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Biomedical subjects

Kevin Taylor

Publications and source records attributed to Kevin Taylor.

10 recordsLinked to original sources
PubMed2006

Aspirin reduces platelet aggregation during high-energy excimer laser.

BACKGROUND AND OBJECTIVES: Excimer laser is used clinically in arterial revascularization procedures. This study evaluated the efficacy of aspirin in reducing platelet aggregation during high-energy excimer lasing. STUDY DESIGN/MATERIALS AND METHODS: Platelet rich plasma (PRP) from seven rabbits was circulated in a dual organ chamber with aspirin added to one and the other was control. PRP was irradiated using an excimer laser (308 nm; 45 mJ/mm(2); 25 Hz; 5 minutes) via a 2.0 mm laser catheter. Platelet aggregation (particle volume) was measured by laser-light scattering. Morphology was evaluated by phase contrast and electron microscopy. RESULTS: Baseline platelet volume was 3.4 microm(3) for both control and aspirin groups. Following lasing, platelet volume peaked at 102.2 +/- 18.5 microm(3) for control compared to 43.1 +/- 49.2 microm(3) for aspirin-treated PRP (P < 0.0001). CONCLUSION: Aspirin reduces large platelet aggregates but not small aggregates by 58% during lasing of PRP.

Analysis of Variance↗
PubMed2005

Fetal testosterone and empathy.

BACKGROUND: In animals, fetal testosterone (fT) plays a central role in organizing the brain and in later social behavior. In humans, exposure to atypical levels of prenatal androgens may result in masculine behavior and ability patterns. Normal inter-individual variation in fT levels has also been correlated with later sex-typed behavior. METHODS: In the current study, 38 children (24 male, 14 female), whose fT was analyzed in amniotic fluid, were followed up at age 4. They were asked to describe cartoons with 2 moving triangles whose interactions with each other suggested social relationships and psychological motivations. RESULTS: Females used more mental and affective state terms to describe the cartoons than males. fT was not associated with the frequency of mental or affective state terms. Females also used more intentional propositions than males. fT was negatively correlated with the frequency of intentional propositions, taking sex differences into account. fT was also negatively correlated with the frequency of intentional propositions when males were examined separately. Males used more neutral propositions than females. fT was directly correlated with the frequency of neutral propositions, taking sex differences into account. This relationship was not seen when males and females were examined separately. CONCLUSIONS: These findings implicate fT in human social development. The relevance of our findings to the 'extreme male brain' theory of autism is also discussed.

Affect↗
PubMed2005

Gender-typed play and amniotic testosterone.

Sex differences in play are apparent in a number of mammalian species, including humans. Prenatal testosterone may contribute to these differences. The authors report the first attempt to correlate gender-typed play in a normative sample of humans with measurements of amniotic testosterone (aT). Testosterone was measured in the amniotic fluid of 53 children (31 boys and 22 girls). A strong sex difference was observed in aT and, at ages 4.75 to 5.8 years, on a modified version of the Child Game Participation Questionnaire. Hierarchical regression analyses on the entire group and within-sex correlations suggested that variations in aT did not contribute to individual differences in game participation as reported by the mother. A critique of explanations for this finding is presented.

Amniocentesis↗
PubMed2005

Foetal testosterone, social relationships, and restricted interests in children.

BACKGROUND: Sex-differences exist in some areas of human social behaviour. In animals, foetal testosterone (fT) plays a central role in organising the brain and in later social behaviour. fT has also been implicated in language development, eye-contact, and spatial ability in humans. METHODS: Fifty-eight children (35 male and 23 female), whose fT was analysed in amniotic fluid, were followed up at age 4. Their mothers completed the Children's Communication Checklist, a questionnaire assessing language, quality of social relationships and restricted interests. RESULTS: fT was negatively correlated to quality of social relationships, taking sex-differences into account. fT was also positively correlated with restricted interests in boys. CONCLUSIONS: These findings implicate fT in both social development and attentional focus. They may also have implications for understanding the sex ratio in autism.

Autistic Disorder↗
PubMed2004

Novel use of a high-energy excimer laser catheter for calcified and complex coronary artery lesions.

