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David Li

Publications and source records attributed to David Li.

14 recordsLinked to original sources
PubMed2006

Regulation of the monomer-dimer equilibrium in inducible nitric-oxide synthase by nitric oxide.

The oxygenase domain of inducible nitric-oxide synthase exists as a functional tight homodimer in the presence of the substrate L-arginine and the cofactor tetrahydrobiopterin (H4B). In the absence of H4B, the enzyme is a mixture of monomer and loose dimer. We show that exposure of H4B-free enzyme to NO induces dissociation of the loose dimer into monomers in a reaction that follows single exponential decay kinetics with a lifetime of approximately 300 min. It is followed by a faster autoreduction reaction of the heme iron with a lifetime of approximately 30 min and the concurrent breakage of the proximal iron-thiolate bond, forming a five-coordinate NO-bound ferrous species. Mass spectrometry revealed that the NO-induced monomerization is associated with intramolecular disulfide bond formation between Cys104 and Cys109, located in the zinc-binding motif. The regulatory effect of NO as a dimer inhibitor is discussed in the context of the structure/function relationships of this enzyme.

Amino Acid Motifs↗
PubMed2006

Three-tesla magnetic resonance imaging of the ventrolateral thalamus: a correlative anatomical description.

OBJECT: Surgery for tremor targets the ventrolateral nuclei of the thalamus. An initial radiological estimation of this target can be further refined through intraoperative physiological confirmation. Direct visualization of these nuclei has not yet been described. The improved signal-to-noise ratio associated with 3-tesla (3T) magnetic resonance (MR) imaging makes increased spatial resolution possible, which may aid in the identification of subtle morphological features. This study was conducted to describe the anatomy of the nuclei and fiber projections within the ventral thalamus by using 3T MR imaging. METHODS: Using a commercially available 3T MR unit, the authors obtained images of a formalin-fixed, paraffin-embedded brain. Slices with a 2-mm thickness and 0.2-mm gap were obtained parallel to the anterior commissure-posterior commissure (AC-PC) line. The brain was then sectioned through the cerebral hemispheres to obtain tissue slices encompassing the same levels. Adjacent 10-microm paraffin sections from the middle of each level were stained with Luxol fast blue and cresyl violet. The MR image and histological sections at the level of the AC-PC line were then compared in detail. In a separate study, the human thalamus was scanned in vivo using 3T and 1.5T MR imaging for anatomical comparison. CONCLUSIONS: The anatomy of the nuclei and fiber projections within the ventrolateral thalamus in humans can be described using 3T MR imaging. The findings were reproducible in vivo with 3T but not 1.5T MR imaging. Additional studies are needed to confirm the accuracy of this observation for clinical purposes.

Artifacts↗
PubMed2005

Benefits of high-dose, high-frequency interferon beta-1a in relapsing-remitting multiple sclerosis are sustained to 16 months: final comparative results of the EVIDENCE trial.

The EVIDENCE trial demonstrated that interferon (IFN) beta-1a, 44 mcg subcutaneously (sc) three times weekly (tiw) (Rebif), was significantly more effective than IFN beta-1a, 30 mcg intramuscularly (im) once weekly (qw) (Avonex), in reducing relapses and magnetic resonance imaging (MRI) activity in patients with relapsing-remitting multiple sclerosis at both 24 and 48 weeks of therapy. We now present final comparative data on these patients, showing that the superior efficacy of IFN beta-1a, 44mcg sc tiw, for relapse measures and MRI activity, compared with IFN beta-1a, 30mcg im qw, was sustained for at least 16 months. The development of antibodies to IFN was associated with reduced efficacy on MRI measures and fewer IFN-related adverse events, but did not have an impact on relapse outcomes.

Adjuvants, Immunologic↗
PubMed2005

Enhanced benefit of increasing interferon beta-1a dose and frequency in relapsing multiple sclerosis: the EVIDENCE Study.

