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Biomedical subjects

David A Jackson

Publications and source records attributed to David A Jackson.

15 recordsLinked to original sources
PubMed2006

The disposition and metabolism of naveglitazar, a peroxisome proliferator-activated receptor alpha-gamma dual, gamma-dominant agonist in mice, rats, and monkeys.

Naveglitazar [LY519818; benzenepropanoic acid, alpha-methoxy-4-[3-(4-phenoxyphenoxy)propoxy], (alpha-S)-] is a nonthiozolidinedione peroxisome proliferator-activated receptor alpha-gamma dual, gamma-dominant agonist that has shown glucose-lowering potential in animal models and in the clinic. Studies have been conducted to characterize the disposition, metabolism, and excretion of naveglitazar in mice, rats, and monkeys after oral and/or i.v. bolus administration. After oral administration of [(14)C]naveglitazar, naveglitazar was well absorbed and moderately metabolized in all species evaluated, with total recoveries of radioactivity ranging from 90 to 96%. Naveglitazar was the most abundant peak observed in circulation at C(max), representing 68 to 81% of the total radioactivity in plasma. The most prominent metabolite observed in circulation was the R-enantiomer of naveglitazar, LY591026, which is formed via enzymatic chiral inversion. para-Hydroxy naveglitazar and the sulfate conjugate of para-hydroxy naveglitazar were also observed in circulation in most species, especially in the monkey. The metabolic pathways observed include enzymatic chiral inversion, aromatic hydroxylation, oxidative dehydrogenation, and/or various phase II conjugation pathways. Naveglitazar was highly bound to plasma proteins among the species examined (>99%), and binding was independent of concentration. Biliary excretion was recognized as the most prominent excretion pathway in bile duct-cannulated rats (79 of the 96% recovered), producing an acyl glucuronide conjugate of naveglitazar and a sulfate and glucuronide diconjugate of para-hydroxy naveglitazar, which were shown to be reversible. The primary excretory pathway observed in mice and monkeys was via the feces. In summary, naveglitazar was well absorbed, moderately metabolized, and excreted via the feces in mice, rats, and monkeys.

Animals↗
PubMed2006

Application of biocatalysis to drug metabolism: preparation of mammalian metabolites of a biaryl-bis-sulfonamide AMPA (alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid) receptor potentiator using Actinoplanes missouriensis.

LY451395 (2-propanesulfonamide, N-[(2R)-2-[4'-[2-[methylsulfonyl)amino]ethyl][1,1'-biphenyl]-4-yl]propyl]-) is a potent and highly selective potentiator of the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors. It is a biaryl-bis-sulfonamide and is known to be highly metabolized in preclinical species. In those metabolism studies, the metabolite structures were proposed exclusively by the analysis of mass spectrometric data. Although mass spectrometry is clearly a technique of choice for rapid identification of drug metabolites, occasionally, nuclear magnetic resonance spectroscopy is required to unambiguously assign and characterize, particularly, the regio- and stereochemistry of metabolic changes. Nuclear magnetic resonance spectroscopy, in general, is less sensitive than other detection methods and demands several micrograms of material for the analysis. To support full structure characterization of metabolites by NMR, in this study we demonstrated the application of a microbial-based surrogate biocatalytic system to produce sufficient amounts of the mammalian metabolites of LY451395. The results revealed that incubation of LY451395 with Actinoplanes missouriensis NRRL B3342 generated several metabolites that were previously detected in the in vivo metabolism studies of the preclinical species. Subsequent large-scale bioconversion resulted in the isolation of seven mammalian metabolites in milligram quantities for structural characterization by nuclear magnetic resonance spectroscopy. Furthermore, a selected group of metabolites generated from the microbial conversion served as analytical standards to monitor and quantify drug metabolites during clinical investigations.

Biotechnology↗
PubMed2006

Randomized trial of a brief physiotherapy intervention compared with usual physiotherapy for neck pain patients: cost-effectiveness analysis.

