The effects of age and gender on the single dose pharmacokinetics of avitriptan administered to healthy volunteers

The effects of age and gender on the single dose pharmacokinetics of avitriptan and its three metabolites were assessed in 15 young men, 15 young women, 15 elderly men and 15 elderly women. Avitriptan was administered as a 150-mg capsule after a 10-hour fast and serial plasma and urine samples were collected up to 36 hours after the dose. Plasma samples were analyzed for avitriptan and its metabolites, N-desmethyl avitriptan (ND048), O-desmethyl avitriptan (OD048), and methoxypyrimidinyl piperazine (MPP). Urine samples were analyzed for only avitriptan and MPP. Avitriptan was well tolerated in all four groups. The drug was rapidly absorbed with a median time to maximum plasma concentration (tmax) between 0.5 and 1.5 hours. No significant gender-related differences were found in the maximum plasma concentration (Cmax) and area under the concentration-time curve extrapolated to infinity (AUC0-infinity) of avitriptan. Renal clearance of avitriptan was significantly smaller in young women compared with young men, but this is clinically not relevant because only 2% to 3% of the total dose is excreted unchanged. Compared with the young volunteers, mean Cmax was approximately 50% higher in the elderly but there was no difference in the AUC0-infinity between the 2 age groups. Plasma concentrations of ND048, OD048, and MPP were each 50 to 100 fold lower than those of avitriptan. Hence some age- and gender-related differences found in the pharmacokinetics of avitriptan metabolites are probably not relevant in the assessment of overall safety and efficacy of avitriptan. Based on the pharmacokinetics and tolerability, no age or gender-related dose adjustment is necessary for avitriptan.     

Inhibition of N-methyl-D-aspartate glutamate receptor subunit expression by antisense oligonucleotides reveals their role in striatal motor regulation

N-methyl-D-aspartate (NMDA) glutamate receptors have an established role in the regulation of motor behavior by the basal ganglia. Recent studies have revealed that NMDA receptors are heteromeric assemblies of structurally related subunits from two families: NMDAR1, which is required for channel activity, and NMDAR2A-D, which modulate the properties of the channels. In the rat, the NMDA receptor subunits exhibit anatomically restricted patterns of expression, so that each component of the basal ganglia has a distinct NMDA receptor subunit mRNA phenotype. We have used in vivo intrastriatal injection of synthetic antisense oligodeoxynucleotides (ODNs) to examine the roles of particular NMDA receptor subunits in the regulation of motor behavior in rats. Injection of 15 nmol of a 20-mer ODN targeted to the NMDAR1 subunit induced spontaneous ipsilateral rotation. Smaller doses of NMDAR1 antisense ODN did not lead to spontaneous rotation, but prominent ipsilateral rotation was observed after systemic administration of D-amphetamine. An antisense ODN to NMDAR2A was also effective in eliciting amphetamine-inducible rotation, although the magnitude of the effect was less than that seen with NMDAR1, whereas ODNs targeted to NMDAR2B, NMDAR2C and an NMDAR1 sense strand ODN had no effect on behavior. In situ hybridization demonstrated that injection of the NMDAR1, NMDAR2A or NMDAR2B antisense ODNs produced specific reductions in target mRNA signal intensity in the injected striatum. After NMDAR1 antisense ODN injection, striatal binding of 3H-glutamate target mRNA signal intensity in the injected striatum. After NMDAR1 antisense ODN injection, striatal binding of 3H-glutamate to NMDA sites was not altered, although strychnine-insensitive 3H-glycine binding sites exhibited a small but significant reduction. These observations suggest that NMDA receptor complexes containing NMDAR1 and, to a lesser extent, NMDAR2A subunits play particularly important roles in the regulation of motor behavior by neostriatal neurons.     

Cytochrome P450 3A4 activity in premenopausal and postmenopausal women, based on 6-beta-hydroxycortisol:cortisol ratios

STUDY OBJECTIVE: To characterize cytochrome P450 (CYP) 3A4 activity in premenopausal and postmenopausal women by evaluating the urinary 6-beta-hydroxycortisol:cortisol ratio. DESIGN: Prospective study SUBJECTS: Thirteen premenopausal and 13 postmenopausal women who were healthy and not receiving drugs known to affect CYP3A4 activity INTERVENTIONS: Beginning on day 2 of menses, premenopausal women collected first morning urine samples every other day for a complete menstrual cycle. Postmenopausal women collected first morning urine every other day for 28 days. MEASUREMENTS AND MAIN RESULTS: Mean weekly 6-beta-hydroxycortisol:cortisol ratios did not differ during the phase (week) of the menstrual cycle. Daily ratios did not differ in postmenopausal women. No difference between premenopausal and postmenopausal women was found on comparing overall median ratios. CONCLUSION: Cytochrome P450 3A4 activity as measured by 6-beta-hydroxy cortisol:cortisol ratio did not differ by week of menstrual cycle, suggesting no menstrual cycle-related changes. Menopause does not appear to be associated with differences in CYP3A4 activity, compared with premenopause.     