BACKGROUND: The EVIDENCE (Evidence of Interferon Dose-Response: European North American Comparative Efficacy) Study demonstrated that patients with multiple sclerosis (MS) who initiate interferon beta-1a therapy with 44 microg 3 times weekly (TIW) were less likely to have a relapse or activity on magnetic resonance imaging (MRI) compared with those who initiate therapy at a dosage of 30 microg 1 time weekly (QW). OBJECTIVE: To determine the effect of changing the dosage from 30 microg QW to 44 microg TIW in this extension of the EVIDENCE Study. DESIGN/PATIENTS: Patients with relapsing MS originally randomized to interferon beta-1a, 30 microg QW, during the comparative phase of the study changed to 44 microg TIW, whereas patients originally randomized to 44 microg TIW continued that regimen. Patients were followed up, on average, for an additional 32 weeks. MAIN OUTCOME MEASURE: The within-patient pretransition to post-transition change in relapse rate. RESULTS: At the transition visit, 223 (73%) of 306 patients receiving 30 microg QW converted to 44 microg TIW, and 272 (91%) of 299 receiving 44-microg TIW continued the same therapy. The post-transition annualized relapse rate decreased from 0.64 to 0.32 for patients increasing the dose (P<.001) and from 0.46 to 0.34 for patients continuing 44-microg TIW (P = .03). The change was greater in those increasing dose and frequency (P = .047). Patients converting to the 44-mug TIW regimen had fewer active lesions on T2-weighted MRI compared with before the transition (P = .02), whereas those continuing the 44-microg TIW regimen had no significant change in T2 active lesions. Patients who converted to high-dose/high-frequency interferon beta-1a therapy had increased rates of adverse events and treatment terminations consistent with the initiation of high-dose subcutaneous interferon therapy. CONCLUSIONS: Patients receiving interferon beta-1a improved on clinical and MRI disease measures when they changed from 30 microg QW to 44 microg TIW.

Adjuvants, Immunologic↗
PubMed2005

Ligand-protein interactions in nitric oxide synthase.

Nitric oxide synthases (NOSs) are heme proteins that catalyze the formation of nitric oxide (NO) from L-arginine and oxygen in a sequential two-step process. Three structurally similar isoforms have been identified that deliver NO to different tissues for specific functions. An understanding of the interactions of ligands with the protein is essential to determine the mechanism of catalysis, the design of inhibitors and the differential auto-inhibitory regulation of the enzymatic activity of the isoforms due to the binding of NO to the heme. Ligand-protein interactions in the three isoforms revealed by resonance Raman scattering studies are reviewed in this article. The CO-related modes in the CO-bound ferrous enzyme are sensitive to the presence of substrate, either L-arginine or N-hydroxy-L-arginine, in the distal pocket, but insensitive to the presence of the tetrahydrobiopterin (H4B) cofactor. In contrast, when NO is coordinated to the ferric heme, the NO is sensitive to the substrate only when H4B is present. Furthermore, in the NO-bound ferric enzyme, the addition of H4B induces a large heme distortion that may modulate heme reduction and thereby regulate the NO auto-inhibitory process. In the metastable O2-bound enzyme, L-arginine binding causes the appearance of a shoulder on the O-O stretching mode, suggesting a specific interaction of the heme-bound dioxygen with the bound-substrate that may be crucial for the oxygenation reaction of the substrate during the catalytic turn-over. It is postulated that spectroscopic differences in the oxy-complex are a consequence of the degree of protonation of the proximal cysteine ligand on the heme. Resonance Raman studies of NOSs expand our understanding of the mechanistic features of this important family of enzymes.

Carbon Monoxide↗
PubMed2005

Vital pulp therapy with mineral trioxide aggregate.

The present case report describes the treatment of complicated crown fractures using mineral trioxide aggregate (MTA). MTA was used as pulp-capping material after partial pulpotomy to preserve the vitality of the pulpal tissues in two cases. Follow-up examinations revealed that the treatment was successful in preserving pulpal vitality and continued development of the tooth.

Aluminum Compounds↗
PubMed2005

Neurological soft signs as predictors of treatment response to selective serotonin reuptake inhibitors in obsessive-compulsive disorder.

Neurological soft-sign abnormalities have been implicated in obsessive-compulsive disorder (OCD). This first comprehensive data analysis evaluated the association between baseline neurological soft signs and treatment response in 117 OCD patients treated with controlled-release fluvoxamine in a double-blind placebo-controlled trial. Total and right-sided soft signs for the responders and the nonresponders did not differ significantly. Left-sided visuospatial soft signs were significantly increased in treatment nonresponders compared to responders. These subtle neurological abnormalities may implicate a potential subgroup of OCD patients with poorer treatment response. This may have treatment implications and therefore serve as a screening tool in OCD.

Double-Blind Method↗
PubMed2004

Heme distortion modulated by ligand-protein interactions in inducible nitric-oxide synthase.