OBJECTIVES: To assess the cost-effectiveness of brief physiotherapy intervention versus usual physiotherapy management in patients with neck pain of musculoskeletal origin in the community setting. METHODS: A cost-effectiveness analysis was conducted alongside a multicenter pragmatic randomized controlled clinical trial. Individuals 18 years of age and older with neck pain of more than 2 weeks were recruited from physiotherapy departments with referrals from general practitioners (GPs) in the East Yorkshire and North Lincolnshire regions in the United Kingdom. A total of 139 patients were allocated to the brief intervention, and 129 to the usual physiotherapy. Resource use data were prospectively collected on the number of physiotherapy sessions, hospital stay, specialist, and GP visits. Quality-adjusted life years (QALYs) were estimated using EQ-5D data collected at baseline, 3 and 12 months from the start of the treatment. The economic evaluation was conducted from the U.K. National Health System perspective. RESULTS: On average, brief intervention produced lower costs (pounds--68; 95 percent confidence interval [CI], pounds--103 to pounds--35) and marginally lower QALYs (-0.001; 95 percent CI, -0.030 to 0.028) compared with usual physiotherapy, resulting in an incremental cost per QALY of pounds 68,000 for usual physiotherapy. These results are sensitive to patients' treatment preferences. CONCLUSIONS: Usual physiotherapy may not be good value for money for the average individual in this trial but could be a cost-effective strategy for those who are indifferent toward which treatment they receive.

Cost-Benefit Analysis↗
PubMed2005

A randomized trial comparing a group exercise programme for back pain patients with individual physiotherapy in a severely deprived area.

PURPOSE: To compare a group exercise programme known as the Back to Fitness programme with individual physiotherapy for patients with non-specific low back pain from a materially deprived area. METHOD: This was a randomized controlled trial including 237 physiotherapy patients with back pain lasting more than six weeks. Participants were allocated to either the Back to Fitness programme or to individual physiotherapy, and followed up at three months and 12 months after randomization. The main outcome measure was the Roland Disability Questionnaire. Secondary measures were: SF12, EQ5D, Pain Self-Efficacy Scale. Health care diaries recording patients' use of health care resources were also collected over a 12-month period. RESULTS: There were no statistically significant differences in change scores between groups on the primary outcome measure at three months (CI - 2.24 to 0.49) and at 12 months (CI - 1.68 to 1.39). Only minor improvements in disability scores were observed in the Back to Fitness group at three months and 12 months respectively (mean change scores; - 0.89, - 0.77) and in the individual physiotherapy arm (mean change scores; - 0.02, - 0.63). Further analysis showed that patients from the most severely deprived areas were marginally worse at three month follow-up whereas those from more affluent areas tended to improve (CI 0.43 to 3.15).

Adult↗
PubMed2004

Randomised trial of a brief physiotherapy intervention compared with usual physiotherapy for neck pain patients: outcomes and patients' preference.

OBJECTIVES: Firstly, to compare the effectiveness of a brief physiotherapy intervention with "usual" physiotherapy for patients with neck pain. Secondly, to evaluate the effect of patients' preferences on outcome. DESIGN: Non-inferiority randomised controlled trial eliciting preferences independently of randomisation. SETTING: Physiotherapy departments in a community setting in Yorkshire and north Lincolnshire. PARTICIPANTS: 268 patients (mean age 48 years) with subacute and chronic neck pain, who were referred by their general practitioner and randomly assigned to a brief physiotherapy intervention (one to three sessions) using cognitive behaviour principles to encourage self management and return to normal function or usual physiotherapy, at the discretion of the physiotherapist concerned. MAIN OUTCOME MEASURES: The Northwick Park neck pain questionnaire (NPQ), a specific measure of functional disability resulting from neck pain. Also, the short form 36 (SF-36) questionnaire, a generic, health related, quality of life measure; and the Tampa scale for kinesophobia, a measure of fear and avoidance of movement. RESULTS: At 12 months, patients allocated to usual physiotherapy had a small but significant improvement in NPQ scores compared with patients in the brief intervention group (mean difference 1.99, 95% confidence interval 0.45 to 3.52; P = 0.01). Although the result shows a significant inferiority of the intervention, the confidence interval shows that the effect could be in the non-inferiority range for the brief intervention (below 1.2 points of NPQ score). Patients who preferred the brief intervention and received this treatment had similar outcomes to patients receiving usual physiotherapy. CONCLUSIONS: Usual physiotherapy may be only marginally better than a brief physiotherapy intervention for neck pain. Patients with a preference for the brief intervention may do at least as well with this approach. Additional training for the physiotherapists in cognitive behaviour techniques might improve this approach further.