This study was designed to evaluate safety and effectiveness of the 0.9 mm excimer laser coronary catheter with increased laser parameters. We report a prospective trial of 100 calcified and/or balloon-resistant lesions where a new 0.9 mm excimer laser catheter was used at standard or higher energy level to facilitate angioplasty. Standard in-hospital clinical and angiographic parameters were collected and measured. Laser technical success was obtained in 87 lesions (92%), procedural success was reached in 88 lesions (93%), and clinical success in 82 lesions (86%). Increased laser parameters were used for 29 resistant lesions. This new 0.9 mm excimer laser coronary catheter using higher energy parameters seems to be safe and effective for management of calcified and nondilatable lesions.

Aged↗
PubMed2004

Role of Sp1, C/EBP alpha, HNF3, and PXR in the basal- and xenobiotic-mediated regulation of the CYP3A4 gene.

Cytochrome P450 3A4 (CYP3A4) is the major cytochrome P450 present in adult human liver and is involved in the metabolism of over 50% of therapeutic compounds currently in use. Since expression levels of CYP3A4 are regulated by many of these compounds, this raises the potential for drug-drug interactions and subsequent altered efficacy or toxicity of the individual compounds at the dose prescribed. Hence, understanding the molecular mechanisms of CYP3A4 regulation is of key importance in predicting and understanding such interactions. To examine this we have used DNase I footprinting and bioinformatic analysis to identify putative transcription factor binding sites within the 250 base pairs of promoter proximal to the transcription start site. We identified several protected fragments within this region that corresponded to putative binding sites for Sp1, AP2, CCAAT/enhancer binding protein (C/EBPalpha), and hepatic nuclear factor-3 (HNF3), as well as confirming previously identified C/EBPalpha, pregnane X receptor (PXR), and HNF3 binding sites. Sequential site-directed mutagenesis of C/EBPalpha, Sp1, HNF3, and PXR binding sites was next used to examine the role of these sites in basal CYP3A4 expression. Disruption of the C/EBPalpha, HNF3, and PXR binding sites all affected basal expression. Finally, the role of these sites was examined in activation of CYP3A4 expression by rifampicin, metyrapone, clotrimazole, and phenobarbital. Disruption of any of these sites either led to an altered pattern of activation by the xenobiotic, as altered maximal activation, or altered the EC(50) value of activation. Such effects were xenobiotic-specific, with each disrupted site playing a role in the activation of some of the xenobiotics.

Base Sequence↗
PubMed2002

Expression and characterization of recombinant vitamin K-dependent gamma-glutamyl carboxylase from an invertebrate, Conus textile.

The marine snail Conus is the sole invertebrate wherein both the vitamin K-dependent carboxylase and its product, gamma-carboxyglutamic acid, have been identified. To examine its biosynthesis of gamma-carboxyglutamic acid, we studied the carboxylase from Conus venom ducts. The carboxylase cDNA from Conus textile has an ORF that encodes a 811-amino-acid protein which exhibits sequence similarity to the vertebrate carboxylases, with 41% identity and approximately 60% sequence similarity to the bovine carboxylase. Expression of this cDNA in COS cells or insect cells yielded vitamin K-dependent carboxylase activity and vitamin K-dependent epoxidase activity. The recombinant carboxylase has a molecular mass of approximately 130 kDa. The recombinant Conus carboxylase carboxylated Phe-Leu-Glu-Glu-Leu and the 28-residue peptides based on residues -18 to +10 of human proprothrombin and proFactor IX with Km values of 420 micro m, 1.7 micro m and 6 micro m, respectively; the Km for vitamin K is 52 micro m. The Km values for peptides based on the sequence of the conotoxin epsilon-TxIX and two precursor analogs containing 12 or 29 amino acids of the propeptide region are 565 micro m, 75 micro m and 74 micro m, respectively. The recombinant Conus carboxylase, in the absence of endogenous substrates, is stimulated up to fivefold by vertebrate propeptides but not by Conus propeptides. These results suggest two propeptide-binding sites in the carboxylase, one that binds the Conus and vertebrate propeptides and is required for substrate binding, and the other that binds only the vertebrate propeptide and is required for enzyme stimulation. The marked functional and structural similarities between the Conus carboxylase and vertebrate vitamin K-dependent gamma-carboxylases argue for conservation of a vitamin K-dependent carboxylase across animal species and the importance of gamma-carboxyglutamic acid synthesis in diverse biological systems.

1-Carboxyglutamic Acid↗