severity of extrapyramidal symptoms was assessed with the Extrapyramidal Symptom Rating Scale (ESRS), and efficacy was assessed with the Positive and Negative Syndrome Scale (PANSS). This study was conducted from March 29, 1999 to July 19, 2000. RESULTS: The subjects were 615 patients with schizophrenia who received at least 1 injection of long-acting risperidone. The 12-month trial was completed by 65% of patients. Treatment was discontinued because of adverse events in 5% of patients. Extrapyramidal symptoms as adverse events were reported by 25% of the patients. Severity of extrapyramidal symptoms (according to ESRS scores) was low at baseline and decreased in each of the groups during the 12 months. The other most common adverse events were anxiety in 24%, insomnia in 21%, psychosis in 17%, and depression in 14% of the patients. Little pain was associated with the injections. Severity of symptoms of schizophrenia was improved in each group, with significant reductions in PANSS total scores (p <.01) and positive (p <.01) and negative (p <.001) factor scores. CONCLUSION: In terms of both safety and efficacy, symptomatically stable patients with schizophrenia benefit from being switched to long-acting injectable risperidone.

Administration, Oral↗
PubMed2002

Calmodulin-containing substructures of the centrosomal matrix released by microtubule perturbation.

Calmodulin redistribution in MDCK and HeLa cells subjected to microtubule perturbations by antimitotic drugs was followed using a calmodulin-EGFP fusion protein that preserves the Ca(2+) affinity, target binding and activation properties of native calmodulin. CaM-EGFP targeting to spindle structures in normal cell division and upon spindle microtubule disruption allows evaluation of the dynamic redistribution of calmodulin in cell division. Under progressive treatment of stably transfected mammalian cells with nocodazole or vinblastine, the centrosomal matrix at the mitotic poles subdivides into numerous small 'star-like' structures, with the calmodulin concentrated centrally, and partially distinct from the reduced microtubule mass to which kinetochores and chromosomes are attached. Prolonged vinblastine treatment causes the release of localised calmodulin into a uniform cytoplasmic distribution, and tubulin paracrystal formation. By contrast, paclitaxel treatment of metaphase cells apparently causes limited disassembly of the pericentriolar material into a number of multipolar 'ring-like' structures containing calmodulin, each one having multiple attached microtubules terminating in the partially disordered kinetochore/chromosome complex. Thus drugs with opposite effects in either destabilising or stabilising mitotic microtubules cause subdivision of the centrosomal matrix into two distinctive calmodulin-containing structures, namely small punctate 'stars' or larger polar 'rings' respectively. The 'star-like' structures may represent an integral subcomponent for the attachment of kinetochore microtubules to the metaphase centrosome complex. The results imply that microtubules have a role in stabilising the structure of the pericentriolar matrix, involving interaction, either direct or indirect, with one or more proteins that are targets for binding of calmodulin. Possible candidates include the pericentriolar matrix-associated coiled-coil proteins containing calmodulin-binding motifs, such as myosin V, kendrin (PCNT2) and AKAP450.

Animals↗
PubMed2002

Molecular interactions between desmosomal cadherins.

Desmocollins (Dscs) and desmogleins (Dsgs) are cell-adhesion molecules involved in the formation of desmosome cell-cell junctions and share structural similarities to classical cadherins such as E-cadherin. In order to identify and provide quantitative information on the types of protein-protein interactions displayed by the type 2 isoforms and investigate the role of Ca(2+) in this process, we have developed an Escherichia coli expression system to generate recombinant proteins containing the first two extracellular domains, namely Dsg2(1-2) and Dsc2(1-2). Analytical ultracentrifugation, chemical cross-linking, CD, fluorescence and BIAcore have been used to provide the first direct evidence of Ca(2+) binding to desmosomal cadherins. These studies suggest that Dsc2(1-2) not only exhibits homophilic interactions in solution, but can also form heterophilic interactions with Dsg2(1-2). The latter, on the other hand, shows much weaker homophilic association. Our results further demonstrate that heterophilic interactions are Ca(2+)-dependent, whereas the Ca(2+)-dependence of homophilic association is less clear. Our data indicate that the functional properties of Dsc2(1-2) are more similar to those of classical cadherins, consistent with the observation that Dsc shares a higher level of sequence homology with classical cadherins than does Dsg. In addition to corroborating the conclusions of previously reported transfection studies which suggest the formation of lateral heterodimers and homodimers, our results also provide direct quantitative information on the strength of these interactions which are essential for understanding the adhesion mechanism.

Binding Sites↗
PubMed2002

A double-blind, randomised comparative trial of amisulpride versus olanzapine in the treatment of schizophrenia: short-term results at two months.

OBJECTIVE: To compare the efficacy and safety of the atypical antipsychotics amisulpride and olanzapine in the treatment of acute psychotic exacerbations of schizophrenia. DESIGN AND SETTING: A multinational, double-blind randomised clinical trial. PATIENTS AND TREATMENT: Three hundred and seventy-seven patients with predominantly positive symptomatology were treated for six months with either amisulpride (200-800 mg/d) or olanzapine (5-20 mg/d). MAIN OUTCOME MEASURES: Short-term results were analysed after two months of treatment. The primary efficacy measure was the change of score on the Brief Psychiatric Rating Scale (BPRS). Other measures of efficacy and safety were also evaluated. RESULTS: Psychotic symptoms, as measured on the BPRS score, improved with both treatments, amisulpride being equivalent to olanzapine. All BPRS factor scores, as well as depressive symptoms, improved to a similar extent with both treatments. Less than five per cent of patients withdrew for adverse events, and there was no evidence for the emergence of extrapyramidal symptoms with either treatment. Statistically significant greater weight gain (2.7 +/- 3.9 kg) was observed during the study in the olanzapine group, compared with the amisulpride group (0.9 +/- 3.2 kg, p < 0.0001). CONCLUSIONS: Amisulpride and olanzapine show equivalent efficacy at 2 months in the treatment of acute psychotic exacerbations of schizophrenia. Amisulpride offers a significant advantage in preserving body weight.

Adolescent↗