Modeling study of the effects of overlapping Ca2+ microdomains on neurotransmitter release

Although single-channel Ca2+ microdomains are capable of gating neurotransmitter release in some instances, it is likely that in many cases the microdomains from several open channels overlap to activate vesicle fusion. We describe a mathematical model in which transmitter release is gated by single or overlapping Ca2+ microdomains produced by the opening of nearby Ca2+ channels. This model accounts for the presence of a mobile Ca2+ buffer, provided either that the buffer is unsaturable or that it is saturated near an open channel with Ca2+ binding kinetics that are rapid relative to Ca2+ diffusion. We show that the release time course is unaffected by the location of the channels (at least for distances up to 50 nm), but paired-pulse facilitation is greater when the channels are farther from the release sites. We then develop formulas relating the fractional release following selective or random channel blockage to the cooperative relationship between release and the presynaptic Ca2+ current. These formulas are used with the transmitter release model to study the dependence of this form of cooperativity, which we call Ca2+ current cooperativity, on mobile buffers and on the local geometry of Ca2+ channels. We find that Ca2+ current cooperativity increases with the number of channels per release site, but is considerably less than the number of channels, the theoretical upper bound. In the presence of a saturating mobile buffer the Ca2+ current cooperativity is greater, and it increases more rapidly with the number of channels. Finally, Ca2+ current cooperativity is an increasing function of channel distance, particularly in the presence of saturating mobile buffer.     

Detailed active site configuration of a new crystal form of methanol dehydrogenase from Methylophilus W3A1 at 1.9 A resolution

The three-dimensional structure of a new crystal form of methanol dehydrogenase from Methylophilus W3A1 has been obtained in the presence of substrate using data recorded at a synchrotron. The structure of this approximately 140 kDa heterotetramer, refined at 1. 9 A resolution, reveals the detailed configuration of its redox cofactor, pyrroloquinoline quinone (PQQ). C4, one of the oxygen-bearing atoms of this orthoquinone is in a planar configuration while C5, which bears the other quinone oxygen, is tetrahedral, suggesting that the PQQ is in the semiquinone redox state. The substrate binding site has been identified close to PQQ and to the side chain of Asp297, the putative active site base. The proximity of the hydroxyl of methanol to C5 of PQQ compared to the greater separation of the substrate methyl group from C5 supports the addition-elimination reaction mechanism involving a hemiketal intermediate.     

A longitudinal study of the relationships between haemostatic, lipid, and oestradiol changes during normal human pregnancy

BACKGROUND: Chronic leukemia is a disease characterized by the malignant proliferation of immunologically incompetent lymphocytes. The knowledge of open heart surgery in patients with this disorder is limited. METHODS: Twelve patients with chronic lymphocytic leukemia underwent open heart surgery (nine coronary artery bypass grafting (CABG), two aortic valve replacement (AVR), one CABG and AVR) from September 1991 to September 1996. There were nine males and three females with a mean age of 68 years (41-81 years). Staging was assigned according to the Rai Classification. There were seven Stage 0, two Stage I, zero Stage II, one Stage III and two Stage IV patients. Cardiopulmonary bypass (CPB) was performed using standard techniques of cannulation, moderate hypothermia and antegrade/retrograde cardioplegia. RESULTS: Hospital mortality occurred in two (17%) patients. Both patients died of sepsis. Hospital morbidity occurred in seven (58%) patients. The most common complications were infections. Five patients were found to have other malignancies (basal cell, laryngeal, prostate, bladder and breast cancers). Transfusion of blood products was required in eight (67%) patients. The average length of stay was 15 days (7-50 days). Follow-up was complete. Late mortality occurred in four patients at a mean of 7 months (1-18 months). All deaths were non-cardiac related (ruptured AAA, kidney failure, respiratory failure and sepsis). Six patients remain alive at a mean of 25 months (1-48 months). CONCLUSION: Hospital mortality and morbidity in patients with chronic lymphocytic leukemia undergoing open heart surgery are high. Infection is the leading cause of hospital death, as well as the most common complication. The majority of patients receive blood products during the course of their hospitalization. Late mortality is high and non-cardiac related. Based on these findings, a re-definition of the aims, goals and expectations of open heart surgery in patients with chronic leukemia is necessary. Suggestions in management are presented.     

Upregulation of 5''-AMP-activated protein kinase is responsible for the increase in myocardial fatty acid oxidation rates following birth in the newborn rabbit

Eighteen patients with intracranial skull base tumours diagnosed at CT or MR as neuromas or meningiomas were studied with positron emission tomography (PET) using L-(methyl-11C) methionine. Compared with normal cerebellar tissue, the uptake of methionine in the tumours increased more rapidly and reached a higher level, and showed a slow decline after a peak occurring about 5 min after the injection. All the meningiomas exhibited considerably higher accumulation of the tracer compared with the surrounding cerebellar tissue, which made the tumour easy to identify and to demarcate from the surrounding cerebellar tissue, which made the tumour easy to identify and to demarcate from the surrounding structures (tumour to cerebellum ratios 2.62-5.37, mean 3.63). The uptake was homogeneous in all meningiomas, which were all of the syncytial type. The neuromas showed lower contrast against the cerebellum (tumour to cerebellum ratios 1.1-1.87, mean 1.48). Some neuromas displayed an irregular pattern with regions of decreased tracer uptake corresponding to small cystic areas within the neuroma. There was no overlap in methionine uptake between the two tumour groups. The results indicate that PET-methionine may contribute to the evaluation, treatment planning and follow-up of patients with skull base meningiomas and neuromas.