Adolescent↗
PubMed2004

Fiber-optic-based absolute displacement sensors at 1500 nm by means of a variant of channeled spectrum signal recovery.

An absolute displacement-sensing system based on channeled spectrum processing capable of simultaneous interrogation of fiber Bragg gratings and fiber-optic interferometric sensors is presented in which the role of the optical spectrometer is performed by a scanning Fabry-Perot filter. We demonstrate a resolution of +/-50 nm with an estimated dynamic range of 1 part in 10(5).

Journal Article↗
PubMed2004

Gender differences in the effects of oppositional behavior on teacher ratings of ADHD symptoms.

H. Abikoff, M. Courtney, W. E. Pelham, and H. S. Koplewicz (1993) presented elementary school teachers with a videotape of a 4th-grade male child exhibiting behavior associated with either Attention Deficit Hyperactivity Disorder (ADHD) or Oppositional Defiant Disorder (ODD). Comparisons with ratings generated from a control tape (same child exhibiting unremarkable behavior) suggested that oppositional tendencies inflated teacher ratings of ADHD for boys. The term "halo effect" has been used in the literature to refer to the impact of one class of behavior on the perception of another. This study replicated this procedure using identical scripts with both male and female child models. Oppositional behavior was associated with higher teacher ratings of hyperactivity and inattentiveness. Portrayals of behavior associated with ADHD generated higher teacher ratings of oppositional conduct. This bidirectional effect differed in magnitude as a function of child gender. The boy actor exhibiting oppositional behavior received teacher ratings of hyperactivity and inattention that were roughly half of those elicited by his portrayal of ADHD itself. The girl actor portraying ADHD generated oppositional defiant ratings that were roughly two thirds of those elicited from her performance as a child with ODD. These teacher rating tendencies could contribute to higher diagnostic rates of ADHD among boys and ODD among girls. Available epidemiologic data indicate a much higher rate of ADHD among boys and prevalence differentials for ODD (girls initially lower) that disappear by adolescence. Future research will be required to determine the extent to which these teacher response sets generalize to other evaluators such as parents, physicians and mental health professionals.

Attention Deficit Disorder with Hyperactivity↗
PubMed2004

Quantification of root caries using optical coherence tomography and microradiography: a correlational study.

PURPOSE: The use of transverse microradiography (TMR) to quantify the amount of mineral lost during demineralization of tooth tissue has long been established. In the present study, the use of an en-face Optical Coherence Tomography (OCT) technology to detect and quantitatively monitor the mineral changes in root caries was investigated and correlated with TMR. MATERIALS AND METHODS: We used an OCT system, developed initially for retina imaging, and which can collect A-scans, B-scans (longitudinal images) and C-scans (en-face images) to quantitatively assess the development of root caries. The power to the sample was 250 microW, wavelength lambda = 850 nm and the optical source linewidth was 16 microm. RESULTS: Both the transversal and longitudinal images showed the caries lesion as volumes of reduced reflectivity. Quantitative analysis using the A-scan (reflectivity versus depth curve) showed that the tissue reflectivity decreased with increasing demineralization time. A linear correlation (r = 0.957) was observed between the mineral loss measured by TMR and the percentage reflectivity loss in demineralized tissue measured by OCT. CONCLUSION: We concluded that OCT could be used to detect incipient root caries, and that the reflectivity loss in root tissue during demineralization, measured by OCT, could be related to the amount of mineral lost during the demineralization.

Analysis of Variance↗
PubMed2003

Beta-globin locus control region HS2 and HS3 interact structurally and functionally.