The catalytic center of nitric-oxide synthase (NOS) consists of a thiolate-coordinated heme macrocycle, a tetrahydrobiopterin (H4B) cofactor, and an l-arginine (l-Arg)/N-hydroxyarginine substrate binding site. To determine how the interplay between the cofactor, the substrates, and the protein matrix housing the heme regulates the enzymatic activity of NOS, the CO-, NO-, and CN(-)-bound adducts of the oxygenase domain of the inducible isoform of NOS (iNOS(oxy)) were examined with resonance Raman spectroscopy. The Raman data of the CO-bound ferrous protein demonstrated that the presence of l-Arg causes the Fe-C-O moiety to adopt a bent structure because of an H-bonding interaction whereas H4B binding exerts no effect. Similar behavior was found in the CN(-)-bound ferric protein and in the nitric oxide (NO)-bound ferrous protein. In contrast, in the NO-bound ferric complexes, the addition of l-Arg alone does not affect the structural properties of the Fe-N-O moiety, but H4B binding forces it to adopt a bent structure, which is further enhanced by the subsequent addition of l-Arg. The differential interactions between the various heme ligands and the protein matrix in response to l-Arg and/or H4B binding is coupled to heme distortions, as reflected by the development of a variety of out-of-plane heme modes in the low frequency Raman spectra. The extent and symmetry of heme deformation modulated by ligand, substrate, and cofactor binding may provide important control over the catalytic and autoinhibitory properties of the enzyme.

Binding Sites↗
PubMed2004

A double-blind placebo-controlled study of controlled release fluvoxamine for the treatment of generalized social anxiety disorder.

This was a randomized double-blind placebo-controlled multicenter study to assess the efficacy, safety, and tolerability of fluvoxamine in a controlled release (CR) formulation for treatment of generalized social anxiety disorder (GSAD). A total of 300 subjects with GSAD were randomly assigned to receive either fluvoxamine CR (N = 149) or placebo (N = 151) for 12 weeks. Mean changes from baseline to end point in Liebowitz Social Anxiety Scale (LSAS), Clinical Global Impression Severity of Illness Scale (CGI-S), Sheehan Disability Scale (SDS), as well as the mean end point scores in Clinical Global Impression Improvement Scale (CGI-I) and Patient Global Impression of Improvement Scale (PGI) were compared between the fluvoxamine CR and placebo treatment groups. Arizona Sexual Experience Scale (ASEX), adverse event, and other safety parameters were also assessed. The results demonstrated that fluvoxamine CR was significantly superior to placebo in decreasing LSAS total score (primary measure) starting at week 4. At end point, there was a mean change from baseline of -36.1 +/- 2.7 (37% reduction) in the LSAS total score in the fluvoxamine CR group compared with -27.3 +/- 2.4 (28% reduction) in the placebo group (P = 0.020 for mean change). Fluvoxamine CR was also significantly superior to placebo in SDS, CGI-S, CGI-I at end point (secondary measures). When compared with placebo, fluvoxamine CR did not cause any significant weight gain or clinically significant sexual dysfunction as measured by ASEX. In summary, fluvoxamine CR is an efficacious, safe, and well-tolerated treatment of generalized social anxiety disorder.

Adolescent↗
PubMed2004

Fluvoxamine-controlled release formulation for the treatment of generalized social anxiety disorder.

BACKGROUND: Generalized social anxiety disorder is a highly prevalent anxiety disorder with deleterious effects on social and family relationships, as well as work performance. We report the results of a multicenter, randomized, placebo-controlled trial comparing the efficacy, safety, and tolerability of fluvoxamine controlled release (CR) to placebo in patients with generalized social anxiety disorder. METHODS: A total of 279 adult patients meeting all inclusion/exclusion criteria was recruited at 23 United States sites and randomly assigned to receive either fluvoxamine CR (100-300 mg/d) or placebo for 12 weeks. The dose could be increased, based on efficacy and tolerability, in increments of 50 mg/d at weekly intervals. The dosage remained constant during weeks 6 to 12. RESULTS: Treatment with fluvoxamine CR resulted in statistically and clinically significant improvements in symptoms associated with generalized social anxiety disorder as early as week 4 on the Liebowitz Social Anxiety Scale and the Clinical Global Impression Scale Global Improvement, and at week 6 on the Sheehan Disability Scale, Clinical Global Impression Scale Severity of Illness and the Patient Global Impression of Improvement Scale. The most frequent adverse events reported by patients on fluvoxamine CR were headache, nausea, somnolence, and insomnia. No weight gain was observed for either treatment group, and at end point, there were no differences between treatments on overall sexual function, as measured by the Arizona Sexual Experience Scale. CONCLUSIONS: Both physician and patient-rated scales indicate that fluvoxamine CR is effective and safe for the treatment of generalized social anxiety disorder.