The overall structure of the DNase I hypersensitive sites (HSs) that comprise the beta-globin locus control region (LCR) is highly conserved among mammals, implying that the HSs have conserved functions. However, it is not well understood how the LCR HSs, either individually or collectively, activate transcription. We analyzed the interactions of HS2, HS3 and HS4 with the human epsilon- and beta-globin genes in chromatinized episomes in fetal/embryonic K562 cells. Only HS2 activates transcription of the epsilon-globin gene, while all three HSs activate the beta-globin gene. HS3 stimulates the beta-globin gene constitutively, but HS2 and HS4 transactivation requires expression of the transcription factor EKLF, which is not present in K562 cells but is required for beta-globin expression in vivo. To begin addressing how the individual HSs may interact with one another in a complex, we linked the beta-globin gene to both the HS2 and HS3. HS2 and HS3 together resulted in synergistic stimulation of beta-globin transcription. Unexpectedly, mutated, inactive forms of HS2 impeded the activation of the beta-globin gene by HS3. Thus, there appear to be distinct interactions among the HSs and between the HSs and the globin genes. These preferential, non-exclusive interactions may underlie an important structural and functional cooperativity among the regulatory sequences of the beta-globin locus in vivo.

Binding Sites↗
PubMed2003

Characterization of dark liver pigment observed in rats after subchronic dosing of the beta3-adrenergic receptor agonist LY368842.

Dark liver pigmentation was observed in F344 rats in a subchronic toxicology study after daily dosing of LY368842 glycolate. In addition, green-colored urine was observed in some animals. To identify the source of the pigment and its potential for toxic consequences, the liver pigment was isolated from the liver tissue of rats. The resulting material was a dark brown to black powder that was insoluble in water, organic solvents, or a tissue-solubilizing agent. Several techniques, such as chemical degradation, HPLC, tandem mass spectrometry (LC/MS/MS), (1)H NMR, and matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS), were employed to characterize the dark liver pigment. Following oxidative degradation of the isolated pigment, degradation products related to LY368842 were identified or tentatively identified using LC/MS/MS. Two degradation products had the same protonated molecular ion at m/z 505, which is 30 amu higher than that of LY368842. The major m/z 505 product has been identified as the indole-2,3-dione oxidative product based on (1)H NMR data and confirmed by an authentic standard. In addition, monohydroxylated product was also identified in the degradation mixture. These degradation products were consistent with the metabolites found in vivo in rats. MALDI-MS analyses of liver and urine pigment both identified a product with a protonated molecular ion at m/z 977, suggesting formation of indirubin-like and indigo-like pigments. The results obtained suggest that the oxidative metabolites of LY368842 played a key role in the formation of the liver and urine pigments.

Adrenergic beta-3 Receptor Agonists↗
PubMed2003

Metabolism of capsaicin by cytochrome P450 produces novel dehydrogenated metabolites and decreases cytotoxicity to lung and liver cells.

Capsaicin is a common dietary constituent and a popular homeopathic treatment for chronic pain. Exposure to capsaicin has been shown to cause various dose-dependent acute physiological responses including the sensation of burning and pain, respiratory depression, and death. In this study, the P450-dependent metabolism of capsaicin by recombinant P450 enzymes and hepatic and lung microsomes from various species, including humans, was determined. A combination of LC/MS, LC/MS/MS, and LC/NMR was used to identify several metabolites of capsaicin that were generated by aromatic (M5 and M7) and alkyl hydroxylation (M2 and M3), O-demethylation (M6), N- (M9) and alkyl dehydrogenation (M1 and M4), and an additional ring oxygenation of M9 (M8). Dehydrogenation of capsaicin was a novel metabolic pathway and produced unique macrocyclic, diene, and imide metabolites. Metabolism of capsaicin by microsomes was inhibited by the nonselective P450 inhibitor 1-aminobenzotriazole (1-ABT). Metabolism was catalyzed by CYP1A1, 1A2, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, and 3A4. Addition of GSH (2 mM) to microsomal incubations stimulated the metabolism of capsaicin and trapped several reactive electrophilic intermediates as their GSH adducts. These results suggested that reactive intermediates, which inactivated certain P450 enzymes, were produced during catalytic turnover. Comparison of the rate and types of metabolites produced from capsaicin and its analogue, nonivamide, demonstrated similar pathways in the P450-dependent metabolism of these two capsaicinoids. However, production of the dehydrogenated (M4), macrocyclic (M1), and omega-1-hydroxylated (M3) metabolites was not observed for nonivamide. These differences may be reflective of the mechanism of formation of these metabolites of capsaicin. The role of metabolism in the cytotoxicity of capsaicin and nonivamide was also assessed in cultured lung and liver cells. Lung cells were markedly more sensitive to cytotoxicity by capsaicin and nonivamide. Cytotoxicity was enhanced 5 and 40% for both compounds by 1-ABT in BEAS-2B and HepG2, respectively. These data suggested that metabolism of capsaicinoids by P450 in cells represented a detoxification mechanism (in contrast to bioactivation).

Animals↗
PubMed2003

Correlation of quantitative light-induced fluorescence and optical coherence tomography applied for detection and quantification of early dental caries.

Fluorescence loss in enamel following demineralization has been correlated with the amount of mineral lost during the demineralization. The correlation between fluorescence loss measured by quantitative light-induced fluorescence (QLF) and the reflectivity loss measured by a versatile en face optical coherence tomography (OCT) system was investigated in a demineralization process to produce artificial dental caries. We used an OCT system that can collect A-scans (reflectivity versus depth), B-scans (longitudinal images), and C-scans (en face images). The power to the sample was 250 microW, the wavelength lambda = 850 nm, and the depth resolution in air 16 microm. A-scans, which show the profile of the reflectivity versus the depth of penetration into the tooth tissue, were used for quantitative analysis of the reflectivity loss. The results have shown that both the fluorescence radiance and reflectivity of the enamel decrease with increasing de- mineralization time. A linear correlation was observed between the percentage of fluorescence loss measured by QLF and the percentage of reflectivity loss measured by OCT. It was concluded that the decrease in reflectivity of the enamel during demineralization, measured by OCT, could be related to the amount of mineral lost during the de- mineralization process.

Algorithms↗
PubMed2002

A three-component coupling process based on vicarious nucleophilic substitution (VNS(AR))-alkylation reactions: an approach to indoprofen and derivatives.

The intermediate anion derived from the vicarious nucleophilic substitution (VNS) of hydrogen reacts with a series of alkyl halides to generate the corresponding alpha-alkylated conventional VNS product in a one-pot process. This one-pot VNS-alkylation reaction offers a convenient route to a range alpha-substituted nitrobenzyl phosphine oxides, sulfones, and esters via a three-component coupling reaction. Reactions of alpha-chloroethyl phenyl sulfone (14) and ethyl 2-chloropropionate (16) with nitrobenzene followed by subsequent addition of an alkylating agent give a series of sulfones and esters bearing an alpha-aryl quaternary center. The VNS-alkylation protocol has been applied to the synthesis of derivatives of Indoprofen from nitrobenzene using readily available inexpensive starting materials. Indoprofen itself was prepared using the conventional VNS reaction in four steps and 24% overall yield from nitrobenzene.

Alkylation↗
PubMedDate not supplied

Biosynthesis of drug glucuronides for use as authentic standards.

INTRODUCTION: Glucuronidation by the uridine diphosphate glucuronosyltransferases (UGTs) plays a pivotal role in the clearance mechanism of both xenobiotics and endobiotics. The detection of glucuronides at low micromolar concentrations is required to accurately model in vitro enzyme kinetics and in vivo pharmacokinetics. However, relatively few glucuronides are currently available as standards for developing liquid chromatography and mass spectroscopy (LC/MS) bioanalytical methods. METHODS: The glucuronidation capacity of hepatic microsomes prepared from rat (RLM), dog (DLM), monkey (MLM), and human (HLM) was examined for five xenobiotic substrates. In each case, glucuronide standards were produced using the enzyme source most efficient for the production of that specific glucuronide. RESULTS: Dog hepatic microsomes were used to produce glucuronides for anthraflavic acid (yield: 14 mg), buprenorphine (yield: 14 mg), and octylgallate (total yield: 13 mg), whereas propofol glucuronide (yield: 20 mg), and ethinylestradiol glucuronide (yield: 8 mg) were prepared using HLM. All glucuronides were characterized by LC/MS/MS and nuclear magnetic resonance (NMR) spectroscopy. DISCUSSION: The multimilligram quantities of glucuronide standards produced by this method have many applications throughout drug discovery and toxicology. In addition to allowing the quantification of glucuronide formation from in vitro and in vivo studies, the authentic standards produced could also be used to assess potential pharmacological or toxicological effects of metabolites.

Animals↗