Adolescent↗
PubMed2003

Fluvoxamine CR in the long-term treatment of social anxiety disorder: the 12- to 24-week extension phase of a multicentre, randomized, placebo-controlled trial.

Fluvoxamine CR has been reported effective in the short-term (12-wk) treatment of generalized social anxiety disorder (social phobia). Social anxiety disorder (SAD) is, however, a chronic disorder thought to require maintenance treatment. We report on data from the extension phase of a short-term study, in order to explore the efficacy and safety profile of fluvoxamine CR (100-300 mg/d) in the longer-term treatment of this disorder. Adult outpatients with generalized social anxiety disorder (GSAD) at 35 centres in Europe, South Africa, and USA were included in an acute phase study (12 wk). Subjects who demonstrated at least minimal improvement by endpoint (n=112), were offered participation in an extension phase, in which medication was continued for a further 12 wk under double-blind conditions. Efficacy was assessed using the Liebowitz Social Anxiety Disorder Scale (LSAS), the Clinical Global Impression Global Improvement score (CGI-I), the Clinical Global Impressions Severity of Illness score (CGI-S), and the Sheehan Disability Scale (SDS). Safety and tolerability assessments were also performed at regular intervals. Subjects treated with fluvoxamine CR had a numerically greater decrease in LSAS total scores than subjects treated with placebo at endpoint. Analysis of data from baseline (day 1) to endpoint (last observation carried forward) demonstrated that this difference tended towards significance, while severity of illness on the CGI-S and disability on the SDS were significantly lower in the fluvoxamine CR group than in the placebo group. The same trends were observed when only data from weeks 12-24 were included in the analysis; although the magnitude of changes was smaller in the extension phase than in the acute phase, fluvoxamine CR-treated subjects continued to show improvement compared to placebo-treated subjects. Most treatment-emergent signs and symptoms (TESS) were mild to moderate in severity. No unexpected abnormalities were reported on vital signs, electrocardiagrams, or laboratory investigations. These data support the long-term efficacy, safety, and tolerability of fluvoxamine CR in the treatment of GSAD. Given the prevalence, persistence, and disability associated with GSAD, and the relative paucity of long-term treatment studies of SAD, the current dataset provides empirical support for the current clinical consensus that pharmacotherapy of this disorder should be continued beyond the acute phase.

Adult↗
PubMed2003

A double-blind, placebo-controlled study of the efficacy and safety of controlled-release fluvoxamine in patients with obsessive-compulsive disorder.

OBJECTIVE: The aim of this 12-week, double-blind, flexible-dose, placebo-controlled, parallel-arm, multicenter trial was to determine the safety and efficacy of fluvoxamine in a controlled-release (CR) formulation in adult outpatients with obsessive-compulsive disorder (OCD). METHOD: 253 adult outpatients with DSM-IV OCD were randomly assigned to receive 100 to 300 mg of fluvoxamine CR (N = 127) or placebo (N = 126) once daily for 12 weeks. Intent-to-treat analyses of efficacy assessments with the Yale-Brown Obsessive Compulsive Scale (YBOCS), Clinical Global Impressions-Severity of Illness scale (CGI-S), and Clinical Global Impressions-Improvement scale (CGI-I) were conducted. RESULTS: Fluvoxamine CR was significantly (p <.05) superior to placebo in decreasing YBOCS total score beginning at week 2. This early response was sustained at all subsequent visits. At endpoint, there was a mean decrease of 8.5 +/- 0.7 (31.7%) in the YBOCS total score compared with baseline in the fluvoxamine CR treatment group versus a mean decrease of 5.6 +/- 0.7 (21.2%) in the placebo group (p =.001). Fluvoxamine CR was also significantly superior to placebo in lowering the severity of illness (CGI-S, p =.002) and in producing clinical improvement (CGI-I, p <.01). At endpoint, significantly greater percentages of the fluvoxamine CR treatment group were responders (p =.002) and remitters (p =.019) compared with the placebo group. CONCLUSION: Over 12 weeks, fluvoxamine CR treatment was associated with a statistically significant and clinically relevant reduction in OCD severity and was found to be safe and well tolerated. The early onset of therapeutic effect, starting from week 2, was of particular interest.

Adolescent↗